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Sample records for reinforced composite materials

  1. Nanostructured composite reinforced material

    DOEpatents

    Seals, Roland D.; Ripley, Edward B.; Ludtka, Gerard M.

    2012-07-31

    A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

  2. 3-D textile reinforcements in composite materials

    SciTech Connect

    Miravete, A.

    1999-11-01

    Laminated composite materials have been used in structural applications since the 1960s. However, their high cost and inability to accommodate fibers in the laminate`s thickness direction greatly reduce their damage tolerance and impact resistance. The second generation of materials--3-D textile reinforced composites--offers significant cost reduction, and by incorporating reinforcement in the thickness direction, dramatically increases damage tolerance and impact resistance. However, methods for predicting mechanical properties of 3-D textile reinforced composite materials tend to be more complex. These materials also have disadvantages--particularly in regard to crimps in the yarns--that require more research. Textile preforms, micro- and macromechanical modeling, manufacturing processes, and characterization all need further development. As researchers overcome these problems, this new generation of composites will emerge as a highly competitive family of materials. This book provides a state-of-the-art account of this promising technology. In it, top experts describe the manufacturing processes, highlight the advantages, identify the main applications, analyze methods for predicting mechanical properties, and detail various reinforcement strategies, including grid structure, knitted fabric composites, and the braiding technique. Armed with the information in this book, readers will be prepared to better exploit the advantages of 3-D textile reinforced composites, overcome its disadvantages, and contribute to the further development of the technology.

  3. Processes for fabricating composite reinforced material

    DOEpatents

    Seals, Roland D.; Ripley, Edward B.; Ludtka, Gerard M.

    2015-11-24

    A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

  4. Fiber Reinforced Composite Materials Used for Tankage

    NASA Technical Reports Server (NTRS)

    Cunningham, Christy

    2005-01-01

    The Nonmetallic Materials and Processes Group is presently working on several projects to optimize cost while providing effect materials for the space program. One factor that must be considered is that these materials must meet certain weight requirements. Composites contribute greatly to this effort. Through the use of composites the cost of launching payloads into orbit will be reduced to one-tenth of the current cost. This research project involved composites used for aluminum pressure vessels. These tanks are used to store cryogenic liquids during flight. The tanks need some type of reinforcement. Steel was considered, but added too much weight. As a result, fiber was chosen. Presently, only carbon fibers with epoxy resin are wrapped around the vessels as a primary source of reinforcement. Carbon fibers are lightweight, yet high strength. The carbon fibers are wet wound onto the pressure vessels. This was done using the ENTEC Filament Winding Machine. It was thought that an additional layer of fiber would aid in reinforcement as well as containment and impact reduction. Kevlar was selected because it is light weight, but five times stronger that steel. This is the same fiber that is used to make bullet-proof vests trampolines, and tennis rackets.

  5. Composite structural materials. [fiber reinforced composites for aircraft structures

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

    1981-01-01

    Physical properties of fiber reinforced composites; structural concepts and analysis; manufacturing; reliability; and life prediction are subjects of research conducted to determine the long term integrity of composite aircraft structures under conditions pertinent to service use. Progress is reported in (1) characterizing homogeneity in composite materials; (2) developing methods for analyzing composite materials; (3) studying fatigue in composite materials; (4) determining the temperature and moisture effects on the mechanical properties of laminates; (5) numerically analyzing moisture effects; (6) numerically analyzing the micromechanics of composite fracture; (7) constructing the 727 elevator attachment rib; (8) developing the L-1011 engine drag strut (CAPCOMP 2 program); (9) analyzing mechanical joints in composites; (10) developing computer software; and (11) processing science and technology, with emphasis on the sailplane project.

  6. NDE Elastic Properties of Fiber-Reinforced Composite Materials

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Y.

    1995-01-01

    Fiber-reinforced composites are increasingly replacing metallic alloys as structural materials for primary components of fracture-critical structures. This trend is a result of the growing understanding of material behavior and recognition of the desirable properties of composites. A research program was conducted on NDE methods for determining the elastic properties of composites.

  7. Corrosion and tribological properties of basalt fiber reinforced composite materials

    NASA Astrophysics Data System (ADS)

    Ha, Jin Cheol; Kim, Yun-Hae; Lee, Myeong-Hoon; Moon, Kyung-Man; Park, Se-Ho

    2015-03-01

    This experiment has examined the corrosion and tribological properties of basalt fiber reinforced composite materials. There were slight changes of weight after the occurring of corrosion based on time and H2SO4 concentration, but in general, the weight increased. It is assumed that this happens due to the basalt fiber precipitate. Prior to the corrosion, friction-wear behavior showed irregular patterns compared to metallic materials, and when it was compared with the behavior after the corrosion, the coefficient of friction was 2 to 3 times greater. The coefficient of friction of all test specimen ranged from 0.1 to 0.2. Such a result has proven that the basalt fiber, similar to the resin rubber, shows regular patterns regardless of time and H2SO4 concentration because of the space made between resins and reinforced materials.

  8. Natural Kenaf Fiber Reinforced Composites as Engineered Structural Materials

    NASA Astrophysics Data System (ADS)

    Dittenber, David B.

    The objective of this work was to provide a comprehensive evaluation of natural fiber reinforced polymer (NFRP)'s ability to act as a structural material. As a chemical treatment, aligned kenaf fibers were treated with sodium hydroxide (alkalization) in different concentrations and durations and then manufactured into kenaf fiber / vinyl ester composite plates. Single fiber tensile properties and composite flexural properties, both in dry and saturated environments, were assessed. Based on ASTM standard testing, a comparison of flexural, tensile, compressive, and shear mechanical properties was also made between an untreated kenaf fiber reinforced composite, a chemically treated kenaf fiber reinforced composite, a glass fiber reinforced composite, and oriented strand board (OSB). The mechanical properties were evaluated for dry samples, samples immersed in water for 50 hours, and samples immersed in water until saturation (~2700 hours). Since NFRPs are more vulnerable to environmental effects than synthetic fiber composites, a series of weathering and environmental tests were conducted on the kenaf fiber composites. The environmental conditions studied include real-time outdoor weathering, elevated temperatures, immersion in different pH solutions, and UV exposure. In all of these tests, degradation was found to be more pronounced in the NFRPs than in the glass FRPs; however, in nearly every case the degradation was less than 50% of the flexural strength or stiffness. Using a method of overlapping and meshing discontinuous fiber ends, large mats of fiber bundles were manufactured into composite facesheets for structural insulated panels (SIPs). The polyisocyanurate foam cores proved to be poorly matched to the strength and stiffness of the NFRP facesheets, leading to premature core shear or delamination failures in both flexure and compressive testing. The NFRPs were found to match well with the theoretical stiffness prediction methods of classical lamination

  9. Hot extruded carbon nanotube reinforced aluminum matrix composite materials.

    PubMed

    Kwon, Hansang; Leparoux, Marc

    2012-10-19

    Carbon nanotube (CNT) reinforced aluminum (Al) matrix composite materials were successfully fabricated by mechanical ball milling followed by powder hot extrusion processes. Microstructural analysis revealed that the CNTs were well dispersed at the boundaries and were aligned with the extrusion direction in the composites obtained. Although only a small quantity of CNTs were added to the composite (1 vol%), the Vickers hardness and the tensile strength were significantly enhanced, with an up to three-fold increase relative to that of pure Al. From the fractography of the extruded Al-CNT composite, several shapes were observed in the fracture surface, and this unique morphology is discussed based on the strengthening mechanism. The damage in the CNTs was investigated with Raman spectroscopy. However, the Al-CNT composite materials were not only strengthened by the addition of CNTs but also enhanced by several synergistic effects. The nanoindentation stress-strain curve was successfully constructed by setting the effective zero-load and zero-displacement points and was compared with the tensile stress-strain curve. The yield strengths of the Al-CNT composites from the nanoindentation and tensile tests were compared and discussed. We believe that the yield strength can be predicted using a simple nanoindentation stress/strain curve and that this method will be useful for materials that are difficult to machine, such as complex ceramics. PMID:23011263

  10. Hot extruded carbon nanotube reinforced aluminum matrix composite materials

    NASA Astrophysics Data System (ADS)

    Kwon, Hansang; Leparoux, Marc

    2012-10-01

    Carbon nanotube (CNT) reinforced aluminum (Al) matrix composite materials were successfully fabricated by mechanical ball milling followed by powder hot extrusion processes. Microstructural analysis revealed that the CNTs were well dispersed at the boundaries and were aligned with the extrusion direction in the composites obtained. Although only a small quantity of CNTs were added to the composite (1 vol%), the Vickers hardness and the tensile strength were significantly enhanced, with an up to three-fold increase relative to that of pure Al. From the fractography of the extruded Al-CNT composite, several shapes were observed in the fracture surface, and this unique morphology is discussed based on the strengthening mechanism. The damage in the CNTs was investigated with Raman spectroscopy. However, the Al-CNT composite materials were not only strengthened by the addition of CNTs but also enhanced by several synergistic effects. The nanoindentation stress-strain curve was successfully constructed by setting the effective zero-load and zero-displacement points and was compared with the tensile stress-strain curve. The yield strengths of the Al-CNT composites from the nanoindentation and tensile tests were compared and discussed. We believe that the yield strength can be predicted using a simple nanoindentation stress/strain curve and that this method will be useful for materials that are difficult to machine, such as complex ceramics.

  11. Mechanical response of composite materials with through-the-thickness reinforcement

    NASA Technical Reports Server (NTRS)

    Farley, Gary L.; Dickinson, Larry C.

    1992-01-01

    An experimental investigation was conducted to identify the key geometrical parameters and quantify their influence on the mechanical response of through-the-thickness (TTT) reinforced composite materials. Composite laminates with TTT reinforcement fibers were fabricated using different TTT reinforcement materials and reinforcement methods and laminates were also fabricated of similar construction but without TTT reinforcement fibers. Coupon specimens were machined from these laminates and were destructively tested. TTT reinforcement yarns enhance damage tolerance and improve interlaminar strength. Thick-layer composites with TTT reinforcement yarns have equal or superior mechanical properties to thin-layer composites without TTT reinforcement yarns. A significant potential exists for fabrication cost reduction by using thick-layer composites with TTT reinforcement yarns. Removal of the surface loop of the TTT reinforcement improves compression strength. Stitching provides somewhat higher mechanical properties than integral weaving.

  12. Analysis of woven fabrics for reinforced composite materials

    NASA Technical Reports Server (NTRS)

    Dow, Norris F.; Ramnath, V.; Rosen, B. Walter

    1987-01-01

    The use of woven fabrics as reinforcements for composites is considered. Methods of analysis of properties are reviewed and extended, with particular attention paid to three-dimensional constructions having through-the-thickness reinforcements. Methodology developed is used parametrically to evaluate the performance potential of a wide variety of reinforcement constructions including hybrids. Comparisons are made of predicted and measured properties of representative composites having biaxial and triaxial woven, and laminated tape lay-up reinforcements. Overall results are incorporated in advanced weave designs.

  13. Dual-nanoparticulate-reinforced aluminum matrix composite materials.

    PubMed

    Kwon, Hansang; Cho, Seungchan; Leparoux, Marc; Kawasaki, Akira

    2012-06-01

    Aluminum (Al) matrix composite materials reinforced with carbon nanotubes (CNT) and silicon carbide nanoparticles (nano-SiC) were fabricated by mechanical ball milling, followed by hot-pressing. Nano-SiC was used as an active mixing agent for dispersing the CNTs in the Al powder. The hardness of the produced composites was dramatically increased, up to eight times higher than bulk pure Al, by increasing the amount of nano-SiC particles. A small quantity of aluminum carbide (Al(4)C(3)) was observed by TEM analysis and quantified using x-ray diffraction. The composite with the highest hardness values contained some nanosized Al(4)C(3). Along with the CNT and the nano-SiC, Al(4)C(3) also seemed to play a role in the enhanced hardness of the composites. The high energy milling process seems to lead to a homogeneous dispersion of the high aspect ratio CNTs, and of the nearly spherical nano-SiC particles in the Al matrix. This powder metallurgical approach could also be applied to other nanoreinforced composites, such as ceramics or complex matrix materials. PMID:22571898

  14. Dual-nanoparticulate-reinforced aluminum matrix composite materials

    NASA Astrophysics Data System (ADS)

    Kwon, Hansang; Cho, Seungchan; Leparoux, Marc; Kawasaki, Akira

    2012-06-01

    Aluminum (Al) matrix composite materials reinforced with carbon nanotubes (CNT) and silicon carbide nanoparticles (nano-SiC) were fabricated by mechanical ball milling, followed by hot-pressing. Nano-SiC was used as an active mixing agent for dispersing the CNTs in the Al powder. The hardness of the produced composites was dramatically increased, up to eight times higher than bulk pure Al, by increasing the amount of nano-SiC particles. A small quantity of aluminum carbide (Al4C3) was observed by TEM analysis and quantified using x-ray diffraction. The composite with the highest hardness values contained some nanosized Al4C3. Along with the CNT and the nano-SiC, Al4C3 also seemed to play a role in the enhanced hardness of the composites. The high energy milling process seems to lead to a homogeneous dispersion of the high aspect ratio CNTs, and of the nearly spherical nano-SiC particles in the Al matrix. This powder metallurgical approach could also be applied to other nanoreinforced composites, such as ceramics or complex matrix materials.

  15. MULTIPHASE MATERIAL OPTIMIZATION FOR FIBER REINFORCED COMPOSITES CONSIDERING STRAIN SOFTENING

    NASA Astrophysics Data System (ADS)

    Kato, Junji; Ramm, Ekkehard; Terada, Kenjiro; Kyoya, Takashi

    The present paper addresses an optimization strategy of textile fiber reinforced concrete (FRC) with emphasis on its special failure behavior. Since both concrete and fiber are brittle materials, a prominent objective for FRC structures is concerned with the improvement of structural ductility, which may be defined as energy absorption capacity. Despite above unfavorable characteristics, the interface between fiber and matrix plays a substantial role in the structural response. This favorable 'composite effect' is related to material parameters involved in the interface and the material layout on the small scale level. Therefore the purpose of the present paper is to improve the structural ductility of FRC at the macroscopic level applying an optimization method with respect to significant material parameters at the small scale level. The method discussed is based on multiphase material optimization. This methodology is extended to a damage formulation. The performance of the proposed method is demonstrated in a series of numerical examples; it is verified that the structural ductility can be considerably improved.

  16. Development of Ceramic Fibers for Reinforcement in Composite Materials

    NASA Technical Reports Server (NTRS)

    Gates, L. E.; Lent, W. E.; Teague, W. T.

    1961-01-01

    the. testing apparatus for single fiber tensile strength increased the precision. of tests conducted on nine fibers. The highest mean tensile strength, a value of 295,000 pounds per square inch, was obtained with R-141 fibers. Treatment of R-74 fibers with anhydrous Linde A-1100 silane finish improved its mean fiber tensile strength by 25 percent. The lapse of time after fiber formation had no measurable effect on tensile strength. A static heating test conducted with various high melting fibers indicated that Fiberfrax and R-108 underwent no significant changes in bulk volume or resiliency on exposure to 2750 degrees Fahrenheit (1510 degrees Centigrade) in an oxidizing atmosphere. For fiber-resin composition fabrication, ten fiber materials were selected on the bases of high fiber yield, fusion temperature, and type of composition. Fiberfrax, a commercial ceramic fiber, was included for comparison. A new, more effective method of removing pellets from blown fibers was developed. The de-pelletized fibers were treated with a silane finish and felted into ten-inch diameter felts prior to resin impregnation. Composites containing 30 percent by weight of CTL 91-LD phenolic resin were molded under high pressure from the impregnated felts and post-cured to achieve optimum properties. Flexural strength, flexural modules of elasticity, and punch shear strength tests were conducted on the composite specimens. The highest average flexural strength obtained was 19,958 pounds per square inch with the R-74-fiber-resin composite. This compares very favorably with the military specification of 13,000 pounds per square inch flexural strength for randomly oriented fiber reinforced composites. The highest punch shear strength (11,509 pounds per square inch) was obtained with the R-89 fiber-resin composite. The effects of anhydrous fiber finishes on composite strength were not clearly indicated. Plasma arc tests at a heat flux of 550 British Thermal Units per square foot per second on

  17. Creep behavior of abaca fibre reinforced composite material

    SciTech Connect

    Tobias, B.C.; Lieng, V.T.

    1996-12-31

    This study investigates the creep behavior of abaca fibre reinforced composite lamina. The optimum proportions of constituents and loading conditions, temperature and stresses, are investigated in terms of creep properties. Lamina with abaca fibre volume fractions of 60, 70 and 80 percent, embedded in polyester resin were fabricated. Creep tests in tension at three temperature levels 20{degrees}C, 100{degrees}C and 120{degrees}C and three constant stress levels of 0. 1 MPa, 0. 13 Mpa and 0. 198 MPa using a Dynamic Mechanical Analyzer (DMA) were performed. The creep curves show standard regions of an ideal creep curve such as primary and secondary creep stage. The results also show that the minimum creep rate of abaca fibre reinforced composite increases with the increase of temperature and applied stress. Plotting the minimum creep rate against stress, depicts the variations of stress exponents which vary from 1.6194 at 20{degrees}C to 0.4576 at 120{degrees}C.

  18. Fungal degradation of fiber-reinforced composite materials

    NASA Technical Reports Server (NTRS)

    Gu, J. D.; Lu, C.; Mitchell, R.; Thorp, K.; Crasto, A.

    1997-01-01

    As described in a previous report, a fungal consortium isolated from degraded polymeric materials was capable of growth on presterilized coupons of five composites, resulting in deep penetration into the interior of all materials within five weeks. Data describing the utilization of composite constituents as nutrients for the microflora are described in this article. Increased microbial growth was observed when composite extract was incubated with the fungal inoculum at ambient temperatures. Scanning electron microscopic observation of carbon fibers incubated with a naturally developed population of microorganisms showed the formation of bacterial biofilms on the fiber surfaces, suggesting possible utilization of the fiber chemical sizing as carbon and energy sources. Electrochemical impedance spectroscopy was used to monitor the phenomena occurring at the fiber-matrix interfaces. Significant differences were observed between inoculated and sterile panels of the composite materials. A progressive decline in impedance was detected in the inoculated panels. Several reaction steps may be involved in the degradation process. Initial ingress of water into the resin matrix appeared to be followed by degradation of fiber surfaces, and separation of fibers from the resin matrix. This investigation suggested that composite materials are susceptible to microbial attack by providing nutrients for growth.

  19. Nano-particulate dispersion and reinforcement of nanostructured composite materials

    NASA Astrophysics Data System (ADS)

    Yong, Virginia Hiu-Hung

    2005-12-01

    This research investigated the feasibility of reinforcing polymer composites using 30 nm SiC nanoparticles in a vinyl ester resin. The SiC nanoparticles were examined using transmission electron microscopy and thermogravimetric analysis. Gamma-methacryloxy propyl trimethoxy silane (MPS) was chosen as the coupling agent. Both mixing procedures with (1) the nanoparticles pretreated with a dilute MPS solution in an acid 5% (v/v) water-ethanol mixture and (2) the MPS sonicated as an integral blend with the filled vinyl ester, were attempted. Fourier transform infrared spectroscopy was used to study the silanol condensation between MPS and the SiC nanoparticles. The results show that ultrasonic mixing did not fully disperse the particles. Hence the composite strength did not improve although the modulus increased. The use of MPS improved the dispersion quality and hence the composite strength. The rheological behavior of SiC nanoparticle-filled vinyl ester resin systems was evaluated in terms of the Bingham, power law, Herschel-Bulkley, and Casson models. Even when the particle loading was less then 4% by weight, the viscosity of the nanoparticle suspension was found to increase much more than that of a microparticle suspension. This phenomenon may be the result of association between nanoparticles and polymer molecules, effectively making the nanoparticles larger. The resulting reduction in the mobility of polymer molecules also led to delayed curing. The maximum particle loading corresponding to infinite viscosity was determined as 0.1 volume fraction using the (1 - eta r-1/2) - φ dependence. The experimental optimum fractional weight per cent of the dispersants (wt. % dispersant/wt. % SiC) was found to be around 40% for 30 nm SiC nanoparticles, which is in close agreement with the theoretically calculated monolayer coverage dosage of 67%.

  20. Fibre-reinforced materials.

    PubMed

    Brown, D

    2000-11-01

    This paper considers the role of fibres in the reinforcement of composite materials, and the significance of the form the fibre takes and the material from which it is made. The current dental applications of fibre reinforcement, including dental cements and splints, fibres made into structures for use in composites, denture bases and the contemporary use of fibres in fixed partial dentures, are reviewed. Their role in biomedical implants is surveyed and their future forecast. PMID:11218597

  1. Styrene-terminated polysulfone oligomers as matrix material for graphite reinforced composites - An initial study

    NASA Technical Reports Server (NTRS)

    Garcia, Dana; Bowles, Kenneth J.; Vannucci, Raymond D.

    1987-01-01

    Results pertaining to graphite reinforced composites containing styrene-terminated oligomers as the matrix material are summarized. The processing parameters are determined and the properties of the resulting composite are evaluated. In terms of solvent impregnation techniques, CH2Cl2 is the preferred solvent due to its easy removal during the prepreg drying and consolidation steps.

  2. Compressive strength of fiber-reinforced composite materials

    NASA Technical Reports Server (NTRS)

    Davis, J. G., Jr.

    1975-01-01

    Results of an experimental and analytical investigation of the compressive strength of unidirectional boron-epoxy composite material are presented. Observation of fiber coordinates in a boron-epoxy composite indicates that the fibers contain initial curvature. Combined axial compression and torsion tests were conducted on boron-epoxy tubes and it was shown that the shear modulus is a function of axial compressive stress. An analytical model which includes initial curvature in the fibers and permits an estimate of the effect of curvature on compressive strength is proposed. Two modes of failure which may result from the application of axial compressive stress are analyzed - delamination and shear instability. Based on tests and analysis, failure of boron-epoxy under axial compressive load is due to shear instability.

  3. Reinforcements: The key to high performance composite materials

    NASA Technical Reports Server (NTRS)

    Grisaffe, Salvatore J.

    1990-01-01

    Better high temperature fibers are the key to high performance, light weight composite materials. However, current U.S. and Japanese fibers still have inadequate high temperature strength, creep resistance, oxidation resistance, modulus, stability, and thermal expansion match with some of the high temperature matrices being considered for future aerospace applications. In response to this clear deficiency, both countries have research and development activities underway. Once successful fibers are identified, their production will need to be taken from laboratory scale to pilot plant scale. In such efforts it can be anticipated that the Japanese decisions will be based on longer term criteria than those applied in the U.S. Since the initial markets will be small, short term financial criteria may adversely minimize the number and strength of U.S. aerospace materials suppliers to well into the 21st century. This situation can only be compounded by the Japanese interests in learning to make commercial products with existing materials so that when the required advanced fibers eventually do arrive, their manufacturing skills will be developed.

  4. MATERIAL SHAPE OPTIMIZATION FOR FIBER REINFORCED COMPOSITES APPLYING A DAMAGE FORMULATION

    NASA Astrophysics Data System (ADS)

    Kato, Junji; Ramm, Ekkehard; Terada, Kenjiro; Kyoya, Takashi

    The present contribution deals with an optimization strategy of fiber reinforced composites. Although the methodical concept is very general we concentrate on Fiber Reinforced Concrete with a complex failure mechanism resulting from material brittleness of both constituents matrix and fibers. The purpose of the present paper is to improve the structural ductility of the fiber reinforced composites applying an optimization method with respect to the geometrical layout of continuous long textile fibers. The method proposed is achieved by applying a so-called embedded reinforcement formulation. This methodology is extended to a damage formulation in order to represent a realistic structural behavior. For the optimization problem a gradient-based optimization scheme is assumed. An optimality criteria method is applied because of its numerically high efficiency and robustness. The performance of the method is demonstrated by a series of numerical examples; it is verified that the ductility can be substantially improved.

  5. Quasicrystalline particulate reinforced aluminum composite

    SciTech Connect

    Anderson, I.E.; Biner, S.B.; Sordelet, D.J.; Unal, O.

    1997-07-01

    Particulate reinforced aluminum and aluminum alloy composites are rapidly emerging as new commercial materials for aerospace, automotive, electronic packaging and other high performance applications. However, their low processing ductility and difficulty in recyclability have been the key concern. In this study, two composite systems having the same aluminum alloy matrix, one reinforced with quasicrystals and the other reinforced with the conventional SiC reinforcements were produced with identical processing routes. Their processing characteristics and tensile mechanical properties were compared.

  6. Modelling of dimensional stability of fiber reinforced composite materials

    NASA Technical Reports Server (NTRS)

    Hahn, H. T.; Hosangadi, A.

    1982-01-01

    Various methods of predicting the expansion and diffusion properties of composite laminates are reviewed. The prediction equations for continuous fiber composites can be applied to SMC composites as the effective fiber aspect ratio in the latter is large enough. The effect of hygrothermal expansion on the dimensional stability of composite laminates was demonstrated through the warping of unsymmetric graphite/epoxy laminates. The warping is very sensitive to the size of the panel, and to the moisture content which is in turn sensitive to the relative humidity in the environment. Thus, any long term creep test must be carried out in a humidity-controlled environment. Environmental effects in SMC composites and bulk polyester were studied under seven different environments. The SMC composites chosen are SMC-R25, SMC-R40, and SMC-R65.

  7. Yeh-Stratton Criterion for Stress Concentrations on Fiber-Reinforced Composite Materials

    NASA Technical Reports Server (NTRS)

    Yeh, Hsien-Yang; Richards, W. Lance

    1996-01-01

    This study investigated the Yeh-Stratton Failure Criterion with the stress concentrations on fiber-reinforced composites materials under tensile stresses. The Yeh-Stratton Failure Criterion was developed from the initial yielding of materials based on macromechanics. To investigate this criterion, the influence of the materials anisotropic properties and far field loading on the composite materials with central hole and normal crack were studied. Special emphasis was placed on defining the crack tip stress fields and their applications. The study of Yeh-Stratton criterion for damage zone stress fields on fiber-reinforced composites under tensile loading was compared with several fracture criteria; Tsai-Wu Theory, Hoffman Theory, Fischer Theory, and Cowin Theory. Theoretical predictions from these criteria are examined using experimental results.

  8. Strength and toughness of structural fibres for composite material reinforcement.

    PubMed

    Herráez, M; Fernández, A; Lopes, C S; González, C

    2016-07-13

    The characterization of the strength and fracture toughness of three common structural fibres, E-glass, AS4 carbon and Kevlar KM2, is presented in this work. The notched specimens were prepared by means of selective carving of individual fibres by means of the focused ion beam. A straight-fronted edge notch was introduced in a plane perpendicular to the fibre axis, with the relative notch depth being a0/D≈0.1 and the notch radius at the tip approximately 50 nm. The selection of the appropriate beam current during milling operations was performed to avoid to as much as possible any microstructural changes owing to ion impingement. Both notched and un-notched fibres were submitted to uniaxial tensile tests up to failure. The strength of the un-notched fibres was characterized in terms of the Weibull statistics, whereas the residual strength of the notched fibres was used to determine their apparent toughness. To this end, the stress intensity factor of a fronted edge crack was computed by means of the finite-element method for different crack lengths. The experimental results agreed with those reported in the literature for polyacrylonitrile-based carbon fibres obtained by using similar techniques. After mechanical testing, the fracture surface of the fibres was analysed to ascertain the failure mechanisms. It was found that AS4 carbon and E-glass fibres presented the lower toughness with fracture surfaces perpendicular to the fibre axis, emanating from the notch tip. The fractured region of Kevlar KM2 fibres extended along the fibre and showed large permanent deformation, which explains their higher degree of toughness when compared with carbon and glass fibres. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'. PMID:27242306

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

    NASA Technical Reports Server (NTRS)

    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.

  10. Composite material reinforced with atomized quasicrystalline particles and method of making same

    DOEpatents

    Biner, S.B.; Sordelet, D.J.; Lograsso, B.K.; Anderson, I.E.

    1998-12-22

    A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quasicrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked composite exhibits substantially improved yield strength, tensile strength, Young`s modulus (stiffness). 3 figs.

  11. Styrene-terminated polysulfone oligomers as matrix material for graphite reinforced composites: An initial study

    NASA Technical Reports Server (NTRS)

    Garcia, Dana; Bowles, Kenneth J.; Vannucci, Raymond D.

    1987-01-01

    Styrene terminated polysulfone oligomers are part of an oligomeric class of compounds with end groups capable of thermal polymerization. These materials can be used as matrices for graphite reinforced composites. The initial evaluation of styrene terminated polysulfone oligomer based composites are summarized in terms of fabrication methods, and mechanical and environmental properties. In addition, a description and evaluation is provided of the NASA/Industry Fellowship Program for Technology Transfer.

  12. A mechanism responsible for reducing compression strength of through-the-thickness reinforced composite material

    NASA Technical Reports Server (NTRS)

    Farley, Gary L.

    1992-01-01

    A study was conducted to identify one of the mechanisms that contributes to the reduced compression strength of composite materials with through-the-thickness (TTT) reinforcements. In this study a series of thick (0/90) laminates with stitched and integrally woven TTT reinforcements were fabricated and statically tested. In both the stitching and weaving process a surface loop of TTT reinforcement yarn is created between successive TTT penetrations. It was shown that the surface loop of the TTT reinforcement 'kinked' the in-plane fibers in such a manner that they were made ineffective in carrying compressive load. The improvement in strength by removal of the surface loop and 'kinked' in-plane fibers was between 7 and 35 percent.

  13. Micromechanics for particulate reinforced composites

    NASA Technical Reports Server (NTRS)

    Murthy, Pappu L. N.; Goldberg, Robert K.; Mital, Subodh K.

    1996-01-01

    A set of micromechanics equations for the analysis of particulate reinforced composites is developed using the mechanics of materials approach. Simplified equations are used to compute homogenized or equivalent thermal and mechanical properties of particulate reinforced composites in terms of the properties of the constituent materials. The microstress equations are also presented here to decompose the applied stresses on the overall composite to the microstresses in the constituent materials. The properties of a 'generic' particulate composite as well as those of a particle reinforced metal matrix composite are predicted and compared with other theories as well as some experimental data. The micromechanics predictions are in excellent agreement with the measured values.

  14. Nanofiber reinforcement of a geopolymer matrix for improved composite materials mechanical performance

    NASA Astrophysics Data System (ADS)

    Rahman, AKM Samsur

    Geopolymers have the potential to cross the process performance gap between polymer matrix and ceramic matrix composites (CMC), enabling high temperature capable composites that are manufactured at relatively low temperatures. Unfortunately, the inherently low toughness of these geopolymers limits the performance of the resulting fiber reinforced geopolymer matrix composites. Toughness improvements in composites can be addressed through the adjustments in the fiber/matrix interfacial strength and through the improvements in the inherent toughness of the constituent materials. This study investigates the potential to improve the inherent toughness of the geopolymer matrix material through the addition of nanofillers, by considering physical dimensions, mechanical properties, reinforcing capability and interfacial bond strength effects. A process optimization study was first undertaken to develop the ability to produce consistent, neat geopolymer samples, a critical precursor to producing nano-filled geopolymer for toughness evaluation. After that, single edge notched bend beam fracture toughness and un-notched beam flexural strength were evaluated for silicon carbide, alumina and carbon nanofillers reinforced geopolymer samples treated at various temperatures in reactive and inert environments. Toughness results of silicon carbide and carbon nanofillers reinforced geopolymers suggested that with the improved baseline properties, high aspect ratio nanofillers with high interfacial bond strength are the most capable in further improving the toughness of geopolymers. Among the high aspect ratio nanofillers i.e. nanofibers, 2vol% silicon carbide whicker (SCW) showed the highest improvement in fracture toughness and flexural strength of ~164% & ~185%, respectively. After heat treatment at 650 °C, SCW reinforcement was found to be effective, with little reduction in the performance, while the performance of alumina nanofiber (ANF) reinforced geopolymer significantly

  15. Diaphragm forming of carbon-fiber-reinforced thermoplastic composite materials

    SciTech Connect

    Smiley, A.J.

    1988-01-01

    The experimental work consisted of fabricating composite components and identifying the effects of the forming parameters on the resulting thickness profiles and fiber orientation. The transverse fiber flow produced thickness variations and fiber-orientation fields peculiar to the tool-surface geometry, diaphragm deformation behavior, and laminate configuration. The transverse flow in the surface-ply layers was dominated by the stretching diaphragms. In the interior ply layers the flow appeared to be driven by the pressure gradients produced at the contact points. The analytical work consisted of the development of a diaphragm-forming process model which employed engineering mechanics and fiber kinematics to predict post-formed thickness variations and fiber orientation fields of axisymmetric composite components. The flow analysis determined the thickness variation and flow velocities in the transverse fiber direction. The flow velocities were employed to determine the relative fiber realignment. The realignment of the fibers was then utilized in a geometric mapping procedure to determine the fiber-orientation field. Overall, the predictions on interior-ply and surface-ply layer orientations matched reasonably well with the experimental observations.

  16. Composite material reinforced with atomized quasicrystalline particles and method of making same

    DOEpatents

    Biner, Suleyman B.; Sordelet, Daniel J.; Lograsso, Barbara K.; Anderson, Iver E.

    1998-12-22

    A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quaiscrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked compositehibits substantially improved yield strength, tensile strength, Young's modulus (stiffness).

  17. Adherence of Streptococcus mutans to Fiber-Reinforced Filling Composite and Conventional Restorative Materials.

    PubMed

    Lassila, Lippo V J; Garoushi, Sufyan; Tanner, Johanna; Vallittu, Pekka K; Söderling, Eva

    2009-01-01

    OBJECTIVES.: The aim was to investigate the adhesion of Streptococcus mutans (S. mutans) to a short glass fibers reinforced semi-IPN polymer matrix composite resin. The effect of surface roughness on adhesion was also studied. For comparison, different commercial restorative materials were also evaluated. MATERIALS AND METHODS.: Experimental composite FC resin was prepared by mixing 22.5 wt% of short E-glass fibers, 22.5 wt% of IPN-resin and 55 wt% of silane treated silica fillers using high speed mixing machine. Three direct composite resins (Z250, Grandio and Nulite), resin-modified glass ionomers (Fuji II LC), amalgam (ANA 2000), fiber-reinforced composite (FRC) (everStick and Ribbond), and pre-fabricated ceramic filling insert (Cerana class 1) were tested in this study. Enamel and dentin were used as controls. The specimens (n=3/group) with or without saliva were incubated in a suspension of S. mutans allowing initial adhesion to occur. For the enumeration of cells on the disc surfaces as colony forming units (CFU) the vials with the microbe samples were thoroughly Vortex-treated and after serial dilutions grown anaerobically for 2 days at +37 degrees C on Mitis salivarius agars (Difco) containing bacitracin. Bacterial adhesion was also evaluated by using scanning electron microscopy. Surface roughness (Ra) of the materials was also determined using a surface profilometer. All results were statistically analyzed with one-way analysis of variance (ANOVA). RESULTS.: Composite FC resin and other commercial restorative materials showed similar adhesion of S. mutans, while adhesion to dentin and enamel was significantly higher (p<0.05). Surface roughness had no effect on bacterial adhesion. Saliva coating significantly decreased the adhesion for all materials (p<0.05). Composite FC resin had a significantly higher Ra value than control groups (p<0.05). CONCLUSIONS.: Short fiber-reinforced composite with semi-IPN polymer matrix revealed similar S. mutans adhesion

  18. Adherence of Streptococcus mutans to Fiber-Reinforced Filling Composite and Conventional Restorative Materials

    PubMed Central

    Lassila, Lippo V.J; Garoushi, Sufyan; Tanner, Johanna; Vallittu, Pekka K; Söderling, Eva

    2009-01-01

    Objectives. The aim was to investigate the adhesion of Streptococcus mutans (S. mutans) to a short glass fibers reinforced semi-IPN polymer matrix composite resin. The effect of surface roughness on adhesion was also studied. For comparison, different commercial restorative materials were also evaluated. Materials and Methods. Experimental composite FC resin was prepared by mixing 22.5 wt% of short E-glass fibers, 22.5 wt% of IPN-resin and 55 wt% of silane treated silica fillers using high speed mixing machine. Three direct composite resins (Z250, Grandio and Nulite), resin-modified glass ionomers (Fuji II LC), amalgam (ANA 2000), fiber-reinforced composite (FRC) (everStick and Ribbond), and pre-fabricated ceramic filling insert (Cerana class 1) were tested in this study. Enamel and dentin were used as controls. The specimens (n=3/group) with or without saliva were incubated in a suspension of S. mutans allowing initial adhesion to occur. For the enumeration of cells on the disc surfaces as colony forming units (CFU) the vials with the microbe samples were thoroughly Vortex-treated and after serial dilutions grown anaerobically for 2 days at +37°C on Mitis salivarius agars (Difco) containing bacitracin. Bacterial adhesion was also evaluated by using scanning electron microscopy. Surface roughness (Ra) of the materials was also determined using a surface profilometer. All results were statistically analyzed with one-way analysis of variance (ANOVA). Results. Composite FC resin and other commercial restorative materials showed similar adhesion of S. mutans, while adhesion to dentin and enamel was significantly higher (p<0.05). Surface roughness had no effect on bacterial adhesion. Saliva coating significantly decreased the adhesion for all materials (p<0.05). Composite FC resin had a significantly higher Ra value than control groups (p<0.05). Conclusions. Short fiber-reinforced composite with semi-IPN polymer matrix revealed similar S. mutans adhesion than

  19. Processing and Material Characterization of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics.

    NASA Technical Reports Server (NTRS)

    Cox, Sarah B.

    2014-01-01

    The need for high performance vehicles in the aerospace industry requires materials which can withstand high loads and high temperatures. New developments in launch pads and infrastructure must also be made to handle this intense environment with lightweight, reusable, structural materials. By using more functional materials, better performance can be seen in the launch environment, and launch vehicle designs which have not been previously used can be considered. The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer matrix composites can be used for temperatures up to 260C. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in the composites. In this study, continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. The oxyacetylene torch testing and three point bend testing have been performed on test panels and the test results are presented.

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

    NASA Astrophysics Data System (ADS)

    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

  1. Determination of Material Parameters for Microbuckling Analysis of Fiber Reinforced Polymer Matrix Composites

    NASA Astrophysics Data System (ADS)

    Romanowicz, M.

    2015-05-01

    This research focuses on studying the effect of the constitutive law adopted for a matrix material on the compressive response of a unidirectional fiber reinforced polymer matrix composite. To investigate this effect, a periodic unit cell model of a unidirectional composite with an initial fiber waviness and inelastic behavior of the matrix was used. The sensitivity of the compressive strength to the hydrostatic pressure, the flow rule and the fiber misalignment angle were presented. The model was verified against an analytical solution and experimental data. Results of this study indicate that a micromechanical model with correctly identified material parameters provides a useful alternative to theoretical models and experimentation.

  2. Effect of reinforcement and fiber-matrix interface on dynamic fracture of fiber-reinforced composite materials

    SciTech Connect

    Khanna, S.K.

    1992-01-01

    The experimental technique of dynamic photoelasticity coupled with high speed photography has been used to study the interaction of running cracks with brittle and ductile fibers embedded in a brittle polymeric matrix. The effect of reinforcement and the fiber-matrix interface on dynamic stress intensity factor, crack bridging phenomena, crack surface morphology and toughening mechanisms occurring during dynamic fracturing of reinforced brittle matrix composites has been investigated. It is found that reinforcement reduces the crack velocity and the stress intensity factor. Thus the energy supplied to the crack tip is reduced resulting in reduction of the crack jump distance. Fiber pullout experiments were done to characterize the fiber-matrix interface. Rapid pullout results in an increase in interface shear strength. For rapid pullout of fibers the difference between maximum pullout loads. for well and weakly bonded fibers, is much smaller than for very slow pullout. A fiber-matrix interface which is weaker in the vicinity of the crack path, termed the partly debonded interface, produces higher crack closing forces and lower stress intensity factor compared to well bonded fibers. The former interface condition results in low fracture energy and shorter crack jump compared to the later. The interface condition significantly affects the fracture surface morphology. The fracture surface roughness is lower for reinforced materials compared to monolithic. Further the partly debonded fibers result in lower surface roughness compared to the well bonded fibers. Inclined fibers with various interface conditions have no significant effect on the stress intensity factor. The fiber debonded length, however, decreases, as compared to fibers which are aligned with the loading direction, due to the kinking of the fibers.

  3. Investigation of Polymer Resin/Fiber Compatibility in Natural Fiber Reinforced Composite Automotive Materials

    SciTech Connect

    Fifield, Leonard S.; Huang, Cheng; Simmons, Kevin L.

    2010-01-01

    Natural fibers represent a lower density and potentially lower cost alternative to glass fibers for reinforcement of polymers in automotive composites. The high specific modulus and strength of bast fibers make them an attractive option to replace glass not only in non-structural automotive components, but also in semi-structural and structural components. Significant barriers to insertion of bast fibers in the fiber reinforced automotive composite market include the high moisture uptake of this lignocellulosic material relative to glass and the weak inherent interface between natural fibers and automotive resins. This work seeks to improve the moisture uptake and resin interfacing properties of natural fibers through improved fundamental understanding of fiber physiochemical architecture and development of tailored fiber surface modification strategies.

  4. Railgun Application for High Energy Impact Testing of Nano-Reinforced Kevlar-Based Composite Materials

    NASA Astrophysics Data System (ADS)

    Micheli, D.; Vricella, A.; Pastore, R.; Morles, R. B.; Marchetti, M.

    2013-08-01

    An advanced electromagnetic accelerator, called railgun, has been assembled and tuned in order to perform high energy impact test on layered structures. Different types of layered composite materials have been manufactured and characterized in terms of energy absorbing capability upon impact of metallic bullets fired at high velocity. The composite materials under testing are manufactured by integrating several layers of Kevlar fabric and carbon fiber ply within a polymeric matrix reinforced by carbon nanotubes at 1% of weight percentage. The experimental results show that the railgun-device is a good candidate to perform impact testing of materials in the space debris energy range, and that carbon nanotubes may enhance, when suitably coupled to the composite's matrix, the excellent antiballistic properties of the Kevlar fabrics.

  5. Aging characteristics of short glass fiber reinforced ZA-27 alloy composite materials

    NASA Astrophysics Data System (ADS)

    Sharma, S. C.; Girish, B. M.; Satish, B. M.; Kamath, R.

    1998-12-01

    Aging characteristics of short glass fiber reinforced ZA-27 alloy composite materials have been evaluated in the present study. The liquid metallurgy technique was used to fabricate the composites, in which preheated short glass fibers were introduced into the ZA-27 alloy melt above its liquidus temperature. The aging temperature employed was 125 °C for 6, 12,18, and 24 h. The aged alloy (no fibers) reached the peak hardness after 18 h, while the composites (regardless of filler content) reached the same hardness in 12 h. It is hypothesized that the aging treatment of a composite improves the strength of the interface between the short fibers and the matrix. This is confirmed by the tensile fractograph analysis, which indicates that at a given aging temperature, the composites aged for 18 h exhibit short fibers that remain attached to the metal matrix, while those aged for 6 h undergo debonding.

  6. A study of fiber materials for use in temperature resistant fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Bachowsky, M. J.; Anderson, R. N.

    1982-01-01

    This study has been directed at characterizing the micro-properties of candidate ceramics and glasses for use in making fibers used in fiber reinforced material composites. Particular emphasis has been given into developing techniques to guide the optimization of fiber properties. The Scanning Electron Microscope (SEM) and X-ray Diffractometer (XRD) have been used to help collate the method of synthesis, crystal structure and surface morphology with physical performance parameters. As a result, progress has been made in characterizing such materials. This increased understanding makes the previous research worthy of further study.

  7. On constitutive equations for thermoelastic analysis of fiber-reinforced composites with isotropic matrix material

    NASA Astrophysics Data System (ADS)

    Usal, Melek; Usal, Mustafa Reşit; Esendemir, Ümran

    2013-01-01

    This paper is concerned with developing constitutive equations for the thermoelastic analysis of composites consisting of an isotropic matrix reinforced by independent and inextensible two families of fibers having an arbitrary distribution. The composite medium is assumed to be incompressible, dependent on temperature gradient, and showing linear elastic behavior. The reaction of the composite material subject to external loads is expressed in stress tensor and heat flux vector. The matrix material made of elastic material involving an artificial anisotropy due to fibers reinforcing by arbitrary distributions has been assumed as an isotropic medium. The theory is formulated within the scope of continuum mechanics. As a result of thermodynamic constraints, it has been determined that the stress potential function is dependent on the deformation tensor, the fiber fields vectors and the temperature, while the heat flux vector function is dependent on the deformation tensor, the fiber fields vectors, the temperature and temperature gradient. To determine arguments of the constitutive functionals, findings relating to the theory of invariants have been used as a method because of that isotropy constraint is imposed on the material. The constitutive equations of stress and heat flux vector have been written in terms of different coordinate descriptions.

  8. Composite Intersection Reinforcement

    NASA Technical Reports Server (NTRS)

    Misciagna, David T. (Inventor); Fuhrer, Jessica J. (Inventor); Funk, Robert S. (Inventor); Tolotta, William S. (Inventor)

    2013-01-01

    An assembly and method for manufacturing a composite reinforcement for unitizing a structure are provided. According to one embodiment, the assembly includes a base having a plurality of pins extending outwardly therefrom to define a structure about which a composite fiber is wound to define a composite reinforcement preform. The assembly also includes a plurality of mandrels positioned adjacent to the base and at least a portion of the composite reinforcement preform, and a cap that is positioned over at least a portion of the plurality of mandrels. The cap is configured to engage each of the mandrels to support the mandrels and the composite reinforcement preform during a curing process to form the composite reinforcement.

  9. Composite intersection reinforcement

    NASA Technical Reports Server (NTRS)

    Misciagna, David T. (Inventor); Fuhrer, Jessica J. (Inventor); Funk, Robert S. (Inventor); Tolotta, William S. (Inventor)

    2010-01-01

    An assembly and method for manufacturing a composite reinforcement for unitizing a structure are provided. According to one embodiment, the assembly includes a base having a plurality of pins extending outwardly therefrom to define a structure about which a composite fiber is wound to define a composite reinforcement preform. The assembly also includes a plurality of mandrels positioned adjacent to the base and at least a portion of the composite reinforcement preform, and a cap that is positioned over at least a portion of the plurality of mandrels. The cap is configured to engage each of the mandrels to support the mandrels and the composite reinforcement preform during a curing process to form the composite reinforcement.

  10. Damage threshold study of sonic IR imaging on carbon-fiber reinforced laminated composite materials

    NASA Astrophysics Data System (ADS)

    Han, Xiaoyan; He, Qi; Zhang, Ding; Ashbaugh, Mike; Favro, Lawrence D.; Newaz, Golam; Thomas, Robert L.

    2013-01-01

    Sonic Infrared Imaging, as a young NDE technology, has drawn a lot of attentions due to it's fast, wide-area evaluation capability, and due to its broad applications in different materials such as metal/metal alloy, composites and detection of various types of defects: surface, subsurface, cracks, delaminations/disbonds. Sonic IR Imaging combines pulsed ultrasound excitation and infrared imaging to detect defects in materials. The sound pulse causes rubbing due to non-unison motion between faces of defects, and infrared sensors image the temperature map over the target to identify defects. However, concerns have also been brought up about possible damages which might occur at the contact spots between the ultrasound transducer from the external excitation source and the target materials. In this paper, we present our results from a series of systematically designed experiments on carbon-fiber reinforced laminated composite panels to address the concerns.

  11. Fracture mechanics in fiber reinforced composite materials, taking as examples B/A1 and CRFP

    NASA Technical Reports Server (NTRS)

    Peters, P. W. M.

    1982-01-01

    The validity of linear elastic fracture mechanics and other fracture criteria was investigated with laminates of boron fiber reinforced aluminum (R/A1) and of carbon fiber reinforced epoxide (CFRP). Cracks are assessed by fracture strength Kc or Kmax (critical or maximum value of the stress intensity factor). The Whitney and Nuismer point stress criterion and average stress criterion often show that Kmax of fiber composite materials increases with increasing crack length; however, for R/A1 and CFRP the curve showing fracture strength as a function of crack length is only applicable in a small domain. For R/A1, the reason is clearly the extension of the plastic zone (or the damage zone n the case of CFRP) which cannot be described with a stress intensity factor.

  12. Flexural behavior of reinforced concrete beams strengthened with advanced composite materials

    SciTech Connect

    Shahawy, M.A.; Beitelman, T.

    1996-12-31

    This paper presents the results of a feasibility study to investigate the flexural behavior of structurally damaged reinforced and prestressed concrete members retrofitted with bonded carbon fiber materials. The effect of CFRP laminates, bonded to the soffit of precracked reinforced concrete rectangular and tee beams, is investigated in terms of flexural strength, deflections, cracking behavior and failure modes. The results indicate that strengthening of significantly cracked structural members by bonding Carbon laminates is structurally efficient and that the retrofitted members are restored to stiffness and strength values nearly equal to or greater than those of the original. The results indicate that the retrofitted members maintained adequate structural integrity and composite action at all stages of testing up to failure.

  13. Influence of oxide reinforcement materials on high-temperatue oxidation resistance of Ni sub 3 A1 matrix composites

    SciTech Connect

    Tortorelli, P.F.; DeVan, J.H.; McKamey, C.G.; Howell, M.

    1990-01-01

    The oxidation resistance of Ni{sub 3}Al-based metal matrix composites was studied in high-temperature air under isothermal and thermal cycling conditions as a function of the composition and form of oxide reinforcement material. The incorporation of oxide fibers Al{sub 2}O{sub 3}, HfO{sub 2}, or Al{sub 2}O{sub 3}--ZrO{sub 2} or particles into the Ni{sub 3}Al matrix led to oxidation rates significantly greater than that for the monolithic aluminide. The increase in susceptibility was primarily due to internal oxidation along the fiber- (or particle-) matrix interfaces and depended on the type of reinforcement material and its deposition in the matrix. The results suggest that the choice of reinforcement material and the method of materials processing will be important considerations in the design of oxidation-resistant Ni{sub 3}Al composites. 10 refs, 4 figs.

  14. Analytical modeling in support of the development of fiber reinforced ceramic composite materials for re-heater burners

    SciTech Connect

    Kibler, J.J.; DiPietro, S.G.

    1995-10-01

    Development of Continuous Fiber reinforced Ceramic Composite (CFCC) materials is a process of identifying components which will benefit from CFCC properties, and defining appropriate composite constructions which will provide materials which will meet the structural and thermal requirements of the application. Materials Sciences Corporation (MSC) has been providing analytical support to Textron Specialty Materials in the development of re-heated tubes for metal reheating furnaces. As part of this support, a study has been made of the sensitivity of composite properties to fiber orientation as well as a number of matrix properties which control the stress-strain behavior of the composite.

  15. Fiber reinforced PMR polyimide composites

    NASA Technical Reports Server (NTRS)

    Cavano, P. J.; Winters, W. E.

    1978-01-01

    Commercially obtained PMR-15 polyimide prepregs with S-glass and graphite fiber reinforcements were evaluated along with in-house prepared glass and graphite cloth PMR 2 materials. A novel autoclave approach was conceived and used to demonstrate that both the PMR systems respond to 1.4 MPa (200 psi) autoclave pressures to produce void free composites equivalent to die molded laminates. Isothermal gravimetric analysis and subsequent mechanical property tests indicated that the PMR 2 system was significantly superior in thermo-oxidative stability, and that S-glass reinforcements may contribute to the accelerated degradation of composites at 316 C (600 F) when compared to graphite fiber reinforced composites. Fully reversed bending fatigue experiments were conducted with a type of fixture unused for organic matrix composites. These studies indicated that the graphite fiber composites were clearly superior in fatigue resistance to the glass fiber reinforced material and that PMR matrix composite systems yield performance of the same order as composite materials employing other families of matrices.

  16. Surface emissivity of a reinforced carbon composite material with an oxidation-inhibiting coating

    NASA Technical Reports Server (NTRS)

    Wakefield, R. M.

    1973-01-01

    Total effective emissivity and spectral emissivity over the wavelength range of 0.65 to 6.3 microns were determined for temperatures from 1300 t0 2250 deg K. A multi channel radiometer was used in the arcjet and laboratory tests. The black-body-hole method was used to independently check radiometer results. The results show the silicon-carbide coated reinforced carbon composite material is a nongray radiator. The total effective emissivity and the spectral emissivity at 0.65 micron both decreased with increasing temperature, respectively, from approximately 0.8 to 0.6, and from 0.4 to 0.25, over the temperature range. The emissivity values were the same when the sample was viewed normal to the surface or at a 45 deg angle. Recommended emissivity values are presented.

  17. Surface modification of fiber reinforced polymer composites and their attachment to bone simulating material.

    PubMed

    Hautamäki, M P; Puska, M; Aho, A J; Kopperud, H M; Vallittu, P K

    2013-05-01

    The purpose of this study was to investigate the effect of fiber orientation of a fiber-reinforced composite (FRC) made of poly-methyl-methacrylate (PMMA) and E-glass to the surface fabrication process by solvent dissolution. Intention of the dissolution process was to expose the fibers and create a macroporous surface onto the FRC to enhance bone bonding of the material. The effect of dissolution and fiber direction to the bone bonding capability of the FRC material was also tested. Three groups of FRC specimens (n = 18/group) were made of PMMA and E-glass fiber reinforcement: (a) group with continuous fibers parallel to the surface of the specimen, (b) continuous fibers oriented perpendicularly to the surface, (c) randomly oriented short (discontinuous) fibers. Fourth specimen group (n = 18) made of plain PMMA served as controls. The specimens were subjected to a solvent treatment by tetrahydrofuran (THF) of either 5, 15 or 30 min of time (n = 6/time point), and the advancement of the dissolution (front) was measured. The solvent treatment also exposed the fibers and created a surface roughness on to the specimens. The solvent treated specimens were embedded into plaster of Paris to simulate bone bonding by mechanical locking and a pull-out test was undertaken to determine the strength of the attachment. All the FRC specimens dissolved as function of time, as the control group showed no marked dissolution during the study period. The specimens with fibers along the direction of long axis of specimen began to dissolve significantly faster than specimens in other groups, but the test specimens with randomly oriented short fibers showed the greatest depth of dissolution after 30 min. The pull-out test showed that the PMMA specimens with fibers were retained better by the plaster of Paris than specimens without fibers. However, direction of the fibers considerably influenced the force of attachment. The fiber reinforcement increases significantly the

  18. Mechanical properties of neat polymer matrix materials and their unidirectional carbon fiber-reinforced composites

    NASA Technical Reports Server (NTRS)

    Zimmerman, Richard S.; Adams, Donald F.

    1988-01-01

    The mechanical properties of two neat resin systems for use in carbon fiber epoxy composites were characterized. This included tensile and shear stiffness and strengths, coefficients of thermal and moisture expansion, and fracture toughness. Tests were conducted on specimens in the dry and moisture-saturated states, at temperatures of 23, 82 and 121 C. The neat resins tested were American Cyanamid 1806 and Union Carbide ERX-4901B(MPDA). Results were compared to previously tested neat resins. Four unidirectional carbon fiber reinforced composites were mechanically characterized. Axial and transverse tension and in-plane shear strengths and stiffness were measured, as well as transverse coefficients of thermal and moisture expansion. Tests were conducted on dry specimens only at 23 and 100 C. The materials tested were AS4/3502, AS6/5245-C, T300/BP907, and C6000/1806 unidirectional composites. Scanning electron microscopic examination of fracture surfaces was performed to permit the correlation of observed failure modes with the environmental test conditions.

  19. Alumina-Reinforced Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Bansal, Narottam P.

    2003-01-01

    Alumina-reinforced zirconia composites, used as electrolyte materials for solid oxide fuel cells, were fabricated by hot pressing 10 mol percent yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina particulates and platelets each containing 0 to 30 mol percent alumina. Major mechanical and physical properties of both particulate and platelet composites including flexure strength, fracture toughness, slow crack growth, elastic modulus, density, Vickers microhardness, thermal conductivity, and microstructures were determined as a function of alumina content either at 25 C or at both 25 and 1000 C. Flexure strength and fracture toughness at 1000 C were maximized with 30 particulate and 30 mol percent platelet composites, respectively, while resistance to slow crack growth at 1000 C in air was greater for 30 mol percent platelet composite than for 30 mol percent particulate composites.

  20. Microstructural characterization of fiber-reinforced composites

    SciTech Connect

    Summerscales, J.

    1998-12-31

    In the past 50 years, great progress has been made in developing artificial fiber-reinforced composite materials, generally using filaments with microscopic diameters. An array of reinforcement forms can be used in commercial applications--with the microstructure being a critical factor in realizing the required properties in a material. This book comprehensively examines the application of advanced microstructural characterization techniques to fiber-reinforced composites. Its contents include: (1) flexible textile composite microstructure; (2) 3-D confocal microscopy of glass fiber-reinforced composites; (3) geometric modeling of yarn and fiber assemblies; (4) characterization of yarn shape in woven fabric composites; (5) quantitative microstructural analysis for continuous fiber composites; (6) electron microscopy of polymer composites; (7) micromechanics of reinforcement using laser raman spectroscopy; and (8) acoustic microscopy of ceramic fiber composites.

  1. Feasibility study of prestressed natural fiber-reinforced polylactic acid (pla) composite materials

    NASA Astrophysics Data System (ADS)

    Hinchcliffe, Sean A.

    The feasibility of manufacturing prestressed natural-fiber reinforced biopolymer composites is demonstrated in this work. The objective of this study was to illustrate that the specific mechanical properties of biopolymers can be enhanced by leveraging a combination of additive manufacturing (3D printing) and post-tensioning of continuous natural fiber reinforcement. Tensile and flexural PLA specimens were 3D-printed with and without post-tensioning ducts. The mechanical properties of reinforcing fibers jute and flax were characterized prior to post-tensioning. The effect of matrix cross-sectional geometry and post-tensioning on the specific mechanical properties of PLA were investigated using mechanical testing. Numerical and analytical models were developed to predict the experimental results, which confirm that 3D-printed matrices improve the specific mechanical properties of PLA composites and are further improved via initial fiber prestressing. The results suggest that both additive manufacturing and fiber prestressing represent viable new methods for improving the mechanical performance of natural fiber-reinforced polymeric composites.

  2. Recovery of microfields in fiber-reinforced composite materials: Principles and limitations

    NASA Astrophysics Data System (ADS)

    Ritchey, Andrew J.

    A detailed investigation of the limitations and errors induced by modeling a composite layer composed of straight carbon fibers embedded in an epoxy matrix as an homogenous layer with Cauchy effective moduli is performed. Specifically, the material system studied has IM7 carbon fibers arranged in a square array and bonded together with 8552 epoxy resin (IM7/8552). The finite element method is used to study the effect of free surfaces on the local elastic fields in 0°, 45° and 90° laminae, in which as many as 256 individual fibers are modeled. Through these analyses, it is shown that a micro-boundary layer, analogous to the macro-boundary layer observed in composite laminates, is developed at the microlevel. Additionally, [0/90]s and [90/0]s laminates are studied to investigate the joint action of the macro- and micro-boundary layers. Unless otherwise noted, fiber volume fractions of Vƒ=0.20 and Vƒ=0.65 are selected and the domains are subjected to uniform axial extension. Although this study is done for a highly idealized geometry (i.e. with a single material system and under a simple loading condition) the principles of periodicity, symmetry and antisymmetry used to efficiently perform a direct numerical simulation with a large number of fiber inclusions is general, and can be applied to more complicated geometries and boundary conditions. The purpose of the current work is to be the first step in a building block approach to understanding the interaction of multiple scales in fiber-reinforced composites through direct numerical simulations. The main part of the current manuscript focuses on the characterization of a micro-boundary layer that develops in fiber reinforced composite layers. This phenomena results from the changing constraints on the constituent phases as a result of discontinuities, such as free surfaces or ply interfaces. The effect is most pronounced in laminae that have a fiber termination intersecting a free surface, and appears to be

  3. Buckling of Carbon Nanotube-Reinforced Polymer Laminated Composite Materials Subjected to Axial Compression and Shear Loadings

    NASA Technical Reports Server (NTRS)

    Riddick, J. C.; Gates, T. S.; Frankland, S.-J. V.

    2005-01-01

    A multi-scale method to predict the stiffness and stability properties of carbon nanotube-reinforced laminates has been developed. This method is used in the prediction of the buckling behavior of laminated carbon nanotube-polyethylene composites formed by stacking layers of carbon nanotube-reinforced polymer with the nanotube alignment axes of each layer oriented in different directions. Linking of intrinsic, nanoscale-material definitions to finite scale-structural properties is achieved via a hierarchical approach in which the elastic properties of the reinforced layers are predicted by an equivalent continuum modeling technique. Solutions for infinitely long symmetrically laminated nanotube-reinforced laminates with simply-supported or clamped edges subjected to axial compression and shear loadings are presented. The study focuses on the influence of nanotube volume fraction, length, orientation, and functionalization on finite-scale laminate response. Results indicate that for the selected laminate configurations considered in this study, angle-ply laminates composed of aligned, non-functionalized carbon nanotube-reinforced lamina exhibit the greatest buckling resistance with 1% nanotube volume fraction of 450 nm uniformly-distributed carbon nanotubes. In addition, hybrid laminates were considered by varying either the volume fraction or nanotube length through-the-thickness of a quasi-isotropic laminate. The ratio of buckling load-to-nanotube weight percent for the hybrid laminates considered indicate the potential for increasing the buckling efficiency of nanotube-reinforced laminates by optimizing nanotube size and proportion with respect to laminate configuration.

  4. Laser-Generated Lamb Waves Propagation in Multilayered Plates Composed of Viscoelastic Fiber-reinforced Composite Materials

    NASA Astrophysics Data System (ADS)

    Sun, Hong-xiang; Zhang, Shu-yi; Yuan, Shou-qi; Guan, Yi-jun; Ge, Yong

    2016-07-01

    The propagation characteristics of laser-generated Lamb waves in multilayered fiber-reinforced composite plates with different fiber orientations and number of layers have been investigated quantitatively. Considering the viscoelasticity of the composite materials, we have set up finite element models for simulating the laser-generated Lamb waves in two types of the multilayered composite plates. In the first type, different fiber orientations are adopted. In the second one, different number of layers are considered. The results illustrate the occurrence of attenuation and dispersion, which is induced by the viscoelasticity and multilayer structure, respectively.

  5. Preliminary development of a fundamental analysis model for crack growth in a fiber reinforced composite material

    NASA Technical Reports Server (NTRS)

    Kanninen, M. F.; Rybicki, E. F.; Griffith, W. I.

    1977-01-01

    A mathematical model for the strength of fiber reinforced composites containing specific flaws is described. The approach is to embed a local heterogeneous region surrounding the crack tip in an anisotropic elastic continuum. By consideration of the individual failure events activated near the flaw tip, a strength prediction can be made from basic properties of the composite constituents. Computations for arbitrary flaw size and orientation have been performed for unidirectional composites with linear elastic-brittle constituent behavior. The mechanical properties were those of graphite epoxy. With the rupture properties arbitrarily varied to test the capability of the model to reflect real fracture modes in fiber composites, it is shown that fiber breakage, matrix crazing, crack bridging, matrix-fiber debonding, and axial splitting all can occur during gradually increasing load prior to catastrophic fracture. Qualitative comparisons with experimental results on edge-notched unidirectional graphite epoxy specimens have also been made.

  6. Effect of Sericin on Mechanical Behavior of Composite Material Reinforced by Silk Woven Fabric

    NASA Astrophysics Data System (ADS)

    Kimura, Teruo; Ino, Haruhiro; Hanada, Koji; Katori, Sigetaka

    Recent, attention has been given to shift from glass fibers and carbon fibers to natural fibers for FRP composites for the goal of protecting the environment. This paper concerned with the application of silk fabric for composite materials. Polypropylene (PP) was used for the matrix material and the silk fabric composites were molded using a compression molding method. Especially, the effect of sericin on mechanical behaviors of composite materials was discussed. Good adhesion between silk and PP was obtained by removing the sericin existing around the fibroin. The tensile modulus of composite decreased with decreasing the sericin because of the flexibility of silk fibers without sericin. In particular, the higher Izod impact value was obtained for the composites containing the silk fibers without sericin.

  7. Non-destructive evaluation of porosity and its effect on mechanical properties of carbon fiber reinforced polymer composite materials

    NASA Astrophysics Data System (ADS)

    Bhat, M. R.; Binoy, M. P.; Surya, N. M.; Murthy, C. R. L.; Engelbart, R. W.

    2012-05-01

    In this work, an attempt is made to induce porosity of varied levels in carbon fiber reinforced epoxy based polymer composite laminates fabricated using prepregs by varying the fabrication parameters such as applied vacuum, autoclave pressure and curing temperature. Different NDE tools have been utilized to evaluate the porosity content and correlate with measurable parameters of different NDE techniques. Primarily, ultrasonic imaging and real time digital X-ray imaging have been tried to obtain a measurable parameter which can represent or reflect the amount of porosity contained in the composite laminate. Also, effect of varied porosity content on mechanical properties of the CFRP composite materials is investigated through a series of experimental investigations. The outcome of the experimental approach has yielded interesting and encouraging trend as a first step towards developing an NDE tool for quantification of effect of varied porosity in the polymer composite materials.

  8. Modelling of fracture phenomenon in case of composite materials reinforced with short carbon fibers

    NASA Astrophysics Data System (ADS)

    Caliman, R.

    2015-11-01

    The research work presented in this paper describes the composite materials in terms of formation and propagation of cracks using an algorithm that imposes disproportional loads to composite samples. The required parameters that describe the composites fracture demand inputs as: load intensity, geometry features and relative loading direction. In order to obtain reliable results, it should be a good correlation between the model which describes the facture propagation, the composition of the material and the structural homogeneity. The presented study is using a Functionally Graded Material with local homogeneity in fracture area, and a numerical model based on integration of interactions (Mori - Tanaka method). The parameters that describes the fracture behaviour, includes a factor of stress intensity which is important for establish the fracture direction. The model used in simulations is considering a composite sample with rectangular shape and 6 mm thickness. The sample is loaded with predefined stress σct (MPa) above and under the fracture line. σct represents the critical stress able to lead to fracture propagation. The main objective of this research work it was to generate a numerical model which describes the fracture behaviour of a composite material. The obtained model and its accuracy to describe the fracture behaviour of a composite material is presented in the final part of this paper.

  9. Self-sealing of thermal fatigue and mechanical damage in fiber-reinforced composite materials

    NASA Astrophysics Data System (ADS)

    Moll, Jericho L.

    Fiber reinforced composite tanks provide a promising method of storage for liquid oxygen and hydrogen for aerospace applications. The inherent thermal fatigue of these vessels leads to the formation of microcracks, which allow gas phase leakage across the tank walls. In this dissertation, self-healing functionality is imparted to a structural composite to effectively seal microcracks induced by both mechanical and thermal loading cycles. Two different microencapsulated healing chemistries are investigated in woven glass fiber/epoxy and uni-weave carbon fiber/epoxy composites. Self-healing of mechanically induced damage was first studied in a room temperature cured plain weave E-glass/epoxy composite with encapsulated dicyclopentadiene (DCPD) monomer and wax protected Grubbs' catalyst healing components. A controlled amount of microcracking was introduced through cyclic indentation of opposing surfaces of the composite. The resulting damage zone was proportional to the indentation load. Healing was assessed through the use of a pressure cell apparatus to detect nitrogen flow through the thickness direction of the damaged composite. Successful healing resulted in a perfect seal, with no measurable gas flow. The effect of DCPD microcapsule size (51 microm and 18 microm) and concentration (0--12.2 wt%) on the self-sealing ability was investigated. Composite specimens with 6.5 wt% 51 microm capsules sealed 67% of the time, compared to 13% for the control panels without healing components. A thermally stable, dual microcapsule healing chemistry comprised of silanol terminated poly(dimethyl siloxane) plus a crosslinking agent and a tin catalyst was employed to allow higher composite processing temperatures. The microcapsules were incorporated into a satin weave E-glass fiber/epoxy composite processed at 120°C to yield a glass transition temperature of 127°C. Self-sealing ability after mechanical damage was assessed for different microcapsule sizees (25 microm and 42

  10. Improvement and optimization of internal damping in fiber-reinforced composite materials. Final report, June 1983-November 1985

    SciTech Connect

    Gibson, R.F.; Suarez, S.A.

    1986-03-03

    The objective of this research were to study the effects of such parameters as fiber aspect ratio, fiber orientation and fiber/matrix properties on damping in fiber-reinforced polymer composites. These objectives were to be met by using both experimental and analytical approaches. The development of improved techniques for fabrication and testing of specimens and the development of relatively simple design equations for prediction of damping were desirable goals that were also met. Two new computer-aided testing techniques based on the impulse frequency-response approach were developed. Specimens of graphite/epoxy, boron/epoxy and Kevlar aramid/epoxy were fabricated by using an autoclave-style press cure which was developed specifically for this program. Although a number of parameters were studied, the emphasis was on the influence of fiber length, fiber orientation, and fiber material on damping of polymer composites. Experimental results show that, as predicted, very low fiber aspect ratios are required to produce significant improvements in damping. Of the three fiber types tested, the Kevlar aramid fiber composite was found to have much better damping than graphite or boron fiber composites. Measurements and predictions also indicate that the control of fiber orientation in a continuous fiber reinforced laminate may be a better approach to the improvement of damping than the control of fiber aspect ratio.

  11. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.; Prewo, K. M.; Thompson, E. R.

    1978-01-01

    A composite that can be used at temperatures up to 875 K with mechanical properties equal or superior to graphite fiber reinforced epoxy composites is presented. The composite system consist of graphite fiber, uniaxially or biaxially, reinforced borosilicate glass. The mechanical and thermal properties of such a graphite fiber reinforced glass composite are described, and the system is shown to offer promise as a high performance structural material. Specific properties that were measured were: a modified borosilicate glass uniaxially reinforced by Hercules HMS graphite fiber has a three-point flexural strength of 1030 MPa, a four-point flexural strength of 964 MPa, an elastic modulus of 199 GPa and a failure strain of 0.0052. The preparation and properties of similar composites with Hercules HTS, Celanese DG-102, Thornel 300 and Thornel Pitch graphite fibers are also described.

  12. Analysis of Graphite-Reinforced Cementitious Composites

    NASA Technical Reports Server (NTRS)

    Vaughan, R. E.

    2002-01-01

    Strategically embedding graphite meshes in a compliant cementitious matrix produces a composite material with relatively high tension and compressive properties as compared to steel-reinforced structures fabricated from a standard concrete mix. Although these composite systems are somewhat similar, the methods used to analyze steel-reinforced composites often fail to characterize the behavior of their more advanced graphite-reinforced counterparts. This Technical Memorandum describes some of the analytical methods being developed to determine the deflections and stresses in graphite-reinforced cementitious composites. It is initially demonstrated that the standard transform section method fails to provide accurate results when the elastic moduli ratio exceeds 20. An alternate approach is formulated by using the rule of mixtures to determine a set of effective material properties for the composite. Tensile tests are conducted on composite samples to verify this approach. When the effective material properties are used to characterize the deflections of composite beams subjected to pure bending, an excellent agreement is obtained. Laminated composite plate theory is investigated as a means for analyzing even more complex composites, consisting of multiple graphite layers oriented in different directions. In this case, composite beams are analyzed using the laminated composite plate theory with material properties established from tensile tests. Then, finite element modeling is used to verify the results. Considering the complexity of the samples, a very good agreement is obtained.

  13. Mechanical properties of several neat polymer matrix materials and unidirectional carbon fiber-reinforced composites

    NASA Technical Reports Server (NTRS)

    Coguill, Scott L.; Adams, Donald F.

    1989-01-01

    The mechanical and physical properties of three neat matrix materials, i.e., PEEK (polyetheretherketone) thermoplastic, Hexcel F155 rubber-toughened epoxy and Hercules 8551-7 rubber-toughened epoxy, were experimentally determined. Twelve unidirectional carbon fiber composites, incorporating matrix materials characterized in this or earlier studies (with one exception; the PISO(sub 2)-TPI matrix itself was not characterized), were also tested. These composite systems included AS4/2220-1, AS4/2220-3, T500/R914, IM6/HX1504, T300/4901A (MDA), T700/4901A (MDA), T300/4901B (MPDA), T700/4901B (MPDA), APC2 (AS4/PEEK, ICI), APC2 (AS4/PEEK, Langley Research Center), AS4/8551-7, and AS4/PISO(sub 2)-TPI. For the neat matrix materials, the tensile, shear, fracture toughness, coefficient of thermal expansion, and coefficient of moisture expansion properties were measured as a function of both temperature and moisture content. For the unidirectional composites, axial and transverse tensile, longitudinal shear, coefficient of thermal expansion, and coefficient of moisture expansion properties were determined, at room temperature and 100 C.

  14. The development, fabrication, and material characterization of polypropylene composites reinforced with carbon nanofiber and hydroxyapatite nanorod hybrid fillers

    PubMed Central

    Liao, Cheng Zhu; Wong, Hoi Man; Yeung, Kelvin Wai Kwok; Tjong, Sie Chin

    2014-01-01

    This study focuses on the design, fabrication, microstructural and property characterization, and biocompatibility evaluation of polypropylene (PP) reinforced with carbon nanofiber (CNF) and hydroxyapatite nanorod (HANR) fillers. The purpose is to develop advanced PP/CNF–HANR hybrids with good mechanical behavior, thermal stability, and excellent biocompatibility for use as craniofacial implants in orthopedics. Several material-examination techniques, including X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, tensile tests, and impact measurement are used to characterize the microstructural, mechanical, and thermal properties of the hybrids. Furthermore, osteoblastic cell cultivation and colorimetric assay are also employed for assessing their viability on the composites. The CNF and HANR filler hybridization yields an improvement in Young’s modulus, impact strength, thermal stability, and biocompatibility of PP. The PP/2% CNF–20% HANR hybrid composite is found to exhibit the highest elastic modulus, tensile strength, thermal stability, and biocompatibility. PMID:24648729

  15. Creep deformation characteristics of ductile discontinuous fiber reinforced composites

    SciTech Connect

    Biner, S.B.

    1993-10-01

    Role of material parameters and geometric parameters of ductile reinforcing phase on the creep deformation behavior of 20% discontinuously reinforced composite was numerically investigated including debonding and pull-out mechanisms. Results indicate that for rigidly bonded interfaces, the creep rate of the composite is not significantly influenced by the material properties and geometric parameters of the ductile reinforcing phase due to development of large hydrostatic stress and constrained deformation in the reinforcement. For debonding interfaces, the geometric parameters of the reinforcing phase are important; however, event with very weak interfacial behavior low composite creep rates can be achieved by suitable selection of the geometric parameters of the ductile reinforcing phase.

  16. Damping behavior of Discontinuous Fiber Reinforced Thermoplastic Composites

    NASA Astrophysics Data System (ADS)

    Haldar, Amit Kumar; Aggarwal, Ishan; Batra, N. K.

    2010-11-01

    Discontinuous fiber reinforced composites are being used in many antivibration applications due to their time and temperature dependent specific mechanical properties. For utilization of this material to specific engineering applications there is a need to understand the damping behavior of composites under dynamic loading. For this work, unreinforced and 20% long and short reinforced glass fiber polypropylene composite materials were tested for free transverse vibration damping characteristics under static as well as fatigue loading conditions. The damping characteristics are quantified by decay pattern and natural frequency. Presence of reinforced fibers increases the damping capacity. Among reinforcements, short fiber reinforced polypropylene shows increased damping capacity then long glass fiber reinforced polypropylene.

  17. Fiber-Reinforced Composite Foam

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A two-phase method for making fiber-reinforced compositions was developed to achieve uniform fiber dispersion in a composite matrix. The first phase involved mixing together water, fibers, and a portion of a fiber dispersant to form a viscous composition. The high viscosity imparted by the dispersa...

  18. Matrix toughness, long-term behavior, and damage tolerance of notched graphite fiber-reinforced composite materials

    NASA Technical Reports Server (NTRS)

    Bakis, C. E.; Simonds, R. A.; Stinchcomb, W. W.; Vick, L. W.

    1990-01-01

    The long-term behavior of notched graphite-fiber-reinforced composite laminates with brittle or tough matrix materials and different fiber architectures was investigated using damage measurements and stiffness change, residual strength, and life data. The fiber/matrix materials included T300/5208, AS4/3501-6, AS4/1808, AS4/PEEK, and C3000/PMR-15 matrices and unidirectional tape and woven cloth fiber architectures. Results of damage evaluation and of residual strength measurements during the fatigue damage development showed that the long-term behavior and damage tolerance are controlled by a number of interacting factors such as the matrix toughness, fiber architecture, loading levels, and damage types and distributions.

  19. The Comparison of Shear Bond Strength Between Fibre Reinforced Composite Posts with Three Different Composite Core Materials – An In vitro Study

    PubMed Central

    Anche, Sampath; Kakarla, Pranitha; Kadiyala, Krishna Kishore; Sreedevi, B.; Chiramana, Sandeep; Dev J., Ravi Rakesh; Manne, Sanjay Dutt; G., Deepthi

    2014-01-01

    Aim: The aim of this study is to compare the shear bond strength between fiber reinforced composite post with three different composite core materials. Materials and Methods: The materials used for the study were: 30 maxillary central incisors, pre fabricated fiber reinforced composite post (postec plus posts), Multi-core heavy body, Ti-core, Fluoro-core, Etchant gel, Silane coupling agent, Dentin bonding agent, Standardized gutta percha points, Rely-X dual cure composite resin. A total of 30 human maxillary central incisor were selected for this study. They were divided into three groups of 10 specimens each namely A, B and C. Results: The results obtained were analyzed by using one way analysis (ANOVA) and Tukey Honestly Significant Difference and they showed highest mean shear bond strength for group C when compared with group A and group B. There is no significant difference in the shear bond strength values between group A and group B. Conclusion: The teeth restored with multicore HB showed highest shear bond strength. The teeth restored with Fluoro core showed lowest shear bond strength. No statistically significant difference exists between the shear bond strength values between Ti-core and Fluoro-core. PMID:24596784

  20. Compressive strength of fiber reinforced composite materials. [composed of boron and epoxy

    NASA Technical Reports Server (NTRS)

    Davis, J. G., Jr.

    1974-01-01

    Results of an experimental and analytical investigation of the compressive strength of unidirectional boron-epoxy composite material are presented. Observation of fiber coordinates in a boron-epoxy composite indicates that the fibers contain initial curvature. Combined axial compression and torsion tests were conducted on boron-epoxy tubes, and it was shown that the shear modulus is a function of axial compressive stress. An analytical model which includes initial curvature in the fibers and permits an estimate of the effect of curvature on compressive strength is proposed. Two modes of failure which may result from the application of axial compressive stress are analyzed, delamination and shear instability. Based on tests and analysis, failure of boron-epoxy under axial compressive load is due to shear instability.

  1. Studies of Matrix/Fiber Reinforced Composite Materials for the High Speed Research (HSR) Program

    NASA Technical Reports Server (NTRS)

    Orwoll, Robert A.

    1998-01-01

    The research on the curing mechanism of the phenylethynyl terminated imide matrix resins was the primary focus of this research. The ability to process high performance polymers into useful adhesives and high quality composites has been significantly advanced by synthetic techniques in which oligomers terminated with reactive groups cure or crosslink at elevated temperature after the article has been fabricated. The research used a variety of analytical techniques. Many stable products were isolated, and attempts at identification were made. This research was intended to provide fundamental insight into the molecular structure of these new engineering materials.

  2. Computer modeling of the mechanical behavior of composites -- Interfacial cracks in fiber-reinforced materials

    SciTech Connect

    Schmauder, S.; Haake, S. |; Mueller, W.H. |

    1996-06-15

    Computer modeling of materials and especially modeling the mechanical behavior of composites became increasingly popular in the past few years. Among them are examples of micromechanical modeling of real structures as well as idealized model structures of linear elastic and elasto-plastic material response. In this paper, Erdogan`s Integral Equation Method (IEM) is chosen as an example for a powerful method providing principle insight into elastic fracture mechanical situations. IEM or, alternatively, complex function techniques sometimes even allow for deriving analytical solutions such as in the case of a circumferential crack along a fiber/matrix interface. The analytical formulae of this interface crack will be analyzed numerically and typical results will be presented graphically.

  3. Carbon Nanotubes Reinforced Composites for Biomedical Applications

    PubMed Central

    Wang, Wei; Zhu, Yuhe; Liao, Susan; Li, Jiajia

    2014-01-01

    This review paper reported carbon nanotubes reinforced composites for biomedical applications. Several studies have found enhancement in the mechanical properties of CNTs-based reinforced composites by the addition of CNTs. CNTs reinforced composites have been intensively investigated for many aspects of life, especially being made for biomedical applications. The review introduced fabrication of CNTs reinforced composites (CNTs reinforced metal matrix composites, CNTs reinforced polymer matrix composites, and CNTs reinforced ceramic matrix composites), their mechanical properties, cell experiments in vitro, and biocompatibility tests in vivo. PMID:24707488

  4. Fiber reinforced composite resin systems.

    PubMed

    Giordano, R

    2000-01-01

    The Targis/Vectris and Sculpture/FibreKor systems were devised to create a translucent maximally reinforced resin framework for fabrication of crowns, bridges, inlays, and onlays. These materials are esthetic, have translucency similar to castable glass-ceramics such as OPC and Empress, and have fits that are reported to be acceptable in clinical and laboratory trials. These restorations rely on proper bonding to the remaining tooth structure; therefore, careful attention to detail must be paid to this part of the procedure. Cementation procedures should involve silane treatment of the cleaned abraded internal restoration surface, application of bonding agent to the restoration as well as the etched/primed tooth, and finally use of a composite resin. Each manufacturer has a recommended system which has been tested for success with its resin system. These fiber reinforced resins are somewhat different than classical composites, so not all cementation systems will necessarily work with them. Polishing of the restoration can be accomplished using diamond or alumina impregnated rubber wheels followed by diamond paste. The glass fibers can pose a health risk. They are small enough to be inhaled and deposited in the lungs, resulting in a silicosis-type problem. Therefore, if fibers are exposed and ground on, it is extremely important to wear a mask. Also, the fibers can be a skin irritant, so gloves also should be worn. If the fibers become exposed intraorally, they can cause gingival inflammation and may attract plaque. The fibers should be covered with additional composite resin. If this cannot be accomplished, the restoration should be replaced. The bulk of these restorations are formed using a particulate filled resin, similar in structure to conventional composite resins. Therefore, concerns as to wear resistance, color stability, excessive expansion/contraction, and sensitivity remain until these materials are proven in long-term clinical trials. They do hold the

  5. Thick fibrous composite reinforcements behave as special second-gradient materials: three-point bending of 3D interlocks

    NASA Astrophysics Data System (ADS)

    Madeo, Angela; Ferretti, Manuel; dell'Isola, Francesco; Boisse, Philippe

    2015-08-01

    In this paper, we propose to use a second gradient, 3D orthotropic model for the characterization of the mechanical behavior of thick woven composite interlocks. Such second-gradient theory is seen to directly account for the out-of-plane bending rigidity of the yarns at the mesoscopic scale which is, in turn, related to the bending stiffness of the fibers composing the yarns themselves. The yarns' bending rigidity evidently affects the macroscopic bending of the material and this fact is revealed by presenting a three-point bending test on specimens of composite interlocks. These specimens differ one from the other for the different relative direction of the yarns with respect to the edges of the sample itself. Both types of specimens are independently seen to take advantage of a second-gradient modeling for the correct description of their macroscopic bending modes. The results presented in this paper are essential for the setting up of a correct continuum framework suitable for the mechanical characterization of composite interlocks. The few second-gradient parameters introduced by the present model are all seen to be associated with peculiar deformation modes of the mesostructure (bending of the yarns) and are determined by inverse approach. Although the presented results undoubtedly represent an important step toward the complete characterization of the mechanical behavior of fibrous composite reinforcements, more complex hyperelastic second-gradient constitutive laws must be conceived in order to account for the description of all possible mesostructure-induced deformation patterns.

  6. Advanced X-Ray Inspection of Reinforced Carbon Composite Materials on the Orbiter Leading Edge Structural Subsystem (LESS)

    NASA Technical Reports Server (NTRS)

    Hernandez, Jose M.; Berry, Robert F.; Osborn, Robin; Bueno, Clifford; Osterlitz, Mark; Mills, Richard; Morris, Philip; Phalen, Robert; McNab, Jim; Thibodeaux, Tahanie; Thompson, Kyle

    2004-01-01

    The post return-to-flight (RTF) inspection methodology for the Orbiter Leading Edge Structural Subsystem (LESS) is currently being defined. Numerous NDT modalities and techniques are being explored to perform the flight-to-flight inspections of the reinforced carbon/carbon (RCC) composite material for impact damage, general loss of mass in the bulk layers, or other anomalous conditions that would pose risk to safe return upon re-entry. It is possible to have an impact upon ascent that is not visually observable on the surface, yet causes internal damage. Radiographic testing may be a useful NDT technique for such occurrences. The authors have performed radiographic tests on full-sized mock samples of LESS hardware with embedded image quality phantoms. Digitized radiographic film, computed radiography and flat panel digital real-time radiography was acquired using a GE Eresco 200 x-ray tube, and Se-75 and Yb-169 radioisotopes.

  7. Tungsten fiber reinforced FeCralY: A first generation composite turbine blade material

    NASA Technical Reports Server (NTRS)

    Petrasek, D. W.; Winsa, E. A.; Westfall, L. J.; Signorelli, R. A.

    1979-01-01

    Tungsten-fiber/FeCrAlY (W/FeCrAlY) was identified as a promising aircraft engine, first generation, turbine blade composite material. Based on available data, W/FeCrAlY should have the stress-rupture, creep, tensile, fatigue, and impact strengths required for turbine blades operating from 1250 to 1370 K. It should also have adequate oxidation, hot corrosion, and thermal cycling damage resistance as well as high thermal conductivity. Concepts for potentially low cost blade fabrication were developed. These concepts were used to design a first stage JT9D convection cooled turbine blade having a calculated 50 K use-temperature advantage over the directionally solidified superalloy blade.

  8. A Strategy to Support Design Processes for Fibre Reinforced Thermoset Composite Materials

    NASA Astrophysics Data System (ADS)

    Gascons, Marc; Blanco, Norbert; Mayugo, Joan Andreu; Matthys, Koen

    2012-06-01

    The concept stage in the design for a new composite part is a time when several fundamental decisions must be taken and a considerable amount of the budget is spent. Specialized commercial software packages can be used to support the decision making process in particular aspects of the project (e.g. material selection, numerical analysis, cost prediction,...). However, a complete and integrated virtual environment that covers all the steps in the process is not yet available for the composite design and manufacturing industry. This paper does not target the creation of such an overarching virtual tool, but instead presents a strategy that handles the information generated in each step of the design process, independently of the commercial packages used. Having identified a suitable design parameter shared in common with all design steps, the proposed strategy is able to evaluate the effects of design variations throughout all the design steps in parallel. A case study illustrating the strategy on an industrial part is presented.

  9. Inorganic nanotubes reinforced polyvinylidene fluoride composites as low-cost electromagnetic interference shielding materials.

    PubMed

    Eswaraiah, Varrla; Sankaranarayanan, Venkataraman; Ramaprabhu, Sundara

    2011-01-01

    Novel polymer nanocomposites comprising of MnO2 nanotubes (MNTs), functionalized multiwalled carbon nanotubes (f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f-MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10-16S/m to 4.5 × 10-5S/m (3.2 × 10-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region. PMID:21711633

  10. Inorganic nanotubes reinforced polyvinylidene fluoride composites as low-cost electromagnetic interference shielding materials

    PubMed Central

    2011-01-01

    Novel polymer nanocomposites comprising of MnO2 nanotubes (MNTs), functionalized multiwalled carbon nanotubes (f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f-MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10-16S/m to 4.5 × 10-5S/m (3.2 × 10-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region. PMID:21711633

  11. Inorganic nanotubes reinforced polyvinylidene fluoride composites as low-cost electromagnetic interference shielding materials

    NASA Astrophysics Data System (ADS)

    Eswaraiah, Varrla; Sankaranarayanan, Venkataraman; Ramaprabhu, Sundara

    2011-12-01

    Novel polymer nanocomposites comprising of MnO2 nanotubes (MNTs), functionalized multiwalled carbon nanotubes ( f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f-MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10-16S/m to 4.5 × 10-5S/m (3.2 × 10-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/ f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region.

  12. Novel methods and self-reinforced composite materials for assessment and prevention of mechanically assisted corrosion in modular implants

    NASA Astrophysics Data System (ADS)

    Ouellette, Eric S.

    Novel methods for assessing the electrochemical and micromechanical performance of modular tapers were evaluated, and self-reinforced composite materials were developed for their potential to prevent the onset of mechanically assisted corrosion in modular taper devices. A study of the seating and taper locking mechanics of modular taper samples was conducted, and the effect on taper engagement strength of seating load, loading rate, taper moisture, and taper design/material combination was studied. The load-displacement behavior was captured during seating, and the subsequent pull off load was correlated to seating displacement, seating energy, and seating load. The primary factor affecting taper engagement strength was seating load, and loading rate and design/material factors did not have a significant impact on the quality of the taper engagement. Next, the effect of variation of 7 different design, material, and surgical factors on the fretting corrosion and micromechanical behavior during incremental cyclic fretting corrosion testing was examined using a design of experiments matrix. Seating load and head offset length were the most influential factors affecting fretting corrosion, with low seating loads and high head offsets giving rise to increased currents during sequentially incremented cyclic loads. Poly(ether ether ketone) (PEEK) fibers were produced, and the effects of varying draw down ratio, molecular weight, and post-spinning treatment on the structural and mechanical properties of the fibers were studied. Highly drawn fibers showed the highest increase in molecular orientation and mechanical properties. PEEK fibers were then utilized in the design and fabrication of self-reinforced composite PEEK (SRC-PEEK) thin film composites, and self-reinforced composite ultra-high molecular weight polyethylene (SRC-PE) produced from Spectra fiber was also introduced. Pin on disk studies were employed to understand the potential of both of these SRC materials to

  13. Sapphire reinforced alumina matrix composites

    NASA Technical Reports Server (NTRS)

    Jaskowiak, Martha H.; Setlock, John A.

    1994-01-01

    Unidirectionally reinforced A1203 matrix composites have been fabricated by hot pressing. Approximately 30 volume % of either coated or uncoated sapphire fiber was used as reinforcement. Unstabilized ZrO2 was applied as the fiber coating. Composite mechanical behavior was analyzed both after fabrication and after additional heat treatment. The results of composite tensile tests were correlated with fiber-matrix interfacial shear strengths determined from fiber push-out tests. Substantially higher strength and greater fiber pull-out were observed for the coated fiber composites for all processing conditions studied. The coated fiber composites retained up to 95% and 87% of their as-fabricated strength when heat treated at 14000C for 8 or 24 hours, respectively. Electron microscopy analysis of the fracture surfaces revealed extensive fiber pull-out both before and after heat treatment.

  14. Development of an Iron-Based Hardfacing Material Reinforced with Fe-(TiW)C Composite Powder

    NASA Astrophysics Data System (ADS)

    Correa, E. O.; Alcantara, N. G.; Tecco, D. G.; Kumar, R. V.

    2007-05-01

    The objective of this work is to investigate the correlation of microstructure with wear resistance in a hardfacing material reinforced with Fe-(TiW)C composite powder particles. This material was designed for cladding components subjected to highly abrasive conditions and was deposited on a low-carbon steel substrate by open arc welding. The theoretical and experimental work undertaken includes solidification study, microstructural characterization, and abrasive wear testing. Microstructural analysis of the hardfaced top layer of the alloy showed the presence of TiWC carbide particles and TiNbC carbides randomly distributed in a eutectic mixture matrix γ/M7C3 containing primary austenite dendrites. Microstructural examinations also showed that hard and fine spherulitic carbides, in which a Ti-rich MC carbide core was encircled by MC carbide enriched with Nb and W, were homogeneously distributed in the matrix. The energy-dispersive spectroscopy (EDS) mapping of spherulitic carbides showed that the any added Nb replaced a significant part of W in the Fe-(TiW)C powder, and W preferentially partitioned into other carbides and matrix during solidification. Abrasion test results showed that the preceding carbides improve the wear resistance of the hardfacing material in comparison with conventional Fe-Cr-C and Fe-Cr-C-Nb alloys, especially under high stress conditions.

  15. Resonant Ultrasound Spectroscopy, as Applied to Nondestructive Evaluation and Characterization of Carbon Fiber Reinforced Epoxy Composite Materials.

    NASA Astrophysics Data System (ADS)

    Whitney, Timothy Marvin

    1996-08-01

    Resonant ultrasound spectroscopy (RUS) can be an elegantly simple nondestructive evaluation tool. The resonance spectrum of any specimen is dependent on, and sensitive at ppm levels to, its density, geometry, elastic and thermal properties, and boundary conditions. The measurement of spectrum is fast, taking between 15 and 90 seconds with state-of-the-art instrumentation, making it appropriate for following properties as a function of temperature. Parts per million changes in specimen density, geometry, elastic moduli, temperature, and boundary conditions are detected with RUS. A novel apparatus is presented for driving and detecting the mechanical resonance of objects with major dimensions ranging from 0.1 cm to 33 cm. The noise floor of the apparatus is characterized using a high Q titanium alloy and a low Q graphite/epoxy composite. The apparatus is used to measure the amplitude/frequency resonance spectra of right rectangular parallelepiped (RRP) specimens of four different lay-ups of AS4/3501-6 carbon fiber reinforced epoxy (CFRE) composite material at room temperature and at one degree C intervals between -177^circC and 25 ^circC. It is important to know the mechanical properties of this material at low temperatures for underwater, polar, and space applications. The temperature dependence of the second order elastic moduli are calculated from the resonance spectra of the AS4/3501-6 RRPs. High power ultrasound is used to enhance the cure of AS4/3501-6 CFRE composite. Composite panels are insonified through the caul plate, by a high power ultrasonic horn, while curing. Stiffness enhancements of five percent are observed. The resonance spectrum of a steel caul plate is used to monitor the degree of cure of AS4/3501-6 CFRE composite panels in real time. Because the curing composite acts to change the boundary conditions, the resonance spectrum changes as the composite cures. RUS is used to screen a variety of high precision engineered parts for mechanical defects

  16. Ethanol production waste as rubber composite filler: examining the pyrolysis of dried distillers grains and other dry milling byproducts as potential rubber reinforcement materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The current push for corn-based ethanol is creating a large surplus of affordable by-products that can potentially serve as filler material for rubber composites. Biomaterial fillers can help replace carbon black and reduce dependence on petroleum. This research examines the reinforcement behavior...

  17. Analysis of Graphite Reinforced Cementitious Composites

    NASA Technical Reports Server (NTRS)

    Vaughan, Robert E.; Gilbert, John A.; Spanyer, Karen (Technical Monitor)

    2001-01-01

    This paper describes analytical methods that can be used to determine the deflections and stresses in highly compliant graphite-reinforced cementitious composites. It is demonstrated that the standard transform section fails to provide accurate results when the elastic modulus ratio exceeds 20. So an alternate approach is formulated by using the rule of mixtures to determine a set of effective material properties for the composite. Tensile tests are conducted on composite samples to verify this approach; and, when the effective material properties are used to characterize the deflections of composite beams subject to pure bending, an excellent agreement is obtained. Laminated composite plate theory is also investigated as a means for analyzing even more complex composites, consisting of multiple graphite layers oriented in different directions. In this case, composite beams are analyzed by incorporating material properties established from tensile tests. Finite element modeling is used to verity the results and, considering the complexity of the samples, a very good agreement is obtained.

  18. The mechanics of delamination in fiber-reinforced composite materials. I - Stress singularities and solution structure

    NASA Technical Reports Server (NTRS)

    Wang, S. S.; Choi, I.

    1983-01-01

    The fundamental mechanics of delamination in fiber composite laminates is studied. Mathematical formulation of the problem is based on laminate anisotropic elasticity theory and interlaminar fracture mechanics concepts. Stress singularities and complete solution structures associated with general composite delaminations are determined. For a fully open delamination with traction-free surfaces, oscillatory stress singularities always appear, leading to physically inadmissible field solutions. A refined model is introduced by considering a partially closed delamination with crack surfaces in finite-length contact. Stress singularities associated with a partially closed delamination having frictional crack-surface contact are determined, and are found to be different from the inverse square-root one of the frictionless-contact case. In the case of a delamination with very small area of crack closure, a simplified model having a square-root stress singularity is employed by taking the limit of the partially closed delamination. The possible presence of logarithmic-type stress singularity is examined; no logarithmic singularity of any kind is found in the composite delamination problem. Numerical examples of dominant stress singularities are shown for delaminations having crack-tip closure with different frictional coefficients between general (1) and (2) graphite-epoxy composites. Previously announced in STAR as N84-13221

  19. Fibre Reinforced Composite: Post and Core Material in a Pediatric Patient - An Alternative to Usual

    PubMed Central

    Tandon, Shobha

    2014-01-01

    Fractured teeth are always a challenge to the dentist. The root canal therapy today can retain even very badly broken teeth. One of the most accepted techniques involve restoration of extensively carious or badly fractured teeth by the fabrication of a post and core while utilizing the root canal space for anchorage. So far, the only materials that are available to the dentist for this procedure have been a variety of metallic alloys. These materials are hard and need to be cast precisely so that they can fit the canals. Today materials are available which usually eliminates all the intermediate steps which are done in laboratories and the total control is rendered in the hands of the dentist, to fabricate on the chair, a resilient, aesthetic and bonded post and core. One such material is discussed here in a pediatric permanent anterior tooth. PMID:25584339

  20. Fiber Reinforced Composite Cores and Panels

    NASA Technical Reports Server (NTRS)

    Day, Stephen W. (Inventor); Campbell, G. Scott (Inventor); Tilton, Danny E. (Inventor); Stoll, Frederick (Inventor); Sheppard, Michael (Inventor); Banerjee, Robin (Inventor)

    2013-01-01

    A fiber reinforced core panel is formed from strips of plastics foam helically wound with layers of rovings to form webs which may extend in a wave pattern or may intersect transverse webs. Hollow tubes may replace foam strips. Axial rovings cooperate with overlying helically wound rovings to form a beam or a column. Wound roving patterns may vary along strips for structural efficiency. Wound strips may alternate with spaced strips, and spacers between the strips enhance web buckling strength. Continuously wound rovings between spaced strips permit folding to form panels with reinforced edges. Continuously wound strips are helically wrapped to form annular structures, and composite panels may combine both thermoset and thermoplastic resins. Continuously wound strips or strip sections may be continuously fed either longitudinally or laterally into molding apparatus which may receive skin materials to form reinforced composite panels.

  1. Neutron imaging of fiber-reinforced materials

    NASA Astrophysics Data System (ADS)

    Bastürk, M.; Kardjilov, N.; Rauch, H.; Vontobel, P.

    2005-04-01

    Glass-fiber-reinforced plastic laminates used for the insulation of Toroidal Field (TF) magnet-coils and fiber-reinforced silicon carbide ceramic composites used as structural material for the self-cooled Pb-17Li blanket module are attractive candidate materials for fusion reactors because of their high performance under extreme conditions. Porosity, which depends on the manufacturing process, and swelling of fiber-reinforced materials due to the high flux of radiation are the main problems. The aim of this study is to describe the experimental procedures of different imaging methods, and also to decide the most efficient imaging method for the investigations of the complex microstructure of fiber-reinforced materials. In this work, the fiber-reinforced composites were inspected with neutron and X-ray radiographies at ATI-Vienna and also at PSI-Villigen. A contrast enhancement at the edges can be achieved by means of phase contrast neutron radiography (NR), which is based on the wave properties of neutrons and arises from the neutron refraction (rather than attenuation). Elements having different refractive index within a sample cause a phase shift between coherent neutron waves. The degree of coherence can be determined by means of the coherence pattern caused by the sample, when a point source (pinhole) is used and the distance between source and sample is varied.

  2. Cyclic fatigue behaviour of fibre reinforced rubber-toughened nylon composite materials

    NASA Astrophysics Data System (ADS)

    Pinot, L.; Gomina, M.; Jernot, J.-P.; Moreau, R.; Nakache, E.

    2005-03-01

    The effects of the amount of rubber, the concentration of fibres and the state of the fibre/matrix interface upon the mechanical behaviour of glass fibre/rubber-toughened nylon ternary blends are checked. First, monotonic tensile tests were carried out on different intermediate materials and then on the ternary blends to derive the stress-strain curves and document the damage mechanisms. Cyclic fatigue tests were implemented on tensile specimens and the results were analysed in terms of the reduction of the Young's modulus, the increase of the hysteresis energy rate in the stress-strain diagram and the temperature rise. These findings were correlated to fractographic observations to assess the role of the different constituents.

  3. Interface shear strength and fracture behaviour of porous glass-fibre-reinforced composite implant and bone model material.

    PubMed

    Nganga, Sara; Ylä-Soininmäki, Anne; Lassila, Lippo V J; Vallittu, Pekka K

    2011-11-01

    Glass-fibre-reinforced composites (FRCs) are under current investigation to serve as durable bone substitute materials in load-bearing orthopaedic implants and bone implants in the head and neck area. The present form of biocompatible FRCs consist of non-woven E-glass-fibre tissues impregnated with varying amounts of a non-resorbable photopolymerisable bifunctional polymer resin with equal portions of both bis-phenyl-A-glycidyl dimethacrylate (BisGMA) and triethyleneglycol dimethacrylate (TEGDMA). FRCs with a total porosity of 10-70 vol% were prepared, more than 90 vol% of which being functional (open pores), and the rest closed. The pore sizes were greater than 100 μm. In the present study, the push-out test was chosen to analyse the shear strength of the interface between mechanically interlocked gypsum and a porous FRC implant structure. Gypsum was used as a substitute material for natural bone. The simulative in vitro experiments revealed a significant rise of push-out forces to the twofold level of 1147 ± 271 N for an increase in total FRC porosity of 43%. Pins, intended to model the initial mechanical implant fixation, did not affect the measured shear strength of the gypsum-FRC interface, but led to slightly more cohesive fracture modes. Fractures always occurred inside the gypsum, it having lower compressive strength than the porous FRC structures. Therefore, the largest loads were restricted by the brittleness of the gypsum. Increases of the FRC implant porosity tended to lead to more cohesive fracture modes and higher interfacial fracture toughness. Statistical differences were confirmed using the Kruskal-Wallis test. The differences between the modelled configuration showing gypsum penetration into all open pores and the real clinical situation with gradual bone ingrowth has to be considered. PMID:22098879

  4. Quantitative radiographic analysis of fiber reinforced polymer composites.

    PubMed

    Baidya, K P; Ramakrishna, S; Rahman, M; Ritchie, A

    2001-01-01

    X-ray radiographic examination of the bone fracture healing process is a widely used method in the treatment and management of patients. Medical devices made of metallic alloys reportedly produce considerable artifacts that make the interpretation of radiographs difficult. Fiber reinforced polymer composite materials have been proposed to replace metallic alloys in certain medical devices because of their radiolucency, light weight, and tailorable mechanical properties. The primary objective of this paper is to provide a comparable radiographic analysis of different fiber reinforced polymer composites that are considered suitable for biomedical applications. Composite materials investigated consist of glass, aramid (Kevlar-29), and carbon reinforcement fibers, and epoxy and polyether-ether-ketone (PEEK) matrices. The total mass attenuation coefficient of each material was measured using clinical X-rays (50 kev). The carbon fiber reinforced composites were found to be more radiolucent than the glass and kevlar fiber reinforced composites. PMID:11261603

  5. Graphite fiber reinforced glass matrix composites for aerospace applications

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Bacon, J. F.; Dicus, D. L.

    1979-01-01

    The graphite fiber reinforced glass matrix composite system is described. Although this composite is not yet a mature material, it possesses low density, attractive mechanical properties at elevated temperatures, and good environmental stability. Properties are reported for a borosilicate glass matrix unidirectionally reinforced with 60 volume percent HMS graphite fiber. The flexural strength and fatigue characteristics at room and elevated temperature, resistance to thermal cycling and continuous high temperature oxidation, and thermal expansion characteristics of the composite are reported. The properties of this new composite are compared to those of advanced resin and metal matrix composites showing that graphite fiber reinforced glass matrix composites are attractive for aerospace applications.

  6. Reinforcing Liner For Composite Cryogenic Tank

    NASA Technical Reports Server (NTRS)

    Burgeson, John E.

    1990-01-01

    Proposed fiber-reinforced liner for graphite/epoxy fuel tank prevents metal-foil leakage barrier from detaching at low temperatures. Consists of epoxy containing fibers of Spectra 1000. Tank holds inner layers of foil, adhesive, and proposed liner. Liner much thinner than shell, adds little weight, and subtracts little volume. Lined composite tank used to hold liquids from room temperature to cryogenic temperatures. Not suitable for oxygen, because organic materials in liner oxidized quickly.

  7. Physics-Based Simulation and Experiment on Blast Protection of Infill Walls and Sandwich Composites Using New Generation of Nano Particle Reinforced Materials

    NASA Astrophysics Data System (ADS)

    Irshidat, Mohammad

    A critical issue for the development of nanotechnology is our ability to understand, model, and simulate the behavior of small structures and to make the connection between nano structure properties and their macroscopic functions. Material modeling and simulation helps to understand the process, to set the objectives that could guide laboratory efforts, and to control material structures, properties, and processes at physical implementation. These capabilities are vital to engineering design at the component and systems level. In this research, experimental-computational-analytical program was employed to investigate the performance of the new generation of polymeric nano-composite materials, like nano-particle reinforced elastomeric materials (NPREM), for the protection of masonry structures against blast loads. New design tools for using these kinds of materials to protect Infill Walls (e.g. masonry walls) against blast loading were established. These tools were also extended to cover other type of panels like sandwich composites. This investigation revealed that polymeric nano composite materials are strain rate sensitive and have large amount of voids distributed randomly inside the materials. Results from blast experiments showed increase in ultimate flexural resistance achieved by both unreinforced and nano reinforced polyurea retrofit systems applied to infill masonry walls. It was also observed that a thin elastomeric coating on the interior face of the walls could be effective at minimizing the fragmentation resulting from blast. More conclusions are provided with recommended future research.

  8. Joint Strength Control at the Fiber/Matrix Interface during the Production of Polymer Composite Materials Reinforced with High Performance Fibers

    NASA Astrophysics Data System (ADS)

    Kudinov, Vladimir V.; Korneeva, Natalia V.

    2010-06-01

    The paper presents the results obtained in the study of the joint strength between polymer matrix and high performance polyethylene fiber. The fiber/matrix joints simulate the unit cell of the fiber-reinforced composite materials. Effect of heat treatment on the composite properties at the interface was estimated by a multifilament wet-pull-out method. It was found that the joint strength may be increased with the help of extra heart treatment. Both the energy to peak load and the energy to failure for CM joints at various stages of loading were determined.

  9. Tensile properties of nanoclay reinforced epoxy composites

    NASA Astrophysics Data System (ADS)

    Ku, H.; Trada, Mohan

    2013-08-01

    Kinetic epoxy resin was filled with nanoclay to increase tensile properties of the composite for civil and structural. This project manufactured samples with different percentages by weight of nanoclay in the composites in steps of 1 wt %, which were then post-cured in an oven. The samples were then subjected to tensile tests. The results showed that the composite with 3 wt % of nanoclay produced the highest yield and tensile strengths. However, the Young's modulus increased with increasing nanoparticulate loading. It is hoped that the discussion and results in this work would not only contribute towards the further development of nanoclay reinforced epoxy composites with enhanced material properties, but also provide useful information for the studies of fracture toughness, tensile properties and flexural properties of other composites.

  10. Composite Structural Materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

    1984-01-01

    The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.

  11. Strengthening composite resin restorations with ceramic whisker reinforcement.

    PubMed

    Xu, H H; Schumacher, G E; Eichmiller, F C; Antonucci, J M

    2000-01-01

    Due to their tendency to fracture, current composite formulations are unsuitable for use in large stress-bearing direct posterior restorations that involve cusps. This study investigated the use of single-crystalline ceramic whiskers for the reinforcement of composite resins. The whisker-reinforced composite materials exhibited physical characteristics (i.e., flexural strength, work-of-fracture, and elastic modulus) that were significantly greater (P < 0.05; Student's t test) than those of traditional composite formulations. The experimental materials also had a surface smoothness that was essentially comparable to hybrid composite control specimens. PMID:11404884

  12. Stress relaxation in discontinuously reinforced composites

    SciTech Connect

    Shi, N.; Arsenault, R.J.

    1995-05-01

    It has been observed that in discontinuously-reinforced Al{sub 2}0{sub 3}/NiAl composites that as the reinforcement size increases the average density of dislocations generated from the relaxation of the thermal stresses increases, and the corresponding thermal residual stresses slightly decrease. Similar changes result when the reinforcement morphology changes from spheres to short fibers to continuous filaments. The changes of dislocation density and thermal residual stresses with respect to particle size are in contrast to those observed in the SiC/Al counterpart A previously developed simple model used to explain the SiC/Al data, which was based on prismatic dislocation punching, suggested that the density of the misfit dislocations decreases when the reinforcement size increases. In this investigation, a simple model is proposed to explain the anomaly in the development of thermal residual stresses and the generation of misfit dislocations as a function of the particle size and shape in Al{sub 2}0{sub 3}/NiAl composites. As a result of a lack of sufficient independent-slip-systems in low symmetry materials such as NiAl, plastic relaxation of the thermal stresses is severely constrained as compared to fcc Al. As such, plastic relaxation requires collaborative slips in an aggregate of grains. This only occurs when the length scale of the varying misfit thermal stress field is much larger than the average grain size. That is, the mechanism of plastic relaxation becomes operative when the reinforcement size increases.

  13. Composites Reinforced in Three Dimensions by Using Low Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Erb, Randall M.; Libanori, Rafael; Rothfuchs, Nuria; Studart, André R.

    2012-01-01

    The orientation and distribution of reinforcing particles in artificial composites are key to enable effective reinforcement of the material in mechanically loaded directions, but remain poor if compared to the distinctive architectures present in natural structural composites such as teeth, bone, and seashells. We show that micrometer-sized reinforcing particles coated with minimal concentrations of superparamagnetic nanoparticles (0.01 to 1 volume percent) can be controlled by using ultralow magnetic fields (1 to 10 milliteslas) to produce synthetic composites with tuned three-dimensional orientation and distribution of reinforcements. A variety of structures can be achieved with this simple method, leading to composites with tailored local reinforcement, wear resistance, and shape memory effects.

  14. SiC Fiber-Reinforced Celsian Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    2003-01-01

    Celsian is a promising matrix material for fiber-reinforced composites for high temperature structural applications. Processing and fabrication of small diameter multifilament silicon carbide tow reinforced celsian matrix composites are described. Mechanical and microstructural properties of these composites at ambient and elevated temperatures are presented. Effects of high-temperature exposures in air on the mechanical behavior of these composites are also given. The composites show mechanical integrity up to 1100 C but degrade at higher temperatures in oxidizing atmospheres. A model has been proposed for the degradation of these composites in oxidizing atmospheres at high temperatures.

  15. Silicon, iron and titanium doped calcium phosphate-based glass reinforced biodegradable polyester composites as bone analogous materials

    NASA Astrophysics Data System (ADS)

    Shah Mohammadi, Maziar

    Bone defects resulting from disease or traumatic injury is a major health care problem worldwide. Tissue engineering offers an alternative approach to repair and regenerate bone through the use of a cell-scaffold construct. The scaffold should be biodegradable, biocompatible, porous with an open pore structure, and should be able to withstand the applied forces. Phosphate-based glasses (PGs) may be used as reinforcing agents in degradable composites since their degradation can be predicted and controlled through their chemistry. This doctoral dissertation describes the development and evaluation of PGs reinforced biodegradable polyesters for intended applications in bone augmentation and regeneration. This research was divided into three main objectives: 1) Investigating the composition dependent properties of novel PG formulations by doping a sodium-free calcium phosphate-based glass with SiO2, Fe2O3, and TiO2. Accordingly, (50P2 O5-40CaO- xSiO2-(10-x)Fe2O3, where x = 10, 5 and 0 mol.%) and (50P2O5-40CaO-xSiO 2-(10-x)TiO2 where x = 10, 7, 5, 3 and 0 mol.%) formulations were developed and characterised. SiO2 incorporation led to increased solubility, ion release, pH reduction, as well as hydrophilicity, surface energy, and surface polarity. In contrast, doping with Fe2O 3 or TiO2 resulted in more durable glasses, and improved cell attachment and viability. It was hypothesised that the presence of SiO 2 in the TiO2-doped formulations could up-regulate the ionic release from the PG leading to higher alkaline phosphatase activity of MC3T3-E1 cells. 2) Incorporating Si, Fe, and Ti doped PGs as fillers, either as particulates (PGPs) or fibres (PGFs), into biodegradable polyesters (polycaprolactone (PCL) and semi-crystalline and amorphous poly(lactic acid) (PLA and PDLLA)) with the aim of developing degradable bone analogous composites. It was found that PG composition and geometry dictated the weight loss, ionic release, and mechanical properties of the composites. It

  16. Composite material

    DOEpatents

    Hutchens, Stacy A.; Woodward, Jonathan; Evans, Barbara R.; O'Neill, Hugh M.

    2012-02-07

    A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

  17. Nano polypeptide particles reinforced polymer composite fibers.

    PubMed

    Li, Jiashen; Li, Yi; Zhang, Jing; Li, Gang; Liu, Xuan; Li, Zhi; Liu, Xuqing; Han, Yanxia; Zhao, Zheng

    2015-02-25

    Because of the intensified competition of land resources for growing food and natural textile fibers, there is an urgent need to reuse and recycle the consumed/wasted natural fibers as regenerated green materials. Although polypeptide was extracted from wool by alkaline hydrolysis, the size of the polypeptide fragments could be reduced to nanoscale. The wool polypeptide particles were fragile and could be crushed down to nano size again and dispersed evenly among polymer matrix under melt extrusion condition. The nano polypeptide particles could reinforce antiultraviolet capability, moisture regain, and mechanical properties of the polymer-polypeptide composite fibers. PMID:25647481

  18. An Assessment of Self-Healing Fiber Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Smith, Joseph G., Jr.

    2012-01-01

    Several reviews and books have been written concerning self-healing polymers over the last few years. These have focused primarily on the types of self-healing materials being studied, with minor emphasis given to composite properties. The purpose of this review is to assess the self-healing ability of these materials when utilized in fiber reinforced composites

  19. PEDOT:PSS-Based Piezo-Resistive Sensors Applied to Reinforcement Glass Fibres for in Situ Measurement during the Composite Material Weaving Process

    PubMed Central

    Trifigny, Nicolas; Kelly, Fern M.; Cochrane, Cédric; Boussu, François; Koncar, Vladan; Soulat, Damien

    2013-01-01

    The quality of fibrous reinforcements used in composite materials can be monitored during the weaving process. Fibrous sensors previously developed in our laboratory, based on PEDOT:PSS, have been adapted so as to directly measure the mechanical stress on fabrics under static or dynamic conditions. The objective of our research has been to develop new sensor yarns, with the ability to locally detect mechanical stresses all along the warp or weft yarn. This local detection is undertaken inside the weaving loom in real time during the weaving process. Suitable electronic devices have been designed in order to record in situ measurements delivered by this new fibrous sensor yarn. PMID:23959238

  20. PEDOT:PSS-based piezo-resistive sensors applied to reinforcement glass fibres for in situ measurement during the composite material weaving process.

    PubMed

    Trifigny, Nicolas; Kelly, Fern M; Cochrane, Cédric; Boussu, François; Koncar, Vladan; Soulat, Damien

    2013-01-01

    The quality of fibrous reinforcements used in composite materials can be monitored during the weaving process. Fibrous sensors previously developed in our laboratory, based on PEDOT:PSS, have been adapted so as to directly measure the mechanical stress on fabrics under static or dynamic conditions. The objective of our research has been to develop new sensor yarns, with the ability to locally detect mechanical stresses all along the warp or weft yarn. This local detection is undertaken inside the weaving loom in real time during the weaving process. Suitable electronic devices have been designed in order to record in situ measurements delivered by this new fibrous sensor yarn. PMID:23959238

  1. Fiber reinforced thermoplastic resin matrix composites

    NASA Technical Reports Server (NTRS)

    Jones, Robert J. (Inventor); Chang, Glenn E. C. (Inventor)

    1989-01-01

    Polyimide polymer composites having a combination of enhanced thermal and mechanical properties even when subjected to service temperatures as high as 700.degree. F. are described. They comprise (a) from 10 to 50 parts by weight of a thermoplastic polyimide resin prepared from 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane and (b) from 90 to 50 parts by weight of continuous reinforcing fibers, the total of (a) and (b) being 100 parts by weight. Composites based on polyimide resin formed from 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane and pyromellitic dianhydride and continuous carbon fibers retained at least about 50% of their room temperature shear strength after exposure to 700.degree. F. for a period of 16 hours in flowing air. Preferably, the thermoplastic polyimide resin is formed in situ in the composite material by thermal imidization of a corresponding amide-acid polymer prepared from 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. It is also preferred to initially size the continuous reinforcing fibers with up to about one percent by weight of an amide-acid polymer prepared from 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. In this way imidization at a suitable elevated temperature results in the in-situ formation of a substantially homogeneous thermoplastic matrix of the polyimide resin tightly and intimately bonded to the continuous fibers. The resultant composites tend to have optimum thermo-mechanical properties.

  2. Nanotube reinforced thermoplastic polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Shofner, Meisha Lei

    The inherent high strength, thermal conductivity, and electrical conductivity make nanotubes attractive reinforcements for polymer matrix composites. However, the structure that makes them desirable also causes highly anisotropic properties and limited reactivity with other materials. This thesis isolates these problems in two separate studies aimed at improving mechanical properties with single wall nanotube (SWNT) reinforced thermoplastic polymer composites. The two studies demonstrate the effect of solid freeform fabrication (SFF) and chemical functionalization on anisotropy and limited reactivity, respectively. Both studies showed mechanical property improvements. The alignment study demonstrates a maximum increase of 93% in tensile modulus with single wall nanotubes (SWNTs). The chemical functionalization study shows a larger increase in storage modulus for functionalized SWNTs as compared to purified SVWNTs with respective increases of 9% and 44% in storage modulus. Improved interfacial properties are also observed as a decrease in mechanical damping. Maximum property increases in composites are obtained when nanotubes are aligned, requiring additional processing consideration to the anisotropic structure. Melt spinning and extrusion processing effectively align nanotubes, but the end product of these techniques, composite fibers, requires further processing to be incorporated into finished parts. Extrusion-based SFF is a novel technique for processing nanotube reinforced composites because it allows for the direct fabrication of finished parts containing aligned nanotubes. SFF processing produces parts containing preferentially oriented nanotubes with improved mechanical properties when compared to isotropic composites. Functionalization of the nanotube surface disrupts the rope structure to obtain smaller ropes and promote further interfacial bonding. The chemically inert nature of nanotubes resulting from a structure containing few defects and the

  3. Comparison of the flexural strength of six reinforced restorative materials.

    PubMed

    Cohen, B I; Volovich, Y; Musikant, B L; Deutsch, A S

    2001-01-01

    This study calculated the flexural strength for six reinforced restorative materials and demonstrated that flexural strength values can be determined simply by using physical parameters (diametral tensile strength and Young's modulus values) that are easily determined experimentally. A one-way ANOVA analysis demonstrated a statistically significant difference between the two reinforced glass ionomers and the four composite resin materials, with the composite resin being stronger than the glass ionomers. PMID:12017792

  4. Effects of temperature and humidity cycling on the strengths of textile reinforced carbon/epoxy composite materials

    NASA Technical Reports Server (NTRS)

    Cano, Roberto J.; Furrow, Keith W.

    1993-01-01

    Results are presented from an experimental evaluation of the combined effects of temperature and humidity cycling on AS4/3501-6 composites (unstitched, Kevlar 29 stitched, and S-2 glass stitched uniweave fabric) and AS4/E905L composites (2-D, S-2 glass stitched 2-D, and 3-D braided fabric). The AS4/3501-6 uniweave material had a quasi-isotropic layup, whereas the AS4/E905L materials were braided in a (+/-30 deg/0 deg)(sub s) orientation. Data presented include compression strengths and compression-compression fatigue results for uncycled composites and cycled composites (160, 480, 720, and 1280 cycles from 140 deg F at 95 percent relative humidity to -67 deg F). To observe the presence of microcracking within the laminates, photomicrographs were taken of each material type at the end of each cycling period. Microcracks were found to be more prevalent within stitched laminates, predominantly around individual stitches. The glass stitched laminates showed significant microcracking even before cycling. Less microcracking was evident in the Kevlar stitched materials, whereas the unstitched uniweave material developed microcracks only after cycling. The 3-D braid did not develop microcracks. The static compression strengths of the unstitched and Kevlar stitched uniweave materials were degraded by about 10 percent after 1280 temperature/humidity cycles, whereas the reduction in compression strength for the glass stitched uniweave was less than 3 percent. The reduction in compression strength for the glass stitched 2-D braid was less than 8 percent. The unstitched 2-D and 3-D braids did not lose strength from temperature/humidity cycling. The compression-compression fatigue properties of all six material types were not affected by temperature/humidity cycling.

  5. Trans-Laminar-Reinforced (TLR) Composites

    NASA Technical Reports Server (NTRS)

    Hinders, Mark; Dickinson, Larry

    1997-01-01

    A Trans-Laminar-Reinforced (TLR) composite is defined as composite laminate with up to five percent volume of fibrous reinforcement oriented in a 'trans-laminar' fashion in the through-thickness direction. The TLR can be continuous threads as in 'stitched laminates', or it can be discontinuous rods or pins as in 'Z-Fiber(TM) materials. It has been repeatedly documented in the literature that adding TLR to an otherwise two dimensional laminate results in the following advantages: substantially improved compression-after-impact response; considerably increased fracture toughness in mode 1 (double cantilever beam) and mode 2 (end notch flexure); and severely restricted size and growth of impact damage and edge delamination. TLR has also been used to eliminate catastrophic stiffener disbonding in stiffened structures. TLR directly supports the 'Achilles heel' of laminated composites, that is delamination. As little as one percent volume of TLR significantly alters the mechanical response of laminates. The objective of this work was to characterize the effects of TLR on the in-plane and inter-laminar mechanical response of undamaged composite laminates. Detailed finite element models of 'unit cells', or representative volumes, were used to study the effects of adding TLR on the elastic constants; the in-plane strength; and the initiation of delamination. Parameters investigated included TLR material, TLR volume fraction, TLR diameter, TLR through-thickness angle, ply stacking sequence, and the microstructural features of pure resin regions and curved in-plane fibers. The work was limited to the linear response of undamaged material with at least one ply interface. An inter-laminar dominated problem of practical interest, a flanged skin in bending, was also modeled.

  6. Mechanical properties of some silicon carbide reinforced aluminum composites

    SciTech Connect

    Tsangarakis, N.; Andrews, B.O.; Cavallaro, C.

    1987-05-01

    The mechanical properties of several particulate and continuous fiber silicon carbide-reinforced aluminum composites were examined. The tensile strength of a 47 percent silicon carbide fiber unidirectionally-reinforced aluminum composite was 1273 and 76 MPa parallel and normal to the fiber direction, respectively. The tensile strength of (0 deg/90 deg) 4s and (0/sub 2/90/0)s composites were 629 and 864 MPa, respectively. The tensile properties of a 30 percent silicon carbide particulate reinforced aluminum were found to depend on the chemistry of the metal matrix. The endurance limits of the fiber and the particulate reinforced aluminum were at the most 55 percent and 33 percent of the respective tensile strengths. The fracture toughness of the fiber reinforced composite varied with specimen width, while that of the particulate reinforced composite was 21-29 MPa sq rt m. The fatigue crack growth rate in the latter composite decreased with material thickness. There were indications that the fatigue crack growth rate in the silicon carbide particulate reinforced aluminum may be independent of variations in the chemistry of the metal matrix. 6 references.

  7. Aluminum-Alloy-Matrix/Alumina-Reinforcement Composites

    NASA Technical Reports Server (NTRS)

    Kashalikar, Uday; Rozenoyer, Boris

    2004-01-01

    Isotropic composites of aluminum-alloy matrices reinforced with particulate alumina have been developed as lightweight, high-specific-strength, less-expensive alternatives to nickel-base and ferrous superalloys. These composites feature a specific gravity of about 3.45 grams per cubic centimeter and specific strengths of about 200 MPa/(grams per cubic centimeter). The room-temperature tensile strength is 100 ksi (689 MPa) and stiffness is 30 Msi (206 GPa). At 500 F (260 C), these composites have shown 80 percent retention in strength and 95 percent retention in stiffness. These materials also have excellent fatigue tolerance and tribological properties. They can be fabricated in net (or nearly net) sizes and shapes to make housings, pistons, valves, and ducts in turbomachinery, and to make structural components of such diverse systems as diesel engines, automotive brake systems, and power-generation, mining, and oil-drilling equipment. Separately, incorporation of these metal matrix composites within aluminum gravity castings for localized reinforcement has been demonstrated. A composite part of this type can be fabricated in a pressure infiltration casting process. The process begins with the placement of a mold with alumina particulate preform of net or nearly net size and shape in a crucible in a vacuum furnace. A charge of the alloy is placed in the crucible with the preform. The interior of the furnace is evacuated, then the furnace heaters are turned on to heat the alloy above its liquidus temperature. Next, the interior of the furnace is filled with argon gas at a pressure about 900 psi (approximately equal to 6.2 MPa) to force the molten alloy to infiltrate the preform. Once infiltrated, the entire contents of the crucible can be allowed to cool in place, and the composite part recovered from the mold.

  8. X-ray photoelectron spectroscopic studies of graphitic materials and interfacial interactions in carbon-fiber-reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Viswanathan, Hema L.

    This dissertation involves the X-ray photoelectron spectroscopic (XPS) study of the chemistry associated with carbon fiber-reinforced composites fabricated using PAN-based carbon fibers and a thermoplastic polyimide resin. The mechanical properties of the ultimate composite are significantly affected by the nature of the fiber/matrix interface. Interfacial interaction can be promoted by the electrochemical modification of the fiber surface. The determination of carbon fiber microstructure was conducted through angle-resolved valence band photoemission studies of highly ordered graphite. The change in orientation of the basal planes and reactive edge sites with take-off angle provided a method for the determination of surface microstructure. The electronic structure of solid-state graphite was described using a band structure model and the results obtained were compared with the multiple scattered wave X a calculations. PAN-based fibers were electrochemically oxidized and studied using monochromatic X-radiation. The extremely narrow natural linewidth of the monochromatized Al K a radiation allowed previously unresolved features to be seen. In addition, sample decomposition due to radiative heat from the X-ray source is eliminated. Fibers that were pretreated by the manufacturer were subjected to further electrochemical oxidation. The fibers behaved in an erratic and non-reproducible manner. The surface treatment was removed by heating the fibers in vacuum, followed by XPS analysis and electrochemical oxidation. The fiber/matrix interface was simulated by coating a very thin layer of the polyimide resin on the surface of the fiber followed by XPS analysis. The validity of a proposed structure for the resin was confirmed by comparison with ab initio calculations conducted on the resin repeat unit. A high level of fiber/matrix interaction was observed for electrochemically oxidized fibers. The possibility of solvent interaction with the fiber surface was eliminated by

  9. Evaluation of capillary reinforced composites

    NASA Technical Reports Server (NTRS)

    Cahill, J. E.; Halase, J. F.; South, W. K.; Stoffer, L. J.

    1985-01-01

    Anti-icing of the inlet of jet engines is generally performed with high pressure heated air that is directed forward from the compressor through a series of pipes to various manifolds located near the structures to be anti-iced. From these manifolds, the air is directed to all flowpath surfaces that may be susceptible to ice formation. There the anti-icing function may be performed by either heat conduction or film heating. Unfortunately, the prospect of utilizing lighweight, high strength composites for inlet structures of jet engines has been frustrated by the low transverse thermal conductivity of such materials. It was the objective of this program to develop an advanced materials and design concept for anti-icing composite structures. The concept that was evaluated used capillary glass tubes embedded on the surface of a composite structure with heated air ducted through the tubes. An analytical computer program was developed to predict the anti-icing performance of such tubes and a test program was conducted to demonstrate actual performance of this system. Test data and analytical code results were in excellent agreement. Both indicate feasibility of using capillary tubes for surface heating as a means for composite engine structures to combat ice accumulation.

  10. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1982-01-01

    The promise of filamentary composite materials, whose development may be considered as entering its second generation, continues to generate intense interest and applications activity. Fiber reinforced composite materials offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been achieved since the initial developments in the mid 1960's. Rather limited applications to primary aircraft structure have been made, however, mainly in a material-substitution mode on military aircraft, except for a few experiments currently underway on large passenger airplanes in commercial operation. To fulfill the promise of composite materials completely requires a strong technology base. NASA and AFOSR recognize the present state of the art to be such that to fully exploit composites in sophisticated aerospace structures, the technology base must be improved. This, in turn, calls for expanding fundamental knowledge and the means by which it can be successfully applied in design and manufacture.

  11. Reinforced rubber composition containing ground coal

    SciTech Connect

    Sperley, R.J.

    1984-10-16

    A reinforced rubber composition is provided comprising a mixture of (a) a sulfur vulcanizable rubber and (b) ground coal having an average mesh size of 25 or more and which produces an aqueous slurry with a pH of less than 7.0, and wherein a metallic reinforcing member is embedded in the rubber mixture of (a) and (b).

  12. Composition and method for making polyimide resin-reinforced fabric

    NASA Technical Reports Server (NTRS)

    Serafini, T. T.; Delvigs, P. (Inventor)

    1981-01-01

    A composition for making polyimide resin reinforced fibers or fabric is discussed. The composition includes a polyfunctional ester, a polyfunctional amine, and an end capping agent. The composition is impregnated into fibers or fabric and heated to form prepreg material. The tack retention characteristics of this prepreg material are improved by incorporating into the composition a liquid olefinic material compatible with the other ingredients of the composition. The prepreg material is heated at a higher temperature to effect formation of the polyimide resin and the monomeric additive is incorporated in the polyimide polymer structure.

  13. Continuous fiber-reinforced titanium aluminide composites

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Brindley, P. K.; Froes, F. H.

    1991-01-01

    An account is given of the fabrication techniques, microstructural characteristics, and mechanical behavior of a lightweight, high service temperature SiC-reinforced alpha-2 Ti-14Al-21Nb intermetallic-matrix composite. Fabrication techniques under investigation to improve the low-temperature ductility and environmental resistance of this material system, while reducing manufacturing costs to competitive levels, encompass powder-cloth processing, foil-fiber-foil processing, and thermal-spray processing. Attention is given to composite microstructure problems associated with fiber distribution and fiber-matrix interfaces, as well as with mismatches of thermal-expansion coefficient; major improvements are noted to be required in tensile properties, thermal cycling effects, mechanical damage, creep, and environmental effects.

  14. Designing bioinspired composite reinforcement architectures via 3D magnetic printing

    PubMed Central

    Martin, Joshua J.; Fiore, Brad E.; Erb, Randall M.

    2015-01-01

    Discontinuous fibre composites represent a class of materials that are strong, lightweight and have remarkable fracture toughness. These advantages partially explain the abundance and variety of discontinuous fibre composites that have evolved in the natural world. Many natural structures out-perform the conventional synthetic counterparts due, in part, to the more elaborate reinforcement architectures that occur in natural composites. Here we present an additive manufacturing approach that combines real-time colloidal assembly with existing additive manufacturing technologies to create highly programmable discontinuous fibre composites. This technology, termed as ‘3D magnetic printing', has enabled us to recreate complex bioinspired reinforcement architectures that deliver enhanced material performance compared with monolithic structures. Further, we demonstrate that we can now design and evolve elaborate reinforcement architectures that are not found in nature, demonstrating a high level of possible customization in discontinuous fibre composites with arbitrary geometries. PMID:26494282

  15. The mechanics of delamination in fiber-reinforced composite materials. II - The delamination behavior and fracture mechanics parameters

    NASA Technical Reports Server (NTRS)

    Wang, S. S.; Choi, I.

    1983-01-01

    Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination is determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method employing singular finite elements is developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special finite elements include the exact delamination stress singularity in its formulation. The method is shown to be computationally accurate and efficient, and operationally simple. To illustrate the basic nature of composite delamination, solutions are shown for edge-delaminated (0/-0/-0/0) and (+ or - 0/+ or - 0/90/90 deg) graphite-epoxy systems under uniform axial extension. Three-dimensional crack-tip stress intensity factors, associated energy release rates, and delamination crack-closure are determined for each individual case. The basic mechanics and mechanisms of composite delamination are studied, and fundamental characteristics unique to recently proposed tests for interlaminar fracture toughness of fiber composite laminates are examined. Previously announced in STAR as N84-13222

  16. The mechanics of delamination in fiber-reinforced composite materials. Part 2: Delamination behavior and fracture mechanics parameters

    NASA Technical Reports Server (NTRS)

    Wang, S. S.; Choi, I.

    1983-01-01

    Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination is determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method employing singular finite elements is developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special finite elements include the exact delamination stress singularity in its formulation. The method is shown to be computationally accurate and efficient, and operationally simple. To illustrate the basic nature of composite delamination, solutions are shown for edge-delaminated (0/-0/-0/0) and (+ or - 0/+ or - 0/90/90 deg) graphite-epoxy systems under uniform axial extenstion. Three-dimensional crack-tip stress intensity factors, associated energy release rates, and delamination crack-closure are determined for each individual case. The basic mechanics and mechanisms of composite delamination are studied, and fundamental characteristics unique to recently proposed tests for interlaminar fracture toughness of fiber composite laminates are examined.

  17. Boron Nitride Nanotubes-Reinforced Glass Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam; Hurst, Janet B.; Choi, Sung R.

    2005-01-01

    Boron nitride nanotubes of significant lengths were synthesized by reaction of boron with nitrogen. Barium calcium aluminosilicate glass composites reinforced with 4 weight percent of BN nanotubes were fabricated by hot pressing. Ambient-temperature flexure strength and fracture toughness of the glass-BN nanotube composites were determined. The strength and fracture toughness of the composite were higher by as much as 90 and 35 percent, respectively, than those of the unreinforced glass. Microscopic examination of the composite fracture surfaces showed pullout of the BN nanotubes. The preliminary results on the processing and improvement in mechanical properties of BN nanotube reinforced glass matrix composites are being reported here for the first time.

  18. Compressive strength of the mineral reinforced aluminium alloy composite

    NASA Astrophysics Data System (ADS)

    Arora, Rama; Sharma, Anju; Kumar, Suresh; Singh, Gurmel; Pandey, O. P.

    2016-05-01

    This paper presents the results of quasi-static compressive strength of aluminium alloy reinforced with different concentration of rutile mineral particles. The reinforced material shows increase in compressive strength with 5wt% rutile concentration as compared to the base alloy. This increase in compressive strength of composite is attributed to direct strengthening due to transfer of load from lower stiffness matrix (LM13 alloy) to higher stiffness reinforcement (rutile particles). Indirect strengthening mechanisms like increase in dislocation density at the matrix-reinforcement interface, grain size refinement of the matrix and dispersion strengthening are also the contributing factors. The decrease in compressive strength of composite with the increased concentration of rutile concentration beyond 5 wt.% can be attributed to the increase in dislocation density due to the void formation at the matrix-reinforcement interface.

  19. Fatigue of continuous fiber reinforced metallic materials

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.; Mirdamadi, M.; Bakuckas, J. G., Jr.

    1993-01-01

    The complex damage mechanisms that occur in fiber reinforced advanced metallic materials are discussed. As examples, results for several layups of SCS-6/Ti-15-3 composites are presented. Fatigue tests were conducted and analyzed for both notched and unnotched specimens at room and elevated temperatures. Test conditions included isothermal, non-isothermal, and simulated mission profile thermomechanical fatigue. Test results indicated that the stress in the 0 degree fibers is the controlling factor for fatigue life for a given test condition. An effective strain approach is presented for predicting crack initiation at notches. Fiber bridging models were applied to crack growth behavior.

  20. Painted Fiberglass-Reinforced Contemporary Sculpture: Investigating Composite Materials, Techniques and Conservation Using a Multi-Analytical Approach.

    PubMed

    Salvadori, Barbara; Cantisani, Emma; Colombini, Maria Perla; Tognon, Cecilia Gaia Rachele

    2016-01-01

    A multi-analytical approach was used to study the constituent materials, manufacturing technique, and state of conservation of a contemporary sculpture. This sculpture, entitled Nuredduna, was created by Aligi Sassu in 1995 and is located in the "Bellariva garden" in Florence (Italy). Fourier transform infrared spectroscopy (FT-IR), optical and electronic microscopy (OM and SEM-EDS), X-ray diffraction (XRD), and portable X-ray fluorescence (XRF) highlighted the multi-layered structure of the statue: fiberglass and an overlay of different layers (gel coat) applied with an unsaturated polyester resin added with aggregate materials and bromine compounds. A top-coat in acrylic black varnish, used as a finish, was also found. The combination of these materials with their different compositions, environmental impact, and even vandalism have negatively affected the state of conservation of Nuredduna, causing the loss of strata in its lower parts (legs and feet). PMID:26767643

  1. Fibre reinforced composites in aircraft construction

    NASA Astrophysics Data System (ADS)

    Soutis, C.

    2005-02-01

    Fibrous composites have found applications in aircraft from the first flight of the Wright Brothers’ Flyer 1, in North Carolina on December 17, 1903, to the plethora of uses now enjoyed by them on both military and civil aircrafts, in addition to more exotic applications on unmanned aerial vehicles (UAVs), space launchers and satellites. Their growing use has risen from their high specific strength and stiffness, when compared to the more conventional materials, and the ability to shape and tailor their structure to produce more aerodynamically efficient structural configurations. In this paper, a review of recent advances using composites in modern aircraft construction is presented and it is argued that fibre reinforced polymers, especially carbon fibre reinforced plastics (CFRP) can and will in the future contribute more than 50% of the structural mass of an aircraft. However, affordability is the key to survival in aerospace manufacturing, whether civil or military, and therefore effort should be devoted to analysis and computational simulation of the manufacturing and assembly process as well as the simulation of the performance of the structure, since they are intimately connected.

  2. Thermoforming of Continuous Fibre Reinforced Thermoplastic Composites

    SciTech Connect

    McCool, Rauri; Murphy, Adrian; Wilson, Ryan; Jiang Zhenyu; Price, Mark

    2011-05-04

    The introduction of new materials, particularly for aerospace products, is not a simple, quick or cheap task. New materials require extensive and expensive qualification and must meet challenging strength, stiffness, durability, manufacturing, inspection and maintenance requirements. Growth in industry acceptance for fibre reinforced thermoplastic composite systems requires the determination of whole life attributes including both part processing and processed part performance data. For thermoplastic composite materials the interactions between the processing parameters, in-service structural performance and end of life recyclability are potentially interrelated. Given the large number and range of parameters and the complexity of the potential relationships, understanding for whole life design must be developed in a systematic building block approach. To assess and demonstrate such an approach this article documents initial coupon level thermoforming trials for a commercially available fibre reinforced thermoplastic laminate, identifying the key interactions between processing and whole life performance characteristics. To examine the role of the thermoforming process parameters on the whole life performance characteristics of the formed part requires a series of manufacturing trials combined with a series of characterisation tests on the manufacturing trial output. Using a full factorial test programme and considering all possible process parameters over a range of potential magnitudes would result in a very large number of manufacturing trials and accompanying characterisation tests. Such an approach would clearly be expensive and require significant time to complete, therefore failing to address the key requirement for a future design methodology capable of rapidly generating design knowledge for new materials and processes. In this work the role of mould tool temperature and blank forming temperature on the thermoforming of a commercially available

  3. Recent progress in NASA Langley textile reinforced composites program

    NASA Technical Reports Server (NTRS)

    Dexter, H. Benson; Harris, Charles E.; Johnston, Norman J.

    1992-01-01

    The NASA LaRC is conducting and sponsoring research to explore the benefits of textile reinforced composites for civil transport aircraft primary structures. The objective of this program is to develop and demonstrate the potential of affordable textile reinforced composite materials to meet design properties and damage tolerance requirements of advanced aircraft structural concepts. In addition to in-house research, the program was recently expanded to include major participation by the aircraft industry and aerospace textile companies. The major program elements include development of textile preforms, processing science, mechanics of materials, experimental characterization of materials, and development and evaluation of textile reinforced composite structural elements and subcomponents. The NASA Langley in-house focus is as follows: development of a science-based understanding of resin transfer molding (RTM), development of powder-coated towpreg processes, analysis methodology, and development of a performance database on textile reinforced composites. The focus of the textile industry participation is on development of multidirectional, damage-tolerant preforms, and the aircraft industry participation is in the areas of design, fabrication and testing of textile reinforced composite structural elements and subcomponents. Textile processes such as 3D weaving, 2D and 3D braiding, and knitting/stitching are being compared with conventional laminated tape processes for improved damage tolerance. Through-the-thickness reinforcements offer significant damage tolerance improvements. However, these gains must be weighed against potential loss in in-plane properties such as strength and stiffness. Analytical trade studies are underway to establish design guidelines for the application of textile material forms to meet specific loading requirements. Fabrication and testing of large structural components are required to establish the full potential of textile reinforced

  4. Reinforcement of metals with advanced filamentary composites

    NASA Technical Reports Server (NTRS)

    Herakovich, C. T.; Davis, J. G.; Dexter, H. B.

    1974-01-01

    This paper reviews some recent applications of the concept of reinforcing metal structures with advanced filamentary composites, and presents some results of an experimental investigation of the tensile behavior of aluminum and titanium reinforced with unidirectional boron/epoxy. Results are given for tubular and flat specimens, bonded at either room temperature or elevated temperature. The composite reinforced metals showed increased stiffness over the all-metal counterpart, as predicted by the rule of mixtures, and the results were independent of specimen geometry. The tensile strength of the born/epoxy reinforced metals is shown to be a function of the geometry of the test specimen and the method of bonding the composite to the metal.

  5. Fiber-reinforced composites in fixed partial dentures

    PubMed Central

    Vallittu, Pekka

    2006-01-01

    Fiber-reinforced composite resin (FRC) prostheses offer the advantages of good aesthetics, minimal invasive treatment, and an ability to bond to the abutment teeth, thereby compensating for less-than-optimal abutment tooth retention and resistance form. These prostheses are composed of two types of composite materials: fiber composites to build the framework and hybrid or microfill particulate composites to create the external veneer surface. This review concentrates on the use of fiber reinforcement in the fabrication of laboratory or chairsidemade composite-fixed partial dentures of conventional preparation. Other applications of FRC in dentistry are briefly mentioned. The possibilities fiber reinforcement technology offers must be emphasized to the dental community. Rather than limiting discussion to whether FRC prostheses will replace metal-ceramic or full-ceramic prostheses, attention should be focused on the additional treatment options brought by the use of fibers. However, more clinical experience is needed. PMID:21526023

  6. Designing with figer-reinforced plastics (planar random composites)

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1982-01-01

    The use of composite mechanics to predict the hygrothermomechanical behavior of planar random composites (PRC) is reviewed and described. These composites are usually made from chopped fiber reinforced resins (thermoplastics or thermosets). The hygrothermomechanical behavior includes mechanical properties, physical properties, thermal properties, fracture toughness, creep and creep rupture. Properties are presented in graphical form with sample calculations to illustrate their use. Concepts such as directional reinforcement and strip hybrids are described. Typical data that can be used for preliminary design for various PRCs are included. Several resins and molding compounds used to make PRCs are described briefly. Pertinent references are cited that cover analysis and design methods, materials, data, fabrication procedures and applications.

  7. Ceramic whisker reinforcement of dental resin composites.

    PubMed

    Xu, H H; Martin, T A; Antonucci, J M; Eichmiller, F C

    1999-02-01

    Resin composites currently available are not suitable for use as large stress-bearing posterior restorations involving cusps due to their tendencies toward excessive fracture and wear. The glass fillers in composites provide only limited reinforcement because of the brittleness and low strength of glass. The aim of the present study was to reinforce dental resins with ceramic single-crystalline whiskers of elongated shapes that possess extremely high strength. A novel method was developed that consisted of fusing silicate glass particles onto the surfaces of individual whiskers for a two-fold benefit: (1) to facilitate silanization regardless of whisker composition; and (2) to enhance whisker retention in the matrix by providing rougher whisker surfaces. Silicon nitride whiskers, with an average diameter of 0.4 microm and length of 5 microm, were coated by the fusion of silica particles 0.04 microm in size to the whisker surface at temperatures ranging from 650 degrees C to 1000 degrees C. The coated whiskers were silanized and manually blended with resins by spatulation. Flexural, fracture toughness, and indentation tests were carried out for evaluation of the properties of the whisker-reinforced composites in comparison with conventional composites. A two-fold increase in strength and toughness was achieved in the whisker-reinforced composite, together with a substantially enhanced resistance to contact damage and microcracking. The highest flexural strength (195+/-8 MPa) and fracture toughness (2.1+/-0.3 MPa x m(1/2)) occurred in a composite reinforced with a whisker-silica mixture at whisker:silica mass ratio of 2:1 fused at 800 degrees C. To conclude, the strength, toughness, and contact damage resistance of dental resin composites can be substantially improved by reinforcement with fillers of ceramic whiskers fused with silica glass particles. PMID:10029470

  8. Simple stressed-skin composites using paper reinforcement

    SciTech Connect

    Bunnell, L.R.

    1990-11-01

    The objective of this study was to demonstrate the composite reinforcement concept in a hands-on manner, using readily available materials; to demonstrate the consequences of certain defects in these structures; and to quantify the gains made by engineering composite construction, using a simple measurement of Young's modulus of electricity. The materials used were foam rubber beams, beams reinforced on one side by bonding with heavy paper, a beam reinforced on both sides by bonding with heavy paper, and a beam with a defect caused by using a piece of waxed paper midway to prevent bonding of the paper. The experiment is designed to teach students at the high school level or above the concept of Young's modulus, a measure of a material's stiffness. 2 figs. (BM)

  9. Development of Flax Fibre based Textile Reinforcements for Composite Applications

    NASA Astrophysics Data System (ADS)

    Goutianos, S.; Peijs, T.; Nystrom, B.; Skrifvars, M.

    2006-07-01

    Most developments in the area of natural fibre reinforced composites have focused on random discontinuous fibre composite systems. The development of continuous fibre reinforced composites is, however, essential for manufacturing materials, which can be used in load-bearing/structural applications. The current work aims to develop high-performance natural fibre composite systems for structural applications using continuous textile reinforcements like UD-tapes or woven fabrics. One of the main problems in this case is the optimisation of the yarn to be used to manufacture the textile reinforcement. Low twisted yarns display a very low strength when tested dry in air and therefore they cannot be used in processes such as pultrusion or textile manufacturing routes. On the other hand, by increasing the level of twist, a degradation of the mechanical properties is observed in impregnated yarns (e.g., unidirectional composites) similar to off-axis composites. Therefore, an optimum twist should be used to balance processability and mechanical properties. Subsequently, different types of fabrics (i.e., biaxial plain weaves, unidirectional fabrics and non-crimp fabrics) were produced and evaluated as reinforcement in composites manufactured by well established manufacturing techniques such as hand lay-up, vacuum infusion, pultrusion and resin transfer moulding (RTM). Clearly, as expected, the developed materials cannot directly compete in terms of strength with glass fibre composites. However, they are clearly able to compete with these materials in terms of stiffness, especially if the low density of flax is taken into account. Their properties are however very favourable when compared with non-woven glass composites.

  10. Carbon Nanomaterials as Reinforcements for Composites

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Lehoczky, S. L.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Carbon nanomaterials including fellerenes, nanotubes (CNT) and nanofibers have been proposed for many applications. One of applications is to use the carbon nanomaterials as reinforcements for composites, especially for polymer matrices. Carbon nanotubes is a good reinforcement for lightweight composite applications due to its low mass density and high Young's modulus. Two obscures need to overcome for carbon nanotubes as reinforcements in composites, which are large quantity production and functioning the nanotubes. This presentation will discuss the carbon nanotube growth by chemical vapor deposition. In order to reduce the cost of producing carbon nanotubes as well as preventing the sliding problems, carbon nanotubes were also synthesized on carbon fibers. The synthesis process and characterization results of nanotubes and nanotubes/fibers will be discussed in the presentation.

  11. Shear bond strength of a new self-adhering flowable composite resin for lithium disilicate-reinforced CAD/CAM ceramic material

    PubMed Central

    Sancakli, Hande Sar; Sancakli, Erkan; Eren, Meltem Mert; Ozel, Sevda; Yucel, Taner; Yildiz, Esra

    2014-01-01

    PURPOSE The purpose of this study was to evaluate and compare the effects of different surface pretreatment techniques on the surface roughness and shear bond strength of a new self-adhering flowable composite resin for use with lithium disilicate-reinforced CAD/CAM ceramic material. MATERIALS AND METHODS A total of one hundred thirty lithium disilicate CAD/CAM ceramic plates with dimensions of 6 mm × 4 mm and 3 mm thick were prepared. Specimens were then assigned into five groups (n=26) as follows: untreated control, coating with 30 µm silica oxide particles (Cojet™ Sand), 9.6% hydrofluoric acid etching, Er:YAG laser irradiation, and grinding with a high-speed fine diamond bur. A self-adhering flowable composite resin (Vertise Flow) was applied onto the pre-treated ceramic plates using the Ultradent shear bond Teflon mold system. Surface roughness was measured by atomic force microscopy. Shear bond strength test were performed using a universal testing machine at a crosshead speed of 1 mm/min. Surface roughness data were analyzed by one-way ANOVA and the Tukey HSD tests. Shear bond strength test values were analyzed by Kruskal-Wallis and Mann-Whitney U tests at α=.05. RESULTS Hydrofluoric acid etching and grinding with high-speed fine diamond bur produced significantly higher surface roughness than the other pretreatment groups (P<.05). Hydrofluoric acid etching and silica coating yielded the highest shear bond strength values (P<.001). CONCLUSION Self-adhering flowable composite resin used as repair composite resin exhibited very low bond strength irrespective of the surface pretreatments used. PMID:25551002

  12. Technology and Development of Self-Reinforced Polymer Composites

    NASA Astrophysics Data System (ADS)

    Alcock, Ben; Peijs, Ton

    In recent years there has been an increasing amount of interest, both commercially and scientifically, in the emerging field of "self-reinforced polymer composites". These materials, which are sometimes also referred to as "single polymer composites", or "all-polymer composites", were first conceived in the 1970s, and are now beginning to appear in a range of commercial products. While high mechanical performance polymer fibres or tapes are an obvious precursor for composite development, various different technologies have been developed to consolidate these into two- or three-dimensional structures. This paper presents a review of the various processing techniques that have been reported in the literature for the manufacture of self-reinforced polymer composites from fibres or tapes of different polymers, and so exploit the fibre or tape performance in a commercial material or product.

  13. Buckling of Fiber Reinforced Composite Plates with Nanofiber Reinforced Matrices

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Murthy, Pappu L. N.

    2010-01-01

    Anisotropic composite plates were evaluated with nanofiber reinforced matrices (NFRM). The nanofiber reinforcement volumes ratio in the matrix was 0.01. The plate dimensions were 20 by 10 by 1.0 in. (508 by 254 by 25.4 mm). Seven different loading condition cases were evaluated: three for uniaxial loading, three for pairs of combined loading, and one with three combined loadings. The anisotropy arose from the unidirectional plates having been at 30 from the structural axis. The anisotropy had a full 6 by 6 rigidities matrix which were satisfied and solved by a Galerkin buckling algorithm. The buckling results showed that the NFRM plates buckled at about twice those with conventional matrix.

  14. Composite laminate free edge reinforcement concepts

    NASA Technical Reports Server (NTRS)

    Howard, W. E.; Gossard, T., Jr.; Jones, R. M.

    1985-01-01

    The presence of a free edge in a laminated composite structure can result in delamination of the composite under certain loading conditions. Linear finite element analysis predicts large or even singular interlaminar stresses near the free edge. Edge reinforcements which will reduce these interlaminar stresses, prevent or delay the onset of delaminations, and thereby increase the strength and life of the structure were studied. Finite element models are used to analyze reinforced laminates which were subsequently fabricated and loaded to failure in order to verify the analysis results.

  15. Tungsten fiber reinforced copper matrix composites: A review

    NASA Technical Reports Server (NTRS)

    Mcdanels, David L.

    1989-01-01

    Tungsten fiber reinforced copper matrix (W/Cu) composites have served as an ideal model system with which to analyze the properties of metal matrix composites. A series of research programs were conducted to investigate the stress-strain behavior of W/Cu composites; the effect of fiber content on the strength, modulus, and conductivity of W/Cu composites; and the effect of alloying elements on the behavior of tungsten wire and of W/Cu composites. Later programs investigated the stress-rupture, creep, and impact behavior of these composites at elevated temperatures. Analysis of the results of these programs as allows prediction of the effects of fiber properties, matrix properties, and fiber content on the properties of W/Cu composites. These analyses form the basis for the rule-of-mixtures prediction of composite properties which was universally adopted as the criteria for measuring composite efficiency. In addition, the analyses allows extrapolation of potential properties of other metal matrix composites and are used to select candidate fibers and matrices for development of tungsten fiber reinforced superalloy composite materials for high temperature aircraft and rocket engine turbine applications. The W/Cu composite efforts are summarized, some of the results obtained are described, and an update is provided on more recent work using W/Cu composites as high strength, high thermal conductivity composite materials for high heat flux, elevated temperature applications.

  16. Fatigue evaluation of composite-reinforced, integrally stiffened metal panels

    NASA Technical Reports Server (NTRS)

    Dumesnil, C. E.

    1973-01-01

    The fatigue behavior of composite-reinforced, integrally stiffened metal panels was investigated in combined metal and composite materials subjected to fatigue loading. The systems investigated were aluminum-graphite/epoxy, and aluminum-S glass/epoxy. It was found that the composite material would support the total load at limit stress after the metal had completely failed, and the weight of the composite-metal system would be equal to that of an all metal system which would carry the same total load at limit stress.

  17. Glass matrix composites. I - Graphite fiber reinforced glass

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Bacon, J. F.

    1978-01-01

    An experimental program is described in which graphite fibers of Hercules HMS and HTS, Thornel 300, and Celanese DG-12 were used to reinforce, both uniaxially and biaxially, borosilicate pyrex glass. Composite flexural strength distribution, strength as a function of test temperature, fracture toughness and oxidative stability were determined and shown to be primarily a function of fiber type and the quality of fiber-matrix bond formed during composite fabrication. It is demonstrated that the graphite fiber reinforced glass system offers unique possibilities as a high performance structural material.

  18. Fracture criteria for discontinuously reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Rack, H. J.; Goree, J. G.; Albritton, J.; Ratnarparkhi, P.

    1988-01-01

    The effect of sample configuration on the details of initial crack propagation in discontinuously whisker reinforced aluminum metal matrix composites was investigated. Care was taken to allow direct comparison of fracture toughness values utilizing differing sample configurations and orientations, holding all materials variables constant, e.g., extrusion ration, heat treatment, and chemistry.

  19. Examining graphite reinforcement in composites

    NASA Technical Reports Server (NTRS)

    Sanders, R. E.; Yates, C. I.

    1980-01-01

    Structure of graphite layers in composite parts can be checked by pyrolizing epoxy portion of composite samples. After 2-3 hours in nitrogen atmosphere at 540 C, only graphite fibers remain. These can be separated and checked for proper number, thickness, and orientation.

  20. Micromechanical analysis of fiber-reinforced composites with interfacial phenomena. I - Modeling and analysis of discontinuous fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Saito, Kenji; Iwamoto, Masaharu; Araki, Shigetoshi; Yano, Tadayoshi

    1992-04-01

    A mechanical analysis is presented of fiber-reinforced composite material exhibiting matrix cracking and/or interface sliding between a fiber and a matrix, i.e., the problem of a bridging fiber, by the method of micromechanics. In the case where there are many kinds of inhomogeneities, the interaction between the inhomogeneities, which are neglected in Eshelby's (1961) generally used method, must be taken into consideration. The present method is the extension of the method of Taya and Chou (1981) to the analysis of fiber-reinforced composites with interfacial sliding.

  1. Processing and characterization of smart composite reinforcement

    NASA Astrophysics Data System (ADS)

    Kalamkarov, Alexander L.; Fitzgerald, Stephen B.; MacDonald, Douglas O.; Georgiades, Anastasis V.

    1998-07-01

    The issues of processing and characterization of pultruded smart composite reinforcements with the embedded fiber optic sensors are discussed. These fiber reinforced polymer reinforcements incorporate the optical fiber sensors to provide a strain monitoring of structures. The required modification of the pultrusion processing technology to allow for the incorporation of fiber optic sensors is developed. Fabry Perot and Bragg Grating optical strain sensors were chosen due to their small size and excellent sensitivity. The small diameter of the sensor and optical fiber allow them to be embedded without adversely affecting the strength of the composite. Two types of reinforcement with vinylester resin were used to produce the experimental 9.5 mm diameter rods. The reinforcements were carbon and E-glass fibers. In order to fully characterize the pultrusion process, it was decided to subject the strain sensors separately to each of the variables pertinent to the pultrusion process. Thus, sensors were used to monitor strain caused by compaction pressure in the die, compaction pressure plus standard temperature profile, and finally compaction pressure plus temperature plus resin cure (complete pultrusion process). A strain profile was recorded for each experiment as the sensor travelled through the pultrusion die, and for the cool-down period after the sensor had exited the die.

  2. Ceramic fiber reinforced glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    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.

  3. Vibrations of carbon nanotube-reinforced composites

    NASA Astrophysics Data System (ADS)

    Formica, Giovanni; Lacarbonara, Walter; Alessi, Roberto

    2010-05-01

    This work deals with a study of the vibrational properties of carbon nanotube-reinforced composites by employing an equivalent continuum model based on the Eshelby-Mori-Tanaka approach. The theory allows the calculation of the effective constitutive law of the elastic isotropic medium (matrix) with dispersed elastic inhomogeneities (carbon nanotubes). The devised computational approach is shown to yield predictions in good agreement with the experimentally obtained elastic moduli of composites reinforced with uniformly aligned single-walled carbon nanotubes (CNTs). The primary contribution of the present work deals with the global elastic modal properties of nano-structured composite plates. The investigated composite plates are made of a purely isotropic elastic hosting matrix of three different types (epoxy, rubber, and concrete) with embedded single-walled CNTs. The computations are carried out via a finite element (FE) discretization of the composite plates. The effects of the CNT alignment and volume fraction are studied in depth to assess how the modal properties are influenced both globally and locally. As a major outcome, the lowest natural frequencies of CNT-reinforced rubber composites are shown to increase up to 500 percent.

  4. Composite Materials

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Composites are lighter and stronger than metals. Aramid fibers like Kevlar and Nomex were developed by DuPont Corporation and can be combined in a honeycomb structure which can give an airplane a light, tough structure. Composites can be molded into many aerodynamic shapes eliminating rivets and fasteners. Langley Research Center has tested composites for both aerospace and non-aerospace applications. They are also used in boat hulls, military shelters, etc.

  5. Bioinspired Composites with Spatial and Orientational Control of Reinforcement

    NASA Astrophysics Data System (ADS)

    Demiroers, Ahmet; Studart, Andre; Complex Materials Team

    Living organisms combine soft and hard components to fabricate composite materials with out-standing mechanical properties. The optimum design and assembly of the anisotropic components reinforce the material in specific directions against multidirectional external loads. Although nature does it quite readily, it is still a challenge for material scientists to control the orientation and position of the colloidal components in a matrix. Here, we use external electric and magnetic fields to achieve positional and orientational control over colloid-polymer composites to fabricate mechanically robust materials to capture some of the essential features of natural systems. We first investigated the assembly of spherical micron-sized colloids using dielectrophoresis, as these particles provided an easily accessible and instructive length scale for performing initial experiments. We used dielectrophoresis for spatial control of reinforcing anisotropic components and magnetic fields to provide control over the orientation of these reinforcing constituents. The obtained composites with different orientational and spatial reinforcement showed enhanced mechanical properties, such as wear resistance, which exhibits similarities to tooth enamel. SNSF Ambizione Grant PZ00P2_148040.

  6. New generation fiber reinforced polymer composites incorporating carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Soliman, Eslam

    The last five decades observed an increasing use of fiber reinforced polymer (FRP) composites as alternative construction materials for aerospace and infrastructure. The high specific strength of FRP attracted its use as non-corrosive reinforcement. However, FRP materials were characterized with a relatively low ductility and low shear strength compared with steel reinforcement. On the other hand, carbon nanotubes (CNTs) have been introduced in the last decade as a material with minimal defect that is capable of increasing the mechanical properties of polymer matrices. This dissertation reports experimental investigations on the use of multi-walled carbon nanotubes (MWCNTs) to produce a new generation of FRP composites. The experiments showed significant improvements in the flexure properties of the nanocomposite when functionalized MWCNTs were used. In addition, MWCNTs were used to produce FRP composites in order to examine static, dynamic, and creep behavior. The MWCNTs improved the off-axis tension, off-axis flexure, FRP lap shear joint responses. In addition, they reduced the creep of FRP-concrete interface, enhanced the fracture toughness, and altered the impact resistance significantly. In general, the MWCNTs are found to affect the behaviour of the FRP composites when matrix failure dominates the behaviour. The improvement in the mechanical response with the addition of low contents of MWCNTs would benefit many industrial and military applications such as strengthening structures using FRP composites, composite pipelines, aircrafts, and armoured vehicles.

  7. The mechanics of delamination in fiber-reinforced composite materials. Part 1: Stress singularities and solution structure

    NASA Technical Reports Server (NTRS)

    Wang, S. S.; Choi, I.

    1983-01-01

    The fundamental mechanics of delamination in fiber composite laminates is studied. Mathematical formulation of the problem is based on laminate anisotropic elasticity theory and interlaminar fracture mechanics concepts. Stress singularities and complete solution structures associated with general composite delaminations are determined. For a fully open delamination with traction-free surfaces, oscillatory stress singularities always appear, leading to physically inadmissible field solutions. A refined model is introduced by considering a partially closed delamination with crack surfaces in finite-length contact. Stress singularities associated with a partially closed delamination having frictional crack-surface contact are determined, and are found to be diferent from the inverse square-root one of the frictionless-contact case. In the case of a delamination with very small area of crack closure, a simplified model having a square-root stress singularity is employed by taking the limit of the partially closed delamination. The possible presence of logarithmic-type stress singularity is examined; no logarithmic singularity of any kind is found in the composite delamination problem. Numerical examples of dominant stress singularities are shown for delaminations having crack-tip closure with different frictional coefficients between general (1) and (2) graphite-epoxy composites.

  8. Homogenization of long fiber reinforced composites including fiber bending effects

    NASA Astrophysics Data System (ADS)

    Poulios, Konstantinos; Niordson, Christian F.

    2016-09-01

    This paper presents a homogenization method, which accounts for intrinsic size effects related to the fiber diameter in long fiber reinforced composite materials with two independent constitutive models for the matrix and fiber materials. A new choice of internal kinematic variables allows to maintain the kinematics of the two material phases independent from the assumed constitutive models, so that stress-deformation relationships, can be expressed in the framework of hyper-elasticity and hyper-elastoplasticity for the fiber and the matrix materials respectively. The bending stiffness of the reinforcing fibers is captured by higher order strain terms, resulting in an accurate representation of the micro-mechanical behavior of the composite. Numerical examples show that the accuracy of the proposed model is very close to a non-homogenized finite-element model with an explicit discretization of the matrix and the fibers.

  9. Fiber reinforced composites in prosthodontics – A systematic review

    PubMed Central

    Nayar, Sanjna; Ganesh, R.; Santhosh, S.

    2015-01-01

    Fiber-reinforced composite (FRC), prostheses offer the potential advantages of optimized esthetics, low wear of the opposing dentition and the ability to bond the prosthesis to the abutment teeth, thereby compensating for less-than-optimal abutment tooth retention and resistance form. These prostheses are composed of two types of composite materials: Fiber-composites to build the substructure and hybrid or micro fill particulate composites to create the external veneer surface. This article reviews the various types of FRCs and its mechanical properties. PMID:26015717

  10. Apparatus and process for freeform fabrication of composite reinforcement preforms

    NASA Technical Reports Server (NTRS)

    Yang, Junsheng (Inventor); Wu, Liangwei (Inventor); Liu, Junhai (Inventor); Jang, Bor Z. (Inventor)

    2001-01-01

    A solid freeform fabrication process and apparatus for making a three-dimensional reinforcement shape. The process comprises the steps of (1) operating a multiple-channel material deposition device for dispensing a liquid adhesive composition and selected reinforcement materials at predetermined proportions onto a work surface; (2) during the material deposition process, moving the deposition device and the work surface relative to each other in an X-Y plane defined by first and second directions and in a Z direction orthogonal to the X-Y plane so that the materials are deposited to form a first layer of the shape; (3) repeating these steps to deposit multiple layers for forming a three-dimensional preform shape; and (4) periodically hardening the adhesive to rigidize individual layers of the preform. These steps are preferably executed under the control of a computer system by taking additional steps of (5) creating a geometry of the shape on the computer with the geometry including a plurality of segments defining the preform shape and each segment being preferably coded with a reinforcement composition defining a specific proportion of different reinforcement materials; (6) generating programmed signals corresponding to each of the segments in a predetermined sequence; and (7) moving the deposition device and the work surface relative to each other in response to these programmed signals. Preferably, the system is also operated to generate a support structure for any un-supported feature of the 3-D preform shape.

  11. Rate dependent constitutive models for fiber reinforced polymer composites

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.

    1990-01-01

    A literature survey was conducted to assess the state-of-the-art in rate dependent constitutive models for continuous fiber reinforced polymer matrix composite (PMC) materials. Several recent models which include formulations for describing plasticity, viscoelasticity, viscoplasticity, and rate-dependent phenomenon such as creep and stress relaxation are outlined and compared. When appropriate, these comparisons include brief descriptions of the mathematical formulations, the test procedures required for generating material constants, and details of available data comparing test results to analytical predictions.

  12. Modeling the minimum creep rate of discontinuous lamellar- reinforced composites

    NASA Astrophysics Data System (ADS)

    Bartholomeusz, Michael F.; Wert, John A.

    1995-12-01

    An analytical model has been developed to predict the creep rate of discontinuous lamellar-reinforced composites in which both phases plastically deform. The model incorporates effects associated with lamellar orientation relative to the uniaxial stress axis. For modest to large differences between matrix and reinforcement creep rates, lamellar aspect ratio has a significant impact on composite creep rate. For a prescribed reinforcing phase volume fraction, microstructural inhomogeneity can have a pronounced effect on composite creep properties. In the case of uniaxially aligned rigid lamellar-reinforced composites, an inhomogeneous distribution of reinforcing lamellae in the microstructure substantially increases the composite creep rate. Model results demonstrate that there is no significant improvement in creep resistance for aligned fiber-reinforced composites compared to aligned lamellar-reinforced composites, unless the reinforcing phase is essentially nondeforming relative to the matrix phase.

  13. Mechanics of advanced fiber reinforced lattice composites

    NASA Astrophysics Data System (ADS)

    Fan, Hua-Lin; Zeng, Tao; Fang, Dai-Ning; Yang, Wei

    2010-12-01

    Fiber reinforced lattice composites are light-weight attractive due to their high specific strength and specific stiffness. In the past 10 years, researchers developed three-dimensional (3D) lattice trusses and two-dimensional (2D) lattice grids by various methods including interlacing, weaving, interlocking, filament winding and molding hot-press. The lattice composites have been applied in the fields of radar cross-section reduction, explosive absorption and heat-resistance. In this paper, topologies of the lattice composites, their manufacturing routes, as well as their mechanical and multifunctional applications, were surveyed.

  14. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.; Prewo, K. M.

    1977-01-01

    The results of research for the origination of graphite-fiber reinforced glass matrix composites are presented. The method selected to form the composites consisted of pulling the graphite fiber through a slurry containing powdered glass, winding up the graphite fiber and the glass it picks up on a drum, drying, cutting into segments, loading the tape segment into a graphite die, and hot pressing. During the course of the work, composites were made with a variety of graphite fibers in a glass matrix.

  15. Properties of glass/carbon fiber reinforced epoxy hybrid polymer composites

    NASA Astrophysics Data System (ADS)

    Patel, R. H.; Sevkani, V. R.; Patel, B. R.; Patel, V. B.

    2016-05-01

    Composite Materials are well known for their tailor-made properties. For the fabrication of composites different types of reinforcements are used for different applications. Sometimes for a particular application, one type of reinforcement may not fulfill the requirements. Therefore, more than one type of reinforcements may be used. Thus, the idea of hybrid composites arises. Hybrid composites are made by joining two or more different reinforcements with suitable matrix system. It helps to improve the properties of composite materials. In the present work glass/carbon fiber reinforcement have been used with a matrix triglycidyl ether of tris(m-hydroxy phenyl) phosphate epoxy resin using amine curing agent. Different physical and mechanical properties of the glass, carbon and glass/carbon fiber reinforced polymeric systems have been found out.

  16. Method of producing particulate-reinforced composites and composites produced thereby

    SciTech Connect

    Han, Qingyou; Liu, Zhiwei

    2015-12-29

    A process for producing particle-reinforced composite materials through utilization of an in situ reaction to produce a uniform dispersion of a fine particulate reinforcement phase. The process includes forming a melt of a first material, and then introducing particles of a second material into the melt and subjecting the melt to high-intensity acoustic vibration. A chemical reaction initiates between the first and second materials to produce reaction products in the melt. The reaction products comprise a solid particulate phase, and the high-intensity acoustic vibration fragments and/or separates the reaction products into solid particles that are dispersed in the melt and are smaller than the particles of the second material. Also encompassed are particle-reinforced composite materials produced by such a process.

  17. Method of producing particulate-reinforced composites and composites produced thereby

    DOEpatents

    Han, Qingyou; Liu, Zhiwei

    2013-12-24

    A process for producing particle-reinforced composite materials through utilization of an in situ reaction to produce a uniform dispersion of a fine particulate reinforcement phase. The process includes forming a melt of a first material, and then introducing particles of a second material into the melt and subjecting the melt to high-intensity acoustic vibration. A chemical reaction initiates between the first and second materials to produce reaction products in the melt. The reaction products comprise a solid particulate phase, and the high-intensity acoustic vibration fragments and/or separates the reaction products into solid particles that are dispersed in the melt and are smaller than the particles of the second material. Also encompassed are particle-reinforced composite materials produced by such a process.

  18. Fracture behavior of laminated discontinuously reinforced aluminum material

    SciTech Connect

    Osman, T.M. |; Lewandowski, J.J.; Lesuer, D.R.; Syn, C.K.; Hunt, W.H. Jr

    1994-05-01

    Laminated metallic composites are being developed for applications which require high specific stiffness and fracture resistance. Recent work with laminated discontinuously reinforced aluminum (DRA) materials has demonstrated the potential for marked improvements in stable crack growth resistance via extrinsic toughening. The purpose of this work is to compare the fracture mechanisms and fracture resistance of laminated DRA materials to unlaminated DRA materials. In particular, the production of extensive stable crack growth and the associated improvement in damage tolerance in DRA laminates is documented.

  19. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Thompson, E. R.

    1980-01-01

    High levels of mechanical performance in tension, flexure, fatigue, and creep loading situations of graphite fiber reinforced glass matrix composites are discussed. At test temperatures of up to 813 K it was found that the major limiting factor was the oxidative instability of the reinforcing graphite fibers. Particular points to note include the following: (1) a wide variety of graphite fibers were found to be comparable with the glass matrix composite fabrication process; (2) choice of fiber, to a large extent, controlled resultant composite performance; (3) composite fatigue performance was found to be excellent at both 300 K and 703 K; (4) composite creep and stress rupture at temperatures of up to 813 K was limited by the oxidative stability of the fiber; (5) exceptionally low values of composite thermal expansion coefficient were attributable to the dimensional stability of both matrix and fiber; and (6) component fabricability was demonstrated through the hot pressing of hot sections and brazing using glass and metal joining phases.

  20. Identification of thermodynamically stable ceramic reinforcement materials for iron aluminide matrices

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1990-01-01

    Aluminide-base intermetallic matrix composites are currently being considered as potential high-temperature materials. One of the key factors in the selection of a reinforcement material is its chemical stability in the matrix. In this study, chemical interactions between iron aluminides and several potential reinforcement materials, which include carbides, oxides, borides, and nitrides, are analyzed from thermodynamic considerations. Several chemically compatible reinforcement materials are identified for the iron aluminides with Al concentrations ranging from 40 to 50 at. pct.

  1. Three-dimensional printing fiber reinforced hydrogel composites.

    PubMed

    Bakarich, Shannon E; Gorkin, Robert; in het Panhuis, Marc; Spinks, Geoffrey M

    2014-09-24

    An additive manufacturing process that combines digital modeling and 3D printing was used to prepare fiber reinforced hydrogels in a single-step process. The composite materials were fabricated by selectively pattering a combination of alginate/acrylamide gel precursor solution and an epoxy based UV-curable adhesive (Emax 904 Gel-SC) with an extrusion printer. UV irradiation was used to cure the two inks into a single composite material. Spatial control of fiber distribution within the digital models allowed for the fabrication of a series of materials with a spectrum of swelling behavior and mechanical properties with physical characteristics ranging from soft and wet to hard and dry. A comparison with the "rule of mixtures" was used to show that the swollen composite materials adhere to standard composite theory. A prototype meniscus cartilage was prepared to illustrate the potential application in bioengineering. PMID:25197745

  2. Smart pultruded composite reinforcements incorporating fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Kalamkarov, Alexander L.; Fitzgerald, Stephen B.; MacDonald, Douglas O.; Georgiades, Anastasis V.

    1998-03-01

    The issues of processing, evaluation, experimental testing, and modeling of smart fiber reinforced polymer (FRP) composite materials are discussed. The specific application in view is the use of smart composite reinforcements for a monitoring of innovative bridges and structures. The pultrusion technology for the fabrication of fiber reinforced polymer composites with embedded fiber optic senors (Fabry Perot and Bragg Grating) is developed. The optical sensor/composite material interaction is studied. The tensile and shear properties of the pultruded carbon/vinylester and glass/vinylester rods with and without optical fibers are determined. The microstructural analysis of the smart pultruded FRP is carried out. The interfaces between the resin matrix and the acrylate and polyimide coated optical fibers are examined and interpreted in terms of the coatings's ability to resist high temperature and its compatibility with resin matrix. The strain monitoring during the pultrusion of composite parts using the embedded fiber optic sensors was performed. The strain readings from the sensors and the extensometer were compared in mechanical tensile tests.

  3. Development of Textile Reinforced Composites for Aircraft Structures

    NASA Technical Reports Server (NTRS)

    Dexter, H. Benson

    1998-01-01

    NASA has been a leader in development of composite materials for aircraft applications during the past 25 years. In the early 1980's NASA and others conducted research to improve damage tolerance of composite structures through the use of toughened resins but these resins were not cost-effective. The aircraft industry wanted affordable, robust structures that could withstand the rigors of flight service with minimal damage. The cost and damage tolerance barriers of conventional laminated composites led NASA to focus on new concepts in composites which would incorporate the automated manufacturing methods of the textiles industry and which would incorporate through-the-thickness reinforcements. The NASA Advanced Composites Technology (ACT) Program provided the resources to extensively investigate the application of textile processes to next generation aircraft wing and fuselage structures. This paper discusses advanced textile material forms that have been developed, innovative machine concepts and key technology advancements required for future application of textile reinforced composites in commercial transport aircraft. Multiaxial warp knitting, triaxial braiding and through-the-thickness stitching are the three textile processes that have surfaced as the most promising for further development. Textile reinforced composite structural elements that have been developed in the NASA ACT Program are discussed. Included are braided fuselage frames and window-belt reinforcements, woven/stitched lower fuselage side panels, stitched multiaxial warp knit wing skins, and braided wing stiffeners. In addition, low-cost processing concepts such as resin transfer molding (RTM), resin film infusion (RFI), and vacuum-assisted resin transfer molding (VARTM) are discussed. Process modeling concepts to predict resin flow and cure in textile preforms are also discussed.

  4. Basalt fiber reinforced polymer composites: Processing and properties

    NASA Astrophysics Data System (ADS)

    Liu, Qiang

    A high efficiency rig was designed and built for in-plane permeability measurement of fabric materials. A new data derivation procedure to acquire the flow fluid pattern in the experiment was developed. The measurement results of the in-plane permeability for basalt twill 31 fabric material showed that a high correlation exists between the two principal permeability values for this fabric at 35% fiber volume fraction. This may be the most important scientific contribution made in this thesis. The results from radial measurements corresponded quite well with those from Unidirectional (UD) measurements, which is a well-established technique. No significant differences in mechanical properties were found between basalt fabric reinforced polymer composites and glass composites reinforced by a fabric of similar weave pattern. Aging results indicate that the interfacial region in basalt composites may be more vulnerable to environmental damage than that in glass composites. However, the basalt/epoxy interface may have been more durable than the glass/epoxy interface in tension-tension fatigue because the basalt composites have significantly longer fatigue life. In this thesis, chapter I reviews the literature on fiber reinforced polymer composites, with concentration on permeability measurement, mechanical properties and durability. Chapter II discusses the design of the new rig for in-plane permeability measurement, the new derivation procedure for monitoring of the fluid flow pattern, and the permeability measurement results. Chapter III compares the mechanical properties and durability between basalt fiber and glass fiber reinforced polymer composites. Lastly, chapter IV gives some suggestions and recommendations for future work.

  5. Titanium reinforced boron-polyimide composite

    NASA Technical Reports Server (NTRS)

    Clark, G. A.; Clayton, K. I.

    1969-01-01

    Processing techniques for boron polyimide prepreg were developed whereby composites could be molded under vacuum bag pressure only. A post-cure cycle was developed which resulted in no loss in room temperature mechanical properties of the composite at any time during up to 16 hours at 650 F. A design utilizing laminated titanium foil was developed to achieve a smooth transition of load from the titanium attachment points into the boron-reinforced body of the structure. The box beam test article was subjected to combined bending and torsional loads while exposed to 650 F. Loads were applied incrementally until failure occurred at 83% design limit load.

  6. Carbon Fiber Reinforced Ceramic Composites for Propulsion Applications

    NASA Technical Reports Server (NTRS)

    Shivakumar, Kunigal; Argade, Shyam

    2003-01-01

    This report presents a critical review of the processing techniques for fabricating continuous fiber-reinforced CMCs for possible applications at elevated temperatures. Some of the issues affecting durability of the composite materials such as fiber coatings and cracking of the matrix because of shrinkage in PIP-process are also examined. An assessment of the potential inexpensive processes is also provided. Finally three potential routes of manufacturing C/SiC composites using a technology that NC A&T developed for carbon/carbon composites are outlined. Challenges that will be encountered are also listed.

  7. Reinforcing of Cement Composites by Estabragh Fibres

    NASA Astrophysics Data System (ADS)

    Merati, A. A.

    2014-04-01

    The influence of Estabragh fibres has been studied to improve the performance characteristics of the reinforced cement composites. The concrete shrinkage was evaluated by counting the number of cracks and measuring the width of cracks on the surface of concrete specimens. Although, the Estabragh fibres lose their strength in an alkali environment of cement composites, but, the ability of Estabragh fibres to bridge on the micro cracks in the concrete matrix causes to decrease the width of the cracks on the surface of the concrete samples in comparison with the plain concrete. However, considering the mechanical properties of specimens such as bending strength and impact resistance, the specimens with 0.25 % of Estabragh fibre performed better in all respects compared to the physical and mechanical properties of reinforced cement composite of concrete. Consequently, by adding 0.25 % of Estabragh fibres to the cement composite of concrete, a remarkable improvement in physical and mechanical properties of fibre-containing cement composite is achieved.

  8. Mechanical Properties of Continuous Fiber Reinforced Zirconium Diboride Matrix Composites

    NASA Technical Reports Server (NTRS)

    Stuffle, Kevin; Creegan, Peter; Nowell, Steven; Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

    1995-01-01

    Continuous fiber reinforced zirconium diboride matrix composites, SCS-9a-(RBSiCZrB2)matrix, are being developed for leading edge, rocket nozzle and turbine engine applications. Recently, the composite materials have been characterized for tensile properties to 1250 C, the highest temperature tested. The tensile properties are fiber dominated as the matrix is microcracked on fabrication, but favorable failure characteristic are observed. Compression and shear mechanical testing results will be reported if completed. The effects of fiber volume fraction and matrix density on mechanical properties will be discussed. The target applications of the materials will be discussed. Specific testing being performed towards qualification for these applications will be included.

  9. In Vitro Study of Transverse Strength of Fiber Reinforced Composites

    PubMed Central

    Mosharraf, R.; Hashemi, Z.; Torkan, S.

    2011-01-01

    Objective Reinforcement with fiber is an effective method for considerable improvement in flexural properties of indirect composite resin restorations. The aim of this in-vitro study was to compare the transverse strength of composite resin bars reinforced with pre-impregnated and non-impregnated fibers. Materials and Methods Thirty six bar type composite resin specimens (3×2×25 mm) were constructed in three groups. The first group was the control group (C) without any fiber reinforcement. The specimens in the second group (P) were reinforced with pre-impregnated fibers and the third group (N) with non-impregnated fibers. These specimens were tested by the three-point bending method to measure primary transverse strength. Data were statistically analyzed with one way ANOVA and Tukey’s tests. Results There was a significant difference among the mean primary transverse strength in the three groups (P<0.001). The post-hoc (Tukey) test showed that there was a significant difference between the pre-impregnated and control groups in their primary transverse strength (P<0.001). Regarding deflection, there was also a significant difference among the three groups (P=0.001). There were significant differences among the mean deflection of the control group and two other groups (PC&N<.001 and PC&P=.004), but there was no significant difference between the non-and pre-impregnated groups (PN&P=.813). Conclusion Within the limitations of this study, it was concluded that reinforcement with fiber considerably increased the transverse strength of composite resin specimens, but impregnation of the fiber used implemented no significant difference in the transverse strength of composite resin samples. PMID:22457836

  10. Fracture Analysis of Particulate Reinforced Metal Matrix Composites

    NASA Technical Reports Server (NTRS)

    Min, James B.; Cornie, James A.

    2013-01-01

    A fracture analysis of highly loaded particulate reinforced composites was performed using laser moire interferometry to measure the displacements within the plastic zone at the tip of an advancing crack. Ten castings were made of five different particulate reinforcement-aluminum alloy combinations. Each casting included net-shape specimens which were used for the evaluation of fracture toughness, tensile properties, and flexure properties resulting in an extensive materials properties data. Measured fracture toughness range from 14.1 MPa for an alumina reinforced 356 aluminum alloy to 23.9 MPa for a silicon carbide reinforced 2214 aluminum alloy. For the combination of these K(sub Ic) values and the measured tensile strengths, the compact tension specimens were too thin to yield true plane strain K(sub Ic) values. All materials exhibited brittle behavior characterized by very small tensile ductility suggesting that successful application of these materials requires that the design stresses be below the elastic limit. Probabilistic design principles similar to those used with ceramics are recommended when using these materials. Such principles would include the use of experimentally determined design allowables. In the absence of thorough testing, a design allowable stress of 60 percent of the measured ultimate tensile stress is recommended.

  11. Modeling of short fiber reinforced injection moulded composite

    NASA Astrophysics Data System (ADS)

    Kulkarni, A.; Aswini, N.; Dandekar, C. R.; Makhe, S.

    2012-09-01

    A micromechanics based finite element model (FEM) is developed to facilitate the design of a new production quality fiber reinforced plastic injection molded part. The composite part under study is composed of a polyetheretherketone (PEEK) matrix reinforced with 30% by volume fraction of short carbon fibers. The constitutive material models are obtained by using micromechanics based homogenization theories. The analysis is carried out by successfully coupling two commercial codes, Moldflow and ANSYS. Moldflow software is used to predict the fiber orientation by considering the flow kinetics and molding parameters. Material models are inputted into the commercial software ANSYS as per the predicted fiber orientation and the structural analysis is carried out. Thus in the present approach a coupling between two commercial codes namely Moldflow and ANSYS has been established to enable the analysis of the short fiber reinforced injection moulded composite parts. The load-deflection curve is obtained based on three constitutive material model namely an isotropy, transversely isotropy and orthotropy. Average values of the predicted quantities are compared to experimental results, obtaining a good correlation. In this manner, the coupled Moldflow-ANSYS model successfully predicts the load deflection curve of a composite injection molded part.

  12. Finite Element Analysis of Drilling of Carbon Fibre Reinforced Composites

    NASA Astrophysics Data System (ADS)

    Isbilir, Ozden; Ghassemieh, Elaheh

    2012-06-01

    Despite the increased applications of the composite materials in aerospace due to their exceptional physical and mechanical properties, the machining of composites remains a challenge. Fibre reinforced laminated composites are prone to different damages during machining process such as delamination, fibre pull-out, microcracks, thermal damages. Optimization of the drilling process parameters can reduces the probability of these damages. In the current research, a 3D finite element (FE) model is developed of the process of drilling in the carbon fibre reinforced composite (CFC). The FE model is used to investigate the effects of cutting speed and feed rate on thrust force, torque and delamination in the drilling of carbon fiber reinforced laminated composite. A mesoscale FE model taking into account of the different oriented plies and interfaces has been proposed to predict different damage modes in the plies and delamination. For validation purposes, experimental drilling tests have been performed and compared to the results of the finite element analysis. Using Matlab a digital image analysis code has been developed to assess the delamination factor produced in CFC as a result of drilling.

  13. Analysis/design of strip reinforced random composites /strip hybrids/

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1978-01-01

    Results are described which were obtained by applying advanced analysis methods and composite mechanics to a strip-reinforced random composite square panel with fixed ends. This was done in order to illustrate the use of these methods for the apriori assessment of the composite panel when subjected to complex loading conditions. The panel was assumed to be of E-Glass/Random Composite. The strips were assumed to be of three advanced unidirectional composites to cover a range of low, intermediate, and high modulus stiffness. The panels were assumed to be subjected to complex loadings to assess their adequacy as load-carrying members in auto body, aircraft engine nacelle, and windmill blade applications. The results show that strip hybrid panels can be several times more structurally efficient than the random composite base materials. Some of the results are presented in graphical form and procedures are described for use of these graphs as guides for preliminary design of strip hybrids.

  14. Analysis/design of strip reinforced random composites (strip hybrids)

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1978-01-01

    Advanced analysis methods and composite mechanics were applied to a strip-reinforced random composite square panel with fixed ends to illustrate the use of these methods for the a priori assessment of the composite panel when subjected to complex loading conditions. The panel was assumed to be of E-glass random composite. The strips were assumed to be of three advanced unidirectional composites to cover a range of low, intermediate, and high modulus stiffness. The panels were assumed to be subjected to complex loadings to assess their adequacy as load-carrying members in auto body, aircraft engine nacelle and windmill blade applications. The results show that strip hybrid panels can be several times more structurally efficient than the random composite base materials. Some of the results are presented in graphical form and procedures are described for use of these graphs as guides for preliminary design of strip hybrids.

  15. Initial evaluation of continuous fiber reinforced NiAl composites

    NASA Technical Reports Server (NTRS)

    Noebe, R. D.; Bowman, R. R.; Eldridge, J. I.

    1990-01-01

    NiAl is being evaluated as a potential matrix material as part of an overall program to develop and understand high-temperature structural composites. Currently, continuous fiber composites have been fabricated by the powder cloth technique incorporating either W(218) or single crystal Al2O3 fibers as reinforcements in both binary NiAl and a solute strengthened NiAl(.05 at. pct Zr) matrix. Initial evaluation of these composite systems have included: fiber push-out testing to measure matrix/fiber bond strengths, bend testing to determine strength as a function of temperature and composite structure, and thermal cycling to establish the effect of matrix and fiber properties on composite life. The effect of matrix/fiber bond strength and matrix strength on several composite properties will be discussed.

  16. Mullite fiber reinforced reaction bonded Si3N4 composites

    NASA Technical Reports Server (NTRS)

    Saleh, T.; Sayir, A.; Lightfoot, A.; Haggerty, J.

    1996-01-01

    Fracture toughnesses of brittle ceramic materials have been improved by introducing reinforcements and carefully tailored interface layers. Silicon carbide and Si3N4 have been emphasized as matrices of structural composites intended for high temperature service because they combine excellent mechanical, chemical, thermal and physical properties. Both matrices have been successfully toughened with SiC fibers, whiskers and particles for ceramic matrix composite (CMC) parts made by sintering, hot pressing or reaction forming processes. These SiC reinforced CMCs have exhibited significantly improved toughnesses at low and intermediate temperature levels, as well as retention of properties at high temperatures for selected exposures; however, they are vulnerable to attack from elevated temperature dry and wet oxidizing atmospheres after the matrix has cracked. Property degradation results from oxidation of interface layers and/or reinforcements. The problem is particularly acute for small diameter (-20 tim) polymer derived SiC fibers used for weavable toes. This research explored opportunities for reinforcing Si3N4 matrices with fibers having improved environmental stability; the findings should also be applicable to SiC matrix CMCs.

  17. Coupled heating/forming optimization of knitted reinforced composites

    NASA Astrophysics Data System (ADS)

    Pancrace, Johann

    The feasibility of knitted fabric reinforcement for highly flexible composites has been investigated for the thermoforming process. The composite sheets were made through compression molding before being shaped. We used thermoplastic elastomers as matrices: Thermoplastic Elastomers and Thermoplastic Olefins. The knit reinforcement was provided by jersey knitted fabrics of polyester fibers. We first introduced the fundamentals involved in the study. The manufacturing is presented through compression molding and thermoforming. The latter is a two-step process: IR heating and plug/pressure assisted deformations. For the IR heating phase, several material properties have been characterized: the emissivity of matrices, absorption, reflection and transmission of radiations in the composite structure have been studied. We particularly paid attention to the reflection on the composite surfaces. The non-reflected or useful radiations leading to the heating are quantified and simulated for three emitter-composite configurations. It has been found that the emitter temperatures and the angle of incidence have significant roles in the IR heating phase. Thermal properties such as calorific capacity and thermal conductivity of the composites were also presented. Thermograms were carried out with an IR camera. Equipment and Thermogram acquisitions were both presented. Optimization of emitters was performed for a three emitter system. The objective function method has been illustrated. Regarding mechanical purposes, the characterizations of the matrices, reinforcements and flexible composites have been carried out. The studied loadings were uniaxial traction, pure shear and biaxial inflation. For the uniaxial extension, both the reinforcement and the composite were found highly anisotropic regarding the orientation of the loading toward the coursewise of the fabric. The resulting strains and stresses to rupture are also found anisotropic. However, for pure shear loading we observed

  18. Ballistic impact fatigue behavior of spectra fiber-reinforced composites

    SciTech Connect

    Song, J.W.; Lee, B.L.

    1994-12-31

    The study examined the penetration failure mechanisms of Spectra fiber-reinforced composites under ballistic impact and assessed the roles played by resin matrix properties in controlling the process of impact damage propagation. In order to observe gradual propagation of damage, a concept of impact fatigue was introduced by subjecting the composite plates to a multiple number of repeated ballistic impact. When the striking velocity of,a projectile was below the ballistic limit, repeated impact resulted in a progressive growth of local delamination until full penetration of the projectile occurs. Preliminary results indicated that the vinyl ester resin matrix composites have a higher ballistic limit and longer impact fatigue life at a given striking velocity than the polyurethane matrix composites. Based on the test results of dynamic mechanical properties, more localized delamination of polyurethane matrix composites was attributed to a greater degree of stress wave attenuation and lower bending stiffness of material system.

  19. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Thompson, E. R.

    1981-01-01

    A broad group of fibers and matrices were combined to create a wide range of composite properties. Primary material fabrication procedures were developed which readily permit the fabrication of flat plate and shaped composites. Composite mechanical properties were measured under a wide range of test conditions. Tensile, flexure mechanical fatigue, thermal fatigue, fracture toughness, and fatigue crack growth resistance were evaluated. Selected fiber-matrix combinations were shown to maintain their strength at up to 1300 K when tested in an inert atmosphere. Composite high temperature mechanical properties were shown to be limited primarily by the oxidation resistance of the graphite fibers. Composite thermal dimensional stability was measured and found to be excellent.

  20. Lightweight, Thermally Conductive Composite Material

    NASA Technical Reports Server (NTRS)

    Sharp, G. Richard; Loftin, Timothy A.

    1990-01-01

    Aluminum reinforced with carbon fibers superior to copper in some respects. Lightweight composite material has high thermal conductivity. Consists of aluminum matrix containing graphite fibers, all oriented in same direction. Available as sheets, tubes, and bars. Thermal conductivity of composite along fibers rises above that of pure copper over substantial range of temperatures. Graphite/aluminum composite useful in variety of heat-transfer applications in which reduction of weight critical. Used to conduct heat in high-density, high-speed integrated-circuit packages for computers and in base plates for electronic equipment. Also used to carry heat away from leading edges of wings in high-speed airplanes.

  1. Processing and evaluation of smart composite reinforcement

    NASA Astrophysics Data System (ADS)

    Kalamkarov, Alexander L.; Fitzgerald, Stephen B.; MacDonald, Douglas O.

    1997-11-01

    The issues of processing and evaluation of pultruded smart composite reinforcements with embedded fiber optic sensors are discussed. The required modification of the pultrusion processing technology to allow for the incorporation of fiber optic sensors is developed. In order to fully evaluate the loads imposed on the Fabry Perot fiber optic sensors during the pultrusion process, the strain sensors were subjected to the separate variables of the total process. The following data was obtained for the carbon fiber rods. Compaction pressure alone caused negligible residual strain. The temperature profile caused a similar strain profile over the length of the pultrusion die. For the total pultrusion process, the residual strain after cooling appeared to present somewhat of a problem. For several experiments, the residual strain after exiting the pultrusion die was in the range of plus 200 to 400 microstrain, after which the sensors ceased to function. Calculations indicated that the radial shrinkage of the carbon fiber rods may have been sufficient to cause failure of the Fabry Perot sensors. A special procedure of reinforcing sensors prior to embedding them into the composite was successful in allowing the sensors to survive with only a slightly negative residual strain.

  2. Covering of fiber-reinforced composite bars by adhesive materials, is it necessary to improve the bond strength of lingual retainers?

    PubMed Central

    Heravi, Farzin; Kerayechian, Navid; Moazzami, Saied Mostafa; Shafaee, Hooman; Heravi, Parya

    2015-01-01

    Objectives: The objectives were to evaluate the shear bond strength (SBS) of fiber-reinforced composite (FRC) retainers when bonding them to teeth with and without covering the FRC bars using two different adhesive systems. Materials and Methods: Hundred and twenty extracted human maxillary premolars were randomly divided into eight groups (n = 15). FRC bars (4 mm length, Everstick Ortho®, Stick Tech, Oy, Turku, Finland) were bonded to the proximal (distal) surfaces of the teeth using two different adhesives (Tetric Flow [TF, Ivoclar Vivadent, Switzerland] and resin-modified glass ionomer cement [RMGIC, ODP, Vista, CA, USA]) with and without covering with the same adhesive. Specimens were exposed to thermocycling (625 cycles per day [5–55°C, intervals: 30 s] for 8 days). The SBS test was then performed using the universal testing machine (Zwick, GMBH, Ulm, Germany). After debonding, the remaining adhesive on the teeth was recorded by the adhesive remnant index (0–3). Results: The lowest mean SBS (standard deviation) was found in the TF group without covering with adhesive (12.6 [2.11] MPa), and the highest bond strength was in the TF group with covering with adhesive (16.01 [1.09] MPa). Overall, the uncovered RMGIC (15.65 [3.57] MPa) provided a higher SBS compared to the uncovered TF. Covering of FRC with TF led to a significant increase in SBS (P = 0.001), but this was not true for RMGIC (P = 0.807). Thermal cycling did not significantly change the SBS values (P = 0.537). Overall, eight groups were statistically different (ANOVA test, F = 3.32, P = 0.034), but no significant differences in bond failure locations were found between the groups (Fisher's exact tests, P = 0.92). Conclusions: The present findings showed no significant differences between SBS of FRC bars with and without covering by RMGIC. However, when using TF, there was a significant difference in SBS measurements between covering and noncovering groups. Therefore, the use of RMGIC without

  3. Plastic matrix composites with continuous fiber reinforcement

    SciTech Connect

    1991-09-19

    Most plastic resins are not suitable for structural applications. Although many resins are extremely tough, most lack strength, stiffness, and deform under load with time. By mixing strong, stiff, fibrous materials into the plastic matrix, a variety of structural composite materials can be formed. The properties of these composites can be tailored by fiber selection, orientation, and other factors to suit specific applications. The advantages and disadvantages of fiberglass, carbon-graphite, aramid (Kevlar 49), and boron fibers are summarized.

  4. Microscopic mechanism of reinforcement and conductivity in polymer nanocomposite materials

    NASA Astrophysics Data System (ADS)

    Chang, Tae-Eun

    Modification of polymers by adding various nano-particles is an important method to obtain effective enhancement of materials properties. Within this class of materials, carbon nanotubes (CNT) are among the most studied materials for polymer reinforcement due to their extraordinary mechanical properties, superior thermal and electronic properties, and high aspect ratio. However, to unlock the potential of CNTs for applications, CNTs must be well dispersed in a polymer matrix and the microscopic mechanism of polymer reinforcement by CNTs must be understood. In this study, single-wall carbon nanotube (SWNT) composites with polypropylene (PP)-SWNT and polystyrene (PS)-SWNT were prepared and analyzed. Microscopic study of the mechanism of reinforcement and conductivity by SWNT included Raman spectroscopy, wide-angle X-ray diffraction (WAXD) and dielectric measurement. For PP-SWNT composites, tensile tests show a three times increase in the Young's modulus with addition of only 1 wt% SWNT, and much diminished increase of modulus with further increase in SWNT concentration. For PS-SWNT composites, well-dispersed SWNT/PS composite has been produced, using initial annealing of SWNT and optimum sonication conditions. The studies on the tangential mode in the Raman spectra and TEM indicated well-dispersed SWNTs in a PS matrix. We show that conductivity appears in composites already at very low concentrations, hinting at the formation of a 'percolative' network even below 0.5% of SWNT. The Raman studies for both composites show good transfer of the applied stress from the polymer matrices to SWNTs. However, no significant improvement of mechanical property is observed for PS-SWNT composites. The reason for only a slight increase of mechanical property remains unknown.

  5. Fracture of fiber-reinforced composites analyzed via acoustic emission.

    PubMed

    Ereifej, Nadia S; Oweis, Yara G; Altarawneh, Sandra K

    2015-01-01

    This study investigated the fracture resistance of composite resins using a three-point bending test and acoustic emission (AE) analysis. Three groups of specimens (n=15) were prepared: non-reinforced BelleGlass HP composite (NRC), unidirectional (UFRC) and multidirectional (MFRC) fiber-reinforced groups which respectively incorporated unidirectional Stick and multidirectional StickNet fibers. Specimens were loaded to failure in a universal testing machine while an AE system was used to detect audible signals. Initial fracture strengths and AE amplitudes were significantly lower than those at final fracture in all groups (p<0.05). Initial fracture strength of UFRC (170.0 MPa) was significantly higher than MFRC (124.6 MPa) and NRC (87.9 MPa). Final fracture strength of UFRC (198.1 MPa) was also significantly higher than MFRC (151.0 MPa) and NRC (109.2 MPa). Initial and final fracture strengths were significantly correlated (r=0.971). It was concluded that fiber reinforcement improved the fracture resistance of composite resin materials and the monitoring of acoustic signals revealed significant information regarding the fracture process. PMID:25904176

  6. Compression response of thick layer composite laminates with through-the-thickness reinforcement

    NASA Technical Reports Server (NTRS)

    Farley, Gary L.; Smith, Barry T.; Maiden, Janice

    1992-01-01

    Compression and compression-after-impact (CAI) tests were conducted on seven different AS4-3501-6 (0/90) 0.64-cm thick composite laminates. Four of the seven laminates had through-the-thickness (TTT) reinforcement fibers. Two TTT reinforcement methods, stitching and integral weaving, and two reinforcement fibers, Kevlar and carbon, were used. The remaining three laminates were made without TTT reinforcements and were tested to establish a baseline for comparison with the laminates having TTT reinforcement. Six of the seven laminates consisted of nine thick layers whereas the seventh material was composed of 46 thin plies. The use of thick-layer material has the potential for reducing structural part cost because of the reduced part count (layers of material). The compression strengths of the TTT reinforced laminates were approximately one half those of the materials without TTT reinforcements. However, the CAI strengths of the TTT reinforced materials were approximately twice those of materials without TTT reinforcements. The improvement in CAI strength is due to an increase in interlaminar strength produced by the TTT reinforcement. Stitched laminates had slightly higher compression and CAI strengths than the integrally woven laminates.

  7. Creep behavior of tungsten fiber reinforced niobium metal matrix composites

    NASA Technical Reports Server (NTRS)

    Grobstein, T. L.

    1989-01-01

    Tungsten fiber reinforced niobium metal matrix composites were evaluated for use in space nuclear power conversion systems. The composite panels were fabricated using the arc-spray monotape technique at the NASA Lewis Research Center. The creep behavior of W/Nb composite material was determined at 1400 and 1500 K in vacuum over a wide range of applied loads. The time to reach 1 percent strain, the time to rupture, and the minimum creep rate were measured. The W/Nb composites exceeded the properties of monolithic niobium alloys significantly even when compared on a strength to density basis. The effect of fiber orientation on the creep strength also was evaluated. Kirkendall void formation was observed at the fiber/matrix interface; the void distribution differed depending on the fiber orientation relative to the stress axis. A relationship was found between the fiber orientation and the creep strength.

  8. Creep behavior of tungsten fiber reinforced niobium metal matrix composites

    NASA Technical Reports Server (NTRS)

    Grobstein, Toni L.

    1992-01-01

    Tungsten fiber reinforced niobium metal matrix composites were evaluated for use in space nuclear power conversion systems. The composite panels were fabricated using the arc-spray monotape technique at the NASA Lewis Research Center. The creep behavior of W/Nb composite material was determined at 1400 and 1500 K in vacuum over a wide range of applied loads. The time to reach 1 percent strain, the time to rupture, and the minimum creep rate were measured. The W/Nb composites exceeded the properties of monolithic niobium alloys significantly even when compared creep strength also was evaluated. Kirkendall void formation was observed at the fiber/matrix interface; the void distribution differed depending the fiber orientation relative to the stress axis. A relationship was found between the fiber orientation and the creep strength.

  9. Puncture-Healing Thermoplastic Resin Carbon-Fiber-Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Gordon, Keith L. (Inventor); Siochi, Emilie J. (Inventor); Grimsley, Brian W. (Inventor); Cano, Roberto J. (Inventor); Czabaj, Michael W. (Inventor)

    2015-01-01

    A composite comprising a combination of a self-healing polymer matrix and a carbon fiber reinforcement is described. In one embodiment, the matrix is a polybutadiene graft copolymer matrix, such as polybutadiene graft copolymer comprising poly(butadiene)-graft-poly(methyl acrylate-co-acrylonitrile). A method of fabricating the composite is also described, comprising the steps of manufacturing a pre-impregnated unidirectional carbon fiber preform by wetting a plurality of carbon fibers with a solution, the solution comprising a self-healing polymer and a solvent, and curing the preform. A method of repairing a structure made from the composite of the invention is described. A novel prepreg material used to manufacture the composite of the invention is described.

  10. Design aid for shear strengthening of reinforced concrete T-joints using carbon fiber reinforced plastic composites

    NASA Astrophysics Data System (ADS)

    Gergely, Ioan

    The research presented in the present work focuses on the shear strengthening of beam column joints using carbon fiber composites, a material considered in seismic retrofit in recent years more than any other new material. These composites, or fiber reinforced polymers, offer huge advantages over structural steel reinforced concrete or timber. A few of these advantages are the superior resistance to corrosion, high stiffness to weight and strength to weight ratios, and the ability to control the material's behavior by selecting the orientation of the fibers. The design and field application research on reinforced concrete cap beam-column joints includes analytical investigations using pushover analysis; design of carbon fiber layout, experimental tests and field applications. Several beam column joints have been tested recently with design variables as the type of composite system, fiber orientation and the width of carbon fiber sheets. The surface preparation has been found to be critical for the bond between concrete and composite material, which is the most important factor in joint shear strengthening. The final goal of this thesis is to develop design aids for retrofitting reinforced concrete beam column joints. Two bridge bents were tested on the Interstate-15 corridor. One bent was tested in the as-is condition. Carbon fiber reinforced plastic composite sheets were used to externally reinforce the second bridge bent. By applying the composite, the displacement ductility has been doubled, and the bent overall lateral load capacity has been increased as well. The finite element model (using DRAIN-2DX) was calibrated to model the actual stiffness of the supports. The results were similar to the experimental findings.

  11. Asymptotic Analysis of Fiber-Reinforced Composites of Hexagonal Structure

    NASA Astrophysics Data System (ADS)

    Kalamkarov, Alexander L.; Andrianov, Igor V.; Pacheco, Pedro M. C. L.; Savi, Marcelo A.; Starushenko, Galina A.

    2016-08-01

    The fiber-reinforced composite materials with periodic cylindrical inclusions of a circular cross-section arranged in a hexagonal array are analyzed. The governing analytical relations of the thermal conductivity problem for such composites are obtained using the asymptotic homogenization method. The lubrication theory is applied for the asymptotic solution of the unit cell problems in the cases of inclusions of large and close to limit diameters, and for inclusions with high conductivity. The lubrication method is further generalized to the cases of finite values of the physical properties of inclusions, as well as for the cases of medium-sized inclusions. The analytical formulas for the effective coefficient of thermal conductivity of the fiber-reinforced composite materials of a hexagonal structure are derived in the cases of small conductivity of inclusions, as well as in the cases of extremely low conductivity of inclusions. The three-phase composite model (TPhM) is applied for solving the unit cell problems in the cases of the inclusions with small diameters, and the asymptotic analysis of the obtained solutions is performed for inclusions of small sizes. The obtained results are analyzed and illustrated graphically, and the limits of their applicability are evaluated. They are compared with the known numerical and asymptotic data in some particular cases, and very good agreement is demonstrated.

  12. Ceramic composites reinforced with modified silicon carbide whiskers

    DOEpatents

    Tiegs, Terry N.; Lindemer, Terrence B.

    1990-01-01

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  13. Nondestructive testing of externally reinforced structures for seismic retrofitting using flax fiber reinforced polymer (FFRP) composites

    NASA Astrophysics Data System (ADS)

    Ibarra-Castanedo, C.; Sfarra, S.; Paoletti, D.; Bendada, A.; Maldague, X.

    2013-05-01

    Natural fibers constitute an interesting alternative to synthetic fibers, e.g. glass and carbon, for the production of composites due to their environmental and economic advantages. The strength of natural fiber composites is on average lower compared to their synthetic counterparts. Nevertheless, natural fibers such as flax, among other bast fibers (jute, kenaf, ramie and hemp), are serious candidates for seismic retrofitting applications given that their mechanical properties are more suitable for dynamic loads. Strengthening of structures is performed by impregnating flax fiber reinforced polymers (FFRP) fabrics with epoxy resin and applying them to the component of interest, increasing in this way the load and deformation capacities of the building, while preserving its stiffness and dynamic properties. The reinforced areas are however prompt to debonding if the fabrics are not mounted properly. Nondestructive testing is therefore required to verify that the fabric is uniformly installed and that there are no air gaps or foreign materials that could instigate debonding. In this work, the use of active infrared thermography was investigated for the assessment of (1) a laboratory specimen reinforced with FFRP and containing several artificial defects; and (2) an actual FFRP retrofitted masonry wall in the Faculty of Engineering of the University of L'Aquila (Italy) that was seriously affected by the 2009 earthquake. Thermographic data was processed by advanced signal processing techniques, and post-processed by computing the watershed lines to locate suspected areas. Results coming from the academic specimen were compared to digital speckle photography and holographic interferometry images.

  14. Reinforced composite sealants for solid oxide fuel cell applications

    NASA Astrophysics Data System (ADS)

    Gross, Sonja M.; Federmann, Dirk; Remmel, Josef; Pap, Michael

    Glass-ceramic sealants are commonly used as joining materials for planar solid oxide fuel cells stacks. Several requirements need to be fulfilled by these materials: beside of electrical insulation and appropriate thermal expansion, a good adhesion on the ceramic and metallic components of a SOFC stack is necessary to form a gas-tight joint. Even though the joining process might have been successful, failures and leaks often occur during the stack operation due to fracture of the brittle material under thermal stresses or during thermal cycling of the components. This study focusses on composite materials consisting of a glass matrix based on the system of BaO-CaO-SiO 2 and various filler materials, e.g. yttria-stabilized zirconia fibres or particles and silver particles. In order to evaluate a possible reinforcing influence of the filler material of the composite, tensile strength tests were carried out on circular butt joints. The highest strength values were found for the composite material with addition of silver particles, followed by the glass matrix itself without any filler addition and the lowest values were measured for the composite with YSZ particles. SEM investigations of cross-sections of the joints elucidated these results by the microstructure of the glass-ceramic sealants.

  15. Anomaly detection of microstructural defects in continuous fiber reinforced composites

    NASA Astrophysics Data System (ADS)

    Bricker, Stephen; Simmons, J. P.; Przybyla, Craig; Hardie, Russell

    2015-03-01

    Ceramic matrix composites (CMC) with continuous fiber reinforcements have the potential to enable the next generation of high speed hypersonic vehicles and/or significant improvements in gas turbine engine performance due to their exhibited toughness when subjected to high mechanical loads at extreme temperatures (2200F+). Reinforced fiber composites (RFC) provide increased fracture toughness, crack growth resistance, and strength, though little is known about how stochastic variation and imperfections in the material effect material properties. In this work, tools are developed for quantifying anomalies within the microstructure at several scales. The detection and characterization of anomalous microstructure is a critical step in linking production techniques to properties, as well as in accurate material simulation and property prediction for the integrated computation materials engineering (ICME) of RFC based components. It is desired to find statistical outliers for any number of material characteristics such as fibers, fiber coatings, and pores. Here, fiber orientation, or `velocity', and `velocity' gradient are developed and examined for anomalous behavior. Categorizing anomalous behavior in the CMC is approached by multivariate Gaussian mixture modeling. A Gaussian mixture is employed to estimate the probability density function (PDF) of the features in question, and anomalies are classified by their likelihood of belonging to the statistical normal behavior for that feature.

  16. Characterization of interfacial failure in SiC reinforced Si3N4 matrix composite material by both fiber push-out testing and Auger electron spectroscopy

    NASA Technical Reports Server (NTRS)

    Eldridge, J. I.; Honecy, F. S.

    1990-01-01

    AES depth profiling and a fiber push-out test for interfacial shear-strength determination have been used to ascertain the mechanical/chemical properties of the fiber/matrix interface in SiC-reinforced reaction-bonded Si3N4, with attention to the weak point where interfacial failure occurs. In the cases of both composite fracture and fiber push-outs, the interfacial failure occurred either between the two C-rich coatings that are present on the double-coated SiC fibers, or between the inner C-rich coating and the SiC fiber. Interface failure occurs at points of very abrupt concentration changes.

  17. [Fiber-reinforced composite in fixed prosthodontics].

    PubMed

    Pilo, R; Abu Rass, Z; Shmidt, A

    2010-07-01

    Fiber reinforced composite (FRC) is composed of resin matrix and fibers filler. Common types of fibers: polyethylene, carbon and glass. Fibers can be continuous and aligned, discontinuous and aligned, discontinuous and randomly oriented. The architecture of the fibers is unidirectional, woven or braided. The two main types are: dry fibers or impregnated. Inclusion of fibers to resin composite increased its average flexural strength in 100-200 MPa. FRC can be utilized by the dentist in direct approach (splinting, temporary winged bridge) or indirect approach (laboratory made fixed partial denture). Laboratory fixed partial denture (FPD) is made from FRC substructure and Hybrid/Microfill particulate composite veneer. Main indications: interim temporary FPD or FPD in cases of questionable abutment teeth, in aesthetic cases where All Ceram FPD is not feasible. Retention is attained by adhesive cementation to minimally prepared teeth or to conventionally prepared teeth; other options are inlay-onlay bridges or hybrid bridges. Contraindications are: poor hygiene, inability to control humidity, parafunction habits, and more than two pontics. Survival rate of FRC FPD over 5 years is 75%, lower compared to porcelain fused to metal FPD which is 95%. Main reasons for failure are: fracture of framework and delamination of the veneer. Part of the failures is repairable. PMID:21485555

  18. Metal aircraft structural elements reinforced with graphite filamentary composites

    NASA Technical Reports Server (NTRS)

    Berg, K. R.; Ramsey, J.

    1972-01-01

    Strain compatibility equations are used to evaluate the thermal stresses existing when unidirectional graphite composites are bonded to aluminum structures. Based on thermal stresses and optimum placement of the composite, skin-stringer aluminum panels are optimized for minimum weight compression panels with selective composite reinforcement. Composite reinforced skin-stringer panels are thermal cycled to determine the effect of thermal fatigue on structural integrity. Both cycled and uncycled panels are tested in compression and tension. Test results are correlated with predicted loads. Use of filamentary graphite composites is an efficient method of reinforcing metal structures, but care must be taken to minimize thermal stresses.

  19. Calculation of the relative uniformity coefficient on the green composites reinforced with cotton and hemp fabric

    NASA Astrophysics Data System (ADS)

    Baciu, Florin; Hadǎr, Anton; Sava, Mihaela; Marinel, Stǎnescu Marius; Bolcu, Dumitru

    2016-06-01

    In this paper it is studied the influence of discontinuities on elastic and mechanical properties of green composite materials (reinforced with fabric of cotton or hemp). In addition, it is studied the way variations of the volume f the reinforcement influences the elasticity modulus and the tensile strength for the studied composite materials. In order to appreciate the difference in properties between different areas of the composite material, and also the dimensions of the defective areas, we have introduced a relative uniformity coefficient with which the mechanical behavior of the studied composite is compared with a reference composite. To validate the theoretical results we have obtained we made some experiments, using green composites reinforced with fabric, with different imperfection introduced special by cutting the fabric.

  20. Stress corrosion of fiberglass-reinforced (FRP) composites

    SciTech Connect

    Sapalidis, S.N.; Hogg, P.J.; Kelley, D.H.; Youd, S.J.

    1997-12-01

    The stress corrosion characteristics of uniaxial glass fiber reinforced thermosetting resin composites have been examined in Hydrochloric acid at room temperature and 80 C. A simple technique based on linear elastic fracture mechanisms (LEFM) is presented for characterizing crack growth in these materials subjected to hostile acidic environments. The environmental stress corrosion cracking is investigated both for different types of resin and different types of glass fiber reinforcements. Two matrices were used: Bis-A epoxy vinyl ester resin (based on Bisphenol-A epoxy resin) and novolac epoxy vinyl ester resin (based on epoxidized novolac resin). Two glass fiber types were employed: standard E-glass fiber and R, a special type of E-glass with superior acid resistance. Model experiments using a modified double cantilever beam test with static loading have been carried out on unidirectional composite specimens in 1M Hydrochloric acid solution at room temperature and 80 C. The rate of rack growth in the specimens depends on the applied stress, the temperature and the environment. Consequently, the lifetime of a component or structure made from GRP, subjected to stress corrosion conditions, could be predicted provided the dependence of crack growth rate on stress intensity at the crack tip is known. Scanning electron microscopy studies of the specimen fracture surfaces have identified the characteristic failure mechanisms. The most thing findings of this work is that the selection of epoxy vinyl ester resins reinforced with R fiber exhibited superior resistance to crack growth at 80 C compared to similar E-glass reinforced composites at room temperatures.

  1. Self Healing Fibre-reinforced Polymer Composites: an Overview

    NASA Astrophysics Data System (ADS)

    Bond, Ian P.; Trask, Richard S.; Williams, Hugo R.; Williams, Gareth J.

    Lightweight, high-strength, high-stiffness fibre-reinforced polymer composite materials are leading contenders as component materials to improve the efficiency and sustainability of many forms of transport. For example, their widespread use is critical to the success of advanced engineering applications, such as the Boeing 787 and Airbus A380. Such materials typically comprise complex architectures of fine fibrous reinforcement e.g. carbon or glass, dispersed within a bulk polymer matrix, e.g. epoxy. This can provide exceptionally strong, stiff, and lightweight materials which are inherently anisotropic, as the fibres are usually arranged at a multitude of predetermined angles within discrete stacked 2D layers. The direction orthogonal to the 2D layers is usually without reinforcement to avoid compromising in-plane performance, which results in a vulnerability to damage in the polymer matrix caused by out-of-plane loading, i.e. impact. Their inability to plastically deform leaves only energy absorption via damage creation. This damage often manifests itself internally within the material as intra-ply matrix cracks and inter-ply delaminations, and can thus be difficult to detect visually. Since relatively minor damage can lead to a significant reduction in strength, stiffness and stability, there has been some reticence by designers for their use in safety critical applications, and the adoption of a `no growth' approach (i.e. damage propagation from a defect constitutes failure) is now the mindset of the composites industry. This has led to excessively heavy components, shackling of innovative design, and a need for frequent inspection during service (Richardson 1996; Abrate 1998).

  2. Fracture problems in composite materials

    NASA Technical Reports Server (NTRS)

    Erdogan, F.

    1972-01-01

    A series of fracture problems in composite materials are identified, their methods of solution are briefly discussed, and some sample results are presented. The main problem of interest is the determination of the stress state in the neighborhood of localized imperfections such as cracks and inclusions which may exist in the composite. Particular emphasis is placed on the evaluation of quantities such as the stress intensity factors, the power of the stress singularity, and the strain energy release rate, which may be used directly or indirectly in connection with an appropriate fracture criterion for the prediction of fracture initiation and propagation load levels. The topics discussed include a crack in layered composites, a crack terminating at and going through a bi-material interface, a penny-shaped crack in a filament-reinforced elastic matrix, and inclusion problems in bonded materials.

  3. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites.

    PubMed

    Wang, Z; Georgarakis, K; Nakayama, K S; Li, Y; Tsarkov, A A; Xie, G; Dudina, D; Louzguine-Luzgin, D V; Yavari, A R

    2016-01-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses. PMID:27067824

  4. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-04-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

  5. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    PubMed Central

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-01-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses. PMID:27067824

  6. NATURAL FIBER OR GLASS REINFORCED POLYPROPYLENE COMPOSITES?

    SciTech Connect

    Lorenzi, W.; Di Landro, L.; Casiraghi, A.; Pagano, M. R.

    2008-08-28

    Problems related to the recycle of conventional composite materials are becoming always more relevant for many industrial fields. Natural fiber composites (NFC) have recently gained much attention due to their low cost, environmental gains (eco-compatibility), easy disposal, reduction in volatile organic emissions, and their potential to compete with glass fiber composites (GFC). Interest in natural fibers is not only based over ecological aspects. NFC have good mechanical performances in relation to their low specific weight and low price. A characterization of mechanical properties, dynamic behavior, and moisture absorption is presented.

  7. Natural Fiber or Glass Reinforced Polypropylene Composites?

    NASA Astrophysics Data System (ADS)

    Lorenzi, W.; Di Landro, L.; Casiraghi, A.; Pagano, M. R.

    2008-08-01

    Problems related to the recycle of conventional composite materials are becoming always more relevant for many industrial fields. Natural fiber composites (NFC) have recently gained much attention due to their low cost, environmental gains (eco-compatibility), easy disposal, reduction in volatile organic emissions, and their potential to compete with glass fiber composites (GFC). Interest in natural fibers is not only based over ecological aspects. NFC have good mechanical performances in relation to their low specific weight and low price. A characterization of mechanical properties, dynamic behavior, and moisture absorption is presented.

  8. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, R. G.; Wiberley, S. E.

    1985-01-01

    Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

  9. Whisker-reinforced ceramic composites for heat engine components

    NASA Technical Reports Server (NTRS)

    Duffy, Stephen F.

    1988-01-01

    Much work was undertaken to develop techniques of incorporating SiC whiskers into either a Si3N4 or SiC matrix. The result was the fabrication of ceramic composites with ever-increasing fracture toughness and strength. To complement this research effort, the fracture behavior of whisker-reinforced ceramics is studied so as to develop methodologies for the analysis of structural components fabricated from this toughened material. The results, outlined herein, focus on the following areas: the use of micromechanics to predict thermoelastic properties, theoretical aspects of fracture behavior, and reliability analysis.

  10. Mechanical property characterization of polymeric composites reinforced by continuous microfibers

    NASA Astrophysics Data System (ADS)

    Zubayar, Ali

    Innumerable experimental works have been conducted to study the effect of polymerization on the potential properties of the composites. Experimental techniques are employed to understand the effects of various fibers, their volume fractions and matrix properties in polymer composites. However, these experiments require fabrication of various composites which are time consuming and cost prohibitive. Advances in computational micromechanics allow us to study the various polymer based composites by using finite element simulations. The mechanical properties of continuous fiber composite strands are directional. In traditional continuous fiber laminated composites, all fibers lie in the same plane. This provides very desirable increases in the in-plane mechanical properties, but little in the transverse mechanical properties. The effect of different fiber/matrix combinations with various orientations is also available. Overall mechanical properties of different micro continuous fiber reinforced composites with orthogonal geometry are still unavailable in the contemporary research field. In this research, the mechanical properties of advanced polymeric composite reinforced by continuous micro fiber will be characterized based on analytical investigation and FE computational modeling. Initially, we have chosen IM7/PEEK, Carbon Fiber/Nylon 6, and Carbon Fiber/Epoxy as three different case study materials for analysis. To obtain the equivalent properties of the micro-hetero structures, a concept of micro-scale representative volume elements (RVEs) is introduced. Five types of micro scale RVEs (3 square and 2 hexagonal) containing a continuous micro fiber in the polymer matrix were designed. Uniaxial tensile, lateral expansion and transverse shear tests on each RVE were designed and conducted by the finite element computer modeling software ANSYS. The formulae based on elasticity theory were derived for extracting the equivalent mechanical properties (Young's moduli, shear

  11. Fiber-Reinforced-Foam (FRF) Core Composite Sandwich Panel Concept for Advanced Composites Technologi

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Fiber-Reinforced-Foam (FRF) Core Composite Sandwich Panel Concept for Advanced Composites Technologies Project - Preliminary Manufacturing Demonstration Articles for Ares V Payload Shroud Barrel Acreage Structure

  12. Bioactive ceramic-reinforced composites for bone augmentation

    PubMed Central

    Tanner, K. E.

    2010-01-01

    Biomaterials have been used to repair the human body for millennia, but it is only since the 1970s that man-made composites have been used. Hydroxyapatite (HA)-reinforced polyethylene (PE) is the first of the ‘second-generation’ biomaterials that have been developed to be bioactive rather than bioinert. The mechanical properties have been characterized using quasi-static, fatigue, creep and fracture toughness testing, and these studies have allowed optimization of the production method. The in vitro and in vivo biological properties have been investigated with a range of filler content and have shown that the presence of sufficient bioactive filler leads to a bioactive composite. Finally, the material has been applied clinically, initially in the orbital floor and later in the middle ear. From this initial combination of HA in PE other bioactive ceramic polymer composites have been developed. PMID:20591846

  13. Nanographene reinforced carbon/carbon composites

    NASA Astrophysics Data System (ADS)

    Bansal, Dhruv

    Carbon/Carbon Composites (CCC) are made of carbon reinforcement in carbon matrix and have high thermal stability and fatigue resistance. CCC are used in nose cones, heat shields and disc brakes of aircrafts due to their exceptional mechanical properties at high temperature. The manufacturing process of CCC involves a carbonization stage in which unwanted elements, except carbon, are eliminated from the polymer precursor. Carbonization results in the formation of voids and cracks due to the thermal mismatch between the reinforcement and the matrix and expulsion of volatiles from the polymer matrix. Thermal cracks and voids decrease the density and mechanical properties of the manufactured CCC. In this work, Nanographene Platelets (NGP) were explored as nanofillers to fill the voids/cracks and reduce thermal shrinkage in CCC. They were first compared with Vapor Grown Carbon Nanofibers (VGCNF) by dispersion of different concentrations (0.5wt%, 1.5wt%, 3wt%) in resole-type phenolic resin and were characterized to explore their effect on rheology, heat of reaction and wetting behavior. The dispersions were then cured to form nanocomposites and were characterized for morphology, flexure and thermal properties. Finally, NGP were introduced into the carbon/carboncomposites in two stages, first by spraying in different concentrations (0.5wt%, 1.5wt%, 3wt%, 5wt %) during the prepreg formation and later during densification by directly mixing in the corresponding densification mix. The manufactured NGP reinforced CCC were characterized for microstructure, porosity, bulk density and mechanical properties (Flexure and ILSS) which were further cross-checked by non-destructive techniques (vibration and ultrasonic). In this study, it was further found that at low concentration (≤ 1.5 wt%) NGP were more effective in increasing the heat of reaction and in decreasing the viscosity of the phenolic resin. The decrease in viscosity led to better wetting properties of NGP / phenolic

  14. Flexural analysis of palm fiber reinforced hybrid polymer matrix composite

    NASA Astrophysics Data System (ADS)

    Venkatachalam, G.; Gautham Shankar, A.; Raghav, Dasarath; Santhosh Kiran, R.; Mahesh, Bhargav; Kumar, Krishna

    2015-07-01

    Uncertainty in availability of fossil fuels in the future and global warming increased the need for more environment friendly materials. In this work, an attempt is made to fabricate a hybrid polymer matrix composite. The blend is a mixture of General Purpose Resin and Cashew Nut Shell Liquid, a natural resin extracted from cashew plant. Palm fiber, which has high strength, is used as reinforcement material. The fiber is treated with alkali (NaOH) solution to increase its strength and adhesiveness. Parametric study of flexure strength is carried out by varying alkali concentration, duration of alkali treatment and fiber volume. Taguchi L9 Orthogonal array is followed in the design of experiments procedure for simplification. With the help of ANOVA technique, regression equations are obtained which gives the level of influence of each parameter on the flexure strength of the composite.

  15. Synthesis And Characterization Of Reduced Size Ferrite Reinforced Polymer Composites

    SciTech Connect

    Borah, Subasit; Bhattacharyya, Nidhi S.

    2008-04-24

    Small sized Co{sub 1-x}Ni{sub x}Fe{sub 2}O{sub 4} ferrite particles are synthesized by chemical route. The precursor materials are annealed at 400, 600 and 800 C. The crystallographic structure and phases of the samples are characterized by X-ray diffraction (XRD). The annealed ferrite samples crystallized into cubic spinel structure. Transmission Electron Microscopy (TEM) micrographs show that the average particle size of the samples are <20 nm. Particulate magneto-polymer composite materials are fabricated by reinforcing low density polyethylene (LDPE) matrix with the ferrite samples. The B-H loop study conducted at 10 kHz on the toroid shaped composite samples shows reduction in magnetic losses with decrease in size of the filler sample. Magnetic losses are detrimental for applications of ferrite at high powers. The reduction in magnetic loss shows a possible application of Co-Ni ferrites at high microwave power levels.

  16. Carbon fiber reinforced thermoplastic composites for future automotive applications

    NASA Astrophysics Data System (ADS)

    Friedrich, K.

    2016-05-01

    After a brief introduction to polymer composite properties and markets, the state of the art activities in the field of manufacturing of advanced composites for automotive applications are elucidated. These include (a) long fiber reinforced thermoplastics (LFT) for secondary automotive components, and (b) continuous carbon fiber reinforced thermosetting composites for car body applications. It is followed by future possibilities of carbon fiber reinforced thermoplastic composites for e.g. (i) crash elements, (ii) racing car seats, and (iii) production and recycling of automotive fenders.

  17. Finite element analysis of the stiffness of fabric reinforced composites

    NASA Technical Reports Server (NTRS)

    Foye, R. L.

    1992-01-01

    The objective of this work is the prediction of all three dimensional elastic moduli of textile fabric reinforced composites. The analysis is general enough for use with complex reinforcing geometries and capable of subsequent improvements. It places no restrictions on fabric microgeometry except that the unit cell be determinate and rectangular. The unit cell is divided into rectangular subcells in which the reinforcing geometries are easier to define and analyze. The analysis, based on inhomogeneous finite elements, is applied to a variety of weave, braid, and knit reinforced composites. Some of these predictions are correlated to test data.

  18. Damage assessment and residual compression strength of thick composite plates with through-the-thickness reinforcements

    NASA Technical Reports Server (NTRS)

    Smith, Barry T.; Farley, Gary L.; Maiden, Janice; Coogan, Dreux; Moore, Judith G.

    1991-01-01

    Damage in composite materials was studied with through-the-thickness reinforcements. As a first step it was necessary to develop new ultrasonic imaging technology to better assess internal damage of the composite. A useful ultrasonic imaging technique was successfully developed to assess the internal damage of composite panels. The ultrasonic technique accurately determines the size of the internal damage. It was found that the ultrasonic imaging technique was better able to assess the damage in composite panel with through-the-thickness reinforcements than by destructively sectioning the specimen and visual inspection under a microscope. Five composite compression-after-impact panels were tested. The compression-after-impact strength of the panels with the through-the-thickness reinforcements was almost twice that of the comparable panel without through-the-thickness reinforcement.

  19. Damage assessment and residual compression strength of thick composite plates with through-the-thickness reinforcements

    NASA Technical Reports Server (NTRS)

    Smith, Barry T.

    1990-01-01

    Damage in composite materials was studied with through-the-thickness reinforcements. As a first step it was necessary to develop new ultrasonic imaging technology to better assess internal damage of the composite. A useful ultrasonic imaging technique was successfully developed to assess the internal damage of composite panels. The ultrasonic technique accurately determines the size of the internal damage. It was found that the ultrasonic imaging technique was better able to assess the damage in a composite panel with through-the-thickness reinforcements than by destructively sectioning the specimen and visual inspection under a microscope. Five composite compression-after-impact panels were tested. The compression-after-impact strength of the panels with the through-the-thickness reinforcements was almost twice that of the comparable panel without through-the-thickness reinforcement.

  20. Resin Characterization in Cured Composite Materials

    NASA Technical Reports Server (NTRS)

    Young, P. R.; Chang, A.

    1985-01-01

    Molecular-level characterization of polymeric matrix resin in cured graphite-reinforced composite materials now determined through analysis of diffuse reflectance (DR) with Fourier Transform Infrared (FTIR) spectroscopy. Improved analytical method based on diffuse reflectance. DR/ FTIR technique successfully applied to analysis of several different composites and adhesives impossible to analyze by conventional methods.

  1. Method of preparing fiber reinforced ceramic material

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T. (Inventor)

    1987-01-01

    Alternate layers of mats of specially coated SiC fibers and silicon monotapes are hot pressed in two stages to form a fiber reinforced ceramic material. In the first stage a die is heated to about 600 C in a vacuum furnace and maintained at this temperature for about one-half hour to remove fugitive binder. In the second stage the die temperature is raised to about 1000 C and the layers are pressed at between 35 and 138 MPa. The resulting preform is placed in a reactor tube where a nitriding gas is flowed past the preform at 1100 to 1400 C to nitride the same.

  2. Experimental study on mixed mode fracture in unidirectional fiber reinforced composites

    NASA Astrophysics Data System (ADS)

    Gong, Kezhuang; Li, Zheng; Fu, Bin

    2008-11-01

    Fiber reinforced composites are applied broadly in aeronautic and astronautic fields as a structural material. But the investigation in dynamic fracture behavior of fiber reinforced composite stands in the breach for scientists due to a large number of aircraft disasters. In this paper, the mixed mode fracture problems in fiber reinforced composites under impact are studied. First, based on the theory of the reflective dynamic caustic method for mixed mode fracture, corresponding experiments are carried out to study the dynamic fracture behaviors of unidirectional fiber reinforced composites under two kinds load conditions. By recording and analyzing the shadow spot patterns during the crack propagation process carefully, the dynamic fracture toughness and crack growth velocity of fiber reinforced composites are obtained. Via the observation of the crack growth routes and fracture sections, we further reveal the fracture mechanism of unidirectional fiber reinforced composites. It concludes that opening mode still is the easier fracture type for the pre-crack initiation in fiber reinforced composites, while the interface between fibers and matrix becomes the fatal vulnerability during the crack propagation.

  3. Numerical exploration into the potential of tungsten reinforced CuCrZr matrix composites

    NASA Astrophysics Data System (ADS)

    Hohe, Jörg; Fliegener, Sascha; Findeisen, Claudio; Reiser, Jens; Widak, Verena; Rieth, Michael

    2016-03-01

    The present study provides a numerical investigation into the potential of tungsten reinforced CuCrZr materials in order to overcome their limited performance at higher temperatures. Metal matrix composites including (i) particle reinforced microstructures, (ii) short fiber reinforced microstructures with both randomly orientated and (iii) aligned fibers as well as (iv) laminates consisting of stacked tungsten and CuCrZr layers are considered. The numerical analysis is performed by means of an energy based homogenization procedure in conjunction with a finite element analysis of representative volume elements for the respective microstructures. The results of the screening analysis reveal a distinct improvement of the mechanical properties of CuCrZr materials by the tungsten reinforcements even for moderate tungsten volume fractions. In a comparison of the different microstructures, the ordered microstructures, i.e. laminates and the aligned short fiber reinforced composites in most cases outperform their disordered counterparts.

  4. Synthesis and Characterization of TiB2 Reinforced Aluminium Matrix Composites: A Review

    NASA Astrophysics Data System (ADS)

    Kumar, Narendra; Gautam, Gaurav; Gautam, Rakesh Kumar; Mohan, Anita; Mohan, Sunil

    2015-09-01

    Aluminium-matrix composites (AMCs) are developed to meet the demands of light weight high performance materials in aerospace, automotive, marine and other applications. The properties of AMCs can be tailored suitably by combinations of matrix, reinforcement and processing route. AMCs are one of the most attractive alternatives for the manufacturing of light weight and high strength parts due to their low density and high specific strength. There are various techniques for preparing the AMCs with different reinforcement particles. In AMCs, the reinforcements are usually in the form of metal oxides, carbides, borides, nitrides and their combination. Among the various reinforcements titanium di-boride (TiB2) is of much interest due to its excellent stiffness, hardness, and wear resistance. This paper attempts to provide an overview to explore the possibilities of synthesizing titanium di-boride reinforced AMCs with different techniques. The mechanical and tribological properties of these composites have been emphasized to project these as tribo-materials.

  5. Evaluation of several micromechanics models for discontinuously reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. Steven; Birt, M. J.

    1990-01-01

    A systematic experimental evaluation of whisker and particulate reinforced aluminum matrix composites was conducted to assess the variation in tensile properties with reinforcement type, volume fraction, and specimen thickness. Each material was evaluated in three thicknesses, 1.8, 3.18, and 6.35 mm, to determine the size, distribution, and orientation of the reinforcements. This information was used to evaluate several micromechanical models that predict composite moduli. The longitudinal and transverse moduli were predicted for reinforced aluminum. The Paul model, the Cox model and the Halpin-Tsai model were evaluated. The Paul model gave a good upper bound prediction for the particulate reinforced composites but under predicted whisker reinforced composite moduli. The Cox model gave good moduli predictions for the whisker reinforcement, but was too low for the particulate. The Halpin-Tsai model gave good results for both whisker and particulate reinforced composites. An approach using a trigonometric projection of whisker length to predict the fiber contribution to the modulus in the longitudinal and transverse directions was compared to the more conventional lamination theory approach.

  6. Processing and Characterization of Basalt Fiber Reinforced Ceramic Composites for High Temperature Applications Using Polymer Precursors

    NASA Technical Reports Server (NTRS)

    Cox, Sarah B.; Lui, Donovan; Gou, Jihua

    2014-01-01

    The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, which allows a shape to be formed prior to the cure, and is then pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The two PDCs used in this development are polysiloxane and polycarbosilane. Basalt fibers are used for the reinforcement in the composite system. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in composites. Continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material.

  7. Comparison of mechanical properties of a new fiber reinforced composite and bulk filling composites

    PubMed Central

    Pradelle, Nelly; Villat, Cyril; Attik, Nina; Colon, Pierre; Grosgogeat, Brigitte

    2015-01-01

    Objectives The aim of this study was to evaluate the mechanical and physical properties of a newly developed fiber reinforced dental composite. Materials and Methods Fiber reinforced composite EverX Posterior (EXP, GC EUROPE), and other commercially available bulk fill composites, including Filtek Bulk Fill (FB, 3M ESPE), SonicFill (SF, Kerr Corp.), SureFil (SDR, Dentsply), Venus Bulk Fill (VB, HerausKultzer), Tetric evoceram bulk fill (TECB, Ivoclar Vivadent), and Xtra Base (XB, Voco) were characterized. Composite samples light-cured with a LED device were evaluated in terms of flexural strength, flexural modulus (ISO 4049, n = 6), fracture toughness (n = 6), and Vickers hardness (0, 2, and 4 mm in depth at 24 hr, n = 5). The EXP samples and the fracture surface were observed under a scanning electron microscopy. Data were statistically analyzed using one-way ANOVA and unpaired t-test. Results EXP, FB, and VB had significantly higher fracture toughness value compared to all the other bulk composite types. SF, EXP, and XB were not statistically different, and had significantly higher flexural strength values compared to other tested composite materials. EXP had the highest flexural modulus, VB had the lowest values. Vickers hardness values revealed SF, EXP, TECB, and XB were not statistically different, and had significantly higher values compared to other tested composite materials. SEM observations show well dispersed fibers working as a reinforcing phase. Conclusions The addition of fibers to methacrylate-based matrix results in composites with either comparable or superior mechanical properties compared to the other bulk fill materials tested. PMID:26587411

  8. CODIFICATION OF FIBER REINFORCED COMPOSITE PIPING

    SciTech Connect

    Rawls, G.

    2012-10-10

    The goal of the overall project is to successfully adapt spoolable FRP currently used in the oil industry for use in hydrogen pipelines. The use of FRP materials for hydrogen service will rely on the demonstrated compatibility of these materials for pipeline service environments and operating conditions. The ability of the polymer piping to withstand degradation while in service, and development of the tools and data required for life management are imperative for successful implementation of these materials for hydrogen pipeline. The information and data provided in this report provides the technical basis for the codification for fiber reinforced piping (FRP) for hydrogen service. The DOE has invested in the evaluation of FRP for the delivery for gaseous hydrogen to support the development of a hydrogen infrastructure. The codification plan calls for detailed investigation of the following areas: System design and applicable codes and standards; Service degradation of FRP; Flaw tolerance and flaw detection; Integrity management plan; Leak detection and operational controls evaluation; Repair evaluation. The FRP codification process started with commercially available products that had extensive use in the oil and gas industry. These products have been evaluated to assure that sufficient structural integrity is available for a gaseous hydrogen environment.

  9. Reinforced Pericardium as a Hybrid Material for Cardiovascular Applications

    PubMed Central

    Bracaglia, Laura G.; Yu, Li; Hibino, Narutoshi

    2014-01-01

    Pericardium-based cardiovascular devices are currently bound by a 10-year maximum lifetime due to detrimental calcification and degradation. The goal of this work is to develop a novel synthetic material to create a lasting replacement for malfunctioning or diseased tissue in the cardiovascular system. This study couples poly(propylene fumarate) (PPF) and a natural biomaterial together in an unprecedented hybrid composite and evaluates the composite versus the standard glutaraldehyde-treated tissue. The polymer reinforcement is hypothesized to provide initial physical protection from proteolytic enzymes and degradation, but leave the original collagen and elastin matrix unaltered. The calcification rate and durability of the hybrid material are evaluated in vitro and in an in vivo subdermal animal model. Results demonstrate that PPF is an effective support and leads to significantly less calcium deposition, important metrics when evaluating cardiovascular material. By avoiding chemical crosslinking of the tissue and associated side effects, PPF-reinforced pericardium as a biohybrid material offers a promising potential direction for further development in cardiovascular material alternatives. Eliminating the basis for the majority of cardiovascular prosthetic failures could revolutionize expectations for extent of cardiovascular repair. PMID:25236439

  10. High elastic modulus nanopowder reinforced resin composites for dental applications

    NASA Astrophysics Data System (ADS)

    Wang, Yijun

    2007-12-01

    Dental restorations account for more than $3 billion dollars a year on the market. Among them, all-ceramic dental crowns draw more and more attention and their popularity has risen because of their superior aesthetics and biocompatibility. However, their relatively high failure rate and labor-intensive fabrication procedure still limit their application. In this thesis, a new family of high elastic modulus nanopowder reinforced resin composites and their mechanical properties are studied. Materials with higher elastic modulus, such as alumina and diamond, are used to replace the routine filler material, silica, in dental resin composites to achieve the desired properties. This class of composites is developed to serve (1) as a high stiffness support to all-ceramic crowns and (2) as a means of joining independently fabricated crown core and veneer layers. Most of the work focuses on nano-sized Al2O3 (average particle size 47 nm) reinforcement in a polymeric matrix with 50:50 Bisphenol A glycidyl methacrylate (Bis-GMA): triethylene glycol dimethacrylate (TEGDMA) monomers. Surfactants, silanizing agents and primers are examined to obtain higher filler levels and enhance the bonding between filler and matrix. Silane agents work best. The elastic modulus of a 57.5 vol% alumina/resin composite is 31.5 GPa compared to current commercial resin composites with elastic modulus <15 GPa. Chemical additives can also effectively raise the hardness to as much as 1.34 GPa. Besides>alumina, diamond/resin composites are studied. An elastic modulus of about 45 GPa is obtained for a 57 vol% diamond/resin composite. Our results indicate that with a generally monodispersed nano-sized high modulus filler, relatively high elastic modulus resin-based composite cements are possible. Time-dependent behavior of our resin composites is also investigated. This is valuable for understanding the behavior of our material and possible fatigue testing in the future. Our results indicate that with