WorldWideScience

Sample records for fiberreinforced composite posts

  1. Effects of endodontic post surface treatment, dentin conditioning, and artificial aging on the retention of glass fiber-reinforced composite resin posts.

    Science.gov (United States)

    Albashaireh, Zakereyya S; Ghazal, Muhamad; Kern, Matthias

    2010-01-01

    Several post surface treatments with or without the application of a bonding agent have been recommended to improve the bond strength of resin cements to posts. A regimen that produces the maximum bond strength of glass fiber-reinforced composite resin posts has not been verified. The purpose of this study was to evaluate the influence of post surface conditioning methods and artificial aging on the retention and microleakage of adhesively luted glass fiber-reinforced composite resin posts. Seventy-two endodontically treated single-rooted teeth were prepared for glass fiber-reinforced composite resin posts. The posts were submitted to 3 different surface treatments (n=24), including no treatment, etching with phosphoric acid, and airborne-particle abrasion. Subgroups of the posts (n=8) were then allocated for 3 different experimental conditions: no artificial aging, no bonding agent; no artificial aging, bonding agent; or artificial aging, bonding agent. The posts were luted with resin cement (Calibra). Post retention was measured in tension at a crosshead speed of 2 mm/min. The posts assigned for microleakage investigation were placed in fuchsin dye for 72 hours. The dislodged posts and the post spaces were examined microscopically to evaluate the mode of failure and explore the microleakage. Data were analyzed by 2-way ANOVA followed by Tukey HSD test (alpha=.05). The mean (SD) retention values for test groups ranged from 269 (63.8) to 349 (52.2) N. The retention values of the airborne-particle-abrasion group were significantly higher than those of the acidic-treatment and no-treatment groups. The application of bonding agent on the post surface produced no significant influence on retention. The mean retention values after artificial aging were significantly higher than without artificial aging. Microscopic evaluation demonstrated that the failure mode was primarily mixed. Treating the surface of the posts with phosphoric acid for 15 seconds before cementation

  2. Microhardness of dual-polymerizing resin cements and foundation composite resins for luting fiber-reinforced posts.

    Science.gov (United States)

    Yoshida, Keiichi; Meng, Xiangfeng

    2014-06-01

    The optimal luting material for fiber-reinforced posts to ensure the longevity of foundation restorations remains undetermined. The purpose of this study was to evaluate the suitability of 3 dual-polymerizing resin cements and 2 dual-polymerizing foundation composite resins for luting fiber-reinforced posts by assessing their Knoop hardness number. Five specimens of dual-polymerizing resin cements (SA Cement Automix, G-Cem LincAce, and Panavia F2.0) and 5 specimens of dual-polymerizing foundation composite resins (Clearfil DC Core Plus and Unifil Core EM) were polymerized from the top by irradiation for 40 seconds. Knoop hardness numbers were measured at depths of 0.5, 2.0, 4.0, 6.0, 8.0, and 10.0 mm at 0.5 hours and 7 days after irradiation. Data were statistically analyzed by repeated measures ANOVA, 1-way ANOVA, and the Tukey compromise post hoc test (α=.05). At both times after irradiation, the 5 resins materials showed the highest Knoop hardness numbers at the 0.5-mm depth. At 7 days after irradiation, the Knoop hardness numbers of the resin materials did not differ significantly between the 8.0-mm and 10.0-mm depths (P>.05). For all materials, the Knoop hardness numbers at 7 days after irradiation were significantly higher than those at 0.5 hours after irradiation at all depths (Presin materials were found to decrease in the following order: DC Core Plus, Unifil Core EM, Panavia F2.0, SA Cement Automix, and G-Cem LincAce (Pcomposite resins were higher than those of the 3 dual-polymerizing resin cements, notable differences were seen among the 5 materials at all depths and at both times after irradiation. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  3. Effect of ultraviolet light irradiation period on bond strengths between fiber-reinforced composite post and core build-up composite resin.

    Science.gov (United States)

    Asakawa, Yuya; Takahashi, Hidekazu; Iwasaki, Naohiko; Kobayashi, Masahiro

    2014-01-01

    The aim of the present study was to characterize the effects of the ultraviolet light (UV) irradiation period on the bond strength of fiber-reinforced composite (FRC) posts to core build-up resin. Three types of FRC posts were prepared using polymethyl methacrylate, urethane dimethacrylate, and epoxy resin. The surfaces of these posts were treated using UV irradiation at a distance of 15 mm for 0 to 600 s. The pull-out bond strength was measured and analyzed with the Dunnett's comparison test (α=0.05). The bond strengths of the post surfaces without irradiation were 6.9 to 7.4 MPa; those after irradiation were 4.2 to 26.1 MPa. The bond strengths significantly increased after 15 to 120-s irradiation. UV irradiation on the FRC posts improved the bond strengths between the FRC posts and core build-up resin regardless of the type of matrix resin.

  4. Micromechanical failure in fiber-reinforced composites

    DEFF Research Database (Denmark)

    Ashouri Vajari, Danial

    Micromechanical failure mechanisms occurring in unidirectional fiber-reinforced composites are studied by means of the finite element method as well as experimental testing. This study highlights the effect of micro-scale features such as fiber/matrix interfacial debonding, matrix cracking...... and microvoids on the microscopic and macroscopic mechanical response of composite materials. To this end, first a numerical study is carried out to explore ways to stabilize interfacial crack growth under dominant Mode-I fracture using the cohesive zone model. Consequently, this study suggests a method...... composites. In the first approach, the J2 plasticity model is implemented to model the elasto-plastic behavior of the matrix while in the second strategy the modified Drucker-Prager plasticity model is utilized to account for brittle-like and pressure dependent behavior of an epoxy matrix. In addition...

  5. Effects of various etching protocols on the flexural properties and surface topography of fiber-reinforced composite dental posts.

    Science.gov (United States)

    Aksornmuang, Juthatip; Chuenarrom, Chanya; Chittithaworn, Natjira

    2017-09-26

    The purpose of this study was to evaluate the flexural properties and surface topography of fiber posts surface-treated with various etching protocols. Seventy each of three types of fiber posts: RelyX Fiber Post, Tenax Fiber Trans, and D.T. Light-Post Illusion X-Ro, were randomly divided into 7 groups: no surface treatment, surface treated with hydrofluoric acid (HF) 4.5% for 60 s, HF 4.5% for 120 s, HF 9.6% for 15 s, HF 9.6% for 60 s, HF 9.6% for 120 s, and treated with H 2 O 2 24% for 10 min. The specimens were then subjected to a three-point bending test. Surface topographies of the posts were observed using a SEM. The results indicate that fiber post surface pretreatments had no adverse effects on the flexural properties. However, the fiber posts treated with high HF concentrations or long etching times seemed to have more surface irregularities.

  6. Fiber-reinforced Composite for Chairside Replacement of Anterior ...

    African Journals Online (AJOL)

    Fiber-reinforced Composite for Chairside Replacement of Anterior Teeth: A Case Report. ... investigation will be required to provide additional information on the survival of directly-bonded anterior fixed prosthesis made with FRC systems.

  7. Radiation processing for carbon fiber-reinforced polytetrafluoroethylene composite materials

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Udagawa, Akira; Morita, Yousuke

    2001-01-01

    The present work is an attempt to evaluate the performance of the fiber composites with crosslinked polytetrafluoroethylene (PTFE) as a polymer matrix by radiation. The uni-directional carbon fiber-reinforced composites were fabricated with PTFE fine powder impregnation method and then crosslinked by electron beams irradiation under selective conditions. The carbon fiber-reinforced crosslinked PTFE composites show good mechanical properties compared with crosslinked PTFE. The radiation resistance of crosslinked PTFE composites is improved more than that of crosslinked resin without fiber. (author)

  8. Fiber-reinforced Composite Resin Prosthesis to Restore Missing ...

    African Journals Online (AJOL)

    A fiber-reinforced composite inlay-onlay FPD was used for a single posterior tooth replacement in a patient refusing implant for psychological reasons. The FRC-FPD was made of pre-impregnated E-glass fibers (everStick, StickTeck, Turku, Finland) embedded in a resin matrix (Stick Resin, StickTeck, Turku, Finland).

  9. Elastic constants and internal friction of fiber-reinforced composites

    International Nuclear Information System (INIS)

    Ledbetter, H.M.

    1982-01-01

    We review recent experimental studies at NBS on the anisotropic elastic constants and internal friction of fiber-reinforced composites. Materials that were studied include: boron-aluminum, boron-epoxy, graphite-epoxy, glass-epoxy, and aramid-epoxy. In all cases, elastic-constant direction dependence could be described by relationships developed for single crystals of homogeneous materials. Elastic stiffness and internal friction were found to vary inversely

  10. Fabrication of fiber-reinforced composites by chemical vapor infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Besmann, T.M.; Stinton, D.P. [Oak Ridge National Lab., TN (United States); Matlin, W.M.; Liaw, P.K. [Univ. of Tennessee, Knoxville, TN (United States)

    1996-08-01

    Processing equipment for the infiltration of fiber-reinforced composite tubes is being designed that incorporates improvements over the equipment used to infiltrate disks. A computer-controlled machine-man interface is being developed to allow for total control of all processing variables. Additionally, several improvements are being made to the furnace that will reduce the complexity and cost of the process. These improvements include the incorporation of free standing preforms, cast mandrels, and simpler graphite heating elements.

  11. Fiber-reinforced composites materials, manufacturing, and design

    CERN Document Server

    Mallick, P K

    2007-01-01

    The newly expanded and revised edition of Fiber-Reinforced Composites: Materials, Manufacturing, and Design presents the most up-to-date resource available on state-of-the-art composite materials. This book is unique in that it not only offers a current analysis of mechanics and properties, but also examines the latest advances in test methods, applications, manufacturing processes, and design aspects involving composites. This third edition presents thorough coverage of newly developed materials including nanocomposites. It also adds more emphasis on underlying theories, practical methods, and problem-solving skills employed in real-world applications of composite materials. Each chapter contains new examples drawn from diverse applications and additional problems to reinforce the practical relevance of key concepts. New in The Third Edition: Contains new sections on material substitution, cost analysis, nano- and natural fibers, fiber architecture, and carbon-carbon composites Provides a new chapter on poly...

  12. Elastic properties of rigid fiber-reinforced composites

    Science.gov (United States)

    Chen, J.; Thorpe, M. F.; Davis, L. C.

    1995-05-01

    We study the elastic properties of rigid fiber-reinforced composites with perfect bonding between fibers and matrix, and also with sliding boundary conditions. In the dilute region, there exists an exact analytical solution. Around the rigidity threshold we find the elastic moduli and Poisson's ratio by decomposing the deformation into a compression mode and a rotation mode. For perfect bonding, both modes are important, whereas only the compression mode is operative for sliding boundary conditions. We employ the digital-image-based method and a finite element analysis to perform computer simulations which confirm our analytical predictions.

  13. Chairside fabricated fiber-reinforced composite fixed partial denture

    Directory of Open Access Journals (Sweden)

    Sufyan Garoushi

    2007-01-01

    Full Text Available The advances in the materials and techniques for adhesive dentistry have allowed the development of non-invasive or minimally invasive approaches for replacing a missing tooth in those clinical situations when conservation of adjacent teeth is needed. Good mechanical and cosmetic/aesthetic properties of fiber-reinforced composite (FRC, with good bonding properties with composite resin cement and veneering composite are needed in FRC devices. Some recent studies have shown that adhesives of composite resins and luting cements allow diffusion of the adhesives to the FRC framework of the bridges. By this so-called interdiffusion bonding is formed [1]. FRC bridges can be made in dental laboratories or chairside. This article describes a clinical case of chairside (directly made FRC Bridge, which was used according to the principles of minimal invasive approach. Treatment was performed by Professor Vallittu from the University of Turku, Finland.

  14. Poisson's ratio of fiber-reinforced composites

    Science.gov (United States)

    Christiansson, Henrik; Helsing, Johan

    1996-05-01

    Poisson's ratio flow diagrams, that is, the Poisson's ratio versus the fiber fraction, are obtained numerically for hexagonal arrays of elastic circular fibers in an elastic matrix. High numerical accuracy is achieved through the use of an interface integral equation method. Questions concerning fixed point theorems and the validity of existing asymptotic relations are investigated and partially resolved. Our findings for the transverse effective Poisson's ratio, together with earlier results for random systems by other authors, make it possible to formulate a general statement for Poisson's ratio flow diagrams: For composites with circular fibers and where the phase Poisson's ratios are equal to 1/3, the system with the lowest stiffness ratio has the highest Poisson's ratio. For other choices of the elastic moduli for the phases, no simple statement can be made.

  15. Natural fiber-reinforced polymer composites

    International Nuclear Information System (INIS)

    Taj, S.; Khan, S.; Munawar, M.A.

    2007-01-01

    Natural fibers have been used to reinforce materials for over 3,000 years. More recently they have been employed in combination with plastics. Many types of natural fi fibers have been investigated for use in plastics including Flax, hemp, jute, straw, wood fiber, rice husks, wheat, barley, oats, rye, cane (sugar and bamboo), grass reeds, kenaf, ramie, oil palm empty fruit bunch, sisal, coir, water hyacinth, pennywort, kapok, paper-mulberry, raphia, banana fiber, pineapple leaf fiber and papyrus. Natural fibers have the advantage that they are renewable resources and have marketing appeal. The Asian markets have been using natural fibers for many years e.g., jute is a common reinforcement in India. Natural fibers are increasingly used in automotive and packaging materials. Pakistan is an agricultural country and it is the main stay of Pakistan's economy. Thousands of tons of different crops are produced but most of their wastes do not have any useful utilization. Agricultural wastes include wheat husk, rice husk, and their straw, hemp fiber and shells of various dry fruits. These agricultural wastes can be used to prepare fiber reinforced polymer composites for commercial use. This report examines the different types of fibers available and the current status of research. Many references to the latest work on properties, processing and application have been cited in this review. (author)

  16. Improvement of the piezoelectric properties of glass fiber-reinforced epoxy composites by poling treatment

    International Nuclear Information System (INIS)

    Oh, S M; Hwang, H Y

    2013-01-01

    Recently, a new non-destructive method has been proposed for damage monitoring of glass fiber-reinforced polymer composite materials using the piezoelectric characteristics of a polymeric matrix. Several studies of the piezoelectric properties of unidirectional glass fiber epoxy composites and damage monitoring of double-cantilever beams have supported the claim that the piezoelectric method is feasible and powerful enough to monitor the damage of glass fiber epoxy composites. Generally, conventional piezoelectric materials have higher piezoelectric characteristics through poling treatment. In this work, we investigated the change of the piezoelectric properties of glass fiber-reinforced epoxy composites before and after poling treatment. The piezoelectric constants (d 33 ) of glass fiber-reinforced epoxy composites increased by more than 400%. Also, x-ray diffraction tests revealed that poling treatment changed the degree of crystallinity of the epoxy matrix, and this led to the improvement of the piezoelectric characteristics of glass fiber-reinforced epoxy composites. (paper)

  17. Effect of surface treatments on the flexural properties and adhesion of glass fiber-reinforced composite post to self-adhesive luting agent and radicular dentin.

    Science.gov (United States)

    Elnaghy, Amr M; Elsaka, Shaymaa E

    2016-01-01

    This study evaluated the effect of different surface treatments on the flexural properties and adhesion of glass fiber post to self-adhesive luting agent and radicular dentin. Seventy-five single-rooted human teeth were prepared to receive a glass fiber post (Reblida). The posts were divided into five groups according to the surface treatment: Gr C (control; no treatment), Gr S (silanization for 60 s), Gr AP (airborne-particle abrasion), Gr HF (etching with 9 % hydrofluoric acid for 1 min), and Gr M10 (etching with CH2Cl2 for 10 min). Dual-cure self-adhesive luting agent (Rely X Unicem) was applied to each group for testing the adhesion using micropush-out test. Failure types were examined with stereomicroscope and surface morphology of the posts was characterized using a scanning electron microscopy (SEM). Flexural properties of posts were assessed using a three-point bending test. Data were analyzed using ANOVA and Tukey's HSD test. Statistical significance was set at the 0.05 probability level. Groups treated with M10 showed significantly higher bond strength than those obtained with other surface treatments (P C > S > AP > HF. Most failure modes were adhesive type of failures between dentin and luting agent (48.2%). SEM analysis revealed that the fiber post surfaces were modified after surface treatments. The surface treatments did not compromise the flexural properties of fiber posts. Application of M10 to the fiber post surfaces enhanced the adhesion to self-adhesive luting agent and radicular dentin.

  18. Hybrid Fiber Layup and Fiber-Reinforced Polymeric Composites Produced Therefrom

    Science.gov (United States)

    Barnell, Thomas J. (Inventor); Garrigan, Sean P. (Inventor); Rauscher, Michael D. (Inventor); Dietsch, Benjamin A. (Inventor); Cupp, Gary N. (Inventor)

    2018-01-01

    Embodiments of a hybrid fiber layup used to form a fiber-reinforced polymeric composite, and a fiber-reinforced polymeric composite produced therefrom are disclosed. The hybrid fiber layup comprises one or more dry fiber strips and one or more prepreg fiber strips arranged side by side within each layer, wherein the prepreg fiber strips comprise fiber material impregnated with polymer resin and the dry fiber strips comprise fiber material without impregnated polymer resin.

  19. Fabrication of fiber-reinforced composites by chemical vapor infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Besmann, T.M.; McLaughlin, J.C. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Probst, K.J.; Anderson, T.J. [Univ. of Florida, Gainesville, FL (United States). Dept. of Chemical Engineering; Starr, T.L. [Georgia Inst. of Tech., Atlanta, GA (United States). Dept. of Materials Science and Engineering

    1997-12-01

    Silicon carbide-based heat exchanger tubes are of interest to energy production and conversion systems due to their excellent high temperature properties. Fiber-reinforced SiC is of particular importance for these applications since it is substantially tougher than monolithic SiC, and therefore more damage and thermal shock tolerant. This paper reviews a program to develop a scaled-up system for the chemical vapor infiltration of tubular shapes of fiber-reinforced SiC. The efforts include producing a unique furnace design, extensive process and system modeling, and experimental efforts to demonstrate tube fabrication.

  20. On Healable Polymers and Fiber-Reinforced Composites

    Science.gov (United States)

    Nielsen, Christian Eric

    Polymeric materials capable of healing damage would be valuable in structural applications where access for repair is limited. Approaches to creating such materials are reviewed, with the present work focusing on polymers with thermally reversible covalent cross-links. These special cross-links are Diels-Alder (DA) adducts, which can be separated and re-formed, enabling healing of mechanical damage at the molecular level. Several DA-based polymers, including 2MEP4FS, are mechanically and thermally characterized. The polymerization reaction of 2MEP4FS is modeled and the number of established DA adducts is associated with the glass transition temperature of the polymer. The models are applied to concentric cylinder rotational measurements of 2MEP4FS prepolymer at room and elevated temperatures to describe the viscosity as a function of time, temperature, and conversion. Mechanical damage including cracks and scratches are imparted in cured polymer samples and subsequently healed. Damage due to high temperature thermal degradation is observed to not be reversible. The ability to repair damage without flowing polymer chains makes DA-based healable polymers particularly well-suited for crack healing. The double cleavage drilled compression (DCDC) fracture test is investigated as a useful method of creating and incrementally growing cracks in a sample. The effect of sample geometry on the fracture behavior is experimentally and computationally studied. Computational and empirical models are developed to estimate critical stress intensity factors from DCDC results. Glass and carbon fiber-reinforced composites are fabricated with 2MEP4FS as the matrix material. A prepreg process is developed that uses temperature to control the polymerization rate of the monomers and produce homogeneous prepolymer for integration with a layer of unidirectional fiber. Multiple prepreg layers are laminated to form multi-layered cross-ply healable composites, which are characterized in

  1. Effects of moisture on glass fiber-reinforced polymer composites

    DEFF Research Database (Denmark)

    Alzamora Guzman, Vladimir Joel; Brøndsted, Povl

    2015-01-01

    performance of wind turbine blades over their lifetime. Here, environmental moisture conditions were simulated by immersing glass fiber-reinforced polymer specimens in salt water for a period of up to 8 years. The mechanical properties of specimens were analyzed before and after immersion to evaluate...

  2. Fracture Resistance of Endodontically Treated Teeth Restored with 2 Different Fiber-reinforced Composite and 2 Conventional Composite Resin Core Buildup Materials: An In Vitro Study.

    Science.gov (United States)

    Eapen, Ashly Mary; Amirtharaj, L Vijay; Sanjeev, Kavitha; Mahalaxmi, Sekar

    2017-09-01

    The purpose of this in vitro study was to comparatively evaluate the fracture resistance of endodontically treated teeth restored with 2 fiber-reinforced composite resins and 2 conventional composite resin core buildup materials. Sixty noncarious unrestored human maxillary premolars were collected, endodontically treated (except group 1, negative control), and randomly divided into 5 groups (n = 10). Group 2 was the positive control. The remaining 40 prepared teeth were restored with various direct core buildup materials as follows: group 3 teeth were restored with dual-cure composite resin, group 4 with posterior composite resin, group 5 with fiber-reinforced composite resin, and group 6 with short fiber-reinforced composite resin. Fracture strength testing was performed using a universal testing machine. The results were statistically analyzed by 1-way analysis of variance and the post hoc Tukey test. Fracture patterns for each sample were also examined under a light microscope to determine the level of fractures. The mean fracture resistance values (in newtons) were obtained as group 1 > group 6 > group 4 > group 3 > group 5 > group 2. Group 6 showed the highest mean fracture resistance value, which was significantly higher than the other experimental groups, and all the fractures occurred at the level of enamel. Within the limitations of this study, a short fiber-reinforced composite can be used as a direct core buildup material that can effectively resist heavy occlusal forces against fracture and may reinforce the remaining tooth structure in endodontically treated teeth. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  3. Adhesive Properties of Bonded Orthodontic Retainers to Enamel : Stainless Steel Wire vs Fiber-reinforced Composites

    NARCIS (Netherlands)

    Foek, Dave Lie Sam; Krebs, Eliza; Sandham, John; Ozcan, Mutlu

    2009-01-01

    Purpose: The objectives of this study were to compare the bond strength of a stainless steel orthodontic wire vs various fiber-reinforced composites (FRC) used as orthodontic retainers on enamel, analyze the failure types after debonding, and investigate the influence of different application

  4. An emerging alternative to thermal curing: Electron curing of fiber-reinforced composites

    International Nuclear Information System (INIS)

    Singh, A.; Saunders, C.B.; Lopata, V.J.; Kremers, W.; Chung, M.

    1995-01-01

    Electron curing of fiber-reinforced composites to produce materials with good mechanical properties has been demonstrated by the authors' work, and by Aerospatiale. The attractions of this technology are the technical and processing advantages offered over thermal curing, and the projected cost benefits. Though the work so far has focused on the higher value composites for the aircraft and aerospace industries, the technology can also be used to produce composites for the higher volume industries, such as transportation and automotive

  5. Mechanical Behavior of Stainless Steel Fiber-Reinforced Composites Exposed to Accelerated Corrosion

    Science.gov (United States)

    O’Brien, Caitlin; McBride, Amanda; E. Zaghi, Arash; Burke, Kelly A.; Hill, Alex

    2017-01-01

    Recent advancements in metal fibers have introduced a promising new type of stainless steel fiber with high stiffness, high failure strain, and a thickness corrosion. The main goal of this study is to compare the impact of corrosion on the mechanical properties of steel fiber-reinforced composites with those of conventional types of stainless steel. By providing experimental evidences, this study may promote the application of steel fiber-reinforced composite as a viable alternative to conventional metals. Samples of steel fiber-reinforced polymer and four different types of stainless steel were subjected to 144 and 288 h of corrosion in ferric chloride solution to simulate accelerated corrosion conditions. The weight losses due to corrosion were recorded. The corroded and control samples were tested under monotonic tensile loading to measure the ultimate stresses and strains. The effect of corrosion on the mechanical properties of the different materials was evaluated. The digital image correlation (DIC) technique was used to investigate the failure mechanism of the corrosion-damaged specimens. Overall, steel fiber-reinforced composites had the greatest corrosion resistance. PMID:28773132

  6. Behavior of Fiber-Reinforced Smart Soft Composite Actuators According to Material Composition

    Energy Technology Data Exchange (ETDEWEB)

    Han, Min-Woo; Kim, Hyung-Il; Song, Sung-Hyuk; Ahn, Sung-Hoon [Seoul Nat’l Univ., Seoul (Korea, Republic of)

    2017-02-15

    Fiber-reinforced polymer composites, which are made by combining a continuous fiber that acts as reinforcement and a homogeneous polymeric material that acts as a host, are engineering materials with high strength and stiffness and a lightweight structure. In this study, a shape memory alloy(SMA) reinforced composite actuator is presented. This actuator is used to generate large deformations in single lightweight structures and can be used in applications requiring a high degree of adaptability to various external conditions. The proposed actuator consists of numerous individual laminas of the glass-fiber fabric that are embedded in a polymeric matrix. To characterize its deformation behavior, the composition of the actuator was changed by changing the matrix material and the number of the glass-fiber fabric layers. In addition, current of various magnitudes were applied to each actuator to study the effect of the heating of SMA wires on applying current.

  7. CO2-laser-assisted processing of glass fiber-reinforced thermoplastic composites

    Science.gov (United States)

    Brecher, Christian; Emonts, Michael; Schares, Richard Ludwig; Stimpfl, Joffrey

    2013-02-01

    To fully exploit the potential of fiber-reinforced thermoplastic composites (FRTC) and to achieve a broad industrial application, automated manufacturing systems are crucial. Investigations at Fraunhofer IPT have proven that the use of laser system technology in processing FRTC allows to achieve high throughput, quality, flexibility, reproducibility and out-of-autoclave processing simultaneously. As 90% of the FRP in Europe1 are glass fiber-reinforced a high impact can be achieved by introducing laser-assisted processing with all its benefits to glass fiber-reinforced thermoplastics (GFRTC). Fraunhofer IPT has developed the diode laser-assisted tape placement (laying and winding) to process carbon fiber-reinforced thermoplastic composites (CFRTC) for years. However, this technology cannot be transferred unchanged to process milky transparent GFRTC prepregs (preimpregnated fibers). Due to the short wavelength (approx. 980 nm) and therefore high transmission less than 20% of the diode laser energy is absorbed as heat into non-colored GFRTC prepregs. Hence, the use of a different wave length, e.g. CO2-laser (10.6 μm) with more than 90% laser absorption, is required to allow the full potential of laser-assisted processing of GFRTC. Also the absorption of CO2-laser radiation at the surface compared to volume absorption of diode laser radiation is beneficial for the interlaminar joining of GFRTC. Fraunhofer IPT is currently developing and investigating the CO2-laser-assisted tape placement including new system, beam guiding, process and monitoring technology to enable a resource and energy efficient mass production of GFRP composites, e.g. pipes, tanks, masts. The successful processing of non-colored glass fiber-reinforced Polypropylene (PP) and Polyphenylene Sulfide (PPS) has already been proven.

  8. Young modulus and internal friction of a fiber-reinforced composite

    International Nuclear Information System (INIS)

    Ledbetter, H.M.; Lei, M.; Austin, M.W.

    1986-01-01

    By a kilohertz-frequency resonance method we determined the Young modulus and internal friction of a uniaxially fiber-reinforced composite. The composite comprised glass fibers in an epoxy-resin matrix. We studied three fiber contents: 0, 41, and 49 vol %. The Young modulus fit a linear rule of mixture. The internal friction fit a classical free-damped-oscillator model where one assumes a linear rule of mixture for three quantities: mass, force constant, and mechanical-resistance constant

  9. Monotonic and cyclic responses of impact polypropylene and continuous glass fiber-reinforced impact polypropylene composites at different strain rates

    KAUST Repository

    Yudhanto, Arief; Lubineau, Gilles; Wafai, Husam; Mulle, Matthieu; Pulungan, Ditho Ardiansyah; Yaldiz, R.; Verghese, N.

    2016-01-01

    Impact copolymer polypropylene (IPP), a blend of isotactic polypropylene and ethylene-propylene rubber, and its continuous glass fiber composite form (glass fiber-reinforced impact polypropylene, GFIPP) are promising materials for impact

  10. Short fiber-reinforced composite restorations: A review of the current literature.

    Science.gov (United States)

    Garoushi, Sufyan; Gargoum, Ausama; Vallittu, Pekka K; Lassila, Lippo

    2018-02-25

    A newly-recommended method for restoring large cavities is the biomimetic approach of using short fiber-reinforced composite (SFRC) as dentine-replacing material. The aim of the current review was to present an overview of SFRC and to give the clinician a detailed understanding of this new material and treatment strategy based on available-literature review. A thorough literature search was done up to December 2017. The range of relevant publications was surveyed using PubMed and Google Scholar. From the search results, articles related to our search terms were only considered. The search terms used were "short fiber-reinforced composite", "everX posterior", and "fiber-reinforced composite restorations". Of the assessed articles selected (N = 70), most were laboratory-based research with various test specimen designs prepared according to the ISO standard or with extracted teeth; only four articles were clinical reports. A common finding was that by combining the SFRC as a bulk base with conventional composite, the load-bearing capacity and failure mode of the material combination were improved, as compared to plain conventional composite restoration. In the reviewed studies, the biomimetic restoration technique of using SFRC showed promising characteristics, and therefore, might be recommended as an alternative treatment option for large cavities. © 2018 John Wiley & Sons Australia, Ltd.

  11. Design and analysis of a novel latch system implementing fiber-reinforced composite materials

    Science.gov (United States)

    Guevara Arreola, Francisco Javier

    The use of fiber-reinforced composite materials have increased in the last four decades in high technology applications due to their exceptional mechanical properties and low weight. In the automotive industry carbon fiber have become popular exclusively in luxury cars because of its high cost. However, Carbon-glass hybrid composites offer an effective alternative to designers to implement fiber-reinforced composites into several conventional applications without a considerable price increase maintaining most of their mechanical properties. A door latch system is a complex mechanism that is under high loading conditions during car accidents such as side impacts and rollovers. Therefore, the Department of Transportation in The United States developed a series of tests that every door latch system comply in order to be installed in a vehicle. The implementation of fiber-reinforced composite materials in a door latch system was studied by analyzing the material behavior during the FMVSS No. 206 transverse test using computational efforts and experimental testing. Firstly, a computational model of the current forkbolt and detent structure was developed. Several efforts were conducted in order to create an effective and time efficient model. Two simplified models were implemented with two different contact interaction approaches. 9 composite materials were studied in forkbolt and 5 in detent including woven carbon fiber, unidirectional carbon fiber, woven carbon-glass fiber hybrid composites and unidirectional carbon-glass fiber hybrid composites. The computational model results showed that woven fiber-reinforced composite materials were stiffer than the unidirectional fiber-reinforced composite materials. For instance, a forkbolt made of woven carbon fibers was 20% stiffer than a forkbolt made of unidirectional fibers symmetrically stacked in 0° and 90° alternating directions. Furthermore, Hybrid composite materials behaved as expected in forkbolt noticing a decline

  12. A fiber-reinforced composite prosthesis restoring a lateral midfacial defect: a clinical report.

    Science.gov (United States)

    Kurunmäki, Hemmo; Kantola, Rosita; Hatamleh, Muhanad M; Watts, David C; Vallittu, Pekka K

    2008-11-01

    This clinical report describes the use of a glass fiber-reinforced composite (FRC) substructure to reinforce the silicone elastomer of a large facial prosthesis. The FRC substructure was shaped into a framework and embedded into the silicone elastomer to form a reinforced facial prosthesis. The prosthesis is designed to overcome the disadvantages associated with traditionally fabricated prostheses; namely, delamination of the silicone of the acrylic base, poor marginal adaptation over time, and poor simulation of facial expressions.

  13. Gigi Tiruan Cekat dengan Fiber-Reinforced Composites pada Kehilangan Gigi Anterior dengan Space Menyempit

    Directory of Open Access Journals (Sweden)

    Budi Santoso

    2011-06-01

    Full Text Available Latar belakang. Pada kasus kehilangan gigi-gigianterior tanpa penggantian secepatnya akan menyebabkan rasa malu, tidak percaya diri,gangguan berbicara dan bersuara, pergeseran gigi-gigitetangganya, tilting,hilangnyakontakantar gigi,elongasi gigi antagonisnya, traumatik oklusi, ginggival pocket serta karies pada gigi sebelahnya. Tujuan. Penulisan laporan ini untuk memberi informasi bahwa pada kasus kehilangan gigi anterior dengan space yang telah menyempit dapat dibuatkan protesa berupa gigi tiruan cekat dengan fiber-reinforced composites. Kasus. Seorang pasien laki-Iaki berusia 26 tahun datang ke RSGM dengan kasus kehilangan gigi incisivus centralis kiri atas dengan space mesio-distal yang telah menyempit. Penanganan. Setelah dilakukan pemeriksaan subyektif, obyektif dan radiografi maka dilakukan perawatan dengan protesa berupa gigi tiruan cekat dengan fiber-reinforced composites. Setelah 10 hari perawatan kemudian kontrol dan pad a pemeriksaan subyektif tidak ada keluhan. Pada pemeriksaan obyektif dilakukan pemeriksaan terhadap retensi, stabilisasi, oklusi, estetis dan warnanya. Kesimpulan. Hasil Perawatan gigi tiruan cekat dengan fiber-reinforced composites dapat memperbaiki kondisi kehilangan gigi dengan space mesio-distal yang telah menyempit sehingga mengembalikan estetika dan percaya diri pasien.

  14. Kenaf/Synthetic and Kevlar®/Cellulosic Fiber-Reinforced Hybrid Composites: A Review

    Directory of Open Access Journals (Sweden)

    Suhad D. Salman

    2015-08-01

    Full Text Available This paper reviews the published and ongoing research work on kenaf/synthetic and Kevlar®/cellulosic fiber-reinforced composite materials. The combination of natural fibers with synthetic fibers in hybrid composites has become increasingly applied in several different fields of technology and engineering. As a result, a better balance between performance and cost is expected to be achieved by 2015, through appropriate material design. This review is intended to provide an outline of the essential outcomes of those hybrid composite materials currently utilized, focusing on processing and mechanical and structural properties.

  15. Fatigue resistance and stiffness of glass fiber-reinforced urethane dimethacrylate composite.

    Science.gov (United States)

    Narva, Katja K; Lassila, Lippo V J; Vallittu, Pekka K

    2004-02-01

    Retentive properties of cast metal clasps decrease over time because of metal fatigue. Novel fiber-reinforced composite materials are purported to have increased fatigue resistance compared with metals and may offer a solution to the problem of metal fatigue. The aim of this study was to investigate the fatigue resistance and stiffness of E-glass fiber-reinforced composite. Twelve cylindrical fiber-reinforced composite test cylinders (2 mm in diameter and 60 mm in length) were made from light-polymerized urethane dimethacrylate monomer with unidirectional, single-stranded, polymer preimpregnated E-glass fiber reinforcement. Six cylinders were stored in dry conditions and 6 in distilled water for 30 days before testing. Fatigue resistance was measured by a constant-deflection fatigue test with 1 mm of deflection across a specimen span of 11 mm for a maximum of 150,000 loading cycles. The resistance of the cylinder against deflection was measured (N) and the mean values of the force were compared by 1-way analysis of variance (alpha = .05). The flexural modulus (GPa) was calculated for the dry and water-stored cylinders for the first loading cycle. Scanning electron microscopy was used to assess the distribution of the fibers, and the volume percent of fibers and polymer were assessed by combustion analysis. The test cylinders did not fracture due to fatigue following 150,000 loading cycles. Flexural modulus at the first loading cycle was 18.9 (+/- 2.9) GPa and 17.5 (+/- 1.7) GPa for the dry and water-stored cylinders, respectively. The mean force required to cause the first 1-mm deflection was 33.5 (+/- 5.2) N and 37.7 (+/- 3.6) N for the dry and water stored cylinders, respectively; however, the differences were not significant. After 150,000 cycles the mean force to cause 1-mm deflection was significantly reduced to 23.4 (+/- 8.5) N and 13.1 (+/- 3.5) N, respectively (P fiber- and polymer-rich areas within the specimens and indicated that individual fibers were

  16. Modeling of Stress Development During Thermal Damage Healing in Fiber-reinforced Composite Materials Containing Embedded Shape Memory Alloy Wires

    NARCIS (Netherlands)

    Bor, Teunis Cornelis; Warnet, Laurent; Akkerman, Remko; de Boer, Andries

    2010-01-01

    Fiber-reinforced composite materials are susceptible to damage development through matrix cracking and delamination. This article concerns the use of shape memory alloy (SMA) wires embedded in a composite material to support healing of damage through a local heat treatment. The composite material

  17. Mechanical and thermal properties of sisal fiber-reinforced rubber seed oil-based polyurethane composites

    International Nuclear Information System (INIS)

    Bakare, I.O.; Okieimen, F.E.; Pavithran, C.; Abdul Khalil, H.P.S.; Brahmakumar, M.

    2010-01-01

    The development of high-performance composite materials from locally sourced and renewable materials was investigated. Rubber seed oil polyurethane resin synthesized using rubber seed monoglyceride derived from glycerolysis of the oil was used as matrix in the composite samples. Rubber seed oil-based polyurethane composite reinforced with unidirectional sisal fibers were prepared and characterized. Results showed that the properties of unidirectional fiber-reinforced rubber seed oil-based polyurethane composites gave good thermal and mechanical properties. Also, the values of tensile strengths and flexural moduli of the polyurethane composites were more than tenfold and about twofold higher than un-reinforced rubber seed oil-based polyurethane. The improved thermal stability and the scanning electron micrographs of the fracture surface of the composites were attributed to good fiber-matrix interaction. These results indicate that high-performance 'all natural products' composite materials can be developed from resources that are readily available locally.

  18. Constitutive modeling of fiber-reinforced cement composites

    Science.gov (United States)

    Boulfiza, Mohamed

    The role of fibers in the enhancement of the inherently low tensile stress and strain capacities of fiber reinforced cementitious composites (FRC) has been addressed through both the phenomenological, using concepts of continuum damage mechanics, and micro-mechanical approaches leading to the development of a closing pressure that could be used in a cohesive crack analysis. The observed enhancements in the matrix behavior is assumed to be related to the ability of the material to transfer stress across cracks. In the micromechanics approach, this is modeled by the introduction of a nonlinear closing pressure at the crack lips. Due to the different nature of cracking in the pre-peak and post peak regimes, two different micro-mechanical models of the cohesive pressure have been proposed, one for the strain hardening stage and another for the strain softening regime. This cohesive pressure is subsequently incorporated into a finite element code so that a nonlinear fracture analysis can be carried out. On top of the fact that a direct fracture analysis has been performed to predict the response of some FRC structural elements, a numerical procedure for the homogenization of FRC materials has been proposed. In this latter approach, a link is established between the cracking taking place at the meso-scale and its mechanical characteristics as represented by the Young's modulus. A parametric study has been carried out to investigate the effect of crack patterning and fiber volume fractions on the overall Young's modulus and the thermodynamic force associated with the tensorial damage variable. After showing the usefulness and power of phenomenological continuum damage mechanics (PCDM) in the prediction of ERC materials' response to a stimuli (loading), a combined PCDM-NLFMsp1 approach is proposed to model (predict, forecast) the complete response of the composite up to failure. Based on experimental observations, this approach assumes that damage mechanics which predicts

  19. Micromechanical Modeling of Fiber-Reinforced Composites with Statistically Equivalent Random Fiber Distribution

    Directory of Open Access Journals (Sweden)

    Wenzhi Wang

    2016-07-01

    Full Text Available Modeling the random fiber distribution of a fiber-reinforced composite is of great importance for studying the progressive failure behavior of the material on the micro scale. In this paper, we develop a new algorithm for generating random representative volume elements (RVEs with statistical equivalent fiber distribution against the actual material microstructure. The realistic statistical data is utilized as inputs of the new method, which is archived through implementation of the probability equations. Extensive statistical analysis is conducted to examine the capability of the proposed method and to compare it with existing methods. It is found that the proposed method presents a good match with experimental results in all aspects including the nearest neighbor distance, nearest neighbor orientation, Ripley’s K function, and the radial distribution function. Finite element analysis is presented to predict the effective elastic properties of a carbon/epoxy composite, to validate the generated random representative volume elements, and to provide insights of the effect of fiber distribution on the elastic properties. The present algorithm is shown to be highly accurate and can be used to generate statistically equivalent RVEs for not only fiber-reinforced composites but also other materials such as foam materials and particle-reinforced composites.

  20. Low Velocity Impact Behavior of Basalt Fiber-Reinforced Polymer Composites

    Science.gov (United States)

    Shishevan, Farzin Azimpour; Akbulut, Hamid; Mohtadi-Bonab, M. A.

    2017-06-01

    In this research, we studied low velocity impact response of homogenous basalt fiber-reinforced polymer (BFRP) composites and then compared the impact key parameters with carbon fiber-reinforced polymer (CFRP) homogenous composites. BFRPs and CFRPs were fabricated by vacuum-assisted resin transfer molding (VARTM) method. Fabricated composites included 60% fiber and 40% epoxy matrix. Basalt and carbon fibers used as reinforcement materials were weaved in 2/2 twill textile tip in the structures of BFRP and CFRP composites. We also utilized the energy profile method to determine penetration and perforation threshold energies. The low velocity impact tests were carried out in 30, 60, 80, 100, 120 and 160 J energy magnitudes, and impact response of BFRPs was investigated by related force-deflection, force-time, deflection-time and absorbed energy-time graphics. The related impact key parameters such as maximum contact force, absorbed energy, deflection and duration time were compared with CFRPs for various impact energy levels. As a result, due to the higher toughness of basalt fibers, a better low velocity impact performance of BFRP than that of CFRP was observed. The effects of fabrication parameters, such as curing process, were studied on the low velocity impact behavior of BFRP. The results of tested new fabricated materials show that the change of fabrication process and curing conditions improves the impact behavior of BFRPs up to 13%.

  1. Fiber-reinforced plastic composites. Possibilities and limitations of applications as machine-construction materials

    Science.gov (United States)

    Ophey, Lothar

    1988-01-01

    The use of fiber-reinforced composite structural materials in engineering applications is discussed in a survey of currently available technology and future prospects. The ongoing rapid growth in the use of these materials is described, and the criteria to be applied in selecting base materials, lamination schemes, fasteners, and processing methods are examined in detail and illustrated with graphs, diagrams, flow charts, and drawings. A description of a sample application (comparing the properties of steel, CFRP, SiC-reinforced Al, CFRP/steel, and CFRP/Al automobile piston rods) is included.

  2. Impact strength on fiber-reinforced hybrid composite

    International Nuclear Information System (INIS)

    Firdaus, S M; Nurdina; Ariff, M Azmil

    2013-01-01

    Acrylonitrile-Butadiene-Styrene (ABS) has been well known composite in automotive players to have light weight with high impact strength material compared to sheet metal material which has high impact strength but heavy in weight. In this project, the impact strength properties of fabricated pure ABS were compared to the eight samples of hybrid ABS composite with different weight percentages of short fibers and particle sizes of ground rubber. The objective was to improve the impact strength in addition of short fibers and ground rubber particles. These samples were then characterized using an un-notched Izod impact test. Results show that the increasing of filler percentage yielded an adverse effect on the impact strength of the hybrid composite. The effect of the ground rubber particulate sizes however are deemed to be marginal than the effect of varying filler percentage based on the collected impact strength data from all physically tested hybrid composites

  3. Natural tooth pontic with splinting of periodontally weakened teeth using fiber-reinforced composite resin

    Directory of Open Access Journals (Sweden)

    Gauri Srinidhi

    2014-01-01

    Full Text Available Replacement of missing anterior teeth due to periodontal reasons is challenging due to the poor support of abutment teeth. This prevents the use of fixed partial dentures (FPDs. Fiber-reinforced splinting provides a viable alternative to the dentist while choosing a treatment plan in replacing missing anterior teeth in periodontally compromised patients as opposed to conventional modalities like FPDs or removable partial dentures. Replacing missing teeth using either patient′s own tooth or a denture tooth as pontic can be done by splinting adjacent teeth with fiber reinforced composite. The splinting has an additional advantage of stabilizing adjacent mobile teeth. This case report details the case selection, procedure with follow-up of a case where the natural extracted tooth of the patient was used as pontic to replace a missing anterior tooth. The splinting was done with fiber reinforced composite resin. Fiber-reinforced composite resin splinting of patient′s extracted natural tooth is economical, fast, and easy to use chairside technique with the added benefit of periodontal stabilization.

  4. Fracture resistance of class IV fiber-reinforced composite resin restorations: An in vitro study

    Directory of Open Access Journals (Sweden)

    P S Praveen Kumar

    2017-01-01

    Full Text Available Objectives: The aim of this study was to evaluate fracture resistance of incisal edge fractures (Class IV restored with a Glass Fiber-reinforced Composite (FRC. Materials and Methods: Twenty-four extracted sound maxillary central incisors were randomly divided into two groups. Group I (control contained untreated teeth. Samples in experimental groups II were prepared by cutting the incisal (one-third part of the crown horizontally and was subjected to enamel preparations, then restored with a Glass FRC. Fracture resistance was evaluated as Newton's for samples tested in a Hounsfield universal testing machine. Failure modes were examined microscopically. Results: Mean peak failure load (Newton's observed in Glass Fiber-reinforced Nanocomposite was 863.50 ± 76.12. The experimental group showed similar types of failure modes with the majority occurring as cohesive and mixed type. 58% of the teeth in Glass FRC group fractured below the cementoenamel junction. Conclusion: Using Fiber reinforced composite substructure under conventional composites in Class IV restorations, the fracture resistance of the restored incisal edge could be increased.

  5. Three-Dimensional Microvascular Fiber-Reinforced Composites

    Science.gov (United States)

    2011-03-01

    are varied to meet the desired design criteria. The interstitial pore space between fi bers is infi ltrated with a low-viscosity thermosetting resin...uid. d) μ CT image of composite with glass fi bers (blue) and channels fi lled with electrically conductive gallium–indium alloy (red). Probe

  6. Study on an Improved Phosphate Cement Binder for the Development of Fiber-Reinforced Inorganic Polymer Composites

    Directory of Open Access Journals (Sweden)

    Zhu Ding

    2014-11-01

    Full Text Available Magnesium phosphate cement (MPC has been proven to be a very good repair material for deteriorated concrete structures. It has excellent adhesion performance, leading to high bonding strength with old concrete substrates. This paper presents an experimental study into the properties of MPC binder as the matrix of carbon fiber sheets to form fiber-reinforced inorganic polymer (FRIP composites. The physical and mechanical performance of the fresh mixed and the hardened MPC paste, the bond strength of carbon fiber sheets in the MPC matrix, the tensile strength of the carbon FRIP composites and the microstructure of the MPC matrix and fiber-reinforced MPC composites were investigated. The test results showed that the improved MPC binder is well suited for developing FRIP composites, which can be a promising alternative to externally-bonded fiber-reinforced polymer (FRP composites for the strengthening of concrete structures. Through the present study, an in-depth understanding of the behavior of fiber-reinforced inorganic MPC composites has been achieved.

  7. Overall mechanical properties of fiber-reinforced metal matrix composites for fusion applications

    International Nuclear Information System (INIS)

    You, J.H.; Bolt, H.

    2002-01-01

    The high-temperature strength and creep properties are among the crucial criteria for the structural materials of plasma facing components (PFC) of fusion reactors, as they will be subjected to severe thermal stresses. The fiber-reinforced metal matrix composites are a potential heat sink material for the PFC application, since the combination of different material properties can lead to versatile performances. In this article, the overall mechanical properties of two model composites based on theoretical predictions are presented. The matrix materials considered were a precipitation hardened CuCrZr alloy and reduced activation martensitic steel 'Eurofer'. Continuous SiC fibers were used for the reinforcement. The results demonstrate that yield stress, ultimate tensile strength, work hardening rate and creep resistance could be extensively improved by the fiber reinforcement up to fiber content of 40 vol.%. The influence of the residual stresses on the plastic behavior of the composites is also discussed

  8. Near-Infrared Spectroscopic Method for Monitoring Water Content in Epoxy Resins and Fiber-Reinforced Composites

    Directory of Open Access Journals (Sweden)

    Andrey E. Krauklis

    2018-04-01

    Full Text Available Monitoring water content and predicting the water-induced drop in strength of fiber-reinforced composites are of great importance for the oil and gas and marine industries. Fourier transform infrared (FTIR spectroscopic methods are broadly available and often used for process and quality control in industrial applications. A benefit of using such spectroscopic methods over the conventional gravimetric analysis is the possibility to deduce the mass of an absolutely dry material and subsequently the true water content, which is an important indicator of water content-dependent properties. The objective of this study is to develop an efficient and detailed method for estimating the water content in epoxy resins and fiber-reinforced composites. In this study, Fourier transform near-infrared (FT-NIR spectroscopy was applied to measure the water content of amine-epoxy neat resin. The method was developed and successfully extended to glass fiber-reinforced composite materials. Based on extensive measurements of neat resin and composite samples of varying water content and thickness, regression was performed, and the quantitative absorbance dependence on water content in the material was established. The mass of an absolutely dry resin was identified, and the true water content was obtained. The method was related to the Beer–Lambert law and explained in such terms. A detailed spectroscopic method for measuring water content in resins and fiber-reinforced composites was developed and described.

  9. Near-Infrared Spectroscopic Method for Monitoring Water Content in Epoxy Resins and Fiber-Reinforced Composites.

    Science.gov (United States)

    Krauklis, Andrey E; Gagani, Abedin I; Echtermeyer, Andreas T

    2018-04-11

    Monitoring water content and predicting the water-induced drop in strength of fiber-reinforced composites are of great importance for the oil and gas and marine industries. Fourier transform infrared (FTIR) spectroscopic methods are broadly available and often used for process and quality control in industrial applications. A benefit of using such spectroscopic methods over the conventional gravimetric analysis is the possibility to deduce the mass of an absolutely dry material and subsequently the true water content, which is an important indicator of water content-dependent properties. The objective of this study is to develop an efficient and detailed method for estimating the water content in epoxy resins and fiber-reinforced composites. In this study, Fourier transform near-infrared (FT-NIR) spectroscopy was applied to measure the water content of amine-epoxy neat resin. The method was developed and successfully extended to glass fiber-reinforced composite materials. Based on extensive measurements of neat resin and composite samples of varying water content and thickness, regression was performed, and the quantitative absorbance dependence on water content in the material was established. The mass of an absolutely dry resin was identified, and the true water content was obtained. The method was related to the Beer-Lambert law and explained in such terms. A detailed spectroscopic method for measuring water content in resins and fiber-reinforced composites was developed and described.

  10. Investigation of degradation products produced by recycling the solvent during chemical degradation of fiber-reinforced composites

    DEFF Research Database (Denmark)

    Ucar, Hülya; Simonsen, Morten Enggrob; Søgaard, Erik Gydesen

    2017-01-01

    of the process. In this study, acetone has been used as the organic solvent. To increase the sustainability of the process, the solvent was recycled in eight consecutive batches using new glass fiber-reinforced composites in each recycling. No additional amount of acetone was added, resulting in a reduction...

  11. The use of maleic anhydride-modified polypropylene for performance enhancement in continuous glass fiber-reinforced polypropylene composites

    NARCIS (Netherlands)

    Rijsdijk, H.A.; Contant, M.; Peijs, A.A.J.M.; Miravete, A.

    1993-01-01

    The influence of maleic anhydride-modified polypropylene (m-PP) on static mech. properties of continuous glass fiber-reinforced polypropylene (PP) composites was studied. M-PP was added to the PP homopolymer to improve the adhesion between the matrix and the glass fiber. Three-point bending tests

  12. Fracture strength and bending of all-ceramic and fiber-reinforced composites in inlay-retained fixed partial dentures

    Directory of Open Access Journals (Sweden)

    Serkan Saridag

    2012-06-01

    Conclusions: Zirconia-based ceramic inlay-retained fixed partial dentures demonstrated the highest fracture strength. The fiber-reinforced composite inlay-retained fixed partial dentures demonstrated higher bending values than did the all-ceramic inlay-retained fixed partial dentures.

  13. Standard Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in Databases

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2000-01-01

    1.1 This guide establishes essential and desirable data elements for fiber-reinforced composite materials for two purposes: to establish the material identification component of data-reporting requirements for test reporting and to provide information for the design of material property databases. 1.1.1 This guide is the first part of a two-part modular approach. The first part serves to identify the material and the second part serves to describe testing procedures and variables and to record results. 1.1.2 For mechanical testing, the related document is Guide E 1434. The interaction of this guide with Guide E 1434 is emphasized by the common numbering of data elements. Data Elements A1 through G13 are included in this guide, and numbering of data elements in Guide E 1434 begins with H1 for the next data element block. This guide is most commonly used in combination with a guide for reporting the test procedures and results such as Guide E 1434. 1.2 These guidelines are specific to fiber-reinforced polyme...

  14. Esthetic rehabilitation of single anterior edentulous space using fiber-reinforced composite

    Directory of Open Access Journals (Sweden)

    Hyeon Kim

    2014-08-01

    Full Text Available A fiber-reinforced composite (FRC fixed prosthesis is an innovative alternative to a traditional metal restoration, as it is a conservative treatment method. This case report demonstrates a detailed procedure for restoring a missing anterior tooth with an FRC. A 44-year-old woman visited our department with an avulsed tooth that had fallen out on the previous day and was completely dry. This tooth was replanted, but it failed after one year. A semi-direct technique was used to fabricate a FRC fixed partial prosthesis for its replacement. The FRC framework and the pontic were fabricated using a duplicated cast model and nanofilled composite resin. Later on, interproximal contact, tooth shape, and shade were adjusted at chairside. This technique not only enables the clinician to replace a missing tooth immediately after extraction for minimizing esthetic problems, but it also decreases both tooth reduction and cost.

  15. Mechanical properties of Nextel trademark 312 fiber-reinforced SiC matrix composites

    International Nuclear Information System (INIS)

    Vaidyanathan, K.R.; Sankar, J.; Kelkar, A.D.; Weaver, B.

    1995-01-01

    Vapor phase synthesis is emerging as a method for the preparation of near final-shape, ceramic matrix composites for advanced structural applications. Oxide fiber-reinforced silicon carbide matrix composites are currently being developed for these applications. The mechanical properties of Nextel trademark 312 fiber reinforced SiC matrix composites fabricated employing the forced-flow, thermal gradient chemical vapor infiltration process (FCVI) were evaluated at room temperature in pure tension. The composites were fabricated with a 0.15 μm pyrolytic carbon interface layer for improving the toughness of the composite system. Because of the available FCVI apparatus, only short length specimens (7--8 cm) could be fabricated. Room temperature tensile strengths were measured and compared to room temperature flexure strength results for the composite. Excellent toughness and composite behavior was obtained for the composite system. Fractography as well as possible factors responsible for the differences in tensile and flexural strengths for the composite system is presented in this paper

  16. Thermo-hydroforming of a fiber-reinforced thermoplastic composites considering fiber orientations

    Science.gov (United States)

    Ahn, Hyunchul; Kuuttila, Nicholas Eric; Pourboghrat, Farhang

    2018-05-01

    The Thermoplastic woven composites were formed using a composite thermal hydroforming process, utilizing heated and pressurized fluid, similar to sheet metal forming. This study focuses on the modification of 300-ton pressure formation and predicts its behavior. Spectra Shield SR-3136 is used in this study and material properties are measured by experiments. The behavior of fiber-reinforced thermoplastic polymer composites (FRTP) was modeled using the Preferred Fiber Orientation (PFO) model and validated by comparing numerical analysis with experimental results. The thermo-hydroforming process has shown good results in the ability to form deep drawn parts with reduced wrinkles. Numerical analysis was performed using the PFO model and implemented as commercial finite element software ABAQUS / Explicit. The user subroutine (VUMAT) was used for the material properties of the thermoplastic composite layer. This model is suitable for working with multiple layers of composite laminates. Model parameters have been updated to work with cohesive zone model to calculate the interfacial properties between each composite layer. The results of the numerical modeling showed a good correlation with the molding experiment on the forming shape. Numerical results were also compared with experimental results on punch force-displacement curves for deformed geometry and forming processes of the composite layer. Overall, the shape of the deformed FRTP, including the distribution of wrinkles, was accurately predicted as shown in this study.

  17. Experimental Investigation on the Durability of Glass Fiber-Reinforced Polymer Composites Containing Nanocomposite

    Directory of Open Access Journals (Sweden)

    Weiwen Li

    2013-01-01

    Full Text Available Nanoclay layers incorporated into polymer/clay nanocomposites can inhibit the harmful penetration of water and chemicals into the material, and thus the durability of glass fiber-reinforced polymer (GFRP composites should be enhanced by using polymer/clay nanocomposite as the matrix material. In this study, 1.5 wt% vinyl ester (VE/organoclay and 2 wt% epoxy (EP/organoclay nanocomposites were prepared by an in situ polymerization method. The dispersion states of clay in the nanocomposites were studied by performing XRD analysis. GFRP composites were then fabricated with the prepared 1.5 wt% VE/clay and 2.0 wt% EP/clay nanocomposites to investigate the effects of a nanocomposite matrix on the durability of GFRP composites. The durability of the two kinds of GFRP composites was characterized by monitoring tensile properties following degradation of GFRP specimens aged in water and alkaline solution at 60°C, and SEM was employed to study fracture behaviors of aged GFRP composites under tension. The results show that tensile properties of the two types of GFRP composites with and without clay degrade significantly with aging time. However, the GFRP composites with nanoclay show a lower degradation rate compared with those without nanoclay, supporting the aforementioned hypothesis. And the modification of EP/GFRP enhanced the durability more effectively.

  18. Process for the preparation of fiber-reinforced ceramic composites by chemical vapor deposition

    Science.gov (United States)

    Lackey, Jr., Walter J.; Caputo, Anthony J.

    1986-01-01

    A chemical vapor deposition (CVD) process for preparing fiber-reinforced ceramic composites. A specially designed apparatus provides a steep thermal gradient across the thickness of a fibrous preform. A flow of gaseous ceramic matrix material is directed into the fibrous preform at the cold surface. The deposition of the matrix occurs progressively from the hot surface of the fibrous preform toward the cold surface. Such deposition prevents the surface of the fibrous preform from becoming plugged. As a result thereof, the flow of reactant matrix gases into the uninfiltrated (undeposited) portion of the fibrous preform occurs throughout the deposition process. The progressive and continuous deposition of ceramic matrix within the fibrous preform provides for a significant reduction in process time over known chemical vapor deposition processes.

  19. Stress-temperature-lifetime response of nicalon fiber-reinforced SiC composites in air

    International Nuclear Information System (INIS)

    Lin, Hua-Tay; Becher, P.F.

    1996-01-01

    Time-to-failure tests were conducted in four-point flexure and in air as a function of stress levels and temperatures to study the lifetime response of various Nicalon fiber-reinforced SiC (designated as Nic/SiC) composites with a graphitic interfacial coating. The results indicated that all of the Nic/SiC composites exhibit a similar stress-dependent failure at applied stress greater than a threshold value. In this case, the lifetimes of the composites increased with decrease in both stress level and test temperature. The lifetime of the composites appeared to be relatively insensitive to the thickness of graphitic interface layer and was enhanced somewhat by the addition of oxidation inhibitors. Electron microscopy and oxidation studies indicated that the life of the Nic/SiC composites was governed by the oxidation of the graphitic interfaces and the on of glass(es) in composites due to the oxidation of the fiber and matrix, inhibitor phases

  20. ZnO Piezoelectric Nanowires for Use in a Self-Powered Structural Health Monitoring Device for Fiber-Reinforced Composites Uploading Attachment Instructions

    Data.gov (United States)

    National Aeronautics and Space Administration — The goal of this proposed research is to develop a new self-powered structural health monitoring (SHM) system for fiber-reinforced polymer (FRP) composites by using...

  1. Effects of Interface Modification on Mechanical Behavior of Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites

    Science.gov (United States)

    Bansal, Narottam P.; Eldridge, Jeffrey I.

    1997-01-01

    Unidirectional celsian matrix composites having approx. 42 volume percent of uncoated or BN/SiC-coated Hi-Nicalon fibers were tested in three-point bend at room temperature. The uncoated fiber-reinforced composites showed catastrophic failure with strength of 210 +/- 35 MPa and a flat fracture surface. In contrast, composites reinforced with BN/SiC-coated fibers exhibited graceful failure with extensive fiber pullout. Values of first matrix cracking stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01 %, respectively, with ultimate strength as high as 960 MPa. The elastic Young's modulus of the uncoated and BN/SiC-coated fiber-reinforced composites were measured as 184 q 4 GPa and 165 +/- 5 GPa, respectively. Fiber push-through tests and microscopic examination indicated no chemical reaction at the uncoated or coated fiber-matrix interface. The low strength of the uncoated fiber-reinforced composite is probably due to degradation of the fibers from mechanical surface damage during processing. Because both the coated and uncoated fiber reinforced composites exhibited weak interfaces, the beneficial effect of the BN-SiC dual layer is primarily the protection of fibers from mechanical damage during processing.

  2. Effects of Subscale Size and Shape on Global Energy Dissipation in a Multiscale Model of a Fiber-Reinforced Composite Exhibiting Post-Peak Strain Softening Using Abaqus and FEAMAC

    Science.gov (United States)

    Pineda, Evan, J.; Bednarcyk, Brett, A.; Arnold, Steven, M.

    2012-01-01

    A mesh objective crack band model is implemented in the generalized method of cells (GMC) micromechanics model to predict failure of a composite repeating unit cell (RUC). The micromechanics calculations are achieved using the MAC/GMC core engine within the ImMAC suite of micromechanics codes, developed at the NASA Glenn Research Center. The microscale RUC is linked to a macroscale Abaqus/Standard finite element model using the FEAMAC multiscale framework (included in the ImMAC suite). The effects of the relationship between the characteristic length of the finite element and the size of the microscale RUC on the total energy dissipation of the multiscale model are investigated. A simple 2-D composite square subjected to uniaxial tension is used to demonstrate the effects of scaling the dimensions of the RUC such that the length of the sides of the RUC are equal to the characteristic length of the finite element. These results are compared to simulations where the size of the RUC is fixed, independent of the element size. Simulations are carried out for a variety of mesh densities and element shapes, including square and triangular. Results indicate that a consistent size and shape must be used to yield preserve energy dissipation across the scales.

  3. Fiber-Reinforced Epoxy Composites and Methods of Making Same Without the Use of Oven or Autoclave

    Science.gov (United States)

    Barnell, Thomas J. (Inventor); Rauscher, Michael D. (Inventor); Stienecker, Rick D. (Inventor); Nickerson, David M. (Inventor); Tong, Tat H. (Inventor)

    2016-01-01

    Method embodiments for producing a fiber-reinforced epoxy composite comprise providing a mold defining a shape for a composite, applying a fiber reinforcement over the mold, covering the mold and fiber reinforcement thereon in a vacuum enclosure, performing a vacuum on the vacuum enclosure to produce a pressure gradient, insulating at least a portion of the vacuum enclosure with thermal insulation, infusing the fiber reinforcement with a reactive mixture of uncured epoxy resin and curing agent under vacuum conditions, wherein the reactive mixture of uncured epoxy resin and curing agent generates exothermic heat, and producing the fiber-reinforced epoxy composite having a glass transition temperature of at least about 100.degree. C. by curing the fiber reinforcement infused with the reactive mixture of uncured epoxy resin and curing agent by utilizing the exothermically generated heat, wherein the curing is conducted inside the thermally insulated vacuum enclosure without utilization of an external heat source or an external radiation source.

  4. Flexural properties of polyethylene, glass and carbon fiber-reinforced resin composites for prosthetic frameworks.

    Science.gov (United States)

    Maruo, Yukinori; Nishigawa, Goro; Irie, Masao; Yoshihara, Kumiko; Minagi, Shogo

    2015-01-01

    High flexural properties are needed for fixed partial denture or implant prosthesis to resist susceptibility to failures caused by occlusal overload. The aim of this investigation was to clarify the effects of four different kinds of fibers on the flexural properties of fiber-reinforced composites. Polyethylene fiber, glass fiber and two types of carbon fibers were used for reinforcement. Seven groups of specimens, 2 × 2 × 25 mm, were prepared (n = 10 per group). Four groups of resin composite specimens were reinforced with polyethylene, glass or one type of carbon fiber. The remaining three groups served as controls, with each group comprising one brand of resin composite without any fiber. After 24-h water storage in 37°C distilled water, the flexural properties of each specimen were examined with static three-point flexural test at a crosshead speed of 0.5 mm/min. Compared to the control without any fiber, glass and carbon fibers significantly increased the flexural strength (p glass fiber (p glass fibers (p > 0.05). Fibers could, therefore, improve the flexural properties of resin composite and carbon fibers in longitudinal form yielded the better effects for reinforcement.

  5. Effect of Home Bleaching on Microleakage of Fiber-reinforced and Particle-filled Composite Resins

    Directory of Open Access Journals (Sweden)

    Farahnaz Sharafeddin

    2013-12-01

    Full Text Available Background and aims. Bleaching may exert some negative effects on existing composite resin restorations. The aim of this study was to evaluate the effect of home bleaching on microleakage of fiber-reinforced and particle-filled composite resins. Materials and methods. Ninety class V cavities (1.5×2×3 mm were prepared on the buccal surfaces of 90 bovine teeth. The teeth were randomly divided into 6 groups (n=15 and restored as follows: Groups 1 and 2 with Z100, groups 3 and 4 with Z250, and groups 5 and 6 with Nulite F composite resins. All the specimens were thermocycled. Groups 1, 3 and 5 were selected as control groups (without bleaching and the experimental groups 2, 4 and 6 were bleached with 22% carbamide peroxide gel. All the samples were immersed in 2% basic fuchsin dye for 24 hours and then sectioned longitudinally. Dye penetration was evaluated under a stereomicroscope (×25, at both the gingival and incisal margins. Data were analyzed using Kruskal-Wallis, Mann-Whitney and Wilcoxon tests (α=0.05. Results. Statistical analyses revealed that bleaching gel increased microleakage only at gingival margins with Z250 (P=0.007. Moreover, the control groups showed a statistically significant difference in microleakage at their gingival margins. Nulite F had the maximum microleakage while Z250 showed the minimum (P=0.006. Conclusion. Microleakage of home-bleached restorations might be related to the type of composite resin used.

  6. Effect of Accelerated Aging on Color Change of Direct and Indirect Fiber-Reinforced Composite Restorations

    Directory of Open Access Journals (Sweden)

    Masomeh Hasani Tabatabaei

    2016-10-01

    Full Text Available Objectives: The aim of this study was to assess the effect of artificial accelerated aging (AAA on color change of direct and indirect fiber-reinforced composite (FRC restorations.Materials and Methods: Direct (Z250 and indirect (Gradia composite resins were reinforced with glass (GF and polyethylene fibers (PF based on the manufacturers’ instructions. Forty samples were fabricated and divided into eight groups (n=5. Four groups served as experimental groups and the remaining four served as controls. Color change (∆E and color parameters (∆L*, ∆a*, ∆b* were read at baseline and after AAA based on the CIELAB system. Three-way ANOVA and Tukey’s test were used for statistical analysis.Results: Significant differences were found in ΔE, ΔL*, Δa* and Δb* among the groups after AAA (P<0.05. Most of the studied samples demonstrated an increase in lightness and a red-yellow shift after AAA.Conclusions: The obtained ∆E values were unacceptable after AAA (∆E≥ 3.3. All indirect samples showed a green-blue shift with a reduction in lightness except for Gradia/PF+ NuliteF.Keywords: Aging; Composite Resins; Color

  7. Physical and Mechanical Characteristics of Kevlar Fiber-Reinforced PC/ABS Composites

    Directory of Open Access Journals (Sweden)

    Kuljira Sujirote

    2012-01-01

    Full Text Available In this research, the composites between polycarbonate (PC and acrylonitrile-butadiene-styrene (ABS alloy and Kevlar fiber were prepared. The flexural and tensile properties of PC/ABS alloy and its composites were determined using a universal testing machine. The synergistic behavior of flexural modulus was observed for all regions of PC contents, while the synergism of flexural strength and tensile strength were found in some PC contents. It was found that the optimum weight ratio of PC:ABS was 60:40. In the Kevlar Fiber-reinforced PC/ABS composite system at PC:ABS of 60:40, both flexural modulus and strength were increased with matrix contents. Additionally, the flexural strength drastically increased with the matrix content and then reached the maximum value of 167 MPa at the matrix content of 33.4 wt%. The results from peel test, water contact measurement, and scanning electron microscopy (SEM reveal that the interfacial adhesion between the Kevlar fiber and the polymer matrix could be improved by increasing the PC content in the matrix.

  8. Microstructure changes and properties of TiC-coated carbon fiber-reinforced carbon composites

    International Nuclear Information System (INIS)

    Wang Kunjie; Guo Quangui; Zhang Guobing; Shi Jingli; Zhang Hua; Liu Lang

    2008-01-01

    In the present paper, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to study distortion of TiC crystals after thermal cycles in plasma environment. Scanning electron microscopy (SEM) was used to observe morphology changes and penetrating cracks in TiC/C coatings. To avoid the cracks and enhance properties of coated carbon fiber-reinforced carbon (C/C) composites, TiC/C composites were prepared as buffer layer to relieve thermal stresses. Thermal cycles indicated that the buffer layer could effectively improve thermal shock resistance of pure TiC coated C/C composites. To study the reason, transmission electron microscopy (TEM) results suggested that TiC particles were uniformly imbedded in pyrocarbon in the buffer layer, which was advantageous to relieve mismatch of coefficient of thermal expansion (CTE) between pure TiC and C/C. Moreover, thermal conductivity tests showed that the buffer layer was in favor of transferring heat loading

  9. The effect of the matrix superplastic deformation on interface reaction in fiber-reinforced composites

    International Nuclear Information System (INIS)

    Astanin, V.V.; Imayeva, L.A.

    1995-01-01

    It is known that superplastic deformation affects the processes o solid phases bonding. In particular, the effect of a character of matrix flow upon nucleation and growth of the reaction products at the fiber/matrix interface should be expected during consolidation of the fiber-reinforced composites under superplastic conditions. The matrix material flow in thin clearance (about 20μm) between strengthening fibers is a special feature of composite consolidation. In previous papers, it was shown that the character of the flow in thin specimens, when the specimen thickness is equal to several grain sizes, is very different from that in thick specimens. In this manner the question of the effect of the deformation on the fiber/matrix interface formation is complicated and one should consider the peculiarities of matrix deformation during the composite fabrication and the effect of localization of the deformation on the fiber/matrix interface reaction. In this paper, the authors shall focus on these two problems

  10. Standard Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2000-01-01

    1.1 This guide provides a common format for mechanical test data for composite materials for two purposes: (1) to establish data reporting requirements for test methods and ( 2) to provide information for the design of material property databases. This guide should be used in combination with Guide E 1309 which provides similar information to identify the composite material tested. 1.2 These guidelines are specific to mechanical tests of high-modulus fiber-reinforced composite materials. Types of tests considered in this guide include tension, compression, shear, flexure, open/filled hole, bearing, fracture toughness, and fatigue. The ASTM standards for which this guide was developed are listed in . The guidelines may also be useful for additional tests or materials. 1.3 This guide is the second part of a modular approach for which the first part is Guide E 1309. Guide E 1309 serves to identify the material, and this guide serves to describe mechanical testing procedures and variables and to record results....

  11. 3D-WOVEN FIBER-REINFORCED COMPOSITE FOR CAD/CAM DENTAL APPLICATION.

    Science.gov (United States)

    Petersen, Richard; Liu, Perng-Ru

    2016-05-01

    Three-dimensional (3D)-woven noncrimp fiber-reinforced composite (FRC) was tested for mechanical properties in the two principal directions of the main XY plane and compared to different Computer-Aided-Design/Computer-Aided-Machining (CAD/CAM) Dental Materials. The Dental Materials included ceramic with Vitablock Mark II®, ProCAD®, InCeram® Spinel, InCeram® Alumina and InCeram® Zirconia in addition to a resin-based 3M Corp. Paradigm® particulate-filled composite. Alternate material controls included Coors 300 Alumina Ceramic and a tungsten carbide 22% cobalt cermet. The 3D-woven FRC was vacuum assisted resin transfer molding processed as a one-depth-thickness ~19-mm preform with a vinyl-ester resin and cut into blocks similar to the commercial CAD/CAM Dental Materials. Mechanical test samples prepared for a flexural three-point span length of 10.0 mm were sectioned for minimum-depth cuts to compare machinability and fracture resistance between groups. 3D-woven FRC improved mechanical properties with significant statistical differences over all CAD/CAM Dental Materials and Coors Alumina Ceramic for flexural strength (p<0.001), resilience (p<0.05), work of fracture (p<0.001), strain energy release (p<0.05), critical stress intensity factor (p<0.001) and strain (p<0.001).

  12. Immediate Repair Bond Strength of Fiber-reinforced Composite after Saliva or Water Contamination.

    Science.gov (United States)

    Bijelic-Donova, Jasmina; Flett, Andrew; Lassila, Lippo V J; Vallittu, Pekka K

    2018-05-31

    This in vitro study aimed to evaluate the shear bond strength (SBS) of particulate filler composite (PFC) to saliva- or water-contaminated fiber-reinforced composite (FRC). One type of FRC substrate with semi-interpenetrating polymer matrix (semi-IPN) (everStick C&B) was used in this investigation. A microhybrid PFC (Filtek Z250) substrate served as control. Freshly cured PFC and FRC substrates were first subjected to different contamination and surface cleaning treatments, then the microhybrid PFC restorative material (Filtek Z250) was built up on the substrates in 2-mm increments and light cured. Uncontaminated and saliva- or water-contaminated substrate surfaces were either left untreated or were cleaned via phosphoric acid etching or water spray accompanied with or without adhesive composite application prior applying the adherent PFC material. SBS was evaluated after thermocycling the specimens (6000 cycles, 5°C and 55°C). Three-way ANOVA showed that both the surface contamination and the surface treatment signficantly affected the bond strength (p contamination reduced the SBS more than did the water contamination. SBS loss after saliva contamination was 73.7% and 31.3% for PFC and FRC, respectively. After water contamination, SBS loss was 17.2% and 13.3% for PFC and FRC, respectively. The type of surface treatment was significant for PFC (p contamination of freshly cured PFC or semi-IPN FRC, surfaces should be re-prepared via phosphoric acid etching, water cleaning, drying, and application of adhesive composite in order to recover optimal bond strength.

  13. Fiber-reinforced composite analysis using optical coherence tomography after mechanical and thermal cycling

    Science.gov (United States)

    Kyotoku, B. B. C.; Braz, A. K. S.; Braz, R.; Gomes, A. S. L.

    2007-02-01

    Fiber-reinforced composites are new materials which have been used for a variety of dental applications, including tooth splinting, replacement of missing teeth, treatment of dental emergencies, reinforcement of resin provisional fixed prosthodontic restorations, orthodontic retention, and other clinical applications. Different fiber types are available, but little clinical information has been disseminated. The traditional microscopy investigation, most commonly used to study this material, is a destructive technique, which requires specimen sectioning and are essentially surface measurements. On the basis of these considerations, the aim of this research is to analyze the interior of a dental sample reinforced with fiber after a mechanical and thermal cycling to emulate oral conditions using optical coherence tomography (OCT). The device we are using is a home built Fourier domain OCT working at 800 nm with 6 μm resolution. The results are compared with microscopy images to validate OCT as a working method. In long term, fractures allow bacterial invasion provoking plaque and calculus formation that can cause caries and periodontal disease. Therefore, non invasive imaging of the bridge fiber enables the possibility of periodic clinical evaluation to ensure the patient health. Furthermore, OCT images can provide a powerful method for quantitative analysis of crack propagation, and can potentially be used for in vivo assessment.

  14. Effect of fabric structure and polymer matrix on flexural strength, interlaminar shear stress, and energy dissipation of glass fiber-reinforced polymer composites

    Science.gov (United States)

    We report the effect of glass fiber structure and the epoxy polymer system on the flexural strength, interlaminar shear stress (ILSS), and energy absorption properties of glass fiber-reinforced polymer (GFRP) composites. Four different GFRP composites were fabricated from two glass fiber textiles of...

  15. Dynamic shear-lag model for understanding the role of matrix in energy dissipation in fiber-reinforced composites.

    Science.gov (United States)

    Liu, Junjie; Zhu, Wenqing; Yu, Zhongliang; Wei, Xiaoding

    2018-07-01

    Lightweight and high impact performance composite design is a big challenge for scientists and engineers. Inspired from well-known biological materials, e.g., the bones, spider silk, and claws of mantis shrimp, artificial composites have been synthesized for engineering applications. Presently, the design of ballistic resistant composites mainly emphasizes the utilization of light and high-strength fibers, whereas the contribution from matrix materials receives less attention. However, recent ballistic experiments on fiber-reinforced composites challenge our common sense. The use of matrix with "low-grade" properties enhances effectively the impact performance. In this study, we establish a dynamic shear-lag model to explore the energy dissipation through viscous matrix materials in fiber-reinforced composites and the associations of energy dissipation characteristics with the properties and geometries of constituents. The model suggests that an enhancement in energy dissipation before the material integrity is lost can be achieved by tuning the shear modulus and viscosity of a matrix. Furthermore, our model implies that an appropriately designed staggered microstructure, adopted by many natural composites, can repeatedly activate the energy dissipation process and thus improve dramatically the impact performance. This model demonstrates the role of matrix in energy dissipation, and stimulates new advanced material design concepts for ballistic applications. Biological composites found in nature often possess exceptional mechanical properties that man-made materials haven't be able to achieve. For example, it is predicted that a pencil thick spider silk thread can stop a flying Boeing airplane. Here, by proposing a dynamic shear-lag model, we investigate the relationships between the impact performance of a composite with the dimensions and properties of its constituents. Our analysis suggests that the impact performance of fiber-reinforced composites could improve

  16. Effect of carbon fiber dispersion on the mechanical properties of carbon fiber-reinforced cement-based composites

    International Nuclear Information System (INIS)

    Wang Chuang; Li Kezhi; Li Hejun; Jiao Gengsheng; Lu Jinhua; Hou Dangshe

    2008-01-01

    The preparation of carbon fiber-reinforced cement-based composites involved two-step dispersions of carbon fibers. Both steps affected greatly the mechanical properties of the composites. With the aid of ultrasonic wave, a new dispersant hydroxyethyl cellulose was used to help fiber dispersion in the first step. The fracture surface of the composites was observed by scanning electron microscopy. The distribution of major elements was analyzed by the energy dispersive spectroscopy and the composition was analyzed through X-ray diffraction. The flexural strength, tensile strength, modulus, and compression strength were measured. Results showed that the distribution of major elements varied with the variation of the fiber dispersion status. The compressive strength increased by 20%, the tensile strength was 2.4 times that of the material without carbon fibers, the modulus increased by 26.8%, whereas the flexure stress decreased by 12.9%

  17. Effects of Alkali Treatment and Polyisocyanate Crosslinking on the Mechanical Properties of Kraft Fiber-Reinforced Unsaturated Polyester Composites

    Directory of Open Access Journals (Sweden)

    Zhenhua Gao

    2014-08-01

    Full Text Available The effects of alkali treatment and polyisocyanate crosslinking on the mechanical properties of kraft fiber-reinforced UPE composites were investigated by means of tensile evaluation, SEM analysis, and XRD analysis. The results indicated that the alkali treatment decreased the tensile strength of the prepared composite before aging from 121 MPa to 97 MPa due to the decreased degree of crystallinity of the alkali-treated kraft fiber. Polyisocyanate crosslinking could apparently improve the mechanical properties and stability in terms of a 43% increase of non-aged tensile strength and 52% increase of hydrothermal-aged tensile strength compared with the controlled composite without crosslinking modification, which was attributable to the formation of strong chemical bonding between the interfaces of kraft fiber and polyester.

  18. Effects of Fiber Coating Composition on Mechanical Behavior of Silicon Carbide Fiber-Reinforced Celsian Composites

    Science.gov (United States)

    Bansal, Narottam P.; Elderidge, Jeffrey I.

    1998-01-01

    Celsian matrix composites reinforced with Hi-Nicalon fibers, precoated with a dual layer of BN/SiC by chemical vapor deposition in two separate batches, were fabricated. Mechanical properties of the composites were measured in three-point flexure. Despite supposedly identical processing, the composite panels fabricated with fibers coated in two batches exhibited substantially different mechanical behavior. The first matrix cracking stresses (sigma(sub mc)) of the composites reinforced with fibers coated in batch 1 and batch 2 were 436 and 122 MPa, respectively. This large difference in sigma(sub mc) was attributed to differences in fiber sliding stresses(tau(sub friction)), 121.2+/-48.7 and 10.4+/-3.1 MPa, respectively, for the two composites as determined by the fiber push-in method. Such a large difference in values of tau(sub friction) for the two composites was found to be due to the difference in the compositions of the interface coatings. Scanning Auger microprobe analysis revealed the presence of carbon layers between the fiber and BN, and also between the BN and SiC coatings in the composite showing lower tau(sub friction). This resulted in lower sigma(sub mc) in agreement with the ACK theory. The ultimate strengths of the two composites, 904 and 759 MPa, depended mainly on the fiber volume fraction and were not significantly effected by tau(sub friction) values, as expected. The poor reproducibility of the fiber coating composition between the two batches was judged to be the primary source of the large differences in performance of the two composites.

  19. Effect of Different Liners on Fracture Resistance of Premolars Restored with Conventional and Short Fiber-Reinforced Composite Resins.

    Science.gov (United States)

    Shafiei, Fereshteh; Doozandeh, Maryam; Ghaffaripour, Dordaneh

    2018-01-11

    To see whether applying four different liners under short fiber-reinforced composite (SFRC), everX Posterior, compared to conventional composite resin, Z250, affected their strengthening property in premolar MOD cavities. Mesio-occluso-distal (MOD) cavities were prepared in 120 sound maxillary premolars divided into 10 groups (n = 12) in terms of two composite resin types and 4 liners or no liner. For each composite resin, in 5 groups no liner, resin-modified glass ionomer (RMGI), conventional flowable composite (COFL), self-adhesive flowable composite resin (SAFL), and self-adhesive resin cement (SARC) were applied prior to restoring incrementally. After water storage and thermocycling, static fracture resistance was tested. Data (in Newtons) were analyzed using two-way ANOVA (α = 0.05). Fracture resistance was significantly affected by composite resin type (p = 0.02), but not by the liner (p > 0.05). The interaction of the two factors was not statistically significant (p > 0.05). SFRC exhibited higher fracture strength (1470 ± 200 N) compared to conventional composite resin (1350 ± 290), irrespective of the application of liners. Application of SARC and SAFL liners led to a higher number of restorable fractures for both composite resins. The four liners can be used without interfering with the higher efficacy of SFRC, compared to conventional composite resins, to improve the fracture strength of premolar MOD cavities. © 2018 by the American College of Prosthodontists.

  20. Fatigue resistance, debonding force, and failure type of fiber-reinforced composite, polyethylene ribbon-reinforced, and braided stainless steel wire lingual retainers in vitro

    NARCIS (Netherlands)

    Foek, Dave Lie Sam; Yetkiner, Enver; Ozcan, Mutlu

    Objective: To analyze the fatigue resistance, debonding force, and failure type of fiber-reinforced composite, polyethylene ribbon-reinforced, and braided stainless steel wire lingual retainers in vitro. Methods: Roots of human mandibular central incisors were covered with silicone, mimicking the

  1. Time-Dependent Stress Rupture Strength Degradation of Hi-Nicalon Fiber-Reinforced Silicon Carbide Composites at Intermediate Temperatures

    Science.gov (United States)

    Sullivan, Roy M.

    2016-01-01

    The stress rupture strength of silicon carbide fiber-reinforced silicon carbide composites with a boron nitride fiber coating decreases with time within the intermediate temperature range of 700 to 950 degree Celsius. Various theories have been proposed to explain the cause of the time-dependent stress rupture strength. The objective of this paper is to investigate the relative significance of the various theories for the time-dependent strength of silicon carbide fiber-reinforced silicon carbide composites. This is achieved through the development of a numerically based progressive failure analysis routine and through the application of the routine to simulate the composite stress rupture tests. The progressive failure routine is a time-marching routine with an iterative loop between a probability of fiber survival equation and a force equilibrium equation within each time step. Failure of the composite is assumed to initiate near a matrix crack and the progression of fiber failures occurs by global load sharing. The probability of survival equation is derived from consideration of the strength of ceramic fibers with randomly occurring and slow growing flaws as well as the mechanical interaction between the fibers and matrix near a matrix crack. The force equilibrium equation follows from the global load sharing presumption. The results of progressive failure analyses of the composite tests suggest that the relationship between time and stress-rupture strength is attributed almost entirely to the slow flaw growth within the fibers. Although other mechanisms may be present, they appear to have only a minor influence on the observed time-dependent behavior.

  2. Reaction sintering of two-dimensional silicon carbide fiber-reinforced silicon carbide composite by sheet stacking method

    International Nuclear Information System (INIS)

    Yoshida, Katsumi; Mukai, Hideki; Imai, Masamitsu; Hashimoto, Kazuaki; Toda, Yoshitomo; Hyuga, Hideki; Kondo, Naoki; Kita, Hideki; Yano, Toyohiko

    2007-01-01

    Two-dimensionally plain woven SiC fiber-reinforced SiC composite has been developed by reaction sintering using a sheet stacking method in order to further increase mechanical and thermal properties of the composite and to obtain flexibility of manufacturing process of 2D woven SiC/SiC composites which can be applied to the fabrication of larger parts. In addition, sinterability and mechanical properties of the composite were investigated. In this study, relative density of the composites was about 90-93% and a dense composite could be obtained by reaction sintering using the sheet stacking method. The bulk density and maximum bending strength of SiC/SiC composite with a C/SiC weight ratio of 0.6 were higher than that of the composite with C/SiC ratios of 0.5 or 0.7. The values were 2.9 g/cm 3 and 200 MPa, respectively. However, the composites obtained in this study fractured in almost brittle manner due to the lower fiber volume fraction

  3. Designing the fiber volume ratio in SiC fiber-reinforced SiC ceramic composites under Hertzian stress

    International Nuclear Information System (INIS)

    Lee, Kee Sung; Jang, Kyung Soon; Park, Jae Hong; Kim, Tae Woo; Han, In Sub; Woo, Sang Kuk

    2011-01-01

    Highlights: → Optimum fiber volume ratios in the SiC/SiC composite layers were designed under Hertzian stress. → FEM analysis and spherical indentation experiments were undertaken. → Boron nitride-pyrocarbon double coatings on the SiC fiber were effective. → Fiber volume ratio should be designed against flexural stress. -- Abstract: Finite element method (FEM) analysis and experimental studies are undertaken on the design of the fiber volume ratio in silicon carbide (SiC) fiber-reinforced SiC composites under indentation contact stresses. Boron nitride (BN)/Pyrocarbon (PyC) are selected as the coating materials for the SiC fiber. Various SiC matrix/coating/fiber/coating/matrix structures are modeled by introducing a woven fiber layer in the SiC matrix. Especially, this study attempts to find the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics under Hertzian stress. The analysis is performed by changing the fiber type, fiber volume ratio, coating material, number of coating layers, and stacking sequence of the coating layers. The variation in the stress for composites in relation to the fiber volume ratio in the contact axial or radial direction is also analyzed. The same structures are fabricated experimentally by a hot process, and the mechanical behaviors regarding the load-displacement are evaluated using the Hertzian indentation method. Various SiC matrix/coating/fiber/coating/matrix structures are fabricated, and mechanical characterization is performed by changing the coating layer, according to the introduction (or omission) of the coating layer, and the number of woven fiber mats. The results show that the damage mode changes from Hertzian stress to flexural stress as the fiber volume ratio increases in composites because of the decreased matrix volume fraction, which intensifies the radial crack damage. The result significantly indicates that the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics should be designed for

  4. Mechanical properties of banana/kenaf fiber-reinforced hybrid polyester composites: Effect of woven fabric and random orientation

    International Nuclear Information System (INIS)

    Alavudeen, A.; Rajini, N.; Karthikeyan, S.; Thiruchitrambalam, M.; Venkateshwaren, N.

    2015-01-01

    Highlights: • This paper is presents the fabrications of kenaf/banana fiber hybrid composites. • Effect of weaving pattern and random orientation on mechanical properties was studied. • Role of interfacial adhesion due to chemical modifications were analyzed with the aid of SEM. • Hybridization of kenaf and banana fibers in plain woven composites exhibits maximum mechanical strength. - Abstract: The present work deals with the effect of weaving patterns and random orientatation on the mechanical properties of banana, kenaf and banana/kenaf fiber-reinforced hybrid polyester composites. Composites were prepared using the hand lay-up method with two different weaving patterns, namely, plain and twill type. Of the two weaving patterns, the plain type showed improved tensile properties compared to the twill type in all the fabricated composites. Furthermore, the maximum increase in mechanical strength was observed in the plain woven hybrid composites rather than in randomly oriented composites. This indicates minimum stress development at the interface of composites due to the distribution of load transfer along the fiber direction. Moreover, alkali (NaOH) and sodium lauryl sulfate (SLS) treatments appear to provide an additional improvement in mechanical strength through enhanced interfacial bonding. Morphological studies of fractured mechanical testing samples were performed by scanning electron microscopy (SEM) to understand the de-bonding of fiber/matrix adhesion

  5. On the Theory and Numerical Simulation of Cohesive Crack Propagation with Application to Fiber-Reinforced Composites

    Science.gov (United States)

    Rudraraju, Siva Shankar; Garikipati, Krishna; Waas, Anthony M.; Bednarcyk, Brett A.

    2013-01-01

    The phenomenon of crack propagation is among the predominant modes of failure in many natural and engineering structures, often leading to severe loss of structural integrity and catastrophic failure. Thus, the ability to understand and a priori simulate the evolution of this failure mode has been one of the cornerstones of applied mechanics and structural engineering and is broadly referred to as "fracture mechanics." The work reported herein focuses on extending this understanding, in the context of through-thickness crack propagation in cohesive materials, through the development of a continuum-level multiscale numerical framework, which represents cracks as displacement discontinuities across a surface of zero measure. This report presents the relevant theory, mathematical framework, numerical modeling, and experimental investigations of through-thickness crack propagation in fiber-reinforced composites using the Variational Multiscale Cohesive Method (VMCM) developed by the authors.

  6. Improvement of Interfacial Adhesion of Incorporated Halloysite-Nanotubes in Fiber-Reinforced Epoxy-Based Composites

    Directory of Open Access Journals (Sweden)

    Jin-Woo Lee

    2017-04-01

    Full Text Available The heart of composite materials depends on the characteristics of their interface. The physical properties of composite materials are often described by the rule of mixtures, representing the average physical properties of the reinforcement and the matrix resin. However, in practical applications there are situations which arise where the rule of mixtures is not followed. This is because when an external energy applied to the composite material is transferred from the matrix to the reinforcement, the final physical properties are affected by the interface between them rather than the intrinsic properties of both the reinforcement and the matrix. The internal bonding strength of the interface of these composites can be enhanced by enhancing the bonding strength by adding a small amount of material at the interface. In this study, the mechanical properties were evaluated by producing a carbon fiber-reinforced composite material and improved by dispersing halloysite nanotubes (HNTs and the epoxy resin using an ultrasonic homogenizer. The interfacial bond strength increased with the addition of HNT. On the other hand, the addition of HNTs more than 3 wt % did not show the reinforcing effect by HNT agglomeration.

  7. Thermographic Non-Destructive Evaluation for Natural Fiber-Reinforced Composite Laminates

    Directory of Open Access Journals (Sweden)

    Hai Zhang

    2018-02-01

    Full Text Available Natural fibers, including mineral and plant fibers, are increasingly used for polymer composite materials due to their low environmental impact. In this paper, thermographic non-destructive inspection techniques were used to evaluate and characterize basalt, jute/hemp and bagasse fibers composite panels. Different defects were analyzed in terms of impact damage, delaminations and resin abnormalities. Of particular interest, homogeneous particleboards of sugarcane bagasse, a new plant fiber material, were studied. Pulsed phase thermography and principal component thermography were used as the post-processing methods. In addition, ultrasonic C-scan and continuous wave terahertz imaging were also carried out on the mineral fiber laminates for comparative purposes. Finally, an analytical comparison of different methods was given.

  8. Effect of Fiber Poisson Contraction on Matrix Multicracking Evolution of Fiber-Reinforced Ceramic-Matrix Composites

    Science.gov (United States)

    Longbiao, Li

    2015-12-01

    An analytical methodology has been developed to investigate the effect of fiber Poisson contraction on matrix multicracking evolution of fiber-reinforced ceramic-matrix composites (CMCs). The modified shear-lag model incorporated with the Coulomb friction law is adopted to solve the stress distribution in the interface slip region and intact region of the damaged composite. The critical matrix strain energy criterion which presupposes the existence of an ultimate or critical strain energy limit beyond which the matrix fails has been adopted to describe matrix multicracking of CMCs. As more energy is placed into the composite, matrix fractures and the interface debonding occurs to dissipate the extra energy. The interface debonded length under the process of matrix multicracking is obtained by treating the interface debonding as a particular crack propagation problem along the fiber/matrix interface. The effects of the interfacial frictional coefficient, fiber Poisson ratio, fiber volume fraction, interface debonded energy and cycle number on the interface debonding and matrix multicracking evolution have been analyzed. The theoretical results are compared with experimental data of unidirectional SiC/CAS, SiC/CAS-II and SiC/Borosilicate composites.

  9. Development of high-speed reactive processing system for carbon fiber-reinforced polyamide-6 composite: In-situ anionic ring-opening polymerization

    International Nuclear Information System (INIS)

    Kim, Sang-Woo; Seong, Dong Gi; Yi, Jin-Woo; Um, Moon-Kwang

    2016-01-01

    In order to manufacture carbon fiber-reinforced polyamide-6 (PA-6) composite, we optimized the reactive processing system. The in-situ anionic ring-opening polymerization of ε-caprolactam was utilized with proper catalyst and initiator for PA-6 matrix. The mechanical properties such as tensile strength, inter-laminar shear strength and compressive strength of the produced carbon fiber-reinforced PA-6 composite were measured, which were compared with the corresponding scanning electron microscope (SEM) images to investigate the polymer properties as well as the interfacial interaction between fiber and polymer matrix. Furthermore, kinetics of in-situ anionic ring-opening polymerization of ε-caprolactam will be discussed in the viewpoint of increasing manufacturing speed and interfacial bonding between PA-6 matrix and carbon fiber during polymerization.

  10. Development of high-speed reactive processing system for carbon fiber-reinforced polyamide-6 composite: In-situ anionic ring-opening polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang-Woo; Seong, Dong Gi; Yi, Jin-Woo; Um, Moon-Kwang [Composites Research Division, Korea Institute of Materials Science (KIMS), Changwon, Gyeongnam, 642–831 (Korea, Republic of)

    2016-05-18

    In order to manufacture carbon fiber-reinforced polyamide-6 (PA-6) composite, we optimized the reactive processing system. The in-situ anionic ring-opening polymerization of ε-caprolactam was utilized with proper catalyst and initiator for PA-6 matrix. The mechanical properties such as tensile strength, inter-laminar shear strength and compressive strength of the produced carbon fiber-reinforced PA-6 composite were measured, which were compared with the corresponding scanning electron microscope (SEM) images to investigate the polymer properties as well as the interfacial interaction between fiber and polymer matrix. Furthermore, kinetics of in-situ anionic ring-opening polymerization of ε-caprolactam will be discussed in the viewpoint of increasing manufacturing speed and interfacial bonding between PA-6 matrix and carbon fiber during polymerization.

  11. Assessment of Tensile Bond Strength of Fiber-Reinforced Composite Resin to Enamel Using Two Types of Resin Cements and Three Surface Treatment Methods

    Directory of Open Access Journals (Sweden)

    Tahereh Ghaffari

    2015-10-01

    Full Text Available Background: Resin-bonded bridgework with a metal framework is one of the most conservative ways to replace a tooth with intact abutments. Visibility of metal substructure and debonding are the complications of these bridgeworks. Today, with the introduction of fiber-reinforced composite resins, it is possible to overcome these complications. The aim of this study was to evaluate the bond strength of fiber-reinforced composite resin materials (FRC to enamel. Methods: Seventy-two labial cross-sections were prepared from intact extracted teeth. Seventy-two rectangular samples of cured Vectris were prepared and their thickness was increased by adding Targis. The samples were divided into 3 groups for three different surface treatments: sandblasting, etching with 9% hydrofluoric acid, and roughening with a round tapered diamond bur. Each group was then divided into two subgroups for bonding to etched enamel by Enforce and Variolink II resin cements. Instron universal testing machine was used to apply a tensile force. The fracture force was recorded and the mode of failure was identified under a reflective microscope. Results: There were no significant differences in bond strength between the three surface treatment groups (P=0.53. The mean bond strength of Variolink II cement was greater than that of Enforce (P=0.04. There was no relationship between the failure modes (cohesive and adhesive and the two cement types. There was some association between surface treatment and failure mode. There were adhesive failures in sandblasted and diamond-roughened groups and the cohesive failure was dominant in the etched group. Conclusion: It is recommended that restorations made of fiber-reinforced composite resin be cemented with VariolinkII and surface-treated by hydrofluoric acid.   Keywords: Tensile bond strength; surface treatment methods; fiber-reinforced composite resin

  12. A glass fiber-reinforced composite - bioactive glass cranioplasty implant: A case study of an early development stage implant removed due to a late infection.

    Science.gov (United States)

    Posti, Jussi P; Piitulainen, Jaakko M; Hupa, Leena; Fagerlund, Susanne; Frantzén, Janek; Aitasalo, Kalle M J; Vuorinen, Ville; Serlo, Willy; Syrjänen, Stina; Vallittu, Pekka K

    2015-03-01

    This case study describes the properties of an early development stage bioactive glass containing fiber-reinforced composite calvarial implant with histology that has been in function for two years and three months. The patient is a 33-year old woman with a history of substance abuse, who sustained a severe traumatic brain injury later unsuccessfully treated with an autologous bone flap and a custom-made porous polyethylene implant. She was thereafter treated with developmental stage glass fiber-reinforced composite - bioactive glass implant. After two years and three months, the implant was removed due to an implant site infection. The implant was analyzed histologically, mechanically, and in terms of chemistry and dissolution of bioactive glass. Mechanical integrity of the load bearing fiber-reinforced composite part of the implant was not affected by the in vivo period. Bioactive glass particles demonstrated surface layers of hydroxyapatite like mineral and dissolution, and related increase of pH was considerably less after two and three months period than that for fresh bioactive glass. There was a difference in the histology of the tissues inside the implant areas near to the margin of the implant that absorbed blood during implant installation surgery, showed fibrous tissue with blood vessels, osteoblasts, collagenous fibers with osteoid formation, and tiny clusters of more mature hard tissue. In the center of the implant, where there was less absorbed blood, only fibrous tissue was observed. This finding is in line with the combined positron emission tomography - computed tomography examination with (18F)-fluoride marker, which demonstrated activity of the mineralizing bone by osteoblasts especially at the area near to the margin of the implant 10 months after implantation. Based on these promising reactions found in the bioactive glass containing fiber-reinforced composite implant that has been implanted for two years and three months, calvarial

  13. Physical Principles Pertaining to Ultrasonic and Mechanical Properties of Anisotropic Media and Their Application to Nondestructive Evaluation of Fiber-Reinforced Composite Materials

    Science.gov (United States)

    Handley, Scott Michael

    The central theme of this thesis is to contribute to the physics underlying the mechanical properties of highly anisotropic materials. Our hypothesis is that a fundamental understanding of the physics involved in the interaction of interrogating ultrasonic waves with anisotropic media will provide useful information applicable to quantitative ultrasonic measurement techniques employed for the determination of material properties. Fiber-reinforced plastics represent a class of advanced composite materials that exhibit substantial anisotropy. The desired characteristics of practical fiber -reinforced composites depend on average mechanical properties achieved by placing fibers at specific angles relative to the external surfaces of the finished part. We examine the physics underlying the use of ultrasound as an interrogation probe for determination of ultrasonic and mechanical properties of anisotropic materials such as fiber-reinforced composites. Fundamental constituent parameters, such as elastic stiffness coefficients (c_{rm IJ}), are experimentally determined from ultrasonic time-of-flight measurements. Mechanical moduli (Poisson's ratio, Young's and shear modulus) descriptive of the anisotropic mechanical properties of unidirectional graphite/epoxy composites are obtained from the ultrasonically determined stiffness coefficients. Three-dimensional visualizations of the anisotropic ultrasonic and mechanical properties of unidirectional graphite/epoxy composites are generated. A related goal of the research is to strengthen the connection-between practical ultrasonic nondestructive evaluation methods and the physics underlying quantitative ultrasonic measurements for the assessment of manufactured fiber-reinforced composites. Production defects such as porosity have proven to be of substantial concern in the manufacturing of composites. We investigate the applicability of ultrasonic interrogation techniques for the detection and characterization of porosity in

  14. Optimal design of variable-stiffness fiber-reinforced composites using cellular automata

    NARCIS (Netherlands)

    Setoodeh, S.

    2005-01-01

    Growing number of applications of composites materials in aerospace and naval structures along with advancements in manufacturing technologies demand continuous innovations in design of composite structures. In the traditional design of composite laminates, fiber orientation angles are constant for

  15. A Testing Platform for Durability Studies of Polymers and Fiber-reinforced Polymer Composites under Concurrent Hygrothermo-mechanical Stimuli

    Science.gov (United States)

    Gomez, Antonio; Pires, Robert; Yambao, Alyssa; La Saponara, Valeria

    2014-01-01

    The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus. PMID:25548950

  16. UV-Assisted 3D Printing of Glass and Carbon Fiber-Reinforced Dual-Cure Polymer Composites.

    Science.gov (United States)

    Invernizzi, Marta; Natale, Gabriele; Levi, Marinella; Turri, Stefano; Griffini, Gianmarco

    2016-07-16

    Glass (GFR) and carbon fiber-reinforced (CFR) dual-cure polymer composites fabricated by UV-assisted three-dimensional (UV-3D) printing are presented. The resin material combines an acrylic-based photocurable resin with a low temperature (140 °C) thermally-curable resin system based on bisphenol A diglycidyl ether as base component, an aliphatic anhydride (hexahydro-4-methylphthalic anhydride) as hardener and (2,4,6,-tris(dimethylaminomethyl)phenol) as catalyst. A thorough rheological characterization of these formulations allowed us to define their 3D printability window. UV-3D printed macrostructures were successfully demonstrated, giving a clear indication of their potential use in real-life structural applications. Differential scanning calorimetry and dynamic mechanical analysis highlighted the good thermal stability and mechanical properties of the printed parts. In addition, uniaxial tensile tests were used to assess the fiber reinforcing effect on the UV-3D printed objects. Finally, an initial study was conducted on the use of a sizing treatment on carbon fibers to improve the fiber/matrix interfacial adhesion, giving preliminary indications on the potential of this approach to improve the mechanical properties of the 3D printed CFR components.

  17. A testing platform for durability studies of polymers and fiber-reinforced polymer composites under concurrent hygrothermo-mechanical stimuli.

    Science.gov (United States)

    Gomez, Antonio; Pires, Robert; Yambao, Alyssa; La Saponara, Valeria

    2014-12-11

    The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus.

  18. UV-Assisted 3D Printing of Glass and Carbon Fiber-Reinforced Dual-Cure Polymer Composites

    Directory of Open Access Journals (Sweden)

    Marta Invernizzi

    2016-07-01

    Full Text Available Glass (GFR and carbon fiber-reinforced (CFR dual-cure polymer composites fabricated by UV-assisted three-dimensional (UV-3D printing are presented. The resin material combines an acrylic-based photocurable resin with a low temperature (140 °C thermally-curable resin system based on bisphenol A diglycidyl ether as base component, an aliphatic anhydride (hexahydro-4-methylphthalic anhydride as hardener and (2,4,6,-tris(dimethylaminomethylphenol as catalyst. A thorough rheological characterization of these formulations allowed us to define their 3D printability window. UV-3D printed macrostructures were successfully demonstrated, giving a clear indication of their potential use in real-life structural applications. Differential scanning calorimetry and dynamic mechanical analysis highlighted the good thermal stability and mechanical properties of the printed parts. In addition, uniaxial tensile tests were used to assess the fiber reinforcing effect on the UV-3D printed objects. Finally, an initial study was conducted on the use of a sizing treatment on carbon fibers to improve the fiber/matrix interfacial adhesion, giving preliminary indications on the potential of this approach to improve the mechanical properties of the 3D printed CFR components.

  19. Monotonic and cyclic responses of impact polypropylene and continuous glass fiber-reinforced impact polypropylene composites at different strain rates

    KAUST Repository

    Yudhanto, Arief

    2016-03-08

    Impact copolymer polypropylene (IPP), a blend of isotactic polypropylene and ethylene-propylene rubber, and its continuous glass fiber composite form (glass fiber-reinforced impact polypropylene, GFIPP) are promising materials for impact-prone automotive structures. However, basic mechanical properties and corresponding damage of IPP and GFIPP at different rates, which are of keen interest in the material development stage and numerical tool validation, have not been reported. Here, we applied monotonic and cyclic tensile loads to IPP and GFIPP at different strain rates (0.001/s, 0.01/s and 0.1/s) to study the mechanical properties, failure modes and the damage parameters. We used monotonic and cyclic tests to obtain mechanical properties and define damage parameters, respectively. We also used scanning electron microscopy (SEM) images to visualize the failure mode. We found that IPP generally exhibits brittle fracture (with relatively low failure strain of 2.69-3.74%) and viscoelastic-viscoplastic behavior. GFIPP [90]8 is generally insensitive to strain rate due to localized damage initiation mostly in the matrix phase leading to catastrophic transverse failure. In contrast, GFIPP [±45]s is sensitive to the strain rate as indicated by the change in shear modulus, shear strength and failure mode.

  20. Stress transfer around a broken fiber in unidirectional fiber-reinforced composites considering matrix damage evolution and interface slipping

    Science.gov (United States)

    Yang, Zhong; Zhang, BoMing; Zhao, Lin; Sun, XinYang

    2011-02-01

    A shear-lag model is applied to study the stress transfer around a broken fiber within unidirectional fiber-reinforced composites (FRC) subjected to uniaxial tensile loading along the fiber direction. The matrix damage and interfacial debonding, which are the main failure modes, are considered in the model. The maximum stress criterion with the linear damage evolution theory is used for the matrix. The slipping friction stress is considered in the interfacial debonding region using Coulomb friction theory, in which interfacial clamping stress comes from radial residual stress and mismatch of Poisson's ratios of constituents (fiber and matrix). The stress distributions in the fiber and matrix are obtained by the shear-lag theory added with boundary conditions, which includes force continuity and displacement compatibility constraints in the broken and neighboring intact fibers. The result gives axial stress distribution in fibers and shear stress in the interface and compares the theory reasonably well with the measurement by a polarized light microscope. The relation curves between damage, debonding and ineffective region lengths with external strain loading are obtained.

  1. Numerical simulating and experimental study on the woven carbon fiber-reinforced composite laminates under low-velocity impact

    Science.gov (United States)

    Liu, Hanyang; Tang, Zhanwen; Pan, Lingying; Zhao, Weidong; Sun, Baogang; Jiang, Wenge

    2016-05-01

    Impact damage has been identified as a critical form of the defects that constantly threatened the reliability of composite structures, such as those used in the aerospace structures and systems. Low energy impacts can introduce barely visible damage and cause the degradation of structural stiffness, furthermore, the flaws caused by low-velocity impact are so dangerous that they can give rise to the further extended delaminations. In order to improve the reliability and load carrying capacity of composite laminates under low-velocity impact, in this paper, the numerical simulatings and experimental studies on the woven fiber-reinforced composite laminates under low-velocity impact with impact energy 16.7J were discussed. The low velocity impact experiment was carried out through drop-weight system as the reason of inertia effect. A numerical progressive damage model was provided, in which the damages of fiber, matrix and interlamina were considered by VUMT subroutine in ABAQUS, to determine the damage modes. The Hashin failure criteria were improved to cover the failure modes of fiber failure in the directions of warp/weft and delaminations. The results of Finite Element Analysis (FEA) were compared with the experimental results of nondestructive examination including the results of ultrasonic C-scan, cross-section stereomicroscope and contact force - time history curves. It is found that the response of laminates under low-velocity impact could be divided into stages with different damage. Before the max-deformation of the laminates occurring, the matrix cracking, fiber breakage and delaminations were simulated during the impactor dropping. During the releasing and rebounding period, matrix cracking and delaminations areas kept increasing in the laminates because of the stress releasing of laminates. Finally, the simulating results showed the good agreements with the results of experiment.

  2. Effects of High-Temperature Annealing in Air on Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites

    Science.gov (United States)

    Bansal, Narottam P.

    2008-01-01

    BN/SiC-coated Hi-Nicalon fiber-reinforced celsian matrix composites (CMC) were annealed for 100 h in air at various temperatures to 1200 C, followed by flexural strength measurements at room temperature. Values of yield stress and strain, ultimate strength, and composite modulus remain almost unchanged for samples annealed up to 1100 C. A thin porous layer formed on the surface of the 1100 C annealed sample and its density decreased from 3.09 to 2.90 g/cu cm. The specimen annealed at 1200 C gained 0.43 wt%, was severely deformed, and was covered with a porous layer of thick shiny glaze which could be easily peeled off. Some gas bubbles were also present on the surface. This surface layer consisted of elongated crystals of monoclinic celsian and some amorphous phase(s). The fibers in this surface ply of the CMC had broken into small pieces. The fiber-matrix interface strength was characterized through fiber push-in technique. Values of debond stress, alpha(sub d), and frictional sliding stress, tau(sub f), for the as-fabricated CMC were 0.31+/-0.14 GPa and 10.4+/-3.1 MPa, respectively. These values compared with 0.53+/-0.47 GPa and 8.33+/-1.72 MPa for the fibers in the interior of the 1200 C annealed sample, indicating hardly any change in fiber-matrix interface strength. The effects of thermal aging on microstructure were investigated using scanning electron microscopy. Only the surface ply of the 1200 C annealed specimens had degraded from oxidation whereas the bulk interior part of the CMC was unaffected. A mechanism is proposed explaining the various steps involved during the degradation of the CMC on annealing in air at 1200 C.

  3. In vitro evaluation of fracture resistance of Fiber-Reinforced Composite inlay bridges in upper anterior and lower posterior teeth

    Directory of Open Access Journals (Sweden)

    Jalalian E.

    2007-07-01

    Full Text Available Background and Aim: Considering flexural strength of fiber-reinforced composites (FRC and also the role of conservative cavities in protecting sound tissue of abutments, the aim of this study was to evaluate the fracture resistance of these bridges by handmade samples in vitro.Materials and Methods: In this experimental in vitro study, 44 sound newly extracted teeth were used to make 22 fixed inlay bridges including 11 three unit anterior upper inlay bridges substituting clinical model of upper central and 11 three unit posterior lower inlay bridges substituting clinical model of lower first molar. Specimens were prepared with FRC and mounted with artificial PDL in acryl. Cases were exposed to final load by using Universal Testing Machine (Instron 1195 with the speed of 1 mm/min. Statistical analysis was performed by Kolmogorov- Smirnov, independent sample T and Kaplan-Meier tests with p<0.05 as the level of significance.Results: Based on the statistical tests, the 95% confidence interval of mean was 450-562 N in anterior and  1473- 1761 N in posterior area. Fracture strength was high in the studied groups. Fractures in both groups occurred on composite facing, and the framework remained intact. The highest percentage of fracture in posterior teeth was in the middle of pontic towards the distal connector and in the anterior teeth in the lateral connector, between central pontic and lateral abutment. Using the independent sample T  test a significant statistical difference was observed between two groups (P<0.001. The fracture resistance of anterior samples was lower than the posterior ones.Conclusion: Based on the results of this study regarding the high fracture resistance in both areas FRC inlay bridges could be recommended for upper anterior and lower posterior teeth in clinical dentistry certainly more studies are needed to ascertain this treatment option.

  4. A Fully Contained Resin Infusion Process for Fiber-Reinforced Polymer Composite Fabrication and Repair

    Science.gov (United States)

    2013-01-01

    Figures iv  Acknowledgments v  1.  Introduction 1  2.  Experimental 2  2.1  Composite Laminate Fabrication...2 Figure 2. Image of fiberglass composite being fabricated using VARTM processing. 2. Experimental 2.1 Composite Laminate Fabrication...style 5 × 5 plain 5 weave prepreg S-2 fiberglass fabric and a honeycomb core cured in an autoclave, much like the composite parts fielded in

  5. Two-year survival analysis of twisted wire fixed retainer versus spiral wire and fiber-reinforced composite retainers: a preliminary explorative single-blind randomized clinical trial.

    Science.gov (United States)

    Sobouti, Farhad; Rakhshan, Vahid; Saravi, Mahdi Gholamrezaei; Zamanian, Ali; Shariati, Mahsa

    2016-03-01

    Traditional retainers (both metal and fiber-reinforced composite [FRC]) have limitations, and a retainer made from more flexible ligature wires might be advantageous. We aimed to compare an experimental design with two traditional retainers. In this prospective preliminary clinical trial, 150 post-treatment patients were enrolled and randomly divided into three groups of 50 patients each to receive mandibular canine-to-canine retainers made of FRC, flexible spiral wire (FSW), and twisted wire (TW). The patients were monitored monthly. The time at which the first signs of breakage/debonding were detected was recorded. The success rates of the retainers were compared using chi-squared, Kaplan-Meier, and Cox proportional-hazard regression analyses (α = 0.05). In total, 42 patients in the FRC group, 41 in the FSW group, and 45 in the TW group completed the study. The 2-year failure rates were 35.7% in the FRC group, 26.8% in the FSW group, and 17.8% in the TW group. These rates differed insignificantly (chi-squared p = 0.167). According to the Kaplan-Meier analysis, failure occurred at 19.95 months in the FRC group, 21.37 months in the FSW group, and 22.36 months in the TW group. The differences between the survival rates in the three groups were not significant (Cox regression p = 0.146). Although the failure rate of the experimental retainer was two times lower than that of the FRC retainer, the difference was not statistically significant. The experimental TW retainer was successful, and larger studies are warranted to verify these results.

  6. Effect of Multiwalled Carbon Nanotubes on the Mechanical Properties of Carbon Fiber-Reinforced Polyamide-6/Polypropylene Composites for Lightweight Automotive Parts

    Directory of Open Access Journals (Sweden)

    Huu-Duc Nguyen-Tran

    2018-03-01

    Full Text Available The development of lightweight automotive parts is an important issue for improving the efficiency of vehicles. Polymer composites have been widely applied to reduce weight and improve mechanical properties by mixing polymers with carbon fibers, glass fibers, and carbon nanotubes. Polypropylene (PP has been added to carbon fiber-reinforced nylon-6 (CF/PA6 composite to achieve further weight reduction and water resistance. However, the mechanical properties were reduced by the addition of PP. In this research, multiwalled carbon nanotubes (CNTs were added to compensate for the reduced mechanical properties experienced when adding PP. Tensile testing and bending tests were carried out to evaluate the mechanical properties. A small amount of CNTs improved the mechanical properties of carbon fiber-reinforced PA6/PP composites. For example, the density of CF/PA6 was reduced from 1.214 to 1.131 g/cm3 (6.8% by adding 30 wt % PP, and the tensile strength of 30 wt % PP composite was improved from 168 to 173 MPa (3.0% by adding 0.5 wt % CNTs with small increase of density (1.135 g/cm3. The developed composite will be widely used for lightweight automotive parts with improved mechanical properties.

  7. Water absorption and tensile strength degradation of Petung bamboo (Dendrocalamus asper) fiber-reinforced polymeric composites

    NARCIS (Netherlands)

    Judawisastra, H.; Sitohang, Ramona; Rosadi, M. S.

    2017-01-01

    Bamboo fibers have attracted great interest and are believed to have the potential as natural fiber for reinforcing polymer composites. This research aims to study water absorption behavior and its effect to tensile strength of the composites made from petung bamboo fiber, which is one of the most

  8. Polymer matrix of fiber-reinforced composites: Changes in the semi-interpenetrating polymer network during the shelf life.

    Science.gov (United States)

    Khan, Aftab A; Al-Kheraif, Abdulaziz A; Al-Shehri, Abdullah M; Säilynoja, Eija; Vallittu, Pekka K

    2018-02-01

    This laboratory study was aimed to characterize semi-interpenetrating polymer network (semi-IPN) of fiber-reinforced composite (FRC) prepregs that had been stored for up to two years before curing. Resin impregnated prepregs of everStick C&B (StickTech-GC, Turku, Finland) glass FRC were stored at 4°C for various lengths of time, i.e., two-weeks, 6-months and 2-years. Five samples from each time group were prepared with a light initiated free radical polymerization method, which were embedded to its long axis in self-curing acrylic. The nanoindentation readings on the top surface toward the core of the sample were made for five test groups, which were named as "stage 1-5". To evaluate the nanohardness and modulus of elasticity of the polymer matrix, a total of 4 slices (100µm each) were cut from stage 1 to stage 5. Differences in nanohardness values were evaluated with analysis of variance (ANOVA), and regression model was used to develop contributing effect of the material's different stages to the total variability in the nanomechanical properties. Additional chemical and thermal characterization of the polymer matrix structure of FRC was carried out. It was hypothesized that time of storage may have an influence on the semi-IPN polymer structure of the cured FRC. The two-way ANOVA test revealed that the storage time had no significant effect on the nanohardness of FRC (p = 0.374). However, a highly significant difference in nanohardness values was observed between the different stages of FRC (Pprepregs might be due to phase-segregation of components of semi-IPN structure of FRC prepregs before their use. This may have an influence to the surface bonding properties of the cured FRC. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Active constrained layer damping of geometrically nonlinear vibrations of functionally graded plates using piezoelectric fiber-reinforced composites

    International Nuclear Information System (INIS)

    Panda, Satyajit; Ray, M C

    2008-01-01

    In this paper, a geometrically nonlinear dynamic analysis has been presented for functionally graded (FG) plates integrated with a patch of active constrained layer damping (ACLD) treatment and subjected to a temperature field. The constraining layer of the ACLD treatment is considered to be made of the piezoelectric fiber-reinforced composite (PFRC) material. The temperature field is assumed to be spatially uniform over the substrate plate surfaces and varied through the thickness of the host FG plates. The temperature-dependent material properties of the FG substrate plates are assumed to be graded in the thickness direction of the plates according to a power-law distribution while the Poisson's ratio is assumed to be a constant over the domain of the plate. The constrained viscoelastic layer of the ACLD treatment is modeled using the Golla–Hughes–McTavish (GHM) method. Based on the first-order shear deformation theory, a three-dimensional finite element model has been developed to model the open-loop and closed-loop nonlinear dynamics of the overall FG substrate plates under the thermal environment. The analysis suggests the potential use of the ACLD treatment with its constraining layer made of the PFRC material for active control of geometrically nonlinear vibrations of FG plates in the absence or the presence of the temperature gradient across the thickness of the plates. It is found that the ACLD treatment is more effective in controlling the geometrically nonlinear vibrations of FG plates than in controlling their linear vibrations. The analysis also reveals that the ACLD patch is more effective for controlling the nonlinear vibrations of FG plates when it is attached to the softest surface of the FG plates than when it is bonded to the stiffest surface of the plates. The effect of piezoelectric fiber orientation in the active constraining PFRC layer on the damping characteristics of the overall FG plates is also discussed

  10. Active constrained layer damping of geometrically nonlinear vibrations of functionally graded plates using piezoelectric fiber-reinforced composites

    Science.gov (United States)

    Panda, Satyajit; Ray, M. C.

    2008-04-01

    In this paper, a geometrically nonlinear dynamic analysis has been presented for functionally graded (FG) plates integrated with a patch of active constrained layer damping (ACLD) treatment and subjected to a temperature field. The constraining layer of the ACLD treatment is considered to be made of the piezoelectric fiber-reinforced composite (PFRC) material. The temperature field is assumed to be spatially uniform over the substrate plate surfaces and varied through the thickness of the host FG plates. The temperature-dependent material properties of the FG substrate plates are assumed to be graded in the thickness direction of the plates according to a power-law distribution while the Poisson's ratio is assumed to be a constant over the domain of the plate. The constrained viscoelastic layer of the ACLD treatment is modeled using the Golla-Hughes-McTavish (GHM) method. Based on the first-order shear deformation theory, a three-dimensional finite element model has been developed to model the open-loop and closed-loop nonlinear dynamics of the overall FG substrate plates under the thermal environment. The analysis suggests the potential use of the ACLD treatment with its constraining layer made of the PFRC material for active control of geometrically nonlinear vibrations of FG plates in the absence or the presence of the temperature gradient across the thickness of the plates. It is found that the ACLD treatment is more effective in controlling the geometrically nonlinear vibrations of FG plates than in controlling their linear vibrations. The analysis also reveals that the ACLD patch is more effective for controlling the nonlinear vibrations of FG plates when it is attached to the softest surface of the FG plates than when it is bonded to the stiffest surface of the plates. The effect of piezoelectric fiber orientation in the active constraining PFRC layer on the damping characteristics of the overall FG plates is also discussed.

  11. Effect of implant design and bioactive glass coating on biomechanical properties of fiber-reinforced composite implants.

    Science.gov (United States)

    Ballo, Ahmed M; Akca, Eralp; Ozen, Tuncer; Moritz, Niko; Lassila, Lippo; Vallittu, Pekka; Närhi, Timo

    2014-08-01

    This study aimed to evaluate the influence of implant design and bioactive glass (BAG) coating on the response of bone to fiber-reinforced composite (FRC) implants. Three different FRC implant types were manufactured for the study: non-threaded implants with a BAG coating; threaded implants with a BAG coating; and threaded implants with a grit-blasted surface. Thirty-six implants (six implants for each group per time point) were installed in the tibiae of six pigs. After an implantation period of 4 and 12 wk, the implants were retrieved and prepared for micro-computed tomography (micro-CT), push-out testing, and scanning electron microscopy analysis. Micro-CT demonstrated that the screw-threads and implant structure remained undamaged during the installation. The threaded FRC/BAG implants had the highest bone volume after 12 wk of implantation. The push-out strengths of the threaded FRC/BAG implants after 4 and 12 wk (463°N and 676°N, respectively) were significantly higher than those of the threaded FRC implants (416°N and 549°N, respectively) and the nonthreaded FRC/BAG implants (219°N and 430°N, respectively). Statistically significant correlation was found between bone volume and push-out strength values. This study showed that osseointegrated FRC implants can withstand the static loading up to failure without fracture, and that the addition of BAG significantly improves the push-out strength of FRC implants. © 2014 Eur J Oral Sci.

  12. Natural Mallow Fiber-Reinforced Epoxy Composite for Ballistic Armor Against Class III-A Ammunition

    Science.gov (United States)

    Nascimento, Lucio Fabio Cassiano; Holanda, Luane Isquerdo Ferreira; Louro, Luis Henrique Leme; Monteiro, Sergio Neves; Gomes, Alaelson Vieira; Lima, Édio Pereira

    2017-10-01

    Epoxy matrix composites reinforced with up to 30 vol pct of continuous and aligned natural mallow fibers were for the first time ballistic tested as personal armor against class III-A 9 mm FMJ ammunition. The ballistic efficiency of these composites was assessed by measuring the dissipated energy and residual velocity after the bullet perforation. The results were compared to those in similar tests of aramid fabric (Kevlar™) commonly used in vests for personal protections. Visual inspection and scanning electron microscopy analysis of impact-fractured samples revealed failure mechanisms associated with fiber pullout and rupture as well as epoxy cracking. As compared to Kevlar™, the mallow fiber composite displayed practically the same ballistic efficiency. However, there is a reduction in both weight and cost, which makes the mallow fiber composites a promising material for personal ballistic protection.

  13. Conduction noise absorption by fiber-reinforced epoxy composites with carbon nanotubes

    International Nuclear Information System (INIS)

    Lee, Ok Hyoung; Kim, Sung-Soo; Lim, Yun-Soo

    2011-01-01

    Nearly all electronic equipment is susceptible to malfunction as a result of electromagnetic interference. In this study, glass fiber, and carbon fiber as a type reinforcement and epoxy as a matrix material were used to fabricate composite materials. In an attempt to increase the conduction noise absorption, carbon nanotubes were grown on the surface of glass fibers and carbon fibers. A microstrip line with characteristic impedance of 50 Ω in connection with network analyzer was used to measure the conduction noise absorption. In comparing a glass fiber/epoxy composite with a GF-CNT/Ep composite, it was demonstrated that the CNTs significantly influence the noise absorption property mainly due to increase in electric conductivity. In the carbon fiber composites, however, the effectiveness of CNTs on the degree of electric conductivity is negligible, resulting in a small change in reflection and transmission of an electromagnetic wave. - Research Highlights: → In this study, glass fiber and carbon fiber as a type reinforcement and epoxy as a matrix material were used to fabricate composite materials. In an attempt to increase the conduction noise absorption, carbon nanotubes (CNTs) were grown on the surface of glass fibers and carbon fibers. A microstrip line with characteristic impedance of 50 Ω in connection with network analyzer was used to measure the conduction noise absorption. → In comparing a glass fiber/epoxy composite with a GF-CNT/Ep composite, it was demonstrated that the CNTs significantly influence the noise absorption property mainly due to increase in electric conductivity. In the carbon fiber composites, however, the effectiveness of CNTs on the degree of electric conductivity is negligible, resulting in a small change in reflection and transmission of an electromagnetic wave.

  14. Mechanical and physical properties of wood fiber-reinforced, sulfur-based wood composites

    Science.gov (United States)

    Chung-Yun Hse; Ben S. Bryant

    1993-01-01

    Sulfur-based composite was made from sulfur impregnated, oven dried, wet-formed fiber mats. The fiber mats consisted of a 50/50 mixture of recycled newsprint pulp and mechanical hardwood pulp from several species made from chips in a laboratory refiner. The thickness of the composites was 0.125 inch and the specific gravity of the unimpregnated fiber mat was 0.2. The...

  15. Thermal Protection of Carbon Fiber-Reinforced Composites by Ceramic Particles

    Directory of Open Access Journals (Sweden)

    Baljinder Kandola

    2016-06-01

    Full Text Available The thermal barrier efficiency of two types of ceramic particle, glass flakes and aluminum titanate, dispersed on the surface of carbon-fiber epoxy composites, has been evaluated using a cone calorimeter at 35 and 50 kW/m2, in addition to temperature gradients through the samples’ thicknesses, measured by inserting thermocouples on the exposed and back surfaces during the cone tests. Two techniques of dispersing ceramic particles on the surface have been employed, one where particles were dispersed on semi-cured laminate and the other where their dispersion in a phenolic resin was applied on the laminate surface, using the same method as used previously for glass fiber composites. The morphology and durability of the coatings to water absorption, peeling, impact and flexural tension were also studied and compared with those previously reported for glass-fiber epoxy composites. With both methods, uniform coatings could be achieved, which were durable to peeling or water absorption with a minimal adverse effect on the mechanical properties of composites. While all these properties were comparable to those previously observed for glass fiber composites, the ceramic particles have seen to be more effective on this less flammable, carbon fiber composite substrate.

  16. Annealing effects of carbon fiber-reinforced epoxy resin composites irradiated by electron beams

    International Nuclear Information System (INIS)

    Udagawa, Akira; Sasuga, Tuneo; Ito, Hiroshi; Hagiwara, Miyuki

    1987-01-01

    Carbon cloth-reinforced epoxy resin composites were irradiated with 2 MeV electrons at room temperature and then annealed in air for 2 h at temperatures up to 180 deg C. A considerable decrease in the three-point bending strength occurred when the irradiated composites were annealed in the temperature range of 115 - 135 deg C which is below the glass transition temperature T g of the matrix resin, while the bending strength remained unchanged up to 180 deg C for the unirradiated composites. In the dynamic viscoelastic spectra of the irradiated matrix, a new relaxation appeared at the temperature extending from 50 deg C to just below the matrix T g and disappeared on annealing for 2 h at 135 deg C. Annealing also decreased the concentration of free radicals existing stably in the irradiated matrix at room temperature. After annealing, a large amount of clacks and voids were observed in the fractography of the composites by scanning electron microscopy. These results indicate: (1) Annealing brings about rearrangement of the radiation-induced molecular chain scission in the matrix; (2) The bending strength of the irradiated composites decreased owing to the increased brittleness of the matrix by annealing. (author)

  17. Mallow Fiber-Reinforced Epoxy Composites in Multilayered Armor for Personal Ballistic Protection

    Science.gov (United States)

    Nascimento, Lucio Fábio Cassiano; Louro, Luis Henrique Leme; Monteiro, Sergio Neves; Lima, Édio Pereira; da Luz, Fernanda Santos

    2017-10-01

    Lighter and less expensive polymer composites reinforced with natural fibers have been investigated as possible components of a multilayered armor system (MAS) for personal protection against high-velocity ammunition. Their ballistic performance was consistently found comparable with that of conventional Kevlar® synthetic aramid fiber. Among the numerous existing natural fibers with the potential for reinforcing polymer composites to replace Kevlar® in MAS, mallow fiber has not been fully investigated. Thus, the objective of this work is to evaluate the ballistic performance of epoxy composites reinforced with 30 vol.% of aligned mallow fibers as a second MAS layer backing a front ceramic plate. The results using high-velocity 7.62 ammunition show a similar indentation to a Kevlar® layer with the same thickness. An impedance matching calculation supports the similar ballistic performance of mallow fiber composite and Kevlar®. Reduced MAS costs associated with the mallow fiber composite are practical advantages over Kevlar®.

  18. A novel basalt fiber-reinforced polylactic acid composite for hard tissue repair.

    Science.gov (United States)

    Chen, Xi; Li, Yan; Gu, Ning

    2010-08-01

    A basalt fiber (BF) was, for the first time, introduced into a poly(l-lactic acid) (PLLA) matrix as innovative reinforcement to fabricate composite materials for hard tissue repair. Firstly, BF/PLLA composites and pure PLLA were produced by the methods of solution blending and freeze drying. The results showed that basalt fibers can be uniformly dispersed in the PLLA matrix and significantly improve the mechanical properties and hydrophilicity of the PLLA matrix. The presence of basalt fibers may retard the polymer degradation rate and neutralize the acid degradation from PLLA. Osteoblasts were cultured in vitro to evaluate the cytocompatibility of the composite. An MTT assay revealed that osteoblasts proliferated well for 7 days and there was little difference found in their viability on both PLLA and BF/PLLA films, which was consistent with the alkaline phosphatase (ALP) activity results. A fluorescent staining observation showed that osteoblasts grew well on the composites. SEM images displayed that osteoblasts tended to grow along the fiber axis. The formation of mineralized nodules was observed on the films by Alizarin red S staining. These results suggest that the presence of basalt fibers does not noticeably affect osteoblastic behavior and the designed composites are osteoblast compatible. It is concluded that basalt fibers, as reinforcing fibers, may have promising applications in hard tissue repair.

  19. A novel basalt fiber-reinforced polylactic acid composite for hard tissue repair

    International Nuclear Information System (INIS)

    Chen Xi; Li Yan; Gu Ning

    2010-01-01

    A basalt fiber (BF) was, for the first time, introduced into a poly(l-lactic acid) (PLLA) matrix as innovative reinforcement to fabricate composite materials for hard tissue repair. Firstly, BF/PLLA composites and pure PLLA were produced by the methods of solution blending and freeze drying. The results showed that basalt fibers can be uniformly dispersed in the PLLA matrix and significantly improve the mechanical properties and hydrophilicity of the PLLA matrix. The presence of basalt fibers may retard the polymer degradation rate and neutralize the acid degradation from PLLA. Osteoblasts were cultured in vitro to evaluate the cytocompatibility of the composite. An MTT assay revealed that osteoblasts proliferated well for 7 days and there was little difference found in their viability on both PLLA and BF/PLLA films, which was consistent with the alkaline phosphatase (ALP) activity results. A fluorescent staining observation showed that osteoblasts grew well on the composites. SEM images displayed that osteoblasts tended to grow along the fiber axis. The formation of mineralized nodules was observed on the films by Alizarin red S staining. These results suggest that the presence of basalt fibers does not noticeably affect osteoblastic behavior and the designed composites are osteoblast compatible. It is concluded that basalt fibers, as reinforcing fibers, may have promising applications in hard tissue repair.

  20. Porosity characterization of fiber-reinforced ceramic matrix composite using synchrotron X-ray computed tomography

    International Nuclear Information System (INIS)

    Zou, C.; Li, B.; Zhang, C.; Wang, S.; Marrow, T.J.; Reinhard, C.

    2016-01-01

    The pore structure and porosity of a continuous fiber reinforced ceramic matrix composite has been characterized using high-resolution synchrotron X-ray computed tomography (XCT). Segmentation of the reconstructed tomograph images reveals different types of pores within the composite, the inter-fiber bundle open pores displaying a 'node-bond' geometry, and the intra-fiber bundle isolated micropores showing a piping shape. The 3D morphology of the pores is resolved and each pore is labeled. The quantitative filtering of the pores measures a total porosity 8.9% for the composite, amid which there is about 7.1∼ 9.3% closed micropores

  1. Dynamic and Capillary Shear Rheology of Natural Fiber-Reinforced Composites

    NARCIS (Netherlands)

    Moigne, Le N.; Oever, van den M.J.A.; Budtova, T.

    2013-01-01

    An extended dynamic and capillary rheological study of molten flax and sisal polypropylene (PP) composites was performed. Fiber concentration varied from 20 to 50 wt% and shear rate from 0.1 rad s−1 to 10,000 s#142;−1. Maleic anhydride-grafted-PP was used as compatibilizer; it strongly reduces PP

  2. Ceramic fiber-reinforced monoclinic celsian phase glass-ceramic matrix composite material

    Science.gov (United States)

    Bansal, Narottam P. (Inventor); Dicarlo, James A. (Inventor)

    1994-01-01

    A hyridopolysilazane-derived ceramic fiber reinforced monoclinic celsian phase barium aluminum silicate glass-ceramic matrix composite material is prepared by ball-milling an aqueous slurry of BAS glass powder and fine monoclinic celsian seeds. The fibers improve the mechanical strength and fracture toughness and with the matrix provide superior dielectric properties.

  3. The Impact Resistance of Fiber-Reinforced Polymer Composites: A Review

    Directory of Open Access Journals (Sweden)

    Mahmood Mehrdad Shokrieh

    2012-12-01

    Full Text Available Fiber reinforced composites are widely used instead of traditional materials in various technological applications. Therefore, by considering the extensive applications of these materials, a proper knowledge of their impact behavior (from low- to high-velocity as well as their static behavior is necessary. In order to study the effects of strain rates on the behavior of these materials, special testing machines are needed. Most of the research efforts in this feld are focused on application of real loading and gripping boundary conditions on the testing specimens. In this paper, a detailed review of different types of impact testing techniques and the strain rate dependence of mechanical and strength properties of polymer composite materials  are presented. In this respect, an attempt is made to present and summarize the methods of impact tests and the strain rate effects on the tensile, compressive, shear and bending properties of the fber-reinforced polymer composite materials. Moreover, a classifcation of the state-of-the-art of the testing techniques to characterize composite material properties in a wide range of strain rates are also given.

  4. The Impact Resistance of Fiber-Reinforced Polymer Composites: A Review

    OpenAIRE

    Mahmood Mehrdad Shokrieh; Majid Jamal Omidi

    2012-01-01

    Fiber reinforced composites are widely used instead of traditional materials in various technological applications. Therefore, by considering the extensive applications of these materials, a proper knowledge of their impact behavior (from low- to high-velocity) as well as their static behavior is necessary. In order to study the effects of strain rates on the behavior of these materials, special testing machines are needed. Most of the research efforts in this feld are focused on application ...

  5. Numerical approach of the injection molding process of fiber-reinforced composite with considering fiber orientation

    Science.gov (United States)

    Nguyen Thi, T. B.; Yokoyama, A.; Ota, K.; Kodama, K.; Yamashita, K.; Isogai, Y.; Furuichi, K.; Nonomura, C.

    2014-05-01

    One of the most important challenges in the injection molding process of the short-glass fiber/thermoplastic composite parts is being able to predict the fiber orientation, since it controls the mechanical and the physical properties of the final parts. Folgar and Tucker included into the Jeffery equation a diffusive type of term, which introduces a phenomenological coefficient for modeling the randomizing effect of the mechanical interactions between the fibers, to predict the fiber orientation in concentrated suspensions. Their experiments indicated that this coefficient depends on the fiber volume fraction and aspect ratio. However, a definition of the fiber interaction coefficient, which is very necessary in the fiber orientation simulations, hasn't still been proven yet. Consequently, this study proposed a developed fiber interaction model that has been introduced a fiber dynamics simulation in order to obtain a global fiber interaction coefficient. This supposed that the coefficient is a sum function of the fiber concentration, aspect ratio, and angular velocity. The proposed model was incorporated into a computer aided engineering simulation package C-Mold. Short-glass fiber/polyamide-6 composites were produced in the injection molding with the fiber weight concentration of 30 wt.%, 50 wt.%, and 70 wt.%. The physical properties of these composites were examined, and their fiber orientation distributions were measured by micro-computed-tomography equipment μ-CT. The simulation results showed a good agreement with experiment results.

  6. An overview of development and status of fiber-reinforced composites as dental and medical biomaterials.

    Science.gov (United States)

    Vallittu, Pekka K

    2018-01-01

    Fibr-reinforced composites (FRC) have been used successfully for decades in many fields of science and engineering applications. Benefits of FRCs relate to physical properties of FRCs and versatile production methods, which can be utilized. Conventional hand lamination of prefabricated FRC prepregs is utilized still most commonly in fabrication of dental FRC devices but CAD-CAM systems are to be come for use in certain production steps of dental constructions and medical FRC implants. Although metals, ceramics and particulate filler resin composites have successfully been used as dental and medical biomaterials for decades, devices made out of these materials do not meet all clinical requirements. Only little attention has been paid to FRCs as dental materials and majority of the research in dental field has been focusing on particulate filler resin composites and in medical biomaterial research to biodegradable polymers. This is paradoxical because FRCs can potentially resolve many of the problems related to traditional isotropic dental and medical materials. This overview reviews the rationale and status of using biostable glass FRC in applications from restorative and prosthetic dentistry to cranial surgery. The overview highlights also the critical material based factors and clinical requirement for the succesfull use of FRCs in dental reconstructions.

  7. Mechanics of Unidirectional Fiber-Reinforced Composites: Buckling Modes and Failure Under Compression Along Fibers

    Science.gov (United States)

    Paimushin, V. N.; Kholmogorov, S. A.; Gazizullin, R. K.

    2018-01-01

    One-dimensional linearized problems on the possible buckling modes of an internal or peripheral layer of unidirectional multilayer composites with rectilinear fibers under compression in the fiber direction are considered. The investigations are carried out using the known Kirchhoff-Love and Timoshenko models for the layers. The binder, modeled as an elastic foundation, is described by the equations of elasticity theory, which are simplified in accordance to the model of a transversely soft layer and are integrated along the transverse coordinate considering the kinematic coupling relations for a layer and foundation layers. Exact analytical solutions of the problems formulated are found, which are used to calculate a composite made of an HSE 180 REM prepreg based on a unidirectional carbon fiber tape. The possible buckling modes of its internal and peripheral layers are identified. Calculation results are compared with experimental data obtained earlier. It is concluded that, for the composite studied, the flexural buckling of layers in the uniform axial compression of specimens along fibers is impossible — the failure mechanism is delamination with buckling of a fiber bundle according to the pure shear mode. It is realized (due to the low average transverse shear modulus) at the value of the ultimate compression stress equal to the average shear modulus. It is shown that such a shear buckling mode can be identified only on the basis of equations constructed using the Timoshenko shear model to describe the deformation process of layers.

  8. Scattering of Lamb waves by cracks in a composite graphite fiber-reinforced epoxy plate

    Science.gov (United States)

    Bratton, Robert; Datta, Subhendu K.; Shah, Arvind

    1990-01-01

    Recent investigations of space construction techniques have explored the used of composite materials in the construction of space stations and platforms. These composites offer superior strength to weight ratio and are thermally stable. For example, a composite material being considered is laminates of graphite fibers in an epoxy matrix. The overall effective elastic constants of such a medium can be calculated from fiber and matrix properties by using an effective modulus theory as shown in Datta, el. al. The investigation of propagation and scattering of elastic waves in composite materials is necessary in order to develop an ability to characterize cracks and predict the reliability of composite structures. The objective of this investigation is the characterization of a surface breaking crack by ultrasonic techniques. In particular, the use of Lamb waves for this purpose is studied here. The Lamb waves travel through the plate, encountering a crack, and scatter. Of interest is the modeling of the scattered wave in terms of the Lamb wave modes. The direct problem of propagation and scattering of Lamb waves by a surface breaking crack has been analyzed. This would permit an experimentalist to characterize the crack by comparing the measured response to the analytical model. The plate is assumed to be infinite in the x and y directions with a constant thickness in the z direction. The top and bottom surfaces are traction free. Solving the governing wave equations and using the stress-free boundary conditions results in the dispersion equation. This equation yields the guided modes in the homogeneous plate. The theoretical model is a hybrid method that combines analytical and finite elements techniques to describe the scattered displacements. A finite region containing the defects is discretized by finite elements. Outside the local region, the far field solution is expressed as a Fourier summation of the guided modes obtained from the dispersion equation

  9. A Constitutive Formulation for the Linear Thermoelastic Behavior of Arbitrary Fiber-Reinforced Composites

    Directory of Open Access Journals (Sweden)

    Melek Usal

    2010-01-01

    Full Text Available The linear thermoelastic behavior of a composite material reinforced by two independent and inextensible fiber families has been analyzed theoretically. The composite material is assumed to be anisotropic, compressible, dependent on temperature gradient, and showing linear elastic behavior. Basic principles and axioms of modern continuum mechanics and equations belonging to kinematics and deformation geometries of fibers have provided guidance and have been determining in the process of this study. The matrix material is supposed to be made of elastic material involving an artificial anisotropy due to fibers reinforcing by arbitrary distributions. As a result of thermodynamic constraints, it has been determined that the free energy function is dependent on a symmetric tensor and two vectors whereas the heat flux vector function is dependent on a symmetric tensor and three vectors. The free energy and heat flux vector functions have been represented by a power series expansion, and the type and the number of terms taken into consideration in this series expansion have determined the linearity of the medium. The linear constitutive equations of the stress and heat flux vector are substituted in the Cauchy equation of motion and in the equation of conservation of energy to obtain the field equations.

  10. Process for the manufacture of seamless metal-clad fiber-reinforced organic matrix composite structures

    Science.gov (United States)

    Bluck, Raymond M. (Inventor); Bush, Harold G. (Inventor); Johnson, Robert R. (Inventor)

    1991-01-01

    A process for producing seamless metal-clad composite structures includes providing a hollow, metallic inner member and an outer sleeve to surround the inner member and define an inner space therebetween. A plurality of continuous reinforcing fibers is attached to the distal end of the outside diameter of the inner member, and the inner member is then introduced, distal end first, into one end of the outer sleeve. The inner member is then moved, distal end first, into the outer sleeve until the inner member is completely enveloped by the outer sleeve. A liquid matrix material is then injected into the space containing the reinforcing fibers between the inner member and the outer sleeve. Next a pressurized heat transfer medium is passed through the inner member to cure the liquid matrix material. Finally, the wall thickness of both the inner member and the outer sleeve are reduced to desired dimensions by chemical etching, which adjusts the thermal expansion coefficient of the metal-clad composite structure to a desired value.

  11. RESIDUAL PROPERTIES OF FIBER-REINFORCED REFRACTORY COMPOSITES WITH A FIRECLAY FILLER

    Directory of Open Access Journals (Sweden)

    Marcel Jogl

    2016-02-01

    Full Text Available The aim of our study was to develop a composite material for industrial use that is resistant to the effect of high temperatures. The binder system based on aluminous cement was modified by adding finely-ground ceramic powder and metakaolin to reduce costs and also to reduce adverse effects on the environment due to high energy consumption for cement production. Additives were applied as a partial aluminous cement replacement in doses of 10, 20 and 30% by weight. The composites were evaluated on the basis of their mechanical properties and their bulk density after gradual temperature loading. The influence of basalt fibers and modifications to the binder system were studied at the same time. Basalt fibers were applied in doses of 0.5% and 2.0% by volume. The results confirmed the potential of the mineral additives studied here for practical applications, taking into account the residual mechanical parameters after thermal loading. The addition of ceramic powder reduced the bulk density by 5% for each 10% of cement substitution, but the residual values were very similar. The bulk density and the compressive strength were reduced when basalt fibers were applied, and the flexural strength was significantly increased in proportion to the fiber dosages. Metakaolin seems to be a more suitable additive than the ceramic powder that was applied here, because there was a significant increase in the mechanical parameters and also in the residual values of all properties that were studied.

  12. Fracture toughness of fiber-reinforced glass ceramic and ceramic matrix composites

    Science.gov (United States)

    Stull, Kevin R.; Parvizi-Majidi, A.

    1991-01-01

    A fracture mechanics investigation of 2D woven Nicalon SiC/SiC and Nicalon SiC/LAS has been undertaken. An energy approach has been adopted to characterize and quantify the fracture properties of these materials. Chevron-notched bend specimens were tested in an edgewise configuration in which the crack propagated perpendicular to the ply direction. R-curves were obtained from repeated loading and unloading of specimens using several methods of data reduction. Values correconding to the plateau regions of the R-curves were taken as steady-state crack-growth resistance. These ranged from 37 to 63 kJ/sq m for 2D-SiC/LAS and 2.6 to 2.8 kJ/sq m for 2D-SiC/SiC composites.

  13. Numerical Modeling of Fiber-Reinforced Metal Matrix Composite Processing by the Liquid Route: Literature Contribution

    Science.gov (United States)

    Lacoste, Eric; Arvieu, Corinne; Mantaux, Olivier

    2018-04-01

    One of the technologies used to produce metal matrix composites (MMCs) is liquid route processing. One solution is to inject a liquid metal under pressure or at constant rate through a fibrous preform. This foundry technique overcomes the problem of the wettability of ceramic fibers by liquid metal. The liquid route can also be used to produce semiproducts by coating a filament with a molten metal. These processes involve physical phenomena combined with mass and heat transfer and phase change. The phase change phenomena related to solidification and also to the melting of the metal during the process notably result in modifications to the permeability of porous media, in gaps in impregnation, in the appearance of defects (porosities), and in segregation in the final product. In this article, we provide a state-of-the-art review of numerical models and simulation developed to study these physical phenomena involved in MMC processing by the liquid route.

  14. Influence of Thin-Film Adhesives in Pullout Tests Between Nickel-Titanium Shape Memory Alloy and Carbon Fiber-Reinforced Polymer Matrix Composites

    Science.gov (United States)

    Quade, Derek J.; Jana, Sadhan; McCorkle, Linda S.

    2018-01-01

    Strips of nickel-titanium (NiTi) shape memory alloy (SMA) and carbon fiber-reinforced polymer matrix composite (PMC) were bonded together using multiple thin film adhesives and their mechanical strengths were evaluated under pullout test configuration. Tensile and lap shear tests were conducted to confirm the deformation of SMAs at room temperature and to evaluate the adhesive strength between the NiTi strips and the PMC. Optical and scanning electron microscopy techniques were used to examine the interfacial bonding after failure. Simple equations on composite tensile elongation were used to fit the experimental data on tensile properties. ABAQUS models were generated to show the effects of enhanced bond strength and the distribution of stress in SMA and PMC. The results revealed that the addition of thin film adhesives increased the average adhesive strength between SMA and PMC while halting the room temperature shape memory effect within the pullout specimen.

  15. Effect of Environment on Stress-Rupture Behavior of a Carbon Fiber-Reinforced Silicon Carbide (C/SiC) Ceramic Matrix Composite

    Science.gov (United States)

    Verrilli, Michael J.; Opila, Elizabeth J.; Calomino, Anthony; Kiser, J. Douglas

    2002-01-01

    Stress-rupture tests were conducted in air, vacuum, and steam-containing environments to identify the failure modes and degradation mechanisms of a carbon fiber-reinforced silicon carbide (C/SiC) composite at two temperatures, 600 and 1200 C. Stress-rupture lives in air and steam containing environments (50 - 80% steam with argon) are similar for a composite stress of 69 MPa at 1200 C. Lives of specimens tested in a 20% steam/argon environment were about twice as long. For tests conducted at 600 C, composite life in 20% steam/argon was 20 times longer than life in air. Thermogravimetric analysis of the carbon fibers was conducted under similar conditions to the stress-rupture tests. The oxidation rate of the fibers in the various environments correlated with the composite stress-rupture lives. Examination of the failed specimens indicated that oxidation of the carbon fibers was the primary damage mode for specimens tested in air and steam environments at both temperatures.

  16. Multi-Objective Patch Optimization with Integrated Kinematic Draping Simulation for Continuous–Discontinuous Fiber-Reinforced Composite Structures

    Directory of Open Access Journals (Sweden)

    Benedikt Fengler

    2018-03-01

    Full Text Available Discontinuous fiber-reinforced polymers (DiCoFRP in combination with local continuous fiber reinforced polymers (CoFRP provide both a high design freedom and high weight-specific mechanical properties. For the optimization of CoFRP patches on complexly shaped DiCoFRP structures, an optimization strategy is needed which considers manufacturing constraints during the optimization procedure. Therefore, a genetic algorithm is combined with a kinematic draping simulation. To determine the optimal patch position with regard to structural performance and overall material consumption, a multi-objective optimization strategy is used. The resulting Pareto front and a corresponding heat-map of the patch position are useful tools for the design engineer to choose the right amount of reinforcement. The proposed patch optimization procedure is applied to two example structures and the effect of different optimization setups is demonstrated.

  17. Modification of a Phenolic Resin with Epoxy- and Methacrylate-Functionalized Silica Sols to Improve the Ablation Resistance of Their Glass Fiber-Reinforced Composites

    Directory of Open Access Journals (Sweden)

    Yu Hu

    2014-01-01

    Full Text Available Functionalized silica sols were obtained by the hydrolytic condensation of (γ-methacryloxypropyltrimethoxysilane (MPMS, (γ-glycidyloxypropyltrimethoxysilane (GPMS and tetraethoxysilane (TEOS. Three different sols were obtained: MPS (derived from MPMS and TEOS, GPS-MPS (derived from GPMS, MPMS and TEOS, and GPSD (derived from GPMS, TEOS and diglycidyl ether of bisphenol A, DGEBA. These silica sols were mixed with a phenolic resin (PR. Ethylenediamine was used as a hardener for epoxy-functionalized sols and benzoyl peroxide was used as an initiator of the free-radical polymerization of methacrylate-functionalized silica sols. Glass fiber-reinforced composites were obtained from the neat PR and MPS-PR, GPS-MPS-PR and GPSD-PR. The resulting composites were evaluated as ablation resistant materials in an acetylene-oxygen flame. A large increase in the ablation resistance was observed when the PR was modified by the functionalized silica sols. The ablation resistance of the composites decreased as follows: GPSD-PR > MPS-PR > GPS-MPS-PR > PR.

  18. Effects of Fiber Content on Mechanical Properties of CVD SiC Fiber-Reinforced Strontium Aluminosilicate Glass-Ceramic Composites

    Science.gov (United States)

    Bansal, Narottam P.

    1996-01-01

    Unidirectional CVD SiC(f)(SCS-6) fiber-reinforced strontium aluminosilicate (SAS) glass-ceramic matrix composites containing various volume fractions, approximately 16 to 40 volume %, of fibers were fabricated by hot pressing at 1400 C for 2 h under 27.6 MPa. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase formed, with complete absence of the undesired hexacelsian phase, in the matrix. Room temperature mechanical properties were measured in 3-point flexure. The matrix microcracking stress and the ultimate strength increased with increase in fiber volume fraction, reached maximum values for V(sub f) approximately equal to 0.35, and degraded at higher fiber loadings. This degradation in mechanical properties is related to the change in failure mode, from tensile at lower V(sub f) to interlaminar shear at higher fiber contents. The extent of fiber loading did not have noticeable effect on either fiber-matrix debonding stress, or frictional sliding stress at the interface. The applicability of micromechanical models in predicting the mechanical properties of the composites was also examined. The currently available theoretical models do not appear to be useful in predicting the values of the first matrix cracking stress, and the ultimate strength of the SCS-6/SAS composites.

  19. A Novel CAE Method for Compression Molding Simulation of Carbon Fiber-Reinforced Thermoplastic Composite Sheet Materials

    Directory of Open Access Journals (Sweden)

    Yuyang Song

    2018-06-01

    Full Text Available Its high-specific strength and stiffness with lower cost make discontinuous fiber-reinforced thermoplastic (FRT materials an ideal choice for lightweight applications in the automotive industry. Compression molding is one of the preferred manufacturing processes for such materials as it offers the opportunity to maintain a longer fiber length and higher volume production. In the past, we have demonstrated that compression molding of FRT in bulk form can be simulated by treating melt flow as a continuum using the conservation of mass and momentum equations. However, the compression molding of such materials in sheet form using a similar approach does not work well. The assumption of melt flow as a continuum does not hold for such deformation processes. To address this challenge, we have developed a novel simulation approach. First, the draping of the sheet was simulated as a structural deformation using the explicit finite element approach. Next, the draped shape was compressed using fluid mechanics equations. The proposed method was verified by building a physical part and comparing the predicted fiber orientation and warpage measurements performed on the physical parts. The developed method and tools are expected to help in expediting the development of FRT parts, which will help achieve lightweight targets in the automotive industry.

  20. Use of the Materials Genome Initiative (MGI approach in the design of improved-performance fiber-reinforced SiC/SiC ceramic-matrix composites (CMCs

    Directory of Open Access Journals (Sweden)

    Jennifer S. Snipes

    2016-07-01

    Full Text Available New materials are traditionally developed using costly and time-consuming trial-and-error experimental efforts. This is followed by an even lengthier material-certification process. Consequently, it takes 10 to 20 years before a newly-discovered material is commercially employed. An alternative approach to the development of new materials is the so-called materials-by-design approach within which a material is treated as a complex hierarchical system, and its design and optimization is carried out by employing computer-aided engineering analyses, predictive tools and available material databases. In the present work, the materials-by-design approach is utilized to design a grade of fiber-reinforced (FR SiC/SiC ceramic matrix composites (CMCs, the type of materials which are currently being used in stationary components, and are considered for use in rotating components, of the hot sections of gas-turbine engines. Towards that end, a number of mathematical functions and numerical models are developed which relate CMC constituents’ (fibers, fiber coating and matrix microstructure and their properties to the properties and performance of the CMC as a whole. To validate the newly-developed materials-by-design approach, comparisons are made between experimentally measured and computationally predicted selected CMC mechanical properties. Then an optimization procedure is employed to determine the chemical makeup and processing routes for the CMC constituents so that the selected mechanical properties of the CMCs are increased to a preset target level.

  1. The bond of different post materials to a resin composite cement and a resin composite core material.

    Science.gov (United States)

    Stewardson, D; Shortall, A; Marquis, P

    2012-01-01

    To investigate the bond of endodontic post materials, with and without grit blasting, to a resin composite cement and a core material using push-out bond strength tests. Fiber-reinforced composite (FRC) posts containing carbon (C) or glass (A) fiber and a steel (S) post were cemented into cylinders of polymerized restorative composite without surface treatment (as controls) and after grit blasting for 8, 16, and 32 seconds. Additional steel post samples were sputter-coated with gold before cementation to prevent chemical interaction with the cement. Cylindrical composite cores were bonded to other samples. After sectioning into discs, bond strengths were determined using push-out testing. Profilometry and electron microscopy were used to assess the effect of grit blasting on surface topography. Mean (standard deviation) bond strength values (MPa) for untreated posts to resin cement were 8.41 (2.80) for C, 9.61(1.88) for A, and 19.90 (3.61) for S. Prolonged grit blasting increased bond strength for FRC posts but produced only a minimal increase for S. After 32 seconds, mean values were 20.65 (4.91) for C, 20.41 (2.93) for A, and 22.97 (2.87) for S. Gold-coated steel samples produced the lowest bond strength value, 7.84 (1.40). Mean bond strengths for untreated posts bonded to composite cores were 6.19 (0.95) for C, 13.22 (1.61) for A, and 8.82 (1.18) for S, and after 32 seconds of grit blasting the values were 17.30 (2.02) for C, 26.47 (3.09) for A, and 20.61 (2.67) for S. FRC materials recorded higher roughness values before and after grit blasting than S. With prolonged grit blasting, roughness increased for A and C, but not for S. There was no evidence of significant bonding to untreated FRC posts, but significant bonding occurred between untreated steel posts and the resin cement. Increases in the roughness of FRC samples were material dependent and roughening significantly increased bond strength values (p<0.05). Surface roughening of the tested FRC posts is

  2. Occupational exposures to styrene vapor in a manufacturing plant for fiber-reinforced composite wind turbine blades.

    Science.gov (United States)

    Hammond, Duane; Garcia, Alberto; Feng, H Amy

    2011-07-01

    A utility-scale wind turbine blade manufacturing plant requested assistance from the National Institute for Occupational Safety and Health (NIOSH) in controlling worker exposures to styrene at a plant that produced 37 and 42 m long fiber-reinforced wind turbine blades. The plant requested NIOSH assistance because previous air sampling conducted by the company indicated concerns about peak styrene concentrations when workers entered the confined space inside of the wind turbine blade. NIOSH researchers conducted two site visits and collected personal breathing zone and area air samples while workers performed the wind turbine blade manufacturing tasks of vacuum-assisted resin transfer molding (VARTM), gelcoating, glue wiping, and installing the safety platform. All samples were collected during the course of normal employee work activities and analyzed for styrene using NIOSH Method 1501. All sampling was task based since full-shift sampling from a prior Occupational Safety and Health Administration (OSHA) compliance inspection did not show any exposures to styrene above the OSHA permissible exposure limit. During the initial NIOSH site visit, 67 personal breathing zone and 18 area air samples were collected while workers performed tasks of VARTM, gelcoating, glue wipe, and installation of a safety platform. After the initial site visit, the company made changes to the glue wipe task that eliminated the need for workers to enter the confined space inside of the wind turbine blade. During the follow-up site visit, 12 personal breathing zone and 8 area air samples were collected from workers performing the modified glue wipe task. During the initial site visit, the geometric means of the personal breathing zone styrene air samples were 1.8 p.p.m. (n = 21) for workers performing the VARTM task, 68 p.p.m. (n = 5) for workers installing a safety platform, and 340 p.p.m. (n = 14) for workers performing the glue wipe task, where n is the number of workers sampled for a

  3. Interfacial Properties of Bamboo Fiber-Reinforced High-Density Polyethylene Composites by Different Methods for Adding Nano Calcium Carbonate

    Directory of Open Access Journals (Sweden)

    Cuicui Wang

    2017-11-01

    Full Text Available The focus of this study was to observe the effect of nano calcium carbonate (CaCO3 modification methods on bamboo fiber (BF used in BF-reinforced high-density polyethylene (HDPE composites manufactured by extrusion molding. Two methods were used to introduce the nano CaCO3 into the BF for modification; the first was blending modification (BM and the second was impregnation modification (IM. In order to determine the effects of the modification methods, the water absorption, surface free energy and interfacial properties of the unmodified composites were compared to those of the composites made from the two modification methods. The results revealed that the percentage increase in the weight of the composite treated by nano CaCO3 decreased and that of the IMBF/HDPE composite was the lowest over the seven months of time. The results obtained by the acid-base model according to the Lewis and Owens-Wendt- Rabel-Kaelble (OWRK equations indicated that the surface energy of the composites was between 40 and 50 mJ/m2. When compared to the control sample, the maximum storage modulus (E′max of the BMBF/HDPE and IMBF/HDPE composites increased 1.43- and 1.53-fold, respectively. The values of the phase-to-phase interaction parameter B and the k value of the modified composites were higher than those of the unmodified composites, while the apparent activation energy Ea and interface parameter A were lower in the modified composites. It can be concluded that nano CaCO3 had an effect on the interfacial properties of BF-reinforced HDPE composites, and the interface bonding between IMBF and HDPE was greatest among the composites.

  4. Oxidation effects on the mechanical properties of SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

    Science.gov (United States)

    Bhatt, Ramakrishna T.

    1989-01-01

    The room temperature mechanical properties of SiC fiber reinforced reaction bonded silicon nitride composites were measured after 100 hrs exposure at temperatures to 1400 C in nitrogen and oxygen environments. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers in a reaction bonded Si3N4 matrix. The results indicate that composites heat treated in a nitrogen environment at temperatures to 1400 C showed deformation and fracture behavior equivalent to that of the as-fabricated composites. Also, the composites heat treated in an oxidizing environment beyond 400 C yielded significantly lower tensile strength values. Specifically in the temperature range from 600 to 1000 C, composites retained approx. 40 percent of their as-fabricated strength, and those heat treated in the temperatures from 1200 to 1400 C retained 70 percent. Nonetheless, for all oxygen heat treatment conditions, composite specimens displayed strain capability beyond the matrix fracture stress; a typical behavior of a tough composite.

  5. Preparation and properties of banana fiber-reinforced composites based on high density polyethylene (HDPE)/Nylon-6 blends.

    Science.gov (United States)

    Liu, H; Wu, Q; Zhang, Q

    2009-12-01

    Banana fiber (BaF)-filled composites based on high density polyethylene (HDPE)/Nylon-6 blends were prepared via a two-step extrusion method. Maleic anhydride grafted styrene/ethylene-butylene/styrene triblock polymer (SEBS-g-MA) and maleic anhydride grafted polyethylene (PE-g-MA) were used to enhance impact performance and interfacial bonding between BaF and the resins. Mechanical, crystallization/melting, thermal stability, water absorption, and morphological properties of the composites were investigated. In the presence of SEBS-g-MA, better strengths and moduli were found for HDPE/Nylon-6 based composites compared with corresponding HDPE based composites. At a fixed weight ratio of PE-g-MA to BaF, an increase of BaF loading up to 48.2 wt.% led to a continuous improvement in moduli and flexural strength of final composites, while impact toughness was lowered gradually. Predicted tensile modulus by the Hones-Paul model for three-dimensional random fiber orientation agreed well with experimental data at the BaF loading of 29.3 wt.%. However, the randomly-oriented fiber models underestimated experimental data at higher fiber levels. It was found that the presence of SEBS-g-MA had a positive influence on reinforcing effect of the Nylon-6 component in the composites. Thermal analysis results showed that fractionated crystallization of the Nylon-6 component in the composites was induced by the addition of both SEBS-g-MA and PE-g-MA. Thermal stability of both composite systems differed slightly, except an additional decomposition peak related to the minor Nylon-6 for the composites from the HDPE/Nylon-6 blends. In the presence of SEBS-g-MA, the addition of Nylon-6 and increased BaF loading level led to an increase in the water absorption value of the composites.

  6. Interfacial characteristics and fracture behavior of spark-plasma-sintered TiNi fiber-reinforced 2024Al matrix composites

    International Nuclear Information System (INIS)

    Dong, Peng; Wang, Zhe; Wang, Wenxian; Chen, Shaoping; Zhou, Jun

    2017-01-01

    Embedding of shape memory alloy (SMA) fibers into materials to fabricate SMA composites has attracted considerable attention because of the potential applicability of these composites in smart systems and structures. In this study, 2024Al matrix composites reinforced by continuous TiNi SMA fibers were fabricated using spark plasma sintering (SPS). The interface between the fibers and matrix consisted of a bilayer. The layer close to the fiber consisted of a multiple phase mixture, and the other layer exhibited a periodic morphology resulting from the alternating phases of Al 3 Ti and Al 3 Ni. In addition, a small quantity of TiO 2 phases was also observed in the interface layer. Based on detailed interface studies of the orientation relationships between the Al 3 Ti, Al 3 Ni, and TiO 2 phases and the atomic correspondence at phase boundaries, the effects of the interface phases on the fracture behavior of the composites were demonstrated.

  7. Characterization, Long-Term Behavior Evaluation and Thermomechanical Properties of Untreated and Treated Flax Fiber-Reinforced Composites

    Science.gov (United States)

    Amiri, Ali

    In recent years there has been a resurgence of interest in the usage of natural fiber reinforced composites in more advanced structural applications. Consequently, the need for improving their mechanical properties as well as service life and long-term behavior modeling and predictions has arisen. In a step towards further development of these materials, in this study, two newly developed biobased resins, derived from soybean oil, methacrylated epoxidized sucrose soyate and double methacrylated epoxidized sucrose soyate are combined with untreated and alkaline treated flax fiber to produce novel biocomposites. Vinyl ester reinforced with flax fiber is used as control in addition to comparing properties of biobased composites against commercial pultruded composites. Effects of alkaline treatment of flax fiber as well as addition of 1% acrylic resin to vinyl ester and the two mentioned biobased resins on mechanical properties are studied. Properties are evaluated in short-term and also, after being exposed to accelerated weathering (i.e. UV and moisture). Moreover, long-term creep of these novel biobased composites and effect of fiber and matrix treatment on viscoelastic behavior is investigated using Time-temperature superposition (TTS) principle. Based on the results of this study, the TTS provides an accelerated method for evaluation of mechanical properties of biobased composites, and satisfactory master curves are achieved by use of this principle. Also, fiber and matrix treatments were effective in increasing mechanical properties of biobased composites in short-term, and treatments delayed the creep response and slowed the process of creep in composites under study in the steady state region. Overall, results of this study reveal the successful production of biocomposites having properties that meet or exceed those of conventional pultruded members while maintaining high biocontent. Composites using treated flax fiber and newly developed resins showed less

  8. Smart carbon nanotube/fiber and PVA fiber-reinforced composites for stress sensing and chloride ion detection

    Science.gov (United States)

    Hoheneder, Joshua

    Fiber reinforced composites (FRC) with polyvinyl alcohol (PVA) fibers and carbon nanofibers (CNF) had an excellent flexural strength in excess of 18.5 MPa compared to reference samples of 15.8 MPa. It was found that the developed, depending on applied stress and exposure to chloride solutions, composites exhibit some electrical conductivity, from 4.20×10 -4 (Ω-1m-1 to 4.13×10 -4 Ω-1m-1. These dependences can be characterized by piezioresistive and chemoresistive coefficients demonstrating that the material possesses self-sensing capabilities. The sensitivity to stain and chloride solutions can be enhanced by incorporating small amounts of carbon nanofibers (CNF) or carbon nanotube (CNT) into composite structure. Conducted research has demonstrated a strong dependency of electrical properties of composite on crack formation in moist environments. The developed procedure is scalable for industrial application in concrete structures that require nondestructive stress monitoring, integrity under high service loads and stability in harsh environments.

  9. Interfacial characteristics and fracture behavior of spark-plasma-sintered TiNi fiber-reinforced 2024Al matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Peng, E-mail: dongpeng@tyut.edu.cn [College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Shanxi Key Laboratory of Advanced Magnesium-Based Materials, Taiyuan 030024 (China); Wang, Zhe [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wang, Wenxian [College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Shanxi Key Laboratory of Advanced Magnesium-Based Materials, Taiyuan 030024 (China); Chen, Shaoping [College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Zhou, Jun [Department of Mechanical Engineering, Pennsylvania State University Erie, Erie, PA 16563 (United States)

    2017-04-13

    Embedding of shape memory alloy (SMA) fibers into materials to fabricate SMA composites has attracted considerable attention because of the potential applicability of these composites in smart systems and structures. In this study, 2024Al matrix composites reinforced by continuous TiNi SMA fibers were fabricated using spark plasma sintering (SPS). The interface between the fibers and matrix consisted of a bilayer. The layer close to the fiber consisted of a multiple phase mixture, and the other layer exhibited a periodic morphology resulting from the alternating phases of Al{sub 3}Ti and Al{sub 3}Ni. In addition, a small quantity of TiO{sub 2} phases was also observed in the interface layer. Based on detailed interface studies of the orientation relationships between the Al{sub 3}Ti, Al{sub 3}Ni, and TiO{sub 2} phases and the atomic correspondence at phase boundaries, the effects of the interface phases on the fracture behavior of the composites were demonstrated.

  10. Identifying design parameters controlling damage behaviors of continuous fiber-reinforced thermoplastic composites using micromechanics as a virtual testing tool

    KAUST Repository

    Pulungan, Ditho Ardiansyah; Lubineau, Gilles; Yudhanto, Arief; Yaldiz, Recep; Schijve, Warden

    2017-01-01

    In this paper, we propose a micromechanical approach to predict damage mechanisms and their interactions in glass fibers/polypropylene thermoplastic composites. First, a representative volume element (RVE) of such materials was rigorously determined using a geometrical two-point probability function and the eigenvalue stabilization of homogenized elastic tensor obtained by Hill-Mandel kinematic homogenization. Next, the 3D finite element models of the RVE were developed accordingly. The fibers were modeled with an isotropic linear elastic material. The matrix was modeled with an isotropic linear elastic, rate-independent hyperbolic Drucker-Prager plasticity coupled with a ductile damage model that is able to show pressure dependency of the yield and damage behavior often found in a thermoplastic material. In addition, cohesive elements were inserted into the fiber-matrix interfaces to simulate debonding. The RVE faces are imposed with periodical boundary conditions to minimize the edge effect. The RVE was then subjected to transverse tensile loading in accordance with experimental tensile tests on [90]8 laminates. The model prediction was found to be in very good agreement with the experimental results in terms of the global stress-strain curves, including the linear and nonlinear portion of the response and also the failure point, making it a useful virtual testing tool for composite material design. Furthermore, the effect of tailoring the main parameters of thermoplastic composites is investigated to provide guidelines for future improvements of these materials.

  11. Identifying design parameters controlling damage behaviors of continuous fiber-reinforced thermoplastic composites using micromechanics as a virtual testing tool

    KAUST Repository

    Pulungan, Ditho Ardiansyah

    2017-03-31

    In this paper, we propose a micromechanical approach to predict damage mechanisms and their interactions in glass fibers/polypropylene thermoplastic composites. First, a representative volume element (RVE) of such materials was rigorously determined using a geometrical two-point probability function and the eigenvalue stabilization of homogenized elastic tensor obtained by Hill-Mandel kinematic homogenization. Next, the 3D finite element models of the RVE were developed accordingly. The fibers were modeled with an isotropic linear elastic material. The matrix was modeled with an isotropic linear elastic, rate-independent hyperbolic Drucker-Prager plasticity coupled with a ductile damage model that is able to show pressure dependency of the yield and damage behavior often found in a thermoplastic material. In addition, cohesive elements were inserted into the fiber-matrix interfaces to simulate debonding. The RVE faces are imposed with periodical boundary conditions to minimize the edge effect. The RVE was then subjected to transverse tensile loading in accordance with experimental tensile tests on [90]8 laminates. The model prediction was found to be in very good agreement with the experimental results in terms of the global stress-strain curves, including the linear and nonlinear portion of the response and also the failure point, making it a useful virtual testing tool for composite material design. Furthermore, the effect of tailoring the main parameters of thermoplastic composites is investigated to provide guidelines for future improvements of these materials.

  12. Thermomechanical Fatigue Behavior of a Silicon Carbide Fiber-Reinforced Calcium Aluminosilicate Glass-Ceramic Matrix Composite.

    Science.gov (United States)

    1992-08-01

    Testing of Coated Monocrystalline Superalloys," in Low Cycle Fatigue. ASTM STP 942, Solomon, H.D., Hafford, G.R., Kaisand, L.R., and Keis, B.N. , eds...HOTOL) project is considering the use of CMCs on lower aeroshell panels , air intake leading edges, and the nose cone where temperatures may climb to...Works (Corning, NY). The composite was supplied in 16-ply, unidirectionally reinforced (10116) panels , measuring 152.4 cm x 152.4 cm (6 in x 6 in

  13. Paper-based energy-storage devices comprising carbon fiber-reinforced polypyrrole-cladophora nanocellulose composite electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Razaq, Aamir; Sjoedin, Martin; Stroemme, Maria; Mihranyan, Albert [Nanotechnology and Functional Materials, Department of Engineering Sciences, Uppsala (Sweden); Department of Chemistry, Angstroem Laboratory, Uppsala (Sweden); Nyholm, Leif [Department of Chemistry, Angstroem Laboratory, Uppsala (Sweden)

    2012-04-15

    Composites of polypyrrole (PPy) and Cladophora nanocellulose, reinforced with 8 {mu}m-thick chopped carbon filaments, can be used as electrode materials to obtain paper-based energy-storage devices with unprecedented performance at high charge and discharge rates. Charge capacities of more than 200 C g{sup -1} (PPy) are obtained for paper-based electrodes at potential scan rates as high as 500 mV s{sup -1}, whereas cell capacitances of {proportional_to}60-70 F g{sup -1} (PPy) are reached for symmetric supercapacitor cells with capacitances up to 3.0 F (i.e.,0.48 F cm{sup -2}) when charged to 0.6 V using current densities as high as 31 A g{sup -1} based on the PPy weight (i.e., 99 mA cm{sup -2}). Energy and power densities of 1.75 Wh kg{sup -1} and 2.7 kW kg{sup -1}, respectively, are obtained when normalized with respect to twice the PPy weight of the smaller electrode. No loss in cell capacitance is seen during charging/discharging at 7.7 A g{sup -1} (PPy) over 1500 cycles. It is proposed that the nonelectroactive carbon filaments decrease the contact resistances and the resistance of the reduced PPy composite. The present straightforward approach represents significant progress in the development of low-cost and environmentally friendly paper-based energy-storage devices for high-power applications. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Self-Healing Capability of Fiber-Reinforced Cementitious Composites for Recovery of Watertightness and Mechanical Properties

    Directory of Open Access Journals (Sweden)

    Tomoya Nishiwaki

    2014-03-01

    Full Text Available Various types of fiber reinforced cementitious composites (FRCCs were experimentally studied to evaluate their self-healing capabilities regarding their watertightness and mechanical properties. Cracks were induced in the FRCC specimens during a tensile loading test, and the specimens were then immersed in static water for self-healing. By water permeability and reloading tests, it was determined that the FRCCs containing synthetic fiber and cracks of width within a certain range (<0.1 mm exhibited good self-healing capabilities regarding their watertightness. Particularly, the high polarity of the synthetic fiber (polyvinyl alcohol (PVA series and hybrid fiber reinforcing (polyethylene (PE and steel code (SC series showed high recovery ratio. Moreover, these series also showed high potential of self-healing of mechanical properties. It was confirmed that recovery of mechanical property could be obtained only in case when crack width was sufficiently narrow, both the visible surface cracks and the very fine cracks around the bridging of the SC fibers. Recovery of the bond strength by filling of the very fine cracks around the bridging fibers enhanced the recovery of the mechanical property.

  15. Influence of screw holes and gamma sterilization on properties of phosphate glass fiber-reinforced composite bone plates.

    Science.gov (United States)

    Han, Na; Ahmed, Ifty; Parsons, Andrew J; Harper, Lee; Scotchford, Colin A; Scammell, Brigitte E; Rudd, Chris D

    2013-05-01

    Polymers prepared from polylactic acid (PLA) have found a multitude of uses as medical devices. For a material that degrades, the main advantage is that an implant would not necessitate a second surgical event for removal. In this study, fibers produced from a quaternary phosphate-based glass (PBG) in the system 50P2O5-40CaO-5Na2O-5Fe2O3 were used to reinforce PLA polymer. The purpose of this study was to assess the effect of screw holes in a range of PBG-reinforced PLA composites with varying fiber layup and volume fraction. The flexural properties obtained showed that the strength and modulus values increased with increasing fiber volume fraction; from 96 MPa to 320 MPa for strength and between 4 GPa and 24 GPa for modulus. Furthermore, utilizing a larger number of thinner unidirectional (UD) fiber prepreg layers provided a significant increase in mechanical properties, which was attributed to enhanced wet out and thus better fiber dispersion during production. The effect of gamma sterilization via flexural tests showed no statistically significant difference between the sterilized and nonsterilized samples, with the exception of the modulus values for samples with screw holes. Degradation profiles revealed that samples with screw holes degraded faster than those without screw holes due to an increased surface area for the plates with screw holes in PBS up to 30 days. Scanning electron microscope (SEM) analysis revealed fiber pullout before and after degradation. Compared with various fiber impregnation samples, with 25% volume fraction, 8 thinner unidirectional prepreg stacked samples had the shortest fiber pull-out lengths in comparison to the other samples investigated.

  16. Rapid replacement of Tangier Island bridges including lightweight and durable fiber-reinforced polymer deck systems.

    Science.gov (United States)

    2009-01-01

    Fiber-reinforced polymer (FRP) composite cellular deck systems were used as new bridge decks on two replacement bridges on Tangier Island, Virginia. The most important characteristics of this application were reduced self-weight and increased durabil...

  17. Fracture strength of fiber-reinforced surface-retained anterior cantilever restorations

    NARCIS (Netherlands)

    Oezcan, Mutlu; Kumbuloglu, Ovul; User, Atilla

    2008-01-01

    Purpose: This study compared the fracture strength of direct anterior cantilever fiber-reinforced composite (FRC) fixed partial dentures (FPD) reinforced with 3 types of E-glass fibers preimpregnated with either urethane tetramethacrylate, bisphenol glycidylmethacrylate/polymethyl methacrylate, or

  18. An experimental and theoretical investigation of stick-slip, steady-state and roughness dominated sliding in fiber-reinforced composites

    International Nuclear Information System (INIS)

    Mackin, T.J.

    1995-01-01

    The mechanical properties of fiber reinforced composites depends strongly upon the properties of the fiber/matrix interface. Enhanced fracture resistance and strain to failure are synonymous with debonding and sliding of the reinforcement phase. Thus, the two key properties of the composite are the interfacial toughness and the post-debond sliding stress. After debonding a variety of interfacial sliding phenomena are noted, including: stick-slip, steady-state, and roughness dominated sliding. The interfacial properties, including the coefficient of friction, the radial clamping pressure, asperity amplitude, the elastic properties of the constituents, and the compliance of the test machine, each play a role in the operative sliding phenomenon. Experiments have been conducted to explore each of these phenomena. In addition, models have been developed that rationalize all of the observed behavior

  19. Evaluation of Different Techniques of Active Thermography for Quantification of Artificial Defects in Fiber-Reinforced Composites Using Thermal and Phase Contrast Data Analysis

    Science.gov (United States)

    Maierhofer, Christiane; Röllig, Mathias; Gower, Michael; Lodeiro, Maria; Baker, Graham; Monte, Christian; Adibekyan, Albert; Gutschwager, Berndt; Knazowicka, Lenka; Blahut, Ales

    2018-05-01

    For assuring the safety and reliability of components and constructions in energy applications made of fiber-reinforced polymers (e.g., blades of wind turbines and tidal power plants, engine chassis, flexible oil and gas pipelines) innovative non-destructive testing methods are required. Within the European project VITCEA complementary methods (shearography, microwave, ultrasonics and thermography) have been further developed and validated. Together with partners from the industry, test specimens have been constructed and selected on-site containing different artificial and natural defect artefacts. As base materials, carbon and glass fibers in different orientations and layering embedded in different matrix materials (epoxy, polyamide) have been considered. In this contribution, the validation of flash and lock-in thermography to these testing problems is presented. Data analysis is based on thermal contrasts and phase evaluation techniques. Experimental data are compared to analytical and numerical models. Among others, the influence of two different types of artificial defects (flat bottom holes and delaminations) with varying diameters and depths and of two different materials (CFRP and GFRP) with unidirectional and quasi-isotropic fiber alignment is discussed.

  20. The restoration of a maxillary central incisor fracture with the original crown fragment using a glass fiber-reinforced post: a clinical report.

    Science.gov (United States)

    Durkan, Rukiye Kaplan; Ozel, M Birol; Celik, Davut; Bağiş, Bora

    2008-12-01

    This report describes an esthetic, conservative, and economical alternative restoration technique for a fractured central incisor using the patient's own tooth crown piece and a bondable reinforcement glass fiber. Although the long-term durability of this adhesive post core restoration remains unknown, it remains successful after 1 year.

  1. [Carbon fiber-reinforced plastics as implant materials].

    Science.gov (United States)

    Bader, R; Steinhauser, E; Rechl, H; Siebels, W; Mittelmeier, W; Gradinger, R

    2003-01-01

    Carbon fiber-reinforced plastics have been used clinically as an implant material for different applications for over 20 years.A review of technical basics of the composite materials (carbon fibers and matrix systems), fields of application,advantages (e.g., postoperative visualization without distortion in computed and magnetic resonance tomography), and disadvantages with use as an implant material is given. The question of the biocompatibility of carbon fiber-reinforced plastics is discussed on the basis of experimental and clinical studies. Selected implant systems made of carbon composite materials for treatments in orthopedic surgery such as joint replacement, tumor surgery, and spinal operations are presented and assessed. Present applications for carbon fiber reinforced plastics are seen in the field of spinal surgery, both as cages for interbody fusion and vertebral body replacement.

  2. Environmental Durability of Reinforced Concrete Deck Girders Strengthened for Shear with Surface-Bonded Carbon Fiber-Reinforced Polymer

    Science.gov (United States)

    2009-05-01

    "This research investigated the durability of carbon fiber-reinforced polymer composites (CFRP) used for shear strengthening reinforced concrete deck girders. Large beams were used to avoid accounting for size effects in the data analysis. The effort...

  3. Composites

    International Nuclear Information System (INIS)

    Kasen, M.B.

    1983-01-01

    This chapter discusses the roles of composite laminates and aggregates in cryogenic technology. Filamentary-reinforced composites are emphasized because they are the most widely used composite materials. Topics considered include composite systems and terminology, design and fabrication, composite failure, high-pressure reinforced plastic laminates, low-pressure reinforced plastics, reinforced metals, selectively reinforced structures, the effect of cryogenic temperatures, woven-fabric and random-mat composites, uniaxial fiber-reinforced composites, composite joints in cryogenic structures, joining techniques at room temperature, radiation effects, testing laminates at cryogenic temperatures, static and cyclic tensile testing, static and cyclic compression testing, interlaminar shear testing, secondary property tests, and concrete aggregates. It is suggested that cryogenic composite technology would benefit from the development of a fracture mechanics model for predicting the fitness-for-purpose of polymer-matrix composite structures

  4. Microscale damage mechanisms and degradation of fiber-reinforced composites for wind energy applications: results of Danish–Chinese collaborative investigations

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon; Zhou, H.W.; Yi, H.Y.

    2014-01-01

    Recent research works in the area of experimental and computational analyses of microscale mechanisms of strength, damage and degradation of glass fiber polymer composites for wind energy applications, which were carried out in the framework of a series of Sino–Danish collaborative research...... projects, are summarized in this article. In a series of scanning electron microscopy in situ experimental studies of composite degradation under off-axis tensile, compressive and cyclic loadings as well as three-dimensional computational experiments based on micromechanics of composites and damage...

  5. Effect of anodic surface treatment on PAN-based carbon fiber and its relationship to the fracture toughness of the carbon fiber-reinforced polymer composites

    DEFF Research Database (Denmark)

    Sarraf, Hamid; Skarpova, Ludmila

    2008-01-01

    The effect of anodic surface treatment on the polyacrylonitrile (PAN)-based carbon fibers surface properties and the mechanical behavior of the resulting carbon fiber-polymer composites has been studied in terms of the contact angle measurements of fibers and the fracture toughness of composites...... in the fiber surface nature and the mechanical interfacial properties between the carbon fiber and epoxy resin matrix of the resulting composites, i.e., the fracture toughness. We suggest that good wetting plays an important role in improving the degree of adhesion at interfaces between fibers and matrices...

  6. Rapid Strengthening of Full-Sized Concrete Beams with Powder-Actuated fastening Systems and Fiber-Reinforced Polymer (FRP) Composite Materials

    National Research Council Canada - National Science Library

    Bank, Lawrence

    2002-01-01

    A research study was conducted to determine if the method of retrofitting reinforced concrete beams with powder-actuated fasteners and composite materials was applicable to full-scale flexural members...

  7. Squid pen-inspired chitinous functional materials: Hierarchical chitin fibers by centrifugal jet-spinning and transparent chitin fiber-reinforced composite

    Science.gov (United States)

    Jeong, Seung-Hwan; Kim, Joong-Kwon; Lim, Young-Woo; Hwang, Hyun-Bin; Kwon, Hee-Young; Bae, Byeong-Soo; Jin, Jungho

    2018-01-01

    Here, inspired by the fibrous composite structure of a squid pen, we introduce hierarchical chitin fibers (herein, termed "Chiber") and their transparent composites and demonstrate the potential of these chitinous functional materials as a sustainable separation-membrane and reinforcing filler for composites. We employ a centrifugal jet-spinning process to fabricate Chiber with aligned chitin nanofibrillar architectures, for which we discuss the processing-morphology relationship. A nonwoven fiber-mat made of Chiber exhibits excellent adsorbing performance for a toxic ionic dye (Congo Red), and has a low coefficient of thermal expansion comparable to that of glass fibers. Finally, we demonstrate a squid pen-mimetic transparent composite using Chiber and investigate its optical property.

  8. Effects of KMnO4 Treatment on the Flexural, Impact, and Thermal Properties of Sugar Palm Fiber-Reinforced Thermoplastic Polyurethane Composites

    Science.gov (United States)

    Mohammed, A. A.; Bachtiar, D.; Rejab, M. R. M.; Jiang, X. X.; Abas, Falak O.; Abass, Raghad U.; Hasany, S. F.; Siregar, Januar P.

    2018-05-01

    Global warming has had a great impact on environmental changes since the last decade. Eco-friendly industrial products are of great importance to sustain life on earth, including using natural composites. Natural fibers used as fillers are also environmentally valuable because of their biodegradable nature. However, compatibility issues between the fiber and its respective matrix is a major concern. The present work focused on the study of the flexural, impact, and thermal behaviors of environmentally friendly sugar palm fibers (SPF) incorporated into a composite with thermoplastic polyurethane (TPU). Two techniques (extrusion and compression molding) were used to prepare these composites. The fiber size and dosage were kept constant at 250 µm and 30 wt.% SPF, respectively. The effects of potassium permanganate (KMnO4) treatment on the flexural, impact, and thermal behaviors of the treated SPF with 6% NaOH-reinforced TPU composites were investigated. Three different concentrations of KMnO4 (0.033%, 0.066%, and 0.125%) were studied for this purpose. The characterization of the flexural and impact properties of the new TPU/SPF composites was studied as per American Society for Testing Materials ASTM standards. Thermogravimetric analysis was employed for thermal behavior analysis of the TPU/SPF composites. The best flexural strength, impact strength, and modulus properties (8.118 MPa, 55.185 kJ/m2, and 262.102 MPa, respectively) were obtained with a 0.033% KMnO4-treated sample. However, all flexural strength, impact strength, and modulus properties for the KMnO4-treated samples were lower than the sample treated only with 6% NaOH. The highest thermal stability was also shown by the sample treated with 0.033% KMnO4. Therefore, this method enhanced the thermal properties of the TPU/SPF composites with clear deterioration of the flexural and impact properties.

  9. Fiber-reinforced ceramic matrix composites processed by a hybrid technique based on chemical vapor infiltration, slurry impregnation and spark plasma sintering

    International Nuclear Information System (INIS)

    Magnant, J.; Pailler, R.; Le Petitcorps, Y.; Maille, L.; Guette, A.; Marthe, J.

    2013-01-01

    Fabrication of multidirectional continuous carbon and silicon carbide fiber reinforced ceramic matrix composites (CMC) by a new short time hybrid process was studied. This process is based, first, on the deposition of fiber interphase and coating by chemical vapor infiltration, next, on the introduction of silicon nitride powders into the fibrous preform by slurry impregnation and, finally, on the densification of the composite by liquid phase spark plasma sintering (LP-SPS). The homogeneous introduction of the ceramic charges into the multidirectional fiber pre-forms was realized by slurry impregnation from highly concentrated and well-dispersed aqueous colloid suspensions. The chemical degradation of the carbon fibers during the fabrication was prevented by adapting the sintering pressure cycle. The composites manufactured are dense. Microstructural analyses were conducted to explain the mechanical properties achieved. One main important result of this study is that LP-SPS can be used in some hybrid processes to densify fiber reinforced CMC. (authors)

  10. ASSESSMENTS OF FUTURE ENVIRONMENTAL TRENDS AND PROBLEMS OF INCREASED USE, RECYCLING, AND COMBUSTION OF FIBER-REINFORCED, PLASTIC AND METAL COMPOSITE MATERIALS

    Science.gov (United States)

    The purpose of the study is to identify and define future environmental concerns related to the projected utilization, recycling, and combustion of composite materials. The study is being conducted for the Office of Strategic Assessment and Special Studies (OSASS) of the U.S. Env...

  11. Advance study of fiber-reinforced self-compacting concrete

    Science.gov (United States)

    Mironova, M.; Ivanova, M.; Naidenov, V.; Georgiev, I.; Stary, J.

    2015-10-01

    Incorporation in concrete composition of steel macro- and micro - fiber reinforcement with structural function increases the degree of ductility of typically brittle cement-containing composites, which in some cases can replace completely or partially conventional steel reinforcement in the form of rods and meshes. Thus, that can reduce manufacturing, detailing and placement of conventional reinforcement, which enhances productivity and economic efficiency of the building process. In this paper, six fiber-reinforced with different amounts of steel fiber cement-containing self-compacting compositions are investigated. The results of some of their main strength-deformation characteristics are presented. Advance approach for the study of structural and material properties of these type composites is proposed by using the methods of industrial computed tomography. The obtained original tomography results about the microstructure and characteristics of individual structural components make it possible to analyze the effective macro-characteristics of the studied composites. The resulting analytical data are relevant for the purposes of multi-dimensional modeling of these systems. Multifactor structure-mechanical analysis of the obtained with different methods original scientific results is proposed. It is presented a conclusion of the capabilities and effectiveness of complex analysis in the studies to characterize the properties of self-compacting fiber-reinforced concrete.

  12. Advance study of fiber-reinforced self-compacting concrete

    International Nuclear Information System (INIS)

    Mironova, M.; Ivanova, M.; Naidenov, V.; Georgiev, I.; Stary, J.

    2015-01-01

    Incorporation in concrete composition of steel macro- and micro – fiber reinforcement with structural function increases the degree of ductility of typically brittle cement-containing composites, which in some cases can replace completely or partially conventional steel reinforcement in the form of rods and meshes. Thus, that can reduce manufacturing, detailing and placement of conventional reinforcement, which enhances productivity and economic efficiency of the building process. In this paper, six fiber-reinforced with different amounts of steel fiber cement-containing self-compacting compositions are investigated. The results of some of their main strength-deformation characteristics are presented. Advance approach for the study of structural and material properties of these type composites is proposed by using the methods of industrial computed tomography. The obtained original tomography results about the microstructure and characteristics of individual structural components make it possible to analyze the effective macro-characteristics of the studied composites. The resulting analytical data are relevant for the purposes of multi-dimensional modeling of these systems. Multifactor structure-mechanical analysis of the obtained with different methods original scientific results is proposed. It is presented a conclusion of the capabilities and effectiveness of complex analysis in the studies to characterize the properties of self-compacting fiber-reinforced concrete

  13. Advance study of fiber-reinforced self-compacting concrete

    Energy Technology Data Exchange (ETDEWEB)

    Mironova, M., E-mail: mirona@imbm.bas.bg; Ivanova, M., E-mail: magdalena.ivanova@imbm.bas.bg; Naidenov, V., E-mail: valna53@mail.bg [Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 4, Sofia 1113 (Bulgaria); Georgiev, I., E-mail: ivan.georgiev@parallel.bas.bg [Institute of Information and Communication Technologies & Institute of Mathematics and Informatics, Bulgarian Academy of Sciences, Acad. G. Bonchev str., Sofia 1113 (Bulgaria); Stary, J., E-mail: stary@ugn.cas.cz [Institute of Geonics Czech Academy of Sciences, Studentska str., Ostrava 1768 (Czech Republic)

    2015-10-28

    Incorporation in concrete composition of steel macro- and micro – fiber reinforcement with structural function increases the degree of ductility of typically brittle cement-containing composites, which in some cases can replace completely or partially conventional steel reinforcement in the form of rods and meshes. Thus, that can reduce manufacturing, detailing and placement of conventional reinforcement, which enhances productivity and economic efficiency of the building process. In this paper, six fiber-reinforced with different amounts of steel fiber cement-containing self-compacting compositions are investigated. The results of some of their main strength-deformation characteristics are presented. Advance approach for the study of structural and material properties of these type composites is proposed by using the methods of industrial computed tomography. The obtained original tomography results about the microstructure and characteristics of individual structural components make it possible to analyze the effective macro-characteristics of the studied composites. The resulting analytical data are relevant for the purposes of multi-dimensional modeling of these systems. Multifactor structure-mechanical analysis of the obtained with different methods original scientific results is proposed. It is presented a conclusion of the capabilities and effectiveness of complex analysis in the studies to characterize the properties of self-compacting fiber-reinforced concrete.

  14. Influence of Laser Activated Irrigation with Erbium Lasers on Bond Strength of Inidividually Formed Fiber Reinforced Composite Posts to Root Canal Dentin

    Directory of Open Access Journals (Sweden)

    Ivana Miletić

    2016-01-01

    Full Text Available Objective: The aim of this in vitro study was to investigate the effect of laser activated irrigation (LAI using two erbium lasers on bond strength of individually formed fiber-reinforced composite (FRC posts to root canal dentin. Materials and methods: Twenty-seven single-rooted human teeth were endodontically treated and after post space preparation divided into three groups (n=9 per group, according to the pre-treatment of post space preparation: 1 Conventional syringe irrigation (CSI and saline; 2 Er.YAG photon-induced photoacoustic streaming (PIPS technique and saline; 3 Er,Cr:YSGG activated irrigation with RFT2 tip. Two specimens from each group were used for SEM analysis. The remaining specimens (n=7 per group received individually formed FRC post, everStick POST, luted with self-adhesive cement, G-CEM LinkAce. After cementation, the roots were perpendicularly sectioned into 1 mm thin sections and a push-out test was carried out (0.5 mm/min. The data were calculated as megapascals and were log transformed and statistically analysed using one-way ANOVA at the level of significance set at 5%. Results: In the control group, the smear layer was still present. In the Er:YAG group, the smear layer was removed. In the Er,Cr:YSGG group, the smear layer was partially removed. The Er,Cr:YSGG group achieved the highest bond strength values, followed by the control group and then the Er:YAG group, but no statistically significant difference was found in bond strength values in the tested group of post space pretreatment (p=0.564. Conclusions: LAI using two erbium lasers, with PIPS or RFT2 tip, did not affect the bond strength of individually formed FRC posts to root canal dentin.

  15. Non-destructive evaluation of fiber-reinforced composites with a fast 2D fiber-optic laser-ultrasound scanner

    Science.gov (United States)

    Pelivanov, Ivan; Buma, Takashi; Xia, Jinjun; Wei, Chen-Wei; Shtokolov, Alex; O'Donnell, Matthew

    2015-03-01

    Laser ultrasonic (LU) inspection represents an attractive, non-contact method to evaluate composite materials. Current non-contact systems, however, have relatively low sensitivity compared to contact piezoelectric detection. They are also difficult to adjust, very expensive, and strongly influenced by environmental noise. Here, we demonstrate that most of these drawbacks can be eliminated by combining a new generation of compact, inexpensive fiber lasers with new developments in fiber telecommunication optics and an optimally designed balanced probe scheme. In particular, a new type of a balanced fiber-optic Sagnac interferometer is presented as part of an all-optical LU pump-probe system for high speed non-destructive testing and evaluation (NDT&E) of aircraft composites. The performance of the LU system is demonstrated on a composite sample typically used in the aircraft industry. Wide-band ultrasound probe signals are generated directly at the sample surface with a pulsed diode-pumped laser delivering nanosecond laser pulses at a 1 kHz repetition rate with a pulse energy of 2 mJ. A balanced fiber-optic Sagnac interferometer is employed to detect pressure signals in a 1-10 MHz frequency range at the same point (an 8 μm focal spot) on the composite surface. A fast (up to 100 mm/s) 2D translation system is employed to move the sample during scanning and produce a complete B-scan consisting of one thousand A-scans in less than a second. The sensitivity of this system, in terms of the noise equivalent pressure, is found to be only 10 dB above the Nyquist thermal noise limit. To our knowledge, this is the best reported sensitivity for a non-contact ultrasonic detector of this dimension.

  16. Stabilized fiber-reinforced pavement base course with recycled aggregate

    Science.gov (United States)

    Sobhan, Khaled

    This study evaluates the benefits to be gained by using a composite highway base course material consisting of recycled crushed concrete aggregate, portland cement, fly ash, and a modest amount of reinforcing fibers. The primary objectives of this research were to (a) quantify the improvement that is obtained by adding fibers to a lean concrete composite (made from recycled aggregate and low quantities of Portland cement and/or fly ash), (b) evaluate the mechanical behavior of such a composite base course material under both static and repeated loads, and (c) utilize the laboratory-determined properties with a mechanistic design method to assess the potential advantages. The split tensile strength of a stabilized recycled aggregate base course material was found to be exponentially related to the compacted dry density of the mix. A lean mix containing 4% cement and 4% fly ash (by weight) develops sufficient unconfined compressive, split tensile, and flexural strengths to be used as a high quality stabilized base course. The addition of 4% (by weight) of hooked-end steel fibers significantly enhances the post-peak load-deformation response of the composite in both indirect tension and static flexure. The flexural fatigue behavior of the 4% cement-4% fly ash mix is comparable to all commonly used stabilized materials, including regular concrete; the inclusion of 4% hooked-end fibers to this mix significantly improves its resistance to fatigue failure. The resilient moduli of stabilized recycled aggregate in flexure are comparable to the values obtained for traditional soil-cement mixes. In general, the fibers are effective in retarding the rate of fatigue damage accumulation, which is quantified in terms of a damage index defined by an energy-based approach. The thickness design curves for a stabilized recycled aggregate base course, as developed by using an elastic layer approach, is shown to be in close agreement with a theoretical model (based on Westergaard

  17. Size-Resolved Characterization of Particles and Fibers Released during Abrasion of Fiber-Reinforced Composite in a Workplace Influenced by Ambient Background Sources

    DEFF Research Database (Denmark)

    Kling, Kirsten I.; Levin, Marcus; Jensen, Alexander C. O.

    2016-01-01

    We demonstrate the use of high-to low-resolution microscopy and particle chemical analysis during normal vacuum and cryo-conditions to identify the nature and relative abundances of process-generated particles and fibers from sanding of a glass and carbon fiber epoxy layer-composite in a workplace...... influenced by both indoor and ambient background sources. The study suggests that a proper exposure characterization requires multiple techniques covering wide size ranges to reach a conclusion. Besides a rise in number concentration due to release of particles during the sanding, a significant contribution...

  18. Numerical and Experimental Characterization of Fiber-Reinforced Thermoplastic Composite Structures with Embedded Piezoelectric Sensor-Actuator Arrays for Ultrasonic Applications

    Directory of Open Access Journals (Sweden)

    Klaudiusz Holeczek

    2016-02-01

    Full Text Available The paper presents preliminary numerical and experimental studies of active textile-reinforced thermoplastic composites with embedded sensor-actuator arrays. The goal of the investigations was the assessment of directional sound wave generation capability using embedded sensor-actuator arrays and developed a wave excitation procedure for ultrasound measurement tasks. The feasibility of the proposed approach was initially confirmed in numerical investigations assuming idealized mechanical and geometrical conditions. The findings were validated in real-life conditions on specimens of elementary geometry. Herein, the technological aspects of unique automated assembly of thermoplastic films containing adapted thermoplastic-compatible piezoceramic modules and conducting paths were described.

  19. Bonding Characteristics of Macrosynthetic Fiber in Latex-Modified Fiber-Reinforced Cement Composites as a Function of Carbon Nanotube Content

    Directory of Open Access Journals (Sweden)

    Ji-Hong Jean

    2016-01-01

    Full Text Available The effect of carbon nanotube content (0, 0.5, 1.0, 1.5, and 2.0% of the cement weight on the bonding properties of macrosynthetic fiber in latex-modified hybrid fiber cement-based composites (LMHFRCCs was evaluated. The slump value, compressive strength, and bonding strength were measured for each LMHFRCC. As the carbon nanotube content increased to 1.5%, the bonding properties of the macrosynthetic fiber improved. However, the bonding performance deteriorated at a carbon nanotube content of 2.0%. A decrease in the fluidity of the mix negatively affected the dispersion of the nanotubes in the LMHFRCCs. The addition of carbon nanotubes also affected the relative bonding strength independently of the improvement in compressive strength. Microscopic analysis of the macrosynthetic fiber surfaces was used to understand changes in the bonding behavior.

  20. Design Guidelines for In-Plane Mechanical Properties of SiC Fiber-Reinforced Melt-Infiltrated SiC Composites

    Science.gov (United States)

    Morscher, Gregory N.; Pujar, Vijay V.

    2008-01-01

    In-plane tensile stress-strain, tensile creep, and after-creep retained tensile properties of melt-infiltrated SiC-SiC composites reinforced with different fiber types were evaluated with an emphasis on obtaining simple or first-order microstructural design guidelines for these in-plane mechanical properties. Using the mini-matrix approach to model stress-strain behavior and the results of this study, three basic general design criteria for stress and strain limits are formulated, namely a design stress limit, a design total strain limit, and an after-creep design retained strength limit. It is shown that these criteria can be useful for designing components for high temperature applications.

  1. Multi-layer porous fiber-reinforced composites for implants: in vitro calcium phosphate formation in the presence of bioactive glass.

    Science.gov (United States)

    Nganga, Sara; Zhang, Di; Moritz, Niko; Vallittu, Pekka K; Hupa, Leena

    2012-11-01

    Glass-fiber-reinforced composites (FRCs), based on bifunctional methacrylate resin, have recently shown their potential for use as durable cranioplasty, orthopedic and oral implants. In this study we suggest a multi-component sandwich implant structure with (i) outer layers out of porous FRC, which interface the cortical bone, and (ii) inner layers encompassing bioactive glass granules, which interface with the cancellous bone. The capability of Bioglass(®) 45S5 granules (100-250μm) to induce calcium phosphate formation on the surface of the FRC was explored by immersing the porous FRC-Bioglass laminates in simulated body fluid (SBF) for up to 28d. In both static (agitated) and dynamic conditions, bioactive glass granules induced precipitation of calcium phosphate at the laminate surfaces as confirmed by scanning electron microscopy. The proposed dynamic flow system is useful for the in vitro simulation of bone-like apatite formation on various new porous implant designs containing bioactive glass and implant material degradation. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  2. Influence of increment thickness on dentin bond strength and light transmission of composite base materials.

    Science.gov (United States)

    Omran, Tarek A; Garoushi, Sufyan; Abdulmajeed, Aous A; Lassila, Lippo V; Vallittu, Pekka K

    2017-06-01

    Bulk-fill resin composites (BFCs) are gaining popularity in restorative dentistry due to the reduced chair time and ease of application. This study aimed to evaluate the influence of increment thickness on dentin bond strength and light transmission of different BFCs and a new discontinuous fiber-reinforced composite. One hundred eighty extracted sound human molars were prepared for a shear bond strength (SBS) test. The teeth were divided into four groups (n = 45) according to the resin composite used: regular particulate filler resin composite: (1) G-ænial Anterior [GA] (control); bulk-fill resin composites: (2) Tetric EvoCeram Bulk Fill [TEBF] and (3) SDR; and discontinuous fiber-reinforced composite: (4) everX Posterior [EXP]. Each group was subdivided according to increment thickness (2, 4, and 6 mm). The irradiance power through the material of all groups/subgroups was quantified (MARC® Resin Calibrator; BlueLight Analytics Inc.). Data were analyzed using two-way ANOVA followed by Tukey's post hoc test. SBS and light irradiance decreased as the increment's height increased (p composite used. EXP presented the highest SBS in 2- and 4-mm-thick increments when compared to other composites, although the differences were not statistically significant (p > 0.05). Light irradiance mean values arranged in descending order were (p composites. Discontinuous fiber-reinforced composite showed the highest value of curing light transmission, which was also seen in improved bonding strength to the underlying dentin surface. Discontinuous fiber-reinforced composite can be applied safely in bulks of 4-mm increments same as other bulk-fill composites, although, in 2-mm thickness, the investigated composites showed better performance.

  3. Modal analysis of pre and post impacted nano composite laminates

    Directory of Open Access Journals (Sweden)

    R. Velmurugan

    Full Text Available Modal analysis is carried out on pre and post impacted nano composite laminates. The laminates are prepared using 3, 5 and 8 layers of 610gsm glass woven roving mats(WRM with epoxy resin and montmorillonite(MMT clay content is varied from 1% to 5%. Impulse hammer technique is used to find natural frequency and damping factor of laminates. Medium velocity impact tests are conducted by using a gas gun. The vibration responses of natural frequency and damping factor are obtained and are studied for laminates with all edges clamped boundary conditions. Results show considerable improvement in natural frequency and damping factor due to nano clay addition. It is also seen that the nano clay controls the delamination due to impact loading.

  4. Fracture Behavior and Properties of Functionally Graded Fiber-Reinforced Concrete

    International Nuclear Information System (INIS)

    Roesler, Jeffery; Bordelon, Amanda; Gaedicke, Cristian; Park, Kyoungsoo; Paulino, Glaucio

    2008-01-01

    In concrete pavements, a single concrete mixture design is selected to resist mechanical loading without attempting to adversely affect the concrete pavement shrinkage, ride quality, or noise attenuation. An alternative approach is to design distinct layers within the concrete pavement surface which have specific functions thus achieving higher performance at a lower cost. The objective of this research was to address the structural benefits of functionally graded concrete materials (FGCM) for rigid pavements by testing and modeling the fracture behavior of different combinations of layered plain and synthetic fiber-reinforced concrete materials. Fracture parameters and the post-peak softening behavior were obtained for each FGCM beam configuration by the three point bending beam test. The peak loads and initial fracture energy between the plain, fiber-reinforced, and FGCM signified similar crack initiation. The total fracture energy indicated improvements in fracture behavior of FGCM relative to full-depth plain concrete. The fracture behavior of FGCM depended on the position of the fiber-reinforced layer relative to the starter notch. The fracture parameters of both fiber-reinforced and plain concrete were embedded into a finite element-based cohesive zone model. The model successfully captured the experimental behavior of the FGCMs and predicted the fracture behavior of proposed FGCM configurations and structures. This integrated approach (testing and modeling) demonstrates the viability of FGCM for designing layered concrete pavements system

  5. Properties of Fiber-Reinforced Mortars Incorporating Nano-Silica

    Directory of Open Access Journals (Sweden)

    Ahmed Ghazy

    2016-02-01

    Full Text Available Repair and rehabilitation of deteriorating concrete elements are of significant concern in many infrastructural facilities and remain a challenging task. Concerted research efforts are needed to develop repair materials that are sustainable, durable, and cost-effective. Research data show that fiber-reinforced mortars/concretes have superior performance in terms of volume stability and toughness. In addition, it has been recently reported that nano-silica particles can generally improve the mechanical and durability properties of cement-based systems. Thus, there has been a growing interest in the use of nano-modified fiber-reinforced cementitious composites/mortars (NFRM in repair and rehabilitation applications of concrete structures. The current study investigates various mechanical and durability properties of nano-modified mortar containing different types of fibers (steel, basalt, and hybrid (basalt and polypropylene, in terms of compressive and flexural strengths, toughness, drying shrinkage, penetrability, and resistance to salt-frost scaling. The results highlight the overall effectiveness of the NFRM owing to the synergistic effects of nano-silica and fibers.

  6. Applications of Fiber-Reinforced Polymers in Additive Manufacturing

    DEFF Research Database (Denmark)

    Hofstätter, Thomas; Pedersen, David Bue; Tosello, Guido

    2017-01-01

    Additive manufacturing technologies are these years entering the market of functional final parts. Initial research has been performed targeting the integration of fibers into additive manufactured plastic composites. Major advantages, among others, are for example increased tensile strength...... and Young's modulus. Key challenges in the field, as of now, are proper fiber placement, fiber seizing, an increased knowledge in the used materials and how they are applied into engineering solutions through proper control of the additive manufacturing process. The aim of this research is the improved...... understanding of fiber-reinforcement in additive manufacturing in terms of production and application. Vat polymerization and material extrusion techniques for composite additive manufacturing were investigated with respect of increasing adhesion between the matrix material and the fibers. Process optimization...

  7. Life Prediction for FRP composites with Data Fusion & Machine Learning

    Data.gov (United States)

    National Aeronautics and Space Administration — High-fidelity, probabilistic predictions of damage evolution in fiber-reinforced polymer (FRP) composite structures could accelerate development and certification of...

  8. Post-irradiation examinations of THERMHET composite fuels for transmutation

    Science.gov (United States)

    Noirot, J.; Desgranges, L.; Chauvin, N.; Georgenthum, V.

    2003-07-01

    The thermal behaviour of composite targets dedicated to minor actinide transmutation was studied using THERMHET (thermal behaviour of heterogeneous fuel) irradiation in the SILOE reactor. Three inert matrix fuel designs were tested (macro-mass, jingle and microdispersion) all with a MgAl 2O 4 spinel inert matrix and around 40% weight of UO 2 to simulate minor actinide inclusions. The post-irradiation examinations led to a new interpretation of the temperature measurement by thermocouples located in the central hole of the pellets. A major change in the micro-dispersed structure was detected. The examinations enabled us to understand the behaviour of the spinel during the different stages of irradiation. They revealed an amorphisation at low temperature and then a nano re-crystallisation at high temperature of the spinel in the micro-dispersed case. These results, together with those obtained in the MATINA irradiation of an equivalent structure, show the importance of the irradiation temperature on spinel behaviour.

  9. Post-irradiation examinations of THERMHET composite fuels for transmutation

    Energy Technology Data Exchange (ETDEWEB)

    Noirot, J. E-mail: jnoirot@cea.fr; Desgranges, L.; Chauvin, N.; Georgenthum, V

    2003-07-01

    The thermal behaviour of composite targets dedicated to minor actinide transmutation was studied using THERMHET (thermal behaviour of heterogeneous fuel) irradiation in the SILOE reactor. Three inert matrix fuel designs were tested (macro-mass, jingle and microdispersion) all with a MgAl{sub 2}O{sub 4} spinel inert matrix and around 40% weight of UO{sub 2} to simulate minor actinide inclusions. The post-irradiation examinations led to a new interpretation of the temperature measurement by thermocouples located in the central hole of the pellets. A major change in the micro-dispersed structure was detected. The examinations enabled us to understand the behaviour of the spinel during the different stages of irradiation. They revealed an amorphisation at low temperature and then a nano re-crystallisation at high temperature of the spinel in the micro-dispersed case. These results, together with those obtained in the MATINA irradiation of an equivalent structure, show the importance of the irradiation temperature on spinel behaviour.

  10. Post-irradiation examinations of THERMHET composite fuels for transmutation

    International Nuclear Information System (INIS)

    Noirot, J.; Desgranges, L.; Chauvin, N.; Georgenthum, V.

    2003-01-01

    The thermal behaviour of composite targets dedicated to minor actinide transmutation was studied using THERMHET (thermal behaviour of heterogeneous fuel) irradiation in the SILOE reactor. Three inert matrix fuel designs were tested (macro-mass, jingle and microdispersion) all with a MgAl 2 O 4 spinel inert matrix and around 40% weight of UO 2 to simulate minor actinide inclusions. The post-irradiation examinations led to a new interpretation of the temperature measurement by thermocouples located in the central hole of the pellets. A major change in the micro-dispersed structure was detected. The examinations enabled us to understand the behaviour of the spinel during the different stages of irradiation. They revealed an amorphisation at low temperature and then a nano re-crystallisation at high temperature of the spinel in the micro-dispersed case. These results, together with those obtained in the MATINA irradiation of an equivalent structure, show the importance of the irradiation temperature on spinel behaviour

  11. Photoelastic stress analysis of different prefabricated post-and-core materials.

    Science.gov (United States)

    Asvanund, Pattapon; Morgano, Steven M

    2011-01-01

    The purpose of this study was to investigate stress developed by a combination of a stainless steel post or a fiber-reinforced resin post with a silver amalgam core or a composite resin core. Two-dimensional photoelastic models were used to simulate root dentin. Posts (ParaPost XT and ParaPost-FiberWhite) were cemented with a luting agent (RelyX Unicem). Silver amalgam cores and composite resin cores were fabricated on the posts. Complete crowns were fabricated and cemented on the cores. Each model was analyzed with 2 force magnitudes and in 2 directions. Fringe orders were recorded and compared using ANOVA (p=0.05) and the Scheffe's test. With vertical force, no stress differences occurred among the 4 groups (p=0.159). With a 30-degree force, there was stress differences among the 4 groups (p<0.001). The combination of a fiber-reinforced post and composite resin core could potentially reduce stresses within the radicular dentin when angled loads are applied.

  12. Microleakage of Different Post Systems and a Custom Adapted Fiber Post

    Directory of Open Access Journals (Sweden)

    Farideh Geramipanah

    2013-01-01

    Full Text Available Objective: The effects of closely adapting a prefabricated fiber to the post space remain unknown. The purpose of this study was to quantify the microleakages of a custom adapted fiber-reinforced post, a prefabricated quartz fiber post and a cast post using nondestructive methods.Materials and Methods: Sixty-five extracted human premolars were endodontically treated and randomly divided into three groups (n=15, which were restored using a cast post-and-core, a custom adapted fiber post (Refropost with a microhybrid microfiller resin composite (Gradia, or a prefabricated quartz fiber post (DT light post and two groups of control ( n=10. All groups were cemented using a dual polymerizing resin cement (Panavia F2.0. A composite core (Z100 was used for the fiber posts. The microleakage was calculated for the experimental and control groups before and after thermal cycling and cycling loading using a radiotracer solution (thallium 201 chloride and a gamma counter device. Data were subjected to statistical analysis of ANOVA and Tukey HSD at significant level of P< 0.05.Results: Significantly lower microleakage values were found for the cast post-and-core (mean value =16.04 ×104 and custom adapted fiber post groups (mean value=14.36×104. Thermal cycling and cyclic loading had no significant effect on the microleakage value of any tested group.Conclusion: Post systems with improved adaptation showed similar microleakage to casting post

  13. Post-buckling analysis of composite beams: A simple intuitive ...

    Indian Academy of Sciences (India)

    and lateral displacement functions at any discrete location of the beam. ..... shells under combined axial compression and radial pressure. ... Razakamiadana A and Zidi M 1999 Buckling and post-buckling of concentric cylindrical tubes under.

  14. Challenges and Opportunities for Nanotechnology in Multi-Functional Composite Structures (Preprint)

    National Research Council Canada - National Science Library

    Baur, Jeff; Silverman, Edward

    2006-01-01

    .... Of the wide variety of structural applications, fiber-reinforced composites for aerospace structures have some of the most demanding applications with extreme requirements in physical, chemical...

  15. Accelerated aging of adhesive-mediated fiber post-resin composite bonds: A modeling approach.

    Science.gov (United States)

    Radovic, Ivana; Monticelli, Francesca; Papacchini, Federica; Magni, Elisa; Cury, Alvaro Hafiz; Vulicevic, Zoran R; Ferrari, Marco

    2007-08-01

    Although fiber posts luted in root canals are not directly exposed to oral fluids, water storage is considered as in vitro accelerated aging test for bonded interfaces. The aim of the study was to evaluate the influence of accelerated water aging on fiber post-resin composite adhesion. Forty fiber posts (DT Light Post, RTD) were randomly divided into two main groups, according to the surface treatment performed. Group I: XPBond adhesive (Dentsply Caulk); Group II: sandblasting (Rocatec-Pre, 3M ESPE) and XPBond. Dual-cured resin cement (Calibra, Dentsply Caulk) and flowable composite (X-Flow, Dentsply Caulk) were applied on the posts to produce cylindrical specimens. The bond strength at the interface between post and cement/composite was measured with the microtensile test according to the non-trimming technique. Half of the sticks were tested immediately for bond strength, while in the other half testing was performed after 1 month of water storage at 37 degrees C. Post-cement/composite interfaces were evaluated under SEM prior and after water aging. Statistical analysis was performed using the Kruskal-Wallis ANOVA followed by Dunn's multiple range test (p<0.05). Immediate bond strength was higher on sandblasted posts. After water aging the two post surface treatments resulted comparable in bond strength. Resin cement achieved higher bond strength to fiber posts than flowable composite. Water aging significantly reduced bond strength. Sandblasting followed by adhesive coating may improve immediate post-resin bond strength in comparison to adhesive alone. However, fiber post-resin bond strength mediated by hydrophilic adhesive tends to decrease after water aging.

  16. Flexural behaviour of post-cured composites at oral-simulating temperatures.

    Science.gov (United States)

    Ho, C T; Vijayaraghavan, T V; Lee, S Y; Tsai, A; Huang, H M; Pan, L C

    2001-07-01

    Post-curing treatments have been known to improve the mechanical stability of visible light-cured composites. After individual post-curing treatment, the flexural strength (FS) of four commercial direct/indirect placement composite materials which differ greatly in composition [oligocarbonate dimethacrylate (OCDMA)-based Conquest C & B (CQT), Bisphenol-A glycidyl dimethacrylate (BisGMA)-based Charisma, urethane dimethacrylate (UDMA)-based Concept (CCT), and BisGMA/UDMA-based Dentacolor] was evaluated under water in the temperature range of 12-50 degrees C. A control series was tested in air at room temperature (25 +/- 1 degrees C). Data were analysed using ANOVA and Duncan's test. Flexural strengths overall decreased (20-40%, P OCDMA-based materials. Post-cured composites can be significantly affected by exposure to oral environments. Different composition determines the degree of influence.

  17. Radiation effects on carbon fiber-reinforced plastics for spacecraft materials

    International Nuclear Information System (INIS)

    Udagawa, Akira; Kudoh, Hisaaki; Sasuga, Tsuneo; Morino, Yoshiki; Seguchi, Tadao; Yudate, Kozo.

    1995-02-01

    The effects of space environment were studied for two kinds of carbon fiber-reinforced plastics(CFRP) which were an epoxy resin composite using construction materials of satellite and a polyimide(PMR-15) composite expecting bright future space materials for long term operation. Resistibility of these materials to the space environments were evaluated from the change of mechanical properties after exposure of electron, proton, atomic oxygen and thermal cycling. It was found that the CFRP with PMR-15 as a matrix had good performance in the space environments. No differences in the mechanical properties for the materials were observed between proton and electron irradiations. (author)

  18. To evaluate and compare the effect of different Post Surface treatments on the Tensile Bond Strength between Fiber Posts and Composite Resin.

    OpenAIRE

    Shori, Deepa; Pandey, Swapnil; Kubde, Rajesh; Rathod, Yogesh; Atara, Rahul; Rathi, Shravan

    2013-01-01

    Background: Fiber posts are widely used for restoration of mutilated teeth that lack adequate coronal tooth structure to retain a core for definitive restoration, bond between the fiber post and composite material depends upon the chemical reaction between the post surface and the resin material used for building up the core. In attempt to maximize the resin bonding with fiber post, different post surface conditioning is advocated. Therefore the purpose of the study is to examine the interfac...

  19. Bond Behavior of Wet-Bonded Carbon Fiber-Reinforced Polymer-Concrete Interface Subjected to Moisture

    OpenAIRE

    Yiyan Lu; Tao Zhu; Shan Li; Zhenzhen Liu

    2018-01-01

    The use of carbon fiber-reinforced polymer (CFRP) composite materials to strengthen concrete structures has become popular in coastal regions with high humidity levels. However, many concrete structures in these places remain wet as a result of tides and wave-splashing, so they cannot be completely dried before repair. Therefore, it is vital to investigate the effects of moisture on the initial and long-term bond behavior between CFRP and wet concrete. This research assesses the effects of mo...

  20. Development of Abaca Fiber-reinforced Foamed Fly Ash Geopolymer

    Directory of Open Access Journals (Sweden)

    Janne Pauline S. Ngo

    2018-01-01

    Full Text Available The growing environmental and economic concerns have led to the need for more sustainable construction materials. The development of foamed geopolymer combines the benefit of reduced environmental footprint and attractive properties of geopolymer technology with foam concrete’s advantages of being lightweight, insulating and energy-saving. In this study, alkali-treated abaca fiber-reinforced geopolymer composites foamed with H2O2 were developed using fly ash as the geopolymer precursor. The effects of abaca fiber loading, foaming agent dosage, and curing temperature on mechanical strength were evaluated using Box-Behken design of experiment with three points replicated. Volumetric weight of samples ranged from 1966 kg/m3 to 2249 kg/m3. Measured compressive strength and flexural ranged from 19.56 MPa to 36.84 MPa, and 2.41 MPa to 6.25 MPa, respectively. Results suggest enhancement of compressive strength by abaca reinforcement and elevated temperature curing. Results, however, indicate a strong interaction between curing temperature and foaming agent dosage, which observably caused the composite’s compressive strength to decline when simultaneously set at high levels. Foaming agent dosage was the only factor detected to significantly affect flexural strength.

  1. Effect of different composite core materials on fracture resistance of endodontically treated teeth restored with FRC posts

    OpenAIRE

    PANITIWAT, Prapaporn; SALIMEE, Prarom

    2017-01-01

    Abstract Objective This study evaluated the fracture resistance of endodontically treated teeth restored with fiber reinforced composite posts, using three resin composite core build-up materials, (Clearfil Photo Core (CPC), MultiCore Flow (MCF), and LuxaCore Z-Dual (LCZ)), and a nanohybrid composite, (Tetric N-Ceram (TNC)). Material and Methods Forty endodontically treated lower first premolars were restored with quartz fiber posts (D.T. Light-Post) cemented with resin cement (Panavia F2...

  2. Synthesis and Characterization of a Polyimide-Epoxy Composite for Dental Applications

    Science.gov (United States)

    Yang, An; Xu, Chun

    2018-03-01

    Epoxy (EP) resins have been employed in dentistry for years, but their intrinsic brittleness demands a reinforcement to make them an ideal dental material that combines strength, toughness, and aesthetics. In this study, an EP resin was reinforced with a low-molecular-weight polyimide (PI). The PI/EP composites were subjected to three-point bending tests and examined by the scanning electron microscopy. It was found that blending PI with EP in proper proportions strengthened EP without sacrificing its toughness. The PI/EP composite could be employed in dentistry as the matrix of fiber-reinforced dental root canal posts.

  3. Fast Cure Repair Kit for Composites, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA has a need for technologies that will enable them to repair damage to composite structures. Fiber-reinforced polymer composite materials are fast gaining ground...

  4. Radiation processing for PTFE composite reinforced with carbon fiber

    International Nuclear Information System (INIS)

    Akihiro Oshima; Akira Udagawa; Yousuke Morita

    1999-01-01

    The present work is an attempt to evaluate the performance of crosslinked PTFE as a polymer matrix for carbon fiber-reinforced composite materials. The carbon fiber-reinforced PTFE pre-composite, which is laminated with PTFE fine powder, is crosslinked by electron beam irradiation. Mechanical and frictional properties of the crosslinked PTFE composite obtained are higher than those of PTFE resin. The crosslinked PTFE composite with high mechanical and radiation resistant performance is obtained by radiation crosslinking process

  5. Post-impact performance of composites; Predicting Compression after Impact (CAI) in composite laminates

    NARCIS (Netherlands)

    Esrall, F.

    2013-01-01

    Impact damage has been known to seriously limit the performance of composite aircraft structures. In the preliminary design phase, tens of thousands of subparts need to be analyzed for impact. Over the years, many approaches have been proposed to study the creation of impact damage and to determine

  6. Enhanced Schapery Theory Software Development for Modeling Failure of Fiber-Reinforced Laminates

    Science.gov (United States)

    Pineda, Evan J.; Waas, Anthony M.

    2013-01-01

    Progressive damage and failure analysis (PDFA) tools are needed to predict the nonlinear response of advanced fiber-reinforced composite structures. Predictive tools should incorporate the underlying physics of the damage and failure mechanisms observed in the composite, and should utilize as few input parameters as possible. The purpose of the Enhanced Schapery Theory (EST) was to create a PDFA tool that operates in conjunction with a commercially available finite element (FE) code (Abaqus). The tool captures the physics of the damage and failure mechanisms that result in the nonlinear behavior of the material, and the failure methodology employed yields numerical results that are relatively insensitive to changes in the FE mesh. The EST code is written in Fortran and compiled into a static library that is linked to Abaqus. A Fortran Abaqus UMAT material subroutine is used to facilitate the communication between Abaqus and EST. A clear distinction between damage and failure is imposed. Damage mechanisms result in pre-peak nonlinearity in the stress strain curve. Four internal state variables (ISVs) are utilized to control the damage and failure degradation. All damage is said to result from matrix microdamage, and a single ISV marks the micro-damage evolution as it is used to degrade the transverse and shear moduli of the lamina using a set of experimentally obtainable matrix microdamage functions. Three separate failure ISVs are used to incorporate failure due to fiber breakage, mode I matrix cracking, and mode II matrix cracking. Failure initiation is determined using a failure criterion, and the evolution of these ISVs is controlled by a set of traction-separation laws. The traction separation laws are postulated such that the area under the curves is equal to the fracture toughness of the material associated with the corresponding failure mechanism. A characteristic finite element length is used to transform the traction-separation laws into stress-strain laws

  7. Polishing and coating carbon fiber-reinforced carbon composites with a carbon-titanium layer enhances adhesion and growth of osteoblast-like MG63 cells and vascular smooth muscle cells in vitro

    Czech Academy of Sciences Publication Activity Database

    Bačáková, Lucie; Starý, V.; Kofroňová, Olga; Lisá, Věra

    2001-01-01

    Roč. 54, č. 4 (2001), s. 567-578 ISSN 0021-9304 R&D Projects: GA ČR GA106/99/0626 Institutional research plan: CEZ:AV0Z5011922 Keywords : surface roughness * carbon particles * bone-derived cells Subject RIV: JI - Composite Materials Impact factor: 2.105, year: 2001

  8. Development of the experimental procedure to examine the response of carbon fiber-reinforced polymer composites subjected to a high-intensity pulsed electric field and low-velocity impact.

    Science.gov (United States)

    Hart, Robert J; Zhupanska, Olesya I

    2016-01-01

    A new fully automated experimental setup has been developed to study the response of carbon fiber reinforced polymer (CFRP) composites subjected to a high-intensity pulsed electric field and low-velocity impact. The experimental setup allows for real-time measurements of the pulsed electric current, voltage, impact load, and displacements on the CFRP composite specimens. The setup includes a new custom-built current pulse generator that utilizes a bank of capacitor modules capable of producing a 20 ms current pulse with an amplitude of up to 2500 A. The setup enabled application of the pulsed current and impact load and successfully achieved coordination between the peak of the current pulse and the peak of the impact load. A series of electrical, impact, and coordinated electrical-impact characterization tests were performed on 32-ply IM7/977-3 unidirectional CFRP composites to assess their ability to withstand application of a pulsed electric current and determine the effects of the pulsed current on the impact response. Experimental results revealed that the electrical resistance of CFRP composites decreased with an increase in the electric current magnitude. It was also found that the electrified CFRP specimens withstood higher average impact loads compared to the non-electrified specimens.

  9. Finite deformation of incompressible fiber-reinforced elastomers: A computational micromechanics approach

    Science.gov (United States)

    Moraleda, Joaquín; Segurado, Javier; LLorca, Javier

    2009-09-01

    The in-plane finite deformation of incompressible fiber-reinforced elastomers was studied using computational micromechanics. Composite microstructure was made up of a random and homogeneous dispersion of aligned rigid fibers within a hyperelastic matrix. Different matrices (Neo-Hookean and Gent), fibers (monodisperse or polydisperse, circular or elliptical section) and reinforcement volume fractions (10-40%) were analyzed through the finite element simulation of a representative volume element of the microstructure. A successive remeshing strategy was employed when necessary to reach the large deformation regime in which the evolution of the microstructure influences the effective properties. The simulations provided for the first time "quasi-exact" results of the in-plane finite deformation for this class of composites, which were used to assess the accuracy of the available homogenization estimates for incompressible hyperelastic composites.

  10. Fiber-Reinforced Origamic Robotic Actuator.

    Science.gov (United States)

    Yi, Juan; Chen, Xiaojiao; Song, Chaoyang; Wang, Zheng

    2018-02-01

    A novel pneumatic soft linear actuator Fiber-reinforced Origamic Robotic Actuator (FORA) is proposed with significant improvements on the popular McKibben-type actuators, offering nearly doubled motion range, substantially improved force profile, and significantly lower actuation pressure. The desirable feature set is made possible by a novel soft origamic chamber that expands radially while contracts axially when pressurized. Combining this new origamic chamber with a reinforcing fiber mesh, FORA generates very high traction force (over 150N) and very large contractile motion (over 50%) at very low input pressure (100 kPa). We developed quasi-static analytical models both to characterize the motion and forces and as guidelines for actuator design. Fabrication of FORA mostly involves consumer-grade three-dimensional (3D) printing. We provide a detailed list of materials and dimensions. Fabricated FORAs were tested on a dedicated platform against commercially available pneumatic artificial muscles from Shadow and Festo to showcase its superior performances and validate the analytical models with very good agreements. Finally, a robotic joint was developed driven by two antagonistic FORAs, to showcase the benefits of the performance improvements. With its simple structure, fully characterized mechanism, easy fabrication procedure, and highly desirable performance, FORA could be easily customized to application requirements and fabricated by anyone with access to a 3D printer. This will pave the way to the wider adaptation and application of soft robotic systems.

  11. Elevated temperature tensile and creep behavior of a SiC fiber-reinforced titanium metal matrix composite. Final Report, 22 Dec. 1994 M.S. Thesis, 7 May 1993

    Science.gov (United States)

    Thurston, Rita J.

    1995-01-01

    In this research program, the tensile properties and creep behavior in air of (0)(sub 4), (0/90)(sub s) and (90)(sub 4) SCS-9/Beta 21S composite layups with 0.24 volume fraction fiber were evaluated. Monotonic tensile tests at 23, 482, 650 and 815 C yielded the temperature dependence of the elastic modulus, proportional limit, ultimate tensile strength and total strain at failure. At 650 C, the UTS of the (0)(sub 4) and (0/90)(sub s) layups decreases by almost 50 percent from the room temperature values, indicating that operating temperatures should be less than 650 C to take advantage of the specific tensile properties of these composites.

  12. Post-Buckling and Ultimate Strength Analysis of Stiffened Composite Panel Base on Progressive Damage

    Science.gov (United States)

    Zhang, Guofan; Sun, Xiasheng; Sun, Zhonglei

    Stiffened composite panel is the typical thin wall structure applied in aerospace industry, and its main failure mode is buckling subjected to compressive loading. In this paper, the development of an analysis approach using Finite Element Method on post-buckling behavior of stiffened composite structures under compression was presented. Then, the numerical results of stiffened panel are obtained by FE simulations. A thorough comparison were accomplished by comparing the load carrying capacity and key position strains of the specimen with test. The comparison indicates that the FEM results which adopted developed methodology could meet the demand of engineering application in predicting the post-buckling behavior of intact stiffened structures in aircraft design stage.

  13. Manufacturability of Wood Plastic Composite Sheets on the Basis of the Post-Processing Cooling Curve

    Directory of Open Access Journals (Sweden)

    Sami Matthews

    2015-10-01

    Full Text Available Extruded wood-plastic composites (WPCs are increasingly regarded as promising materials for future manufacturing industries. It is necessary to select and tune the post-processing methods to be able to utilize these materials fully. In this development, temperature-related material properties and the cooling rate are important indicators. This paper presents the results of natural cooling in a factory environment fit into a cooling curve function with temperature zones for forming, cutting, and packaging overlaid using a WPC material. This information is then used in the evaluation of manufacturability and productivity in terms of cost effectiveness and technical quality by comparing the curve to actual production time data derived from a prototype post-process forming line. Based on this information, speed limits for extrusion are presented. This paper also briefly analyzes techniques for controlling material cooling to counter the heat loss before post-processing.

  14. Mechanical Behavior of Steel Fiber-Reinforced Concrete Beams Bonded with External Carbon Fiber Sheets.

    Science.gov (United States)

    Gribniak, Viktor; Tamulenas, Vytautas; Ng, Pui-Lam; Arnautov, Aleksandr K; Gudonis, Eugenijus; Misiunaite, Ieva

    2017-06-17

    This study investigates the mechanical behavior of steel fiber-reinforced concrete (SFRC) beams internally reinforced with steel bars and externally bonded with carbon fiber-reinforced polymer (CFRP) sheets fixed by adhesive and hybrid jointing techniques. In particular, attention is paid to the load resistance and failure modes of composite beams. The steel fibers were used to avoiding the rip-off failure of the concrete cover. The CFRP sheets were fixed to the concrete surface by epoxy adhesive as well as combined with various configurations of small-diameter steel pins for mechanical fastening to form a hybrid connection. Such hybrid jointing techniques were found to be particularly advantageous in avoiding brittle debonding failure, by promoting progressive failure within the hybrid joints. The use of CFRP sheets was also effective in suppressing the localization of the discrete cracks. The development of the crack pattern was monitored using the digital image correlation method. As revealed from the image analyses, with an appropriate layout of the steel pins, brittle failure of the concrete-carbon fiber interface could be effectively prevented. Inverse analysis of the moment-curvature diagrams was conducted, and it was found that a simplified tension-stiffening model with a constant residual stress level at 90% of the strength of the SFRC is adequate for numerically simulating the deformation behavior of beams up to the debonding of the CFRP sheets.

  15. Interface stresses in fiber-reinforced materials with regular fiber arrangements

    Science.gov (United States)

    Mueller, W. H.; Schmauder, S.

    The theory of linear elasticity is used here to analyze the stresses inside and at the surface of fiber-reinforced composites. Plane strain, plane stress, and generalized plane strain are analyzed using the shell model and the BHE model and are numerically studied using finite element analysis. Interface stresses are shown to depend weakly on Poisson's ratio. For equal values of the ratio, generalized plane strain and plane strain results are identical. For small volume fractions up to 40 vol pct of fibers, the shell and the BHE models predict the interface stresses very well over a wide range of elastic mismatches and for different fiber arrangements. At higher volume fractions the stresses are influenced by interactions with neighboring fibers. Introducing an external pressure into the shell model allows the prediction of interface stresses in real composite with isolated or regularly arranged fibers.

  16. Post-cure depth of cure of bulk fill dental resin-composites.

    Science.gov (United States)

    Alrahlah, A; Silikas, N; Watts, D C

    2014-02-01

    To determine the post-cure depth of cure of bulk fill resin composites through using Vickers hardness profiles (VHN). Five bulk fill composite materials were examined: Tetric EvoCeram(®) Bulk Fill, X-tra base, Venus(®) Bulk Fill, Filtek™ Bulk Fill, SonicFill™. Three specimens of each material type were prepared in stainless steel molds which contained a slot of dimensions (15 mm × 4 mm × 2 mm), and a top plate. The molds were irradiated from one end. All specimens were stored at 37°C for 24h, before measurement. The Vickers hardness was measured as a function of depth of material, at 0.3mm intervals. Data were analysed by one-way ANOVA using Tukey post hoc tests (α=0.05). The maximum VHN ranged from 37.8 to 77.4, whilst the VHN at 80% of max.VHN ranged from 30.4 to 61.9. The depth corresponding to 80% of max.VHN, ranged from 4.14 to 5.03 mm. One-way ANOVA showed statistically significant differences between materials for all parameters tested. SonicFill exhibited the highest VHN (pFill the lowest (p≤0.001). SonicFill and Tetric EvoCeram Bulk Fill had the greatest depth of cure (5.03 and 4.47 mm, respectively) and was significant's different from X-tra base, Venus Bulk Fill and Filtek Bulk Fill (p≤0.016). Linear regression confirmed a positive regression between max.VHN and filler loading (r(2)=0.94). Bulk fill resin composites can be cured to an acceptable post-cure depth, according to the manufacturers' claims. SonicFill and Tetric EvoCeram Bulk Fill had the greatest depth of cure among the composites examined. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  17. FRCM and FRP composites for the repair of damaged PC girders.

    Science.gov (United States)

    2015-01-01

    Fabric-reinforced-cementitious-matrix (FRCM) and fiber-reinforced polymer (FRP) composites have : emerged as novel strengthening technologies. FRCM is a composite material consisting of a sequence of : one or more layers of cement-based matrix reinfo...

  18. Environmental Degradation of Fiber-Reinforced Polymer Fasteners in Wood

    Science.gov (United States)

    Samuel L. Zelinka; Douglas R. Rammer

    2013-01-01

    This paper examines the durability of fiber-reinforced polymer (FRP) nails in treated wood. The FRP nails were exposed to four conditions: (1) accelerated weathering, consisting of exposure to ultraviolet light and condensation; (2) 100% relative humidity (RH); (3) being driven into untreated wood and exposed to 100% RH; and (4) being driven into wood treated with...

  19. Influence of post-casting treatments on sulphonated polyetheretherketone composite membranes

    Energy Technology Data Exchange (ETDEWEB)

    Carbone, Alessandra; Gatto, Irene; Passalacqua, Enza [CNR-ITAE, Institute for Advanced Energy Technologies ' ' N. Giordano' ' Via Salita S. Lucia sopra Contesse, 5 - Messina (Italy); Ohira, Akihiro; Wu, Libin [FC-CUBIC (Polymer Electrolyte Fuel Cell Cutting-Edge Research Center) AIST Tokyo Waterfront, 2-41-6, Aomi, Koto-ku, Tokyo 135-0064 (Japan)

    2010-09-15

    Since the post-casting treatments influence the water entrapped in polymeric matrix and consequently its proton conductivity, an evaluation of annealing at 200 C and acid treatments was conducted on previously developed composite s-PEEK (1.55 mequiv. g{sup -1}) membranes, containing a commercial aminopropyl-functionalised silica. DSC, WAXS, SEM-EDX and laser microscope measurements carried out on membranes swollen at different temperatures highlighted different membrane properties depending on post-casting treatments. It was found that composite membranes have different structural and morphological characteristics than pristine polymer membranes. The silica distribution was modified when different treatments are used. The state of water changed when silica was inserted into the membranes. Actually, contrary to the pristine membranes the presence of freezable water was revealed at temperature lower than 80 C. The proton conductivity was also affected by the presence and the amount of water trapped into the membranes and was particularly influenced by the post-casting treatments. The silica introduction reduced the swelling effect and improved the robustness of the membranes even if a higher water content in the freezable state was observed. Acid treatment leads to significant improvement in membrane properties, but the present work shows that annealing before acid treatment can affect the membrane morphology more strongly than other treatments resulting in a much better fuel cell performance. (author)

  20. Radiation-induced crosslinking and post-processing of poly(L-lactic acid) composite

    International Nuclear Information System (INIS)

    Nagasawa, Naotsugu; Kasai, Noboru; Yagi, Toshiaki; Yoshii, Fumio; Tamada, Masao

    2011-01-01

    Poly(L-lactic acid), PLLA, was irradiated using electron beams (EBs) in the presence of triallyl isocyanurate (TAIC) at 5% concentration as crosslinking agent. The crosslinked PLLA obtained has heat resistance, as demonstrated by retention of its original shape at glass transition temperature or even higher than 200 o C. As an application of this fact, crosslinked PLLA is applied in spectacle lens to prevent shape deformation of eyeglass frames in displaying and transporting. However, in this application to lens, it is not enough to improve the thermal deformation of PLLA under stress at 70 o C. Radiation-induced crosslinking of a PLLA/silicon dioxide (SiO 2 ) composite with TAIC and post-processing of the crosslinked PLLA composite by heating were further investigated from the viewpoint of thermal deformation. The PLLA materials have several advantages such as high heat resistance and transparency. It is therefore proved that the combination of radiation-induced crosslinking, composition of SiO 2 and post-heating is beneficial for expanding the applications of PLLA.

  1. Radiation-induced crosslinking and post-processing of poly(L-lactic acid) composite

    Energy Technology Data Exchange (ETDEWEB)

    Nagasawa, Naotsugu, E-mail: nagasawa.naotsugu@jaea.go.j [Japan Atomic Energy Agency (JAEA), Quantum Beam Science Directorate, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Kasai, Noboru; Yagi, Toshiaki; Yoshii, Fumio; Tamada, Masao [Japan Atomic Energy Agency (JAEA), Quantum Beam Science Directorate, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)

    2011-02-15

    Poly(L-lactic acid), PLLA, was irradiated using electron beams (EBs) in the presence of triallyl isocyanurate (TAIC) at 5% concentration as crosslinking agent. The crosslinked PLLA obtained has heat resistance, as demonstrated by retention of its original shape at glass transition temperature or even higher than 200 {sup o}C. As an application of this fact, crosslinked PLLA is applied in spectacle lens to prevent shape deformation of eyeglass frames in displaying and transporting. However, in this application to lens, it is not enough to improve the thermal deformation of PLLA under stress at 70 {sup o}C. Radiation-induced crosslinking of a PLLA/silicon dioxide (SiO{sub 2}) composite with TAIC and post-processing of the crosslinked PLLA composite by heating were further investigated from the viewpoint of thermal deformation. The PLLA materials have several advantages such as high heat resistance and transparency. It is therefore proved that the combination of radiation-induced crosslinking, composition of SiO{sub 2} and post-heating is beneficial for expanding the applications of PLLA.

  2. Effects of programmed physical activity on body composition in post-pubertal schoolchildren

    Directory of Open Access Journals (Sweden)

    Edson dos Santos Farias

    2015-04-01

    Full Text Available OBJECTIVE: To assess body composition modifications in post-pubertal schoolchildren after practice of a physical activity program during one school year. METHODS: The sample consisted of 386 students aged between 15 and 17 years and divided into two groups: the study group (SG comprised 195 students and the control group (CG, 191. The SG was submitted to a physical activity program and the CG attended conventional physical education classes. Body composition was assessed using body mass index (BMI, percentage of body fat (%BF, fat mass (FM, and lean mass (LM. RESULTS: A positive effect of the physical activity program on body composition in the SG (p < 0.001 was observed, as well as on the interaction time x group in all the variables analyzed in both genders. A reduction in %BF (mean of differences = -5.58% and waist circumference (-2.33 cm, as well as an increase in LM (+2.05 kg were observed in the SG for both genders, whereas the opposite was observed in the CG. CONCLUSION: The practice of programmed physical activity promotes significant reduction of body fat in post-pubertal schoolchildren.

  3. Effects of programmed physical activity on body composition in post-pubertal schoolchildren.

    Science.gov (United States)

    Farias, Edson Dos Santos; Gonçalves, Ezequiel Moreira; Morcillo, André Moreno; Guerra-Júnior, Gil; Amancio, Olga Maria Silverio

    2015-01-01

    To assess body composition modifications in post-pubertal schoolchildren after practice of a physical activity program during one school year. The sample consisted of 386 students aged between 15 and 17 years and divided into two groups: the study group (SG) comprised 195 students and the control group (CG), 191. The SG was submitted to a physical activity program and the CG attended conventional physical education classes. Body composition was assessed using body mass index (BMI), percentage of body fat (%BF), fat mass (FM), and lean mass (LM). A positive effect of the physical activity program on body composition in the SG (pgenders. A reduction in %BF (mean of differences = -5.58%) and waist circumference (-2.33 cm), as well as an increase in LM (+2.05 kg) were observed in the SG for both genders, whereas the opposite was observed in the CG. The practice of programmed physical activity promotes significant reduction of body fat in post-pubertal schoolchildren. Copyright © 2013 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.

  4. Carriers' localization and thermal redistribution in post growth voluntarily tuned quantum dashes' size/composition distribution

    International Nuclear Information System (INIS)

    Alouane, M.H. Hadj; Helali, A.; Morris, D.; Maaref, H.; Aimez, V.; Salem, B.; Gendry, M.

    2014-01-01

    This paper treats the impact of post growth tuned InAs/InP quantum dashes' (QDas) size/composition distribution on carriers' localization and thermal redistribution. The spread of this distribution depends on the experimental conditions used for the phosphorus ion implantation enhanced intermixing process. Atypical temperature-dependent luminescence properties have been observed and found to be strongly dependent on the amount of QDas size/composition dispersion. The experimental results have been reproduced by a model that takes into account the width of the QDas localized states distribution and consequent thermally induced carriers' redistribution. This model gives critical temperature values marking the beginning and the end of carriers delocalization and thermal transfer processes via an intermixing induced carrier's transfer channel located below the wetting layer states. -- Highlights: • We examine optical properties of post growth tuned QDas size/composition distribution. • Carriers' localization and thermal redistribution within inhomogeneously intermixed QDas are the origin of the atypical temperature-dependent luminescence properties. • Localized states ensemble's model is successively used to interpret the experimental results. • The carriers thermal transfer processes occur via an intermixing induced channel located below the wetting layer states. • Intermixing degree strongly influence the critical temperatures marking the beginning and the end of the carriers thermal transfer processes

  5. Investigation of Active Tagged Composites for Army Infrastructure Applications

    National Research Council Canada - National Science Library

    Berman, J

    1998-01-01

    .... Advanced composites, such as fiber-reinforced plastics (FRP), can eliminate many problems related to steel reinforcement because of their excellent fatigue resistance, corrosion resistance, and their very high specific strength...

  6. Influence of body composition on physiological responses to post-exercise hydrotherapy.

    Science.gov (United States)

    Stephens, Jessica M; Halson, Shona L; Miller, Joanna; Slater, Gary J; Askew, Christopher D

    2018-05-01

    This study examined the influence of body composition on temperature and blood flow responses to post-exercise cold water immersion (CWI), hot water immersion (HWI) and control (CON). Twenty-seven male participants were stratified into three groups: 1) low mass and low fat (LM-LF); 2) high mass and low fat (HM-LF); or 3) high mass and high fat (HM-HF). Experimental trials involved a standardised bout of cycling, maintained until core temperature reached 38.5°C. Participants subsequently completed one of three 15-min recovery interventions (CWI, HWI, or CON). Core, skin and muscle temperatures, and limb blood flow were recorded at baseline, post-exercise, and every 30 min following recovery for 240 min. During CON and HWI there were no differences in core or muscle temperature between body composition groups. The rate of fall in core temperature following CWI was greater in the LM-LF (0.03 ± 0.01°C/min) group compared to the HM-HF (0.01 ± 0.001°C/min) group (P = 0.002). Muscle temperature decreased to a greater extent during CWI in the LM-LF and HM-LF groups (8.6 ± 3.0°C) compared with HM-HF (5.1 ± 2.0°C, P < 0.05). Blood flow responses did not differ between groups. Differences in body composition alter the thermal response to post-exercise CWI, which may explain some of the variance in the responses to CWI recovery.

  7. Fibre reinforced composites '84; Proceedings of the International Conference, University of Liverpool, England, April 3-5, 1984

    Energy Technology Data Exchange (ETDEWEB)

    1984-01-01

    Among the topics discussed are phenolic resin matrix composites for high temperature and fire-exposure applications, novel resins for fiber-reinforced composite productivity improvement, the use of engineering textiles for mechanical property improvement in composites, the significance of aramid fiber reinforcement in composites, the energy absorption properties of Sheet Metal Compounds (SMCs) under crash conditions, and SMC impact behavior variations with temperature. Also covered are CFRP applications in high performance structures, composite helicopter main rotor blade technology, composite vehicular leaf springs, carbon fiber-reinforced thermoplastics, filament winding development status, the injection processing of fiber-reinforced thermoplastics, civil aircraft composite structure certification, composite radomes, design procedures for short fiber-reinforced thermoplastics, the strength limitations of mechanically fastened lap joints, environmental fatigue and creep in glass-reinforced materials, the effects of moisture on high performance laminates, the environmental behavior of SMC, and corrugated composites.

  8. Change in the structure and properties of carbon fiber-reinforced plastic with a polysulfone matrix under the effect of gamma irradiation

    International Nuclear Information System (INIS)

    Arkhipov, A.A.; Korkhov, V.P.; Pudnik, V.V.; Rodin, Yu.P.

    1993-01-01

    This article presents the results of studying the change in the structure and properties of carbon fiber-reinforced plastic with a thermoplastic matrix -- aromatic polysulfone -- as a function of the absorbed dose of gamma radiation. In view of the presence in the polysulfone macromolecules and in carbon fibers of a large number of aromatic rings and double bonds providing high radiation resistance of the composite, irradiation was carried out up to large values of absorbed doses (10 9 rad). Specimens of orthogonally reinforced composite KTMU-1 with a thickness of 1.3 mm made from aromatic polysulfone PSF-150 and carbon ribbon that absorbed various gamma radiation dosages were used. It was found that structural transformations under the effect of gamma radiation did not have a substantial effect on the mechanical properties of carbon fiber-reinforced plastic. 2 refs., 3 figs., 3 tabs

  9. In Vitro Evaluation of Various Surface Treatments of Fiber Posts on the Bond Strength to Composite Core

    Directory of Open Access Journals (Sweden)

    Sareh Nadalizadeh

    Full Text Available Introduction: The reliable bond at the root-post-core interface is critical for the clinical success of post-retained restorations. To decrease the risk of fracture, it is important to optimize the adhesion. Therefore, various post surface treatments have been proposed. The purpose of this study was to investigate the influence of various surface treatments of fiber posts on the bond strength to composite core. Materials & Methods: In this study, 40 fiber reinforced posts were used. After preparing and sectioning them, resulting specimens were divided into four groups (N=28. The posts received different surface treatments such as no surface treatment (control group, preparing with hydrogen peroxide 10%, preparing with silane, preparing with HF and silane. Then, posts were tested in micro tensile testing machine. The results were analyzed by One-Way ANOVA and Dunnett T3 test. Results: The greatest bond strength observed was in treatment with hydrogen peroxide 10% (19.84±8.95 MPa, and the lowest strength was related to the control group (12.44±3.40 MPa. The comparison of the groups with Dunnett T3 test showed that the differences between the groups was statistically significant (α=0.05.Conclusion: Based on the results of this study, preparing with H2O2 -10 % and silane increases the bond strength of FRC posts to the composite core more than the other methods. Generally, the bond strength of posts to the composite core increases by surface treatment.

  10. Partial elastodynamic cloaking by means of fiber-reinforced composites

    International Nuclear Information System (INIS)

    Olsson, P; Wall, David J N

    2011-01-01

    In this paper, we show that if inextensible fibers are embedded in an elastic material (or the material is by some other means made considerably stiffer in a particular but possibly variable direction), one may obtain equations of motion which are form invariant under certain diffeomorphism, allowing for partial cloaking (or 'illusion optics') schemes in both 2D and 3D. The schemes are valid at all frequencies without requiring any active material properties, and will thus work in the time domain without requiring active materials. While being mathematically exact at all frequencies, the applicability is of course limited to where the continuum approximation holds. Additional limits, set by idealization in the modeling of fibers and core material, are also present. However, contrary to some other approaches, the solution does not require metamaterials with non-scalar mass densities, nor does it require the breaking of the supersymmetry of the elasticity tensor

  11. Partial elastodynamic cloaking by means of fiber-reinforced composites

    Science.gov (United States)

    Olsson, P.; Wall, David J. N.

    2011-04-01

    In this paper, we show that if inextensible fibers are embedded in an elastic material (or the material is by some other means made considerably stiffer in a particular but possibly variable direction), one may obtain equations of motion which are form invariant under certain diffeomorphism, allowing for partial cloaking (or 'illusion optics') schemes in both 2D and 3D. The schemes are valid at all frequencies without requiring any active material properties, and will thus work in the time domain without requiring active materials. While being mathematically exact at all frequencies, the applicability is of course limited to where the continuum approximation holds. Additional limits, set by idealization in the modeling of fibers and core material, are also present. However, contrary to some other approaches, the solution does not require metamaterials with non-scalar mass densities, nor does it require the breaking of the supersymmetry of the elasticity tensor.

  12. Continuous Fiber Ceramic Composites

    Energy Technology Data Exchange (ETDEWEB)

    Fareed, Ali [Honeywell Advanced Composites Inc. (HACI), Newark, DE (United States); Craig, Phillip A. [Honeywell Advanced Composites Inc. (HACI), Newark, DE (United States)

    2002-09-01

    Fiber-reinforced ceramic composites demonstrate the high-temperature stability of ceramics--with an increased fracture toughness resulting from the fiber reinforcement of the composite. The material optimization performed under the continuous fiber ceramic composites (CFCC) included a series of systematic optimizations. The overall goals were to define the processing window, to increase the robustinous of the process, to increase process yield while reducing costs, and to define the complexity of parts that could be fabricated.

  13. Properties of Fiber-Reinforced Mortars Incorporating Nano-Silica

    OpenAIRE

    Ahmed Ghazy; Mohamed T. Bassuoni; Eugene Maguire; Mark O’Loan

    2016-01-01

    Repair and rehabilitation of deteriorating concrete elements are of significant concern in many infrastructural facilities and remain a challenging task. Concerted research efforts are needed to develop repair materials that are sustainable, durable, and cost-effective. Research data show that fiber-reinforced mortars/concretes have superior performance in terms of volume stability and toughness. In addition, it has been recently reported that nano-silica particles can generally improve the m...

  14. Engineering Properties of Treated Natural Hemp Fiber-Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Xiangming Zhou

    2017-06-01

    Full Text Available In recent years, the construction industry has seen a significant rise in the use of natural fibers, for producing building materials. Research has shown that treated hemp fiber-reinforced concrete (THFRC can provide a low-cost building material for residential and low-rise buildings, while achieving sustainable construction and meeting future environmental targets. This study involved enhancing the mechanical properties of hemp fiber-reinforced concrete through the Ca(OH2 solution pretreatment of fibers. Both untreated (UHFRC and treated (THFRC hemp fiber-reinforced concrete were tested containing 15-mm length fiber, at a volume fraction of 1%. From the mechanical strength tests, it was observed that the 28-day tensile and compressive strength of THFRC was 16.9 and 10% higher, respectively, than UHFRC. Based on the critical stress intensity factor (KICs and critical strain energy release rate (GICs, the fracture toughness of THFRC at 28 days was also found to be 7–13% higher than UHFRC. Additionally, based on the determined brittleness number (Q and modulus of elasticity, the THFRC was found to be 11% less brittle and 10.8% more ductile. Furthermore, qualitative analysis supported many of the mechanical strength findings through favorable surface roughness observed on treated fibers and resistance to fiber pull-out.

  15. Fracture resistance of upper central incisors restored with different posts and cores

    Directory of Open Access Journals (Sweden)

    Maryam Rezaei Dastjerdi

    2015-08-01

    Full Text Available Objectives To determine and compare the fracture resistance of endodontically treated maxillary central incisors restored with different posts and cores. Materials and Methods Forty-eight upper central incisors were randomly divided into four groups: cast post and core (group 1, fiber-reinforced composite (FRC post and composite core (group 2, composite post and core (group 3, and controls (group 4. Mesio-distal and bucco-lingual dimensions at 7 and 14 mm from the apex were compared to ensure standardization among the groups. Twelve teeth were prepared for crown restoration (group 4. Teeth in other groups were endodontically treated, decoronated at 14 mm from the apex, and prepared for posts and cores. Resin-based materials were used for cementation in groups 1 and 2. In group 3, composite was used directly to fill the post space and for core build-up. All samples were restored by standard metal crowns using glass ionomer cement, mounted at 135° vertical angle, subjected to thermomechanical aging, and then fractured using a universal testing machine. Kruskal-Wallis and Mann-Whitney U tests were used to analyze the data. Results Fracture resistance of the groups was as follows: Control (group 4 > cast post and core (group 1 > fiber post and composite core (group 2 > composite post and core (group 3. All samples in groups 2 and 3 fractured in restorable patterns, whereas most (58% in group 1 were non-restorable. Conclusions Within the limitations of this study, FRC posts showed acceptable fracture resistance with favorable fracture patterns for reconstruction of upper central incisors.

  16. Enhanced Performance of Thin Film Composite Forward Osmosis Membrane by Chemical Post-Treatment

    Science.gov (United States)

    Liu, Zheng; Chen, Jiangrong; Cao, Zhen; Wang, Jian; Guo, Chungang

    2018-01-01

    Forward osmosis is an attractive technique in water purification and desalination fields. Enhancement of the forward osmosis membrane performance is essential to the application of this technique. In this study, an optimized chemical post-treatment approach which was used to improve RO membrane performance was employed for enhancing water flux of thin film composite forward osmosis membrane. Home-made polysulfide-based forward osmosis membrane was prepared and nitric acid, sulfuric acid, ethanol, 2-propanol were employed as post-treatment solutions. After a short-term treatment, all the membrane samples manifested water flux enhancement compared with their untreated counterparts. Over 50% increase of water flux had been obtained by ethanol solution treatment. The swelling, changes of hydrophobicity and solvency in both active layer and substrate were verified as the major causes for the enhancement of the water flux. It is noted that the treatment time and solution concentration should be controlled to get both appropriate water flux and reverse salt flux. The results obtained in this study will be useful for further FO membrane development and application.

  17. Improving reconstituted HDL composition for efficient post-ischemic reduction of ischemia reperfusion injury.

    Directory of Open Access Journals (Sweden)

    Marie-Claude Brulhart-Meynet

    Full Text Available New evidence shows that high density lipoproteins (HDL have protective effects beyond their role in reverse cholesterol transport. Reconstituted HDL (rHDL offer an attractive means of clinically exploiting these novel effects including cardioprotection against ischemia reperfusion injury (IRI. However, basic rHDL composition is limited to apolipoprotein AI (apoAI and phospholipids; addition of bioactive compound may enhance its beneficial effects.The aim of this study was to investigate the role of rHDL in post-ischemic model, and to analyze the potential impact of sphingosine-1-phosphate (S1P in rHDL formulations.The impact of HDL on IRI was investigated using complementary in vivo, ex vivo and in vitro IRI models. Acute post-ischemic treatment with native HDL significantly reduced infarct size and cell death in the ex vivo, isolated heart (Langendorff model and the in vivo model (-48%, p<0.01. Treatment with rHDL of basic formulation (apoAI + phospholipids had a non-significant impact on cell death in vitro and on the infarct size ex vivo and in vivo. In contrast, rHDL containing S1P had a highly significant, protective influence ex vivo, and in vivo (-50%, p<0.01. This impact was comparable with the effects observed with native HDL. Pro-survival signaling proteins, Akt, STAT3 and ERK1/2 were similarly activated by HDL and rHDL containing S1P both in vitro (isolated cardiomyocytes and in vivo.HDL afford protection against IRI in a clinically relevant model (post-ischemia. rHDL is significantly protective if supplemented with S1P. The protective impact of HDL appears to target directly the cardiomyocyte.

  18. Bench Scale Thin Film Composite Hollow Fiber Membranes for Post-Combustion Carbon Dioxide Capture

    Energy Technology Data Exchange (ETDEWEB)

    Glaser, Paul [General Electric Global Research, Niskayuna, NY (United States); Bhandari, Dhaval [General Electric Global Research, Niskayuna, NY (United States); Narang, Kristi [General Electric Global Research, Niskayuna, NY (United States); McCloskey, Pat [General Electric Global Research, Niskayuna, NY (United States); Singh, Surinder [General Electric Global Research, Niskayuna, NY (United States); Ananthasayanam, Balajee [General Electric Global Research, Niskayuna, NY (United States); Howson, Paul [General Electric Global Research, Niskayuna, NY (United States); Lee, Julia [General Electric Global Research, Niskayuna, NY (United States); Wroczynski, Ron [General Electric Global Research, Niskayuna, NY (United States); Stewart, Frederick [Idaho National Lab. (INL), Idaho Falls, ID (United States); Orme, Christopher [Idaho National Lab. (INL), Idaho Falls, ID (United States); Klaehn, John [Idaho National Lab. (INL), Idaho Falls, ID (United States); McNally, Joshua [Idaho National Lab. (INL), Idaho Falls, ID (United States); Rownaghi, Ali [Georgia Inst. of Technology, Atlanta, GA (United States); Lu, Liu [Georgia Inst. of Technology, Atlanta, GA (United States); Koros, William [Georgia Inst. of Technology, Atlanta, GA (United States); Goizueta, Roberto [Georgia Inst. of Technology, Atlanta, GA (United States); Sethi, Vijay [Western Research Inst., Laramie, WY (United States)

    2015-04-01

    GE Global Research, Idaho National Laboratory (INL), Georgia Institute of Technology (Georgia Tech), and Western Research Institute (WRI) proposed to develop high performance thin film polymer composite hollow fiber membranes and advanced processes for economical post-combustion carbon dioxide (CO2) capture from pulverized coal flue gas at temperatures typical of existing flue gas cleanup processes. The project sought to develop and then optimize new gas separations membrane systems at the bench scale, including tuning the properties of a novel polyphosphazene polymer in a coating solution and fabricating highly engineered porous hollow fiber supports. The project also sought to define the processes needed to coat the fiber support to manufacture composite hollow fiber membranes with high performance, ultra-thin separation layers. Physical, chemical, and mechanical stability of the materials (individual and composite) towards coal flue gas components was considered via exposure and performance tests. Preliminary design, technoeconomic, and economic feasibility analyses were conducted to evaluate the overall performance and impact of the process on the cost of electricity (COE) for a coal-fired plant including capture technologies. At the onset of the project, Membranes based on coupling a novel selective material polyphosphazene with an engineered hollow fiber support was found to have the potential to capture greater than 90% of the CO2 in flue gas with less than 35% increase in COE, which would achieve the DOE-targeted performance criteria. While lab-scale results for the polyphosphazene materials were very promising, and the material was incorporated into hollow-fiber modules, difficulties were encountered relating to the performance of these membrane systems over time. Performance, as measured by both flux of and selectivity for CO2 over other flue gas constituents was found to deteriorate over time, suggesting a system that was

  19. Evolution of post-ESWL residual lithiasis depending on the type of calculus and urine composition.

    Science.gov (United States)

    Grases, Felix; Costa-Bauzá, Antonia; Isern, Bernat; Sanchis, Pilar; Perelló, Joan; Hierro, Fernando; Conte Visus, Antonio

    2009-07-01

    Extracorporeal shock wave lithotripsy (ESWL) is one of the most commonly used procedures for removal of renal calculi from the upper urinary tract, but complete expulsion of the fragments generated is not always achieved. This can lead to new lithiasic episodes, and it is considered that 10-26% of fragmented calculi can undergo regrowth. This in vitro study investigated the influence of fragment and urinary composition on post-ESWL growth of fragments, with the aims of establishing the effect and importance of these parameters, and identifying effective prophylactic measures. Fragments collected from patients immediately following expulsion after ESWL treatment were selected for regrowth experiments. The particles included 24 calcium oxalate monohydrate (COM) fragments, 48 calcium oxalate dihydrate (COD), 24 hydroxyapatite (HAP), and 16 uric acid. In all treatments, calculi fragments showed a considerable capacity to induce growth of calcium oxalate and calcium phosphate. Under normocalciuria conditions, new COM crystals formed; both COM and COD crystals developed under hypercalciuria conditions at a urinary pH 6.0 both HAP and brushite (BRU) crystals were formed. The highest growth rates were observed for COD calculi fragments under hypercalciuria conditions and at a urinary pH of 6.5, followed by growth on COM and HAP fragments under the same conditions; growth rates under other conditions tested were similar but 10-fold lower. With regard to the role of crystallization inhibitors, phytate exhibited inhibitory effects under all assay conditions. However, citrate had little effect, even at the highest concentration tested (1,000 mg/L). This study demonstrates the importance of avoiding heterogeneous nucleant retention (pre-existing solid microparticles) in renal cavities, as these can act as very efficient inducers of the formation of new calculi, the composition of which is mainly dependant on the urine composition.

  20. Preoperative body size and composition, habitual diet, and post-operative complications in elective colorectal cancer patients in Norway.

    Science.gov (United States)

    Berstad, P; Haugum, B; Helgeland, M; Bukholm, I; Almendingen, K

    2013-08-01

    Both malnutrition and obesity are related to worsened post-operative outcomes after colorectal surgery. Obese cancer patients may be malnourished as a result of short-term weight loss. The present study aimed to evaluate preoperative nutritional status, body composition and dietary intake related to post-operative complications (POC) and post-operative hospital days (POHD) in elective colorectal cancer (CRC) patients. Anthropometry, body composition measured by bioelectric spectroscopy and dietary habits assessed by a validated food-frequency questionnaire were examined in 100 newly-diagnosed CRC patients. Data from 30-day POC and POHD were collected from medical records. Nonparametric and chi-squared tests and logistic regression were used to analyse associations between body and dietary variables and post-operative outcome. Twenty-nine patients had at least one POC. The median POHD was six. Body size and composition measures and short-term weight loss were no different between patients with and without POC, or between patients with POHD body size, body composition and short-term weight loss were not related to 30-day post-operative outcomes in CRC patients. A high content of marine n-3 PUFA in preoperative habitual diets may protect against POC after CRC surgery. © 2012 The Authors Journal of Human Nutrition and Dietetics © 2012 The British Dietetic Association Ltd.

  1. Assessment of the post-impact damage propagation in a carbon-fibre composite under cyclic loading

    Czech Academy of Sciences Publication Activity Database

    Kytýř, Daniel; Fíla, T.; Šleichrt, J.; Doktor, Tomáš; Šperl, Martin

    2014-01-01

    Roč. 48, č. 5 (2014), s. 777-780 ISSN 1580-2949 R&D Projects: GA TA ČR(CZ) TA03010209 Institutional support: RVO:68378297 Keywords : carbon-fibre composites * post-impact damage * laser profilometry Subject RIV: JI - Composite Materials Impact factor: 0.548, year: 2014 http://mit.imt.si/Revija/izvodi/mit145/kytyr.pdf

  2. Buckling Modes of Structural Elements of Off-Axis Fiber-Reinforced Plastics

    Science.gov (United States)

    Paimushin, V. N.; Polyakova, N. V.; Kholmogorov, S. A.; Shishov, M. A.

    2018-05-01

    The structures of two types of unidirectional fiber-reinforced composites — with an ELUR-P carbon fiber tape, an XT-118 cold-cure binder with an HSE 180 REM prepreg, and a hot-cure binder — were investigated. The diameters of fibers and fiber bundles (threads) of both the types of composites were measured, and their mutual arrangement was examined both in the semifinished products (in the uncured state) and in the finished composites. The defects characteristic of both the types of binder and manufacturing technique were detected in the cured composites. Based on an analysis of the results obtained, linearized problems on the internal multiscale buckling modes of an individual fiber (with and without account of its interaction with the surrounding matrix) or of a fiber bundle are formulated. In the initial atate, these structural elements of the fibrous composites are in a subcritical (unperturbed) state under the action of shear stresses and tension (compression) in the transverse direction. Such an initial stress state is formed in them in tension and compression tests on flat specimens made of off-axis-reinforced composites with straight fibers. To formulate the problems, the equations derived earlier from a consistent variant of geometrically nonlinear equations of elasticity theory by reducing them to the one-dimensional equations of the theory of straight rods on the basis of a refined Timoshenko shear model with account of tensile-compressive strains in the transverse direction are used. It is shown that, in loading test specimens, a continuous rearrangement of composite structure can occur due to the realization and continuous change of internal buckling modes as the wave-formation parameter varies continuously, which apparently explain the decrease revealed in the tangential shear modulus of the fibrous composites with increasing shear strains.

  3. Effect of length and diameter of fiber reinforced composite post (FRC on fracture resistance of remaining tooth structure

    Directory of Open Access Journals (Sweden)

    Mahdiyeh seifi

    2013-03-01

    Full Text Available Introduction: Post and core has been considered for endodontically treated tooth, especially in cases with severe damage crowns. Recently fiber reinforced composite posts (FRC post have been used in the treatment of endodontically treated teeth. Because the length and diameter of posts are effective in stress distribution, the purpose of this study is to evaluate the effect of length and diameter of FRC post on fracture resistance. Methods: In this experimental study, 36 glass fiber posts with combination of 7mm, 9mm, and 12mm length and 1.1mm, 1.3mm and 1.5mm diameter were divided into 9 groups of 4. These posts were cemented in root canals by Panavia. Samples were tested with 45° compressive forces for the evaluation of fracture resistance. Datas were analyzed using SPSS soft ware and One- way and Two-way ANOVA analyses. Results: Fracture resistance did not increase significantly with the effect of length and diameter simultaneously (P=0.85. Samples with 12mm length and 1.5mm diameter had the greatest fracture resistance (1023/33N±239/22. The minimum fracture resistance had occurred in post with 7mm length and 1.5mm diameter (503/13N ±69/18. Fracture resistance increased significantly by increasing the length and the same diameter. Conclusion: It can be concluded that fracture resistance is affected by the length and not the diameter of FRC post.

  4. Mild hypothermic culture conditions affect residual host cell protein composition post-Protein A chromatography.

    Science.gov (United States)

    Goey, Cher Hui; Bell, David; Kontoravdi, Cleo

    2018-04-01

    Host cell proteins (HCPs) are endogenous impurities, and their proteolytic and binding properties can compromise the integrity, and, hence, the stability and efficacy of recombinant therapeutic proteins such as monoclonal antibodies (mAbs). Nonetheless, purification of mAbs currently presents a challenge because they often co-elute with certain HCP species during the capture step of protein A affinity chromatography. A Quality-by-Design (QbD) strategy to overcome this challenge involves identifying residual HCPs and tracing their source to the harvested cell culture fluid (HCCF) and the corresponding cell culture operating parameters. Then, problematic HCPs in HCCF may be reduced by cell engineering or culture process optimization. Here, we present experimental results linking cell culture temperature and post-protein A residual HCP profile. We had previously reported that Chinese hamster ovary cell cultures conducted at standard physiological temperature and with a shift to mild hypothermia on day 5 produced HCCF of comparable product titer and HCP concentration, but with considerably different HCP composition. In this study, we show that differences in HCP variety at harvest cascaded to downstream purification where different residual HCPs were present in the two sets of samples post-protein A purification. To detect low-abundant residual HCPs, we designed a looping liquid chromatography-mass spectrometry method with continuous expansion of a preferred, exclude, and targeted peptide list. Mild hypothermic cultures produced 20% more residual HCP species, especially cell membrane proteins, distinct from the control. Critically, we identified that half of the potentially immunogenic residual HCP species were different between the two sets of samples.

  5. A resin composite material containing an eugenol derivative for intracanal post cementation and core build-up restoration.

    Science.gov (United States)

    Almaroof, A; Rojo, L; Mannocci, F; Deb, S

    2016-02-01

    To formulate and evaluate new dual cured resin composite based on the inclusion of eugenyl methacrylate monomer (EgMA) with Bis-GMA/TEGDMA resin systems for intracanal post cementation and core build-up restoration of endodontically treated teeth. EgMA was synthesized and incorporated at 5% (BTEg5) or 10% (BTEg10) into dual-cure formulations. Curing properties, viscosity, Tg, radiopacity, static and dynamic mechanical properties of the composites were determined and compared with Clearfil™DC Core-Plus, a commercial dual-cure, two-component composite. Statistical analysis of the data was performed with ANOVA and the Tukey's post-hoc test. The experimental composites were successfully prepared, which exhibited excellent curing depths of 4.9, 4.7 and 4.2 mm for BTEg0, BTEg5 and BTEg10 respectively, which were significantly higher than Clearfil™DC. However, the inclusion of EgMA initially led to a lower degree of cure, which increased when measured at 24 h with values comparable to formulations without EgMA, indicating post-curing. The inclusion of EgMA also lowered the polymerization exotherm thereby reducing the potential of thermal damage to host tissue. Both thermal and viscoelastic analyses confirmed the ability of the monomer to reduce the stiffness of the composites by forming a branched network. The compressive strength of BTEg5 was significantly higher than the control whilst flexural strength increased significantly from 95.9 to 114.8 MPa (BTEg5) and 121.9 MPa (BTEg10). Radiopacity of the composites was equivalent to ∼3 mm Al allowing efficient diagnosis. The incorporation of EgMA within polymerizable formulations provides a novel approach to prepare reinforced resin composite material for intracanal post cementation and core build-up and the potential to impart antibacterial properties of eugenol to endodontic restorations. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  6. A Hybrid Approach to Composite Damage and Failure Analysis Combining Synergistic Damage Mechanics and Peridynamics

    Science.gov (United States)

    2017-03-30

    manufacturing defects in the intermediately -homogenized model of fiber-reinforced composites. 15. SUBJECT TERMS Computational micromechanics; Cavitation...defects in the intermediately -homogenized model of fiber-reinforced composites. Task 1.1 Micro-level crack initiation Background and motivation In...new Intermediate Homogenization Peridynamic approach (IH-PD model) for failure in multiphase materials. We plan to apply this IH-PD model for the

  7. Woodland caribou calf recruitment in relation to calving/post-calving landscape composition

    Directory of Open Access Journals (Sweden)

    Sara C. McCarthy

    2011-04-01

    Full Text Available Since the 1990s, Newfoundland’s woodland caribou (Rangifer tarandus caribou population has declined by an estimated 66%. Low calf recruitment has been associated to the decline, possibly triggered by increasing calf predation and/or decreasing resources. To investigate the role of landscape composition in this system, we studied the yearly (2005-2008 calving/post-calving range (CPCR of 104 satellite-collared females belonging to six herds. We mapped nine disturbance factors (e.g. roads, logging, etc, as well as vegetation cover types (e.g. coniferous, deciduous forests, etc, and determined the total area they occupied within CPCRs yearly for each herd. Using an information theoretic approach, we assessed the model that best explained variation in recruitment using these components. Based on corrected Akaike Information Criterion, the model that best explained variation in calf recruitment included total disturbance and deciduous forest area, both showing the expected negative relationship with calf recruitment. Other landscape variables among the models with ΔAICc < 2 were mixed forest, also with a suggested negative relationship, and barrens and wetlands with a significant positive trend. This study highlights the need to minimize total disturbance footprint and account for resulting changes in forest composition within CPCRs during land use planning. Expanding forestry operations and road infrastructure in critical woodland caribou habitat across Canada may additionally contribute to habitat loss via fragmentation. This in turn, may lead to range recession beyond the initial local avoidance footprint. We see the possibility of using calf recruitment models based on landscape parameters, among others, to predict the impact of new industrial developments on calf recruitment.

  8. Ex vivo fracture resistance of direct resin composite complete crowns with and without posts on maxillary premolars.

    NARCIS (Netherlands)

    Fokkinga, W.A.; Bell, A.M. Le; Kreulen, C.M.; Lassila, L.V.; Vallittu, P.K.; Creugers, N.H.J.

    2005-01-01

    AIM: To investigate ex vivo the fracture resistance and failure mode of direct resin composite complete crowns with and without various root canal posts made on maxillary premolars. METHODOLOGY: The clinical crowns of 40 human extracted single-rooted maxillary premolars were sectioned at the

  9. Effect of different composite core materials on fracture resistance of endodontically treated teeth restored with FRC posts.

    Science.gov (United States)

    Panitiwat, Prapaporn; Salimee, Prarom

    2017-01-01

    This study evaluated the fracture resistance of endodontically treated teeth restored with fiber reinforced composite posts, using three resin composite core build-up materials, (Clearfil Photo Core (CPC), MultiCore Flow (MCF), and LuxaCore Z-Dual (LCZ)), and a nanohybrid composite, (Tetric N-Ceram (TNC)). Forty endodontically treated lower first premolars were restored with quartz fiber posts (D.T. Light-Post) cemented with resin cement (Panavia F2.0). Samples were randomly divided into four groups (n=10). Each group was built-up with one of the four core materials following its manufacturers' instructions. The teeth were embedded in acrylic resin blocks. Nickel-Chromium crowns were fixed on the specimens with resin cement. The fracture resistance was determined using a universal testing machine with a crosshead speed of 1 mm/min at 1350 to the tooth axis until failure occurred. All core materials used in the study were subjected to test for the flexural modulus according to ISO 4049:2009. One-way ANOVA and Bonferroni multiple comparisons test indicated that the fracture resistance was higher in the groups with CPC and MCF, which presented no statistically significant difference (p>0.05), but was significantly higher than in those with LCZ and TNC (paligned with the same tendency of fracture loads. Among the cores used in this study, the composite core with high filler content tended to enhance fracture thresholds of teeth restored with fiber posts more than others.

  10. Suppression of electromechanical instability in fiber-reinforced dielectric elastomers

    Directory of Open Access Journals (Sweden)

    Rui Xiao

    2016-03-01

    Full Text Available The electromechanical instability of dielectric elastomers has been a major challenge for the application of this class of active materials. In this work, we demonstrate that dielectric elastomers filled with soft fiber can suppress the electromechanical instability and achieve large deformation. Specifically, we developed a constitutive model to describe the dielectric and mechanical behaviors of fiber-reinforced elastomers. The model was applied to study the influence of stiffness, nonlinearity properties and the distribution of fiber on the instability of dielectric membrane under an electric field. The results show that there exists an optimal fiber distribution condition to achieve the maximum deformation before failure.

  11. Compressive strength measurements of hybrid dental composites treated with dry heat and light emitting diodes (LED post cure treatment

    Directory of Open Access Journals (Sweden)

    Jenny Krisnawaty

    2014-11-01

    Full Text Available Hybrid composites are mostly used on large cavities as restorative dental materials, whether it is used directly or indirectly. The mechanical properties of composite resin shall increase if it is treated with post cure treatment. The aim of this study is to evaluate compressive strength differences between dry heat and Light Emitting Diodes (LED treatment on the hybrid dental composite. A quasi-experimental was applied on this research with a total of 30 samples that were divided into two groups. Each sample was tested using LLOYD Universal Testing Machine with 1 mm/min speed to evaluate the compressive strength. The compressive strength results were marked when the sample was broken. The results of two groups were then analyzed using t-test statistical calculation. The results of this study show that post cure treatment on hybrid composite using LED light box (194.138 MPa was lower than dry heat treatment (227.339 MPa, which was also significantly different from statistical analysis. It can be concluded that compressive strength of LED light box was lower than dry heat post-cure treatment on the hybrid composite resin.

  12. Hydrogen-assisted post-growth substitution of tellurium into molybdenum disulfide monolayers with tunable compositions

    Science.gov (United States)

    Yin, Guoli; Zhu, Dancheng; Lv, Danhui; Hashemi, Arsalan; Fei, Zhen; Lin, Fang; Krasheninnikov, Arkady V.; Zhang, Ze; Komsa, Hannu-Pekka; Jin, Chuanhong

    2018-04-01

    Herein we report the successful doping of tellurium (Te) into molybdenum disulfide (MoS2) monolayers to form MoS2x Te2(1-x) alloy with variable compositions via a hydrogen-assisted post-growth chemical vapor deposition process. It is confirmed that H2 plays an indispensable role in the Te substitution into as-grown MoS2 monolayers. Atomic-resolution transmission electron microscopy allows us to determine the lattice sites and the concentration of introduced Te atoms. At a relatively low concentration, tellurium is only substituted in the sulfur sublattice to form monolayer MoS2(1-x)Te2x alloy, while with increasing Te concentration (up to ˜27.6% achieved in this study), local regions with enriched tellurium, large structural distortions, and obvious sulfur deficiency are observed. Statistical analysis of the Te distribution indicates the random substitution. Density functional theory calculations are used to investigate the stability of the alloy structures and their electronic properties. Comparison with experimental results indicate that the samples are unstrained and the Te atoms are predominantly substituted in the top S sublattice. Importantly, such ultimately thin Janus structure of MoS2(1-x)Te2x exhibits properties that are distinct from their constituents. We believe our results will inspire further exploration of the versatile properties of asymmetric 2D TMD alloys.

  13. Online Structural-Health Monitoring of Glass Fiber-Reinforced Thermoplastics Using Different Carbon Allotropes in the Interphase

    Directory of Open Access Journals (Sweden)

    Michael Thomas Müller

    2018-06-01

    Full Text Available An electromechanical response behavior is realized by nanostructuring the glass fiber interphase with different highly electrically conductive carbon allotropes like carbon nanotubes (CNT, graphene nanoplatelets (GNP, or conductive carbon black (CB. The operational capability of these multifunctional glass fibers for an online structural-health monitoring is demonstrated in endless glass fiber-reinforced polypropylene. The electromechanical response behavior, during a static or dynamic three-point bending test of various carbon modifications, shows qualitative differences in the signal quality and sensitivity due to the different aspect ratios of the nanoparticles and the associated electrically conductive network densities in the interphase. Depending on the embedding position within the glass fiber-reinforced composite compression, shear and tension loadings of the fibers can be distinguished by different characteristics of the corresponding electrical signal. The occurrence of irreversible signal changes during the dynamic loading can be attributed to filler reorientation processes caused by polymer creeping or by destruction of electrically conductive paths by cracks in the glass fiber interphase.

  14. A comparative study of bulk-fill composites: degree of conversion, post-gel shrinkage and cytotoxicity

    Directory of Open Access Journals (Sweden)

    Flávia Gonçalves

    2018-03-01

    Full Text Available Abstract: Bulk-fill composites are claimed to be restorative materials used in deep preparations and effectively photoactivated in layers up to 4 mm. The aim of the present study was to evaluate the degree of conversion, post-gel volumetric shrinkage, and cytotoxicity of six bulk-fill and two conventional composites. Degree of conversion was determined by FTIR spectroscopy; post-gel volumetric shrinkage was determined using the strain gauge method; and cytotoxicity in human fibroblasts was evaluated indirectly by the MTT assay. Data were subjected to one-way ANOVA/Tukey's test (α = 0.05. All materials, including bulk-fill and conventional composites, were classified as non-toxic, with cell viability higher than 70%. Bulk-fill composites exhibited volumetric shrinkage similar to or lower (1.4 to 0.4% than that of conventional composites (1.7–2.1%. However, only four of the bulk-fill composites were able to sustain a homogeneous conversion at the 4-mm depth. Despite their non-toxicity and shrinkage similar to that of conventional materials, not all commercial bulk-fill materials were able to maintain a conversion as high as 80% of the superficial layer, at the 4-mm depth, indicating some failure in the bulk-fill design of some commercial brands. Therefore, the use of bulk-fill materials in dental practice is advantageous, but special attention should be given to the selection and correct use of the materials.

  15. Effect of combined extrusion parameters on mechanical properties of basalt fiber-reinforced plastics based on polypropylene

    Science.gov (United States)

    Bashtannik, P. I.; Ovcharenko, V. G.; Boot, Yu. A.

    1997-11-01

    Basalt fibers are efficient reinforcing fillers for polypropylene because they increase both the mechanical and the tribotechnical properties of composites. Basalt fibers can compete with traditional fillers (glass and asbestos fibers) of polypropylene with respect to technological, economic, and toxic properties. The effect of technological parameters of producing polypropylene-based basalt fiber-reinforced plastics (BFRPs) by combined extrusion on their mechanical properties has been investigated. The extrusion temperature was found to be the main parameter determining the mechanical properties of the BFRPs. With temperature growth from 180 to 240°C, the residual length of the basalt fibers in the composite, as well as the adhesive strength of the polymer-fiber system, increased, while the composite defectiveness decreased. The tensile strength and elastic modulus increased from 35 to 42 MPa and 3.2 to 4.2 GPa, respectively. At the same time, the growth in composite solidity led to its higher brittleness. Thus, a higher temperature of extrusion allows us to produce materials which can be subjected to tensile and bending loads, while the materials produced at a lower temperature of extrusion are impact stable. The effect of the gap size between the extruder body and moving disks on the mechanical properties of the BFRPs is less significant than that of temperature. An increase of the gap size from 2 to 8 mm improves the impregnation quality of the fibers, but the extruder productivity diminishes. The possibility of controling the properties of reinforced polypropylene by varying the technological parameters of combined extrusion is shown. The polypropylene-based BFRPs produced by the proposed method surpass the properties of glass and asbestos fiber-reinforced plastics.

  16. Electromechanical behavior of fiber-reinforced dielectric elastomer membrane

    Directory of Open Access Journals (Sweden)

    Chi Li

    2015-04-01

    Full Text Available Based on its large deformation, light weight, and high energy density, dielectric elastomer (DE has been used as driven muscle in many areas. We design the fiber-reinforced DE membrane by adding fibers in the membrane. The deformation and driven force direction of the membrane can be tuned by changing the fiber arrangements. The actuation in the perpendicular direction of the DE membrane with long fibers first increases and then decreases by the increasing of the fiber spacing in the perpendicular direction. The horizontal actuation of the membrane decreases by decreasing the spacing of short fibers. In the membrane-inflating structure, the radially arranged fibers will break the axisymmetric behavior of the structure. The top area of the inflated balloon without fiber will buckle up when the voltage reaches a certain level. Finite element simulations based on nonlinear field theory are conducted to investigate the effects of fiber arrangement and verify the experimental results. This work can guide the design of fiber-reinforced DE.

  17. A thermo-viscoelastic approach for the characterization and modeling of the bending behavior of thermoplastic composites – Part II

    NARCIS (Netherlands)

    Ropers, Steffen; Sachs, Ulrich; Kardos, Marton; Osswald, Tim A.

    2017-01-01

    A proper description of the bending behavior is crucial to obtain accurate forming simulations, especially for continuous fiber-reinforced thermoplastic composites. These materials exhibit a highly temperature and bending-curvature dependent bending stiffness. These dependencies make the property

  18. Double-Sided Terahertz Imaging of Multilayered Glass Fiber-Reinforced Polymer

    Directory of Open Access Journals (Sweden)

    Przemyslaw Lopato

    2017-06-01

    Full Text Available Polymer matrix composites (PMC play important roles in modern industry. Increasing the number of such structures in aerospace, construction, and automotive applications enforces continuous monitoring of their condition. Nondestructive inspection of layered composite materials is much more complicated process than evaluation of homogenous, (mostly metallic structures. Several nondestructive methods are utilized in this case (ultrasonics, shearography, tap testing, acoustic emission, digital radiography, infrared imaging but none of them gives full description of evaluated structures. Thus, further development of NDT techniques should be studied. A pulsed terahertz method seems to be a good candidate for layered PMC inspection. It is based on picosecond electromagnetic pulses interacting with the evaluated structure. Differences of dielectric parameters enables detection of a particular layer in a layered material. In the case of multilayered structures, only layers close to surface can be detected. The response of deeper ones is averaged because of multiple reflections. In this paper a novel inspection procedure with a data processing algorithm is introduced. It is based on a double-sided measurement, acquired signal deconvolution, and data combining. In order to verify the application of the algorithm stress-subjected glass fiber-reinforced polymer (GFRP was evaluated. The obtained results enabled detection and detailed analysis of delaminations introduced by stress treatment and proved the applicability of the proposed algorithm.

  19. Morphology of root canal surface: A reflection on the process of cementation of the composite relined glass fiber post

    Directory of Open Access Journals (Sweden)

    Yasmine Mendes Pupo

    2017-01-01

    Full Text Available Background: The present study was conducted to evaluate the bond strength in the different root thirds (premolars and maxillary central incisors of composite relined glass fiber posts compared to untreated glass fiber posts cemented with dual- or chemical-cure cements. Materials and Methods: Sixty human single-rooted premolars (flat canal (n = 15 and 12 maxillary central incisors were used (round canal (n = 3. The teeth were sectioned, and the roots received endodontic treatment. The standardized preparation of the canals was carried out, and the roots were randomly divided into four groups according to the cementation systems: G1: cemented posts (dual: Ambar/Allcem; G2: relined posts (dual: Ambar/Allcem; G3: cemented posts (chemical: Fusion Duralink/Cement Post; and G4: relined posts (chemical: Fusion Duralink/Cement Post. The roots were cut to give two slices of each third of the root canal per specimen. Push-out test was conducted at a speed of 0.5 mm/min. Data were analyzed by analysis of variance and Tukey's post hoc test (α = 0.05. Results: There was no statistically significant difference between groups for the premolars (flat canal (P = 0.959. There was a significant difference in the central incisors between the middle and apical thirds in the cemented group when using the dual system (P = 0.04 and between the middle and apical thirds (P = 0.003 and cervical and apical thirds (P = 0.033 when using the chemical system. Conclusion: Due to the anatomy of the root canal, flat canal of the premolars does not require relining, but round canal of the maxillary central incisors demands it for more secure in the bond strength.

  20. Use of Steel Fiber-Reinforced Rubberized Concrete in Cold Regions

    Science.gov (United States)

    2017-12-24

    This report documents and presents the use of steel fiber-reinforced rubberized concrete (SFRRC) in cold regions. Further investigation of SFRRC use was conducted with the wheel tracker rut and freeze-thaw laboratory testing procedures at the Univers...

  1. Polyurethane foam infill for fiber-reinforced polymer (FRP) bridge deck panels.

    Science.gov (United States)

    2014-05-01

    Although still in their infancy, fiber-reinforced polymer (FRP) bridges have shown great promise in eliminating corrosion : concerns and meeting (or exceeding) FHWAs goal of 100-year life spans for bridges. While FRP bridges are cost-effective in ...

  2. Operational factors influence on service life characteristics of structural carbon fiber-reinforced plastic

    OpenAIRE

    Борозенець, Григорій; Павлов, Віктор; Семак, Інна

    2013-01-01

    The nature of strength changing of aircraft structural carbon fiber-reinforced plastic under influence of water saturation after static preloading and mode changing of structural elements forming process pressure is considered.

  3. Stochastic analysis of laminated composite plates on elastic foundation: The cases of post-buckling behavior and nonlinear free vibration

    International Nuclear Information System (INIS)

    Singh, B.N.; Lal, Achchhe

    2010-01-01

    This study deals with the stochastic post-buckling and nonlinear free vibration analysis of a laminated composite plate resting on a two parameters Pasternak foundation with Winkler cubic nonlinearity having uncertain system properties. The system properties are modeled as basic random variables. A C 0 nonlinear finite element formulation of the random problem based on higher-order shear deformation theory in the von Karman sense is presented. A direct iterative method in conjunction with a stochastic nonlinear finite element method proposed earlier by the authors is extended to analyze the effect of uncertainty in system properties on the post-buckling and nonlinear free vibration of the composite plates having Winler type of geometric nonlinearity. Mean as well as standard deviation of the responses have been obtained for various combinations of geometric parameters, foundation parameters, stacking sequences and boundary conditions and compared with those available in the literature and Monte Carlo simulation.

  4. Fracture resistance of endodontically treated teeth restored with Zirconia filler containing composite core material and fiber posts.

    Science.gov (United States)

    Jeaidi, Zaid Al

    2016-01-01

    To assess the fracture resistance of endodontically treated teeth with a novel Zirconia (Zr) nano-particle filler containing bulk fill resin composite. Forty-five freshly extracted maxillary central incisors were endodontically treated using conventional step back preparation and warm lateral condensation filling. Post space preparation was performed using drills compatible for fiber posts (Rely X Fiber Post) on all teeth (n=45), and posts were cemented using self etch resin cement (Rely X Unicem). Samples were equally divided into three groups (n=15) based on the type of core materials, ZirconCore (ZC) MulticCore Flow (MC) and Luxacore Dual (LC). All specimens were mounted in acrylic resin and loads were applied (Universal testing machine) at 130° to the long axis of teeth, at a crosshead speed of 0.5 mm/min until failure. The loads and the site at which the failures occurred were recorded. Data obtained was tabulated and analyzed using a statistical program. The means and standard deviations were compared using ANOVA and Multiple comparisons test. The lowest and highest failure loads were shown by groups LC (18.741±3.02) and MC (25.16±3.30) respectively. Group LC (18.741±3.02) showed significantly lower failure loads compared to groups ZC (23.02±4.21) and MC (25.16±3.30) (pcomposite cores was comparable to teeth restored with conventional Zr free bulk fill composites. Zr filled bulk fill composites are recommended for restoration of endodontically treated teeth as they show comparable fracture resistance to conventional composite materials with less catastrophic failures.

  5. Effect of different composite core materials on fracture resistance of endodontically treated teeth restored with FRC posts

    Directory of Open Access Journals (Sweden)

    Prapaporn PANITIWAT

    Full Text Available Abstract Objective This study evaluated the fracture resistance of endodontically treated teeth restored with fiber reinforced composite posts, using three resin composite core build-up materials, (Clearfil Photo Core (CPC, MultiCore Flow (MCF, and LuxaCore Z-Dual (LCZ, and a nanohybrid composite, (Tetric N-Ceram (TNC. Material and Methods Forty endodontically treated lower first premolars were restored with quartz fiber posts (D.T. Light-Post cemented with resin cement (Panavia F2.0. Samples were randomly divided into four groups (n=10. Each group was built-up with one of the four core materials following its manufacturers’ instructions. The teeth were embedded in acrylic resin blocks. Nickel-Chromium crowns were fixed on the specimens with resin cement. The fracture resistance was determined using a universal testing machine with a crosshead speed of 1 mm/min at 1350 to the tooth axis until failure occurred. All core materials used in the study were subjected to test for the flexural modulus according to ISO 4049:2009. Results One-way ANOVA and Bonferroni multiple comparisons test indicated that the fracture resistance was higher in the groups with CPC and MCF, which presented no statistically significant difference (p>0.05, but was significantly higher than in those with LCZ and TNC (p<0.05. In terms of the flexural modulus, the ranking from the highest values of the materials was aligned with the same tendency of fracture loads. Conclusion Among the cores used in this study, the composite core with high filler content tended to enhance fracture thresholds of teeth restored with fiber posts more than others.

  6. State-of-the-art of fiber-reinforced polymers in additive manufacturing technologies

    DEFF Research Database (Denmark)

    Hofstätter, Thomas; Pedersen, David Bue; Tosello, Guido

    2017-01-01

    Additive manufacturing technologies have received a lot of attention in recent years for their use in multiple materials such as metals, ceramics, and polymers. The aim of this review article is to analyze the technology of fiber-reinforced polymers and its implementation with additive...... manufacturing. This article reviews recent developments, ideas, and state-of-the-art technologies in this field. Moreover, it gives an overview of the materials currently available for fiber-reinforced material technology....

  7. Mesoscale Characterization of Fracture Properties of Steel Fiber-Reinforced Concrete Using a Lattice–Particle Model

    Directory of Open Access Journals (Sweden)

    Francisco Montero-Chacón

    2017-02-01

    Full Text Available This work presents a lattice–particle model for the analysis of steel fiber-reinforced concrete (SFRC. In this approach, fibers are explicitly modeled and connected to the concrete matrix lattice via interface elements. The interface behavior was calibrated by means of pullout tests and a range for the bond properties is proposed. The model was validated with analytical and experimental results under uniaxial tension and compression, demonstrating the ability of the model to correctly describe the effect of fiber volume fraction and distribution on fracture properties of SFRC. The lattice–particle model was integrated into a hierarchical homogenization-based scheme in which macroscopic material parameters are obtained from mesoscale simulations. Moreover, a representative volume element (RVE analysis was carried out and the results shows that such an RVE does exist in the post-peak regime and until localization takes place. Finally, the multiscale upscaling strategy was successfully validated with three-point bending tests.

  8. Mesoscale Characterization of Fracture Properties of Steel Fiber-Reinforced Concrete Using a Lattice-Particle Model.

    Science.gov (United States)

    Montero-Chacón, Francisco; Cifuentes, Héctor; Medina, Fernando

    2017-02-21

    This work presents a lattice-particle model for the analysis of steel fiber-reinforced concrete (SFRC). In this approach, fibers are explicitly modeled and connected to the concrete matrix lattice via interface elements. The interface behavior was calibrated by means of pullout tests and a range for the bond properties is proposed. The model was validated with analytical and experimental results under uniaxial tension and compression, demonstrating the ability of the model to correctly describe the effect of fiber volume fraction and distribution on fracture properties of SFRC. The lattice-particle model was integrated into a hierarchical homogenization-based scheme in which macroscopic material parameters are obtained from mesoscale simulations. Moreover, a representative volume element (RVE) analysis was carried out and the results shows that such an RVE does exist in the post-peak regime and until localization takes place. Finally, the multiscale upscaling strategy was successfully validated with three-point bending tests.

  9. Feasibility of Reducing the Fiber Content in Ultra-High-Performance Fiber-Reinforced Concrete under Flexure.

    Science.gov (United States)

    Park, Jung-Jun; Yoo, Doo-Yeol; Park, Gi-Joon; Kim, Sung-Wook

    2017-01-28

    In this study, the flexural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) is examined as a function of fiber length and volume fraction. Straight steel fiber with three different lengths ( l f ) of 13, 19.5, and 30 mm and four different volume fractions ( v f ) of 0.5%, 1.0%, 1.5%, and 2.0% are considered. Test results show that post-cracking flexural properties of UHPFRC, such as flexural strength, deflection capacity, toughness, and cracking behavior, improve with increasing fiber length and volume fraction, while first-cracking properties are not significantly influenced by fiber length and volume fraction. A 0.5 vol % reduction of steel fiber content relative to commercial UHPFRC can be achieved without deterioration of flexural performance by replacing short fibers ( l f of 13 mm) with longer fibers ( l f of 19.5 mm and 30 mm).

  10. Mesoscale Characterization of Fracture Properties of Steel Fiber-Reinforced Concrete Using a Lattice–Particle Model

    Science.gov (United States)

    Montero-Chacón, Francisco; Cifuentes, Héctor; Medina, Fernando

    2017-01-01

    This work presents a lattice–particle model for the analysis of steel fiber-reinforced concrete (SFRC). In this approach, fibers are explicitly modeled and connected to the concrete matrix lattice via interface elements. The interface behavior was calibrated by means of pullout tests and a range for the bond properties is proposed. The model was validated with analytical and experimental results under uniaxial tension and compression, demonstrating the ability of the model to correctly describe the effect of fiber volume fraction and distribution on fracture properties of SFRC. The lattice–particle model was integrated into a hierarchical homogenization-based scheme in which macroscopic material parameters are obtained from mesoscale simulations. Moreover, a representative volume element (RVE) analysis was carried out and the results shows that such an RVE does exist in the post-peak regime and until localization takes place. Finally, the multiscale upscaling strategy was successfully validated with three-point bending tests. PMID:28772568

  11. Dual Function Behavior of Carbon Fiber-Reinforced Polymer in Simulated Pore Solution

    Directory of Open Access Journals (Sweden)

    Ji-Hua Zhu

    2016-02-01

    Full Text Available The mechanical and electrochemical performance of carbon fiber-reinforced polymer (CFRP were investigated regarding a novel improvement in the load-carrying capacity and durability of reinforced concrete structures by adopting CFRP as both a structural strengthener and an anode of the impressed current cathodic protection (ICCP system. The mechanical and anode performance of CFRP were investigated in an aqueous pore solution in which the electrolytes were available to the anode in a cured concrete structure. Accelerated polarization tests were designed with different test durations and various levels of applied currents in accordance with the international standard. The CFRP specimens were mechanically characterized after polarization. The measured feeding voltage and potential during the test period indicates CFRP have stable anode performance in a simulated pore solution. Two failure modes were observed through tensile testing. The tensile properties of the post-polarization CFRP specimens declined with an increased charge density. The CFRP demonstrated success as a structural strengthener and ICCP anode. We propose a mathematic model predicting the tensile strengths of CFRP with varied impressed charge densities.

  12. High rate response of ultra-high-performance fiber-reinforced concretes under direct tension

    Energy Technology Data Exchange (ETDEWEB)

    Tran, Ngoc Thanh [Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747 (Korea, Republic of); Tran, Tuan Kiet [Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747 (Korea, Republic of); Department of Civil Engineering and Applied Mechanics, Ho Chi Minh City University of Technology and Education, 01 Vo Van Ngan, Thu Duc District, Ho Chi Minh City (Viet Nam); Kim, Dong Joo, E-mail: djkim75@sejong.ac.kr [Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747 (Korea, Republic of)

    2015-03-15

    The tensile response of ultra-high-performance fiber-reinforced concretes (UHPFRCs) at high strain rates (5–24 s{sup −} {sup 1}) was investigated. Three types of steel fibers, including twisted, long and short smooth steel fibers, were added by 1.5% volume content in an ultra high performance concrete (UHPC) with a compressive strength of 180 MPa. Two different cross sections, 25 × 25 and 25 × 50 mm{sup 2}, of tensile specimens were used to investigate the effect of the cross section area on the measured tensile response of UHPFRCs. Although all the three fibers generated strain hardening behavior even at high strain rates, long smooth fibers produced the highest tensile resistance at high rates whereas twisted fiber did at static rate. The breakages of twisted fibers were observed from the specimens tested at high strain rates unlike smooth steel fibers. The tensile behavior of UHPFRCs at high strain rates was clearly influenced by the specimen size, especially in post-cracking strength.

  13. SEM and TEM characterization of the microstructure of post-compressed TiB2/2024Al composite.

    Science.gov (United States)

    Guo, Q; Jiang, L T; Chen, G Q; Feng, D; Sun, D L; Wu, G H

    2012-02-01

    In the present work, 55 vol.% TiB(2)/2024Al composites were obtained by pressure infiltration method. Compressive properties of 55 vol.% TiB(2)/2024Al composite under the strain rates of 10(-3) and 1S(-1) at different temperature were measured and microstructure of post-compressed TiB(2)/2024Al composite was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). No trace of Al(3)Ti compound flake was found. TiB(2)-Al interface was smooth without significant reaction products, and orientation relationships ( [Formula: see text] and [Formula: see text] ) were revealed by HRTEM. Compressive strength of TiB(2)/2024Al composites decreased with temperature regardless of strain rates. The strain-rate-sensitivity of TiB(2)/2024Al composites increased with the increasing temperature. Fracture surface of specimens compressed at 25 and 250°C under 10(-3)S(-1) were characterized by furrow. Under 10(-3)S(-1), high density dislocations were formed in Al matrix when compressed at 25°C and dynamic recrystallization occurred at 250°C. Segregation of Mg and Cu on the subgrain boundary was also revealed at 550°C. Dislocations, whose density increased with temperature, were formed in TiB(2) particles under 1S(-1). Deformation of composites is affected by matrix, reinforcement and strain rate. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Post-irradiation hardness of resin-modified glass ionomer cements and a polyacid-modified composite resin

    International Nuclear Information System (INIS)

    Yap, A.U.J.

    1997-01-01

    This study examined the post-irradiation hardness of resin-modified glass ionomer cements and a polyacid-modified composite resin using a digital microhardness tester. Change in hardness of these materials over a period of 6 months was compared to that of conventional glass ionomer cements and a composite resin. With the exception of the composite resin, all materials showed a significant increase in hardness over 24 h after their initial set. Dual-cure resin-modified glass ionomer cements showed decreased hardness with increased storage time in saline at 37 o C. Results suggest that the addition of resins to glass ionomer cements does not improve initial hardness and does not negate the acid-base reaction of conventional cements. Resin addition may, however, lead to increased water sorption and decreased hardness. (author)

  15. Post-Impact and Open Hole Tensile Of Kenaf Hybrid Composites

    Science.gov (United States)

    Yunus, S.; Salleh, Z.; Masdek, N. R. N. M.; Taib, Y. M.; Azhar, I. I. S.; Hyie, K. M.

    2018-03-01

    Nowadays, kenaf hybrid glass composites has been used for a vast field of study throughout the globe. There are several compositions and orientation of kenaf hybrid glass composites that has been studied. With regards to the study that has been done, this study will be focussing on a 90FG/0/90/90/0/90FG orientation of kenaf hybrid glass composites. Polyester resin is used as a matrix to these hybrid composites. Impacted and open hole specimens were then analyzed through tensile test. All specimens were fabricated by using the cold press hand lay-up technique. The results revealed that the hybrid composites were hardly affected by the impact up to 6J. After 6J the impacted specimens experienced a significant damage for both strength and modulus. The same goes to open hole specimens where the same trend of tensile properties were observed as impacted specimens.

  16. Mechanical and Morphology Properties of Feather Fiber Composite for Dental Post Application

    International Nuclear Information System (INIS)

    Siti Maizatul Farhain Salehuddin; Mohammed Rafiq Abdul Kadir; Eshamsul Sulaiman; Noor Hayaty Abu Kasim

    2014-01-01

    Feather/plastic composite material was fabricated from polymethyl methacrylate (PMMA), feather fiber (FF) and montmorillonite (MMT) using brabender internal mixer. PMMA based composites were produced with 1, 3, 5, 7 and 10 phr composite of mass feather fiber with and without 4 % of montmorillonite (MMT). Alkali treatment was used to improve the interfacial adhesion among the feather fiber (FF) and the PMMA. Flexural properties of FF/ PMMA and FF/ PMMA/ MMT composites were investigated. Composites were analyzed by Scanning Electron (SEM) and Fourier Transform Infra Red (FTIR) spectroscopy techniques. The result showed that, the addition of FF significantly increased the flexural strength of the composites. The hydrophobic nature of feather fiber displayed an excellent compatibility among fibers and PMMA matrix. (author)

  17. Mechanical Properties of Abutments: Resin-Bonded Glass Fiber-Reinforced Versus Titanium.

    Science.gov (United States)

    Bassi, Mirko Andreasi; Bedini, Rosells; Pecci, Raffaela; Ioppolo, Pietro; Laritano, Dorina; Carinci, Francesco

    2016-01-01

    The clinical success and longevity of endosseous implants, after their prosthetic finalization, mainly depends on mechanical factors. Excessive mechanical stress has been shown to cause initial bone loss around implants in the presence of a rigid implant-prosthetic connection. The implant abutments are manufactured with high elastic modulus materials such as titanium, steel, precious alloys, or esthetic ceramics. These materials do not absorb any type of shock from the chewing loads or ensure protection of the bone-implant interface, especially when the esthetic restorative material is ceramic rather than composite resin. The mechanical resistance to cyclical load was evaluated in a tooth-colored fiber-reinforced abutment prototype (TCFRA) and compared to that of a similarly shaped titanium abutment (TA). Eight TCFRAs and eight TAs were adhesively cemented on as many titanium implants. The swinging the two types of abutments showed during the application of sinusoidal load was also analyzed. In the TA group, fracture and deformation occurred in 12.5% of samples, while debonding occurred in 62.5%. In the TCFRA group, only debonding was present, in 37.5% of samples. In comparison to the TAs, the TCFRAs exhibited greater swinging during the application of sinusoidal load. In the TA group extrusion prevailed, whereas in the TCFRA group intrusion was more frequent. TCFRA demonstrated a greater elasticity than did TAs to the flexural load, absorbing part of the transversal load applied on the fixture during the chewing function and thus reducing the stress on the bone-implant interface.

  18. Mechanical properties of resin glass fiber-reinforced abutment in comparison to titanium abutment

    Science.gov (United States)

    Andreasi Bassi, Mirko; Bedini, Rossella; Pecci, Raffella; Ioppolo, Pietro; Lauritano, Dorina; Carinci, Francesco

    2015-01-01

    Purpose: So far, definitive implant abutments have been performed with high elastic modulus materials, which prevented any type of shock absorption of the chewing loads and as a consequence, the protection of the bone-fixture interface. This is particularly the case when the esthetic restorative material chosen is ceramic rather than composite resin. The adoption of an anisotropic abutment, characterized by an elastic deformability, could allow decreasing the impulse of chewing forces transmitted to the crestal bone. Materials and Methods: According to research protocol, the mechanical resistance to cyclical load was evaluated in a tooth-colored fiber-reinforced abutment (TCFRA) prototype and compared to that of a titanium abutment (TA), thus eight TCFRAs and eight TAs were adhesively cemented on as many titanium implants. The swinging that the two types of abutments showed during the application of sinusoidal load was also analyzed. Results: In the TA group, both fracture and deformation occurred in 12.5% of samples while debonding 62.5%. In the TCFRA group, only debonding was present in 37.5% of samples. In comparison to the TAs, the TCFRAs exhibited a greater swinging during the application of sinusoidal load. In the TA group, the extrusion prevailed, whereas in the TCFRA group, the intrusion was more frequent. Conclusion: The greater elasticity of TCFRA to the flexural load allows absorbing part of the transversal load applied on the fixture during the chewing function, thus reducing the stress on the bone-implant interface. PMID:26229266

  19. Fiber-Reinforced Polymer Nets for Strengthening Lava Stone Masonries in Historical Buildings

    Directory of Open Access Journals (Sweden)

    Santi Maria Cascone

    2016-04-01

    Full Text Available The strengthening of masonries is a crucial step in building restoration works because of its relevance, mostly with regard to the improvement of building seismic behavior. Current building technologies are based on the use of steel nets which are incorporated into cement plasters. The use of steel has a number of contraindications that can be solved by using composite materials such as glass fiber nets, which have high mechanical characteristics and lightness, elasticity, corrosion resistance, and compatibility with lime plaster. Building interventions, that take into account the application of glass fiber nets, are very sustainable from several points of view, e.g., material production, in situ works, economic cost and durability. In Italy, several experiments have been carried out in situ with the aim of testing the mechanical characteristics of masonries which have been treated with fiber-reinforced polymer (FRP nets. This paper deals with a series of in situ tests carried out during the restoration works of an important historical building located in Catania (Sicily, Italy. The results achieved are largely positive.

  20. Study of matrix micro-cracking in nano clay and acrylic tri-block-copolymer modified epoxy/basalt fiber-reinforced pressure-retaining structures

    Directory of Open Access Journals (Sweden)

    2011-10-01

    Full Text Available In fiber-reinforced polymer pressure-retaining structures, such as pipes and vessels, micro-level failure commonly causes fluid permeation due to matrix cracking. This study explores the effect of nano-reinforcements on matrix cracking in filament-wound basalt fiber/epoxy composite structures. The microstructure and mechanical properties of bulk epoxy nanocomposites and hybrid fiber-reinforced composite pipes modified with acrylic tri-block-copolymer and organophilic layered silicate clay were investigated. In cured epoxy, the tri-block-copolymer phase separated into disordered spherical micelle inclusions; an exfoliated and intercalated structure was observed for the nano-clay. Block-copolymer addition significantly enhanced epoxy fracture toughness by a mechanism of particle cavitation and matrix shear yielding, whereas toughness remained unchanged in nano-clay filled nanocomposites due to the occurrence of lower energy resistance phenomena such as crack deflection and branching.Tensile stiffness increased with nano-clay content, while it decreased slightly for block-copolymer modified epoxy. Composite pipes modified with either the organic and inorganic nanoparticles exhibited moderate improvements in leakage failure strain (i.e. matrix cracking strain; however, reductions in functional and structural failure strength were observed.

  1. Flexible n-type thermoelectric composite films with enhanced performance through interface engineering and post-treatment

    Science.gov (United States)

    An, Hyeunhwan; Karas, Dale; Kim, Byung-Wook; Trabia, Sarah; Moon, Jaeyun

    2018-07-01

    Flexible thermoelectric (TE) materials, which are devices that convert thermal gradients to electrical energy, have attracted interest for practical energy-harvesting/recovery applications. However, as compared with p-type materials, the progress on the development of n-type TE flexible materials has been slow due to difficulties involved in n-type doping techniques. This study used high mobility carbon nanotubes (CNTs) to a uniformly mixed hybrid-composite, resulting in an enhanced power factor by increasing electrical conductivity. The energy filtering effect and stoichiometric composition of the material used, bismuth telluride (Bi2Te3) correlated to a significant enhancement in TE performance, with a power factor of 225.9 μW m‑1K‑2 at room temperature: a factor of 65 higher than as-fabricated composite film. This paper describes a simplified synthesis for the preparation of the composite film that eliminates time-intensive and cost-prohibitive processing, traditionally seen during extrusion and dicing inorganic manufacturing. The resulting post-annealed composite film consisting of Bi2Te3 nanowire and CNTs demonstrate a promising candidate for material that can be used for an n-type TE device that has improved energy conversion efficiency.

  2. Valorization of post-consumer waste plastic in cementitious concrete composites

    International Nuclear Information System (INIS)

    Marzouk, O. Yazoghli; Dheilly, R.M.; Queneudec, M.

    2007-01-01

    The sheer amount of disposable bottles being produced nowadays makes it imperative to identify alternative procedures for recycling them since they are non-biodegradable. This paper describes an innovative use of consumed plastic bottle waste as sand-substitution aggregate within composite materials for building application. Particularly, bottles made of polyethylene terephthalate (PET) have been used as partial and complete substitutes for sand in concrete composites. Various volume fractions of sand varying from 2% to 100% were substituted by the same volume of granulated plastic, and various sizes of PET aggregates were used. The bulk density and mechanical characteristics of the composites produced were evaluated. To study the relationship between mechanical properties and composite microstructure, scanning electron microscopy technique was employed. The results presented show that substituting sand at a level below 50% by volume with granulated PET, whose upper granular limit equals 5 mm, affects neither the compressive strength nor the flexural strength of composites. This study demonstrates that plastic bottles shredded into small PET particles may be used successfully as sand-substitution aggregates in cementitious concrete composites. These new composites would appear to offer an attractive low-cost material with consistent properties; moreover, they would help in resolving some of the solid waste problems created by plastics production and in saving energy

  3. Vancomycin–chitosan composite deposited on post porous hydroxyapatite coated Ti6Al4V implant for drug controlled release

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Chi-Chuan [Department of Materials Science and Engineering, National Chung Hsing, University 250, Kuo-Kuang Road, Taichung 40227, Taiwan (China); Lin, Chien-Chung [Department of Materials Science and Engineering, National Chung Hsing, University 250, Kuo-Kuang Road, Taichung 40227, Taiwan (China); Department of Orthopaedic Surgery, Taichung Armed Force General Hospital, 348, Sec. 2, Jhongshan Road, Taiping City, Taichung 411, Taiwan (China); Liao, Jiunn-Wang [Graduate Institute of Veterinary Pathobiology, National Chung Hsing, University 250, Kuo-Kuang Road, Taichung 40227, Taiwan (China); Yen, Shiow-Kang, E-mail: skyen@dragon.nchu.edu.tw [Department of Materials Science and Engineering, National Chung Hsing, University 250, Kuo-Kuang Road, Taichung 40227, Taiwan (China)

    2013-05-01

    Through the hydrogen bonds and the deprotonation, the vancomycin–chitosan composite has been originally deposited on Ti4Al4V by electrochemical technology. However, the rapid destruction of the hydrogen bonding between them by polar water molecules during immersion tests revealed 80% drug burst in a few hours. In this study, the post porous hydroxyapatite (HA) coated Ti4Al4V is prepared for the subsequent electrolytic deposition of vancomycin–chitosan composite to control the drug release. As expected, the initial burst is reduced to 55%, followed by a steady release about 20% from day 1 to day 5 and a slower release of the retained 25% after day 6, resulting in bacterial inhibition zone diameter of 30 mm which can last for more than a month in antibacterial tests, compared with the coated specimen without HA gradually loosing inhibition zone after 21 days. Besides, the cell culture indicates that the vancomycin–chitosan/HA composite coated has enhanced the proliferation, the differentiation and the mineralization of the osteoblast-like cell. In general, it is helpful for the osteointegration on permanent implants. Consistently, it effectively provides the prophylaxis and therapy of osteomyelitis according to the results of the rabbit infection animal model. - Highlights: ► The releasing curve of the vancomycin–chitosan/HA composite revealed three periods. ► The drug release sustained one month due to the effect of post porous HA coating. ► The composite coating could treat the osteomyelitis in the rabbit infection model.

  4. Raman spectroscopic assessment of degree of conversion of bulk-fill resin composites--changes at 24 hours post cure.

    Science.gov (United States)

    Par, M; Gamulin, O; Marovic, D; Klaric, E; Tarle, Z

    2015-01-01

    The aim of this study was to determine degree of conversion (DC) of solid and flowable bulk-fill composites immediately and after 24 hours and investigate the variations of DC at surface and depths up to 4 mm. Eight bulk-fill composites (Tetric EvoCeram Bulk Fill [shades IVA and IVB], Quixfil, X-tra fil, Venus Bulk Fill, X-tra Base, SDR, Filtek Bulk Fill) were investigated, and two conventional composites (GrandioSO, X-Flow) were used as controls. The samples (n = 5) were cured for 20 seconds with irradiance of 1090 mW/cm(2). Raman spectroscopic measurements were made immediately after curing on sample surfaces and after 24 hours of dark storage at surface and at incremental depths up to 4 mm. Mean DC values were compared using repeated measures analysis of variance (ANOVA) and t-test for dependent samples. Surface DC values immediately after curing ranged from 59.1%-71.8%, while the 24-hour postcure values ranged from 71.3%-86.1%. A significant increase of DC was observed 24 hours post cure for all bulk-fill composites, which amounted from 11.3% to 16.9%. Decrease of DC through depths up to 4 mm varied widely among bulk-fill composites and ranged from 2.9% to 19.7%. All bulk-fill composites presented a considerable 24-hour postcure DC increase and clinically acceptable DC at depths up to 4 mm. Conventional control composites were sufficiently cured only up to 2 mm, despite significant postcure polymerization.

  5. Chapter 15: Characterization and Processing of Nanocellulose Thermosetting Composites

    Science.gov (United States)

    Ronald C. Sabo; Rani F. Elhajjar; Craig M. Clemons; Krishna M. Pillai

    2015-01-01

    Fiber-reinforced polymer composites have gained popularity through their advantages over conventional metallic materials. Most polymer composites are traditionally made with reinforcing fibers such as carbon or glass. However, there has been recent interest in sourcing these reinforcing fibers from renewable, natural resources. Nanocellulose-based reinforcements...

  6. Fruit cuticle lipid composition and fruit post-harvest water loss in an advanced backcross generation of pepper (Capsicum sp.)

    KAUST Repository

    Parsons, Eugene P.; Popopvsky, Sigal; Lohrey, Gregory T.; Lu, Shiyou; Alkalai-Tuvia, Sharon; Perzelan, Yaacov; Paran, Ilan; Fallik, Elazar; Jenks, Matthew A.

    2012-01-01

    To understand the role of fruit cuticle lipid composition in fruit water loss, an advanced backcross population, the BC2F2, was created between the Capsicum annuum (PI1154) and the Capsicum chinense (USDA162), which have high and low post-harvest water loss rates, respectively. Besides dramatic differences in fruit water loss, preliminary studies also revealed that these parents exhibited significant differences in both the amount and composition of their fruit cuticle. Cuticle analysis of the BC2F2 fruit revealed that although water loss rate was not strongly associated with the total surface wax amount, there were significant correlations between water loss rate and cuticle composition. We found a positive correlation between water loss rate and the amount of total triterpenoid plus sterol compounds, and negative correlations between water loss and the alkane to triterpenoid plus sterol ratio. We also report negative correlations between water loss rate and the proportion of both alkanes and aliphatics to total surface wax amount. For the first time, we report significant correlations between water loss and cutin monomer composition. We found positive associations of water loss rate with the total cutin, total C16 monomers and 16-dihydroxy hexadecanoic acid. Our results support the hypothesis that simple straight-chain aliphatic cuticle constituents form more impermeable cuticular barriers than more complex isoprenoid-based compounds. These results shed new light on the biochemical basis for cuticle involvement in fruit water loss. © 2012 Physiologia Plantarum.

  7. Fruit cuticle lipid composition and fruit post-harvest water loss in an advanced backcross generation of pepper (Capsicum sp.)

    KAUST Repository

    Parsons, Eugene P.

    2012-03-05

    To understand the role of fruit cuticle lipid composition in fruit water loss, an advanced backcross population, the BC2F2, was created between the Capsicum annuum (PI1154) and the Capsicum chinense (USDA162), which have high and low post-harvest water loss rates, respectively. Besides dramatic differences in fruit water loss, preliminary studies also revealed that these parents exhibited significant differences in both the amount and composition of their fruit cuticle. Cuticle analysis of the BC2F2 fruit revealed that although water loss rate was not strongly associated with the total surface wax amount, there were significant correlations between water loss rate and cuticle composition. We found a positive correlation between water loss rate and the amount of total triterpenoid plus sterol compounds, and negative correlations between water loss and the alkane to triterpenoid plus sterol ratio. We also report negative correlations between water loss rate and the proportion of both alkanes and aliphatics to total surface wax amount. For the first time, we report significant correlations between water loss and cutin monomer composition. We found positive associations of water loss rate with the total cutin, total C16 monomers and 16-dihydroxy hexadecanoic acid. Our results support the hypothesis that simple straight-chain aliphatic cuticle constituents form more impermeable cuticular barriers than more complex isoprenoid-based compounds. These results shed new light on the biochemical basis for cuticle involvement in fruit water loss. © 2012 Physiologia Plantarum.

  8. Floating Foundations: "Kairos," Community, and a Composition Program in Post-Katrina New Orleans

    Science.gov (United States)

    Johnson, T. R.; Letter, Joe; Livingston, Judith Kemerait

    2009-01-01

    The authors describe their individual and collective experiences reconstructing their New Orleans-based university composition program in the aftermath of Hurricane Katrina. They emphasize how the concept of "floating foundations" helps account for changes in their students' interests, and they suggest that this idea is applicable to the…

  9. Numerical modeling of hybrid fiber-reinforced concrete (hyfrc)

    International Nuclear Information System (INIS)

    Hameed, R.; Turatsinze, A.

    2015-01-01

    A model for numerical simulation of mechanical response of concrete reinforced with slipping and non slipping metallic fibers in hybrid form is presented in this paper. Constitutive law used to model plain concrete behaviour is based on plasticity and damage theories, and is capable to determine localized crack opening in three dimensional (3-D) systems. Behaviour law used for slipping metallic fibers is formulated based on effective stress carried by these fibers after when concrete matrix is cracked. A continuous approach is proposed to model the effect of addition of non-slipping metallic fibers in plain concrete. This approach considers the constitutive law of concrete matrix with increased fracture energy in tension obtained experimentally in direct tension tests on Fiber Reinforced Concrete (FRC). To simulate the mechanical behaviour of hybrid fiber-reinforced concrete (HyFRC), proposed approaches to model non-slipping metallic fibers and constitutive law of plain concrete and slipping fibers are used simultaneously without any additive equation. All the parameters used by the proposed model have physical meanings and are determined through experiments or drawn from literature. The model was implemented in Finite Element (FE) Code CASTEM and tested on FRC prismatic notched specimens in flexure. Model prediction showed good agreement with experimental results. (author)

  10. Probabilistic Flexural Fatigue in Plain and Fiber-Reinforced Concrete.

    Science.gov (United States)

    Ríos, José D; Cifuentes, Héctor; Yu, Rena C; Ruiz, Gonzalo

    2017-07-07

    The objective of this work is two-fold. First, we attempt to fit the experimental data on the flexural fatigue of plain and fiber-reinforced concrete with a probabilistic model (Saucedo, Yu, Medeiros, Zhang and Ruiz, Int. J. Fatigue, 2013, 48, 308-318). This model was validated for compressive fatigue at various loading frequencies, but not for flexural fatigue. Since the model is probabilistic, it is not necessarily related to the specific mechanism of fatigue damage, but rather generically explains the fatigue distribution in concrete (plain or reinforced with fibers) for damage under compression, tension or flexion. In this work, more than 100 series of flexural fatigue tests in the literature are fit with excellent results. Since the distribution of monotonic tests was not available in the majority of cases, a two-step procedure is established to estimate the model parameters based solely on fatigue tests. The coefficient of regression was more than 0.90 except for particular cases where not all tests were strictly performed under the same loading conditions, which confirms the applicability of the model to flexural fatigue data analysis. Moreover, the model parameters are closely related to fatigue performance, which demonstrates the predictive capacity of the model. For instance, the scale parameter is related to flexural strength, which improves with the addition of fibers. Similarly, fiber increases the scattering of fatigue life, which is reflected by the decreasing shape parameter.

  11. Assessment of the mechanical properties of sisal fiber-reinforced silty clay using triaxial shear tests.

    Science.gov (United States)

    Wu, Yankai; Li, Yanbin; Niu, Bin

    2014-01-01

    Fiber reinforcement is widely used in construction engineering to improve the mechanical properties of soil because it increases the soil's strength and improves the soil's mechanical properties. However, the mechanical properties of fiber-reinforced soils remain controversial. The present study investigated the mechanical properties of silty clay reinforced with discrete, randomly distributed sisal fibers using triaxial shear tests. The sisal fibers were cut to different lengths, randomly mixed with silty clay in varying percentages, and compacted to the maximum dry density at the optimum moisture content. The results indicate that with a fiber length of 10 mm and content of 1.0%, sisal fiber-reinforced silty clay is 20% stronger than nonreinforced silty clay. The fiber-reinforced silty clay exhibited crack fracture and surface shear fracture failure modes, implying that sisal fiber is a good earth reinforcement material with potential applications in civil engineering, dam foundation, roadbed engineering, and ground treatment.

  12. Adjusting cryodiluent composition for improved post-thaw quality of rabbit spermatozoa.

    Directory of Open Access Journals (Sweden)

    Sally E Hall

    Full Text Available Improved fertility following artificial insemination with frozen-thawed spermatozoa would offer rabbit producers faster genetic improvement. Previous work investigating cryoprotectants for rabbit spermatozoa have reported inconsistent results. Semen was collected from three rabbit bucks by artificial vagina and frozen using a standard procedure with varied cryodiluent components. Post-thaw analysis encompassed motility, sperm kinematic parameters and acrosome and membrane integrity. Spermatozoa were evaluated at 0, 2 and 4 h after thawing. Experiment 1 compared diluents with 3.5% dimethyl sulfoxide (DMSO, 1.5% acetamide, 1.75% DMSO + 0.75% acetamide or 3.5% DMSO + 1.5% acetamide. The treatment that resulted in the highest post-thaw motility (P<0.001 and acrosome integrity (P<0.001 was DMSO alone. Experiment 2 compared 3.5, 7 and 10% DMSO in the cryodiluent. The best post-thaw sperm motility (P<0.001 and linearity (P = .002 was in 3.5% DMSO, while 10% DMSO afforded higher acrosome/membrane integrity at this last time point (P<0.05. Experiment 3 varied the cryodiluent to contain either 9 or 17% egg yolk or 9 or 17% low density lipoproteins extracted from whole egg yolk. The treatment with the best post-thaw result was 17% egg yolk (motility, P = 0.01; acrosome/membrane integrity, P<0.001. Experiment 4 compared different carbohydrates in the cryodiluent; 50 mM glucose (TCG, 25 mM glucose with 25 mM sucrose (TCGS low, or 50 mM glucose with 50 mM sucrose (TCGS high. When data were pooled across time points, TCG had significantly higher motility than TCGS high (P = 0.021, but was not different from TCGS low. However, TCG had fewer spermatozoa with intact acrosomes and membranes than both TCGS low and TCGS high (P = .002. Put together, these results indicate that the best cryodiluent for rabbit spermatozoa frozen under the conditions used in this paper is with 7% DMSO and 17% egg yolk in a base medium containing 25 mM glucose and 25 mM sucrose.

  13. Mixture for producing fracture-resistant, fiber-reinforced ceramic material by microwave heating

    Science.gov (United States)

    Meek, T.T.; Blake, R.D.

    1985-04-03

    A fracture-resistant, fiber-reinforced ceramic substrate is produced by a method which involves preparing a ceramic precursor mixture comprising glass material, a coupling agent, and resilient fibers, and then exposing the mixture to microwave energy. The microwave field orients the fibers in the resulting ceramic material in a desired pattern wherein heat later generated in or on the substrate can be dissipated in a desired geometric pattern parallel to the fiber pattern. Additionally, the shunt capacitance of the fracture-resistant, fiber-reinforced ceramic substrate is lower which provides for a quicker transit time for electronic pulses in any conducting pathway etched into the ceramic substrate.

  14. Mechanical and physical properties of carbon-graphite fiber-reinforced polymers intended for implant suprastructures.

    Science.gov (United States)

    Segerström, Susanna; Ruyter, I Eystein

    2007-09-01

    Mechanical properties and quality of fiber/matrix adhesion of poly(methyl methacrylate) (PMMA)-based materials, reinforced with carbon-graphite (CG) fibers that are able to remain in a plastic state until polymerization, were examined. Tubes of cleaned braided CG fibers were treated with a sizing resin. Two resin mixtures, resin A and resin B, stable in the fluid state and containing different cross-linking agents, were reinforced with CG fiber loadings of 24, 36, and 47 wt% (20, 29, and 38 vol.%). In addition, resin B was reinforced with 58 wt% (47 vol.%). After heat-polymerization, flexural strength and modulus were evaluated, both dry and after water storage. Coefficient of thermal expansion, longitudinally and in the transverse direction of the specimens, was determined. Adhesion between fibers and matrix was evaluated with scanning electron microscopy (SEM). Flexural properties and linear coefficient of thermal expansion were similar for both fiber composites. With increased fiber loading, flexural properties increased. For 47 wt% fibers in polymer A the flexural strength was 547.7 (28.12) MPa and for polymer B 563.3 (89.24) MPa when water saturated. Linear coefficient of thermal expansion was for 47 wt% CG fiber-reinforced polymers; -2.5 x 10(-6) degrees C-1 longitudinally and 62.4 x 10(-6) degrees C-1 in the transverse direction of the specimens. SEM revealed good adhesion between fibers and matrix. More porosity was observed with fiber loading of 58 wt%. The fiber treatment and the developed resin matrices resulted in good adhesion between CG fibers and matrix. The properties observed indicate a potential for implant-retained prostheses.

  15. Feasibility of Steel Fiber-Reinforced Rubberized Concrete in Cold Regions for High Volume Intersections

    Science.gov (United States)

    Abou Eid, Mahear A.

    There are many challenges faced with the use of Portland Cement Concrete (PCC) in cold regions, but with the inclusion of new technologies such as steel fibers and recycled tire crumb rubber efficient construction may be possible. Research was conducted on a modified concrete material that included both steel fibers and crumb rubber. The composite material was called Steel Fiber-Reinforced Rubberized Concrete (SFRRC). The objective of this investigation was to provide evidence showing that SFRRC can reduce tire rutting compared to asphaltic pavement. In addition, the research showed that the SFRRC could withstand freeze-thaw cycles and increase service life of roadways. Several tests were performed to determine the characteristics of the material. Freeze-thaw testing was performed to determine compressive strength loss and visual deterioration of the material. Wheel tracker rut testing was performed both with the standard steel wheel and with a modified studded rubber tire to determine plastic deformation and rut resistance. An experimental test slab was cast in place on a public approach to observe the construction procedures, the effects of studded tire wear and the frost actions in cold region conditions. Based on freeze-thaw and wheel tracker test results and observations of the experimental test slab, the SFRRC material shows viability in cold regions for resisting freeze-thaw actions. The freeze-thaw testing resulted in increased compressive strength after 300 freeze-thaw cycles and very low deterioration of material compared to standard PCC. The wheel tracker testing resulted in very low plastic deformation and minor material rutting with use of the studded rubber tire. The test slab showed very minor surface wear, no freeze-thaw cracking and no rutting after one winter of use. It is recommended that further testing of the material be conducted by means of a large-scale trial section. This would provide information with respect to cost analysis and

  16. Effect of post-curing treatment on mechanical properties of composite resins.

    Science.gov (United States)

    Almeida-Chetti, Verónica A; Macchi, Ricardo L; Iglesias, María E

    2014-01-01

    The aim of this study is to assess the effect of additional curing procedures on the flexural strength and modulus of elasticity of indirect and direct composite materials. Twenty-four rectangular prism-shaped 2 mm x 2 mm x 25 mm samples of Belleglass, Premisa (Kerr), Adoro and Heliomolar (Ivoclar Vivadent) were prepared. Each composite was packed in an ad-hoc stainless steel device with a TeflonR instrument. A mylar strip and a glass slab were placed on top to obtain a flat surface. Polymerization was activated for 20 seconds with a halogen unit (Astralis 10, Ivoclar - Vivadent) with soft start regime and an output with a 350 to 1200 mw/cm2 range at four different points according to the diameter of the end of the guide. The specimens obtained were then randomly divided into two different groups: with and without additional treatment. In the group with additional treatment, the samples adorro were submitted to 25 minutes in Lumamat 100 (Ivoclar Vivadent) and the rest to 20 minutes in BelleGlass HP (Kerr). After the curing procedures, all samples were treated with sandpapers of decreasing grain size under water flow, and stored in distilled water for 24 h. Flexural strength was measured according to the ISO 404920 recommendations and elastic modulus was determined following the procedures of ANSI/ADA standard No. 27. Statistical differences were found among the different materials and curing procedures employed (Pcomposites, and its clinical relevance.

  17. Producing ceramic laminate composites by EPD

    International Nuclear Information System (INIS)

    Nicholson, P.S.; Sarkar, P.; Datta, S.

    1996-01-01

    The search for tough structural ceramics to operate at high temperatures in hostile environments has led to the development of ceramic composites. This class of material includes laminar ceramic-ceramic composites, continuous-fiber-reinforced ceramic composites and functionally graded materials. The present authors developed electrophoretic deposition (EPD) to synthesize lamellar, fiber-reinforced and functionally graded composites. This paper briefly describes the synthesis and characterization of these EPD composites and introduces a novel class of lamellar composites with nonplanar layers. The synthesis of the latter demonstrates the facility of the EPD process for the synthesis of ceramic composites. The process is totally controllable via suspension concentration, deposition current, voltage and time

  18. Post-fire salvage logging alters species composition and reduces cover, richness, and diversity in Mediterranean plant communities.

    Science.gov (United States)

    Leverkus, Alexandro B; Lorite, Juan; Navarro, Francisco B; Sánchez-Cañete, Enrique P; Castro, Jorge

    2014-01-15

    An intense debate exists on the effects of post-fire salvage logging on plant community regeneration, but scant data are available derived from experimental studies. We analyzed the effects of salvage logging on plant community regeneration in terms of species richness, diversity, cover, and composition by experimentally managing a burnt forest on a Mediterranean mountain (Sierra Nevada, S Spain). In each of three plots located at different elevations, three replicates of three treatments were implemented seven months after the fire, differing in the degree of intervention: "Non-Intervention" (all trees left standing), "Partial Cut plus Lopping" (felling 90% of the trees, cutting the main branches, and leaving all the biomass in situ), and "Salvage Logging" (felling and piling the logs, and masticating the woody debris). Plant composition in each treatment was monitored two years after the fire in linear point transects. Post-fire salvage logging was associated with reduced species richness, Shannon diversity, and total plant cover. Moreover, salvaged sites hosted different species assemblages and 25% lower cover of seeder species (but equal cover of resprouters) compared to the other treatments. Cover of trees and shrubs was also lowest in Salvage Logging, which could suggest a potential slow-down of forest regeneration. Most of these results were consistent among the three plots despite plots hosting different plant communities. Concluding, our study suggests that salvage logging may reduce species richness and diversity, as well as the recruitment of woody species, which could delay the natural regeneration of the ecosystem. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Dynamic displacements of the RHIC dipole cold mass with injection molded composite posts during quench conditions

    International Nuclear Information System (INIS)

    Sondericker, J.; Wolf, L.J.

    1991-02-01

    The new design of the RHIC dipole magnets incorporate helium containment bellows having a convolution diameter of only 7.63 inches. The present bellows are 12.80 inches in diameter. The smaller bellows present a substantially reduced pressure area which can be expected to reduce proportionately the end force on the cold mass during a quench. But, the objection was raised that the smaller bellows would present greater obstruction to the helium flow during a quench thereby producing higher pressure differentials. This analysis was undertaken to address these assertions by predicting the dynamic displacements of the cold mass using the latest test data on the stiffness of the IMC posts, pressure-time histories acquired from the recent full cell tests of RHIC magnets, and the dimensions of the new expansion joints. The analysis treated the cold mass as an elastic body having a saggittal curvature. The technique of normal mode expansion of a lumped-parameter system was used to obtain the results and conclusions reported herein

  20. Wear-resistant and electromagnetic absorbing behaviors of oleic acid post-modified ferrite-filled epoxy resin composite coating

    Science.gov (United States)

    Wang, Wenjie; Zang, Chongguang; Jiao, Qingjie

    2015-03-01

    The post-modified Mn-Zn ferrite was prepared by grafting oleic acid on the surface of Mn-Zn ferrite to inhibit magnetic nanoparticle aggregation. Fourier Transform Infrared (FT-IR) spectroscopy was used to characterize the particle surfaces. The friction and electromagnetic absorbing properties of a thin coating fabricated by dispersing ferrite into epoxy resin (EP) were investigated. The roughness of the coating and water contact angle were measured using the VEECO and water contact angle meter. Friction tests were conducted using a stainless-steel bearing ball and a Rockwell diamond tip, respectively. The complex permittivity and complex permeability of the composite coating were studied in the low frequency (10 MHz-1.5 GHz). Surface modified ferrites are found to improve magnetic particles dispersion in EP resulting in significant compatibility between inorganic and organic materials. Results also indicate that modified ferrite/EP coatings have a lower roughness average value and higher water contact angle than original ferrite/EP coatings. The enhanced tribological properties of the modified ferrite/EP coatings can be seen from the increased coefficient value. The composite coatings with modified ferrite are observed to exhibit better reflection loss compared with the coatings with original ferrite.

  1. Lunar bulk chemical composition: a post-Gravity Recovery and Interior Laboratory reassessment.

    Science.gov (United States)

    Taylor, G Jeffrey; Wieczorek, Mark A

    2014-09-13

    New estimates of the thickness of the lunar highlands crust based on data from the Gravity Recovery and Interior Laboratory mission, allow us to reassess the abundances of refractory elements in the Moon. Previous estimates of the Moon fall into two distinct groups: earthlike and a 50% enrichment in the Moon compared with the Earth. Revised crustal thicknesses and compositional information from remote sensing and lunar samples indicate that the crust contributes 1.13-1.85 wt% Al2O3 to the bulk Moon abundance. Mare basalt Al2O3 concentrations (8-10 wt%) and Al2O3 partitioning behaviour between melt and pyroxene during partial melting indicate mantle Al2O3 concentration in the range 1.3-3.1 wt%, depending on the relative amounts of pyroxene and olivine. Using crustal and mantle mass fractions, we show that that the Moon and the Earth most likely have the same (within 20%) concentrations of refractory elements. This allows us to use correlations between pairs of refractory and volatile elements to confirm that lunar abundances of moderately volatile elements such as K, Rb and Cs are depleted by 75% in the Moon compared with the Earth and that highly volatile elements, such as Tl and Cd, are depleted by 99%. The earthlike refractory abundances and depleted volatile abundances are strong constraints on lunar formation processes. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  2. Characterization of mesoporous VOx/MCM-41 composite materials obtained via post-synthesis impregnation

    International Nuclear Information System (INIS)

    Bukallah, Saeed B.; Bumajdad, Ali; Khalil, Kamal M.S.; Zaki, Mohamed I.

    2010-01-01

    Spherical-particle MCM-41 was synthesized at room temperature, and, then, impregnated with aqueous solutions of NH 4 VO 3 to produce variously loaded VO x /MCM-41 composite materials. Bulk and surface properties of the materials thus produced were characterized by means of X-ray powder diffractometry (XRD), infrared spectroscopy (FTIR), N 2 sorptiometry and X-ray photoelectron spectroscopy (XPS). Results obtained indicated that subsequent calcination at 550 deg. C (for 2 h) of the blank and impregnated MCM-41 particles, results in materials assuming the same bulk structure of MCM-41, and exposing uniformly mesporous, high area surfaces (P w = 2.0-2.3 nm; 974-829 m 2 /g), except for the material obtained at 20 wt%-V 2 O 5 that was shown to suffer a considerable loss on surface area (down to 503 m 2 /g). XPS results implied that the immobilization of the VO x species occurs via interaction with surface OH/H 2 O groups of MCM-41, leading to the formation of vanadate (VO 3 - ) surface species, as well as minor V-O-Si and V 2 O 5 -like species. However, in all cases, the vanadium sites remained pentavalent and exposed on the surface.

  3. Laser surface treatment for enhanced titanium to carbon fiber-reinforced polymer adhesion

    NARCIS (Netherlands)

    Palavra, Armin; Coelho, Bruno N.; de Hosson, Jeff Th. M.; Lima, Milton S. F.; Carvalho, Sheila M.; Costa, Adilson R.

    The adhesion between carbon fiber-reinforced polymer (CFRP) and titanium parts can be improved by laser surface texturing before gluing them together. Here, a pulsed Nd:YAG laser was employed before bonding of the textured surfaces using an epoxy paste adhesive. To investigate the influence of the

  4. Bending strength and fracture surface topography of natural fiber-reinforced shell for investment casting process

    Directory of Open Access Journals (Sweden)

    Kai Lu

    2016-05-01

    Full Text Available In order to improve the properties of silica sol shell for investment casting process, various contents of cattail fibers were added into the slurry to prepare a fiber-reinforced shell in the present study. The bending strength of fiber-reinforced shell was investigated and the fracture surfaces of shell specimens were observed using SEM. It is found that the bending strength increases with the increase of fiber content, and the bending strength of a green shell with 1.0 wt.% fiber addition increases by 44% compared to the fiber-free shell. The failure of specimens of the fiber-reinforced green shell results from fiber rupture and debonding between the interface of fibers and adhesive under the bending load. The micro-crack propagation in the matrix is inhibited by the micro-holes for ablation of fibers in specimens of the fiber-reinforced shell during the stage of being fired. As a result, the bending strength of specimens of the fired shell had no significant drop. Particularly, the bending strength of specimens of the fired shell reinforced with 0.6wt.% fiber reached the maximum value of 4.6 MPa.

  5. Infants' Peripheral Blood Lymphocyte Composition Reflects Both Maternal and Post-Natal Infection with Plasmodium falciparum.

    Directory of Open Access Journals (Sweden)

    Odilon Nouatin

    Full Text Available Maternal parasitoses modulate fetal immune development, manifesting as altered cellular immunological activity in cord blood that may be linked to enhanced susceptibility to infections in early life. Plasmodium falciparum typifies such infections, with distinct placental infection-related changes in cord blood exemplified by expanded populations of parasite antigen-specific regulatory T cells. Here we addressed whether such early-onset cellular immunological alterations persist through infancy. Specifically, in order to assess the potential impacts of P. falciparum infections either during pregnancy or during infancy, we quantified lymphocyte subsets in cord blood and in infants' peripheral blood during the first year of life. The principal age-related changes observed, independent of infection status, concerned decreases in the frequencies of CD4+, NKdim and NKT cells, whilst CD8+, Treg and Teff cells' frequencies increased from birth to 12 months of age. P. falciparum infections present at delivery, but not those earlier in gestation, were associated with increased frequencies of Treg and CD8+ T cells but fewer CD4+ and NKT cells during infancy, thus accentuating the observed age-related patterns. Overall, P. falciparum infections arising during infancy were associated with a reversal of the trends associated with maternal infection i.e. with more CD4+ cells, with fewer Treg and CD8+ cells. We conclude that maternal P. falciparum infection at delivery has significant and, in some cases, year-long effects on the composition of infants' peripheral blood lymphocyte populations. Those effects are superimposed on separate and independent age- as well as infant infection-related alterations that, respectively, either match or run counter to them.

  6. Relationships between anthropometric features, body composition, and anaerobic alactic power in elite post-pubertal and mature male taekwondo athletes

    Directory of Open Access Journals (Sweden)

    Boraczyński Michał

    2017-12-01

    Full Text Available Purpose. The paper describes the relationships between anthropometric features, body composition, and anaerobic alactic power (AAP in elite post-pubertal and mature male taekwondo athletes. Methods. The sample of 41 taekwondo athletes was divided into two groups: post-pubertal (P-P, n = 19, Mage = 15.6 ± 1.1 years and mature (M, n = 22, Mage = 20.7 ± 2.8 years. Anthropometric features (WB-150, ZPU Tryb-Wag, Poland, body composition (BC-418 MA, Tanita, Japan, maturational status (Pubertal Maturational Observational Scale, and AAP (10-s version of the Wingate Anaerobic Test were assessed. Results. Post-hoc testing revealed significant between-group differences (3.2-20.4%, p < 0.01 in all anthropometric and body composition measures, with effect sizes (ES between −0.79 and −1.25 (p < 0.001, except for fat content and percentage of skeletal muscle mass (SMM (p ≥ 0.05. In group M, the maximal power output (Pmax was greater (ES = −1.15, p < 0.001 and the time of its attainment shorter (ES = 0.59, p < 0.001 than in group P-P. Correlation analyses indicated notably strong associations between body mass (BM and Pmax in group P-P (r = 0.950 [95% CI, 0.85-0.98], p < 0.001 and M (r = 0.926 [95% CI, 0.81-0.97], p < 0.001, and similar-sized strong correlations between fat-free mass (FFM and Pmax in group P-P (r = 0.955 [95% CI, 0.86-0.99], p < 0.001 and M (r = 0.924 [95% CI, 0.82-0.96], p < 0.001. Additionally, a strong correlation was found between body height and Pmax in groups P-P and M (r = 0.805 [95% CI, 0.54-0.92], p < 0.001 and r = 0.819 [95% CI, 0.58-0.93], p < 0.001, respectively. Linear regression analyses demonstrated that FFM, BM, and absolute SMM best explained the variance in Pmax in both groups (r, 0.939-0.951; r2, 0.882-0.909. Conclusions. The strong correlations observed in both groups between BM, FFM, SMM, and Pmax demonstrate the significant effects of body size and composition on AAP. By determining the current levels of these

  7. Analysis of Damage in a Ceramic Matrix Composite

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Talreja, Ramesh

    1993-01-01

    Mechanisms of damage and the associated mechanical response are stud ied for a unidirectionally fiber-reinforced ceramic matrix composite subjected to uniaxial tensile loading parallel to fibers. A multi-stage development of damage is identified, and for each stage the governing mechanisms...

  8. Fracture strength and fatigue resistance of dental resin-based composites

    NARCIS (Netherlands)

    Keulemans, F.; Palav, P.; Aboushelib, M.M.N.; van Dalen, A.; Kleverlaan, C.J.; Feilzer, A.J.

    2009-01-01

    Objectives: The aim of this study was to evaluate in vitro the influence of fiber-reinforcement on the fracture strength and fatigue resistance of resin-based composites. Methods: One hundred rectangular bar-shaped specimens (2 mm × 2 mm × 25 mm) made of resin-based composite were prepared in a

  9. Comparative study of adhesive joint designs for composite trusses based on numerical models

    NARCIS (Netherlands)

    Lavalette, N.P.; Bergsma, O.K.; Zarouchas, D.; Benedictus, R.

    2017-01-01

    In the context of lightweight structure design for the transportation and robotics industries, new types of composite structures are being developed, in the form of trusses made of fiber-reinforced polymer composite members of small diameter (a few millimeters thick at most). Some concepts of

  10. Experimental and numerical study of the micro-mechanical failure in composites

    DEFF Research Database (Denmark)

    Ashouri Vajari, Danial; Martyniuk, Karolina; Sørensen, Bent F.

    2013-01-01

    The fibre/matrix interfacial debonding is found to be the first microscale failure mechanism leading to subsequent macroscale transverse cracks in composite materials under tensile load. In this paper, the micromechanical interface failure in fiber-reinforced composites is studied experimentally ...

  11. Preparation and characterisation of poly p-phenylene-2,6-benzobisoxazole fibre-reinforced resin matrix composite for endodontic post material: a preliminary study.

    Science.gov (United States)

    Hu, Chen; Wang, Feng; Yang, Huiyong; Ai, Jun; Wang, Linlin; Jing, Dongdong; Shao, Longquan; Zhou, Xingui

    2014-12-01

    Currently used fibre-reinforced composite (FRC) intracanal posts possess low flexural strength which usually causes post fracture when restoring teeth with extensive loss. To improve the flexural strength of FRC, we aimed to apply a high-performance fibre, poly p-phenylene-2, 6-benzobisoxazole (PBO), to FRCs to develop a new intracanal post material. To improve the interfacial adhesion strength, the PBO fibre was treated with coupling agent (Z-6040), argon plasma, or a combination of above two methods. The effects of the surface modifications on PBO fibre were characterised by determining the single fibre tensile strength and interfacial shear strength (IFSS). The mechanical properties of PBO FRCs were characterised by flexural strength and flexural modulus. The cytotoxicity of PBO FRC was evaluated by the MTT assay. Fibres treated with a combination of Z-6040 and argon plasma possessed a significantly higher IFSS than untreated fibres. Fibre treated with the combination of Z-6040-argon-plasma FRC had the best flexural strength (531.51 ± 26.43MPa) among all treated fibre FRCs and had sufficient flexural strength and appropriate flexural moduli to be used as intracanal post material. Furthermore, an in vitro cytotoxicity assay confirmed that PBO FRCs possessed an acceptable level of cytotoxicity. In summary, our study verified the feasibility of using PBO FRC composites as new intracanal post material. Although the mechanical property of PBO FRC still has room for improvement, our study provides a new avenue for intracanal post material development in the future. To our knowledge, this is the first study to verify the feasibility of using PBO FRC composites as new intracanal post material. Our study provided a new option for intracanal post material development. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Effects of post-heat treatment on microstructure and properties of laser cladded composite coatings on titanium alloy substrate

    Science.gov (United States)

    Li, G. J.; Li, J.; Luo, X.

    2015-01-01

    The composite coatings were produced on the Ti6Al4V alloy substrate by laser cladding. Subsequently, the coatings were heated at 500 °C for 1 h and 2 h and then cooled in air. Effects of post-heat treatment on microstructure, microhardness and fracture toughness of the coatings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), optical microscopy (OM). Wear resistance of the coatings was evaluated under the dry sliding reciprocating friction condition at room temperature. The results indicated that the coatings mainly consist of a certain amount of coarse white equiaxed WC particles surrounded by the white-bright W2C, a great deal of fine dark spherical TiC particles and the matrix composed of the α(Ti), Ti2Ni and TiNi phases. Effects of the post-heat treatment on phase constituents and microstructure of the coatings were almost negligible due to the low temperature. However, the post-heat treatment could decrease the residual stress and increase fracture toughness of the coatings, and fracture toughness of the coatings was improved from 2.77 MPa m1/2 to 3.80 MPa m1/2 and 4.43 MPa m1/2 with the heat treatment for 1 h and 2 h, respectively. The mutual role would contribute to the reduction in cracking susceptibility. Accompanied with the increase in fracture toughness, microhardness of the coatings was reduced slightly. The dominant wear mechanism for all the coatings was abrasive wear, characterized by micro-cutting or micro-plowing. The heat treatment could significantly decrease the average friction coefficient and reduce the fluctuation of the friction coefficient with the change in sliding time. The appropriate heat treatment time (approximately 1 h) had a minimal effect on wear mass loss and volume loss. Moreover, the improvement in fracture toughness will also be beneficial to wear resistance of the coatings under the long service.

  13. Synthesis and characterization polymer composites prepared by low-temperature post-irradiation polymerization of C_2F_4 in the presence of graphene-like material

    International Nuclear Information System (INIS)

    Shulga, Y.M.; Kiryukhin, D.P.; Vasilets, V.N.

    2015-01-01

    Polymer polytetrafluoroethylene (Ptfe)-microwave exfoliated graphene oxide (MEGO) composites containing up to 80 wt.% PTFE were prepared by low-temperature post-irradiation polymerization of C_2F_4 in the presence of the graphene-like material. Composites were characterized by elemental analysis, XPS, NMR, and DSC techniques. The melting point of PTFE in the composite (332.5°C) was higher than that of pure PTFE by 8.8°C. The measured values of the melting enthalpy (ΔHm=51.5 and 45.4 J/g) were used to calculate the extent of crystallinity in the PTFE and PTFE-MEGO composite (0.63 and 0.55, respectively). No - CF_3 end groups typical of commercial PTFE have been detected in the PTFE-MEGO composites. (authors)

  14. Evaluation of plant species composition after thirteen years post coal mining rehabilitation in East Kutai District of East Kalimantan, Indonesia

    Science.gov (United States)

    Komara, L. L.; Murtinah, V.; Arbain

    2018-04-01

    Coal mining leaving large overburden which needs to be rehabilitated by conducting reclamation and re-vegetation. This study objective was to evaluate plant species composition after thirteen years of re-vegetation activities in a coal mining rehabilitation site in KutaiTimur District, East Kalimantan, with coordinate 00º33’23”-00º38’17” NL and 117º23’55”-117º23’20” EL. This study compared rehabilitation site with the natural forest conditions sites. There were found 28 plant species in the rehabilitation site, consisting of 19 wood species (Cassia siamea and Ficus uncinata) and 9 non-wood species (Nephrolepis biserata and Miscanthus javanica).In comparison, 36 species were found in the natural forest condition, consisting of 25 woody species (Nephelium eriopetalum and Macaranga hypoleuca)and 11 non-wood species (Fordia splendidisima and Saurauia umbellata). Woody species diversity indices in the rehabilitation site after 13 years post mining (i.e., 2,21) was lower than in the natural forest sites (3,01); while the diversity indices for non-wood species were relatively similar (1,48 and 1,96 in the rehabilitation and natural forest sites respectively). Species richness of non-wood species was low, but it has a high coverage per species in this site.To restore rehabilitation site woody species to its assumed natural conditions, 22woody species should be planted.

  15. Substitution potentials of recycled HDPE and wood particles from post-consumer packaging waste in Wood-Plastic Composites.

    Science.gov (United States)

    Sommerhuber, Philipp F; Welling, Johannes; Krause, Andreas

    2015-12-01

    The market share of Wood-Plastic Composites (WPC) is small but expected to grow sharply in Europe. This raises some concerns about suitable wood particles needed in the wood-based panels industry in Europe. Concerns are stimulated by the competition between the promotion of wooden products through the European Bioeconomy Strategy and wood as an energy carrier through the Renewable Energy Directive. Cascade use of resources and valorisation of waste are potential strategies to overcome resource scarcity. Under experimental design conditions, WPC made from post-consumer recycled wood and plastic (HDPE) were compared to WPC made from virgin resources. Wood content in the polymer matrix was raised in two steps from 0% to 30% and 60%. Mechanical and physical properties and colour differences were characterized. The feasibility of using cascaded resources for WPC is discussed. Results indicate the technical and economic feasibility of using recycled HDPE from packaging waste for WPC. Based on technical properties, 30% recycled wood content for WPC is feasible, but economic and political barriers of efficient cascading of biomass need to be overcome. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Hybrid fiber and nanopowder reinforced composites for wind turbine blades

    Directory of Open Access Journals (Sweden)

    Nikoloz M. Chikhradze

    2015-01-01

    Full Text Available The results of an investigation into the production of wind turbine blades manufactured using polymer composites reinforced by hybrid (carbon, basalt, glass fibers and strengthened by various nanopowders (oxides, carbides, borides are presented. The hybrid fiber-reinforced composites (HFRC were manufactured with prepreg technology by molding pre-saturated epoxy-strengthened matrix-reinforced fabric. Performance of the manufactured composites was estimated with values of the coefficient of operating condition (COC at a moderate and elevated temperature.

  17. Reversible dielectric property degradation in moisture-contaminated fiber-reinforced laminates

    Science.gov (United States)

    Rodriguez, Luis A.; García, Carla; Fittipaldi, Mauro; Grace, Landon R.

    2016-03-01

    The potential for recovery of dielectric properties of three water-contaminated fiber-reinforced laminates is investigated using a split-post dielectric resonant technique at X-band (10 GHz). The three material systems investigated are bismaleimide (BMI) reinforced with an eight-harness satin weave quartz fabric, an epoxy resin reinforced with an eight- harness satin weave glass fabric (style 7781), and the same epoxy reinforced with a four-harness woven glass fabric (style 4180). A direct correlation between moisture content, dielectric constant, and loss tangent was observed during moisture absorption by immersion in distilled water at 25 °C for five equivalent samples of each material system. This trend is observed through at least 0.72% water content by weight for all three systems. The absorption of water into the BMI, 7781 epoxy, and 4180 epoxy laminates resulted in a 4.66%, 3.35%, and 4.01% increase in dielectric constant for a 0.679%, 0.608%, and 0.719% increase in water content by weight, respectively. Likewise, a significant increase was noticed in loss tangent for each material. The same water content is responsible for a 228%, 71.4%, and 64.1% increase in loss tangent, respectively. Subsequent to full desorption through drying at elevated temperature, the dielectric constant and loss tangent of each laminate exhibited minimal change from the dry, pre-absorption state. The dielectric constant and loss tangent change after the absorption and desorption cycle, relative to the initial state, was 0.144 % and 2.63% in the BMI, 0.084% and 1.71% in the style 7781 epoxy, and 0.003% and 4.51% in the style 4180 epoxy at near-zero moisture content. The similarity of dielectric constant and loss tangent in samples prior to absorption and after desorption suggests that any chemical or morphological changes induced by the presence of water have not caused irreversible changes in the dielectric properties of the laminates.

  18. Multi-material Preforming of Structural Composites

    Energy Technology Data Exchange (ETDEWEB)

    Norris, Robert E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Eberle, Cliff C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pastore, Christopher M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sudbury, Thomas Z. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Xiong, Fue [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hartman, David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-05-01

    Fiber-reinforced composites offer significant weight reduction potential, with glass fiber composites already widely adopted. Carbon fiber composites deliver the greatest performance benefits, but their high cost has inhibited widespread adoption. This project demonstrates that hybrid carbon-glass solutions can realize most of the benefits of carbon fiber composites at much lower cost. ORNL and Owens Corning Reinforcements along with program participants at the ORISE collaborated to demonstrate methods for produce hybrid composites along with techniques to predict performance and economic tradeoffs. These predictions were then verified in testing coupons and more complex demonstration articles.

  19. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2011-01-01

    Strategies are open compositions to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them in full...

  20. Composition

    DEFF Research Database (Denmark)

    2014-01-01

    Memory Pieces are open compositions to be realised solo by an improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them...

  1. Development and Characterization of UHMWPE Fiber-Reinforced Hydrogels For Meniscal Replacement

    Science.gov (United States)

    Holloway, Julianne Leigh

    Meniscal tears are the most common orthopedic injuries to the human body. The current treatment of choice, however, is a partial meniscectomy that leads to osteoarthritis proportional to the amount of tissue removed. As a result, there is a significant clinical need to develop materials capable of restoring the biomechanical contact stress distribution to the knee after meniscectomy and preventing the onset of osteoarthritis. In this work, a fiber-reinforced hydrogel-based synthetic meniscus was developed that allows for tailoring of the mechanical properties and molding of the implant to match the size, shape, and property distribution of the native tissue. Physically cross-linked poly(vinyl alcohol) (PVA) hydrogels were reinforced with ultrahigh molecular weight polyethylene (UHMWPE) fibers and characterized in compression (0.1-0.8 MPa) and tension (0.1-250 MPa) showing fine control over mechanical properties within the range of the human meniscus. Morphology and crystallinity analysis of PVA hydrogels showed increases in crystallinity and PVA densification, or phase separation, with freeze-thaw cycles. A comparison of freeze-thawed and aged, physically cross-linked hydrogels provided insight on both crystallinity and phase separation as mechanisms for PVA gelation. Results indicated both mechanisms independently contributed to hydrogel modulus for freeze-thawed hydrogels. In vitro swelling studies were performed using osmotic solutions to replicate the swelling pressure present in the knee. Minimal swelling was observed for hydrogels with a PVA concentration of 30-35 wt%, independently of hydrogel freeze-thaw cycles. This allows for independent tailoring of hydrogel modulus and pore structure using freeze-thaw cycles and swelling behavior using polymer concentration to match a wide range of properties needed for various soft tissue applications. The UHMWPE-PVA interface was identified as a significant weakness. To improve interfacial adhesion, a novel

  2. Effects of management intervention on post-disturbance community composition: an experimental analysis using bayesian hierarchical models.

    Directory of Open Access Journals (Sweden)

    Jack Giovanini

    Full Text Available As human demand for ecosystem products increases, management intervention may become more frequent after environmental disturbances. Evaluations of ecological responses to cumulative effects of management interventions and natural disturbances provide critical decision-support tools for managers who strive to balance environmental conservation and economic development. We conducted an experiment to evaluate the effects of salvage logging on avian community composition in lodgepole pine (Pinus contorta forests affected by beetle outbreaks in Oregon, USA, 1996-1998. Treatments consisted of the removal of lodgepole pine snags only, and live trees were not harvested. We used a bayesian hierarchical model to quantify occupancy dynamics for 27 breeding species, while accounting for variation in the detection process. We examined how magnitude and precision of treatment effects varied when incorporating prior information from a separate intervention study that occurred in a similar ecological system. Regardless of which prior we evaluated, we found no evidence that the harvest treatment had a negative impact on species richness, with an estimated average of 0.2-2.2 more species in harvested stands than unharvested stands. Estimated average similarity between control and treatment stands ranged from 0.82-0.87 (1 indicating complete similarity between a pair of stands and suggested that treatment stands did not contain novel assemblies of species responding to the harvesting prescription. Estimated treatment effects were positive for twenty-four (90% of the species, although the credible intervals contained 0 in all cases. These results suggest that, unlike most post-fire salvage logging prescriptions, selective harvesting after beetle outbreaks may meet multiple management objectives, including the maintenance of avian community richness comparable to what is found in unharvested stands. Our results provide managers with prescription alternatives to

  3. Assessment of the Mechanical Properties of Sisal Fiber-Reinforced Silty Clay Using Triaxial Shear Tests

    Directory of Open Access Journals (Sweden)

    Yankai Wu

    2014-01-01

    Full Text Available Fiber reinforcement is widely used in construction engineering to improve the mechanical properties of soil because it increases the soil’s strength and improves the soil’s mechanical properties. However, the mechanical properties of fiber-reinforced soils remain controversial. The present study investigated the mechanical properties of silty clay reinforced with discrete, randomly distributed sisal fibers using triaxial shear tests. The sisal fibers were cut to different lengths, randomly mixed with silty clay in varying percentages, and compacted to the maximum dry density at the optimum moisture content. The results indicate that with a fiber length of 10 mm and content of 1.0%, sisal fiber-reinforced silty clay is 20% stronger than nonreinforced silty clay. The fiber-reinforced silty clay exhibited crack fracture and surface shear fracture failure modes, implying that sisal fiber is a good earth reinforcement material with potential applications in civil engineering, dam foundation, roadbed engineering, and ground treatment.

  4. Fracture resistance of abutment screws made of titanium, polyetheretherketone, and carbon fiber-reinforced polyetheretherketone

    Directory of Open Access Journals (Sweden)

    Eduardo Aloisio Fleck NEUMANN

    2014-08-01

    Full Text Available Fractured abutment screws may be replaced; however, sometimes, the screw cannot be removed and the entire implant must be surgically removed and replaced. The aim of this study was to compare the fracture resistance of abutment retention screws made of titanium, polyetheretherketone (PEEK and 30% carbon fiber-reinforced PEEK, using an external hexagonal implant/UCLA-type abutment interface assembly. UCLA-type abutments were fixed to implants using titanium screws (Group 1, polyetheretherketone (PEEK screws (Group 2, and 30% carbon fiber-reinforced PEEK screws (Group 3. The assemblies were placed on a stainless steel holding apparatus to allow for loading at 45o off-axis, in a universal testing machine. A 200 N load (static load was applied at the central point of the abutment extremity, at a crosshead speed of 5 mm/minute, until failure. Data was analyzed by ANOVA and Tukey’s range test. The titanium screws had higher fracture resistance, compared with PEEK and 30% carbon fiber-reinforced PEEK screws (p 0.05. Finally, visual analysis of the fractions revealed that 100% of them occurred at the neck of the abutment screw, suggesting that this is the weakest point of this unit. PEEK abutment screws have lower fracture resistance, in comparison with titanium abutment screws.

  5. Fracture resistance of abutment screws made of titanium, polyetheretherketone, and carbon fiber-reinforced polyetheretherketone.

    Science.gov (United States)

    Neumann, Eduardo Aloisio Fleck; Villar, Cristina Cunha; França, Fabiana Mantovani Gomes

    2014-01-01

    Fractured abutment screws may be replaced; however, sometimes, the screw cannot be removed and the entire implant must be surgically removed and replaced. The aim of this study was to compare the fracture resistance of abutment retention screws made of titanium, polyetheretherketone (PEEK) and 30% carbon fiber-reinforced PEEK, using an external hexagonal implant/UCLA-type abutment interface assembly. UCLA-type abutments were fixed to implants using titanium screws (Group 1), polyetheretherketone (PEEK) screws (Group 2), and 30% carbon fiber-reinforced PEEK screws (Group 3). The assemblies were placed on a stainless steel holding apparatus to allow for loading at 45o off-axis, in a universal testing machine. A 200 N load (static load) was applied at the central point of the abutment extremity, at a crosshead speed of 5 mm/minute, until failure. Data was analyzed by ANOVA and Tukey's range test. The titanium screws had higher fracture resistance, compared with PEEK and 30% carbon fiber-reinforced PEEK screws (p 0.05). Finally, visual analysis of the fractions revealed that 100% of them occurred at the neck of the abutment screw, suggesting that this is the weakest point of this unit. PEEK abutment screws have lower fracture resistance, in comparison with titanium abutment screws.

  6. SEM in situ laboratory investigations on damage growth in GFRP composite under three-point bending tests

    DEFF Research Database (Denmark)

    Zhou, Hong Wei; Mishnaevsky, Leon; Brøndsted, Povl

    2010-01-01

    Glass fiber-reinforced polymer (GFRP) composites are widely used in low-weight constructions. SEM (scanning electron microscopy) in situ experiments of damage growth in GFRP composite under three-point bending loads are carried out. By summarizing the experimental results of three groups of samples...

  7. Oxidation of SiC/BN/SiC Composites in Reduced Oxygen Partial Pressures

    Science.gov (United States)

    Opila, Elizabeth J.; Boyd, Meredith

    2010-01-01

    SiC fiber-reinforced SiC composites with a BN interphase are proposed for use as leading edge structures of hypersonic vehicles. The durability of these materials under hypersonic flight conditions is therefore of interest. Thermogravimetric analysis was used to characterize the oxidation kinetics of both the constituent fibers and composite coupons at four temperatures: 816, 1149, 1343, and 1538 C (1500, 2100, 2450, and 2800 F) and in oxygen partial pressures between 5% and 0.1% (balance argon) at 1 atm total pressure. One edge of the coupons was ground off so the effects of oxygen ingress into the composite could be monitored by post-test SEM and EDS. Additional characterization of the oxidation products was conducted by XPS and TOF-SIMS. Under most conditions, the BN oxidized rapidly, leading to the formation of borosilicate glass. Rapid initial oxidation followed by volatilization of boria lead to protective oxide formation and further oxidation was slow. At 1538C in 5% oxygen, both the fibers and coupons exhibited borosilicate glass formation and bubbling. At 1538C in 0.1% oxygen, active oxidation of both the fibers and the composites was observed leading to rapid SiC degradation. BN oxidation at 1538C in 0.1% oxygen was not significant.

  8. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2014-01-01

    Cue Rondo is an open composition to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound/video files will in some cases only provide a few minutes' sample, or the visuals will not appear at all....... Please DOWNLOAD them to see/hear them in full length! This work is licensed under a Creative Commons "by-nc" License. You may for non-commercial purposes use and distribute it, performance instructions as well as specially designated recordings, as long as the author is mentioned. Please see http...

  9. Flight-vehicle materials, structures, and dynamics - Assessment and future directions. Vol. 3 - Ceramics and ceramic-matrix composites

    Science.gov (United States)

    Levine, Stanley R. (Editor)

    1992-01-01

    The present volume discusses ceramics and ceramic-matrix composites in prospective aerospace systems, monolithic ceramics, transformation-toughened and whisker-reinforced ceramic composites, glass-ceramic matrix composites, reaction-bonded Si3N4 and SiC composites, and chemical vapor-infiltrated composites. Also discussed are the sol-gel-processing of ceramic composites, the fabrication and properties of fiber-reinforced ceramic composites with directed metal oxidation, the fracture behavior of ceramic-matrix composites (CMCs), the fatigue of fiber-reinforced CMCs, creep and rupture of CMCs, structural design methodologies for ceramic-based materials systems, the joining of ceramics and CMCs, and carbon-carbon composites.

  10. Ceramic fiber reinforced glass-ceramic matrix composite

    Science.gov (United States)

    Bansal, Narottam P. (Inventor)

    1993-01-01

    A slurry of BSAS glass powders is cast into tapes which are cut to predetermined sizes. Mats of continuous chemical vapor deposition (CVD)-SiC fibers are alternately stacked with these matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite which is heated to burn out organic constituents. The remaining interim material is then hot-pressed to form a BSAS glass-ceramic fiber-reinforced composite.

  11. Return to the Strangelove Ocean?: Preliminary results of carbon and oxygenisotope compositions of post-impact sediments, IODP Expedition 364 "Chicxulub Impact Crater"

    Science.gov (United States)

    Yamaguchi, K. E.; Ikehara, M.; Hayama, H.; Takiguchi, S.; Masuda, S.; Ogura, C.; Fujita, S.; Kurihara, E.; Matsumoto, T.; Oshio, S.; Ishihata, K.; Fuchizawa, Y.; Noda, H.; Sakurai, U.; Yamane, T.; Morgan, J. V.; Gulick, S. P. S.

    2017-12-01

    The Chicxulub crater in the northern Yucatan Peninsula, Mexico was formed by the asteroid impact at the Cretaceous-Paleogene boundary (66.0 Ma). In early 2016 the IODP Exp. 364 successfully drilled the materials from the topographic peak ring within the crater that was previously identified by seismological observations. A continuous core was recovered. The 112m-thick uppermost part of the continuous core (505.7-1334.7 mbsf) is post-impact sediments, including the PETM, that are mainly composed of carbonate with intercalation of siliciclastics and variable contents of organic carbon. More than 300 samples from the post-impact section were finely powdered for a variety of geochemical analysis. Here we report their carbon and oxygen isotope compositions of the carbonate fraction (mostly in the lower part of the analyzed section) and carbon and nitrogen isotope compositions of organic matter (mostly in the middle-upper part of the analyzed section). Isotope mass spectrometer Isoprime was used for the former analysis, and EA-irMS (elemental analyzer - isotope ratio mass spectrometer) was used for the latter analysis, both at CMCR, Kochi Univ. Depth profile of oxygen isotope compositions of carbonate fraction is variable and somewhat similar to those of Zachos et al. (2001; Science). Carbon isotope compositions of carbonate and organic carbon in the lower part of the analyzed section exhibit some excursions that could correspond to the hyperthemals in the early Paleogene. Their variable nitrogen isotope compositions reflect temporal changes in the style of biogeochemical cycles involving denitrification and nitrogen fixation. Coupled temporal changes in the carbon isotope compositions of organic and carbonate carbon immediately after the K-Pg boundary might support a Strangelove ocean (Kump, 1991; Geology), however high export production (Ba/Ti, nannoplankton and calcisphere blooms, high planktic foram richness, and diverse and abundant micro- and macrobenthic organisms

  12. Post-endodontic treatment of incisors and premolars among dental practitioners in Saarland: an interactive Web-based survey.

    Science.gov (United States)

    Mitov, Gergo; Dörr, Michael; Nothdurft, Frank P; Draenert, Florian; Pospiech, Peter R

    2015-06-01

    The aim of the present study was to evaluate the trend of dental practitioners in the federal state of Saarland in Germany in regard to restoring endodontically treated teeth using a Web-based survey. An interactive Web-based survey instrument was developed, including seven clinical scenarios, presented by photographs of natural incisor and premolar with different types of cavities. Following a decision tree adapted to the clinical treatment, questions on different aspects of the post-endodontic treatment were asked. All 615 members of the Saarland Dental Association (SDA) were asked to participate in the survey. A total of 33 % completed the survey. The majority of the participants believed in the reinforcement effect of the ferrule design, as well as the post placement. The vast majority of the responding practitioners (92 %) adapted their treatment strategies to a high extent to the destruction degree of the endodontically treated tooth. Fiber-reinforced composite (FRC) posts are the most popular prefabricated post type, regardless of the cavity size and tooth localization. Significant differences between the dentists according to the degree of experience were detected only for the use of glass-ionomer cements as core buildup material. The predominant post-endodontic treatment strategies of German dental practitioners are only partly in agreement with the current literature. There is a clear trend toward the increasing use of metal-free post and core materials. Although the participants showed a general adoption of modern materials and techniques, different patterns of post-endodontic treatment were revealed that were not consistent with approaches supported by the literature.

  13. Melt rheological properties of natural fiber-reinforced polypropylene

    Science.gov (United States)

    Jarrod J. Schemenauer; Tim A. Osswald; Anand R. Sanadi; Daniel F. Caulfield

    2000-01-01

    The melt viscosities and mechanical properties of 3 different natural fiber-polypropylene composites were investigated. Coir (coconut), jute, and kenaf fibers were compounded with polypropylene at 30% by weight content. A capillary rheometer was used to evaluate melt viscosity. The power-law model parameters are reported over a shear rate range between 100 to 1000 s–1...

  14. Improved Sectional Image Analysis Technique for Evaluating Fiber Orientations in Fiber-Reinforced Cement-Based Materials.

    Science.gov (United States)

    Lee, Bang Yeon; Kang, Su-Tae; Yun, Hae-Bum; Kim, Yun Yong

    2016-01-12

    The distribution of fiber orientation is an important factor in determining the mechanical properties of fiber-reinforced concrete. This study proposes a new image analysis technique for improving the evaluation accuracy of fiber orientation distribution in the sectional image of fiber-reinforced concrete. A series of tests on the accuracy of fiber detection and the estimation performance of fiber orientation was performed on artificial fiber images to assess the validity of the proposed technique. The validation test results showed that the proposed technique estimates the distribution of fiber orientation more accurately than the direct measurement of fiber orientation by image analysis.

  15. Selected Bibliography on Fiber-Reinforced Cement and Concrete. Supplement Number 4.

    Science.gov (United States)

    1982-08-01

    Building Industry," L’Industria Italiana del Cemento , Vol 50, No. 12, Dec 1980, pp 1135-1144. 19. Bartos, P., "Pullout Failure of Fibres Embedded in Cement...Vol 43, No. 11, Nov 1977, pp 561-564. 21. Bassan, M., "Model of Behavior of Fiber-Reinforced Concretes Under Impact Stresses," il Cemento , Vol 74, No...Pastes," il Cemento , Vol 75, No. 3, Jul-Sep 1978, pp 277-284. 210. Mills, R. H., "Age-Embrittlement of Glass-Reinforced Concrete Containing Blastfurance

  16. Energy Absorption Mechanisms in Unidirectional Composites Subjected to Dynamic Loading Events

    Science.gov (United States)

    2012-03-30

    integral part of commercial, recreation, and defense markets . The proliferation of applications for fiber-reinforced composite technology can be in large...soft body armors. The growth of composites in high-performance markets continues to outpace the development of new and improved physics-based...pp. 718 – 730, 2008. 16. G. C. Jacob, J. F. Fellers, S. Simunovic, and J. M. Starbuck , “Energy Absorption in Polymer Composites for

  17. Properties and performance of flax yarn/thermoplastic polyester composites

    DEFF Research Database (Denmark)

    Madsen, Bo; Mehmood, Shahid

    2012-01-01

    Aiming at demonstrating the potential of unidirectional natural fiber-reinforced thermoplastic composites in structural applications, textile flax yarn/thermoplastic polyester composites with variable fiber volume fractions have been manufactured by a filament-winding process followed by a vacuum......-assisted compression molding process. The microstructure of the composites shows that the flax fiber yarns are well impregnated by the polyester matrix, and this supports the measured low porosity content of the composites. The experimental tensile modulus and ultimate tensile stress of the composites in the axial...

  18. Mechanics of composite materials - 1983. Proceedings of the Symposium, Boston, MA, November 13-18, 1983

    International Nuclear Information System (INIS)

    Dvorak, G.J.

    1983-01-01

    The present conference discusses plate theories applicable to laminated composites, the analysis of large deformations in layered composite shells, composite plate nonlinear bending effects, hybrid composite constitutive behavior, polymeric material life prediction by means of kinetic fracture mechanics, and crack growth direction in fibrous composites. Also discussed are stress singularities and solution structures, together with the delamination behavior and fracture mechanics parameters, of delamination mechanics in fiber-reinforced composites, followed by the theory and applications of unidirectional composite fracture, impact and fatigue behavior in graphite-epoxy laminates, and the fracture behavior of notched unidirectional boron/aluminum composite laminates

  19. Chemical composition and bioactive compounds of garlic (Allium sativum L.) as affected by pre- and post-harvest conditions: A review.

    Science.gov (United States)

    Martins, Natália; Petropoulos, Spyridon; Ferreira, Isabel C F R

    2016-11-15

    Garlic (Allium sativum L.) is considered one of the twenty most important vegetables, with various uses throughout the world, either as a raw vegetable for culinary purposes, or as an ingredient of traditional and modern medicine. Furthermore, it has also been proposed as one of the richest sources of total phenolic compounds, among the usually consumed vegetables, and has been highly ranked regarding its contribution of phenolic compounds to human diet. This review aims to examine all the aspects related with garlic chemical composition and quality, focusing on its bioactive properties. A particular emphasis is given on the organosulfur compounds content, since they highly contribute to the effective bioactive properties of garlic, including its derived products. The important effects of pre-harvest (genotype and various cultivation practices) and post-harvest conditions (storage conditions and processing treatments) on chemical composition and, consequently, bioactive potency of garlic are also discussed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Effects of fiber ellipticity and orientation on dynamic stress concentrations in porous fiber-reinforced composites

    Science.gov (United States)

    Hasheminejad, Seyyed M.; Sanaei, Roozbeh

    2007-11-01

    Interaction of time harmonic fast longitudinal and shear incident plane waves with an elliptical fiber embedded in a porous elastic matrix is studied. The novel features of Biot dynamic theory of poroelasticity along with the classical method of eigen-function expansion and the pertinent boundary conditions are employed to develop a closed form series solution involving Mathieu and modified Mathieu functions of complex arguments. The complications arising due to the non-orthogonality of angular Mathieu functions corresponding to distinct wave numbers in addition to the problems associated with appearance of additional angular dependent terms in the boundary conditions are all avoided by expansion of the angular Mathieu functions in terms of transcendental functions and subsequent integration, leading to a linear set of independent equations in terms of the unknown scattering coefficients. A MATHEMATICA code is developed for computing the Mathieu functions in terms of complex Fourier coefficients which are themselves calculated by numerically solving appropriate sets of eigen-systems. The analytical results are illustrated with numerical examples in which an elastic fiber of elliptic cross section is insonified by a plane fast compressional or shear wave at normal incidence. The effects of fiber cross sectional ellipticity, angle of incidence (fiber two-dimensional orientation), and incident wave polarization (P, SV, SH) on dynamic stress concentrations are studied in a relatively wide frequency range. Limiting cases are considered and fair agreements with well-known solutions are established.

  1. Optimization for Tribological Properties of Glass Fiber-Reinforced PTFE Composites with Grey Relational Analysis

    Directory of Open Access Journals (Sweden)

    Firojkhan Pathan

    2016-01-01

    Full Text Available Most recent history shows that polytetrafluoroethylene (PTFE is widely used as antifrictional materials in industry for wide speed range. A high antifriction property of PTFE makes it suitable for dry friction bearing. Main disadvantage of using PTFE is its high wear rate, so extensive research had been carried out to improve the wear resistance with addition of filler material. This study focuses on four input parameters load, sliding speed, sliding distance, and percentage of glass fiber as a filler material. Taguchi method was used for experimentation; each parameter is having 3 levels with L27 orthogonal array. Grey relational analysis is used to convert multiple response parameters, namely, wear and coefficient of friction, into single grey relation grade. The optimal input parameters were selected based on the S/N ratio. It was observed that load 3 kg, sliding speed 5.1836 m/s (900 rpm, sliding distance 2 km, and 15% of glass fiber are optimal input parameters for PTFE without significantly affecting the wear rate and coefficient of friction.

  2. Alumina Fiber-Reinforced 9310 Steel Metal Matrix Composite for Rotorcraft Drive System Components, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — AISI 9310 nickel-chromium-molybdenum alloy steel is used extensively in military helicopter rotor shafts and gears. This reliable alloy provides excellent fatigue...

  3. CVD apparatus and process for the preparation of fiber-reinforced ceramic composites

    Science.gov (United States)

    Caputo, A.J.; Devore, C.E.; Lowden, R.A.; Moeller, H.H.

    1990-01-23

    An apparatus and process for the chemical vapor deposition of a matrix into a preform having circumferentially wound ceramic fibers, comprises heating one surface of the preform while cooling the other surface thereof. The resulting product may have fibers that are wound on radial planes or at an angle from the radial planes. The fibers can also be precoated with pyrolytic carbon before application of the matrix. The matrix is applied by passing reactant gas through the preform thereof to the other side thereof for the initial deposition of matrix near such other surface of the preform. The matrix fills in the preform from the other side surface thereof to the surface of the side of application thereof until a desired amount of matrix has been deposited. 6 figs.

  4. Strain redistribution around holes and notches in fiber-reinforced cross-woven brittle matrix composites

    DEFF Research Database (Denmark)

    Jacobsen, Torben Krogsdal; Brøndsted, Povl

    1997-01-01

    Mechanics, and an identification procedure based on a uni-axial tensile test and a shear test the strain redistribution around a hole or a notch due to matrix cracking can be predicted. Damage due to fiber breakage is not included in the model. Initial matrix damage in the C-f/SiCm material has...

  5. Preparation, mechanical, and in vitro properties of glass fiber-reinforced polycarbonate composites for orthodontic application.

    Science.gov (United States)

    Tanimoto, Yasuhiro; Inami, Toshihiro; Yamaguchi, Masaru; Nishiyama, Norihiro; Kasai, Kazutaka

    2015-05-01

    Generally, orthodontic treatment uses metallic wires made from stainless steel, cobalt-chromium-nickel alloy, β-titanium alloy, and nickel-titanium (Ni-Ti) alloy. However, these wires are not esthetically pleasing and may induce allergic or toxic reactions. To correct these issues, in the present study we developed glass-fiber-reinforced plastic (GFRP) orthodontic wires made from polycarbonate and E-glass fiber by using pultrusion. After fabricating these GFRP round wires with a diameter of 0.45 mm (0.018 inch), we examined their mechanical and in vitro properties. To investigate how the glass-fiber diameter affected their physical properties, we prepared GFRP wires of varying diameters (7 and 13 µm). Both the GFRP with 13-µm fibers (GFRP-13) and GFRP with 7 µm fibers (GFRP-7) were more transparent than the metallic orthodontic wires. Flexural strengths of GFRP-13 and GFRP-7 were 690.3 ± 99.2 and 938.1 ± 95.0 MPa, respectively; flexural moduli of GFRP-13 and GFRP-7 were 25.4 ± 4.9 and 34.7 ± 7.7 GPa, respectively. These flexural properties of the GFRP wires were nearly equivalent to those of available Ni-Ti wires. GFRP-7 had better flexural properties than GFRP-13, indicating that the flexural properties of GFRP increase with decreasing fiber diameter. Using thermocycling, we found no significant change in the flexural properties of the GFRPs after 600 or 1,200 cycles. Using a cytotoxicity detection kit, we found that the glass fiber and polycarbonate components comprising the GFRP were not cytotoxic within the limitations of this study. We expect this metal-free GFRP wire composed of polycarbonate and glass fiber to be useful as an esthetically pleasing alternative to current metallic orthodontic wire. © 2014 Wiley Periodicals, Inc.

  6. Recent developments in chemical modification and characterization of natural fiber-reinforced composites

    CSIR Research Space (South Africa)

    Jacob John, Maya

    2008-01-01

    Full Text Available health outcome of concern was respiratory health. Other acute and chronic health effects such as heart disease, arthritis, and tuberculosis were also evaluated but not reported in detail here. While measurements of air pollution in the community... was administered by trained, local field workers to 377 eMbalenhle households. A pilot study to test questionnaire validity was performed at a similar low-income community, i.e. Cato Crest in Durban. The questionnaire was intended to capture data about...

  7. Effect of post-fermentation and packing stages on the volatile composition of Spanish-style green table olives.

    Science.gov (United States)

    Sánchez, Antonio Higinio; López-López, Antonio; Cortés-Delgado, Amparo; Beato, Víctor Manuel; Medina, Eduardo; de Castro, Antonio; Montaño, Alfredo

    2018-01-15

    The volatile profile of Spanish-style green table olives after fermentation and the changes in volatile compounds that occurred as a result of the post-fermentation and subsequent packing stage were explored by solid phase micro-extraction (SPME) and gas chromatography coupled to mass spectrometry (GC-MS). Three olive cultivars (Manzanilla, Gordal, and Hojiblanca) were processed and olive samples were taken at three different times throughout the elaboration: after fermentation, after post-fermentation, and after packing. A total of 132 volatile compounds were identified, including 10 phenols, 25 alcohols, 11 acids, 39 esters, 8 hydrocarbons, 14 carbonyl compounds, 17 terpenes, and 6 other compounds. A varying number of compounds from each chemical family underwent significant changes because of the post-fermentation and packing stages. Among them, some typical reaction products of lipid oxidation (e.g. (E)-2-decenal and (E,E)-2,4-decadienal) increased with the post-fermentation in Manzanilla cultivar, and also as a result of packing in all three cultivars. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. "Choice" and destiny: the substrate composition and mechanical stability of settlement structures can mediate coral recruit fate in post-bleached reefs

    Science.gov (United States)

    Yadav, Shreya; Rathod, Pooja; Alcoverro, Teresa; Arthur, Rohan

    2016-03-01

    Increasingly frequent and intense ocean warming events seriously test the buffer and recovery capacities of tropical coral reefs. Post-disturbance, available settlement structures on a reef (often dead coral skeletons) vary considerably in their mechanical stability and substrate composition, critically influencing coral recruit settlement choice and fate. In the wake of a coral mass mortality in the Lakshadweep archipelago, we examine (1) the relative availability of recruit settlement structures (from stable to unstable: reef platform, dead massive coral, consolidated rubble, dead corymbose coral, dead tabular coral, and unconsolidated rubble) in 12 recovering reefs across three atolls in the archipelago, (2) the substrate composition [crustose coralline algae (CCA), mixed turf, macroalgae] of these structural forms, and (3) whether the choice and fate of young coral are mediated by the substrate and stability of different structural forms. For this, we measured the abundance and distribution of recruit (<1 cm), juvenile (1-5 cm), and young adult (5-10) corals of 24 common coral genera. Four years after the mass mortality, reefs differed considerably in composition of settlement structures. The structures themselves varied significantly in substrate cover with dead tables largely covered in CCA [60 ± 6.05 % (SE)] and dead corymbose coral dominated by mixed turf (61.83 ± 3.8 %). The youngest visible recruits (<1 cm) clearly preferred CCA-rich structures such as dead massives and tables. However, older size classes were rarely found on unstable structures (strongly "avoiding" tables, Ivlev's electivity index, E = -0.5). Our results indicate that while substrate cover might mediate coral choice, the mechanical stability of settlement structures is critical in determining post-settlement coral survival. The composition and availability of settlement structures on a reef may serve as a characteristic signature of its recovery potential, aiding in assessments of reef

  9. 5 year radar-based rainfall statistics: disturbances analysis and development of a post-correction scheme for the German radar composite

    Science.gov (United States)

    Wagner, A.; Seltmann, J.; Kunstmann, H.

    2015-02-01

    A radar-based rainfall statistic demands high quality data that provide realistic precipitation amounts in space and time. Instead of correcting single radar images, we developed a post-correction scheme for long-term composite radar data that corrects corrupted areas, but preserves the original precipitation patterns. The post-correction scheme is based on a 5 year statistical analysis of radar composite data and its constituents. The accumulation of radar images reveals artificial effects that are not visible in the individual radar images. Some of them are already inherent to single radar data such as the effect of increasing beam height, beam blockage or clutter remnants. More artificial effects are introduced in the process of compositing such as sharp gradients at the boundaries of overlapping areas due to different beam heights and resolution. The cause of these disturbances, their behaviour with respect to reflectivity level, season or altitude is analysed based on time-series of two radar products: the single radar reflectivity product PX for each of the 16 radar systems of the German Meteorological Service (DWD) for the time span 2000 to 2006 and the radar composite product RX of DWD from 2005 through to 2009. These statistics result in additional quality information on radar data that is not available elsewhere. The resulting robust characteristics of disturbances, e.g. the dependency of the frequencies of occurrence of radar reflectivities on beam height, are then used as a basis for the post-correction algorithm. The scheme comprises corrections for shading effects and speckles, such as clutter remnants or overfiltering, as well as for systematic differences in frequencies of occurrence of radar reflectivities between the near and the far ranges of individual radar sites. An adjustment to rain gauges is also included. Applying this correction, the Root-Mean-Square-Error for the comparison of radar derived annual rain amounts with rain gauge data

  10. Magnetoresistance properties of Fe0,2C0,8 composite materials pre and post gamma irradiated at 250 kGy dose

    International Nuclear Information System (INIS)

    Yunasfi; Setyo Purwanto; Wisnu A A

    2009-01-01

    Research about change of, magnetoresistance properties of Fe 0,2 C 0,8 composite materials pre and post gamma irradiation at a dose of 250 kGy was carried out. Fe 0,2 C 0,8 was prepared by mixing of Fe and C powder with the ratio of Fe : C set on 20:80 in weight %. In this research, the phase structure and magnetic properties of Fe 0,2 C 0,8 composite materials after 250 KGy dose of gamma irradiation have been measured and analyzed. The phase structure of Fe 0,2 C 0,8 was analyzed using X-ray diffractometer (XRD), whole the magnetoresistance properties was characterized using Four Point Probe method. The analyzing results showed the decreasing of X-ray diffraction peak intensity, but also in the same time showed the increasing of magnetoresistance properties after gamma irradiation. The enhancement of magnetoresistance value reached 5 times at 7,5 kOe magnetic field. This enhancement was caused due to structure defect within Fe 0,2 C 0,8 composite initiated by interaction between radiation of gamma ray and composite materials that further causes a change of magnetic interaction intensity in this materials. (author)

  11. Data on post irradiation experiments of heat resistant ceramic composite materials. PIE for 97M-13A

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Shin-ichi; Ishihara, Masahiro; Souzawa, Shizuo [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Sekino, Hajime [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2003-03-01

    The research on the radiation damage mechanism of heat resistant ceramic composite materials is one of the research subjects of the innovative basic research in the field of high temperature engineering, using the High Temperature engineering Test Reactor (HTTR). Three series of irradiation tests on the heat resistant ceramic composite materials, first to third irradiation test program, were carried out using the Japan Material Testing Reactor (JMTR). This is a summary report on the first irradiation test program; irradiation induced dimensional change, thermal expansion coefficient, X-ray diffraction and {gamma}-ray spectrum are reported. (author)

  12. Influence of post discharge nutrition on body composition at 6 years of age among children born very preterm

    DEFF Research Database (Denmark)

    Toftlund, Line Hedegaard; Zachariassen, Gitte; Agertoft, Lone

    Background Very preterm born infants receive nutrition that ensures optimal growth during the neonatal period. New research has shown that the type of nutrition in early life may affect not only growth but also later body composition and risk of developing metabolic syndrome. Aim • To evaluate...... if type of nutrition in early life effects the body composition in later life among very preterm born children Method In 2004-08 a birth cohort of very preterm born infants with a gestational age ≤32+0 weeks. At time of hospital discharge, the infants were randomised into 3 different feeding groups...

  13. Grout compactness monitoring of concrete-filled fiber-reinforced polymer tube using electromechanical impedance

    Science.gov (United States)

    Shi, Yaokun; Luo, Mingzhang; Li, Weijie; Song, Gangbing

    2018-05-01

    The concrete-filled fiber-reinforced polymer tube (CFFT) is a type of structural element widely used in corrosive environments. Poor grout compactness results in incomplete contact or even no contact between the fiber-reinforced polymer (FRP) tube and the concrete grout, which reduces the load bearing capacity of a CFFT. The monitoring of grout compactness for CFFTs is important. The piezoceramic-based electromechanical impedance (EMI) method has emerged as an efficient and low-cost structural health monitoring technique. This paper presents a feasibility study using the EMI method to monitor grout compactness of CFFTs. In this research, CFFT specimens with different levels of compactness (empty, 1/5, 1/3, 1/2, 2/3, and full compactness) were prepared and subjected to EMI measurement by using four piezoceramic patches that were bonded circumferentially along the outer surface of the CFFT. To analyze the correlation between grout compactness and EMI signatures, a compactness index (CI) was proposed based on the root-mean-square deviation (RMSD). The experimental results show that the changes in admittance signatures are able to determine the grout compactness qualitatively. The proposed CI is able to effectively identify the compactness of the CFFT, and provides location information of the incomplete concrete infill.

  14. Compressive Behavior of Fiber-Reinforced Concrete with End-Hooked Steel Fibers

    Directory of Open Access Journals (Sweden)

    Seong-Cheol Lee

    2015-03-01

    Full Text Available In this paper, the compressive behavior of fiber-reinforced concrete with end-hooked steel fibers has been investigated through a uniaxial compression test in which the variables were concrete compressive strength, fiber volumetric ratio, and fiber aspect ratio (length to diameter. In order to minimize the effect of specimen size on fiber distribution, 48 cylinder specimens 150 mm in diameter and 300 mm in height were prepared and then subjected to uniaxial compression. From the test results, it was shown that steel fiber-reinforced concrete (SFRC specimens exhibited ductile behavior after reaching their compressive strength. It was also shown that the strain at the compressive strength generally increased along with an increase in the fiber volumetric ratio and fiber aspect ratio, while the elastic modulus decreased. With consideration for the effect of steel fibers, a model for the stress–strain relationship of SFRC under compression is proposed here. Simple formulae to predict the strain at the compressive strength and the elastic modulus of SFRC were developed as well. The proposed model and formulae will be useful for realistic predictions of the structural behavior of SFRC members or structures.

  15. Enhancement of osteogenesis on micro/nano-topographical carbon fiber-reinforced polyetheretherketone–nanohydroxyapatite biocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Anxiu [College of Stomatology, Chongqing Medical University, Chongqing 401147 (China); Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing 401147 (China); Liu, Xiaochen [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Gao, Xiang; Deng, Feng [College of Stomatology, Chongqing Medical University, Chongqing 401147 (China); Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing 401147 (China); Deng, Yi, E-mail: 18210357357@163.com [College of Stomatology, Chongqing Medical University, Chongqing 401147 (China); Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing 401147 (China); Wei, Shicheng, E-mail: weishicheng99@163.com [College of Stomatology, Chongqing Medical University, Chongqing 401147 (China); Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing 401147 (China)

    2015-03-01

    As an FDA-approved implantable material, carbon fiber-reinforced polyetheretherketone (CFRPEEK) possesses excellent mechanical properties similar to those of human cortical bone and is a prime candidate to replace conventional metallic implants. The bioinertness and inferior osteogenic properties of CFRPEEK, however, limit its clinical application as orthopedic/dental implants. The present work aimed at developing a novel carbon fiber-reinforced polyetheretherketone–nanohydroxyapatite (PEEK/CF/n-HA) ternary biocomposite with micro/nano-topographical surface for the enhancement of the osteogenesis as a potential bioactive material for bone grafting and bone tissue-engineering applications. The combined modification of oxygen plasma and sand-blasting could improve the hydrophily and generate micro/nano-topographical structures on the surface of the CFRPEEK-based ternary biocomposite. The results clearly showcased that the micro-/nano-topographical PEEK/n-HA/CF ternary biocomposite demonstrated the outstanding ability to promote the proliferation and differentiation of MG-63 cells in vitro as well as to boost the osseointegration between implant and bone in vivo, thereby boding well application to bone tissue engineering. - Highlights: • A novel micro/nano-topographical PEEK/n-HA/CF ternary biocomposite was developed. • The modified PEEK biocomposite promotes proliferation and differentiation of cells. • In vivo osseointegration of the micro/nano-topographical PEEK/n-HA/CF was enhanced.

  16. Compressive Behavior of Fiber-Reinforced Concrete with End-Hooked Steel Fibers.

    Science.gov (United States)

    Lee, Seong-Cheol; Oh, Joung-Hwan; Cho, Jae-Yeol

    2015-03-27

    In this paper, the compressive behavior of fiber-reinforced concrete with end-hooked steel fibers has been investigated through a uniaxial compression test in which the variables were concrete compressive strength, fiber volumetric ratio, and fiber aspect ratio (length to diameter). In order to minimize the effect of specimen size on fiber distribution, 48 cylinder specimens 150 mm in diameter and 300 mm in height were prepared and then subjected to uniaxial compression. From the test results, it was shown that steel fiber-reinforced concrete (SFRC) specimens exhibited ductile behavior after reaching their compressive strength. It was also shown that the strain at the compressive strength generally increased along with an increase in the fiber volumetric ratio and fiber aspect ratio, while the elastic modulus decreased. With consideration for the effect of steel fibers, a model for the stress-strain relationship of SFRC under compression is proposed here. Simple formulae to predict the strain at the compressive strength and the elastic modulus of SFRC were developed as well. The proposed model and formulae will be useful for realistic predictions of the structural behavior of SFRC members or structures.

  17. Compressive behaviour of hybrid fiber-reinforced reactive powder concrete after high temperature

    International Nuclear Information System (INIS)

    Zheng, Wenzhong; Li, Haiyan; Wang, Ying

    2012-01-01

    Highlights: ► We complete the high temperature test and compression test of RPC after 20–900 °C. ► The presence of steel fiber and polypropylene fiber can prevent RPC from spalling. ► Compressive strength increases first and then decreases with elevated temperatures. ► Microstructure deterioration is the root cause of macro-properties recession. ► Equations to express the compressive strength change with temperature are proposed. -- Abstract: This study focuses on the compressive properties and microstructures of reactive powder concrete (RPC) mixed with steel fiber and polypropylene fiber after exposure to 20–900 °C. The volume dosage of steel fiber and polypropylene fiber is (2%, 0.1%), (2%, 0.2%) and (1%, 0.2%). The effects of heating temperature, fiber content and specimen size on the compressive properties are analyzed. The microstructures of RPC exposed to different high temperatures are studied by scanning electron microscope (SEM). The results indicate that the compressive strength of hybrid fiber-reinforced RPC increases at first, then decreases with the increasing temperature, and the basic reason for the degradation of macro-mechanical properties is the deterioration of RPC microstructure. Based on the experimental results, equations to express the relationships of the compressive strength with the heating temperatures are established. Compared with normal-strength and high-strength concrete, the hybrid fiber-reinforced RPC has excellent capacity in resistance to high temperature.

  18. Enhancement of osteogenesis on micro/nano-topographical carbon fiber-reinforced polyetheretherketone–nanohydroxyapatite biocomposite

    International Nuclear Information System (INIS)

    Xu, Anxiu; Liu, Xiaochen; Gao, Xiang; Deng, Feng; Deng, Yi; Wei, Shicheng

    2015-01-01

    As an FDA-approved implantable material, carbon fiber-reinforced polyetheretherketone (CFRPEEK) possesses excellent mechanical properties similar to those of human cortical bone and is a prime candidate to replace conventional metallic implants. The bioinertness and inferior osteogenic properties of CFRPEEK, however, limit its clinical application as orthopedic/dental implants. The present work aimed at developing a novel carbon fiber-reinforced polyetheretherketone–nanohydroxyapatite (PEEK/CF/n-HA) ternary biocomposite with micro/nano-topographical surface for the enhancement of the osteogenesis as a potential bioactive material for bone grafting and bone tissue-engineering applications. The combined modification of oxygen plasma and sand-blasting could improve the hydrophily and generate micro/nano-topographical structures on the surface of the CFRPEEK-based ternary biocomposite. The results clearly showcased that the micro-/nano-topographical PEEK/n-HA/CF ternary biocomposite demonstrated the outstanding ability to promote the proliferation and differentiation of MG-63 cells in vitro as well as to boost the osseointegration between implant and bone in vivo, thereby boding well application to bone tissue engineering. - Highlights: • A novel micro/nano-topographical PEEK/n-HA/CF ternary biocomposite was developed. • The modified PEEK biocomposite promotes proliferation and differentiation of cells. • In vivo osseointegration of the micro/nano-topographical PEEK/n-HA/CF was enhanced

  19. A lattice-particle approach for the simulation of fracture processes in fiber-reinforced high-performance concrete

    NARCIS (Netherlands)

    Montero-Chacón, F.; Schlangen, H.E.J.G.; Medina, F.

    2013-01-01

    The use of fiber-reinforced high-performance concrete (FRHPC) is becoming more extended; therefore it is necessary to develop tools to simulate and better understand its behavior. In this work, a discrete model for the analysis of fracture mechanics in FRHPC is presented. The plain concrete matrix,

  20. Detecting post-fire burn severity and vegetation recovery using multitemporal remote sensing spectral indices and field-collected composite burn index data in a ponderosa pine forest

    Science.gov (United States)

    Chen, Xuexia; Vogelmann, James E.; Rollins, Matt; Ohlen, Donald; Key, Carl H.; Yang, Limin; Huang, Chengquan; Shi, Hua

    2011-01-01

    It is challenging to detect burn severity and vegetation recovery because of the relatively long time period required to capture the ecosystem characteristics. Multitemporal remote sensing data can providemultitemporal observations before, during and after a wildfire, and can improve the change detection accuracy. The goal of this study is to examine the correlations between multitemporal spectral indices and field-observed burn severity, and to provide a practical method to estimate burn severity and vegetation recovery. The study site is the Jasper Fire area in the Black Hills National Forest, South Dakota, that burned during August and September 2000. Six multitemporal Landsat images acquired from 2000 (pre-fire), 2001 (post-fire), 2002, 2003, 2005 and 2007 were used to assess burn severity. The normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), normalized burn ratio (NBR), integrated forest index (IFI) and the differences of these indices between the pre-fire and post-fire years were computed and analysed with 66 field-based composite burn index (CBI) plots collected in 2002. Results showed that differences of NDVI and differences of EVI between the pre-fire year and the first two years post-fire were highly correlated with the CBI scores. The correlations were low beyond the second year post-fire. Differences of NBR had good correlation with CBI scores in all study years. Differences of IFI had low correlation with CBI in the first year post-fire and had good correlation in later years. A CBI map of the burnt area was produced using regression tree models and the multitemporal images. The dynamics of four spectral indices from 2000 to 2007 indicated that both NBR and IFI are valuable for monitoring long-term vegetation recovery. The high burn severity areas had a much slower recovery than the moderate and low burn areas.

  1. Humus accumulation, humification, and humic acid composition in soils of two post-mining chronosequences after coal mining

    Czech Academy of Sciences Publication Activity Database

    Abakumov, E.V.; Cajthaml, Tomáš; Brus, Jiří; Frouz, J.

    2013-01-01

    Roč. 13, č. 3 (2013), s. 491-500 ISSN 1439-0108 R&D Projects: GA MŠk 2B08023; GA MŠk LC06066 Institutional support: RVO:61388971 ; RVO:61389013 Keywords : Humus accumulation * Humic acids composition * Humification Subject RIV: EE - Microbiology, Virology; CD - Macromolecular Chemistry (UMCH-V) Impact factor: 2.107, year: 2013

  2. Pre- and post-season dietary intake, body composition, and performance indices of NCAA division I female soccer players.

    Science.gov (United States)

    Clark, Mandy; Reed, Debra B; Crouse, Stephen F; Armstrong, Robert B

    2003-09-01

    Little published data describe the dietary and physiological profiles of intercollegiate female soccer players; therefore, the purpose of this investigation was to report baseline dietary data, anthropometrics, and performance indices of soccer women during rigorous pre-season training (2 sessions/day) and then during the post-competitive season. Members of a NCAA Division I women's soccer squad completed 3-day diet records, anthropometrics, and physical tests, including VO2peak. Average body mass was 62 kg with 16% body fat, and no significant pre to post differences were observed. Total energy, carbohydrate (CHO), protein, and fat intakes were significantly greater during the pre-season. Pre-season energy intake met the DRI for females with an "active" lifestyle (37 kcal/kg). While CHO intake failed to meet minimum recommendations to promote glycogen repletion (7-10 g/kg), protein and fat intakes were above minimum recommendations. Pre- and post-season intakes of several micronutrients were marginal (failed to meet minimum CHO and micronutrient recommendations. Foods higher in protein and fat displaced more CHO-rich and nutrient-dense foods within athletes' energy requirements and satiety limits.

  3. Mechanical property evaluation of natural fiber coir composite

    International Nuclear Information System (INIS)

    Harish, S.; Michael, D. Peter; Bensely, A.; Lal, D. Mohan; Rajadurai, A.

    2009-01-01

    The fiber which serves as a reinforcement in reinforced plastics may be synthetic or natural. Past studies show that only artificial fibers such as glass, carbon etc., have been used in fiber-reinforced plastics. Although glass and other synthetic fiber-reinforced plastics possess high specific strength, their fields of application are very limited because of their inherent higher cost of production. In this connection, an investigation has been carried out to make use of coir, a natural fiber abundantly available in India. Natural fibers are not only strong and lightweight but also relatively very cheap. In the present work, coir composites are developed and their mechanical properties are evaluated. Scanning electron micrographs obtained from fractured surfaces were used for a qualitative evaluation of the interfacial properties of coir/epoxy and compared with glass fiber/epoxy. These results indicate that coir can be used as a potential reinforcing material for making low load bearing thermoplastic composites

  4. Effect of the size of the apical enlargement with rotary instruments, single-cone filling, post space preparation with drills, fiber post removal, and root canal filling removal on apical crack initiation and propagation.

    Science.gov (United States)

    Çapar, İsmail Davut; Uysal, Banu; Ok, Evren; Arslan, Hakan

    2015-02-01

    The purpose of this study was to investigate the incidence of apical crack initiation and propagation in root dentin after several endodontic procedures. Sixty intact mandibular premolars were sectioned perpendicular to the long axis at 1 mm from the apex, and the apical surface was polished. Thirty teeth were left unprepared and served as a control, and the remaining 30 teeth were instrumented with ProTaper Universal instruments (Dentsply Maillefer, Ballaigues, Switzerland) up to size F5. The root canals were filled with the single-cone technique. Gutta-percha was removed with drills of the Rebilda post system (VOCO, Cuxhaven, Germany). Glass fiber-reinforced composite fiber posts were cemented using a dual-cure resin cement. The fiber posts were removed with a drill of the post system. Retreatment was completed after the removal of the gutta-percha. Crack initiation and propagation in the apical surfaces of the samples were examined with a stereomicroscope after each procedure. The absence/presence of cracks was recorded. Logistic regression was performed to analyze statistically the incidence of crack initiation and propagation with each procedure. The initiation of the first crack and crack propagation was associated with F2 and F4 instruments, respectively. The logistic regression analysis revealed that instrumentation and F2 instrument significantly affected apical crack initiation (P .05). Rotary nickel-titanium instrumentation had a significant effect on apical crack initiation, and post space preparation with drills had a significant impact on crack propagation. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  5. Post-processor for simulations of the ORIGEN program and calculation of the composition of the activity of a burnt fuel core by a BWR type reactor

    International Nuclear Information System (INIS)

    Sandoval V, S.

    2006-01-01

    The composition calculation and the activity of nuclear materials subject to processes of burnt, irradiation and decay periods are of utility for diverse activities inside the nuclear industry, as they are it: the processes design and operations that manage radioactive material, the calculation of the inventory and activity of a core of burnt nuclear fuel, for studies of type Probabilistic Safety Analysis (APS), as well as for regulation processes and licensing of nuclear facilities. ORIGEN is a program for computer that calculates the composition and the activity of nuclear materials subject to periods of burnt, irradiation and decay. ORIGEN generates a great quantity of information whose processing and analysis are laborious, and it requires thoroughness to avoid errors. The automation of the extraction, conditioning and classification of that information is of great utility for the analyst. By means of the use of the post-processor presented in this work it is facilitated, it speeds up and wide the capacity of analysis of results, since diverse consultations with several classification options and filtrate of results can be made. As illustration of the utility of the post-processor, and as an analysis of interest for itself, it is also presented in this work the composition of the activity of a burned core in a BWR type reactor according to the following classification criteria: by type of radioisotope (fission products, activation products and actinides), by specie type (gassy, volatile, semi-volatile and not volatile), by element and by chemical group. The results show that the total activity of the studied core is dominated by the fission products and for the actinides, in proportion four to one, and that the gassy and volatile species conform a fifth part of the total activity of the core. (Author)

  6. External nitrogen input affects pre- and post-harvest cell wall composition but not the enzymatic saccharification of wheat straw

    DEFF Research Database (Denmark)

    Baldwin, Laetitia Andrée; Glazowska, Sylwia Emilia; Mravec, Jozef

    2017-01-01

    Wheat is one of the most important crops for food and feed and its straw is a potential feedstock for biorefinery purposes. Nitrogen (N) is an essential input factor in wheat agriculture but no information is available on how it affects straw composition during maturation and at harvest....... To investigate this, we conducted a large scale field experiment in which wheat plants were cultivated at three levels of externally applied N. The plants were harvested at different stages of maturation, spanning green straw at heading (ear emergence) to fully yellow straw at final maturity. Defined parts...

  7. Delayed post-harvest ripening-associated changes in Manilkara zapota L. var. Kalipatti with composite edible coating.

    Science.gov (United States)

    Vishwasrao, Chandrahas; Ananthanarayan, Laxmi

    2017-01-01

    There has been limited research on extending the shelf-life of sapota (Manilkara zapota L. var. Kalipatti) fruit. An edible coating made up of methyl cellulose (MC) and palm oil (PO) was applied to study the extension in shelf-life. Changes in physical and chemical properties of fruit were studied along with peroxidase (POD), polyphenol oxidase (PPO) and pectin methylesterase (PME) activities during post-harvest ripening of sapota. The fruits coated with 15 g L -1 MC and 11.25 g L -1 PO showed significant (P edible coating made up of MC-PO has potential to maintain the quality of sapota fruit. The edible coating extended the shelf-life of sapota fruit by 3 days preserving fruit quality up to 7 days at 24 ± 1 °C and 65 ± 5 %RH. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  8. Polymer-based composites for aerospace: An overview of IMAST results

    Science.gov (United States)

    Milella, Eva; Cammarano, Aniello

    2016-05-01

    This paper gives an overview of technological results, achieved by IMAST, the Technological Cluster on Engineering of Polymeric Composite Materials and Structures, in the completed Research Projects in the aerospace field. In this sector, the Cluster developed different solutions: lightweight multifunctional fiber-reinforced polymer composites for aeronautic structures, advanced manufacturing processes (for the optimization of energy consumption and waste reduction) and multifunctional components (e.g., thermal, electrical, acoustic and fire resistance).

  9. Vibration Analysis of Cracked Composite Bending-torsion Beams for Damage Diagnosis

    OpenAIRE

    Wang, Kaihong

    2004-01-01

    An analytical model of cracked composite beams vibrating in coupled bending-torsion is developed. The beam is made of fiber-reinforced composite with fiber angles in each ply aligned in the same direction. The crack is assumed open. The local flexibility concept is implemented to model the open crack and the associated compliance matrix is derived. The crack introduces additional boundary conditions at the crack location and these effects in conjunction with those of material properties are i...

  10. Flexural Behavior of High-Volume Steel Fiber Cementitious Composite Externally Reinforced with Basalt FRP Sheet

    OpenAIRE

    Seungwon Kim; Cheolwoo Park

    2016-01-01

    High-performance fiber-reinforced cementitious composites (HPFRCCs) are characterized by unique tensile strain hardening and multiple microcracking behaviors. The HPFRCC, which demonstrates remarkable properties such as strength, ductility, toughness, durability, stiffness, and thermal resistance, is a class of fiber cement composite with fine aggregates. It can withstand tensile stresses by forming distributed microcracks owing to the embedded fibers in the concrete, which improve the energy...

  11. Fiber-reinforced materials: finite elements for the treatment of the inextensibility constraint

    Science.gov (United States)

    Auricchio, Ferdinando; Scalet, Giulia; Wriggers, Peter

    2017-12-01

    The present paper proposes a numerical framework for the analysis of problems involving fiber-reinforced anisotropic materials. Specifically, isotropic linear elastic solids, reinforced by a single family of inextensible fibers, are considered. The kinematic constraint equation of inextensibility in the fiber direction leads to the presence of an undetermined fiber stress in the constitutive equations. To avoid locking-phenomena in the numerical solution due to the presence of the constraint, mixed finite elements based on the Lagrange multiplier, perturbed Lagrangian, and penalty method are proposed. Several boundary-value problems under plane strain conditions are solved and numerical results are compared to analytical solutions, whenever the derivation is possible. The performed simulations allow to assess the performance of the proposed finite elements and to discuss several features of the developed formulations concerning the effective approximation for the displacement and fiber stress fields, mesh convergence, and sensitivity to penalty parameters.

  12. Simulation of crack propagation in fiber-reinforced concrete by fracture mechanics

    International Nuclear Information System (INIS)

    Zhang Jun; Li, Victor C.

    2004-01-01

    Mode I crack propagation in fiber-reinforced concrete (FRC) is simulated by a fracture mechanics approach. A superposition method is applied to calculate the crack tip stress intensity factor. The model relies on the fracture toughness of hardened cement paste (K IC ) and the crack bridging law, so-called stress-crack width (σ-δ) relationship of the material, as the fundamental material parameters for model input. As two examples, experimental data from steel FRC beams under three-point bending load are analyzed with the present fracture mechanics model. A good agreement has been found between model predictions and experimental results in terms of flexural stress-crack mouth opening displacement (CMOD) diagrams. These analyses and comparisons confirm that the structural performance of concrete and FRC elements, such as beams in bending, can be predicted by the simple fracture mechanics model as long as the related material properties, K IC and (σ-δ) relationship, are known

  13. Utilization of power plant bottom ash as aggregates in fiber-reinforced cellular concrete.

    Science.gov (United States)

    Lee, H K; Kim, H K; Hwang, E A

    2010-02-01

    Recently, millions tons of bottom ash wastes from thermoelectric power plants have been disposed of in landfills and coastal areas, regardless of its recycling possibility in construction fields. Fiber-reinforced cellular concrete (FRCC) of low density and of high strength may be attainable through the addition of bottom ash due to its relatively high strength. This paper focuses on evaluating the feasibility of utilizing bottom ash of thermoelectric power plant wastes as aggregates in FRCC. The flow characteristics of cement mortar with bottom ash aggregates and the effect of aggregate type and size on concrete density and compressive strength were investigated. In addition, the effects of adding steel and polypropylene fibers for improving the strength of concrete were also investigated. The results from this study suggest that bottom ash can be applied as a construction material which may not only improve the compressive strength of FRCC significantly but also reduce problems related to bottom ash waste.

  14. Influence of fiber upon the radiation degradation of fiber-reinforced plastics

    International Nuclear Information System (INIS)

    Udagawa, Akira

    1992-01-01

    Influences of fiber upon the radiation degradation of fiber-reinforced plastics were investigated by using 2 MeV electrons. Radiation resistances were evaluated from the three-point bending strength of the fiber laminates which used bisphenol A-type epoxy resin as a matrix. Carbon fiber laminates had higher radiation resistance values than the laminates made of glass fiber. Model laminates using polyethylene as a matrix were prepared in order to examine the differences between carbon fiber and glass fiber filler, the relation between gel fraction and absorbed dose was established. When the polyethylene was filled in the carbon fiber, forming the gel was strikingly delayed. This result suggests that radiation protective action existing in carbon fiber to matrix resin is the main cause of the higher radiation resistance of carbon fiber reinforced plastics. (author)

  15. The post-Laramide clastic deposits of the Sierra de Guanajuato: Compositional implications on the tectono-sedimentary and paleographic evolution

    Energy Technology Data Exchange (ETDEWEB)

    Miranda-Aviles, R.; Puy-Alquiza, M.J.; OmaNa, L.; Loza-Aguirre, I.

    2016-07-01

    This article presents the results of the study on sedimentation, sedimentary environments, tectono-sedimentary and paleogeographic evolution of post-Laramide clastic deposits and pre-volcanism of the Sierra Madre Occidental in the Sierra de Guanajuato, central Mexico. The Eocene Duarte Conglomerate and Guanajuato Conglomerate were deposited in the middle and distal parts of alluvial fans. The studied rocks are composed of limestone clasts, granite, andesite, metasediments, diorite, and pyroxenite, indicating the erosion of uplifted blocks of the basal complex of the Sierra de Guanajuato (Arperos basin). The petrographic and compositional analysis of limestone shows a textural variation from basin limestones and shallow platform limestones. The shallow platform limestone contain bivalves, brachiopods, gastropods, echinoderms and benthic foraminifera from the Berriasian-Valanginian. The shallow-water limestone corresponds to the boundary of the Arperos basin whose original outcrops currently not outcrop in the Sierra de Guanajuato. (Author)

  16. Optique moderne et post-moderne dans la composition d'images transculturelles dans trois films de Woody Allen

    Directory of Open Access Journals (Sweden)

    Nadia Fuchs

    2010-12-01

    Full Text Available Avec le personnage récurrent juif new-yorkais névrosé plus ou moins autobiographique, les films de Woody Allen ont créé, volontairement ou pas, leur propre mythologie et un genre à part entière composé de codes que le spectateur décrypte instantanément. Pourtant, Woody Allen est surtout un cinéaste post-moderne, analysant et déconstruisant les simulacres de son époque. Il est ainsi un passeur d'images retraçant l'histoire des arts modernes des XXe et XXIe siècles et de leurs stratégies énonciatives et réceptives.With the recurrent persona of the neurotic and more or less autobiographical Jewish New Yorker, Woody Allen's films have created, willingly or not, their own mythology and a specific genre made up of codes readily accessible to the spectator. However, Woody Allen is more than anything else a postmodern filmmaker who analyses and deconstructs the simulacra of his time. He is thus a conveyor of images which retrace the history of modern art of the XXth and XXIth centuries, and of their strategies of enunciation and reception.

  17. Maternal insulin resistance, triglycerides and cord blood insulin in relation to post-natal weight trajectories and body composition in the offspring up to 2 years.

    Science.gov (United States)

    Brunner, S; Schmid, D; Hüttinger, K; Much, D; Heimberg, E; Sedlmeier, E-M; Brüderl, M; Kratzsch, J; Bader, B L; Amann-Gassner, U; Hauner, H

    2013-12-01

    The intrauterine metabolic environment might have a programming effect on offspring body composition. We aimed to explore associations of maternal variables of glucose and lipid metabolism during pregnancy, as well as cord blood insulin, with infant growth and body composition up to 2 years post-partum. Data of pregnant women and their infants came from a randomized controlled trial designed to investigate the impact of nutritional fatty acids on adipose tissue development in the offspring. Of the 208 pregnant women enrolled, 118 infants were examined at 2 years. In the present analysis, maternal fasting plasma insulin, homeostasis model assessment of insulin resistance and serum triglycerides measured during pregnancy, as well as insulin in umbilical cord plasma, were related to infant growth and body composition assessed by skinfold thickness measurements and abdominal ultrasonography up to 2 years of age. Maternal homeostasis model assessment of insulin resistance at the 32nd week of gestation was significantly inversely associated with infant lean body mass at birth, whereas the change in serum triglycerides during pregnancy was positively associated with ponderal index at 4 months, but not at later time points. Cord plasma insulin correlated positively with birthweight and neonatal fat mass and was inversely associated with body weight gain up to 2 years after multiple adjustments. Subsequent stratification by gender revealed that this relationship with weight gain was stronger, and significant only in girls. Cord blood insulin is inversely associated with subsequent infant weight gain up to 2 years and this seems to be more pronounced in girls. © 2013 The Authors. Diabetic Medicine © 2013 Diabetes UK.

  18. CORRELATION OF PHYSICAL ACTIVITY LEVEL WITH BONE MINERAL DENSITY, CARDIO-RESPIRATORY FITNESS AND BODY COMPOSITION IN POST-MENOPAUSAL WOMEN

    Directory of Open Access Journals (Sweden)

    Niyati N Khona

    2017-09-01

    Full Text Available Background: Due to the hormonal changes in postmenopausal women they are prone for many complications like increased CVD risk factors, osteoporosis, obesity, mood swings and urinary incontinence. Physical inactivity in postmenopausal women leads to higher risk of developing CVD and osteoporosis. The objective was to find out the correlation of physical activity level with BMD, cardio-respiratory fitness and body composition in post-menopausal women Methods: 42 postmenopausal women were included. A detailed clinical evaluation with physical activity level (IPAQ-METS-mins/week, , BMD ( T-Scores, body composition (BMI, waist circumference, BIA & Skin fold calliper for fat %, cardio-respiratory fitness was measured by Balke protocol and VO2peak (ml/kg/min is estimated. Correlation of physical activity level with BMD, cardio-respiratory fitness and body composition were analysed using “Pearson’s product moment correlation co-efficient and Spearman’s rho.” Results: Spearman’s rank correlation rho for IPAQ with VO2 peak was 0.420,BMI was -0.388 and visceral fat was -0.384 indicating moderate positive correlation between IPAQ and cardio-respiratory fitness and weak negative correlation between IPAQ and BMI and visceral fat. Pearson’s product moment correlation coefficient of IPAQ with BMD was 0.147, body fat was -0.234 and waist circumference was -0.256 indicating no correlation. P value was significant for correlation of IPAQ with CRF (0.006, BMI (0.011 and Visceral fat (0.012. Conclusion: There is moderate positive correlation between IPAQ and cardio-respiratory fitness, weak negative correlation between IPAQ and BMI and visceral fat and no correlation between IPAQ and BMD, body fat and waist circumference

  19. The Effects of Pre- and Post-Exercise Whey vs. Casein Protein Consumption on Body Composition and Performance Measures in Collegiate Female Athletes.

    Science.gov (United States)

    Wilborn, Colin D; Taylor, Lem W; Outlaw, Jordan; Williams, Laura; Campbell, Bill; Foster, Cliffa A; Smith-Ryan, Abbie; Urbina, Stacie; Hayward, Sara

    2013-01-01

    Two of the most popular forms of protein on the market are whey and casein. Both proteins are derived from milk but each protein differs in absorption rate and bioavailability, thus it is possible that each type of protein may contribute differently to the adaptations elicited through resistance training. Therefore, the purpose of this study was to investigate the potential effects of ingestion of two types of protein in conjunction with a controlled resistance training program in collegiate female basketball players. Sixteen NCAA Division III female basketball players were matched according to body mass and randomly assigned in a double-blind manner to consume 24 g whey protein (WP) (N = 8, 20.0 ± 1.9 years, 1.58 ± 0.27 m, 66. 0 ± 4.9 kg, 27.0 ± 4.9 %BF) or 24 g casein protein (CP) (N = 8, 21.0 ± 2.8 years, 1.53 ± 0.29 m, 68.0 ± 2.9 kg, 25.0 ± 5.7 %BF) immediately pre- and post-exercise for eight weeks. Subjects participated in a supervised 4-day per week undulating periodized training program. At 0 and 8 weeks, subjects underwent DXA body composition analysis, and at 0 and 8 weeks underwent one repetition maximum (1RM) strength, muscle endurance, vertical jump, 5-10-5 agility run, and broad jump testing sessions. Data were analyzed using repeated measures ANOVA, and presented as mean ± SD changes from baseline after 60 days. No significant group x time interaction effects were observed among groups in changes in any variable (p > 0.05). A significant time effect was observed for body fat (WP: -2.0 ± 1.1 %BF; CP: -1.0 ± 1.6 %BF, p training program with pre- and post-exercise protein supplementation is capable of inducing significant changes in performance and body composition. There does not appear to be a difference in the performance- enhancing effects between whey and casein proteins. Key pointsFemales can experience and increase in performance makers from consuming protein after resistance training.Females can have a decreased body fat composition

  20. Bending behavior of thermoplastic composite sheets viscoelasticity and temperature dependency in the draping process

    CERN Document Server

    Ropers, Steffen

    2017-01-01

    Within the scope of this work, Steffen Ropers evaluates the viscoelastic and temperature-dependent nature of the bending behavior of thermoplastic composite sheets in order to further enhance the predictability of the draping simulation. This simulation is a useful tool for the development of robust large scale processes for continuously fiber-reinforced polymers (CFRP). The bending behavior thereby largely influences the size and position of wrinkles, which are one of the most common processing defects for continuously fiber-reinforced parts. Thus, a better understanding of the bending behavior of thermoplastic composite sheets as well as an appropriate testing method along with corresponding material models contribute to a wide-spread application of CFRPs in large scale production. Contents Thermoplastic Prepregs Draping Simulation of Thermoplastic Prepregs Bending Characterization of Textile Composites Modeling of Bending Behavior Target Groups Researchers and students in the field of polymer, lightweight,...

  1. Electrical and Self-Sensing Properties of Ultra-High-Performance Fiber-Reinforced Concrete with Carbon Nanotubes

    OpenAIRE

    You, Ilhwan; Yoo, Doo-Yeol; Kim, Soonho; Kim, Min-Jae; Zi, Goangseup

    2017-01-01

    This study examined the electrical and self-sensing capacities of ultra-high-performance fiber-reinforced concrete (UHPFRC) with and without carbon nanotubes (CNTs). For this, the effects of steel fiber content, orientation, and pore water content on the electrical and piezoresistive properties of UHPFRC without CNTs were first evaluated. Then, the effect of CNT content on the self-sensing capacities of UHPFRC under compression and flexure was investigated. Test results indicated that higher ...

  2. Role of the polymeric matrix in the processing and structural properties of composite materials. Proceedings of the Joint U.S.-Italy Symposium on Composite Materials, Capri, Italy, June 15-19, 1981

    International Nuclear Information System (INIS)

    Seferis, J.C.; Nicolais, L.

    1983-01-01

    The interaction between the polymeric matrix and the reinforcing phase and the effect of the matrix on composite performance are discussed under the following headings: chemical and environmental effects, short-fiber reinforcements, interfacial effects, and continuous fiber reinforcements and design. Papers are presented on the factors affecting the development of new matrix resins for advanced composites creep and fracture initiation in fiber-reinforced plastics dimensional stability of reinforced matrices and internal stresses in fiber-reinforced plastics. Other topics discussed include the use of composites in commercial aircraft, design of continuous-fiber composite structures, and delamination in graphite-epoxy. For individual items see A83-46280 to A83-46308

  3. Experimental evaluation and simulation of volumetric shrinkage and warpage on polymeric composite reinforced with short natural fibers

    Science.gov (United States)

    Santos, Jonnathan D.; Fajardo, Jorge I.; Cuji, Alvaro R.; García, Jaime A.; Garzón, Luis E.; López, Luis M.

    2015-09-01

    A polymeric natural fiber-reinforced composite is developed by extrusion and injection molding process. The shrinkage and warpage of high-density polyethylene reinforced with short natural fibers of Guadua angustifolia Kunth are analyzed by experimental measurements and computer simulations. Autodesk Moldflow® and Solid Works® are employed to simulate both volumetric shrinkage and warpage of injected parts at different configurations: 0 wt.%, 20 wt.%, 30 wt.% and 40 wt.% reinforcing on shrinkage and warpage behavior of polymer composite. Become evident the restrictive effect of reinforcing on the volumetric shrinkage and warpage of injected parts. The results indicate that volumetric shrinkage of natural composite is reduced up to 58% with fiber increasing, whereas the warpage shows a reduction form 79% to 86% with major fiber content. These results suggest that it is a highly beneficial use of natural fibers to improve the assembly properties of polymeric natural fiber-reinforced composites.

  4. Application of cementitious composites in mechanical engineering

    Science.gov (United States)

    Fediuk, R. S.; Ibragimov, R. A.; Lesovik, V. S.; Akopian, A. K.; Teleshev, A. A.; Khankhabaev, L. R.; Ivanov, A. S.

    2018-03-01

    The paper presents the results of the development of composite fiber-reinforced concrete for use as basic parts of machine-tools and machines. It was revealed that the additions of fly ash and limestone significantly reduce the cracking of concrete. Thus, a clear relationship between the properties of concrete and the features of the structure of cement stone was revealed. The strength and crack resistance of concrete is increased due to an increase in the number of low-basic calcium hydrosilicates, as well as increased gel porosity and reduced capillary porosity (especially at the submicroscopic level).

  5. Influence of wildfires on atmospheric composition and carbon uptake of forest ecosystems in Central Siberia: the establishing of a long-term post-fire monitoring system

    Science.gov (United States)

    Panov, Alexey; Chi, Xuguang; Winderlich, Jan; Prokushkin, Anatoly; Bryukhanov, Alexander; Korets, Mikhail; Ponomarev, Evgenii; Timokhina, Anastasya; Andreae, Meinrat O.; Heimann, Martin

    2014-05-01

    Calculations of direct emissions of greenhouse gases from boreal wildfires remain uncertain due to problems with emission factors, available carbon, and imprecise estimates of burned areas. Even more varied and sparse are accurate in situ calculations of temporal changes in boreal forest carbon dynamics following fire. Linking simultaneous instrumental atmospheric observations, GIS-based estimates of burned areas, and ecosystem carbon uptake calculations is vital to fill this knowledge gap. Since 2006 the Zotino Tall Tower Observatory (ZOTTO; www.zottoproject.org) a research platform for large-scale climatic observations is operational in Central Siberia (60°48'N, 89°21'E). The data of ongoing greenhouse gases measurements at the tower are used in atmospheric inversions studies to infer the distribution of carbon sinks and sources over central Northern Eurasia. We present our contribution to reducing uncertainties in estimates of fire influence on atmospheric composition and post-fire ecosystem carbon uptake deduced from the large-scale fires that happened in 2012 in the tall tower footprint area. The burned areas were estimated from Landsat ETM 5,8 satellite images, while fires were detected from Terra/Aqua MODIS satellite data. The magnitude of ecological change caused by fires ("burn severity") was measured and mapped with a Normalized Burn Ratio (NBR) index and further calibrated by a complementary field based Composite Burn Index (CBI). Measures of fire radiative power (FRP) index provided information on fire heat release intensity and on the amount and completeness of biomass combustion. Based on the analyzed GIS data, the system of study plots was established in the 5 dominating ecosystem types for a long-term post-fire monitoring. On the plots the comprehensive estimation of ecosystem parameters and carbon pools and their mapping was organized with a laser-based field instrumentation system. The work was supported financially by ISTC Project # 2757p

  6. SEM/XPS analysis of fractured adhesively bonded graphite fibre surface resin-rich/graphite fibre composites

    Science.gov (United States)

    Devilbiss, T. A.; Wightman, J. P.; Progar, D. J.

    1988-01-01

    Samples of graphite fiber-reinforced polyimide were fabricated allowing the resin to accumulate at the composite surface. These surface resin-rich composites were then bonded together and tested for lap shear strength both before and after thermal aging. Lap shear strength did not appear to show a significant improvement over that previously recorded for resin-poor samples and was shown to decrease with increasing aging time and temperature.

  7. Compositional and structural changes in TiB2 films induced by bias, in situ and post-deposition annealing, respectively

    International Nuclear Information System (INIS)

    Pelleg, Joshua; Sade, G.; Sinder, M.; Mogilyanski, D.

    2006-01-01

    Structural changes in TiB 2 films were induced at relatively low temperatures by the application of bias and in situ annealing or by post-deposition heat treatment of samples subjected to bias with simultaneous in situ annealing. In situ annealing by itself evoked only partial crystallization. Application of bias by itself only modified the composition of the as deposited film. A simple model is presented to explain the variation of the composition when RF bias is applied to a cold substrate. The crystallized films had a (0001) texture. A model has been suggested to explain the observed preferred orientation, based on the contribution of surface and strain energies. Both, the surface energy and strain energy are direction dependent. These were evaluated for two film orientations reported in the literature, namely, the (0001) and (101-bar 1)orientations. The preferred orientation of the film is determined by the lowest overall free energy resulting from the competition between the surface energy and the strain energy on different lattice planes. The surface energy is not film thickness dependent while the strain energy is thickness dependent and increases with it. For small film thickness, as in this work, the surface energy term is significant and (0001) orientation with a minimum surface energy is preferred. At large film thicknesses the strain energy becomes dominant and the (101-bar 1) preferred orientation is observed. Under certain experimental conditions strain energy effects may tip the preferred orientation to (101-bar 1). The elastic moduli in the (0001) and (101-bar 1) directions were determined as 435 and 538GPa, respectively

  8. Monitoring post-fire changes in species composition and stand structure in boreal forests using high-resolution, 3-D aerial drone data and Landsat

    Science.gov (United States)

    Alonzo, M.; Morton, D. C.; Cook, B.; Andersen, H. E.; Mack, M. C.

    2017-12-01

    The growing frequency and severity of boreal forest fires has important consequences for fire carbon emissions and ecosystem composition. Severe fires are typically associated with high degrees of both canopy and soil organic layer (SOL) consumption, particularly in black spruce stands. Complete canopy consumption can decrease the likelihood of spruce regeneration due to reduced viability of the aerial seedbank. Deeper burning of the SOL increases fire emissions and can expose mineral soil that promotes colonization by broadleaf species. There is mounting evidence that a disturbance-driven shift from spruce to broadleaf forests may indicate an ecological state change with feedbacks to regional and global climate. If post-fire successional dynamics can be characterized at an ecosystem scale using remote sensing data, we will be better equipped to constrain carbon and energy fluxes from SOL losses and albedo changes. In this study, we used Landsat time series, very high-resolution structure-from-motion (SFM) drone imagery, and field measurements to investigate post-fire regrowth 13 years after the 2004 Taylor Complex (TC) fires in interior Alaska. Twenty-seven TC plots span a gradient of moisture conditions and burn severity as estimated by loss of SOL. A range of variables potentially governing seedling species dominance (e.g., moisture status, distance to seed sources) have been collected systematically over the years following fire. In July 2017, we additionally collected drone imagery over 25 of the TC plots. We processed these highly overlapped, nadir-view and oblique angle photos into extremely dense (>700 pts/m2) RGB-colored point clouds using SFM techniques. With these point clouds and high resolution orthomosaics, we estimated: 1) snag heights and biomass, 2) remnant snag fine branching, and 3) species and structure of shrubs and groundcover that have regrown since fire. We additionally assembled a dense Landsat time series arranged by day-of-year to monitor

  9. Post-impact fatigue of cross-plied, through-the-thickness reinforced carbon/epoxy composites. M.S. Thesis - Clemson Univ.

    Science.gov (United States)

    Serdinak, Thomas E.

    1994-01-01

    An experimental investigation of the post-impact fatigue response of integrally woven carbon/epoxy composites was conducted. Five different through-the-thickness (TTT) reinforcing fibers were used in an experimental textile process that produced an integrally woven (0/90/0/90/0/90/0/90/0)(sub T) ply layup with 21K AS4 carbon tow fiber. The resin was Hercules 3501-6, and the five TTT reinforcing fibers were Kevlar, Toray carbon, AS4 carbon, glass, and IM6 carbon. The purpose of this investigation was to study the post-impact fatigue response of these material systems and to identify the optimum TTT fiber. Samples were impacted with one half inch diameter aluminum balls with an average velocity of 543 ft/sec. Post-impact static compression and constant amplitude tension-compression fatigue tests were conducted. Fatigue tests were conducted with a loading ratio of R=-5, and frequency of 4 Hz. Damage growth was monitored using x-radiographic and sectioning techniques and by examining the stress-strain response (across the impact site) throughout the fatigue tests. The static compressive stress versus far-field strain response was nearly linear for all material groups. All the samples had a transverse shear failure mode. The average compressive modulus (from far-field strain) was about 10 Msi. The average post-impact static compressive strength was about 35.5 Ksi. The IM6 carbon sample had a strength of over 40 Ksi, more than 16 percent stronger than average. There was considerable scatter in the S-N data. However, the IM6 carbon samples clearly had the best fatigue response. The response of the other materials, while worse than IM6 carbon, could not be ranked definitively. The initial damage zones caused by the impact loading and damage growth from fatigue loading were similar for all five TTT reinforcing materials. The initial damage zones were circular and consisted of delaminations, matrix cracks and ply cracks. Post-impact fatigue loading caused delamination growth

  10. Trends in restorative composites research: what is in the future?

    Science.gov (United States)

    Maas, Mariel Soeiro; Alania, Yvette; Natale, Livia Camargo; Rodrigues, Marcela Charantola; Watts, David Christopher; Braga, Roberto Ruggiero

    2017-08-28

    Clinical trials have identified secondary caries and bulk fracture as the main causes for composite restoration failure. As a measure to avoid frequent reinterventions for restoration replacement, composites with some sort of defense mechanism against biofilm formation and demineralization, as well as materials with lower susceptibility to crack propagation are necessary. Also, the restorative procedure with composites are very time-consuming and technically demanding, particularly concerning the application of the adhesive system. Therefore, together with bulk-fill composites, self-adhesive restorative composites could reduce operator error and chairside time. This literature review describes the current stage of development of remineralizing, antibacterial and self-healing composites. Also, an overview of the research on fiber-reinforced composites and self-adhesive composites, both introduced for clinical use in recent years, is presented.

  11. Modeling of damage evaluation in thin composite plate loaded by pressure loading

    Directory of Open Access Journals (Sweden)

    Dudinský M.

    2012-12-01

    Full Text Available This article presents the results of numerical analysis of elastic damage of thin laminated long fiber-reinforced composite plate consisting of unidirectional layers which is loaded by uniformly distributed pressure. The analysis has been performed by means of the finite element method (FEM. The numerical implementation uses layered plate finite elements based on the Kirchhoff plate theory. System of nonlinear equations has been solved by means of the Newton- Raphson procedure. Evolution of damage has been solved using the return-mapping algorithm based on the continuum damage mechanics (CDM. The analysis was performed using own program created in MATLAB. Problem of laminated fiber-reinforced composite plate fixed on edges for two different materials and three different laminate stacking sequences (LSS was simulated. Evolution of stresses vs. strains and also evolution of damage variables in critical points of the structure are shown.

  12. Flexural Behavior of High-Volume Steel Fiber Cementitious Composite Externally Reinforced with Basalt FRP Sheet

    Directory of Open Access Journals (Sweden)

    Seungwon Kim

    2016-01-01

    Full Text Available High-performance fiber-reinforced cementitious composites (HPFRCCs are characterized by unique tensile strain hardening and multiple microcracking behaviors. The HPFRCC, which demonstrates remarkable properties such as strength, ductility, toughness, durability, stiffness, and thermal resistance, is a class of fiber cement composite with fine aggregates. It can withstand tensile stresses by forming distributed microcracks owing to the embedded fibers in the concrete, which improve the energy absorption capacity and apparent ductility. This high energy absorbing capacity can be enhanced further by an external stiff fiber-reinforced polymer (FRP. Basalt fabric is externally bonded as a sheet on concrete materials to enhance the durability and resistance to fire and other environmental attacks. This study investigates the flexural performance of an HPFRCC that is externally reinforced with multiple layers of basalt FRP. The HPFRCC considered in the study contains steel fibers at a volume fraction of 8%.

  13. Warpage Analysis of Electroplated Cu Films on Fiber-Reinforced Polymer Packaging Substrates

    Directory of Open Access Journals (Sweden)

    Cheolgyu Kim

    2015-06-01

    Full Text Available This paper presents a warpage analysis method that predicts the warpage behavior of electroplated Cu films on glass fiber-reinforced polymer (GFRP packaging substrates. The analysis method is performed using the following sequence: fabricate specimens for scanning 3D contours, transform 3D data into curvatures, compute the built-in stress of the film using a stress-curvature analytic model, and verify it through comparisons of the finite element method (FEM simulations with the measured data. The curvature is used to describe the deflection and warpage modes and orientations of the specimen. Two primary factors that affect the warpage behavior of the electroplated Cu film on FRP substrate specimens are investigated. The first factor is the built-in stress in a Cu film that explains the room temperature warpage of the specimen under no thermal process. The second factor is the misfit of the coefficient of thermal expansion (CTE between the Cu and FRP layer, which is a dominant factor during the temperature change. The calculated residual stress, and predicted curvatures using FEM simulation throughout the reflow process temperature range between 25 and 180 °C are proven to be accurate by the comparison of the FEM simulations and experiment measurements.

  14. AE analysis of delamination crack propagation in carbon fiber-reinforced polymer materials

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Sang Jae; Arakawa, Kazuo [Kyushu University, kasuga (Japan); Chen, Dingding [National University of Defense Technology, Changsha (China); Han, Seung Wook; Choi, Nak Sam [Hanyang University, Seoul (Korea, Republic of)

    2015-01-15

    Delamination fracture behavior was investigated using acoustic emission (AE) analysis on carbon fiber-reinforced polymer (CFRP) samples manufactured using vacuum-assisted resin transfer molding (VARTM). CFRP plate was fabricated using unidirectional carbon fiber fabric with a lay-up of six plies [+30/-30]6 , and a Teflon film was inserted as a starter crack. Test pieces were sectioned from the inlet and vent of the mold, and packed between two rectangular epoxy plates to load using a universal testing machine. The AE signals were monitored during tensile loading using two sensors. The average tensile load of the inlet specimens was slightly larger than that of the vent specimens; however, the data exhibited significant scattering due to non-uniform resin distribution, and there was no statistically significant different between the strength of the samples sectioned from the inlet or outlet of the mold. Each of the specimens exhibited similar AE characteristics, regardless of whether they were from the inlet or vent of the mold. Four kinds of damage mechanism were observed: micro-cracking, fiber-resin matrix debonding, fiber pull-out, and fiber failure; and three stages of the crack propagation process were identified.

  15. State-of-the-Art Report on Fiber-Reinforced Lightweight Aggregate Concrete Masonry

    Directory of Open Access Journals (Sweden)

    Saul Rico

    2017-01-01

    Full Text Available Masonry construction is the most widely used building method in the world. Concrete masonry is relatively low in cost due to the vast availability of aggregates used within the production process. These aggregate materials are not always reliable for structural use. One of the principal issues associated with masonry is the brittleness of the unit. When subject to seismic loads, the brittleness of the masonry magnifies. In regions with high seismic activity and unspecified building codes or standards, masonry housing has developed into a death trap for countless individuals. A common approach concerning the issue associated with the brittle characteristic of masonry is addition of steel reinforcement. However, this can be expensive, highly dependent on skillfulness of labor, and particularly dependent on the quality of available steel. A proposed solution presented in this investigation consists of introducing steel fibers to the lightweight aggregate concrete masonry mix. Previous investigations in the field of lightweight aggregate fiber-reinforced concrete have shown an increase in flexural strength, toughness, and ductility. The outcome of this research project provides invaluable data for the production of a ductile masonry unit capable of withstanding seismic loads for prolonged periods.

  16. Influence of Tool Shape on Hole Clinching for Carbon Fiber-Reinforced Plastic and SPRC440

    Directory of Open Access Journals (Sweden)

    Seung-Hun Lee

    2014-04-01

    Full Text Available Carbon fiber-reinforced plastic (CFRP is a lightweight material that can potentially replace structural steel components in automobiles. The hole-clinching process is a mechanical clinching technique for joining brittle or low-ductility materials, such as CFRP, with ductile materials. In this study, the influence of tool shape on the hole-clinching process for CFRP and SPRC440 was investigated using FE-analysis and experiments. The parameters of the tool shape investigated were the punch corner radius and the punch diameter. The geometrical interlocking shapes of hole-clinched joints were characterized by neck thickness and undercut. Based on the desired joint strength of 2.5 kN, hole-clinching tools were designed on the basis of the relationship between joint strength and geometrical interlocking. FE-analysis and hole-clinching experiments were performed with the designed hole-clinching tools to investigate the geometrical interlocking shape as well as joinability, including neck fracture, undercut, and hole expansion, resulting from changes in tool parameters. Joint strength was evaluated to verify the effectiveness of hole clinching by a single lap shear test.

  17. High-Temperature Performance and Multiscale Damage Mechanisms of Hollow Cellulose Fiber-Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Liping Guo

    2016-01-01

    Full Text Available Spalling resistance properties and their damage mechanisms under high temperatures are studied in hollow cellulose fiber-reinforced concrete (CFRC used in tunnel structures. Measurements of mass loss, relative dynamic elastic modulus, compressive strength, and splitting tensile strength of CFRC held under high temperatures (300, 600, 800, and 1050°C for periods of 2.5, 4, and 5.5 h were carried out. The damage mechanism was analyzed using scanning electron microscopy, mercury intrusion porosimetry, thermal analysis, and X-ray diffraction phase analysis. The results demonstrate that cellulose fiber can reduce the performance loss of concrete at high temperatures; the effect of holding time on the performance is more noticeable below 600°C. After exposure to high temperatures, the performance of ordinary concrete deteriorates faster and spalls at 700–800°C; in contrast, cellulose fiber melts at a higher temperature, leaving a series of channels in the matrix that facilitate the release of the steam pressure inside the CFRC. Hollow cellulose fibers can thereby slow the damage caused by internal stress and improve the spalling resistance of concrete under high temperatures.

  18. Laser-Based Surface Modification of Microstructure for Carbon Fiber-Reinforced Plastics

    Science.gov (United States)

    Yang, Wenfeng; Sun, Ting; Cao, Yu; Li, Shaolong; Liu, Chang; Tang, Qingru

    2018-05-01

    Bonding repair is a powerful feature of carbon fiber-reinforced plastics (CFRP). Based on the theory of interface bonding, the interface adhesion strength and reliability of the CFRP structure will be directly affected by the microscopic features of the CFRP surface, including the microstructure, physical, and chemical characteristics. In this paper, laser-based surface modification was compared to Peel-ply, grinding, and polishing to comparatively evaluate the surface microstructure of CFRP. The surface microstructure, morphology, fiber damage, height and space parameters were investigated by scanning electron microscopy (SEM) and laser confocal microscopy (LCM). Relative to the conventional grinding process, laser modification of the CFRP surface can result in more uniform resin removal and better processing control and repeatability. This decreases the adverse impact of surface fiber fractures and secondary damage. The surface properties were significantly optimized, which has been reflected such things as the obvious improvement of surface roughness, microstructure uniformity, and actual area. The improved surface microstructure based on laser modification is more conducive to interface bonding of CFRP structure repair. This can enhance the interfacial adhesion strength and reliability of repair.

  19. A biologically inspired artificial muscle based on fiber-reinforced and electropneumatic dielectric elastomers

    Science.gov (United States)

    Liu, Lei; Zhang, Chi; Luo, Meng; Chen, Xi; Li, Dichen; Chen, Hualing

    2017-08-01

    Dielectric elastomers (DEs) have great potential for use as artificial muscles because of the following characteristics: electrical activity, fast and large deformation under stimuli, and softness as natural muscles. Inspired by the traditional McKibben actuators, in this study, we developed a cylindrical soft fiber-reinforced and electropneumatic DE artificial muscle (DEAM) by mimicking the spindle shape of natural muscles. Based on continuum mechanics and variation principle, the inhomogeneous actuation of DEAMs was theoretically modeled and calculated. Prototypes of DEAMs were prepared to validate the design concept and theoretical model. The theoretical predictions are consistent with the experimental results; they successfully predicted the evolutions of the contours of DEAMs with voltage. A pneumatically supported high prestretch in the hoop direction was achieved by our DEAM prototype without buckling the soft fibers sandwiched by the DE films. Besides, a continuously tunable prestretch in the actuation direction was achieved by varying the supporting pressure. Using the theoretical model, the failure modes, maximum actuations, and critical voltages were analyzed; they were highly dependent on the structural parameters, i.e., the cylinder aspect ratio, prestretch level, and supporting pressure. The effects of structural parameters and supporting pressure on the actuation performance were also investigated to optimize the DEAMs.

  20. Use of Fiber-Reinforced Cements in Masonry Construction and Structural Rehabilitation

    Directory of Open Access Journals (Sweden)

    Ece Erdogmus

    2015-02-01

    Full Text Available The use of fiber reinforcement in traditional concrete mixes has been extensively studied and has been slowly finding its regular use in practice. In contrast, opportunities for the use of fibers in masonry applications and structural rehabilitation projects (masonry and concrete structures have not been as deeply investigated, where the base matrix may be a weaker cementitious mixture. This paper will summarize the findings of the author’s research over the past 10 years in these particular applications of fiber reinforced cements (FRC. For masonry, considering both mortar and mortar-unit bond characteristics, a 0.5% volume fraction of micro fibers in type N Portland cement lime mortar appear to be a viable recipe for most masonry joint applications both for clay and concrete units. In general, clay units perform better with high water content fiber reinforced mortar (FRM while concrete masonry units (CMUs perform better with drier mixtures, so 130% and 110% flow rates should be targeted, respectively. For earth block masonry applications, fibers’ benefits are observed in improving local damage and water pressure resistance. The FRC retrofit technique proposed for the rehabilitation of reinforced concrete two-way slabs has exceeded expectations in terms of capacity increase for a relatively low cost in comparison to the common but expensive fiber reinforced polymer applications. For all of these applications of fiber-reinforced cements, further research with larger data pools would lead to further optimization of fiber type, size, and amount.

  1. Seismic Performance of High-Ductile Fiber-Reinforced Concrete Short Columns

    Directory of Open Access Journals (Sweden)

    Mingke Deng

    2018-01-01

    Full Text Available This study mainly aims to investigate the effectiveness of high-ductile fiber-reinforced concrete (HDC as a means to enhance the seismic performance of short columns. Six HDC short columns and one reinforced concrete (RC short column were designed and tested under lateral cyclic loading. The influence of the material type (concrete or HDC, axial load, stirrup ratio, and shear span ratio on crack patterns, hysteresis behavior, shear strength, deformation capacity, energy dissipation, and stiffness degradation was presented and discussed, respectively. The test results show that the RC short column failed in brittle shear with poor energy dissipation, while using HDC to replace concrete can effectively improve the seismic behavior of the short columns. Compared with the RC short column, the shear strength of HDC specimens was improved by 12.6–30.2%, and the drift ratio and the energy dissipation increases were 56.9–88.5% and 237.7–336.7%, respectively, at the ultimate displacement. Additionally, the prediction model of the shear strength for RC columns based on GB50010-2010 (Chinese code can be safely adopted to evaluate the shear strength of HDC short columns.

  2. High-temperature protective coatings for C/SiC composites

    OpenAIRE

    Xiang Yang; Chen Zhao-hui; Cao Feng

    2014-01-01

    Carbon fiber-reinforced silicon carbide (C/SiC) composites were well-established light weight materials combining high specific strength and damage tolerance. For high-temperature applications, protective coatings had to provide oxidation and corrosion resistance. The literature data introduced various technologies and materials, which were suitable for the application of coatings. Coating procedures and conditions, materials design limitations related to the reactivity of the components of C...

  3. Inkjet Assisted Creation of Self-Healing Layers Between Composite Plies

    Science.gov (United States)

    2013-07-29

    technology into a prepreg manufacturing process. The approach consisted of depositing novel thermoplastic low-viscosity microdroplets with chemically and...mechanically comparable properties to epoxy matrix in aerospace grade composites onto fiber-reinforced epoxy prepregs before curing using an ink-jet... prepreg Cycom977-2. Double cantilever beam (DCB) and short beam shear (SBS) tests were used to evaluate the self-healing efficiency. It was shown

  4. TiC growth in C fiber/Ti alloy composites during liquid infiltration

    Science.gov (United States)

    Warrier, S. G.; Lin, R. Y.

    1993-01-01

    A cylindrical model is developed for predicting the reaction zone thickness of carbon fiber-reinforced Ti-matrix composites, and good agreement is obtained between its predicted values and experimental results. The reaction-rate constant for TiC formation is estimated to be 1.5 x 10 exp -9 sq cm/sec. The model is extended to evaluate the relationship between C-coating thicknesses on SiC fibers and processing times.

  5. Monitoring Poisson's ratio degradation of FRP composites under fatigue loading using biaxially embedded FBG sensors

    OpenAIRE

    Akay, Erdem; Yılmaz, Çağatay; Yilmaz, Cagatay; Kocaman, Esat Selim; Türkmen, Halit S.; Turkmen, Halit S.; Yıldız, Mehmet; Yildiz, Mehmet

    2016-01-01

    The significance of strain measurement is obvious for the analysis of Fiber-Reinforced Polymer (FRP) composites. Conventional strain measurement methods are sufficient for static testing in general. Nevertheless, if the requirements exceed the capabilities of these conventional methods, more sophisticated techniques are necessary to obtain strain data. Fiber Bragg Grating (FBG) sensors have many advantages for strain measurement over conventional ones. Thus, the present paper suggests a novel...

  6. Aging linear viscoelasticity of matrix-inclusion composite materials featuring ellipsoidal inclusions

    OpenAIRE

    LAVERGNE, Francis; SAB, Karam; SANAHUJA, Julien; BORNERT, Michel; TOULEMONDE, Charles

    2016-01-01

    A multi-scale homogenization scheme is proposed to estimate the time-dependent strains of fiber-reinforced concrete. This material is modeled as an aging linear viscoelastic composite material featuring ellipsoidal inclusions embedded in a viscoelastic cementitious matrix characterized by a time-dependent Poisson's ratio. To this end, the homogenization scheme proposed in Lavergne et al. [1] is adapted to the case of a time-dependent Poisson's ratio and it is successfully validated on a non-a...

  7. THE EFFECTS OF PRE-AND POST-EXERCISE WHEY VS. CASEIN PROTEIN CONSUMPTION ON BODY COMPOSITION AND PERFORMANCE MEASURES IN COLLEGIATE FEMALE ATHLETES

    Directory of Open Access Journals (Sweden)

    olin D. Wilborn

    2013-03-01

    Full Text Available Two of the most popular forms of protein on the market are whey and casein. Both proteins are derived from milk but each protein differs in absorption rate and bioavailability, thus it is possible that each type of protein may contribute differently to the adaptations elicited through resistance training. Therefore, the purpose of this study was to investigate the potential effects of ingestion of two types of protein in conjunction with a controlled resistance training program in collegiate female basketball players. Sixteen NCAA Division III female basketball players were matched according to body mass and randomly assigned in a double-blind manner to consume 24 g whey protein (WP (N = 8, 20.0 ± 1.9 years, 1.58 ± 0.27 m, 66. 0 ± 4.9 kg, 27.0 ± 4.9 %BF or 24 g casein protein (CP (N = 8, 21.0 ± 2.8 years, 1.53 ± 0.29 m, 68.0 ± 2.9 kg, 25.0 ± 5.7 %BF immediately pre- and post-exercise for eight weeks. Subjects participated in a supervised 4-day per week undulating periodized training program. At 0 and 8 weeks, subjects underwent DXA body composition analysis, and at 0 and 8 weeks underwent one repetition maximum (1RM strength, muscle endurance, vertical jump, 5-10-5 agility run, and broad jump testing sessions. Data were analyzed using repeated measures ANOVA, and presented as mean ± SD changes from baseline after 60 days. No significant group x time interaction effects were observed among groups in changes in any variable (p > 0.05. A significant time effect was observed for body fat (WP: -2.0 ± 1.1 %BF; CP: -1.0 ± 1.6 %BF, p < 0.001, lean mass (WP: 1.5 ± 1.0 kg; CP: 1. 4 ± 1.0 kg, p < 0.001, fat mass (WP: -1.3 ± 1.2 kg; CP: -0.6 ± 1.4 kg, p < 0.001, leg press 1RM (WP: 88.7 ± 43.9 kg; CP: 90.0 ± 48.5 kg, p < 0.001, bench press 1RM (WP: 7.5 ± 4.6 kg; CP: 4.3 ± 4.5 kg, p = 0.01, vertical jump (WP: 4.1 ± 1.8 cm; CP: 3.5 ± 7.6 cm, p < 0.001, 5-10-5 (WP: -0.3 ± 0.2 sec; CP: -0.09 ± 0.42 sec, p < 0.001, and broad jump (WP: 10

  8. Effects of hydrophilic solvent and oxidation resistance post surface treatment on molecular structure and forward osmosis performance of polyamide thin-film composite (TFC) membranes

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Qibo; Xu, Yangyu [School of Environment, Tsinghua University, Beijing 100084 (China); Shen, Jianquan [Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Yang, Haijun, E-mail: yanghj@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Zhou, Lu, E-mail: zhoulu@tsinghua.edu.cn [School of Environment, Tsinghua University, Beijing 100084 (China)

    2015-11-30

    Graphical abstract: - Highlights: • NMP promotes swelling of polyamide, which enhances the TFC FO membrane water flux. • Electron-withdrawing carboxyl groups reduce the activity of polyamide molecules. • TMC and oxalic acid can improve the oxidation resistance properties of the FO membrane. • Oxalic acid and EDC improve the FO membrane separation performance significantly. - Abstract: In this article, novel hydrophilic solvents and antioxidants were used to post-treat aromatic polyamide thin-film composite (TFC) hollow fiber forward osmosis (FO) membranes. The effects of trimesoyl chloride (TMC) and oxalic acid on the structure of polyamide skin layer were investigated using ATR-FTIR and XPS analyses. Pure water flux and rejection of salts were detected using 2 M NaCl solution as draw solutions in FO processes. The results demonstrated that hydrophilic solvent N-methyl pyrrolidone (NMP) enhanced the water flux and kept a high salt retention of the TFC FO membrane. TMC and oxalic acid were both found to improve the oxidation resistance properties of the skin layer of TFC membrane because the electron-withdrawing carboxyl groups reduced the activity of polyamide molecular. The effects of the oxalic acid and carbodiimide on the molecular structures and the FO water flux of the polyamide TFC membranes were more marked than those of TMC. The novel TFC FO membrane treated by oxalic acid and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) exhibited a high level of water flux (20.33 L m{sup −2} h{sup −1}), and the rates of salt rejection and salt reverse rejection were higher by 50% and 83%, respectively.

  9. Influence of retainer design on two-unit cantilever resin-bonded glass fiber reinforced composite fixed dental prostheses: an in vitro and finite element analysis study.

    Science.gov (United States)

    Keulemans, Filip; De Jager, Niek; Kleverlaan, Cornelis J; Feilzer, Albert J

    2008-10-01

    The aim of this study was to evaluate in vitro the influence of retainer design on the strength of two-unit cantilever resin-bonded glass fiber-reinforced composite (FRC) fixed dental prostheses (FDP). Four retainer designs were tested: a proximal box, a step-box, a dual wing, and a step-box-wing. Of each design on 8 human mandibular molars, FRC-FDPs of a premolar size were produced. The FRC framework was made of resin impregnated unidirectional glass fibers (Estenia C&B EG Fiber, Kuraray) and veneered with hybrid resin composite (Estenia C&B, Kuraray). Panavia F 2.0 (Kuraray) was used as resin luting cement. FRC-FDPs were loaded to failure in a universal testing machine. One-way ANOVA and Tukey's post-hoc test were used to evaluate the data. The four designs were analyzed with finite element analysis (FEA) to reveal the stress distribution within the tooth/restoration complex. Significantly lower fracture strengths were observed with inlay-retained FDPs (proximal box: 300 +/- 65 N; step-box: 309 +/- 37 N) compared to wing-retained FDPs (p optimal design for replacement of a single premolar by means of a two-unit cantilever FRC-FDPs.

  10. Electrical and Mechanical Performance of Carbon Fiber-Reinforced Polymer Used as the Impressed Current Anode Material

    Directory of Open Access Journals (Sweden)

    Ji-Hua Zhu

    2014-07-01

    Full Text Available An investigation was performed by using carbon fiber-reinforced polymer (CFRP as the anode material in the impressed current cathodic protection (ICCP system of steel reinforced concrete structures. The service life and performance of CFRP were investigated in simulated ICCP systems with various configurations. Constant current densities were maintained during the tests. No significant degradation in electrical and mechanical properties was found for CFRP subjected to anodic polarization with the selected applied current densities. The service life of the CFRP-based ICCP system was discussed based on the practical reinforced concrete structure layout.

  11. Electrical and Mechanical Performance of Carbon Fiber-Reinforced Polymer Used as the Impressed Current Anode Material.

    Science.gov (United States)

    Zhu, Ji-Hua; Zhu, Miaochang; Han, Ningxu; Liu, Wei; Xing, Feng

    2014-07-24

    An investigation was performed by using carbon fiber-reinforced polymer (CFRP) as the anode material in the impressed current cathodic protection (ICCP) system of steel reinforced concrete structures. The service life and performance of CFRP were investigated in simulated ICCP systems with various configurations. Constant current densities were maintained during the tests. No significant degradation in electrical and mechanical properties was found for CFRP subjected to anodic polarization with the selected applied current densities. The service life of the CFRP-based ICCP system was discussed based on the practical reinforced concrete structure layout.

  12. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    International Nuclear Information System (INIS)

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Woods, J.J.

    1996-06-01

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1,000 C. The irradiation was conducted in the EBR-II to doses of 33 and 43 dpa-SiC (185 EFPD) at a nominal temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. Exposure to the 165 day anneal did not appreciably degrade the conductivity of the monolithic or particulate-reinforced composites, but the conductivity of the fiber-reinforced composites was slightly degraded. The crystalline SiC-based materials tested in this study exhibited thermal conductivity degradation of irradiation, presumably caused by the presence of irradiation-induced defects. Irradiation-induced conductivity degradation was greater at lower temperatures, and was typically more pronounced for materials with higher unirradiated conductivity. Annealing the irradiated specimens for one hour at 150 C above the irradiation temperature produced an increase in thermal conductivity, which is likely the result of interstitial-vacancy pair recombination. Multiple post-irradiation anneals on CVD β-SiC indicated that a portion of the irradiation-induced damage was permanent. A possible explanation for this phenomenon was the formation of stable dislocation loops at the high irradiation temperature and/or high dose that prevented subsequent interstitial/vacancy recombination

  13. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    International Nuclear Information System (INIS)

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Woods, J.J.

    1997-05-01

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1,000 C. The irradiation was conducted in the EBR-II to doses of 33 and 43 dpa-SiC (185 EFPD) at a nominal temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. Exposure to the 165 day anneal did not appreciably degrade the conductivity of the monolithic or particulate-reinforced composites, but the conductivity of the fiber-reinforced composites was slightly degraded. The crystalline SiC-based materials tested in this study exhibited thermal conductivity degradation after irradiation, presumably caused by the presence of irradiation-induced defects. Irradiation-induced conductivity degradation was greater at lower temperatures, and was typically more pronounced for materials with higher unirradiated conductivity. Annealing the irradiated specimens for one hour at 150 C above the irradiation temperature produced an increase in thermal conductivity, which is likely the result of interstitial-vacancy pair recombination. Multiple post-irradiation anneals on CVD β-SiC indicated that a portion of the irradiation-induced damage was permanent. A possible explanation for this phenomenon was the formation of stable dislocation loops at the high irradiation temperature and/or high dose that prevented subsequent interstitial/vacancy recombination

  14. Optics of carbon fiber-reinforced plastics – A theoretical and an experimental study

    International Nuclear Information System (INIS)

    Hohmann, Ansgar; ElMaklizi, Ahmed; Foschum, Florian; Voit, Florian; Bergmann, Florian; Simon, Emanuel; Reitzle, Dominik; Kienle, Alwin

    2016-01-01

    Laser processing of carbon fiber-reinforced plastics (CFRP) as well as their design optimization are strongly emerging fields. As the optics of CFRP is still rather unknown, the optical behavior of CFRP was investigated in this study. Different simulation models were implemented to simulate reflectance from CFRP samples as well as distribution and absorption of light within these samples. The methods include an analytical solution of Maxwell's equations and Monte Carlo solutions of the radiative transfer theory. We show that strong inaccurracies occur, if light propagation in CFRP is modeled using the radiative transfer theory. Therefore, the solution of Maxwell's equations is the method of choice for calculation of light propagation in CFRP. Furthermore, measurements of the reflectance of light from CFRP were performed and compared to the simulations for investigation of the optical behavior. Information on the refractive index of carbon fibers was obtained via goniometric measurements. The amount of reflected light was determined as 6.05±0.38% for light polarized parallel to the fiber direction, while it was 3.65±0.41% for light polarized perpendicular to the fiber direction in case of laser-processed CFRP. - Highlights: • The light scattering of CFRP was studied using Maxwell's equations and radiative transfer theory. • The simulations were validated by experiments. • Strong inaccuracies occur if light propagation in CFRP structures is modeled with the RTT. • The Bouguer–Lambert–Beer model with μ_a=4πf_VIm(n_c_y_l)/λ cannot be used in CFRP samples. • Reflectance values were determined and information on the refractive index was inferred.

  15. Thermal Failure Analysis of Fiber-Reinforced Silica Aerogels under Liquid Nitrogen Thermal Shock

    Directory of Open Access Journals (Sweden)

    Ai Du

    2018-06-01

    Full Text Available Aerogel materials are recognized as promising candidates for the thermal insulator and have achieved great successes for the aerospace applications. However, the harsh environment on the exoplanet, especially for the tremendous temperature difference, tends to affect the tenuous skeleton and performances of the aerogels. In this paper, an evaluation method was proposed to simulate the environment of exoplanet and study the influence on the fiber-reinforced silica aerogels with different supercritical point drying (SPD technology. Thermal conductivity, mechanical property and the microstructure were characterized for understanding the thermal failure mechanism. It was found that structure and thermal property were significantly influenced by the adsorbed water in the aerogels under the thermal shocks. The thermal conductivity of CO2-SPD aerogel increased 35.5% after the first shock and kept in a high value, while that of the ethanol-SPD aerogel increased only 19.5% and kept in a relatively low value. Pore size distribution results showed that after the first shock the peak pore size of the CO2-SPD aerogel increased from 18 nm to 25 nm due to the shrinkage of the skeleton, while the peak pore size of the ethanol-SPD aerogel kept at ~9 nm probably induced by the spring-back effect. An 80 °C treatment under vacuum was demonstrated to be an effective way for retaining the good performance of ethanol-SPD aerogels under the thermal shock. The thermal conductivity increases of the ethanol-SPD aerogels after 5 shocks decreased from ~30 to ~0% via vacuum drying, while the increase of the CO2-SPD aerogels via the same treatments remains ~28%. The high-strain hardening and low-strain soften behaviors further demonstrated the skeleton shrinkage of the CO2-SPD aerogel.

  16. High-rate tensile behavior of steel fiber-reinforced concrete for nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jung Jin; Park, Gi-Joon [Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747 (Korea, Republic of); Kim, Dong Joo, E-mail: djkim75@sejong.ac.kr [Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747 (Korea, Republic of); Moon, Jae Heum; Lee, Jang Hwa [Korea Institute of Construction Technology, 2311 Daewha-Dong, Ilsan-Gu, Goyang-Si, Gyeonggi-Do 411-712 (Korea, Republic of)

    2014-01-15

    Highlights: • The final goal is to develop a fiber reinforced concrete for containment buildings. • High rate tensile behavior of FRC was investigated. • Strain energy frame impact machine was used for tensile impact tests. • Different rate sensitivity of FRC was found according to the type fiber. • Adding more fibers by increasing S/a is positive for higher impact resistance of FRC. -- Abstract: The direct tensile behavior of fiber-reinforced concrete (FRC) at high strain rates were investigated for their potential to enhance the resistance of the containment building of nuclear power plants (NPPs) against aircraft impact. Two types of deformed steel, hooked (H) and twisted (T) fibers were employed. To improve the tensile resistance of FRCs even at higher rates by adding more fibers, the mixture of concrete was modified by either increasing the sand-to-coarse aggregate ratio or decreasing the maximum size of coarse aggregate. All FRC specimens produced two to six times greater tensile strength and one to five times higher toughness at high strain rates (4–53 s{sup −1}) than those at a static rate (0.000167 s{sup −1}). T-fiber generally produced higher tensile strength and toughness than H-fiber at both static and high rates. Although both fibers showed favorable rate sensitivity, T-fiber produced much greater enhancement, at higher strain rates, in tensile strength and slightly lower enhancement in toughness than H-fiber. As the maximum size of coarse aggregate decreased from 19 to 5 mm, the tensile strength and toughness of FRCs with T-fibers noticeably increased at both static and high strain rates.

  17. Influence of Er,Cr:YSGG Laser Surface Treatments on Micro Push-Out Bond Strength of Fiber Posts to Composite Resin Core Materials

    Directory of Open Access Journals (Sweden)

    Mehrsima Ghavami-Lahiji

    2018-03-01

    Full Text Available Statement of problem: The bonding of fiber post to resin core or root dentin is challenged by limited penetration of resin material to the polymeric matrix of fiber posts. Objectives: The purpose of this study was to investigate the effect of Er,Cr:YSGG on micro push-out bond strength of glass fiber posts to resin core material. Materials and Methods: We used 2 commercially available fiber posts, Exacto (Angelus and White Post DC (FGM, which had similar coronal diameters. Specimens of each fiber post (n=36 were randomly divided into three subgroups (n=12 posts per group according to different surface treatment methods: control (no surface treatment, irradiation by 1W Er,Cr:YSGG, and irradiation by 1.5W Er,Cr:YSGG. A cylindrical plastic tube was placed around the post. Resin core material was filled into the tube and cured. Coronal portions of the posts were sectioned into 1-mm-thick slices. Then, the specimens were subjected to a thermocyling device for 3000 cycles. The micro push-out test was carried out using a Universal Testing Machine. Data were analyzed using one-way ANOVA followed by Tukey’s HSD post hoc test to investigate the effect of different surface treatments on each type of fiber post. Results: The 1.5W Er,Cr:YSGG laser statistically reduced micro push-out bond strength values in the Exacto groups (P0.05. Mode of failure analysis showed that mixed failure was the predominant failure type for all surface treatment groups. Conclusions: The beneficial effect of Er,Cr:YSGG laser application could not be confirmed based on the results of this in vitro study. Er,Cr:YSGG laser could not significantly enhance the bond strength values. However, the 1.5W laser statistically decreased micro push-out bond strength in the Exacto fiber posts.

  18. A randomized comparison study regarding the impact of short-duration, high-intensity exercise and traditional exercise on anthropometric and body composition measurement changes in post-menopausal women--A pilot study.

    Science.gov (United States)

    Grossman, Joan A Cebrick; Payne, Ellen K

    2016-03-01

    The mode and duration of exercise necessary to change body composition and reduce weight remains debatable. Menopause results in hormonal changes that preclude weight loss. This randomized pilot study compared the effects of short-duration, high-intensity interval training and traditional exercise on anthropometric and body composition measurement changes in post-menopausal women. To compare the effects of short-duration, high-intensity interval training and traditional methods of exercise (walking) on anthropometric, body composition and body weight change over a 12-week period. Subjects (N = 18) were post-menopausal, sedentary female volunteers, randomly assigned into one of two exercise groups. Both groups exercised five out of seven days for 12 weeks. The resistance group (n = 8) (54.3 ± 7.3 years; BMI = 28.0 ± 2.1 kg/m(2); mean ± SD) exercised for 15.0 ± 3.5 min, which consisted of five different exercise routines including upper and lower extremity, a cardio segment, yoga and abdominal exercises. The walkers (n = 10) (56.6 ± 5.2 years; BMI = 29.2 ± 2.6 kg/m(2); mean ± SD) exercised for 40.0 ± 5.0 min at 65% of their age-predicted maximum heart rate. Relative (%) body fat was measured via DEXA scan, along with five anthropometric measurements, all of which were taken prior to and after 12 weeks. Independent sample t-tests were probed for differences, p ≤ 0.05. No statistically significant changes were determined between the groups for pre-and post-measurements. The outcomes of this study provide a foundation for future comparisons of short-duration high-intensity interval training exercise and traditional exercise, or walking, on anthropometric and body composition measurement changes in sedentary, overweight, post-menopausal females over a 12-week period. © The Author(s) 2016.

  19. Impact of lenalidomide-based induction therapy on the mobilization of CD34+ cells, blood graft cellular composition, and post-transplant recovery in myeloma patients: a prospective multicenter study.

    Science.gov (United States)

    Partanen, Anu; Valtola, Jaakko; Silvennoinen, Raija; Ropponen, Antti; Siitonen, Timo; Putkonen, Mervi; Sankelo, Marja; Pelkonen, Jukka; Mäntymaa, Pentti; Varmavuo, Ville; Jantunen, Esa

    2017-10-01

    Lenalidomide is an immunomodulatory drug that is also currently used in transplant-eligible patients with multiple myeloma. Previous studies have suggested a negative impact of lenalidomide on the mobilization of CD34 + cells. No data are available regarding the more detailed composition of blood grafts after lenalidomide. In a multicenter, prospective study, we analyzed the mobilization of CD34 + cells, graft cellular composition, and post-transplant hematologic recovery in 26 patients with multiple myeloma after lenalidomide-based induction and in 34 lenalidomide-naive controls with multiple myeloma. All patients were mobilized with low-dose cyclophosphamide plus granulocyte-colony-stimulating factor. The cellular composition of the grafts was analyzed from thawed, cryopreserved samples with flow cytometry. Graft function was evaluated by engraftment data and by complete blood counts until 12 months after the graft infusion. Patients in the lenalidomide arm had lower median peak CD34 + counts and approximately 40% lower CD34 + cell yields from the first apheresis session, but these differences were not significant. The median total number of CD34 + cells collected was comparable (6.4 vs. 7.5 × 10 6 /kg). The number of apheresis sessions was higher in the lenalidomide group (2 vs. 1; p = 0.039). The blood graft composition was comparable between the groups. Hematologic recovery within 12 months post-transplant did not differ between the groups. Lenalidomide-based induction seems to have an impact on the number of aphereses performed, but not on the total yields of the CD34 + cells in the graft. Neither cellular composition of the grafts nor post-transplant recovery was affected by the limited pre-transplant exposure to lenalidomide. © 2017 AABB.

  20. Engineering on the straight and narrow: the mechanics of nanofibrous assemblies for fiber-reinforced tissue regeneration.

    Science.gov (United States)

    Mauck, Robert L; Baker, Brendon M; Nerurkar, Nandan L; Burdick, Jason A; Li, Wan-Ju; Tuan, Rocky S; Elliott, Dawn M

    2009-06-01

    Tissue engineering of fibrous tissues of the musculoskeletal system represents a considerable challenge because of the complex architecture and mechanical properties of the component structures. Natural healing processes in these dense tissues are limited as a result of the mechanically challenging environment of the damaged tissue and the hypocellularity and avascular nature of the extracellular matrix. When healing does occur, the ordered structure of the native tissue is replaced with a disorganized fibrous scar with inferior mechanical properties, engendering sites that are prone to re-injury. To address the engineering of such tissues, we and others have adopted a structurally motivated approach based on organized nanofibrous assemblies. These scaffolds are composed of ultrafine polymeric fibers that can be fabricated in such a way to recreate the structural anisotropy typical of fiber-reinforced tissues. This straight-and-narrow topography not only provides tailored mechanical properties, but also serves as a 3D biomimetic micropattern for directed tissue formation. This review describes the underlying technology of nanofiber production and focuses specifically on the mechanical evaluation and theoretical modeling of these structures as it relates to native tissue structure and function. Applying the same mechanical framework for understanding native and engineered fiber-reinforced tissues provides a functional method for evaluating the utility and maturation of these unique engineered constructs. We further describe several case examples where these principles have been put to test, and discuss the remaining challenges and opportunities in forwarding this technology toward clinical implementation.

  1. Engineering on the Straight and Narrow: The Mechanics of Nanofibrous Assemblies for Fiber-Reinforced Tissue Regeneration

    Science.gov (United States)

    Baker, Brendon M.; Nerurkar, Nandan L.; Burdick, Jason A.; Li, Wan-Ju; Tuan, Rocky S.; Elliott, Dawn M.

    2009-01-01

    Tissue engineering of fibrous tissues of the musculoskeletal system represents a considerable challenge because of the complex architecture and mechanical properties of the component structures. Natural healing processes in these dense tissues are limited as a result of the mechanically challenging environment of the damaged tissue and the hypocellularity and avascular nature of the extracellular matrix. When healing does occur, the ordered structure of the native tissue is replaced with a disorganized fibrous scar with inferior mechanical properties, engendering sites that are prone to re-injury. To address the engineering of such tissues, we and others have adopted a structurally motivated approach based on organized nanofibrous assemblies. These scaffolds are composed of ultrafine polymeric fibers that can be fabricated in such a way to recreate the structural anisotropy typical of fiber-reinforced tissues. This straight-and-narrow topography not only provides tailored mechanical properties, but also serves as a 3D biomimetic micropattern for directed tissue formation. This review describes the underlying technology of nanofiber production and focuses specifically on the mechanical evaluation and theoretical modeling of these structures as it relates to native tissue structure and function. Applying the same mechanical framework for understanding native and engineered fiber-reinforced tissues provides a functional method for evaluating the utility and maturation of these unique engineered constructs. We further describe several case examples where these principles have been put to test, and discuss the remaining challenges and opportunities in forwarding this technology toward clinical implementation. PMID:19207040

  2. A stochastic multiscale method for the elastodynamic wave equation arising from fiber composites

    KAUST Repository

    Babuška, Ivo; Motamed, Mohammad; Tempone, Raul

    2014-01-01

    We present a stochastic multilevel global–local algorithm for computing elastic waves propagating in fiber-reinforced composite materials. Here, the materials properties and the size and location of fibers may be random. The method aims at approximating statistical moments of some given quantities of interest, such as stresses, in regions of relatively small size, e.g. hot spots or zones that are deemed vulnerable to failure. For a fiber-reinforced cross-plied laminate, we introduce three problems (macro, meso, micro) corresponding to the three natural scales, namely the sizes of laminate, ply, and fiber. The algorithm uses the homogenized global solution to construct a good local approximation that captures the microscale features of the real solution. We perform numerical experiments to show the applicability and efficiency of the method.

  3. A stochastic multiscale method for the elastodynamic wave equation arising from fiber composites

    KAUST Repository

    Babuška, Ivo

    2014-03-21

    We present a stochastic multilevel global–local algorithm for computing elastic waves propagating in fiber-reinforced composite materials. Here, the materials properties and the size and location of fibers may be random. The method aims at approximating statistical moments of some given quantities of interest, such as stresses, in regions of relatively small size, e.g. hot spots or zones that are deemed vulnerable to failure. For a fiber-reinforced cross-plied laminate, we introduce three problems (macro, meso, micro) corresponding to the three natural scales, namely the sizes of laminate, ply, and fiber. The algorithm uses the homogenized global solution to construct a good local approximation that captures the microscale features of the real solution. We perform numerical experiments to show the applicability and efficiency of the method.

  4. A Stochastic Multiscale Method for the Elastic Wave Equations Arising from Fiber Composites

    KAUST Repository

    Babuska, Ivo

    2016-01-06

    We present a stochastic multilevel global-local algorithm [1] for computing elastic waves propagating in fiber-reinforced polymer composites, where the material properties and the size and distribution of fibers in the polymer matrix may be random. The method aims at approximating statistical moments of some given quantities of interest, such as stresses, in regions of relatively small size, e.g. hot spots or zones that are deemed vulnerable to failure. For a fiber-reinforced cross-plied laminate, we introduce three problems: 1) macro; 2) meso; and 3) micro problems, corresponding to the three natural length scales: 1) the sizes of plate; 2) the tickles of plies; and 3) and the diameter of fibers. The algorithm uses a homogenized global solution to construct a local approximation that captures the microscale features of the problem. We perform numerical experiments to show the applicability and efficiency of the method.

  5. An applied investigation of kenaf-based fiber/polymer composites as potential lightweight materials for automotive components

    Science.gov (United States)

    Du, Yicheng

    Natural fibers have the potential to replace glass fibers in fiber-reinforced composite applications. However, the natural fibers' intrinsic properties cause these issues: (1) the mechanical property variation; (2) moisture uptake by natural fibers and their composites; (3) lack of sound, cost-effective, environment-friendly fiber-matrix compounding processes; (4) incompatibility between natural fibers and polymer matrices; and (5) low heat-resistance of natural fibers and their composites. This dissertation systematically studied the use of kenaf bast fiber bundles, obtained via a mechanical retting method, as a light-weight reinforcement material for fiber-reinforced thermoset polymer composites for automotive applications. Kenaf bast fiber bundle tensile properties were tested, and the effects of locations in the kenaf plant, loading rates, retting methods, and high temperature treatments and their durations on kenaf bast fiber bundle tensile properties were evaluated. A process has been developed for fabricating high fiber loading kenaf bast fiber bundle-reinforced unsaturated polyester composites. The generated composites possessed high elastic moduli and their tensile strengths were close to specification requirements for glass fiber-reinforced sheet molding compounds. Effects of fiber loadings and lengths on resultant composite's tensile properties were evaluated. Fiber loadings were very important for composite tensile modulus. Both fiber loadings and fiber lengths were important for composite tensile strengths. The distributions of composite tensile, flexural and impact strengths were analyzed. The 2-parameter Weibull model was found to be the most appropriate for describing the composite strength distributions and provided the most conservative design values. Kenaf-reinforced unsaturated polyester composites were also proved to be more cost-effective than glass fiber-reinforced SMCs at high fiber loadings. Kenaf bast fiber bundle-reinforced composite

  6. Experimental design and analysis for irradiation of SiC/SiC composite tubes under a prototypic high heat flux

    Science.gov (United States)

    Petrie, Christian M.; Koyanagi, Takaaki; McDuffee, Joel L.; Deck, Christian P.; Katoh, Yutai; Terrani, Kurt A.

    2017-08-01

    The purpose of this work is to design an irradiation vehicle for testing silicon carbide (SiC) fiber-reinforced SiC matrix composite cladding materials under conditions representative of a light water reactor in order to validate thermo-mechanical models of stress states in these materials due to irradiation swelling and differential thermal expansion. The design allows for a constant tube outer surface temperature in the range of 300-350 °C under a representative high heat flux (∼0.66 MW/m2) during one cycle of irradiation in an un-instrumented ;rabbit; capsule in the High Flux Isotope Reactor. An engineered aluminum foil was developed to absorb the expansion of the cladding tubes, due to irradiation swelling, without changing the thermal resistance of the gap between the cladding and irradiation capsule. Finite-element analyses of the capsule were performed, and the models used to calculate thermal contact resistance were validated by out-of-pile testing and post-irradiation examination of the foils and passive SiC thermometry. Six irradiated cladding tubes (both monoliths and composites) were irradiated and subsequently disassembled in a hot cell. The calculated temperatures of passive SiC thermometry inside the capsules showed good agreement with temperatures measured post-irradiation, with two calculated temperatures falling within 10 °C of experimental measurements. The success of this design could lead to new opportunities for irradiation applications with materials that suffer from irradiation swelling, creep, or other dimensional changes that can affect the specimen temperature during irradiation.

  7. Experimental design and analysis for irradiation of SiC/SiC composite tubes under a prototypic high heat flux

    Energy Technology Data Exchange (ETDEWEB)

    Petrie, Christian M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Koyanagi, Takaaki [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); McDuffee, Joel L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Deck, Christian P. [General Atomics, San Diego, CA (United States); Katoh, Yutai [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Terrani, Kurt A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-05-04

    The purpose of this work is to design an irradiation vehicle for testing silicon carbide (SiC) fiber-reinforced SiC matrix composite cladding materials under conditions representative of a light water reactor in order to validate thermo-mechanical models of stress states in these materials due to irradiation swelling and differential thermal expansion. The design allows for a constant tube outer surface temperature in the range of 300–350 °C under a representative high heat flux (~0.66 MW/m2) during one cycle of irradiation in an un-instrumented “rabbit” capsule in the High Flux Isotope Reactor. An engineered aluminum foil was developed to absorb the expansion of the cladding tubes, due to irradiation swelling, without changing the thermal resistance of the gap between the cladding and irradiation capsule. Finite-element analyses of the capsule were performed, and the models used to calculate thermal contact resistance were validated by out-of-pile testing and post-irradiation examination of the foils and passive SiC thermometry. Six irradiated cladding tubes (both monoliths and composites) were irradiated and subsequently disassembled in a hot cell. The calculated temperatures of passive SiC thermometry inside the capsules showed good agreement with temperatures measured post-irradiation, with two calculated temperatures falling within 10 °C of experimental measurements. Furthermore, the success of this design could lead to new opportunities for irradiation applications with materials that suffer from irradiation swelling, creep, or other dimensional changes that can affect the specimen temperature during irradiation.

  8. Multifunctional Composites for Future Energy Storage in Aerospace Structures

    Directory of Open Access Journals (Sweden)

    Till Julian Adam

    2018-02-01

    Full Text Available Multifunctionalization of fiber-reinforced composites, especially by adding energy storage capabilities, is a promising approach to realize lightweight structural energy storages for future transport vehicles. Compared to conventional energy storage systems, energy density can be increased by reducing parasitic masses of non-energy-storing components and by benefitting from the composite meso- and microarchitectures. In this paper, the most relevant existing approaches towards multifunctional energy storages are reviewed and subdivided into five groups by distinguishing their degree of integration and their scale of multifunctionalization. By introducing a modified range equation for battery-powered electric aircrafts, possible range extensions enabled by multifunctionalization are estimated. Furthermore, general and aerospace specific potentials of multifunctional energy storages are discussed. Representing an intermediate degree of structural integration, experimental results for a multifunctional energy-storing glass fiber-reinforced composite based on the ceramic electrolyte Li1.4Al0.4Ti1.6(PO43 are presented. Cyclic voltammetry tests are used to characterize the double-layer behavior combined with galvanostatic charge–discharge measurements for capacitance calculation. The capacitance is observed to be unchanged after 1500 charge–discharge cycles revealing a promising potential for future applications. Furthermore, the mechanical properties are assessed by means of four-point bending and tensile tests. Additionally, the influence of mechanical loads on the electrical properties is also investigated, demonstrating the storage stability of the composites.

  9. Influence of Cutting Temperature on the Tensile Strength of a Carbon Fiber-Reinforced Polymer

    Directory of Open Access Journals (Sweden)

    Jérémy Delahaigue

    2017-12-01

    Full Text Available Carbon fiber-reinforced plastics (CFRP have seen a significant increase in use over the years thanks to their specific properties. Despite continuous improvements in the production methods of laminated parts, a trimming operation is still necessary to achieve the functional dimensions required by engineering specifications. Laminates made of carbon fibers are very abrasive and cause rapid tool wear, and require high cutting temperatures. This creates damage to the epoxy matrix, whose glass-transition temperature is often recognized to be about 180 °C. This study aims to highlight the influence of the cutting temperature generated by tool wear on the surface finish and mechanical properties obtained from tensile tests. Trimming operations were performed on a quasi-isotropic 24-ply carbon/epoxy laminate, of 3.6 mm thickness, with a 6 flutes diamond-coated (CVD cutter. The test specimens of 6 mm and 12 mm wide were obtained by trimming. The reduced width of the coupons allowed amplification of the effect of defects on the measured properties by increasing the proportion of coupon cross-section occupied by the defects. A new tool and a tool in an advanced state of wear were used to generate different cutting temperatures. Results showed a cutting temperature of 300 °C for the new tool and 475 °C for the worn tool. The analysis revealed that the specimens machined with the new tool have no thermal damage and the cut is clean. The plies oriented at −45° presented the worst surface finish according to the failure mode of the fiber. For the worn tool, the surface was degraded and the matrix was carbonized. After cutting, observations showed a degraded resin spread on the machined surface, which reduced the surface roughness and hid the cutting defects. In support of these observations, the tensile tests showed no variation of the mechanical properties for the 12 mm-wide specimens, but did show a 10% loss in mechanical properties for the 6 mm

  10. Thermal stresses in composite tubes using complementary virtual work

    Science.gov (United States)

    Hyer, M. W.; Cooper, D. E.

    1988-01-01

    This paper addresses the computation of thermally induced stresses in layered, fiber-reinforced composite tubes subjected to a circumferential gradient. The paper focuses on using the principle of complementary virtual work, in conjunction with a Ritz approximation to the stress field, to study the influence on the predicted stresses of including temperature-dependent material properties. Results indicate that the computed values of stress are sensitive to the temperature dependence of the matrix-direction compliance and matrix-direction thermal expansion in the plane of the lamina. There is less sensitivity to the temperature dependence of the other material properties.

  11. One-Year Outcomes of Total Meniscus Reconstruction Using a Novel Fiber-Reinforced Scaffold in an Ovine Model.

    Science.gov (United States)

    Patel, Jay M; Merriam, Aaron R; Culp, Brian M; Gatt, Charles J; Dunn, Michael G

    2016-04-01

    Meniscus injuries and resulting meniscectomies lead to joint deterioration, causing pain, discomfort, and instability. Tissue-engineered devices to replace the meniscus have not shown consistent success with regard to function, mechanical integrity, or protection of cartilage. To evaluate a novel resorbable polymer fiber-reinforced meniscus reconstruction scaffold in an ovine model for 52 weeks and assess its integrity, tensile and compressive mechanics, cell phenotypes, matrix organization and content, and protection of the articular cartilage surfaces. Controlled laboratory study. Eight skeletally mature ewes were implanted with the fiber-reinforced scaffold after total meniscectomy, and 2 additional animals had untreated total meniscectomies. Animals were sacrificed at 52 weeks, and the explants and articular surfaces were analyzed macroscopically. Explants were characterized by ultimate tensile testing, confined compression creep testing, and biochemical, histological, and immunohistochemical analyses. Cartilage damage was characterized using the Mankin score on histologic slides from both the femur and tibia. One sheep was removed from the study because of a torn extensor tendon; the remaining 7 explants remained fully intact and incorporated into the bone tunnels. All explants exhibited functional tensile loads, tensile stiffnesses, and compressive moduli. Fibrocartilagenous repair with both types 1 and 2 collagen were observed, with areas of matrix organization and biochemical content similar to native tissue. Narrowing in the body region was observed in 5 of 7 explants. Mankin scores showed less cartilage damage in the explant group (femoral condyle: 3.43 ± 0.79, tibial plateau: 3.50 ± 1.63) than in the meniscectomy group (femoral condyle: 8.50 ± 3.54, tibial plateau: 6.75 ± 2.47) and were comparable with Mankin scores at the previously reported 16- and 32-week time points. A resorbable fiber-reinforced meniscus scaffold supports formation of functional

  12. Glasses, ceramics, and composites from lunar materials

    Science.gov (United States)

    Beall, George H.

    1992-01-01

    A variety of useful silicate materials can be synthesized from lunar rocks and soils. The simplest to manufacture are glasses and glass-ceramics. Glass fibers can be drawn from a variety of basaltic glasses. Glass articles formed from titania-rich basalts are capable of fine-grained internal crystallization, with resulting strength and abrasion resistance allowing their wide application in construction. Specialty glass-ceramics and fiber-reinforced composites would rely on chemical separation of magnesium silicates and aluminosilicates as well as oxides titania and alumina. Polycrystalline enstatite with induced lamellar twinning has high fracture toughness, while cordierite glass-ceramics combine excellent thermal shock resistance with high flexural strengths. If sapphire or rutile whiskers can be made, composites of even better mechanical properties are envisioned.

  13. Effect of polymerization mode of two adhesive systems on push-out bond strength of fiber post to different regions of root canal dentin

    Directory of Open Access Journals (Sweden)

    Shahram Farzin Ebrahimi

    2014-01-01

    Full Text Available Background: A few studies have investigated the effect of the activation mode of adhesive systems on bond strength of fiber posts to root canal dentin. This study investigated the push-out bond strengths of a glass fiber post to different root canal regions with the use of two adhesives with light- and dual-cure polymerization modes. Materials and Methods: In this in vitro study, 40 maxillary central incisors were decoronated at cement-enamel junction with 15 ± 1 mm root length. After root canal therapy and post space preparations, they were randomly divided into four groups. Post spaces were treated with four different adhesives: Excite, Excite Dual cure Single Component (DSC, self-etch adhesive (AdheSE, and AdheSE dual-cure. Then the fiber-reinforced composite (FRC post, Postec Plus, was cemented with dual-cure resin cement, Variolink II. The roots were cut into three 2-mm-thick slices. Push-out tests were performed with a universal testing machine at a crosshead speed of 0.5 mm/min. The mode of failures was determined under a stereomicroscope. Data were analyzed by three-way analysis of variance (ANOVA and Tukey test was conducted to compare post hoc with P < 0.05 as the level of significance. Results: The highest bond strength was obtained for AdheSE dual-cure (15.54 ± 6.90 MPa and the lowest was obtained for Excite light-cure (10.07 ± 7.45 MPa and only the bond strength between these two adhesives had significant difference (P = 0.02. Bond strength decreased from the coronal to the apical in all groups and this was significant in Excite (group 1 and AdheSE (group 3 (P < 0.001. In apical regions, bond strength of dual-cure adhesives was significantly higher than light-cure adhesives (P < 0.001. Conclusion: Push-out bond strength of fiber post to different regions of root canal dentin was affected by both adhesive systems and their polymerization modes.

  14. An analytical model for shape memory alloy fiber-reinforced composite thin-walled beam undergoing large deflection

    Directory of Open Access Journals (Sweden)

    Yongsheng Ren

    2015-03-01

    Full Text Available The structural model of the thin-walled laminated beams with integral shape memory alloy active fibers and accounting for geometrically nonlinear is presented in this article. The structural modeling is split into two parts: a two-dimensional analysis over the cross section and a geometrically nonlinear analysis of a beam along the beam span. The variational asymptotic method is used to formulate the force–deformation relationship equations taking into account the presence of active shape memory alloy fibers distributed along the cross section of the beam. The geometrically nonlinear governing equations are derived using variational principle and based on the von Kármán-type nonlinear strain–displacement relations. The equations are then solved using Galerkin’s method and an incremental Newton–Raphson method. The validation for the proposed model has been carried out by comparison of the present results with those available in the literature. The results show that significant extension, bending, and twisting coupled nonlinear deflections occur during the phase transformation due to shape memory alloy actuation. The effects of the volume fraction of the shape memory alloy fiber and ply angle are also addressed.

  15. Fabrication and Evaluation of Graphite Fiber-Reinforced Polyimide Composite Tube Forms Using Modified Resin Transfer Molding

    Science.gov (United States)

    Exum, Daniel B.; Ilias, S.; Avva, V. S.; Sadler, Bob

    1997-01-01

    The techniques necessary for the fabrication of a complex three-dimensional tubular form using a PMR-type resin have been developed to allow for the construction of several tubes with good physical and mechanical properties. Employing established resin transfer molding practices, the relatively non-hazardous AMB-21 in acetone formulation was used to successfully impregnate four layers of AS4 braided graphite fiber preform previously loaded around an aluminum cylindrical core in an enclosed mold cavity. Using heat and vacuum, the solvent was evaporated to form a prepreg followed by a partial imidization and removal of condensation products. The aluminum core was replaced by a silicone rubber bladder and the cure cycle continued to the final stage of 550 F with a bladder internal pressure of 200 lbs/sq in while simultaneously applying a strong vacuum to the prepreg for removal of any additional imidization products. A combination of several modifications to the standard resin transfer molding methodology enabled the mold to 'breathe', allowing the imidization products a pathway for escape. AMB-21 resin was chosen because of the carcinogenic nature of the primary commercial polyimide PMR-15. The AMB-21 resin was formulated using commercially available monomers or monomer precursors and dissolved in a mixture of methyl alcohol and acetone. The viscosity of the resulting monomer solution was checked by use of a Brookfield rheometer and adjusted by adding acetone to an easily pumpable viscosity of about 600 cP. In addition, several types of chromatographic and thermal analyses were of the braids, and excess handling of the preforms broke some of the microscopic fibers, needlessly decreasing the strength of the finished part. In addition, three dimensional braided preforms with fibers along the length of the tube will be significantly stronger in tension than the braided preforms used in this study.

  16. Analysis of Different Positions of Fiber-Reinforced Composite Retainers versus Multistrand Wire Retainers Using the Finite Element Method

    Directory of Open Access Journals (Sweden)

    Arezoo Jahanbin

    2014-01-01

    Full Text Available Background. The aim of this study was to evaluate root displacement of the lower incisors fixed with FRC in different positions versus FSW retainers using the finite element method. Materials and Methods. 3D finite element models were designed for a mandibular anterior segment: Model 1: flexible spiral wire bonded to the lingual teeth surfaces, Model 2: FRC bonded to the upper third of lingual teeth surfaces, and Model 3: FRC bonded to the middle third. FE analysis was performed for three models and then tooth displacements were evaluated. Results. In contrast to lateral incisors and canines, the FSW retainer caused the central teeth to move more than the teeth bonded with FRC in both loadings. Comparison between Models 2 and 3 (in vertical loading showed that FRC retainers that bonded at the upper third of lingual teeth surfaces made central and canine teeth move less than FRC retainers bonded at the middle third; however, for lateral teeth it was the opposite. Conclusion. FRC retainers bonded at the upper third of lingual teeth surfaces make central and canine teeth move less than FRC retainers bonded at the middle third in vertical loading; however, for lateral teeth it was the opposite.

  17. Micromechanical Study of Interface Stress in a Fiber-Reinforced Composite under Transverse Loading Using Boundary Element Method

    National Research Council Canada - National Science Library

    Eren, Hakan

    2000-01-01

    .... The objective of this study is, by using Boundary Element Method, to examine different shapes of reinforcement elements under unit traction and unit displacement boundary conditions in transversal...

  18. Optical and mechanical excitation thermography for impact response in basalt-carbon hybrid fiber-reinforced composite laminates

    OpenAIRE

    Zhang, Hai; Sfarra, Stefano; Sarasini, Fabrizio; Ibarra-Castanedo, Clemente; Perilli, Stefano; Fernandes, Henrique; Duan, Yuxia; Peeters, Jeroen; Avelidis, Nicholas P; Maldague, Xavier

    2017-01-01

    Abstract: In this paper, optical and mechanical excitation thermography were used to investigate basalt fiber reinforced polymer (BFRP), carbon fiber reinforced polymer (CFRP) and basalt-carbon fiber hybrid specimens subjected to impact loading. Interestingly, two different hybrid structures including sandwich-like and intercalated stacking sequence were used. Pulsed phase thermography (PPT), principal component thermography (PCT) and partial least squares thermography (PLST) were used to pro...

  19. Modeling and Measurement of Sustained Loading and Temperature-Dependent Deformation of Carbon Fiber-Reinforced Polymer Bonded to Concrete.

    Science.gov (United States)

    Jeong, Yoseok; Lee, Jaeha; Kim, WooSeok

    2015-01-29

    This paper aims at presenting the effects of short-term sustained load and temperature on time-dependent deformation of carbon fiber-reinforced polymer (CFRP) bonded to concrete and pull-off strength at room temperature after the sustained loading period. The approach involves experimental and numerical analysis. Single-lap shear specimens were used to evaluate temperature and short-term sustained loading effects on time-dependent behavior under sustained loading and debonding behavior under pull-off loading after a sustained loading period. The numerical model was parameterized with experiments on the concrete, FRP, and epoxy. Good correlation was seen between the numerical results and single-lap shear experiments. Sensitivity studies shed light on the influence of temperature, epoxy modulus, and epoxy thickness on the redistribution of interfacial shear stress during sustained loading. This investigation confirms the hypothesis that interfacial stress redistribution can occur due to sustained load and elevated temperature and its effect can be significant.

  20. A new type of smart basalt fiber-reinforced polymer bars as both reinforcements and sensors for civil engineering application

    Science.gov (United States)

    Tang, Yongsheng; Wu, Zhishen; Yang, Caiqian; Wu, Gang; Shen, Sheng

    2010-11-01

    In this paper, a new type of smart basalt fiber-reinforced polymer (BFRP) bar is developed and their sensing performance is investigated by using the Brillouin scattering-based distributed fiber optic sensing technique. The industrial manufacturing process is first addressed, followed by an experimental study on the strain, temperature and fundamental mechanical properties of the BFRP bars. The results confirm the superior sensing properties, in particular the measuring accuracy, repeatability and linearity through comparing with bare optical fibers. Results on the mechanical properties show stable elastic modulus and high ultimate strength. Therefore, the smart BFRP bar has potential applications for long-term structural health monitoring (SHM) as embedded sensors as well as strengthening and upgrading structures. Moreover the coefficient of thermal expansion for smart BFRP bars is similar to the value for concrete.

  1. A new type of smart basalt fiber-reinforced polymer bars as both reinforcements and sensors for civil engineering application

    International Nuclear Information System (INIS)

    Tang, Yongsheng; Wu, Zhishen; Yang, Caiqian; Wu, Gang; Shen, Sheng

    2010-01-01

    In this paper, a new type of smart basalt fiber-reinforced polymer (BFRP) bar is developed and their sensing performance is investigated by using the Brillouin scattering-based distributed fiber optic sensing technique. The industrial manufacturing process is first addressed, followed by an experimental study on the strain, temperature and fundamental mechanical properties of the BFRP bars. The results confirm the superior sensing properties, in particular the measuring accuracy, repeatability and linearity through comparing with bare optical fibers. Results on the mechanical properties show stable elastic modulus and high ultimate strength. Therefore, the smart BFRP bar has potential applications for long-term structural health monitoring (SHM) as embedded sensors as well as strengthening and upgrading structures. Moreover the coefficient of thermal expansion for smart BFRP bars is similar to the value for concrete

  2. Development of improved asbestos reinforced phenolic insulating composites (optimization of physical properties as a function of molding technique and post cure conditions)

    Science.gov (United States)

    Hedges, L. M. (Editor)

    1973-01-01

    Detailed data are presented on phenolic-glass and phenolic-asbestos compounds which compare the effect of compression molding without degas to the effects of four variations of compression molding. These variations were designed to improve elimination of entrapped volatiles and the volatile products of the condensate reaction associated with the cure of phenolic resins. The utilization of conventional methods of degas plus degas by vacuum and directional heat flow methods are involved. Detailed data are also presented on these same compounds, comparing the effect of changes in post-bake time, and post-bake temperature for the five molding techniques.

  3. The Effect of Pre-Tension on Deformation Behaviour of Natural Fabric Reinforced Composite

    Directory of Open Access Journals (Sweden)

    Paulė BEKAMPIENĖ

    2011-03-01

    Full Text Available In the fiber-reinforced composites industry together with the promotion of environmental friendly production, synthetic materials are attempted to be replaced by renewable, biodegradable and recyclable materials. The most important challenge is to improve strength and durability of these materials. Matrix that supports the fiber-reinforcement in composite generally is brittle and deformation causes fragmentation of the matrix. Pre-tension of reinforcement is a well-known method to increase tensile strength of woven material. The current study develops the idea to use pre-tension of woven fabric in order to improve quality and strength properties of the obtained composite. Natural (cotton fiber and synthetic (glass fiber woven fabrics were investigated. The pressure forming operation was carried out in order to study clamping imposed strain variation across the surface of woven fabric. The uniaxial tension test of single-layer composite specimens with and without pre-tension was performed to study the effect of pre-tension on strength properties of composite. The results have shown that pre-tension imposed by clamping is an effective method to improve the quality of shaped composite parts (more smoothed contour is obtained and to increase the strength properties of composite reinforced by woven natural fabric. After pre-tension the tensile strength at break increased in 12 % in warp direction, in 58 % in weft direction and in 39 % in bias direction.http://dx.doi.org/10.5755/j01.ms.17.1.250

  4. RETROVIT KOLOM PENDEK BETON BERTULANG PERSEGI DENGAN PERKUATAN EKSTERNAL CARBON FIBER-REINFORCED POLYMER DI BAWAH PENGARUH PEMBEBANAN SIKLIK

    Directory of Open Access Journals (Sweden)

    Agus Sulistiawan

    2014-01-01

    Full Text Available The retrofit of non-slender square concrete column with an external strength­ener of carbon fiber-reinforced polymer (CFRP under the influence of cyclic load. The purpose of this study is to know the increase of strength and ductility of a column structure element that has an initial damage, then it is fixed and strengthened by CFRP external strengthening. The column structure element is tested by giving a constant axial load and varying the cyclic load using a displacement control. In this research, two specimens t are used, C-1 column (original column and C-1RC column (retrofit column. The results of the study show that (1 the effectiveness of the C-1CR’s restraint and moment of force are increased by 1.58 times and 52.78% compared to the C-1’s ones, and (2 the installation of CFRP reinforcement increases the strength in accepting lateral load by 52.15% and decreases of ductility by 52.12%.   Tujuan penelitian ini mengetahui peningkatan kekuatan dan daktilitas ele­men struktur kolom yang mengalami kerusakan awal, kemudian diperbaiki, dan diperkuat dengan perkuatan eksternal carbon fiber-reinforced polymer (CFRP. Pengujian ter­hadap elemen struktur kolom dilakukan dengan memberikan beban aksial yang konstan dan memvariasikan beban siklik dengan kontrol perpindahan. Dalam penelitian ini digunakan dua spesimen yaitu kolom C-1 (kolom original dan kolom C-1RC (kolom retrofit. Hasil penelitian menunjukkan (1 efektifitas pengekangan C-1CR meningkat 1,58 kali dan kekuatan terhadap momen meningkat sebesar 52,78% dibanding kolom C-1, dan (2  pemasangan perkuatan CFRP memberikan peningkatan kekuatan dalam menerima beban lateral sebesar 52,15% dan penurunan daktilitas sebesar -52,12%.

  5. Differential post-irradiation caffeine response in normal diploid versus SV40-transformed human fibroblasts: potential role of nuclear organization and protein-composition

    International Nuclear Information System (INIS)

    Taylor, Y.C.; Parsian, A.J.; Duncan, P.G.

    1993-01-01

    To test the hypothesis that the enhancement of cell killing by post-irradiation treatment with caffeine (CAF) is mediated by alterations in chromatin structure, several nuclear parameters were examined in both caffeine-responsive and non-responsive cell lines. (author)

  6. Differential post-irradiation caffeine response in normal diploid versus SV40-transformed human fibroblasts: potential role of nuclear organization and protein-composition

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Y.C.; Parsian, A.J.; Duncan, P.G. (Washington Univ., St. Louis, MO (United States). School of Medicine)

    1993-07-01

    To test the hypothesis that the enhancement of cell killing by post-irradiation treatment with caffeine (CAF) is mediated by alterations in chromatin structure, several nuclear parameters were examined in both caffeine-responsive and non-responsive cell lines. (author).

  7. SYNTHESIS AND CHARACTERIZATION OF CANNABIS INDICA FIBER REINFORCED COMPOSITES

    Directory of Open Access Journals (Sweden)

    Amar Singh Singha

    2011-04-01

    Full Text Available This paper reports on the synthesis of Cannabis indica fiber-reinforced composites using Urea-Resorcinol-Formaldehyde (URF as a novel matrix through compression molding technique. The polycondensation between urea, resorcinol, and formaldehyde in different molar ratios was applied to the synthesis of the URF polymer matrix. A thermosetting matrix based composite, reinforced with lignocellulose from Cannabis indica with different fiber loadings 10, 20, 30, 40, and 50% by weight, was obtained. The mechanical properties of randomly oriented intimately mixed fiber particle reinforced composites were determined. Effects of fiber loadings on mechanical properties such as tensile, compressive, flexural strength, and wear resistance were evaluated. Results showed that mechanical properties of URF resin matrix increased considerably when reinforced with particles of Cannabis indica fiber. Thermal (TGA/DTA/DTG and morphological studies (SEM of the resin, fiber and polymer composite thus synthesized were carried out.

  8. Pedicle screw anchorage of carbon fiber-reinforced PEEK screws under cyclic loading.

    Science.gov (United States)

    Lindtner, Richard A; Schmid, Rene; Nydegger, Thomas; Konschake, Marko; Schmoelz, Werner

    2018-03-01

    Pedicle screw loosening is a common and significant complication after posterior spinal instrumentation, particularly in osteoporosis. Radiolucent carbon fiber-reinforced polyetheretherketone (CF/PEEK) pedicle screws have been developed recently to overcome drawbacks of conventional metallic screws, such as metal-induced imaging artifacts and interference with postoperative radiotherapy. Beyond radiolucency, CF/PEEK may also be advantageous over standard titanium in terms of pedicle screw loosening due to its unique material properties. However, screw anchorage and loosening of CF/PEEK pedicle screws have not been evaluated yet. The aim of this biomechanical study therefore was to evaluate whether the use of this alternative nonmetallic pedicle screw material affects screw loosening. The hypotheses tested were that (1) nonmetallic CF/PEEK pedicle screws resist an equal or higher number of load cycles until loosening than standard titanium screws and that (2) PMMA cement augmentation further increases the number of load cycles until loosening of CF/PEEK screws. In the first part of the study, left and right pedicles of ten cadaveric lumbar vertebrae (BMD 70.8 mg/cm 3  ± 14.5) were randomly instrumented with either CF/PEEK or standard titanium pedicle screws. In the second part, left and right pedicles of ten vertebrae (BMD 56.3 mg/cm 3  ± 15.8) were randomly instrumented with either PMMA-augmented or nonaugmented CF/PEEK pedicle screws. Each pedicle screw was subjected to cyclic cranio-caudal loading (initial load ranging from - 50 N to + 50 N) with stepwise increasing compressive loads (5 N every 100 cycles) until loosening or a maximum of 10,000 cycles. Angular screw motion ("screw toggling") within the vertebra was measured with a 3D motion analysis system every 100 cycles and by stress fluoroscopy every 500 cycles. The nonmetallic CF/PEEK pedicle screws resisted a similar number of load cycles until loosening as the contralateral standard

  9. Requirements of frictional debonding at fiber/matrix interfaces for tough ceramic composites

    Science.gov (United States)

    Hsueh, Chun-Hway

    1992-11-01

    Optimum toughening of fiber-reinforced ceramic composites requires debonding at fiber/matrix interfaces and subsequent frictional sliding between the fibers and the matrix as the main crack extends through the composite. Criteria of both interfacial debonding vs fiber fracture, and frictional debonding vs frictionless debonding, are illustrated. To achieve interfacial debonding, the ratio of the fiber strength to the interfacial shear strength must exceed a critical value; to achieve a frictional interface after interfacial debonding, the ratio of the interfacial residual clamping stress to the interfacial shear strength must also exceed a critical value. While interfacial debonding is not sensitive to Poisson's effect, the frictional interface is sensitive to Poisson's effect.

  10. Effect of montmorillonite clay on flax fabric reinforced poly lactic acid composites with amphiphilic additives

    CSIR Research Space (South Africa)

    Kumar, R

    2010-01-01

    Full Text Available 5083263; fax: +27 41 5832325. Composites: Part A xxx (2010) xxx–xxx Contents lists availabl tes ev E-mail address: krrakesh72@gmail.com (R. Kumar). strength and stiffness, dimensional stability, and thermal proper- ties [1]. But finite nature.... Chemical treatments of natural fiber for use in natural fiber-reinforced composites: a review. J Polym Environ 2007;15:25–33. [15] Pothan LA, Thomas S, Groeninckx G. The role of fibre/matrix interactions on the dynamic mechanical properties...

  11. Long-Term Durability of Basalt Fiber-Reinforced Polymer (BFRP Sheets and the Epoxy Resin Matrix under a Wet–Dry Cyclic Condition in a Chloride-Containing Environment

    Directory of Open Access Journals (Sweden)

    Zhongyu Lu

    2017-11-01

    Full Text Available Basalt fiber-reinforced polymer (BFRP composites are receiving increasing attention as they represent a low-cost green source of raw materials. FRP composites have to face harsh environments, such as chloride ions in coastal marine environments or cold regions with salt deicing. The resistance of FRPs subjected to the above environments is critical for the safe design and application of BFRP composites. In the present paper, the long-term durability of BFRP sheets and the epoxy resin matrix in a wet–dry cyclic environment containing chloride ions was studied. The specimens of the BFRP sheet and epoxy resin matrix were exposed to alternative conditions of 8-h immersion in 3.5% NaCl solution at 40 °C and 16-h drying at 25 °C and 60% relative humidity (RH. The specimens were removed from the exposure chamber at the end of the 180th, 270th and 360th cycles of exposure and were analyzed for degradation with tensile tests, scanning electron microscopy (SEM and void volume fractions. It was found that the tensile modulus of the BFRP sheet increased by 3.4%, and the tensile strength and ultimate strain decreased by 45% and 65%, respectively, after the 360th cycle of exposure. For the epoxy resin matrix, the tensile strength, tensile modulus and ultimate strain decreased by 27.8%, 3.2% and 64.8% after the 360th cycle of exposure, respectively. The results indicated that the degradation of the BFRP sheet was dominated by the damage of the interface between the basalt fiber and epoxy resin matrix. In addition, salt precipitate accelerated the fiber–matrix interfacial debonding, and hydrolysis of the epoxy resin matrix resulted in many voids, which accelerated the degradation of the BFRP sheet.

  12. Physicochemical properties of discontinuous S2-glass fiber reinforced resin composite.

    Science.gov (United States)

    Huang, Qiting; Qin, Wei; Garoushi, Sufyan; He, Jingwei; Lin, Zhengmei; Liu, Fang; Vallittu, Pekka K; Lassila, Lippo V J

    2018-01-30

    The objective of this study was to investigate several physicochemical properties of an experimental discontinuous S2-glass fiber-reinforced resin composite. The experimental composite was prepared by mixing 10 wt% of discontinuous S2-glass fibers with 27.5 wt% of resin matrix and 62.5 wt% of particulate fillers. Flexural strength (FS) and modulus (FM), fracture toughness (FT), work of fracture (WOF), double bond conversion (DC), Vickers hardness, volume shrinkage (VS) and fiber length distribution were determined. These were compared with two commercial resin composites. The experimental composite showed the highest FS, WOF and FT compared with two control composites. The DC of the experimental composite was comparable with controls. No significant difference was observed in VS between the three tested composites. The use of discontinuous glass fiber fillers with polymer matrix and particulate fillers yielded improved physical properties and substantial improvement was associated with the use of S2-glass fiber.

  13. Genotype x prenatal and post-weaning nutritional environment interaction in a composite beef cattle breed using reaction norms and multi-trait model

    Science.gov (United States)

    Environmental effects have been shown to influence several economically important traits in beef cattle. In this study, genetic x nutritional environment interaction has been evaluated in a composite beef cattle breed (50% Red Angus, 25% Charolais, 25% Tarentaise). Four nutritional environments (MAR...

  14. Writing Critical Race Theory and Method: A Composite Counterstory on the Experiences of Black Teachers in New Orleans Post-Katrina

    Science.gov (United States)

    Cook, Daniella Ann; Dixson, Adrienne D.

    2013-01-01

    Using a critical race theory lens, the authors propose a way of writing race research using composite counterstories. Drawing on data from a yearlong study of school rebuilding in the time period immediately after Hurricane Katrina devastated the City of New Orleans, the authors examine the experiences of African-American educators in the school…

  15. Fiber glass-bioactive glass composite for bone replacing and bone anchoring implants.

    Science.gov (United States)

    Vallittu, Pekka K; Närhi, Timo O; Hupa, Leena

    2015-04-01

    Although metal implants have successfully been used for decades, devices made out of metals do not meet all clinical requirements, for example, metal objects may interfere with some new medical imaging systems, while their stiffness also differs from natural bone and may cause stress-shielding and over-loading of bone. Peer-review articles and other scientific literature were reviewed for providing up-dated information how fiber-reinforced composites and bioactive glass can be utilized in implantology. There has been a lot of development in the field of composite material research, which has focused to a large extent on biodegradable composites. However, it has become evident that biostable composites may also have several clinical benefits. Fiber reinforced composites containing bioactive glasses are relatively new types of biomaterials in the field of implantology. Biostable glass fibers are responsible for the load-bearing capacity of the implant, while the dissolution of the bioactive glass particles supports bone bonding and provides antimicrobial properties for the implant. These kinds of combination materials have been used clinically in cranioplasty implants and they have been investigated also as oral and orthopedic implants. The present knowledge suggests that by combining glass fiber-reinforced composite with particles of bioactive glass can be used in cranial implants and that the combination of materials may have potential use also as other types of bone replacing and repairing implants. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  16. The effect of litter quality and soil faunal composition on organic matter dynamics in post-mining soil: A laboratory study

    Czech Academy of Sciences Publication Activity Database

    Frouz, Jan; Elhottová, Dana; Pižl, Václav; Tajovský, Karel; Šourková, Monika; Picek, T.; Malý, S.

    2007-01-01

    Roč. 37, 1/2 (2007), s. 72-80 ISSN 0929-1393 R&D Projects: GA AV ČR 1QS600660505; GA ČR GA526/01/1055; GA ČR GA526/03/1259; GA MŠk LC06066 Institutional research plan: CEZ:AV0Z60660521 Keywords : earthworms * carbon sequestration * disturbed post-mining habitat Subject RIV: EH - Ecology, Behaviour Impact factor: 1.810, year: 2007

  17. Composite materials. Volume 3 - Engineering applications of composites. Volume 4 - Metallic matrix composites. Volume 8 - Structural design and analysis, Part 2

    Science.gov (United States)

    Noton, B. R. (Editor); Kreider, K. G.; Chamis, C. C.

    1974-01-01

    This volume discusses a vaety of applications of both low- and high-cost composite materials in a number of selected engineering fields. The text stresses the use of fiber-reinforced composites, along with interesting material systems used in the electrical and nuclear industries. As to technology transfer, a similarity is noted between many of the reasons responsible for the utilization of composites and those problems requiring urgent solution, such as mechanized fabrication processes and design for production. Features topics include road transportation, rail transportation, civil aircraft, space vehicles, builing industry, chemical plants, and appliances and equipment. The laminate orientation code devised by Air Force materials laboratory is included. Individual items are announced in this issue.

  18. Modelling of the glass fiber length and the glass fiber length distribution in the compounding of short glass fiber-reinforced thermoplastics

    Science.gov (United States)

    Kloke, P.; Herken, T.; Schöppner, V.; Rudloff, J.; Kretschmer, K.; Heidemeyer, P.; Bastian, M.; Walther, Dridger, A.

    2014-05-01

    The use of short glass fiber-reinforced thermoplastics for the production of highly stressed parts in the plastics processing industry has experienced an enormous boom in the last few years. The reasons for this are primarily the improvements to the stiffness and strength properties brought about by fiber reinforcement. These positive characteristics of glass fiber-reinforced polymers are governed predominantly by the mean glass fiber length and the glass fiber length distribution. It is not enough to describe the properties of a plastics component solely as a function of the mean glass fiber length [1]. For this reason, a mathematical-physical model has been developed for describing the glass fiber length distribution in compounding. With this model, it is possible on the one hand to optimize processes for the production of short glass fiber-reinforced thermoplastics, and, on the other, to obtain information on the final distribution, on the basis of which much more detailed statements can be made about the subsequent properties of the molded part. Based on experimental tests, it was shown that this model is able to accurately describe the change in glass fiber length distribution in compounding.

  19. KevlarTM Fiber-Reinforced Polybenzoxazine Alloys for Ballistic Impact Application

    Directory of Open Access Journals (Sweden)

    Chanchira Jubsilp

    2011-10-01

    Full Text Available A light weight ballistic composites from KevlarTM-reinforcing fiber having polybenzoxazine (BA/urethane prepolymer (PU alloys as a matrix were investigated in this work. The effect of alloy compositions on the ballistic composite properties was determined. The results revealed that the enhancement in the glass transition temperature (Tg of the KevlarTM-reinforced BA/PU composites compared to that of the KevlarTM-reinforced polybenzoxazine composite was observed. The increase of the elastomeric PU content in the BA/PU alloy resulted in samples with tougher characteristics. The storage modulus of the KevlarTM-reinforced BA/PU composites increased with increasing the mass fraction of polybenzoxazine. A ballistic impact test was also performed on the KevlarTM-reinforced BA/PU composites using a 9 mm handgun. It was found that the optimal contents of PU in the BA/PU alloys should be approximately 20wt%. The extent of the delaminated area and interfacial fracture were observed to change with the varied compositions of the matrix alloys. The appropriate thickness of KevlarTM-reinforced 80/20 BA/PU composite panel was 30 plies and 50 plies to resist the penetration from the ballistic impact equivalent to levels II-A and III-A of NIJ standard. The arrangement of composite panels with the higher stiffness panel at the front side also showed the best efficiency of ballistic penetration resistance.

  20. Temporal dynamics of the compositions and activities of soil microbial communities post-application of the insecticide chlorantraniliprole in paddy soils.

    Science.gov (United States)

    Wu, Meng; Liu, Jia; Li, Weitao; Liu, Ming; Jiang, Chunyu; Li, Zhongpei

    2017-10-01

    Chlorantraniliprole (CAP) is a newly developed insecticide widely used in rice fields in China. There has been few studies evaluating the toxicological effects of CAP on soil-associated microbes. An 85-day microcosm experiment was performed to reveal the dissipation dynamics of CAP in three types of paddy soils in subtropical China. The effects of CAP on microbial activities (microbial biomass carbon-MBC, basal soil respiration-BSR, microbial metabolic quotient-qCO 2 , acid phosphatase and sucrose invertase activities) in the soils were periodically evaluated. Microbial phospholipid fatty acid (PLFA) analysis was used to evaluate the change of soil microbial community composition on day 14 and 50 of the experiment. CAP residues were extracted using the quick, easy, cheap, effective, rugged, and safe (QuChERS) method and quantification was measured by high performance liquid chromatography (HPLC). The half-lives (DT 50 ) of CAP were in the range of 41.0-53.0 days in the three soils. The results showed that CAP did not impart negative effects on MBC during the incubation. CAP inhibited BSR, qCO 2 , acid phosphatase and sucrose invertase activities in the first 14 days of incubation in all the soils. After day 14, the soil microbial parameters of CAP-treated soils became statistically at par with their controls. Principal component analysis (PCA) determining abundance of biomarker PLFAs indicated that the application of CAP significantly changed the compositions of microbial communities in all three paddy soils on day 14 but the compositions of soil microbial communities recovered by day 50. This study indicates that CAP does not ultimately impair microbial activities and microbial compositions of these three paddy soil types. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Electron beam curing of composites in North America

    International Nuclear Information System (INIS)

    Berejka, Anthony J.; Eberle, Cliff

    2002-01-01

    Electron beam curing of fiber-reinforced composites was explored over 30 years ago. Since then there have been developments in accelerator technology, in processes for handling materials presented to an accelerator, and in materials that can be used as matrix binders. In recent years in North America, Cooperative Research and Development Agreements (CRADAs) have been formed involving collaboration amongst materials suppliers, accelerator manufacturers and service providers, national laboratories, such as Oak Ridge National Laboratory, and interested potential users. The scope and status of these CRADAs are reviewed along with other recent developments in the electron beam curing of composites in North America. Innovative and proprietary materials technology has been developed and progress made toward implementing commercial practice. Significant market interest has developed in the military/aerospace industries that are finding the process and performance of electron beam cured composites to offer significant benefits

  2. Carbon fiber/carbon nanotube reinforced hierarchical composites: Effect of CNT distribution on shearing strength

    DEFF Research Database (Denmark)

    Zhou, H. W.; Mishnaevsky, Leon; Yi, H. Y.

    2016-01-01

    The strength and fracture behavior of carbon fiber reinforced polymer composites with carbon nanotube (CNT) secondary reinforcement are investigated experimentally and numerically. Short Beam Shearing tests have been carried out, with SEM observations of the damage evolution in the composites. 3D...... CNT nanoreinforcement into the matrix and/or the sizing of carbon fiber/reinforced composites ensures strong increase of the composite strength. The effect of secondary CNTs reinforcement is strongest when some small addition of CNTs in the polymer matrix is complemented by the fiber sizing with high...... multiscale computational (FE) models of the carbon/polymer composite with varied CNT distributions have been developed and employed to study the effect of the secondary CNT reinforcement, its distribution and content on the strength and fracture behavior of the composites. It is shown that adding secondary...

  3. Fracture Toughness of Carbon Nanotube-Reinforced Metal- and Ceramic-Matrix Composites

    International Nuclear Information System (INIS)

    Chen, Y.L.; Liu, B.; Hwang, K.C.; Chen, Y.L.; Huang, Y.

    2011-01-01

    Hierarchical analysis of the fracture toughness enhancement of carbon nanotube- (CNT-) reinforced hard matrix composites is carried out on the basis of shear-lag theory and fracture mechanics. It is found that stronger CNT/matrix interfaces cannot definitely lead to the better fracture toughness of these composites, and the optimal interfacial chemical bond density is that making the failure mode just in the transition from CNT pull-out to CNT break. For hard matrix composites, the fracture toughness of composites with weak interfaces can be improved effectively by increasing the CNT length. However, for soft matrix composite, the fracture toughness improvement due to the reinforcing CNTs quickly becomes saturated with an increase in CNT length. The proposed theoretical model is also applicable to short fiber-reinforced composites.

  4. Fracture Toughness of Carbon Nanotube-Reinforced Metal- and Ceramic-Matrix Composites

    Directory of Open Access Journals (Sweden)

    Y. L. Chen

    2011-01-01

    Full Text Available Hierarchical analysis of the fracture toughness enhancement of carbon nanotube- (CNT- reinforced hard matrix composites is carried out on the basis of shear-lag theory and facture mechanics. It is found that stronger CNT/matrix interfaces cannot definitely lead to the better fracture toughness of these composites, and the optimal interfacial chemical bond density is that making the failure mode just in the transition from CNT pull-out to CNT break. For hard matrix composites, the fracture toughness of composites with weak interfaces can be improved effectively by increasing the CNT length. However, for soft matrix composite, the fracture toughness improvement due to the reinforcing CNTs quickly becomes saturated with an increase in CNT length. The proposed theoretical model is also applicable to short fiber-reinforced composites.

  5. Fracture behavior of C/SiC composites at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Dong Hyun; Lee, Jeong Won; Kim, Jae Hoon; Shin, Ihn Cheol; Lim, Byung Joo [Chungnam National University, Daejeon (Korea, Republic of)

    2017-08-15

    The fracture behavior of carbon fiber-reinforced silicon carbide (C/SiC) composites used in rocket nozzles has been investigated under tension, compression, and fracture conditions at room temperature, 773 K and 1173 K. The C/SiC composites used in this study were manufactured by liquid silicon infiltration process at ~1723 K. All experiments were conducted using two types of specimens, considering fiber direction and oxidation condition. Experimental results show that temperature, fiber direction, and oxidation condition affect the behavior of C/SiC composites. Oxidation was found to be the main factor that changes the strength of C/SiC composites. By applying an anti-oxidation coating, the tensile and compressive strengths of the C/SiC composites increased with temperature. The fracture toughness of the C/SiC composites also increased with increase temperature. A fractography analysis of the fractured specimens was conducted using a scanning electron microscope.

  6. Effect of preceramic and Zr coating on impregnation behaviors of SiC ceramic composite

    Science.gov (United States)

    Jung, Yang-Il; Kim, Sun-Han; Kim, Hyun-Gil; Park, Jeong-Yong; Koo, Yang-Hyun

    2015-01-01

    SiC fiber-reinforced ceramic composites were fabricated using a polymer impregnation and pyrolysis process. To develop the low temperature process, the pyrolysis was conducted at 600 °C in air. Both a microstructural observation and a mechanical test were utilized for the evaluation of the impregnation. For the impregnation, two kinds of polycarbosilane having a different degree of cross-linking were used. The level of cross-linking affected the ceramic yield of the composites. The cross-linking under oxygen containing atmosphere resulted in a dense matrix and high density of filling. However, tight bonding between the matrix and fibers in the fully dense composite samples, which was obtained using a cross-linking agent of divinylbenzene, turned out to be deteriorative on the mechanical properties. The physical isolation of fibers from matrix phase in the composites was very important to attain a mechanical ductility. The brittle fracture was alleviated by introducing an interphase coating with metallic Zr. The combination of forming the dense matrix and interphase coating should be a necessary condition for the SiCf/SiC fiber-reinforce composite, and it is practicable by controlling the process parameters.

  7. Effective properties of dispersed phase reinforced composite materials with perfect and imperfect interfaces

    Science.gov (United States)

    Han, Ru

    This thesis focuses on the analysis of dispersed phase reinforced composite materials with perfect as well as imperfect interfaces using the Boundary Element Method (BEM). Two problems of interest are considered, namely, to determine the limitations in the use of effective properties and the analysis of failure progression at the inclusion-matrix interface. The effective moduli (effective Young's modulus, effective Poisson's ratio, effective shear modulus, and effective bulk modulus) of composite materials can be determined at the mesoscopic level using three-dimensional parallel BEM simulations. By comparing the mesoscopic BEM results and the macroscopic results based on effective properties, limitations in the effective property approach can be determined. Decohesion is an important failure mode associated with fiber-reinforced composite materials. Analysis of failure progression at the fiber-matrix interface in fiber-reinforced composite materials is considered using a softening decohesion model consistent with thermodynamic concepts. In this model, the initiation of failure is given directly by a failure criterion. Damage is interpreted by the development of a discontinuity of displacement. The formulation describing the potential development of damage is governed by a discrete decohesive constitutive equation. Numerical simulations are performed using the direct boundary element method. Incremental decohesion simulations illustrate the progressive evolution of debonding zones and the propagation of cracks along the interfaces. The effect of decohesion on the macroscopic response of composite materials is also investigated.

  8. Does the adhesive strategy influence the post-operative sensitivity in adult patients with posterior resin composite restorations?: A systematic review and meta-analysis.

    Science.gov (United States)

    Reis, Alessandra; Dourado Loguercio, Alessandro; Schroeder, Marcos; Luque-Martinez, Issis; Masterson, Danielle; Cople Maia, Lucianne

    2015-09-01

    A systematic review and meta-analysis were performed on the risk and intensity of postoperative sensitivity (POS) in posterior resin composite restorations bonded with self-etch (SE) and etch-and-rinse (ER) adhesives. A comprehensive search was performed in the MEDLINE via PubMeb, Scopus, Web of Science, LILACS, BBO and Cochrane Library and SIGLE without restrictions. The abstracts of the annual conference of the IADR (1990-2014), unpublished and ongoing trials registry were also searched. Dissertations and theses were searched using the ProQuest Dissertations and Periodicos Capes Theses databases. We included randomized clinical trials that compared the clinical effectiveness of SE and ER used for direct resin composite restorations in permanent dentition of adult patients. The risk/intensity of POS was the primary outcome. The risk of bias tool of the Cochrane Collaboration was used. The meta-analysis was performed on the studies considered 'low' risk of bias. After duplicates removal, 2600 articles were identified but only 29 remained in the qualitative synthesis. Five were considered to be 'high' risk of bias and eleven were considered to be 'unclear' in the key domains, yielding 13 studies for meta-analysis. The overall relative risk of the spontaneous POS was 0.63 (95% CI 0.35 to 1.15), while the stimuli-induced POS was 0.99 (95% CI 0.63 to 1.56). The overall standardized mean difference was 0.08 (95%CI -0.19 to 0.35). No overall effect was revealed in the meta-analyses, meaning that no influence of the ER or SE strategy on POS. The type of adhesive strategy (ER or SE) for posterior resin composite restorations does not influence the risk and intensity of POS. CRD42014006617. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  9. Post-processor for simulations of the ORIGEN program and calculation of the composition of the activity of a burnt fuel core by a BWR type reactor; Post-procesador para simulaciones del programa ORIGEN y calculo de la composicion de la actividad de un nucleo de combustible quemado por un reactor tipo BWR

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval V, S. [IIE, Av. Reforma 113, Col. Palmira, 62490 Cuernavaca, Morelos (Mexico)]. e-mail: sandoval@iie.org.mx

    2006-07-01

    The composition calculation and the activity of nuclear materials subject to processes of burnt, irradiation and decay periods are of utility for diverse activities inside the nuclear industry, as they are it: the processes design and operations that manage radioactive material, the calculation of the inventory and activity of a core of burnt nuclear fuel, for studies of type Probabilistic Safety Analysis (APS), as well as for regulation processes and licensing of nuclear facilities. ORIGEN is a program for computer that calculates the composition and the activity of nuclear materials subject to periods of burnt, irradiation and decay. ORIGEN generates a great quantity of information whose processing and analysis are laborious, and it requires thoroughness to avoid errors. The automation of the extraction, conditioning and classification of that information is of great utility for the analyst. By means of the use of the post-processor presented in this work it is facilitated, it speeds up and wide the capacity of analysis of results, since diverse consultations with several classification options and filtrate of results can be made. As illustration of the utility of the post-processor, and as an analysis of interest for itself, it is also presented in this work the composition of the activity of a burned core in a BWR type reactor according to the following classification criteria: by type of radioisotope (fission products, activation products and actinides), by specie type (gassy, volatile, semi-volatile and not volatile), by element and by chemical group. The results show that the total activity of the studied core is dominated by the fission products and for the actinides, in proportion four to one, and that the gassy and volatile species conform a fifth part of the total activity of the core. (Author)

  10. A national environmental/energy workforce assessment. Post-secondary education profile: composite i (environmental engineering/health). Final report on phase 2

    International Nuclear Information System (INIS)

    1978-12-01

    This study is one of 16 volumes aggregating data on representative environmental education offerings in the United States at post-secondary education institutions and in the private sector of the economy. Structured around on-site interviews, the study describes the institutions' education programs--their program structure, representative course offerings, faculty structure, and program requirements. In addition, the study provides information on the employment history of graduates. Designed as Phase II of a three-phase program, the study presents the information on schools with emphasis on environmental engineering/health. The study is an overview. It doesn't include all environmental programs in the United States, and it makes no attempt to evaluate the program offerings

  11. A national environmental/energy workforce assessment. Post-secondary education profile: composite ii (education/ecology). Final report on phase 2

    International Nuclear Information System (INIS)

    1978-12-01

    This study is one of 16 volumes aggregating data on representative environmental education offerings in the United States at post-secondary education institutions and in the private sector of the economy. Structured around on-site interviews, the study describes the institutions' education programs--their program structure, representative course offerings, faculty structure, and program requirements. In addition, the study provides information on the employment history of graduates. Designed as Phase II of a three-phase program, the study presents the information on schools with emphasis on education/ecology. The study is an overview. It doesn't include all environmental programs in the United States, and it makes no attempt to evaluate the program offerings

  12. The Effect of Thermooxidative Aging on the Durability of Glass Fiber-Reinforced Epoxy

    Directory of Open Access Journals (Sweden)

    Amin Khajeh

    2015-01-01

    Full Text Available Thin-skinned organic matrix composites within aeronautical structures are subjected to thermooxidative aging during their service life, leading to reductions in their durability. In this paper, a durability evaluation of fiberglass epoxy prepreg is performed on the original composite thickness before and after 800 h isothermal aging at 82°C. The characterization of both aged and unaged composites comprised tensile tests, DMA, FTIR, weight loss measurements, SEM, and DSC. The tensile strength and modulus of the composites increased after being exposed to pronounced aging conditions, whereas a decrease was observed in the toughness. DMA results revealed that the glass transition temperature and rubbery state modulus increased as a result of the thermooxidative aging. FTIR spectroscopy demonstrated the formation of carbonyl compounds due to oxidation of the chemical structure of the resin. SEM observations indicated the existence of minor superficial cracking and poor fiber-matrix adhesion after aging. In addition, a minor mass change was observed from mass loss monitoring methods. The overall findings suggest that postcuring and physical aging enhanced the brittleness of the resin, leading to a significant decline in the useful structural life of the thin-skinned composite.

  13. Micromechanical performance of interfacial transition zone in fiber-reinforced cement matrix

    Science.gov (United States)

    Zacharda, V.; Němeček, J.; Štemberk, P.

    2017-09-01

    The paper investigates microstructure, chemical composition and micromechanical behavior of an interfacial transition zone (ITZ) in steel fiber reinforced cement matrix. For this goal, a combination of scanning electron microscopy (SEM), nanoindentation and elastic homogenization theory are used. The investigated sample of cement paste with dispersed reinforcement consists of cement CEM I 42,5R and a steel fiber TriTreg 50 mm. The microscopy revealed smaller portion of clinkers and larger porosity in the ITZ. Nanoindentation delivered decreased elastic modulus in comparison with cement bulk (67%) and the width of ITZ (∼ 40 μm). The measured properties served as input parameters for a simple two-scale model for elastic properties of the composite. Although, no major influence of ITZ properties on the composite elastic behavior was found, the findings about the ITZ reduced properties and its size can serve as input to other microstructural fracture based models.

  14. Characteristics of hot-pressed fiber-reinforced ceramics with SiC matrix

    Science.gov (United States)

    Miyoshi, Tadahiko; Kodama, Hironori; Sakamoto, Hiroshi; Goto, Akihiro; Iijima, Shiroo

    1989-11-01

    Silicon carbide ceramics’ matrix composites with SiC or C filaments were fabricated through hot pressing, and the effects of the filament pullout on their fracture toughness were experimentally investigated. The C-rich coating layers on the SiC filaments were found to have a significant effect on the frictional stress at the filament/matrix interfaces, through assising the filamet pullout from the matrix. Although the coating layers were apt to burn out in the sintering process of SiC matrix compposites, a small addition of carbon to the raw materials was found to be effective for the retention of the layers on the fibers, thus increasing the fracture toughness of the composites. The fracture toughness of the C filament/SiC matrix composite increased with temperature due to the larger interfacial frictional stress at higher temperatures, because of the higher thermal expansion of the filament in the radial direction than that of the matrix.

  15. The influence of surface microstructure and chemical composition on corrosion behaviour in fuel-grade bio-ethanol of low-alloy steel modified by plasma nitro-carburizing and post-oxidizing

    Science.gov (United States)

    Boniatti, Rosiana; Bandeira, Aline L.; Crespi, Ângela E.; Aguzzoli, Cesar; Baumvol, Israel J. R.; Figueroa, Carlos A.

    2013-09-01

    The interaction of bio-ethanol on steel surfaces modified by plasma-assisted diffusion technologies is studied for the first time. The influence of surface microstructure and chemical composition on corrosion behaviour of AISI 4140 low-alloy steel in fuel-grade bio-ethanol was investigated. The steel surfaces were modified by plasma nitro-carburizing followed plasma oxidizing. X-ray diffraction, scanning electron microscopy, optical microscopy, X-ray dispersive spectroscopy, and glow-discharge optical emission spectroscopy were used to characterize the modified surface before and after immersion tests in bio-ethanol up to 77 days. The main corrosion mechanism is pit formation. The pit density and pit size were measured in order to quantify the corrosion resistance which was found to depend more strongly on microstructure and morphology of the oxide layer than on its thickness. The best corrosion protection was observed for samples post-oxidized at 480 °C and 90 min.

  16. The influence of surface microstructure and chemical composition on corrosion behaviour in fuel-grade bio-ethanol of low-alloy steel modified by plasma nitro-carburizing and post-oxidizing

    International Nuclear Information System (INIS)

    Boniatti, Rosiana; Bandeira, Aline L.; Crespi, Ângela E.; Aguzzoli, Cesar; Baumvol, Israel J.R.; Figueroa, Carlos A.

    2013-01-01

    The interaction of bio-ethanol on steel surfaces modified by plasma-assisted diffusion technologies is studied for the first time. The influence of surface microstructure and chemical composition on corrosion behaviour of AISI 4140 low-alloy steel in fuel-grade bio-ethanol was investigated. The steel surfaces were modified by plasma nitro-carburizing followed plasma oxidizing. X-ray diffraction, scanning electron microscopy, optical microscopy, X-ray dispersive spectroscopy, and glow-discharge optical emission spectroscopy were used to characterize the modified surface before and after immersion tests in bio-ethanol up to 77 days. The main corrosion mechanism is pit formation. The pit density and pit size were measured in order to quantify the corrosion resistance which was found to depend more strongly on microstructure and morphology of the oxide layer than on its thickness. The best corrosion protection was observed for samples post-oxidized at 480 °C and 90 min.

  17. A composite indicator to measure universal health care coverage in India: way forward for post-2015 health system performance monitoring framework.

    Science.gov (United States)

    Prinja, Shankar; Gupta, Rakesh; Bahuguna, Pankaj; Sharma, Atul; Kumar Aggarwal, Arun; Phogat, Amit; Kumar, Rajesh

    2017-02-01

    There is limited work done on developing methods for measurement of universal health coverage. We undertook a study to develop a methodology and demonstrate the practical application of empirically measuring the extent of universal health coverage at district level. Additionally, we also develop a composite indicator to measure UHC. A cross-sectional survey was undertaken among 51 656 households across 21 districts of Haryana state in India. Using the WHO framework for UHC, we identified indicators of service coverage, financial risk protection, equity and quality based on the Government of India and the Haryana Government's proposed UHC benefit package. Geometric mean approach was used to compute a composite UHC index (CUHCI). Various statistical approaches to aggregate input indicators with or without weighting, along with various incremental combinations of input indicators were tested in a comprehensive sensitivity analysis. The population coverage for preventive and curative services is presented. Adjusting for inequality, the coverage for all the indicators were less than the unadjusted coverage by 0.1-6.7% in absolute term and 0.1-27% in relative term. There was low unmet need for curative care. However, about 11% outpatient consultations were from unqualified providers. About 30% households incurred catastrophic health expenditures, which rose to 38% among the poorest 20% population. Summary index (CUHCI) for UHC varied from 12% in Mewat district to 71% in Kurukshetra district. The inequality unadjusted coverage for UHC correlates highly with adjusted coverage. Our paper is an attempt to develop a methodology to measure UHC. However, careful inclusion of others indicators of service coverage is recommended for a comprehensive measurement which captures the spirit of universality. Further, more work needs to be done to incorporate quality in the measurement framework. © The Author 2016. Published by Oxford University Press in association with The London

  18. La Poste

    CERN Multimedia

    2004-01-01

    http://www.cern.ch/cern50/ The French Post Office has issued ten commemorative envelopes bearing original images depicting CERN and its history. This special fiftieth anniversary collector's edition will be available on the French Post Office (« La Poste ») stand at the Open Day on 16 October, in the CMS experiment hall at Cessy. Information for collectors: a pictorial postmark and date stamp have been specially designed and produced for the occasion with the assistance of CERN's graphics team. Sending a philatelic souvenir is a great way to commemorate the Open Day, so La Poste will be setting up a large post-box for that very purpose next to its stand. A perfect way to send images of CERN all around the world...

  19. Measurement of Three-Dimensional Anisotropic Thermal Diffusivities for Carbon Fiber-Reinforced Plastics Using Lock-In Thermography

    Science.gov (United States)

    Ishizaki, Takuya; Nagano, Hosei

    2015-11-01

    A new measurement technique to measure the in-plane thermal diffusivity, the distribution of in-plane anisotropy, and the out-of-plane thermal diffusivity has been developed to evaluate the thermal conductivity of anisotropic materials such as carbon fiber-reinforced plastics (CFRPs). The measurements were conducted by using a laser-spot-periodic-heating method. The temperature of the sample is detected by using lock-in thermography. Thermography can analyze the phase difference between the periodic heat input and the temperature response of the sample. Two kinds of samples, unidirectional (UD) and cross-ply (CP) pitch-based CFRPs, were fabricated and tested in an atmospheric condition. All carbon fibers of the UD sample run in one direction [90°]. The carbon fibers of the CP sample run in two directions [0°/90°]. It is found that, by using lock-in thermography, it is able to visualize the thermal anisotropy and calculate the angular dependence of the in-plane thermal diffusivity of the CFRPs. The out-of-plane thermal diffusivity of CFRPs was also measured by analyzing the frequency dependence of the phase difference.

  20. Electrical and Self-Sensing Properties of Ultra-High-Performance Fiber-Reinforced Concrete with Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Ilhwan You

    2017-10-01

    Full Text Available This study examined the electrical and self-sensing capacities of ultra-high-performance fiber-reinforced concrete (UHPFRC with and without carbon nanotubes (CNTs. For this, the effects of steel fiber content, orientation, and pore water content on the electrical and piezoresistive properties of UHPFRC without CNTs were first evaluated. Then, the effect of CNT content on the self-sensing capacities of UHPFRC under compression and flexure was investigated. Test results indicated that higher steel fiber content, better fiber orientation, and higher amount of pore water led to higher electrical conductivity of UHPFRC. The effects of fiber orientation and drying condition on the electrical conductivity became minor as sufficiently high amount of steel fibers, 3% by volume, was added. Including only steel fibers did not impart UHPFRC with piezoresistive properties. Addition of CNTs substantially improved the electrical conductivity of UHPFRC. Under compression, UHPFRC with a CNT content of 0.3% or greater had a self-sensing ability that was activated by the formation of cracks, and better sensing capacity was achieved by including greater amount of CNTs. Furthermore, the pre-peak flexural behavior of UHPFRC was precisely simulated with a fractional change in resistivity when 0.3% CNTs were incorporated. The pre-cracking self-sensing capacity of UHPFRC with CNTs was more effective under tensile stress state than under compressive stress state.

  1. Development of Steel Fiber-Reinforced Expanded-Shale Lightweight Concrete with High Freeze-Thaw Resistance

    Directory of Open Access Journals (Sweden)

    Mingshuang Zhao

    2018-01-01

    Full Text Available For the popularized structural application, steel fiber-reinforced expanded-shale lightweight concrete (SFRELC with high freeze-thaw resistance was developed. The experimental study of this paper figured out the effects of air-entraining content, volume fraction of steel fibers, and fine aggregate type. Results showed that while the less change of mass loss rate was taken place for SFRELC after 300 freeze-thaw cycles, the relative dynamic modulus of elasticity and the relative flexural strength presented clear trends of freeze-thaw resistance of SFRELC. The compound effect of the air-entraining agent and the steel fibers was found to support the SFRELC with high freeze-thaw resistance, and the mechanisms were explored with the aid of the test results of water penetration of SFRELC. The beneficial effect was appeared from the replacement of lightweight sand with manufactured sand. Based on the test results, suggestions are given out for the optimal mix proportion of SFRELC to satisfy the durability requirement of freeze-thaw resistance.

  2. Superconducting properties and uniaxial strain characteristics of Nb3Sn fiber-reinforced superconductors with tantalum reinforcement fibers

    International Nuclear Information System (INIS)

    Arai, Kazuaki; Umeda, Masaichi; Agatsuma, Koh; Tateishi, Hiroshi

    1998-01-01

    We have been developing fiber-reinforced superconductors (FRS) for high-field and large-scale magnets. Tungsten fibers have been selected as the reinforcement fiber for FRS so far because tungsten has the highest elastic modulus of approximately 400 GPa which can minimize the strain from electromagnetic force. The preparation process of FRS consists of sputtering deposition and heat treatment because it may be difficult to apply drawing methods to materials of high-elastic modulus such as tungsten. Tantalum has high elastic modulus of 178 GPa and its thermal expansion coefficient that is closer to that of Nb 3 Sn than tungsten's, which means prestrain in Nb 3 Sn in FRS is reduced by adopting tantalum fibers. Tantalum has been used as barriers between bronze and copper in conventional Nb 3 Sn superconductors which are usually prepared with drawing process despite of the tantalum's high elastic modulus. That implies drawing process may be applied to prepare FRS with tantalum reinforcement fibers. In this paper, FRS using tantalum fibers prepared with sputtering process are described with making comparison with FRS of tungsten to clarify the basic properties of FRS using tantalum fibers. Depth profiles in Nb 3 Sn layer in FRS were measured to examine reaction between superconducting layers and reinforcement fibers. Superconducting properties including strain and stress characteristics were shown. Those data will contribute to design of FRS using tantalum reinforcement fibers with adopts the drawing processes. (author)

  3. Quick Preparation of Moisture-Saturated Carbon Fiber-Reinforced Plastics and Their Accelerated Ageing Tests Using Heat and Moisture

    Directory of Open Access Journals (Sweden)

    Masao Kunioka

    2016-06-01

    Full Text Available A quick method involving the control of heat and water vapor pressure for preparing moisture-saturated carbon fiber-reinforced plastics (CFRP, 8 unidirectional prepreg layers, 1.5 mm thickness, epoxy resin has been developed. The moisture-saturated CFRP sample was obtained at 120 °C and 0.2 MPa water vapor in 72 h by this method using a sterilizer (autoclave. The bending strength and viscoelastic properties measured by a dynamic mechanical analysis (DMA remained unchanged during repetitive saturation and drying steps. No degradation and molecular structural change occurred. Furthermore an accelerated ageing test with two ageing factors, i.e., heat and moisture was developed and performed at 140–160 °C and 0.36–0.62 MPa water vapor pressure by using a sealed pressure-proof stainless steel vessel (autoclave. The bending strength of the sample decreased from 1107 to 319 MPa at 160 °C and 0.63 MPa water vapor pressure in 9 days. Degraded samples were analyzed by DMA. The degree of degradation for samples was analyzed by DMA. CFRP and degraded CFRP samples were analyzed by using a surface and interfacial cutting analysis system (SAICAS and an electron probe micro-analyzer (EPMA equipped in a scanning electron microscope.

  4. ASCE application guide for recommended practice for fiber-reinforced polymer products for overhead utility line structures

    Energy Technology Data Exchange (ETDEWEB)

    Gnandt, E. [T and D High Voltage Consulting, Vancouver, BC (Canada)

    2002-07-01

    The participants to the American Society of Civil Engineers (ASCE) prepared an application guide to provide guidelines to utilities and manufacturers on topics ranging from design to manufacture, testing and installation of fiber-reinforced polymer (FRP) products. The intent was also to help utilities with a possible replacement material for wood, steel and pre-stressed concrete. FRP products are constructed from fiber and resin and offer several advantages such as light weight and high strength-to-weight ratio, low maintenance, dimensional stability, resistance to rot, corrosion, chemicals and pest damage. FRP products can be used for lighting poles, ladders and grating, transformer pads, pole line hardware and crossarms, and other applications. There are five structural configurations: (1) cantilevered structures (single pole), (2) guyed structures, framed structures (H-Frame), (4) a combination of (1), (2), and (3), and (5) lattice structures (transmission class). The author listed some of the initial considerations: physical characteristics, guying and grounding, deflection and load testing, attached items, and durability to name only a few. The materials and manufacturing processes were briefly explained, namely the pultrusion method, the filament winding method, and the centrifugal casting method. Design loads considerations are discussed, as are performance-based criteria such as mechanical, coating durability and electrical. Quality control, assembly erection and storage, and in-service considerations are also discussed. The author concluded the presentation with a section dealing with field inspections. figs.

  5. Effect of fiber content on flexural properties of glass fiber-reinforced polyamide-6 prepared by injection molding.

    Science.gov (United States)

    Nagakura, Manamu; Tanimoto, Yasuhiro; Nishiyama, Norihiro

    2017-07-26

    The use of non-metal clasp denture (NMCD) materials may seriously affect the remaining tissues because of the low rigidity of NMCD materials such as polyamides. The purpose of this study was to develop a high-rigidity glass fiber-reinforced thermoplastic (GFRTP) composed of E-glass fiber and polyamide-6 for NMCDs using an injection molding. The reinforcing effects of fiber on the flexural properties of GFRTPs were investigated using glass fiber content ranging from 0 to 50 mass%. Three-point bending tests indicated that the flexural strength and elastic modulus of a GFRTP with a fiber content of 50 mass% were 5.4 and 4.7 times higher than those of unreinforced polyamide-6, respectively. The result showed that the physical characteristics of GFRTPs were greatly improved by increasing the fiber content, and the beneficial effects of fiber reinforcement were evident. The findings suggest that the injection-molded GFRTPs are adaptable to NMCDs because of their excellent mechanical properties.

  6. Electrical and Self-Sensing Properties of Ultra-High-Performance Fiber-Reinforced Concrete with Carbon Nanotubes.

    Science.gov (United States)

    You, Ilhwan; Yoo, Doo-Yeol; Kim, Sooho; Kim, Min-Jae; Zi, Goangseup

    2017-10-29

    This study examined the electrical and self-sensing capacities of ultra-high-performance fiber-reinforced concrete (UHPFRC) with and without carbon nanotubes (CNTs). For this, the effects of steel fiber content, orientation, and pore water content on the electrical and piezoresistive properties of UHPFRC without CNTs were first evaluated. Then, the effect of CNT content on the self-sensing capacities of UHPFRC under compression and flexure was investigated. Test results indicated that higher steel fiber content, better fiber orientation, and higher amount of pore water led to higher electrical conductivity of UHPFRC. The effects of fiber orientation and drying condition on the electrical conductivity became minor as sufficiently high amount of steel fibers, 3% by volume, was added. Including only steel fibers did not impart UHPFRC with piezoresistive properties. Addition of CNTs substantially improved the electrical conductivity of UHPFRC. Under compression, UHPFRC with a CNT content of 0.3% or greater had a self-sensing ability that was activated by the formation of cracks, and better sensing capacity was achieved by including greater amount of CNTs. Furthermore, the pre-peak flexural behavior of UHPFRC was precisely simulated with a fractional change in resistivity when 0.3% CNTs were incorporated. The pre-cracking self-sensing capacity of UHPFRC with CNTs was more effective under tensile stress state than under compressive stress state.

  7. Semiempirical Methodology for Estimating the Service Life of Concrete Deck Panels Strengthened with Fiber-Reinforced Polymer

    Directory of Open Access Journals (Sweden)

    Eon-Kyoung Kim

    2014-01-01

    Full Text Available Deterioration of concrete bridge decks affects their durability, safety, and function. It is therefore necessary to conduct structural rehabilitation of damaged concrete decks by strengthening them with fiber-reinforced polymer. Of the recent studies on the strengthened structures, most have focused on static behavior; only a few studies have investigated fatigue behavior. Accurate analysis of fatigue in concrete deck performance requires a more realistic simulated moving load. This study developed a theoretical live-load model to reflect the effect of moving vehicle loads, based on a statistical approach to the measurement of real traffic loads over various time periods in Korea. It assessed the fatigue life and strengthening effect of bridge decks strengthened with either carbon fiber sheets or grid carbon fiber polymer plastic using probabilistic and reliability analyses. It used extrapolations and simulations to derive maximum load effects for time periods ranging from 1 day to 75 years. Limited fatigue tests were conducted and probabilistic and reliability analyses were carried out on the strengthened concrete bridge deck specimens to predict the extended fatigue life. Analysis results indicated that strengthened concrete decks provide sufficient resistance against increasing truck loads during the service life of a bridge.

  8. Negative Outcomes of Poly(l-Lactic Acid) Fiber-Reinforced Scaffolds in an Ovine Total Meniscus Replacement Model.

    Science.gov (United States)

    Patel, Jay M; Merriam, Aaron R; Kohn, Joachim; Gatt, Charles J; Dunn, Michael G

    2016-09-01

    Our objective was to test the efficacy of collagen-hyaluronan scaffolds reinforced with poly(l-lactic acid) (PLLA) fibers in an ovine total meniscus replacement model. Scaffolds were implanted into 9 sheep (n = 1 at 8 weeks, n = 2 at 16 weeks, n = 3 at both 24, 32 weeks) following total medial meniscectomy. From 16 weeks on, explants were characterized by confined compression creep, histological, and biochemical analyses. Articular surfaces were observed macroscopically and damage was ranked histologically using the Mankin score. At sacrifice, three of the nine PLLA scaffolds had completely ruptured, and the intact scaffolds experienced progressive shape changes and severe narrowing in the body region at 16, 24, and 32 weeks. Aggregate compressive modulus and permeability did not improve with time. Histological and biochemical analyses showed significantly less extracellular matrix and less matrix organization compared to native tissue. Osteophytes, bone erosion, and cartilage damage were observed, increasing with time postimplantation. A buildup of lactic acid and/or the rapid loss of scaffold mechanical integrity due to PLLA degradation are probable causes for the joint abnormalities observed in this study. These results are in sharp contrast to those of our previous successful total meniscus replacement studies using polyarylate [p(DTD DD)] fiber-reinforced scaffolds. This suggests that PLLA fiber as produced in this study cannot be used as reinforcement for a meniscus replacement scaffold.

  9. Influence of breast composition and interseed attenuation in dose calculations for post-implant assessment of permanent breast 103Pd seed implant

    International Nuclear Information System (INIS)

    Afsharpour, Hossein; Beaulieu, Luc; Pignol, Jean-Philippe; Keller, Brian; Carrier, Jean-Francois; Reniers, Brigitte; Verhaegen, Frank

    2010-01-01

    The impact of tissue heterogeneity and interseed attenuation is studied in post-implant evaluation of five clinical permanent breast 103 Pd seed implants using the Monte Carlo (MC) dose calculation method. Dose metrics for the target (PTV) as well as an organ at risk (skin) are used to visualize the differences between a TG43-like MC method and more accurate MC methods capable of considering the breast tissue heterogeneity as well as the interseed attenuation. PTV dose is reduced when using a breast tissue model instead of water in MC calculations while the dose to the skin is increased. Furthermore, we investigate the effect of varying the glandular/adipose proportion of the breast tissue on dose distributions. The dose to the PTV (skin) decreases (increases) with the increasing adipose proportion inside the breast. In a complete geometry and compared to a TG43-like situation, the average PTV D 90 reduction varies from 3.9% in a glandular breast to 35.5% when the breast consists entirely of adipose. The skin D 10 increases by 28.2% in an entirely adipose breast. The results of this work show the importance of an accurate and patient-dependent breast tissue model to be used in the dosimetry for this kind of low energy implant.

  10. Effect of post-etch annealing gas composition on the structural and electrochemical properties of Ti2CTx MXene electrodes for supercapacitor applications

    KAUST Repository

    Rakhi, R. B.

    2015-07-08

    Two-dimensional Ti2CTx MXene nanosheets were prepared by the selective etching of Al layer from Ti2AlC MAX phase using HF treatment. The MXene sheets retained the hexagonal symmetry of the parent Ti2AlC MAX phase. Effect of the post-etch annealing ambient (Ar, N2, N2/H2 and Air) on the structure and electrochemical properties of the MXene nanosheets was investigated in detail. After annealing in Air, the MXene sheets exhibited variations in structure, morphology and electrochemical properties as compared to HF treated MAX phase. In contrast, samples annealed in Ar, N2 and N2/H2 ambient retained their original morphology. However, a significant improvement in the supercapacitor performance is observed upon heat treatment in Ar, N2 and N2/H2 ambients. When used in symmetric two-electrode configuration, the MXene sample annealed in N2/H2 atmosphere exhibited the best capacitive performance with specific capacitance value (51 F/g at 1A/g) and high rate performance (86%). This improvement in the electrochemical performance of annealed samples is attributed to highest carbon content, and lowest fluorine content on the surface of the sample upon annealing, while retaining the original 2D layered morphology, and providing maximum access of aqueous electrolyte to the electrodes.

  11. Post-mortem analysis on LiFePO4|Graphite cells describing the evolution & composition of covering layer on anode and their impact on cell performance

    Science.gov (United States)

    Lewerenz, Meinert; Warnecke, Alexander; Sauer, Dirk Uwe

    2017-11-01

    During cyclic aging of lithium-ion batteries the formation of a μm-thick covering layer on top of the anode facing the separator is found on top of the anode. In this work several post-mortem analyses of cyclic aged cylindrical LFP|Graphite cells are evaluated to give a detailed characterization of the covering layer and to find possible causes for the evolution of such a layer. The analyses of the layer with different methods return that it consists to high percentage of plated active lithium, deposited Fe and products of a solid electrolyte interphase (SEI). The deposition is located mainly in the center of the cell symmetrical to the coating direction. The origin of these depositions is assumed in locally overcharged particles, Fe deposition or inhomogeneous distribution of capacity density. As a secondary effect the deposition on one side increases the thickness locally; thereafter a pressure-induced overcharging due to charge agglomeration of the back side of the anode occurs. Finally a compact and dense covering layer in a late state of aging leads to deactivation of the covered parts of the anode and cathode due to suppressed lithium-ion conductivity. This leads to increasing slope of capacity fade and increase of internal resistance.

  12. Effect of resin cement, aging process and root level on the bond strength of the resin-fiber posts

    Science.gov (United States)

    Almuhim, Khalid Salman

    Background. Little is known about the long-term clinical bonding effectiveness of the Fiber-reinforced composite (FRC) posts cemented with self-etch adhesive systems. Bond stability and longevity of the cemented post are adversely affected by physical and chemical factors over time, such as expansion and contraction stresses caused by thermal changes and occlusal load. This clinical condition can be simulated in vitro by thermocyclic loading; and bonding effectiveness can be evaluated by applying the micropush out test. Therefore, more in vitro studies are needed to evaluate the bond strength of the fiber posts cemented with different resin cement systems after simulating the artificial aging induced by thermocycling. The aim of this study was to compare the microtensile bond strength of two different resin cement systems (total etch, and self-etch resin cement system) used for cementation of fiber reinforced composite posts in three different aging periods using thermocycling. Methods. Following IRB approval, sixty freshly extracted bicuspid single rooted natural teeth were endodontically treated, and the post-spaces were prepared to receive a fiber-post cemented with either a total etch resin cement (Rely-X Ultimate) or with a self-etch resin cement (Rely-X Unicem). No thermocycling, 20,000 and 40,000 cycles was used to age the specimens. Teeth were randomly allocated into six different groups: G1 - Control: Rely-X Ultimate cement with no thermocycling. G2: Rely-X Ultimate cement with 20,000 thermocycling. G3: Rely-X Ultimate cement with 40,000 thermocycling. G4: Rely-X Unicem cement. G5: Rely-X Unicem cement. G6: Rely-X Unicem cement. Microtensile bond strength determined using a micropush out test on a universal testing machine (MTS). Additionally, the failure mode of each specimen was observed under a stereomicroscope (Olympus) at 40x magnification. Finally, one representative sample was randomly selected from each of the five failure modes for scanning

  13. Compositional variations of zirconolite from the Evate apatite deposit (Mozambique) as an indicator of magmatic-hydrothermal conditions during post-orogenic collapse of Gondwana

    Science.gov (United States)

    Hurai, Vratislav; Huraiová, Monika; Gajdošová, Michaela; Konečný, Patrik; Slobodník, Marek; Siegfried, Pete R.

    2018-06-01

    Zirconolite is documented from the Evate apatite-magnetite-carbonate deposit in the circular Monapo Klippe (eastern Mozambique)—a relic of Neoproterozoic nappe thrusted over the Mesoproterozoic basement of the Nampula block. Zirconolite enriched in rare earth elements—REE = Y + Lu+ΣLa-Yb (up to 24.11 wt% REE2O3, 0.596 apfu REE) creates thin rims around spinel and magnetite grains, whereas zirconolite enriched in U and Th (up to 18.88 wt% ThO2 + UO2, 0.293 apfu Th + U) replace the Late Ediacaran ( 590 Ma) zircon and baddeleyite along contacts with pyrrhotite and magnetite. Both types of zirconolite contain locally increased Nb and Ta concentrations (up to 7.58 wt% Nb2O5 + Ta2O5, 0.202 apfu Nb + Ta). Typical substitutions in zirconolite from Evate involve REE + U,Th → Ca, and M 2++ M 5+→Ti + M 3+ ( M 2+ = Fe2++Mg, M 3+ = Fe3+, M 5+ = Nb5++Ta5+). In addition, REE-zirconolite is typical of the REE + M 2+ → Ca + M 3+ substitution ( M 2+ = Mg, M 3+ = Fe3++Al3+). Hence, Fe3+ predominates over Fe2+ in all types of zirconolite, thus enabling the high REE content in Nb-poor zirconolites to be stored in locally dominant REEZrTiFe3+O7 component known so far only as a synthetic analogue of natural zirconolite. Other types of zirconolite from Evate are dominated by the common CaZrTi2O7 end member, but the aforementioned "synthetic" REEZrTiFe3+O7 accompanied by another `synthetic' (U,Th)ZrFe3 + 2O7 component are also abundant. The U,Pb,Th concentrations in U,Th-zirconolites plot discordantly to theoretical isochrons, thus indicating 440 ppm of non-radiogenic excess lead in earlier Nb-rich zirconolite contrasting with secondary Pb loss from later Nb-poor zirconolite. The non-radiogenic Pb-corrected age of the early zirconolite corresponded to 485 ± 9 Ma, within uncertainty limit identical with the 493 ± 10 Ma age of the associated uranothorianite. The variegated chemical composition of zirconolites reflects the complex history of the Evate deposit. Compositional and

  14. Compositional variations of zirconolite from the Evate apatite deposit (Mozambique) as an indicator of magmatic-hydrothermal conditions during post-orogenic collapse of Gondwana

    Science.gov (United States)

    Hurai, Vratislav; Huraiová, Monika; Gajdošová, Michaela; Konečný, Patrik; Slobodník, Marek; Siegfried, Pete R.

    2017-11-01

    Zirconolite is documented from the Evate apatite-magnetite-carbonate deposit in the circular Monapo Klippe (eastern Mozambique)—a relic of Neoproterozoic nappe thrusted over the Mesoproterozoic basement of the Nampula block. Zirconolite enriched in rare earth elements—REE = Y + Lu+ΣLa-Yb (up to 24.11 wt% REE2O3, 0.596 apfu REE) creates thin rims around spinel and magnetite grains, whereas zirconolite enriched in U and Th (up to 18.88 wt% ThO2 + UO2, 0.293 apfu Th + U) replace the Late Ediacaran ( 590 Ma) zircon and baddeleyite along contacts with pyrrhotite and magnetite. Both types of zirconolite contain locally increased Nb and Ta concentrations (up to 7.58 wt% Nb2O5 + Ta2O5, 0.202 apfu Nb + Ta). Typical substitutions in zirconolite from Evate involve REE + U,Th → Ca, and M 2++M 5+→Ti + M 3+ (M 2+ = Fe2++Mg, M 3+ = Fe3+, M 5+ = Nb5++Ta5+). In addition, REE-zirconolite is typical of the REE + M 2+ → Ca + M 3+ substitution (M 2+ = Mg, M 3+ = Fe3++Al3+). Hence, Fe3+ predominates over Fe2+ in all types of zirconolite, thus enabling the high REE content in Nb-poor zirconolites to be stored in locally dominant REEZrTiFe3+O7 component known so far only as a synthetic analogue of natural zirconolite. Other types of zirconolite from Evate are dominated by the common CaZrTi2O7 end member, but the aforementioned "synthetic" REEZrTiFe3+O7 accompanied by another `synthetic' (U,Th)ZrFe3 + 2O7 component are also abundant. The U,Pb,Th concentrations in U,Th-zirconolites plot discordantly to theoretical isochrons, thus indicating 440 ppm of non-radiogenic excess lead in earlier Nb-rich zirconolite contrasting with secondary Pb loss from later Nb-poor zirconolite. The non-radiogenic Pb-corrected age of the early zirconolite corresponded to 485 ± 9 Ma, within uncertainty limit identical with the 493 ± 10 Ma age of the associated uranothorianite. The variegated chemical composition of zirconolites reflects the complex history of the Evate deposit. Compositional and

  15. A numerical study of the influence of microvoids in the transverse mechanical response of unidirectional composites

    DEFF Research Database (Denmark)

    Ashouri Vajari, Danial; González, Carlos; Llorca, Javier

    2014-01-01

    The effect of porosity on the transverse mechanical properties of unidirectional fiber-reinforced composites is studied by means of computational micromechanics. The composite behavior is simulated by the finite element analysis of a representative volume element of the composite microstructure...... that porosity (in the range 1-5%) led to a large reduction in the transverse strength and the influence of both types of voids in the onset and propagation of damage throughout the microstructure was studied under transverse tension and compression. Finally, the failure locus of the composite lamina under...... transverse tension/compression and out-of-plane shear was obtained by means of computational micromechanics and compared with the predictions of Puck's model and with experimental data available in the literature. The results show that the strength of composites is significantly reduced by the presence...

  16. Applied Integrated Design in Composite UAV Development

    Science.gov (United States)

    Vasić, Zoran; Maksimović, Stevan; Georgijević, Dragutin

    2018-04-01

    This paper presents a modern approach to integrated development of Unmanned Aerial Vehicle made of laminated composite materials from conceptual design, through detail design, strength and stiffness analyses, definition and management of design and production data, detailed tests results and other activities related to development of laminated composite structures with main of its particularities in comparison to metal structures. Special attention in this work is focused to management processes of product data during life cycle of an UAV and experimental tests of its composite wing. Experience shows that the automation management processes of product data during life cycle, as well as processes of manufacturing, are inevitable if a company wants to get cheaper and quality composite aircraft structures. One of the most effective ways of successful management of product data today is Product Life cycle Management (PLM). In terms of the PLM, a spectrum of special measures and provisions has to be implemented when defining fiber-reinforced composite material structures in comparison to designing with metals which is elaborated in the paper.

  17. Wear Behavior of Plasma Spray Deposited and Post Heat-Treated Hydroxyapatite (HA)-Based Composite Coating on Titanium Alloy (Ti-6Al-4V) Substrate

    Science.gov (United States)

    Kumari, Renu; Majumdar, Jyotsna Dutta

    2018-04-01

    The present study concerns a detailed evaluation of wear resistance property of plasma spray deposited composite hydroxyapatite (HA)-based (HA-50 wt pct TiO2 and HA-10 wt pct ZrO2) bioactive coatings developed on Ti-6Al-4V substrate and studying the effect of heat treatment on it. Heat treatment of plasma spray deposited samples has been carried out at 650 °C for 2 hours (for HA-50 wt pct TiO2 coating) and at 750 °C for 2 hours (for HA-10 wt pct ZrO2 coating). There is significant deterioration in wear resistance for HA-50 wt pctTiO2 coating and a marginal deterioration in wear resistance for HA-10 wt pct ZrO2 coating in as-sprayed state (as compared to as-received Ti-6Al-4V) which is, however, improved after heat treatment. The coefficient of friction is marginally increased for both HA-50 wt pct TiO2 and HA-10 wt pct ZrO2 coatings in as-sprayed condition as compared to Ti-6Al-4V substrate. However, coefficient of friction is decreased for both HA-50 wt pct TiO2 and HA-10 wt pct ZrO2 coatings after heat-treated condition as compared to Ti-6Al-4V substrate. The maximum improvement in wear resistance property is, however, observed for HA-10 wt pct ZrO2 sample after heat treatment. The mechanism of wear has been investigated.

  18. Influence of Freeze-Drying and Oven-Drying Post Blanching on the Nutrient Composition of the Edible Insect Ruspolia differens.

    Science.gov (United States)

    Fombong, Forkwa Tengweh; Van Der Borght, Mik; Vanden Broeck, Jozef

    2017-09-16

    The longhorn grasshopper, Ruspolia differens (Serville), plays an important role as a food source across Sub-Saharan Africa, where it is consumed as a delicacy in both rural and urban areas. The effect of two drying methods (freeze-drying and oven-drying), employed after blanching, on the proximate, fatty acid and mineral composition of the two most common morphs was determined. Ruspolia differens grasshoppers were harvested in Uganda and Kenya from wild swarms during the rainy periods of November-December 2016. Based on cuticular coloration, we identified three morphs, green, brown and purple, which occurred at a ratio of 65:33:2, respectively. Results indicated that these insects have a high lipid content of 36%, as well as significant protein levels ranging between 33% and 46% dry matter. Oleic acid (44%) and palmitic acid (28%) were the two most abundant fatty acids; while the presence of arachidonic acid (0.6%) and docosahexaenoic acid (0.21%) suggests that Ruspolia differens is also a source of polyunsaturated fatty acids. The observed amino acid profile showed similar trends in all morphs, and all essential amino acids were present. Calcium (896-1035 mg/100 g), potassium (779-816 mg/100 g) and phosphorus (652-685 mg/100 g) were quite high among the minerals. The presence of the trace elements iron (217-220 mg/100 g), zinc (14.2-14.6 mg/100 g), manganese (7.4-8.3 mg/100 g) and copper (1.66 mg/100 g) suggests that inclusion of these grasshoppers in human diets may aid in combatting micronutrient deficiencies. Oven-drying Ruspolia differens delivered the same nutritional quality as freeze-drying. Hence, both drying approaches can be adequately used to formulate insect-based food products without noticeable nutritional changes.

  19. Influence of Freeze-Drying and Oven-Drying Post Blanching on the Nutrient Composition of the Edible Insect Ruspolia differens

    Directory of Open Access Journals (Sweden)

    Forkwa Tengweh Fombong

    2017-09-01

    Full Text Available The longhorn grasshopper, Ruspolia differens (Serville, plays an important role as a food source across Sub-Saharan Africa, where it is consumed as a delicacy in both rural and urban areas. The effect of two drying methods (freeze-drying and oven-drying, employed after blanching, on the proximate, fatty acid and mineral composition of the two most common morphs was determined. Ruspolia differens grasshoppers were harvested in Uganda and Kenya from wild swarms during the rainy periods of November–December 2016. Based on cuticular coloration, we identified three morphs, green, brown and purple, which occurred at a ratio of 65:33:2, respectively. Results indicated that these insects have a high lipid content of 36%, as well as significant protein levels ranging between 33% and 46% dry matter. Oleic acid (44% and palmitic acid (28% were the two most abundant fatty acids; while the presence of arachidonic acid (0.6% and docosahexaenoic acid (0.21% suggests that Ruspolia differens is also a source of polyunsaturated fatty acids. The observed amino acid profile showed similar trends in all morphs, and all essential amino acids were present. Calcium (896–1035 mg/100 g, potassium (779–816 mg/100 g and phosphorus (652–685 mg/100 g were quite high among the minerals. The presence of the trace elements iron (217–220 mg/100 g, zinc (14.2–14.6 mg/100 g, manganese (7.4–8.3 mg/100 g and copper (1.66 mg/100 g suggests that inclusion of these grasshoppers in human diets may aid in combatting micronutrient deficiencies. Oven-drying Ruspolia differens delivered the same nutritional quality as freeze-drying. Hence, both drying approaches can be adequately used to formulate insect-based food products without noticeable nutritional changes.

  20. The road for nanomaterials industry: a review of carbon nanotube production, post-treatment, and bulk applications for composites and energy storage.

    Science.gov (United States)

    Zhang, Qiang; Huang, Jia-Qi; Qian, Wei-Zhong; Zhang, Ying-Ying; Wei, Fei

    2013-04-22

    The innovation on the low dimensional nanomaterials brings the rapid growth of nano community. Developing the controllable production and commercial applications of nanomaterials for sustainable society is highly concerned. Herein, carbon nanotubes (CNTs) with sp(2) carbon bonding, excellent mechanical, electrical, thermal, as well as transport properties are selected as model nanomaterials to demonstrate the road of nanomaterials towards industry. The engineering principles of the mass production and recent progress in the area of CNT purification and dispersion are described, as well as its bulk application for nanocomposites and energy storage. The environmental, health, and safety considerations of CNTs, and recent progress in CNT commercialization are also included. With the effort from the CNT industry during the past 10 years, the price of multi-walled CNTs have decreased from 45 000 to 100 $ kg(-1) and the productivity increased to several hundred tons per year for commercial applications in Li ion battery and nanocomposites. When the prices of CNTs decrease to 10 $ kg(-1) , their applications as composites and conductive fillers at a million ton scale can be anticipated, replacing conventional carbon black fillers. Compared with traditional bulk chemicals, the controllable synthesis and applications of CNTs on a million ton scale are still far from being achieved due to the challenges in production, purification, dispersion, and commercial application. The basic knowledge of growth mechanisms, efficient and controllable routes for CNT production, the environmental and safety issues, and the commercialization models are still inadequate. The gap between the basic scientific research and industrial development should be bridged by multidisciplinary research for the rapid growth of CNT nano-industry. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.