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Sample records for advanced fiber reinforced

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

    SciTech Connect

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

    2015-10-28

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  3. 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

  4. Fuselage structure using advanced technology fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Robinson, R. K.; Tomlinson, H. M. (Inventor)

    1982-01-01

    A fuselage structure is described in which the skin is comprised of layers of a matrix fiber reinforced composite, with the stringers reinforced with the same composite material. The high strength to weight ratio of the composite, particularly at elevated temperatures, and its high modulus of elasticity, makes it desirable for use in airplane structures.

  5. Nondestructive Evaluation of Advanced Fiber Reinforced Polymer Matrix Composites: A Technology Assessment

    NASA Technical Reports Server (NTRS)

    Yolken, H. Thomas; Matzkanin, George A.

    2009-01-01

    Because of their increasing utilization in structural applications, the nondestructive evaluation (NDE) of advanced fiber reinforced polymer composites continues to receive considerable research and development attention. Due to the heterogeneous nature of composites, the form of defects is often very different from a metal and fracture mechanisms are more complex. The purpose of this report is to provide an overview and technology assessment of the current state-of-the-art with respect to NDE of advanced fiber reinforced polymer composites.

  6. Multiscale carbon nanotube-carbon fiber reinforcement for advanced epoxy composites.

    PubMed

    Bekyarova, E; Thostenson, E T; Yu, A; Kim, H; Gao, J; Tang, J; Hahn, H T; Chou, T-W; Itkis, M E; Haddon, R C

    2007-03-27

    We report an approach to the development of advanced structural composites based on engineered multiscale carbon nanotube-carbon fiber reinforcement. Electrophoresis was utilized for the selective deposition of multi- and single-walled carbon nanotubes (CNTs) on woven carbon fabric. The CNT-coated carbon fabric panels were subsequently infiltrated with epoxy resin using vacuum-assisted resin transfer molding (VARTM) to fabricate multiscale hybrid composites in which the nanotubes were completely integrated into the fiber bundles and reinforced the matrix-rich regions. The carbon nanotube/carbon fabric/epoxy composites showed approximately 30% enhancement of the interlaminar shear strength as compared to that of carbon fiber/epoxy composites without carbon nanotubes and demonstrate significantly improved out-of-plane electrical conductivity. PMID:17326671

  7. Ceramic fiber reinforced filter

    DOEpatents

    Stinton, David P.; McLaughlin, Jerry C.; Lowden, Richard A.

    1991-01-01

    A filter for removing particulate matter from high temperature flowing fluids, and in particular gases, that is reinforced with ceramic fibers. The filter has a ceramic base fiber material in the form of a fabric, felt, paper of the like, with the refractory fibers thereof coated with a thin layer of a protective and bonding refractory applied by chemical vapor deposition techniques. This coating causes each fiber to be physically joined to adjoining fibers so as to prevent movement of the fibers during use and to increase the strength and toughness of the composite filter. Further, the coating can be selected to minimize any reactions between the constituents of the fluids and the fibers. A description is given of the formation of a composite filter using a felt preform of commercial silicon carbide fibers together with the coating of these fibers with pure silicon carbide. Filter efficiency approaching 100% has been demonstrated with these filters. The fiber base material is alternately made from aluminosilicate fibers, zirconia fibers and alumina fibers. Coating with Al.sub.2 O.sub.3 is also described. Advanced configurations for the composite filter are suggested.

  8. Rehabilitation of advanced periodontal problems by using a combination of a glass fiber-reinforced composite resin bridge and splint.

    PubMed

    Kumbuloglu, Ovul; Aksoy, Gokhan; User, Atilla

    2008-02-01

    Rehabilitation of masticatory ability in patients with reduced periodontal tissue support is a multiple challenge in dentistry. It has been shown that tooth mobility is reduced by a splint in place. Splints may be constructed of various materials. Development of fiber-reinforced composite materials offers a new and conservative approach for tooth replacement and stabilization. This case report describes the rehabilitation and 2-year follow-up of a patient with advanced periodontal problems by using a glass fiber-reinforced composite resin material. PMID:18389738

  9. Basic failure mechanisms in advanced composites. [composed of epoxy resins reinforced with carbon fibers

    NASA Technical Reports Server (NTRS)

    Mazzio, V. F.; Mehan, R. L.; Mullin, J. V.

    1973-01-01

    The fundamental failure mechanisms which result from the interaction of thermal cycling and mechanical loading of carbon-epoxy composites were studied. This work was confined to epoxy resin uniderictionally reinforced with HTS carbon fibers, and consists of first identifying local fiber, matrix and interface failure mechanisms using the model composite specimen containing a small number of fibers so that optical techniques can be used for characterization. After the local fracture process has been established for both mechanical loading and thermal cycling, engineering composite properties and gross fracture modes are then examined to determine how the local events contribute to real composite performance. Flexural strength in high fiber content specimens shows an increase in strength with increased thermal cycling. Similar behavior is noted for 25 v/o material up to 200 cycles; however, there is a drastic reduction after 200 cycles indicating a major loss of integrity probably through the accumulation of local cleavage cracks in the tensile region.

  10. Advanced in situ multi-scale characterization of hardness of carbon-fiber-reinforced plastic

    NASA Astrophysics Data System (ADS)

    Wang, Hongxin; Masuda, Hideki; Kitazawa, Hideaki; Onishi, Keiko; Kawai, Masamichi; Fujita, Daisuke

    2016-10-01

    In situ multi-scale characterization of hardness of carbon-fiber-reinforced plastic (CFRP) is demonstrated by a traditional hardness tester, instrumented indentation tester and atomic-force-microscope (AFM)-based nanoindentation. In particular, due to the large residual indentation and nonuniform distribution of the microscale carbon fibers, the Vickers hardness could not be calculated by the traditional hardness tester. In addition, the clear residual microindentation could not be formed on the CFRP by instrumented indentation tester because of the large tip half angle of the Berkovich indenter. Therefore, an efficient technique for characterizing the true nanoscale hardness of CFRP was proposed and evaluated. The local hardness of the carbon fibers or plastic matrix on the nanoscale did not vary with nanoindentation location. The Vickers hardnesses of the carbon fiber and plastic matrix determined by AFM-based nanoindentation were 340 ± 30 and 40 ± 2 kgf/mm2, respectively.

  11. Synthesis of high performance ceramic fibers by chemical vapor deposition for advanced metallics reinforcing

    NASA Technical Reports Server (NTRS)

    Revankar, Vithal; Hlavacek, Vladimir

    1991-01-01

    The chemical vapor deposition (CVD) synthesis of fibers capable of effectively reinforcing intermetallic matrices at elevated temperatures which can be used for potential applications in high temperature composite materials is described. This process was used due to its advantage over other fiber synthesis processes. It is extremely important to produce these fibers with good reproducible and controlled growth rates. However, the complex interplay of mass and energy transfer, blended with the fluid dynamics makes this a formidable task. The design and development of CVD reactor assembly and system to synthesize TiB2, CrB, B4C, and TiC fibers was performed. Residual thermal analysis for estimating stresses arising form thermal expansion mismatch were determined. Various techniques to improve the mechanical properties were also performed. Various techniques for improving the fiber properties were elaborated. The crystal structure and its orientation for TiB2 fiber is discussed. An overall view of the CVD process to develop CrB2, TiB2, and other high performance ceramic fibers is presented.

  12. 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.

  13. Fiber reinforced superalloys

    NASA Technical Reports Server (NTRS)

    Petrasek, Donald W.; Signorelli, Robert A.; Caulfield, Thomas; Tien, John K.

    1987-01-01

    Improved performance of heat engines is largely dependent upon maximum cycle temperatures. Tungsten fiber reinforced superalloys (TFRS) are the first of a family of high temperature composites that offer the potential for significantly raising hot component operating temperatures and thus leading to improved heat engine performance. This status review of TFRS research emphasizes the promising property data developed to date, the status of TFRS composite airfoil fabrication technology, and the areas requiring more attention to assure their applicability to hot section components of aircraft gas turbine engines.

  14. Recent advances in electron-beam curing of carbon fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Coqueret, Xavier; Krzeminski, Mickael; Ponsaud, Philippe; Defoort, Brigitte

    2009-07-01

    Cross-linking polymerization initiated by high-energy radiation is a very attractive technique for the fabrication of high-performance composite materials. The method offers many advantages compared to conventional energy- and time-consuming thermal curing processes. Free radical and cationic poly-addition chemistries have been investigated in some details by various research groups along the previous years. A high degree of control over curing kinetics and material properties can be exerted by adjusting the composition of matrix precursors as well as by acting on process parameters. However, the comparison with state-of-the-art thermally cured composites revealed the lower transverse mechanical properties of radiation-cured composites and the higher brittleness of the radiation-cured matrix. Improving fiber-matrix adhesion and upgrading polymer network toughness are thus two major challenges in this area. We have investigated several points related to these issues, and particularly the reduction of the matrix shrinkage on curing, the wettability of carbon fibers, the design of fiber-matrix interface and the use of thermoplastic toughening agents. Significant improvements were achieved on transverse strain at break by applying original surface treatments on the fibers so as to induce covalent coupling with the matrix. A drastic enhancement of the K IC value exceeding 2 MPa m 1/2 was also obtained for acrylate-based matrices toughened with high T g thermoplastics.

  15. 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.

  16. 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.

  17. Fiber reinforced hybrid phenolic foam

    NASA Astrophysics Data System (ADS)

    Desai, Amit

    Hybrid composites in recent times have been developed by using more than one type of fiber reinforcement to bestow synergistic properties of the chosen filler and matrix and also facilitating the design of materials with specific properties matched to end use. However, the studies for hybrid foams have been very limited because of problems related to fiber dispersion in matrix, non uniform mixing due to presence of more than one filler and partially cured foams. An effective approach to synthesize hybrid phenolic foam has been proposed and investigated here. Hybrid composite phenolic foams were reinforced with chopped glass and aramid fibers in varied proportions. On assessing mechanical properties in compression and shear several interesting facts surfaced but overall hybrid phenolic foams exhibited a more graceful failure, greater resistance to cracking and were significantly stiffer and stronger than foams with only glass and aramid fibers. The optimum fiber ratio for the reinforced hybrid phenolic foam system was found to be 1:1 ratio of glass to aramid fibers. Also, the properties of hybrid foam were found to deviate from rule of mixture (ROM) and thus the existing theories of fiber reinforcement fell short in explaining their complex behavior. In an attempt to describe and predict mechanical behavior of hybrid foams a statistical design tool using analysis of variance technique was employed. The utilization of a statistical model for predicting foam properties was found to be an appropriate tool that affords a global perspective of the influence of process variables such as fiber weight fraction, fiber length etc. on foam properties (elastic modulus and strength). Similar approach could be extended to study other fiber composite foam systems such as polyurethane, epoxy etc. and doing so will reduce the number of experimental iterations needed to optimize foam properties and identify critical process variables. Diffusivity, accelerated aging and flammability

  18. High-Temperature Creep Behavior Of Fiber-Reinforced Niobium

    NASA Technical Reports Server (NTRS)

    Petrasek, Donald W.; Titran, Robert H.

    1990-01-01

    Study conducted to determine feasibility of using composite materials in advanced space power systems, described in 22-page report. Tungsten fibers reduce creep and mass in advanced power systems. Reinforcing niobium alloys with tungsten fibers increases their resistances to creep by factors of as much as 10.

  19. Fiber-Reinforced Superalloys For Rocket Engines

    NASA Technical Reports Server (NTRS)

    Lewis, Jack R.; Yuen, Jim L.; Petrasek, Donald W.; Stephens, Joseph R.

    1990-01-01

    Report discusses experimental studies of fiber-reinforced superalloy (FRS) composite materials for use in turbine blades in rocket engines. Intended to withstand extreme conditions of high temperature, thermal shock, atmospheres containing hydrogen, high cycle fatigue loading, and thermal fatigue, which tax capabilities of even most-advanced current blade material - directionally-solidified, hafnium-modified MAR M-246 {MAR M-246 (Hf) (DS)}. FRS composites attractive combination of properties for use in turbopump blades of advanced rocket engines at temperatures from 870 to 1,100 degrees C.

  20. 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.

  1. Toughness of fiber reinforced shotcrete

    SciTech Connect

    Morgan, D.R.; Chen, L.; Beaupre, D.

    1995-12-31

    Fibers are added to shotcrete to improve energy absorption and impact resistance, to provide crack resistance and crack control, and to provide apparent ductility, i.e., an ability to continue to carry load after the shotcrete matrix has cracked. In order to be able to quantify the benefits of fiber addition, a variety of different toughness measuring systems have been developed in different countries. Most commonly used are flexural toughness systems which determine load vs. deflection responses and relate the area under the curve to some absolute or dimensionless index energy parameter. In North America the ASTM C1018 test method is most commonly used. In Japan the JSCE-SF4 test procedure is used. A variety of procedures have been used in Europe, but the template approach of the Norwegian Guidelines NBP No. 7, seems to be finding favor. This paper briefly assesses the relative advantages and disadvantages of the various methods of characterizing toughness. It then provides recommendations for a new procedure which uses the ASTM C1018 test method for generating the flexural load vs. deflection curve, but analyzes the data using a modified version of the Norwegian template approach. The load vs. deflection curve is directly compared against four residual strength curves and the fiber reinforced shotcrete assigned one of four toughness performance levels. It is believed that this new procedure should provide suitable within and between laboratory reproducibility and be more suitable for purposes of differentiating between different fiber types and addition rates and specifying toughness for fiber reinforced shotcrete products than any of the existing methods.

  2. 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

  3. Advanced Engineering Fibers.

    ERIC Educational Resources Information Center

    Edie, Dan D.; Dunham, Michael G.

    1987-01-01

    Describes Clemson University's Advanced Engineered Fibers Laboratory, which was established to provide national leadership and expertise in developing the processing equipment and advance fibers necessary for the chemical, fiber, and textile industries to enter the composite materials market. Discusses some of the laboratory's activities in…

  4. Graphite fiber reinforced thermoplastic resins

    NASA Technical Reports Server (NTRS)

    Novak, R. C.

    1975-01-01

    Mechanical properties of neat resin samples and graphite fiber reinforced samples of thermoplastic resins were characterized with particular emphasis directed to the effects of environmental exposure (humidity, temperature and ultraviolet radiation). Tensile, flexural, interlaminar shear, creep and impact strengths were measured for polysulfone, polyarylsulfone and a state-of-the-art epoxy resin samples. In general, the thermoplastic resins exhibited environmental degradation resistance equal to or superior to the reference epoxy resin. Demonstration of the utility and quality of a graphite/thermoplastic resin system was accomplished by successfully thermoforming a simulated compressor blade and a fan exit guide vane.

  5. [Fiber-reinforced adhesive partial dentures].

    PubMed

    Kreulen, C M

    2003-06-01

    Dental applications of fiber-reinforced polymers include adhesive partial dentures. Dental resin composite materials can be reinforced by several types of fibres. Fiber orientation, proper wetting of the fibers by the resin and fiber volume are important. An application of fiber reinforced composites is the composite inlay bridge. This paper deals with some aspects of this type of adhesive partial denture. Advantages include the satisfactory esthetics and the minimally invasive character. Not clear yet is the long-term survival. The adhesive properties of fiber-reinforced adhesive partial dentures require an adaptation of the current dental philosophy, in which direct and indirect restorative techniques can be combined. An increase in knowledge and experience is needed to determine the dental applications. PMID:12852063

  6. Study on basalt fiber parameters affecting fiber-reinforced mortar

    NASA Astrophysics Data System (ADS)

    Orlov, A. A.; Chernykh, T. N.; Sashina, A. V.; Bogusevich, D. V.

    2015-01-01

    This article considers the effect of different dosages and diameters of basalt fibers on tensile strength increase during bending of fiberboard-reinforced mortar samples. The optimal dosages of fiber, providing maximum strength in bending are revealed. The durability of basalt fiber in an environment of cement, by means of microscopic analysis of samples of fibers and fiberboard-reinforced mortar long-term tests is examined. The article also compares the behavior of basalt fiber in the cement stone environment to a glass one and reveals that the basalt fiber is not subject to destruction.

  7. 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.

  8. 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.

  9. 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.

  10. Nonwoven glass fiber mat reinforces polyurethane adhesive

    NASA Technical Reports Server (NTRS)

    Roseland, L. M.

    1967-01-01

    Nonwoven glass fiber mat reinforces the adhesive properties of a polyurethane adhesive that fastens hardware to exterior surfaces of aluminum tanks. The mat is embedded in the uncured adhesive. It ensures good control of the bond line and increases the peel strength.

  11. 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.

  12. Fiber reinforced superalloys for rocket engines

    NASA Technical Reports Server (NTRS)

    Petrasek, Donald W.; Stephens, Joseph R.

    1988-01-01

    High-pressure turbopumps for advanced reusable liquid-propellant rocket engines such as that for the Space Shuttle Main Engine (SSME) require turbine blade materials that operate under extreme conditions of temperature, hydrogen environment, high-cycle fatigue loading, thermal fatigue and thermal shock. Such requirements tax the capabilities of current blade materials. Based on projections of properties for tungsten fiber reinforced superalloy (FRS) composites, it was concluded that FRS turbine blades offer the potential of a several-fold increase in life and over a 200C increase in temperature capability over current SSME blade material. FRS composites were evaluated with respect to mechanical property requirements for SSME blade applications. Compared to the current blade material, the thermal shock resistance of FRS materials is excellent, two to nine times better, and their thermal fatigue resistance is equal to or higher than the current blade material. FRS materials had excellent low and high-cycle fatigue strengths, and thermal shock-induced surface microcracks had no influence on their fatigue strength. The material also exhibited negligible embrittlement when exposed to a hydrogen environment.

  13. Fiber reinforced superalloys for rocket engines

    NASA Technical Reports Server (NTRS)

    Petrasek, Donald W.; Stephens, Joseph R.

    1989-01-01

    High pressure turbopumps for advanced reusable liquid propellant rocket engines such as that for the Space Shuttle Main Engine (SSME) require turbine blade materials that operate under extreme conditions of temperature, hydrogen environment, high-cycle fatigue loading, thermal fatigue and thermal shock. Such requirements tax the capabilities of current blade materials. Based on projections of properties for tungsten fiber reinforced superalloy (FRS) composites, it was concluded that FRS turbine blades offer the potential of a several fold increase in life and over a 200 C increase in temperature capability over the current SSME blade material. FRS composites were evaluated with respect to mechanical property requirements for SSME blade applications. Compared to the current blade material, the thermal shock resistance of FRS materials is excellent, two to nine times better, and their thermal fatigue resistance is equal to or higher than the current blade material. FRS materials had excellent low and high-cycle fatigue strengths, and thermal shock-induced surface microcracks had no influence on their fatigue strength. The material also exhibited negligible embrittlement when exposed to a hydrogen environment.

  14. Discontinuous Fiber-reinforced Composites above Critical Length

    PubMed Central

    Petersen, R.C.

    2014-01-01

    Micromechanical physics of critical fiber length, describing a minimum filament distance for resin impregnation and stress transfer, has not yet been applied in dental science. As a test of the hypothesis that 9-micron-diameter, 3-mm-long quartz fibers would increase mechanical strength over particulate-filled composites, photocure-resin-pre-impregnated discontinuous reinforcement was incorporated at 35 wt% into 3M Corporation Z100, Kerr Corporation HerculiteXRV, and an experimental photocure paste with increased radiopaque particulate. Fully articulated four-point bend testing per ASTM C 1161-94 for advanced ceramics and Izod impact testing according to a modified unnotched ASTM D 256-00 specification were then performed. All photocure-fiber-reinforced composites demonstrated significant improvements over particulate-filled compounds (p < 0.001) for flexural strength, modulus, work of fracture, strain at maximum load, and Izod toughness, with one exception for the moduli of Z100 and the experimental reinforced paste. The results indicate that inclusion of pre-impregnated fibers above the critical aspect ratio yields major advancements regarding the mechanical properties tested. PMID:15790745

  15. Reinforcement of timber beams with carbon fibers reinforced plastics

    NASA Astrophysics Data System (ADS)

    Gugutsidze, G.; Draškovič, F.

    2010-06-01

    Wood is a polymeric material with many valuable features and which also lacks some negative features. In order to keep up with high construction rates and the minimization of negative effects, wood has become one of the most valuable materials in modern engineering. But the use of timber material economically is also an actual problem in order to protect the environment and improve natural surroundings. A panel of scientists is interested in solving these problems and in creating rational structures, where timber can be used efficiently. These constructions are as follows: glue-laminated (gluelam), composed and reinforced wooden constructions. Composed and reinforced wooden constructions are examined less, but according to researches already carried out, it is clear that significant work can be accomplished in creating rational, highly effective and economic timber constructions. The paper deals with research on the formation of composed fiber-reinforced beams (CFRP) made of timber and provide evidence of their effectiveness. The aim of the paper is to investigate cross-bending of CFRP-reinforced gluelaminated timber beams. According to the results we were able to determine the additional effectiveness of reinforcement with CFRP (which depends on the CFRP material's quality, quantity and module of elasticity) on the mechanical features of timber and a whole beam.

  16. FIBER LENGTH DISTRIBUTION MEASUREMENT FOR LONG GLASS AND CARBON FIBER REINFORCED INJECTION MOLDED THERMOPLASTICS

    SciTech Connect

    Kunc, Vlastimil; Frame, Barbara J; Nguyen, Ba N.; TuckerIII, Charles L.; Velez-Garcia, Gregorio

    2007-01-01

    Procedures for fiber length distribution (FLD) measurement of long fiber reinforced injection molded thermoplastics were refined for glass and carbon fibers. Techniques for sample selection, fiber separation, digitization and length measurement for both fiber types are described in detail. Quantitative FLD results are provided for glass and carbon reinforced polypropylene samples molded with a nominal original fiber length of 12.7 mm (1/2 in.) using equipment optimized for molding short fiber reinforced thermoplastics.

  17. Fabrication Routes for Continuous Fiber-Reinforced Ceramic Composites (CFCC)

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A.; Bansal, Narottam P.

    1998-01-01

    The primary approaches used for fabrication of continuous fiber-reinforced ceramic composite (CFCC) components have been reviewed. The CFCC fabrication issues related to fiber, interface, and matrix have been analyzed. The capabilities. advantages and limitations of the five matrix-infiltration routes have been compared and discussed. Today. the best fabrication route for the CFCC end-user is not clear and compromises need to be made depending on the details of the CFCC application. However, with time, this problem should be reduced as research continues to develop advanced CFCC constituents and fabrication routes.

  18. Fabrication Routes for Continuous Fiber-Reinforced Ceramic Composites (CFCC)

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A.; Bansal, Narottam P.

    1998-01-01

    The primary approaches used for fabrication of continuous fiber-reinforced ceramic composite (CFCC) components have been reviewed. The CFCC fabrication issues related to fiber, interface, and matrix have been analyzed. The capabilities, advantages and limitations of the five matrix-infiltration routes have been compared and discussed. Today, the best fabrication route for the CFCC end-user is not clear and compromises need to be made depending on the details of the CFCC application. However, with time, this problem should be reduced as research continues to develop advanced CFCC constituents and fabrication routes.

  19. Fiber breakage phenomena in long fiber reinforced plastic preparation

    NASA Astrophysics Data System (ADS)

    Huang, Chao-Tsai; Tseng, Huan-Chang; Vlcek, Jiri; Chang, Rong-Yeu

    2015-07-01

    Due to the high demand of smart green, the lightweight technologies have become the driving force for the development of automotives and other industries in recent years. Among those technologies, using short and long fiber-reinforced plastics (FRP) to replace some metal components can reduce the weight of an automotive significantly. However, the microstructures of fibers inside plastic matrix are too complicated to manage and control during the injection molding through the screw, the runner, the gate, and then into the cavity. This study focuses on the fiber breakage phenomena during the screw plastification. Results show that fiber breakage is strongly dependent on screw design and operation. When the screw geometry changes, the fiber breakage could be larger even with lower compression ratio.

  20. Graphite fiber reinforced thermoplastic resins

    NASA Technical Reports Server (NTRS)

    Navak, R. C.

    1977-01-01

    The results of a program designed to optimize the fabrication procedures for graphite thermoplastic composites are described. The properties of the composites as a function of temperature were measured and graphite thermoplastic fan exit guide vanes were fabricated and tested. Three thermoplastics were included in the investigation: polysulfone, polyethersulfone, and polyarylsulfone. Type HMS graphite was used as the reinforcement. Bending fatigue tests of HMS graphite/polyethersulfone demonstrated a gradual shear failure mode which resulted in a loss of stiffness in the specimens. Preliminary curves were generated to show the loss in stiffness as a function of stress and number of cycles. Fan exit guide vanes of HMS graphite polyethersulfone were satisfactorily fabricated in the final phase of the program. These were found to have stiffness and better fatigue behavior than graphite epoxy vanes which were formerly bill of material.

  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. [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

  3. [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.

  4. 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.

  5. 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.

  6. [Fusion implants of carbon fiber reinforced plastic].

    PubMed

    Früh, H J; Liebetrau, A; Bertagnoli, R

    2002-05-01

    Carbon fiber reinforced plastics (CFRP) are used in the medical field when high mechanical strength, innovative design, and radiolucency (see spinal fusion implants) are needed. During the manufacturing process of the material CFRP carbon fibers are embedded into a resin matrix. This resin material could be thermoset (e.g., epoxy resin EPN/DDS) or thermoplastic (e.g., PEAK). CFRP is biocompatible, radiolucent, and has higher mechanical capabilities compared to other implant materials. This publication demonstrates the manufacturing process of fusion implants made of a thermoset matrix system using a fiber winding process. The material has been used clinically since 1994 for fusion implants of the cervical and lumbar spine. The results of the fusion systems CORNERSTONE-SR C (cervical) and UNION (lumbar) showed no implant-related complications. New implant systems made of this CFRP material are under investigation and are presented.

  7. Experimental Behavior of Carbon Fiber Reinforced Isolators

    SciTech Connect

    Russo, Gaetano; Pauletta, Margherita; Cortesia, Andrea; Dal Bianco, Alberto

    2008-07-08

    This paper describes an investigation on the experimental behavior of innovative elastomeric isolators reinforced by carbon fiber fabrics. These fabrics are very much lighter than steel plates used in conventional isolators and able to transfer to the adjacent elastomer layers tangential stresses adequate to oppose the transversal deformation of rubber under vertical loads. The isolators are not bonded to the sub- and super-structure (elimination of the steel end-plates), hence their weight and cost are reduced. The experimental investigation is carried out on small-scale isolator prototypes reinforced by quadridirectional carbon fiber fabrics. The isolators are subjected to the following qualification tests prescribed by the Italian Code 'Ordinanza 3274' for steel reinforced isolators: 1) 'Static assessment of the compression stiffness'; 2) 'Static assessment of the shear modulus G'; 3) 'Dynamic assessment of the dynamic shear modulus G{sub din} and of the damping coefficient {xi}; 4) 'Assessment of the G{sub din}-{gamma} and {xi}-{gamma} diagrams by means of dynamic tests'; 5) 'Assessment of creep characteristics'; 6) 'Evaluation of the capacity of sustaining at least 10 cycles'. As a result of the tests, the isolators survived large shear strains, comparable to those expected for conventional isolators.

  8. Cohesive fracture model for functionally graded fiber reinforced concrete

    SciTech Connect

    Park, Kyoungsoo; Paulino, Glaucio H.; Roesler, Jeffery

    2010-06-15

    A simple, effective, and practical constitutive model for cohesive fracture of fiber reinforced concrete is proposed by differentiating the aggregate bridging zone and the fiber bridging zone. The aggregate bridging zone is related to the total fracture energy of plain concrete, while the fiber bridging zone is associated with the difference between the total fracture energy of fiber reinforced concrete and the total fracture energy of plain concrete. The cohesive fracture model is defined by experimental fracture parameters, which are obtained through three-point bending and split tensile tests. As expected, the model describes fracture behavior of plain concrete beams. In addition, it predicts the fracture behavior of either fiber reinforced concrete beams or a combination of plain and fiber reinforced concrete functionally layered in a single beam specimen. The validated model is also applied to investigate continuously, functionally graded fiber reinforced concrete composites.

  9. Tungsten fiber reinforced superalloys: A status review

    NASA Technical Reports Server (NTRS)

    Petrasek, D. W.; Signorelli, R. A.

    1981-01-01

    Improved performance of heat engines is largely dependent upon maximum cycle temperatures. Tungsten fiber reinforced superalloys (TFRS) are the first of a family of high temperature composites that offer the potential for significantly raising hot component operating temperatures and thus leading to improved heat engine performance. This status review of TFRS research emphasizes the promising property data developed to date, the status of TFRS composite airfoil fabrication technology, and the areas requiring more attention to assure their applicability to hot section components of aircraft gas turbine engines.

  10. Radiation effects on carbon fiber reinforced thermoplastics

    SciTech Connect

    Sasuga, Tsuneo; Udagawa, Akira; Seguchi, Tadao

    1993-12-31

    Polyether-ether-ketone (PEEK) and a newly developed thermoplastic polyimide ``new-TPI`` were applied to carbon fiber reinforced plastic (CFRP) as a matrix resin. PEEK and new-TPI showed excellent resistance over 50 MGy to electron irradiation and the crosslinking proceeded predominantly by irradiation. The changes in mechanical properties induced by electron irradiation of the CFRP with the two resins were examined at various temperatures. The flexural strength and modulus measured at {minus}196 and 25{degree}C were scarcely affected up to 120 MGy and both the values measured at high temperature were increased with dose.

  11. Mechanical properties of woven glass fiber-reinforced composites.

    PubMed

    Kanie, Takahito; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

    2006-06-01

    The aim of this investigation was to measure the flexural and compressive strengths and the corresponding moduli of cylindrical composite specimens reinforced with woven glass fiber. Test specimens were made by light-curing urethane dimethacrylate oligomer with woven glass fiber of 0.18-mm standard thickness. Tests were conducted using four reinforcement methods and two specimen diameters. Flexural strength and modulus of woven glass fiber-reinforced specimens were significantly greater than those without woven glass fiber (p < 0.01). Likewise, compressive strength of reinforced specimens was significantly greater than those without woven glass fiber (p < 0.01), except for specimens reinforced with woven glass fiber oriented at a tilt direction in the texture (p > 0.05). In terms of comparison between the two specimen diameters, no statistically significant differences in flexural strength and compressive strength (p > 0.05) were observed.

  12. Optical Fiber Sensors for Advanced Civil Structures

    NASA Astrophysics Data System (ADS)

    de Vries, Marten Johannes Cornelius

    1995-01-01

    The objective of this dissertation is to develop, analyze, and implement optical fiber-based sensors for the nondestructive quantitative evaluation of advanced civil structures. Based on a comparative evaluation of optical fiber sensors that may be used to obtain quantitative information related to physical perturbations in the civil structure, the extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor is selected as the most attractive sensor. The operation of the EFPI sensor is explained using the Kirchhoff diffraction approach. As is shown in this dissertation, this approach better predicts the signal-to-noise ratio as a function of gap length than methods employed previously. The performance of the optical fiber sensor is demonstrated in three different implementations. In the first implementation, performed with researchers in the Civil Engineering Department at the University of Southern California in Los Angeles, optical fiber sensors were used to obtain quantitative strain information from reinforced concrete interior and exterior column-to-beam connections. The second implementation, performed in cooperation with researchers at the United States Bureau of Mines in Spokane, Washington, used optical fiber sensors to monitor the performance of roof bolts used in mines. The last implementation, performed in cooperation with researchers at the Turner-Fairbanks Federal Highway Administration Research Center in McLean, Virginia, used optical fiber sensors, attached to composite prestressing strands used for reinforcing concrete, to obtain absolute strain information. Multiplexing techniques including time, frequency and wavelength division multiplexing are briefly discussed, whereas the principles of operation of spread spectrum and optical time domain reflectometery (OTDR) are discussed in greater detail. Results demonstrating that spread spectrum and OTDR techniques can be used to multiplex optical fiber sensors are presented. Finally, practical

  13. Nano-Aramid Fiber Reinforced Polyurethane Foam

    NASA Technical Reports Server (NTRS)

    Semmes, Edmund B.; Frances, Arnold

    2008-01-01

    Closed cell polyurethane and, particularly, polyisocyanurate foams are a large family of flexible and rigid products the result of a reactive two part process wherein a urethane based polyol is combined with a foaming or "blowing" agent to create a cellular solid at room temperature. The ratio of reactive components, the constituency of the base materials, temperature, humidity, molding, pouring, spraying and many other processing techniques vary greatly. However, there is no known process for incorporating reinforcing fibers small enough to be integrally dispersed within the cell walls resulting in superior final products. The key differentiating aspect from the current state of art resides in the many processing technologies to be fully developed from the novel concept of milled nano pulp aramid fibers and their enabling entanglement capability fully enclosed within the cell walls of these closed cell urethane foams. The authors present the results of research and development of reinforced foam processing, equipment development, strength characteristics and the evolution of its many applications.

  14. Process of Making Boron-Fiber Reinforced Composite Tape

    NASA Technical Reports Server (NTRS)

    Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor); Johnston, Norman J. (Inventor); Marchello, Joseph M. (Inventor)

    2002-01-01

    The invention is an apparatus and method for producing a hybrid boron reinforced polymer matrix composition from powder pre-impregnated fiber tow bundles and a linear array of boron fibers. The boron fibers are applied onto the powder pre-impregnated fiber tow bundles and then are processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the powder pre-impregnated fiber tow bundles with the boron fibers become a hybrid boron reinforced polymer matrix composite tape. A driving mechanism pulls the powder pre-impregnated fiber tow bundles with boron fibers through the processing line of the apparatus and a take-up spool collects the formed hybrid boron-fiber reinforced polymer matrix composite tape.

  15. Intracanal reinforcement fiber in pediatric dentistry: a case report.

    PubMed

    Rocha, Rachel de Oliveira; das Neves, Lucimara Teixeira; Marotti, Noely Regina; Wanderley, Marcia Turolla; Corrêa, Maria Salete Nahás Pires

    2004-04-01

    A technique for the restoration of carious primary maxillary incisors using indirect resin composite crowns and intracanal reinforcement fiber is described. Endodontic treatment was previously performed on each tooth. The advantages of using an intracanal reinforcement fiber include resin composite crown reinforcement, translucency, and relative manipulation facility. In addition, the use of indirect resin composite crowns provides good shape and esthetics, as well as reduced chair time for the child. The technique is illustrated in a case report in which indirect resin composite crowns and an intracanal reinforcement fiber are placed in a 3-year-old girl.

  16. Advances in root reinforcement experiments

    NASA Astrophysics Data System (ADS)

    Giadrossich, Filippo; Schwarz, Massimiliano; Niedda, Marcello

    2013-04-01

    Root reinforcement is considered in many situations an important effect of vegetation for slope stability. In the past 20 years many studies analyzed root reinforcement in laboratory and field experiments, as well as through modeling frameworks. Nearby the important contribution of roots to shear strength, roots are recognized to impart stabilization also through lateral (parallel to slope) redistribution of forces under tension. Lateral root reinforcement under tensile solicitations (such as in the upper part of a shallow landslide) was documented and discussed by some studies. The most common method adopted to measure lateral root reinforcement are pullout tests where roots (single or as bundle) are pulled out from a soil matrix. These conditions are indeed representative for the case where roots within the mass of a landslide slip out from the upper stable part of the slope (such in a tension crack). However, there is also the situation where roots anchored at the upper stable part of the slope slip out from the sliding soil mass. In this last case it is difficult to quantify root reinforcement and no study discussed this mechanism so far. The main objective of this study is to quantify the contribution of roots considering the two presented cases of lateral root reinforcement discussed above - roots slipping out from stable soil profile or sliding soil matrix from anchored roots-, and discuss the implication of the results for slope stability modeling. We carried out a series of laboratory experiments for both roots pullout and soil sliding mechanisms using a tilting box with a bundle of 15 roots. Both Douglas (Pseudotsuga menziesii) roots and soil were collected from the study area in Sardinia (Italy), and reconstructed in laboratory, filling the root and soil layer by layer up to 0.4 meter thickness. The results show that the ratio between pullout force and force transferred to the root during soil sliding range from 0.5 to 1. This results indicate that

  17. Fire test method for graphite fiber reinforced plastics

    NASA Technical Reports Server (NTRS)

    Bowles, K. J.

    1980-01-01

    A potential problem in the use of graphite fiber reinforced resin matrix composites is the dispersal of graphite fibers during accidental fires. Airborne, electrically conductive fibers originating from the burning composites could enter and cause shorting in electrical equipment located in surrounding areas. A test method for assessing the burning characteristics of graphite fiber reinforced composites and the effectiveness of the composites in retaining the graphite fibers has been developed. The method utilizes a modified Ohio State University Rate of Heat Release apparatus. The equipment and the testing procedure are described. The application of the test method to the assessment of composite materials is illustrated for two resin matrix/graphite composite systems.

  18. Fire test method for graphite fiber reinforced plastics

    NASA Technical Reports Server (NTRS)

    Bowles, K. J.

    1980-01-01

    A potential problem in the use of graphite fiber reinforced resin matrix composites is the dispersal of graphite fibers during accidential fires. Airborne, electrically conductive fibers originating from the burning composites could enter and cause shorting in electrical equipment located in surrounding areas. A test method for assessing the burning characteristics of graphite fiber reinforced composites and the effectiveness of the composites in retaining the graphite fibers has been developed. The method utilizes a modified rate of heat release apparatus. The equipment and the testing procedure are described. The application of the test method to the assessment of composite materials is illustrated for two resin matrix/graphite composite systems.

  19. CREATION OF MUSIC WITH FIBER REINFORCED CONCRETE

    NASA Astrophysics Data System (ADS)

    Kato, Hayato; Takeuchi, Masaki; Ogura, Naoyuki; Kitahara, Yukiko; Okamoto, Takahisa

    This research focuses on the Fiber Reinforcement Concrete(FRC) and its performance on musical tones. Thepossibility of future musical instruments made of this concrete is discussed. Recently, the technical properties of FRC had been improved and the different production styles, such as unit weight of binding material and volume of fiber in the structure, hardly affects the results of the acoustics. However, the board thickness in the FRC instruments is directly related with the variety of musical tone. The FRC musical effects were compared with those produced with wood on wind instruments. The sounds were compared with those produced with woodwind instruments. The sound pressure level was affected by the material and it becomes remarkably notorious in the high frequency levels. These differences had great influence on the spectrum analysis of the tone in the wind instruments and the sensory test. The results from the sensory test show dominant performances of brightness, beauty and power in the FRC instruments compared with those made of wood.

  20. Robotic inspection of fiber reinforced composites using phased array UT

    NASA Astrophysics Data System (ADS)

    Stetson, Jeffrey T.; De Odorico, Walter

    2014-02-01

    Ultrasound is the current NDE method of choice to inspect large fiber reinforced airframe structures. Over the last 15 years Cartesian based scanning machines using conventional ultrasound techniques have been employed by all airframe OEMs and their top tier suppliers to perform these inspections. Technical advances in both computing power and commercially available, multi-axis robots now facilitate a new generation of scanning machines. These machines use multiple end effector tools taking full advantage of phased array ultrasound technologies yielding substantial improvements in inspection quality and productivity. This paper outlines the general architecture for these new robotic scanning systems as well as details the variety of ultrasonic techniques available for use with them including advances such as wide area phased array scanning and sound field adaptation for non-flat, non-parallel surfaces.

  1. Mechanical recycling of continuous fiber-reinforced thermoplastic sheets

    NASA Astrophysics Data System (ADS)

    Moritzer, Elmar; Heiderich, Gilmar

    2016-03-01

    This contribution examines possible material recycling of offcuts generated during the production of continuous-fiber-reinforced composite sheets. These sheets consist of a polyamide 6 matrix and glass fiber fabric. In the initial step, the offcut is shredded to obtain particles; following that, the particles are processed in a twin-screw process to produce fiber-reinforced plastic pellets with varying fiber contents. These pellets are intended for use in injection molding processes as a substitution for new raw materials. This investigation centers on the mechanical properties which can be achieved with the recycled material after both the twin-screw process and injection molding.

  2. Bond characteristics of steel fiber and deformed reinforcing steel bar embedded in steel fiber reinforced self-compacting concrete (SFRSCC)

    NASA Astrophysics Data System (ADS)

    Aslani, Farhad; Nejadi, Shami

    2012-09-01

    Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of the self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, ductility, toughness, energy absorption capacity, fracture toughness and cracking. Although the available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates the bond characteristics between steel fiber and SCC firstly. Based on the available experimental results, the current analytical steel fiber pullout model (Dubey 1999) is modified by considering the different SCC properties and different fiber types (smooth, hooked) and inclination. In order to take into account the effect of fiber inclination in the pullout model, apparent shear strengths ( τ ( app)) and slip coefficient ( β) are incorporated to express the variation of pullout peak load and the augmentation of peak slip as the inclined angle increases. These variables are expressed as functions of the inclined angle ( ϕ). Furthurmore, steel-concrete composite floors, reinforced concrete floors supported by columns or walls and floors on an elastic foundations belong to the category of structural elements in which the conventional steel reinforcement can be partially replaced by the use of steel fibers. When discussing deformation capacity of structural elements or civil engineering structures manufactured using SFRSCC, one must be able to describe thoroughly both the behavior of the concrete matrix reinforced with steel fibers and the interaction between this composite matrix and discrete steel reinforcement of the conventional type. However, even though the knowledge on bond behavior is essential for evaluating the overall behavior of structural components containing reinforcement and steel fibers

  3. Bond characteristics of steel fiber and deformed reinforcing steel bar embedded in steel fiber reinforced self-compacting concrete (SFRSCC)

    NASA Astrophysics Data System (ADS)

    Aslani, Farhad; Nejadi, Shami

    2012-09-01

    Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of the self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, ductility, toughness, energy absorption capacity, fracture toughness and cracking. Although the available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates the bond characteristics between steel fiber and SCC firstly. Based on the available experimental results, the current analytical steel fiber pullout model (Dubey 1999) is modified by considering the different SCC properties and different fiber types (smooth, hooked) and inclination. In order to take into account the effect of fiber inclination in the pullout model, apparent shear strengths (τ (app)) and slip coefficient (β) are incorporated to express the variation of pullout peak load and the augmentation of peak slip as the inclined angle increases. These variables are expressed as functions of the inclined angle (ϕ). Furthurmore, steel-concrete composite floors, reinforced concrete floors supported by columns or walls and floors on an elastic foundations belong to the category of structural elements in which the conventional steel reinforcement can be partially replaced by the use of steel fibers. When discussing deformation capacity of structural elements or civil engineering structures manufactured using SFRSCC, one must be able to describe thoroughly both the behavior of the concrete matrix reinforced with steel fibers and the interaction between this composite matrix and discrete steel reinforcement of the conventional type. However, even though the knowledge on bond behavior is essential for evaluating the overall behavior of structural components containing reinforcement and steel fibers

  4. 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.

  5. Structural Behavior of Concrete Beams Reinforced with Basalt Fiber Reinforced Polymer (BFRP) Bars

    NASA Astrophysics Data System (ADS)

    Ovitigala, Thilan

    The main challenge for civil engineers is to provide sustainable, environmentally friendly and financially feasible structures to the society. Finding new materials such as fiber reinforced polymer (FRP) material that can fulfill the above requirements is a must. FRP material was expensive and it was limited to niche markets such as space shuttles and air industry in the 1960s. Over the time, it became cheaper and spread to other industries such as sporting goods in the 1980-1990, and then towards the infrastructure industry. Design and construction guidelines are available for carbon fiber reinforced polymer (CFRP), aramid fiber reinforced polymer (AFRP) and glass fiber reinforced polymer (GFRP) and they are currently used in structural applications. Since FRP is linear elastic brittle material, design guidelines for the steel reinforcement are not valid for FRP materials. Corrosion of steel reinforcement affects the durability of the concrete structures. FRP reinforcement is identified as an alternative to steel reinforcement in corrosive environments. Although basalt fiber reinforced polymer (BFRP) has many advantages over other FRP materials, but limited studies have been done. These studies didn't include larger BFRP bar diameters that are mostly used in practice. Therefore, larger beam sizes with larger BFRP reinforcement bar diameters are needed to investigate the flexural and shear behavior of BFRP reinforced concrete beams. Also, shear behavior of BFRP reinforced concrete beams was not yet studied. Experimental testing of mechanical properties and bond strength of BFRP bars and flexural and shear behavior of BFRP reinforced concrete beams are needed to include BFRP reinforcement bars in the design codes. This study mainly focuses on the use of BFRP bars as internal reinforcement. The test results of the mechanical properties of BFRP reinforcement bars, the bond strength of BFRP reinforcement bars, and the flexural and shear behavior of concrete beams

  6. Interface Characterization in Fiber-Reinforced Polymer-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Naya, F.; Molina-Aldareguía, J. M.; Lopes, C. S.; González, C.; LLorca, J.

    2016-10-01

    A novel methodology is presented and applied to measure the shear interface strength of fiber-reinforced polymers. The strategy is based in fiber push-in tests carried out on the central fiber of highly-packed fiber clusters with hexagonal symmetry, and it is supported by a detailed finite element analysis of the push-in test to account for the influence of hygrothermal residual stresses, fiber constraint and fiber anisotropy on the interface strength. Examples of application are presented to determine the shear interface strength in carbon and glass fiber composites reinforced with either thermoset or thermoplastic matrices. In addition, the influence of the environment (either dry or wet conditions) on the interface strength in C/epoxy composites is demonstrated.

  7. Stronger Carbon Fibers for Reinforced Plastics

    NASA Technical Reports Server (NTRS)

    Cagliostro, D. E.; Lerner, N. R.

    1983-01-01

    Process makes fibers 70 percent stronger at lower carbonization temperature. Stronger carbon fibers result from benzoic acid pretreatment and addition of acetylene to nitrogen carbonizing atmosphere. New process also makes carbon fibers of higher electrical resistance -- an important safety consideration.

  8. 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

  9. Characterization and design of steel fiber reinforced shotcrete in tunnelling

    SciTech Connect

    Casanova, P.A.; Rossi, P.C.

    1995-12-31

    A design procedure of steel fiber reinforced shotcrete tunnel linings is proposed. It is based on the analysis of a cracked section. The tensile behavior of shotcrete after cracking is obtained by a uniaxial tension test on cored notched samples. As for usual reinforced concrete structures an interaction diagram (moment-axial load) is determined.

  10. Objective Surface Evaluation of Fiber Reinforced Polymer Composites

    NASA Astrophysics Data System (ADS)

    Palmer, Stuart; Hall, Wayne

    2013-08-01

    The mechanical properties of advanced composites are essential for their structural performance, but the surface finish on exterior composite panels is of critical importance for customer satisfaction. This paper describes the application of wavelet texture analysis (WTA) to the task of automatically classifying the surface finish properties of two fiber reinforced polymer (FRP) composite construction types (clear resin and gel-coat) into three quality grades. Samples were imaged and wavelet multi-scale decomposition was used to create a visual texture representation of the sample, capturing image features at different scales and orientations. Principal components analysis was used to reduce the dimensionality of the texture feature vector, permitting successful classification of the samples using only the first principal component. This work extends and further validates the feasibility of this approach as the basis for automated non-contact classification of composite surface finish using image analysis.

  11. Carbon nanotube reinforced polyacrylonitrile and poly(etherketone) fibers

    NASA Astrophysics Data System (ADS)

    Jain, Rahul

    The graphitic nature, continuous structure, and high mechanical properties of carbon nanotubes (CNTs) make them good candidate for reinforcing polymer fiber. The different types of CNTs including single-wall carbon nanotubes (SWNTs), few-wall carbon nanotubes (FWNTs), and multi-wall carbon nanotubes (MWNTs), and carbon nanofibers (CNFs) differ in terms of their diameter and number of graphitic walls. The desire has been to increase the concentration of CNTs as much as possible to make next generation multi-functional materials. The work in this thesis is mainly focused on MWNT and CNF reinforced polyacrylonitrile (PAN) composite fibers, and SWNT, FWNT, and MWNT reinforced poly(etherketone) (PEK) composite fibers. To the best of our knowledge, this is the first study to report the spinning of 20% MWNT or 30% CNF reinforced polymer fiber spun using conventional fiber spinning. Also, this is the first study to report the PEK/CNT composite fibers. The fibers were characterized for their thermal, tensile, mechanical, and dynamic mechanical properties. The fiber structure and morphology was studied using WAXD and SEM. The effect of two-stage heat drawing, sonication time for CNF dispersion, fiber drying temperature, and molecular weight of PAN was also studied. Other challenges associated with processing high concentrations of solutions for making composite fibers have been identified and reported. The effect of CNT diameter and concentration on fiber spinnability and electrical conductivity of composite fiber have also been studied. This work suggests that CNT diameter controls the maximum possible concentration of CNTs in a composite fiber. The results show that by properly choosing the type of CNT, length of CNTs, dispersion of CNTs, fiber spinning method, fiber draw ratio, and type of polymer, one can get electrically conducting fibers with wide range of conductivities for different applications. The PEK based control and composite fibers possess high thermal

  12. Studies on natural fiber reinforced polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Patel, R. H.; Kapatel, P. M.; Machchhar, A. D.; Kapatel, Y. A.

    2016-05-01

    Natural fiber reinforced composites show increasing importance in day to days applications because of their low cost, lightweight, easy availability, non-toxicity, biodegradability and environment friendly nature. But these fibers are hydrophilic in nature. Thus they have very low reactivity and poor compatibility with polymers. To overcome these limitations chemical modifications of the fibers have been carried out. Therefore, in the present work jute fibers have chemically modified by treating with sodium hydroxide (NaOH) solutions. These treated jute fibers have been used to fabricate jute fiber reinforced epoxy composites. Mechanical properties like tensile strength, flexural strength and impact strength have been found out. Alkali treated composites show better properties compare to untreated composites.

  13. Moisture effects on the high-temperature strength of fiber-reinforced resin composites.

    NASA Technical Reports Server (NTRS)

    Hertz, J.

    1972-01-01

    Under NAS 8-27435, the Convair Aerospace Division of General Dynamics and their subcontractor, Hercules Incorporated, have conducted studies on the effects of moisture on the properties of fiber-reinforced resin composites and on the epoxy resins presently used in advanced composites. Data are presented on the resins and composites subjected to varying time/temperature/humidity or time/temperature/water-boil exposures. The effects of moisture on matrix, reinforcement, and fiber/resin interface are discussed and supported by experimental test data.

  14. Polymer concrete reinforced with recycled-tire fibers: Mechanical properties

    NASA Astrophysics Data System (ADS)

    Martínez-Cruz, E.; Martínez-Barrera, G.; Martínez-López, M.

    2013-06-01

    Polymer Concrete was reinforced with recycled-tire fibers in order to improve the compressive and flexural strength. Polymer concrete specimens were prepared with 70% of silicious sand, 30% of polyester resin and various fiber concentrations (0.3, 0.6, 0.9 and 1.2 vol%). The results show increment of 50% in average of the compressive and flexural strength as well as on the deformation when adding 1.2 vol% of recycled-fibers.

  15. Fretting maps of glass fiber-reinforced composites

    SciTech Connect

    Turki, C.; Salvia, M.; Vincent, L.

    1993-12-31

    Industrial development of new materials are often limited due to an insufficient knowledge in their functional properties. The paper deals with fretting behavior of glass fiber reinforced epoxy/metal contacts. Fretting is a plague for all industries, especially in the case of quasi-static loadings. Furthermore friction testing under small displacements appeared well fitted to understand the effect of fiber orientations and to relate results to microstructure (fiber, matrix and interface).

  16. Preliminary evaluation of fiber composite reinforcement of truck frame rails

    NASA Technical Reports Server (NTRS)

    Faddoul, J. R.

    1977-01-01

    The use of graphite fiber/resin matrix composite to effectively reinforce a standard steel truck frame rail is studied. A preliminary design was made and it was determined that the reinforcement weight could be reduced by a factor of 10 when compared to a steel reinforcement. A section of a 1/3 scale reinforced rail was fabricated to demonstrate low cost manufacturing techniques. The scale rail section was then tested and increased stiffness was confirmed. No evidence of composite fatigue was found after 500,000 cycles to a fiber stress of 34,000 psi. The test specimen failed in bending in a static test at a load 50 percent greater than that predicted for a non-reinforced rail.

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

    PubMed

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

    2003-01-01

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

  18. Nano-Fiber Reinforced Enhancements in Composite Polymer Matrices

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    2009-01-01

    Nano-fibers are used to reinforce polymer matrices to enhance the matrix dependent properties that are subsequently used in conventional structural composites. A quasi isotropic configuration is used in arranging like nano-fibers through the thickness to ascertain equiaxial enhanced matrix behavior. The nano-fiber volume ratios are used to obtain the enhanced matrix strength properties for 0.01,0.03, and 0.05 nano-fiber volume rates. These enhanced nano-fiber matrices are used with conventional fiber volume ratios of 0.3 and 0.5 to obtain the composite properties. Results show that nano-fiber enhanced matrices of higher than 0.3 nano-fiber volume ratio are degrading the composite properties.

  19. Fatigue strength of woven kenaf fiber reinforced composites

    NASA Astrophysics Data System (ADS)

    Ismail, A. E.; Aziz, M. A. Che Abdul

    2015-12-01

    Nowadays, green composites provide alternative to synthetic fibers for non-bearing and load-bearing applications. According to literature review, lack of information is available on the fatigue performances especially when the woven fiber is used instead of randomly oriented fibers. In order to overcome this problem, this paper investigates the fatigue strength of different fiber orientations and number of layers of woven kenaf fiber reinforced composites. Four types of fiber orientations are used namely 0°, 15°, 30° and 45°. Additionally, two numbers of layers are also considered. It is revealed that the fatigue life has no strong relationship with the fiber orientations. For identical fiber orientations, the fatigue life can be predicted considerably using the normalized stress. However as expected, the fatigue life enhancement occur when the number of layer is increased.

  20. Damping properties of fiber reinforced composite suitable for stayed cable

    NASA Astrophysics Data System (ADS)

    Li, Jianzhi; Sun, Baochen; Du, Yanliang

    2011-11-01

    Carbon fiber reinforced plastics (CFRP) cables were initially most investigated to replace steel cables. To further explore the advantages of FRP cables, the potential ability of vibration control is studied in this paper emphasizing the designable characteristic of hybrid FRP cables. Fiber reinforced vinyl ester composites and fiber reinforced epoxy composites were prepared by the pultrusion method. Due to the extensive application of fiber reinforced composites, the temperature spectrum and frequency spectrum of loss factor for the composite were tested using dynamic mechanical analysis (DMA) equipment. The damping properties and damping mechanism of the composite were investigated and discussed at different temperatures and frequencies. The result indicates that the loss factor of the composites is increasing with the increase of the frequency from 0.1Hz to 2 Hz and decreasing with the decrease of the temperature from -20°C to 60°C. The loss factor of the carbon fiber composite is higher than that of the glass fiber for the same matrix. The loss factor of the vinyl ester composite is higher than that of the epoxy composite for the same fiber.

  1. Damping properties of fiber reinforced composite suitable for stayed cable

    NASA Astrophysics Data System (ADS)

    Li, Jianzhi; Sun, Baochen; Du, Yanliang

    2012-04-01

    Carbon fiber reinforced plastics (CFRP) cables were initially most investigated to replace steel cables. To further explore the advantages of FRP cables, the potential ability of vibration control is studied in this paper emphasizing the designable characteristic of hybrid FRP cables. Fiber reinforced vinyl ester composites and fiber reinforced epoxy composites were prepared by the pultrusion method. Due to the extensive application of fiber reinforced composites, the temperature spectrum and frequency spectrum of loss factor for the composite were tested using dynamic mechanical analysis (DMA) equipment. The damping properties and damping mechanism of the composite were investigated and discussed at different temperatures and frequencies. The result indicates that the loss factor of the composites is increasing with the increase of the frequency from 0.1Hz to 2 Hz and decreasing with the decrease of the temperature from -20°C to 60°C. The loss factor of the carbon fiber composite is higher than that of the glass fiber for the same matrix. The loss factor of the vinyl ester composite is higher than that of the epoxy composite for the same fiber.

  2. 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.

  3. Shear transfer in concrete reinforced with carbon fibers

    NASA Astrophysics Data System (ADS)

    El-Mokadem, Khaled Mounir

    2001-10-01

    Scope and method of study. The research started with preliminary tests and studies on the behavior and effect of carbon fibers in different water solutions and mortar/concrete mixes. The research work investigated the use of CF in the production of concrete pipes and prestressed concrete double-tee sections. The research then focused on studying the effect of using carbon fibers on the direct shear transfer of sand-lightweight reinforced concrete push-off specimens. Findings and conclusions. In general, adding carbon fibers to concrete improved its tensile characteristics but decreased its compressive strength. The decrease in compressive strength was due to the decrease in concrete density as fibers act as three-dimensional mesh that entrapped air. The decrease in compressive strength was also due to the increase in the total surface area of non-cementitious material in the concrete. Sand-lightweight reinforced concrete push-off specimens with carbon fibers had lower shear carrying capacity than those without carbon fibers for the same cement content in the concrete. Current building codes and specifications estimate the shear strength of concrete as a ratio of the compressive strength. If applying the same principals then the ratio of shear strength to compressive strength for concrete reinforced with carbon fibers is higher than that for concrete without carbon fibers.

  4. Creep behavior for advanced polycrystalline SiC fibers

    SciTech Connect

    Youngblood, G.E.; Jones, R.H.; Kohyama, Akira

    1997-04-01

    A bend stress relaxation (BSR) test has been utilized to examine irradiation enhanced creep in polycrystalline SiC fibers which are under development for use as fiber reinforcement in SiC/SiC composite. Qualitative, S-shaped 1hr BSR curves were compared for three selected advanced SiC fiber types and standard Nicalon CG fiber. The temperature corresponding to the middle of the S-curve (where the BSR parameter m = 0.5) is a measure of a fiber`s thermal stability as well as it creep resistance. In order of decreasing thermal creep resistance, the measured transition temperatures were Nicalon S (1450{degrees}C), Sylramic (1420{degrees}C), Hi-Nicalon (1230{degrees}C) and Nicalon CG (1110{degrees}C).

  5. 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.

  6. Formable woven preforms based on in situ reinforced thermoplastic fibers

    SciTech Connect

    Robertson, C.G.; Souza, J.P. de; Baird, D.G.

    1995-12-01

    Blends of Vectra B950 (VB) and polypropylene (PP) were spun into fibers utilizing a dual extrusion process for use in formable fabric prepregs. Fibers of 50/50 weight composition were processed up to fiber draw ratios of 106. The tensile modulus of these fibers showed positive deviation from the rule of mixtures for draw ratios greater than 40, and the tensile modulus and strength properties did not level off within the range of draw ratios investigated. The fibers, pre-wetted with polypropylene, were woven into fabrics that were subsequently impregnated with polypropylene sheet to form composites. The tensile mechanical properties of these composites were nearly equivalent to those of long glass fiber reinforced polypropylene. At temperatures between 240 and 280{degrees}C, composites of 6.3 wt.% VB proved formable with elongation to break values in excess of 20%. Impregnated fabric composites were successfully thermoformed without noticeable fiber damage, and a combined fabric impregnation / thermoforming process was developed.

  7. Renewable agricultural fibers as reinforcing fillers in plastics: Mechanical properties of kenaf fiber-polypropylene composites

    SciTech Connect

    Sanadi, A.R.; Caulfield, D.F.; Jacobson, R.E.; Rowell, R.M. |

    1995-05-01

    Kenaf (Hibiscus cannabinus) is a fast growing annual growth plant that is harvested for its bast fibers. These fibers have excellent specific properties and have potential to be outstanding reinforcing fillers in plastics. In these experiments, the fibers and polypropylene (PP) were blended in a thermokinetic mixer and then injection molded, with the fiber weight fractions varying to 60%. A maleated polypropylene was used to improve the interaction and adhesion between the nonpolar matrix and the polar lignocellulosic fibers. The specific tensile and flexural moduli of a 50% by weight (39% by volume) of kenaf-PP composite compare favorably with a 40% by weight of glass fiber-PP injection-molded composite. These results suggest that kenaf fibers are a viable alternative to inorganic/mineral-based reinforcing fibers as long as the right processing conditions are used and they are used in applications where the higher water absorption is not critical.

  8. Renewable agricultural fibers as reinforcing fillers in plastics: Mechanical properties of Kenaf fiber-polpyropylene composites

    SciTech Connect

    Sanadi, A.R.; Caulfield, D.F.; Jacobson, R.E.

    1995-12-01

    Kenaf (Hibiscus Cannabinus) is a fast growing annual growth plant that is harvested for its bast fibers. These fibers have excellent specific properties and have potential to be outstanding reinforcing fillers in plastics. In our experiments, the fibers and polypropylene (PP) were blended in a thermokinetic mixer and then injection molded, with the fiber weight fractions varying to 60%. A maleated polypropylene was used to improve the interaction and adhesion between the non-polar matrix and the polar lignocellulosic fibers. The specific tensile and flexural moduli of a 50 % by volume (39 % by volume) of kenaf-PP composites compares favorably with a 40 % by weight of glass fiber-PP injection molded composites, These results suggest that kenaf fibers are a viable alternative to inorganic/mineral based reinforcing fibers as long as the right processing conditions are used and for applications where the higher water absorption is not critical.

  9. Response of fiber reinforced sandwich structures subjected to explosive loading

    SciTech Connect

    Perotti, Luigi E.; El Sayed, Tamer; Deiterding, Ralf; Ortiz, Michael

    2011-01-01

    The capability to numerically simulate the response of sandwich structures to explosive loading constitutes a powerful tool to analyze and optimize their design by investigating the influence of different parameters. In order to achieve this objective, the necessary models for foam core and fiber reinforced materials in finite kinematics have been developed together with a finite element scheme which includes C1 finite elements for shells and cohesive elements able to capture the fracture propagation in composite fiber reinforced materials. This computational capability has been used to investigate the response of fiber reinforced sandwich shells to explosive loading. Based on the dissipated fracture energy resulting from these simulations, a factorial design has been carried out to assess the effect of different parameters on the sandwich shell response creating a tool for its optimization.

  10. Stress concentration in notched anisotropically fiber-reinforced plates

    NASA Astrophysics Data System (ADS)

    Hufenbach, W.; Kroll, L.

    1992-06-01

    As notches represent the most relevant sites of failure in a construction, a calculation of the stress distribution around holes is essential for the design of fiber-reinforced materials. Especially in the case of anisotropic materials the maximal stress concentration factor on the cutout is considerably higher than in conventional isotropic materials. In fiber-reinforced materials the stress distribution around holes is strongly dependent on the degree of anisotropy as well as on the notch geometry and load parameters. The plain stress field around a notch of known geometry will be calculated by means of the method of conformal mapping and complex stress functions, based on the mathematical model of an infinite anisotropic plate with various shapes of the aperture. For some standard types of notches and load cases, the stress concentration factor as a function of various construction parameters will be studied for fiber-reinforced materials used in lightweight construction.

  11. Durability of waste glass flax fiber reinforced mortar

    SciTech Connect

    Aly, M.; Hashmi, M. S. J.; Olabi, A. G.; Messeiry, M.

    2011-01-17

    The main concern for natural fibre reinforced mortar composites is the durability of the fibres in the alkaline environment of cement. The composites may undergo a reduction in strength as a result of weakening of the fibres by a combination of alkali attack and fibre mineralisation. In order to enhance the durability of natural fiber reinforced cement composites several approaches have been studied including fiber impregnation, sealing of the matrix pore system and reduction of matrix alkalinity through the use of pozzolanic materials. In this study waste glass powder was used as a pozzolanic additive to improve the durability performance of flax fiber reinforced mortar (FFRM). The durability of the FFRM was studied by determining the effects of ageing in water and exposure to wetting and drying cycles; on the microstructures and flexural behaviour of the composites. The mortar tests demonstrated that the waste glass powder has significant effect on improving the durability of FFRM.

  12. Laser transmission welding of long glass fiber reinforced thermoplastics

    NASA Astrophysics Data System (ADS)

    van der Straeten, Kira; Engelmann, Christoph; Olowinsky, Alexander; Gillner, Arnold

    2015-03-01

    Joining fiber reinforced polymers is an important topic for lightweight construction. Since classical laser transmission welding techniques for polymers have been studied and established in industry for many years joint-strengths within the range of the base material can be achieved. Until now these processes are only used for unfilled and short glass fiber-reinforced thermoplastics using laser absorbing and laser transparent matrices. This knowledge is now transferred to joining long glass fiber reinforced PA6 with high fiber contents without any adhesive additives. As the polymer matrix and glass fibers increase the scattering of the laser beam inside the material, their optical properties, changing with material thickness and fiber content, influence the welding process and require high power lasers. In this article the influence of these material properties (fiber content, material thickness) and the welding parameters like joining speed, laser power and clamping pressure are researched and discussed in detail. The process is also investigated regarding its limitations. Additionally the gap bridging ability of the process is shown in relation to material properties and joining speed.

  13. Automobile materials competition: energy implications of fiber-reinforced plastics

    SciTech Connect

    Cummings-Saxton, J.

    1981-10-01

    The embodied energy, structural weight, and transportation energy (fuel requirement) characteristics of steel, fiber-reinforced plastics, and aluminum were assessed to determine the overall energy savings of materials substitution in automobiles. In body panels, a 1.0-lb steel component with an associated 0.5 lb in secondary weight is structurally equivalent to a 0.6-lb fiber-reinforced plastic component with 0.3 lb in associated secondary weight or a 0.5-lb aluminum component with 0.25 lb of secondary weight. (Secondary weight refers to the combined weight of the vehicle's support structure, engine, braking system, and drive train, all of which can be reduced in response to a decrease in total vehicle weight.) The life cycle transportation energy requirements of structurally equivalent body panels (including their associated secondary weights) are 174.4 x 10/sup 3/ Btu for steel, 104.6 x 10/sup 3/ Btu for fiber-reinforced plastics, and 87.2 x 10/sup 3/ Btu for aluminum. The embodied energy requirements are 37.2 x 10/sup 3/ Btu for steel, 22.1 x 10/sup 3/ Btu for fiber-reinforced plastics, and 87.1 x 10/sup 3/ Btu for aluminum. These results can be combined to yield total energy requirements of 211.6 x 10/sup 3/ Btu for steel, 126.7 x 10/sup 3/ Btu for fiber-reinforced plastics, and 174.3 x 10/sup 3/ Btu for aluminum. Fiber-reinforced plastics offer the greatest improvements over steel in both embodied and total energy requirements. Aluminum achieves the greatest savings in transportation energy.

  14. Factors Controlling Stress Rupture of Fiber-Reinforced Ceramic Composites

    NASA Technical Reports Server (NTRS)

    DiCarlo, J. A.; Yun, H. M.

    1999-01-01

    The successful application of fiber-reinforced ceramic matrix composites (CMC) depends strongly on maximizing material rupture life over a wide range of temperatures and applied stresses. The objective of this paper is to examine the various intrinsic and extrinsic factors that control the high-temperature stress rupture of CMC for stresses below and above those required for cracking of the 0 C plies (Regions I and II, respectively). Using creep-rupture results for a variety of ceramic fibers and rupture data for CMC reinforced by these fibers, it is shown that in those cases where the matrix carries little structural load, CMC rupture conditions can be predicted very well from the fiber behavior measured under the appropriate test environment. As such, one can then examine the intrinsic characteristics of the fibers in order to develop design guidelines for selecting fibers and fiber microstructures in order to maximize CMC rupture life. For those cases where the fiber interfacial coatings are unstable in the test environment, CMC lives are generally worse than those predicted by fiber behavior alone. For those cases where the matrix can support structural load, CMC life can even be greater provided matrix creep behavior is properly controlled. Thus the achievement of long CMC rupture life requires understanding and optimizing the behavior of all constituents in the proper manner.

  15. Evaluation of Fiber Reinforced Cement Using Digital Image Correlation

    PubMed Central

    Melenka, Garrett W.; Carey, Jason P.

    2015-01-01

    The effect of short fiber reinforcements on the mechanical properties of cement has been examined using a splitting tensile – digital image correlation (DIC) measurement method. Three short fiber reinforcement materials have been used in this study: fiberglass, nylon, and polypropylene. The method outlined provides a simple experimental setup that can be used to evaluate the ultimate tensile strength of brittle materials as well as measure the full field strain across the surface of the splitting tensile test cylindrical specimen. Since the DIC measurement technique is a contact free measurement this method can be used to assess sample failure. PMID:26039590

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

    SciTech Connect

    Besmann, T.M.; McLaughlin, J.C.; Probst, K.J.; Anderson, T.J.; Starr, T.L.

    1997-12-01

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

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. Fabrication of Fiber-Reinforced Celsian Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Setlock, John A.

    2000-01-01

    A method has been developed for the fabrication of small diameter, multifilament tow fiber reinforced ceramic matrix composites. Its application has been successfully demonstrated for the Hi-Nicalon/celsian system. Strong and tough celsian matrix composites, reinforced with BN/SiC-coated Hi-Nicalon fibers, have been fabricated by infiltrating the fiber tows with the matrix slurry, winding the tows on a drum, cutting and stacking of the prepreg tapes in the desired orientation, and hot pressing. The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from the 0.75BaO-0.25SrO-Al2O3-2SiO2 mixed precursor synthesized by solid state reaction from metal oxides. Hot pressing resulted in almost fully dense fiber-reinforced composites. The unidirectional composites having approx. 42 vol% of fibers exhibited graceful failure with extensive fiber pullout in three-point bend tests at room temperature. Values of yield stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01 percent, respectively, and ultimate strengths of 900 +/- 60 MPa were observed. The Young's modulus of the composites was measured to be 165 +/- 5 GPa.

  2. The assessment of metal fiber reinforced polymeric composites

    NASA Technical Reports Server (NTRS)

    Chung, Wenchiang R.

    1990-01-01

    Because of their low cost, excellent electrical conductivity, high specific strength (strength/density), and high specific modulus (modulus/density) short metal fiber reinforced composites have enjoyed a widespread use in many critical applications such as automotive industry, aircraft manufacturing, national defense, and space technology. However, little data has been found in the study of short metal fibrous composites. Optimum fiber concentration in a resin matrix and fiber aspect ratio (length-to-diameter ratio) are often not available to a user. Stress concentration at short fiber ends is the other concern when the composite is applied to a load-bearing application. Fracture in such composites where the damage will be initiated or accumulated is usually difficult to be determined. An experimental investigation is therefore carefully designed and undertaken to systematically evaluate the mechanical properties as well as electrical properties. Inconel 601 (nickel based) metal fiber with a diameter of eight microns is used to reinforce commercially available thermoset polyester resin. Mechanical testing such as tensile, impact, and flexure tests along with electrical conductivity measurements is conducted to study the feasibility of using such composites. The advantages and limitations of applying chopped metal fiber reinforced polymeric composites are also discussed.

  3. 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.

  4. Flexural retrofitting of reinforced concrete structures using Green Natural Fiber Reinforced Polymer plates

    NASA Astrophysics Data System (ADS)

    Cervantes, Ignacio

    An experimental study will be carried out to determine the suitability of Green Natural Fiber Reinforced Polymer plates (GNFRP) manufactured with hemp fibers, with the purpose of using them as structural materials for the flexural strengthening of reinforced concrete (RC) beams. Four identical RC beams, 96 inches long, are tested for the investigation, three control beams and one test beam. The first three beams are used as references; one unreinforced, one with one layer of Carbon Fiber Reinforced Polymer (CFRP), one with two layers of CFRP, and one with n layers of the proposed, environmental-friendly, GNFRP plates. The goal is to determine the number of GNFRP layers needed to match the strength reached with one layer of CFRP and once matched, assess if the system is less expensive than CFRP strengthening, if this is the case, this strengthening system could be an alternative to the currently used, expensive CFRP systems.

  5. Fiber Reinforced Composites for Insulation and Structures

    NASA Technical Reports Server (NTRS)

    Broughton, Roy M., Jr.

    2005-01-01

    The work involves two areas: Composites, optimum fiber placement with initial construction of a pressure vessel, and the general subject of insulation, a continual concern in harsh thermal environments. Insulation

  6. Dynamic mechanical analysis of fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Reed, K. E.

    1979-01-01

    Dynamic mechanical and thermal properties were determined for unidirectional epoxy/glass composites at various fiber orientation angles. Resonant frequency and relative logarithmic decrement were measured as functions of temperature. In low angle and longitudinal specimens a transition was observed above the resin glass transition temperature which was manifested mechanically as an additional damping peak and thermally as a change in the coefficient of thermal expansion. The new transition was attributed to a heterogeneous resin matrix induced by the fiber. The temperature span of the glass-rubber relaxation was found to broaden with decreasing orientation angle, reflecting the growth of fiber contribution and exhibiting behavior similar to that of Young's modulus. The change in resonant frequency through the glass transition was greatest for samples of intermediate fiber angle, demonstrating behavior similar to that of the longitudinal shear modulus.

  7. 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.

  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. Development of ductile hybrid fiber reinforced polymer (D-H-FRP) reinforcement for concrete structures

    NASA Astrophysics Data System (ADS)

    Somboonsong, Win

    The corrosion of steel rebars has been the major cause of the reinforced concrete deterioration in transportation structures and port facilities. Currently, the Federal Highway Administration (FHWA) spends annually $31 billion for maintaining and repairing highways and highway bridges. The study reported herein represents the work done in developing a new type of reinforcement called Ductile Hybrid Fiber Reinforced Polymer or D-H-FRP using non-corrosive fiber materials. Unlike the previous FRP reinforcements that fail in a brittle manner, the D-H-FRP bars exhibit the stress-strain curves that are suitable for concrete reinforcement. The D-H-FRP stress-strain curves are linearly elastic with a definite yield point followed by plastic deformation and strain hardening resembling that of mild steel. In addition, the D-H-FRP reinforcement has integrated ribs required for concrete bond. The desirable mechanical properties of D-H-FRP reinforcement are obtained from the integrated design based on the material hybrid and geometric hybrid concepts. Using these concepts, the properties can be tailored to meet the specific design requirements. An analytical model was developed to predict the D-H-FRP stress-strain curves with different combination of fiber materials and geometric configuration. This model was used to optimize the design of D-H-FRP bars. An in-line braiding-pultrusion manufacturing process was developed at Drexel University to produce high quality D-H-FRP reinforcement in diameters that can be used in concrete structures. A series of experiments were carried out to test D-H-FRP reinforcement as well as their individual components in monotonic and cyclic tensile tests. Using the results from the tensile tests and fracture analysis, the stress-strain behavior of the D-H-FRP reinforcement was fully characterized and explained. Two series of concrete beams reinforced with D-H-FRP bars were studied. The D-H-FRP beam test results were then compared with companion

  10. 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.

  11. 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

  12. Design Guide for glass fiber reinforced metal pressure vessel

    NASA Technical Reports Server (NTRS)

    Landes, R. E.

    1973-01-01

    Design Guide has been prepared for pressure vessel engineers concerned with specific glass fiber reinforced metal tank design or general tank tradeoff study. Design philosophy, general equations, and curves are provided for safelife design of tanks operating under anticipated space shuttle service conditions.

  13. Elastic/viscoplastic constitutive model for fiber reinforced thermoplastic composites

    NASA Technical Reports Server (NTRS)

    Gates, T. S.; Sun, C. T.

    1991-01-01

    A constitutive model to describe the elastic/viscoplastic behavior of fiber-reinforced thermoplastic composites under plane stress conditions is presented. Formulations are given for quasi-static plasticity and time-dependent viscoplasticity. Experimental procedures required to generate the necessary material constants are explained, and the experimental data is compared to the predicted behavior.

  14. COMPRESSION MOLDED, BIO-FIBER REINFORCED, HIGH PERFORMANCE THERMOSET COMPOSITES FOR STRUCTURAL AND SEMI-STRUCTURAL APPLICATIONS

    SciTech Connect

    Fifield, Leonard S.; Simmons, Kevin L.

    2010-09-15

    Major goals for the future of transportation materials include reduced weight of components, reduced cost of materials and increased use of renewable content. Reinforcement of transportation composites with plant fibers has the potential to decrease component weight relative to glass fiber reinforcement, reduce cost of materials relative to carbon fiber reinforcement, and significantly increase the fraction of composite components from a renewable source. Barriers to widespread application of natural fiber reinforced components in structural and semi-structural vehicle applications have included the natural propensity of these materials to uptake moisture and the corresponding loss of mechanical properties with exposure to moisture. Through novel advances in fiber treatment, processing and molding to address moisture absorption and resin interfacing, Pacific Northwest National Laboratory is reducing these barriers. Herein we demonstrate natural fiber reinforced composites that are 1) composed of more than 50wt% renewable content, 2) weigh 17% less than glass fiber composites with the same fiber volume, and 3) exhibit wet mechanical properties suitable for semi-structural application. Lower cost, lower energy in production, and reduced greenhouse gas production are anticipated advantages of the described PNNL technologies.

  15. Fracture behavior of glass fiber reinforced polymer composite

    SciTech Connect

    Avci, A.; Arikan, H.; Akdemir, A

    2004-03-01

    Chopped strand glass fiber reinforced particle-filled polymer composite beams with varying notch-to-depth ratios and different volume fractions of glass fibers were investigated in Mode I fracture using three-point bending tests. Effects of polyester resin content and glass fiber content on fracture behavior was also studied. Polyester resin contents were used 13.00%%, 14.75%, 16.50%, 18.00% and 19.50%, and glass fiber contents were 1% and 1.5% of the total weight of the polymer composite system. Flexural strength of the polymer composite increases with increase in polyester and fiber content. The critical stress intensity factor was determined by using several methods such as initial notch depth method, compliance method and J-integral method. The values of K{sub IC} obtained from these methods were compared.

  16. 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.

  17. Biaxial flexing of a fiber reinforced aluminum composite

    SciTech Connect

    Tsangarakis, N.; Pepi, M.S. )

    1990-07-01

    A disk specimen of silicon carbide continuous fiber reinforced aluminum is used to study the response of the composite to biaxial tensile flexure. The maximum surface principal tensile strain is constant within a radius of 6.1 mm from the center of the disk. The strain is found to be sensitive to the damage introduced in the composite during flexing. Fiber breakage under monotonic loading is initiated within a fiber tensile strain 0.0038-0.0083. Under cyclic loading and for principal surface strain ranges exceeding 0.0035 the dominant damage mechanism leading to failure is fiber breakage. At smaller surface strain ranges, slip bands and cracks formed in the matrix. The limiting value of the cyclic fiber strain range for a life of one million cycles is 0.00132. This strain is 15 percent of the composite failure strain under uniaxial monotonic loading and 50 percent of the maximum strain in uniaxial tensile fatigue. 27 refs.

  18. Micromechanical aspects of failure in unidirectional fiber reinforced composites

    NASA Astrophysics Data System (ADS)

    Oguni, Kenji

    Micromechanical aspects of failure in unidirectional fiber reinforced composites are investigated using combined experimental and analytical methods. Results from an experimental investigation on mechanical behavior of a unidirectional fiber reinforced polymer composite (E-glass/vinylester) with 50% fiber volume fraction under quasi-static uniaxial and proportional multiaxial compression are presented. Detailed examination of the specimen during and after the test reveals the failure mode transition from axial splitting to kink band formation as the loading condition changes from uniaxial to multiaxial compression. Motivated by the experimental observations, an energy-based model is developed to provide an analytical estimate of the critical stress for axial splitting observed in unidirectional fiber reinforced composites under uniaxial compression in the fiber direction (also with weak lateral confinement). The analytic estimate for the compressive strength is used to illustrate its dependence on material properties, surface energy, fiber volume fraction, fiber diameter and lateral confining pressure. To understand the effect of flaws on the strength of unidirectional fiber reinforced composites, a fracture mechanics based model for failure is developed. Based on this model, failure envelope, dominant initial flaw orientation and failure mode for the composites under a wide range of stress states are predicted. Parametric study provides quantitative evaluation of the effect of various mechanical and physical properties on failure behavior and identifies their influence on strength. Finally, results from an experimental investigation on the dynamic mechanical behavior of unidirectional E-glass/vinylester composites with 30%, 50% fiber volume fraction under uniaxial compression are presented. Limited experimental results are also presented for the 50% fiber volume fraction composite under dynamic proportional lateral confinement. Specimens are loaded in the fiber

  19. Optically transparent composites reinforced with plant fiber-based nanofibers

    NASA Astrophysics Data System (ADS)

    Iwamoto, S.; Nakagaito, A. N.; Yano, H.; Nogi, M.

    2005-11-01

    The fibrillation of pulp fiber was attempted by two methods, a high-pressure homogenizer treatment and a grinder treatment. The grinder treatment resulted in the successful fibrillation of wood pulp fibers into nanofibers. The nanofibers demonstrate promising characteristics as reinforcement material for optically transparent composites. Due to the size effect, the nanofiber-reinforced composite retains the transparency of the matrix resin even at high fiber content such as 70 wt %. Since the nanofiber is an aggregate of semi-crystalline extended cellulose chains, its addition also contributes to a significant improvement in the thermal expansion properties of plastics while maintaining its ease of bending. Cellulose nanofibers have tremendous potential as a future resource since they are produced in a sustainable manner by plants, one of the most abundant organic resources on earth.

  20. Effect of thermal shock on fiber-reinforced superalloy composites

    NASA Technical Reports Server (NTRS)

    Yuen, J. L.; Schnittgrund, G. D.; Petrasek, D. W.

    1990-01-01

    An evaluation is presented of the thermal shock behavior of tungsten fiber-reinforced superalloy (FRS) composites with respect to the turbine blade requirements of rocket engine turbopumps. Each composite was reinforced unidirectionally with 40-volume-pct continuous tungsten fibers. The start-up conditions of the first-stage turbine blades of the high-pressure fuel turbopump in the Space Shuttle Main Engine (SSME) were used to investigate the thermal shock behavior of these materials. The FRS composites showed excellent thermal shock resistance, two to nine times better than the turbine blade material used in the SSME. Thermal shock cycling produced microcracks on the surfaces of the irradiated area that were less than 0.13 mm long and 0.005 mm deep. Neither fiber/matrix debonding nor microvoiding was observed.

  1. Esthetic considerations when splinting with fiber-reinforced composites.

    PubMed

    Strassler, Howard E; Serio, Cheryl L

    2007-04-01

    The primary reasons for splinting and stabilizing teeth are to connect them for the purpose of replacing missing teeth or as an adjunct to periodontal therapy. Although the restorations must be planned to withstand the functional requirements of occlusion and mastication, esthetic considerations must also be taken into account. The challenge in creating an esthetic result with fiber-reinforced composite splints is that there is limited space in the connector region to create the three-dimensional effect required to give teeth the appearance of individuality. Careful planning in the diagnosis and treatment of the fiber splint is essential to allow for adequate tooth preparation to give the illusion of nonsplinted teeth. When missing teeth are replaced with a fiber-reinforced, direct, fixed partial denture, the pontic must be created to achieve an esthetically pleasing result. PMID:17532925

  2. Making Glass-Fiber-Reinforced Coolant Tubes

    NASA Technical Reports Server (NTRS)

    Curtin, F.

    1985-01-01

    New use found for heat-shrinkable sleeves. Smooth, noncontaminating channels for transporting cooling water in Space Shuttle Extravehicularmobility unit made of fiberglass tubing with aid of heat-shrinkable sleeves. Previously, glass fibers from inner walls of tubes contaminate water.

  3. A micromorphic model for steel fiber reinforced concrete.

    PubMed

    Oliver, J; Mora, D F; Huespe, A E; Weyler, R

    2012-10-15

    A new formulation to model the mechanical behavior of high performance fiber reinforced cement composites with arbitrarily oriented short fibers is presented. The formulation can be considered as a two scale approach, in which the macroscopic model, at the structural level, takes into account the mesostructural phenomenon associated with the fiber-matrix interface bond/slip process. This phenomenon is contemplated by including, in the macroscopic description, a micromorphic field representing the relative fiber-cement displacement. Then, the theoretical framework, from which the governing equations of the problem are derived, can be assimilated to a specific case of the material multifield theory. The balance equation derived for this model, connecting the micro stresses with the micromorphic forces, has a physical meaning related with the fiber-matrix bond slip mechanism. Differently to previous procedures in the literature, addressed to model fiber reinforced composites, where this equation has been added as an additional independent ingredient of the methodology, in the present approach it arises as a natural result derived from the multifield theory. Every component of the composite is defined with a specific free energy and constitutive relation. The mixture theory is adopted to define the overall free energy of the composite, which is assumed to be homogeneously constituted, in the sense that every infinitesimal volume is occupied by all the components in a proportion given by the corresponding volume fraction. The numerical model is assessed by means of a selected set of experiments that prove the viability of the present approach.

  4. Material and Flexural Properties of Fiber-reinforced Rubber Concrete

    NASA Astrophysics Data System (ADS)

    Helminger, Nicholas P.

    The purpose of this research is to determine the material properties of rubber concrete with the addition of fibers, and to determine optimal mixture dosages of rubber and fiber in concrete for structural applications. Fiber-reinforced concrete and rubberized concrete have been researched separately extensively, but this research intends to combine both rubber and fiber in a concrete matrix in order to create a composite material, fiber-reinforced rubber concrete (FRRC). Sustainability has long been important in engineering design, but much of the previous research performed on sustainable concrete does not result in a material that can be used for practical purposes. While still achieving a material that can be used for structural applications, economical considerations were given when choosing the proportions and types of constituents in the concrete mix. Concrete mixtures were designed, placed, and tested in accordance with common procedures and standards, with an emphasis on practicality. Properties that were investigated include compressive strength, tensile strength, modulus of elasticity, toughness, and ductility. The basis for determining the optimal concrete mixture is one that is economical, practical, and exhibits ductile properties with a significant strength. Results show that increasing percentages of rubber tend to decrease workability, unit weight, compressive strength, split tensile strength, and modulus of elasticity while the toughness is increased. The addition of steel needle fibers to rubber concrete increases unit weight, compressive strength, split tensile strength, modulus of elasticity, toughness, and ductility of the composite material.

  5. 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.

  6. Short fiber-reinforced cementitious composites manufactured by extrusion technology

    NASA Astrophysics Data System (ADS)

    Mu, Bin

    The use of short fibers in the cement-based composites is more preferable due to the simplicity and economic nature in fabrication. The short fiber-reinforced cementitious composite (SFRCC) manufactured by the extrusion method show a great improvement in both strength and toughness as compared to the fiber-reinforced composites made by traditional casting methods. This improvement can be attributed to the achievement of low porosity and good interfacial bond in SFRCC under high shear and compressive stress during the extrusion process. In the present study, products of cylinders, sheets, pipes and honeycomb panels incorporating various mineral admixtures such as slag, silica fume, and metakaolin have been manufactured by the extrusion technology. Two kinds of short fibers, ductile polyvinyl alcohol (PVA) fibers and stronger but less ductile glass fibers, were used as the reinforcement in the products. After the specimens were extruded, tension, bending and impact tests were performed to study the mechanical properties of these products. The rheology test was performed for each mix to determine its viscoelastic properties. In addition, X-ray diffraction (XRD) and scanning electronic microscopy (SEM) technology were employed to get an insight view of the mechanism. A freezing and thawing experiment (ASTM C666) was also carried to investigate the durability of the specimens. Based on these experimental results, the reinforcing behaviors of these two short fibers were investigated. The enhancing effects of silica fume and metakaolin on the extrudates were compared and discussed. Finally, the optimum amount of silica fume and slag was proposed. Since the key point for a successful extrusion is the properly designed rheology which controls both internal and external flow properties of extrudate, a nonlinear viscoelastic model was applied to investigate the rheological behavior of a movable fresh cementitious composite in an extruder channel. The velocity profile of the

  7. Cellulose fiber reinforced nylon 6 or nylon 66 composites

    NASA Astrophysics Data System (ADS)

    Xu, Xiaolin

    Cellulose fiber was used to reinforce higher melting temperature engineering thermoplastics, such as nylon 6 and nylon 66. The continuous extrusion - direct compression molding processing and extrusion-injection molding were chosen to make cellulose fiber/nylon 6 or 66 composites. Tensile, flexural and Izod impact tests were used to demonstrate the mechanical properties of the composites. The continuous extrusion-compression molding processing can decrease the thermal degradation of cellulose fiber, but fiber doesn't disperse well with this procedure. Injection molding gave samples with better fiber dispersion and less void content, and thus gave better mechanical properties than compression molding. Low temperature compounding was used to extrude cellulose fiber/nylon composites. Plasticizer and a ceramic powder were used to decrease the processing temperature. Low temperature extrusion gave better mechanical properties than high temperature extrusion. The tensile modulus of nylon 6 composite with 30% fiber can reach 5GPa; with a tensile strength of 68MPa; a flexural modulus of 4GPa, and a flexural strength of 100MPa. The tensile modulus of nylon 66 composites with 30% fiber can reach 5GPa; with a flexural modulus of 5GPa; a tensile strength of 70MPa; and a flexural strength of 147MPa. The effect of thermal degradation on fiber properties was estimated. The Halpin-Tsai model and the Cox model were used to estimate the composite modulus. The Kelly-Tyson model was used to estimate the composite strength. The result indicates that the change of fiber properties determines the final properties of composites. Fiber length has a minor affect on both modulus and strength as long as the fiber length is above the critical length.

  8. Ageing characteristics of aluminium alloy aluminosilicate discontinuous fiber reinforced composites

    SciTech Connect

    Nath, D.; Singh, V.

    1999-03-05

    Development of continuous fiber reinforced metal matrix composites is aimed at providing high specific strength and stiffness needed for aerospace and some critical high temperature structural applications. Considerable efforts have been made, during the last decade, to improve the strength of age-hardening aluminium alloy matrix composites by suitable heat treatment. It has also been well established that age-hardenable aluminium alloy composites show accelerated ageing behavior because of enhanced dislocation density at the fiber/matrix interface resulting from thermal expansion mismatch between ceramic fiber and the metal matrix. The accelerated ageing of aluminium alloy composites either from dislocation density or the residual stress, as a result of thermal expansion mismatch is dependent on the size of whisker and particulate. Investigations have also been made on the effect of volume fraction of particulate on the ageing behavior of aluminium alloys. The present investigation is concerned with characterization of age-hardening behavior of an Al-Si-Cu-Mg(AA 336) alloy alumino-silicate discontinuous fiber-reinforced composites (referred to as aluminium MMCs in the present text) being developed for automotive pistons. An effort is made to study the effect of volume fraction of the reinforcement on age-hardening behavior of this composite.

  9. 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.

  10. 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.

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

    PubMed

    Wu, Yankai; Li, Yanbin; Niu, Bin

    2014-01-01

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

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

    PubMed

    Wu, Yankai; Li, Yanbin; Niu, Bin

    2014-01-01

    Fiber reinforcement is widely used in construction engineering to improve the mechanical properties of soil because it increases the soil's strength and improves the soil's mechanical properties. However, the mechanical properties of fiber-reinforced soils remain controversial. The present study investigated the mechanical properties of silty clay reinforced with discrete, randomly distributed sisal fibers using triaxial shear tests. The sisal fibers were cut to different lengths, randomly mixed with silty clay in varying percentages, and compacted to the maximum dry density at the optimum moisture content. The results indicate that with a fiber length of 10 mm and content of 1.0%, sisal fiber-reinforced silty clay is 20% stronger than nonreinforced silty clay. The fiber-reinforced silty clay exhibited crack fracture and surface shear fracture failure modes, implying that sisal fiber is a good earth reinforcement material with potential applications in civil engineering, dam foundation, roadbed engineering, and ground treatment. PMID:24982951

  13. New Fiber Reinforced Waterless Concrete for Extraterrestrial Structural Applications

    NASA Technical Reports Server (NTRS)

    Toutanji, H.; Tucker, D.; Ethridge, E.

    2005-01-01

    Commercial use of sulfur concrete on Earth is well established, particularly in corrosive, e.g., acid and salt, environments. Having found troilite (FeS) on the Moon raises the question of using extracted sulfur as a lunar construction mate: iii an attractive alternative to conventional concrete as it does not require water For the purpose of this paper it is assumed that lunar ore is mined, refined, and the raw sulfur processed with appropriate lunar regolith to form, for example, brick and beam elements. Glass fibers produced from regolith were used as a reinforcement to improve the mechanical properties of the sulfur concrete. Glass fibers and glass rebar were produced by melting the lunar regolith simulant. Lunar regolith stimulant was melted in a 25 cc Pt-Rh crucible in a Sybron Thermoline 46100 high temperature MoSi2 furnace at melting temperatures of 1450 to 1600G. The glass melt wets the ceramic rod and long continuous glass fibers were easily hand drawn. The glass fibers were immediately coated with a protective polymer to maintain the mechanical strength. The viability of sulfur concrete as a construction material for extraterrestrial application is presented. The mechanical properties of the glass fiber reinforced sulfur concrete were investigated.

  14. 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.

  15. Simulations of Fiber Distribution Effects in Fiber-Reinforced Cement Composites

    SciTech Connect

    Bolander, John E.; Lim, Yun Mook

    2008-02-15

    This paper describes a lattice model for coupled moisture transport/stress analyses of fiber-reinforced cement composites (FRCC). Each fiber, and its interface with the matrix material, is explicitly represented within the three-dimensional material volume. This enables the direct study of fiber orientation and distribution effects on composite performance. Realistic, nonuniform fiber distributions can be specified as model input. Basic applications of the model are presented, with emphasis toward simulating the durability mechanics of FRCC exposed to drying environments. The modeling of functionally graded FRCC is an obvious potential extension of this work.

  16. Graphite fiber reinforced structure for supporting machine tools

    DOEpatents

    Knight, Jr., Charles E.; Kovach, Louis; Hurst, John S.

    1978-01-01

    Machine tools utilized in precision machine operations require tool support structures which exhibit minimal deflection, thermal expansion and vibration characteristics. The tool support structure of the present invention is a graphite fiber reinforced composite in which layers of the graphite fibers or yarn are disposed in a 0/90.degree. pattern and bonded together with an epoxy resin. The finished composite possesses a low coefficient of thermal expansion and a substantially greater elastic modulus, stiffness-to-weight ratio, and damping factor than a conventional steel tool support utilized in similar machining operations.

  17. 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.

  18. 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

  19. High strain-rate model for fiber-reinforced composites

    SciTech Connect

    Aidun, J.B.; Addessio, F.L.

    1995-07-01

    Numerical simulations of dynamic uniaxial strain loading of fiber-reinforced composites are presented that illustrate the wide range of deformation mechanisms that can be captured using a micromechanics-based homogenization technique as the material model in existing continuum mechanics computer programs. Enhancements to the material model incorporate high strain-rate plastic response, elastic nonlinearity, and rate-dependent strength degradation due to material damage, fiber debonding, and delamination. These make the model relevant to designing composite structural components for crash safety, armor, and munitions applications.

  20. The role of rapid solidification processing in the fabrication of fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Locci, Ivan E.; Noebe, Ronald D.

    1989-01-01

    Advanced composite processing techniques for fiber reinforced metal matrix composites require the flexibility to meet several widespread objectives. The development of uniquely desired matrix microstructures and uniformly arrayed fiber spacing with sufficient bonding between fiber and matrix to transmit load between them without degradation to the fiber or matrix are the minimum requirements necessary of any fabrication process. For most applications these criteria can be met by fabricating composite monotapes which are then consolidated into composite panels or more complicated components such as fiber reinforced turbine blades. Regardless of the end component, composite monotapes are the building blocks from which near net shape composite structures can be formed. The most common methods for forming composite monotapes are the powder cloth, foil/fiber, plasma spray, and arc spray processes. These practices, however, employ rapid solidification techniques in processing of the composite matrix phase. Consequently, rapid solidification processes play a vital and yet generally overlooked role in composite fabrication. The future potential of rapid solidification processing is discussed.

  1. Basalt fiber reinforced porous aggregates-geopolymer based cellular material

    NASA Astrophysics Data System (ADS)

    Luo, Xin; Xu, Jin-Yu; Li, Weimin

    2015-09-01

    Basalt fiber reinforced porous aggregates-geopolymer based cellular material (BFRPGCM) was prepared. The stress-strain curve has been worked out. The ideal energy-absorbing efficiency has been analyzed and the application prospect has been explored. The results show the following: fiber reinforced cellular material has successively sized pore structures; the stress-strain curve has two stages: elastic stage and yielding plateau stage; the greatest value of the ideal energy-absorbing efficiency of BFRPGCM is 89.11%, which suggests BFRPGCM has excellent energy-absorbing property. Thus, it can be seen that BFRPGCM is easy and simple to make, has high plasticity, low density and excellent energy-absorbing features. So, BFRPGCM is a promising energy-absorbing material used especially in civil defense engineering.

  2. Strain Sharing Assessment in Woven Fiber Reinforced Concrete Beams Using Fiber Bragg Grating Sensors.

    PubMed

    Montanini, Roberto; Recupero, Antonino; De Domenico, Fabrizio; Freni, Fabrizio

    2016-09-22

    Embedded fiber Bragg grating sensors have been extensively used worldwide for health monitoring of smart structures. In civil engineering, they provide a powerful method for monitoring the performance of composite reinforcements used for concrete structure rehabilitation and retrofitting. This paper discusses the problem of investigating the strain transfer mechanism in composite strengthened concrete beams subjected to three-point bending tests. Fiber Bragg grating sensors were embedded both in the concrete tensioned surface and in the woven fiber reinforcement. It has been shown that, if interface decoupling occurs, strain in the concrete can be up to 3.8 times higher than that developed in the reinforcement. A zero friction slipping model was developed which fitted very well the experimental data.

  3. Strain Sharing Assessment in Woven Fiber Reinforced Concrete Beams Using Fiber Bragg Grating Sensors.

    PubMed

    Montanini, Roberto; Recupero, Antonino; De Domenico, Fabrizio; Freni, Fabrizio

    2016-01-01

    Embedded fiber Bragg grating sensors have been extensively used worldwide for health monitoring of smart structures. In civil engineering, they provide a powerful method for monitoring the performance of composite reinforcements used for concrete structure rehabilitation and retrofitting. This paper discusses the problem of investigating the strain transfer mechanism in composite strengthened concrete beams subjected to three-point bending tests. Fiber Bragg grating sensors were embedded both in the concrete tensioned surface and in the woven fiber reinforcement. It has been shown that, if interface decoupling occurs, strain in the concrete can be up to 3.8 times higher than that developed in the reinforcement. A zero friction slipping model was developed which fitted very well the experimental data. PMID:27669251

  4. Durability of Cement Composites Reinforced with Sisal Fiber

    NASA Astrophysics Data System (ADS)

    Wei, Jianqiang

    This dissertation focuses mainly on investigating the aging mechanisms and degradation kinetics of sisal fiber, as well as the approaches to mitigate its degradation in the matrix of cement composites. In contrast to previous works reported in the literature, a novel approach is proposed in this study to directly determine the fiber's degradation rate by separately studying the composition changes, mechanical and physical properties of the embedded sisal fibers. Cement hydration is presented to be a crucial factor in understanding fiber degradation behavior. The degradation mechanisms of natural fiber consist of mineralization of cell walls, alkali hydrolysis of lignin and hemicellulose, as well as the cellulose decomposition which includes stripping of cellulose microfibrils and alkaline hydrolysis of amorphous regions in cellulose chains. Two mineralization mechanisms, CH-mineralization and self-mineralization, are proposed. The degradation kinetics of sisal fiber in the cement matrix are also analyzed and a model to predict the degradation rate of cellulose for natural fiber embedded in cement is outlined. The results indicate that the time needed to completely degrade the cellulose in the matrix with cement replacement by 30wt.% metakaolin is 13 times longer than that in pure cement. A novel and scientific method is presented to determine accelerated aging conditions, and to evaluating sisal fiber's degradation rate and durability of natural fiber-reinforced cement composites. Among the static aggressive environments, the most effective approach for accelerating the degradation of natural fiber in cement composites is to soak the samples or change the humidity at 70 °C and higher temperature. However, the dynamic wetting and drying cycling treatment has a more accelerating effect on the alkali hydrolysis of fiber's amorphous components evidenced by the highest crystallinity indices, minimum content of holocellulose, and lowest tensile strength. Based on the

  5. 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.

  6. Dynamic tensile strength of glass fiber reinforced pultruded composites

    SciTech Connect

    Dutta, P.K.; Kumar, M.M.; Hui, D.

    1994-12-31

    This paper discusses the stress-strain behavior, fracture strength, influence of low temperature, and energy absorption in the diametral tensile splitting fracturing of a Glass Fiber Reinforced Polymer Composite. Experiments were conducted at low-temperature in a thermal chamber installed on a servo-hydraulic universal testing machine. The tensile strength was determined by diametral compression of disc samples at 24, {minus}5 and {minus}40 C.

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

    SciTech Connect

    Besmann, T.M.; Stinton, D.P.; Matlin, W.M.; Liaw, P.K.

    1996-08-01

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

  8. Elastic/viscoplastic behavior of fiber-reinforced thermoplastic composites

    NASA Technical Reports Server (NTRS)

    Wang, C.; Sun, C. T.; Gates, T. S.

    1990-01-01

    An elastic/viscoplastic constitutive model was used to characterize the nonlinear and rate dependent behavior of a continuous fiber-reinforced thermoplastic composite. This model was incorporated into a finite element program for the analysis of laminated plates and shells. Details on the finite element formulation with the proposed constitutive model were presented. The numerical results were compared with experimental data for uniaxial tension and three-point bending tests of (+ or - 45 deg)3s APC-2 laminates.

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

    SciTech Connect

    Besmann, T.M.; Matlin, W.M.; Stinton, D.P.; Liaw, P.K.

    1996-06-01

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

  10. Fracture Toughness Micromechanics by Energy Methods With a Photocure Fiber-Reinforced Composite

    PubMed Central

    Petersen, Richard C.; Lemons, Jack E.; McCracken, Michael S.

    2014-01-01

    A fracture toughness analysis for discontinuous fiber reinforcement was evaluated as a function of fiber volume percent (Vf) using advanced flexural bend tests. Fully articulated fixtures with 40-mm spans were used to examine specimens (2 × 2 × 50 mm3) under conditions of Euler-type bending to reduce shearing effects. Testing for fracture toughness in standardized international units (kJ/m2) using fundamental mechanics-of-materials energy methods by strain energy was then applied for assessment of resilience and work of fracture (WOF). Fracture toughness was also measured as strain energy release (SERIC) for the condition of unstable fracture between peak load and 5% maximum deflection past peak load. Energies were calculated by numerical integration using the trapezoidal rule from the area under the load–deflection curve. Fracture depths were normalized using sample dimensions from microscopy imaging for a combined correlation matrix analysis of all mechanical test data. Vf significantly correlated with resilience, WOF, and SERIC, but negatively correlated with degree of crack depth with p < 0.0000005. All measured interrelated properties also significantly correlated with one another (p < 0.000001). Significant fracture toughness differences between particulate-filled and fiber-reinforced composites began when adding fiber reinforcement at 10.3 Vf for resilience, 5.4 Vf for WOF, and 5.4 Vf for SERIC (p < 0.05). PMID:25346562

  11. Fracture Toughness Micromechanics by Energy Methods With a Photocure Fiber-Reinforced Composite.

    PubMed

    Petersen, Richard C; Lemons, Jack E; McCracken, Michael S

    2007-06-01

    A fracture toughness analysis for discontinuous fiber reinforcement was evaluated as a function of fiber volume percent (Vf) using advanced flexural bend tests. Fully articulated fixtures with 40-mm spans were used to examine specimens (2 × 2 × 50 mm(3)) under conditions of Euler-type bending to reduce shearing effects. Testing for fracture toughness in standardized international units (kJ/m(2)) using fundamental mechanics-of-materials energy methods by strain energy was then applied for assessment of resilience and work of fracture (WOF). Fracture toughness was also measured as strain energy release (SERIC) for the condition of unstable fracture between peak load and 5% maximum deflection past peak load. Energies were calculated by numerical integration using the trapezoidal rule from the area under the load-deflection curve. Fracture depths were normalized using sample dimensions from microscopy imaging for a combined correlation matrix analysis of all mechanical test data. Vf significantly correlated with resilience, WOF, and SERIC, but negatively correlated with degree of crack depth with p < 0.0000005. All measured interrelated properties also significantly correlated with one another (p < 0.000001). Significant fracture toughness differences between particulate-filled and fiber-reinforced composites began when adding fiber reinforcement at 10.3 Vf for resilience, 5.4 Vf for WOF, and 5.4 Vf for SERIC (p < 0.05).

  12. 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

  13. 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.

  14. 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

  15. Some properties of an advanced boron fiber

    NASA Technical Reports Server (NTRS)

    Behrendt, D. R.

    1979-01-01

    An advanced coreless boron fiber has exhibited tensile strengths which are more than twice that of the normal CVD B/W fibers. The coreless fiber is made by the chemical removal of the tungsten boride core exposed by splitting the as-grown fiber. The easily splittable fiber is made by the chemical vapor deposition of boron on a larger than usual tungsten substrate. It is expected that the ease of splitting is related to residual stresses in these fibers. Measurements of the axial residual stresses in both the normal and the splittable fibers are presented and the results compared. Differences in these stresses are discussed in connection with the ease of splitting in the splittable fibers.

  16. Fire resistance properties of ceramic wool fiber reinforced intumescent coatings

    NASA Astrophysics Data System (ADS)

    Amir, N.; Othman, W. M. S. W.; Ahmad, F.

    2015-07-01

    This research studied the effects of varied weight percentage and length of ceramic wool fiber (CWF) reinforcement to fire retardant performance of epoxy-based intumescent coating. Ten formulations were developed using ammonium polyphosphate (APP), expandable graphite (EG), melamine (MEL) and boric acid (BA). The mixing was conducted in two stages; powdered materials were grinded in Rocklabs mortar grinder and epoxy-mixed using Caframo mixer at low speed mixing. The samples were applied on mild steel substrate and exposed to 500°C heat inside Carbolite electric furnace. The char expansion and its physical properties were observed. Scanning electron microscopy (SEM) analyses were conducted to inspect the fiber dispersion, fiber condition and the cell structure of both coatings and chars produced. Thermogravimetric analyses (TGA) were conducted to study the thermal properties of the coating such as degradation temperature and residual weight. Fire retardant performance was determined by measuring backside temperature of substrate in 1-hour, 1000°C Bunsen burner test according to UL 1709 fire regime. The results showed that intumescent coating reinforced with CWF produced better fire resistance performance. When compared to unreinforced coating, formulation S6-15 significantly reduced steel temperature at approximately 34.7% to around 175°C. However, higher fiber weight percentage had slightly decreased fire retardant performance of the coating.

  17. Fire resistance properties of ceramic wool fiber reinforced intumescent coatings

    SciTech Connect

    Amir, N. Othman, W. M. S. W. Ahmad, F.

    2015-07-22

    This research studied the effects of varied weight percentage and length of ceramic wool fiber (CWF) reinforcement to fire retardant performance of epoxy-based intumescent coating. Ten formulations were developed using ammonium polyphosphate (APP), expandable graphite (EG), melamine (MEL) and boric acid (BA). The mixing was conducted in two stages; powdered materials were grinded in Rocklabs mortar grinder and epoxy-mixed using Caframo mixer at low speed mixing. The samples were applied on mild steel substrate and exposed to 500°C heat inside Carbolite electric furnace. The char expansion and its physical properties were observed. Scanning electron microscopy (SEM) analyses were conducted to inspect the fiber dispersion, fiber condition and the cell structure of both coatings and chars produced. Thermogravimetric analyses (TGA) were conducted to study the thermal properties of the coating such as degradation temperature and residual weight. Fire retardant performance was determined by measuring backside temperature of substrate in 1-hour, 1000°C Bunsen burner test according to UL 1709 fire regime. The results showed that intumescent coating reinforced with CWF produced better fire resistance performance. When compared to unreinforced coating, formulation S6-15 significantly reduced steel temperature at approximately 34.7% to around 175°C. However, higher fiber weight percentage had slightly decreased fire retardant performance of the coating.

  18. Effect of Plasma and Fiber Position on Flexural Properties of a Polyethylene Fiber-Reinforced Composite.

    PubMed

    Spyrides, Silvana M M; Prado, Maíra do; Simão, Renata Antoun; Bastian, Fernando Luis

    2015-10-01

    The aim of this study was to evaluate the effect of plasma treatment using argon and oxygen gases, combined with fiber position on flexural properties of a fiber-reinforced composite. Eleven groups were evaluated, a non-reinforced control group and 10 groups reinforced with InFibra, a woven polyethylene fiber, varying according to the plasma treatment and fiber position. The samples were prepared using a stainless steel two-piece matrix. The three point bending test was performed in an EMIC testing machine. Flexural strength (FS) and flexural deflection (FD) were calculated from initial (IF) and final (FF) failure. Data were evaluated statistically using Kruskal-Wallis and Mann-Whitney tests (p<0.05). For IF, in all groups with fibers placed on the base, the FS and FD values were significantly higher than those positioned away from the base. The highest value of FS was obtained in the group treated with O 3 min (296.2 MPa) and the highest value of FD was obtained in the group treated with 1 min (0.109 mm). For FF the FS and FD values obtained for the groups with fibers positioned away from the base were similar or higher than those placed on the base. The highest FS value was obtained in the group treated with 1 min (317.5 MPa) and the highest FD value was obtained in the group treated with O 3 min (0.177 mm). Plasma treatment influenced FS and FD. Fiber position and plasma treatment affected the flexural properties of a fiber-reinforced composite.

  19. 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.

  20. 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.

  1. Dimensionally stable PET fibers for tire reinforcement. [Polyethylene terephthalate (POLYESTERS)

    SciTech Connect

    Rim, P.B.; Nelson, C.J.

    1991-05-01

    High-modulus, high-tenacity polyethylene terephthalate (PET) fibers have gained wide acceptance in reinforcement for rubber products such as tires and hoses; in geotextiles, and in ropes and cordage. Accordingly, a great deal of fundamental research has been conducted on how the processing and resulting morphology of these thermoplastic fibers affect their physical properties. The translation of these starting fiber properties to those in the final end-use product has received much less attention. This article compares the structure-property relationships of recently-developed PET yarns possessing high dimensional stability (i.e., high modulus and low shrinkage) with conventional PET tire yarn. Interest in these materials is stimulated by their ability to improve tire uniformity and, for some tire manufacturers, eliminate the need for post-cure inflation during tire manufacturing. Where possible, cause and effect relationships will be developed.

  2. Modeling and simulation of continuous fiber-reinforced ceramic composites

    NASA Astrophysics Data System (ADS)

    Bheemreddy, Venkata

    Finite element modeling framework based on cohesive damage modeling, constitutive material behavior using user-material subroutines, and extended finite element method (XFEM), are developed for studying the failure behavior of continuous fiber-reinforced ceramic matrix composites (CFCCs) by the example of a silicon carbide matrix reinforced with silicon carbide fiber (SiC/SiCf) composite. This work deals with developing comprehensive numerical models for three problems: (1) fiber/matrix interface debonding and fiber pull-out, (2) mechanical behavior of a CFCC using a representative volume element (RVE) approach, and (3) microstructure image-based modeling of a CFCC using object oriented finite element analysis (OOF). Load versus displacement behavior during a fiber pull-out event was investigated using a cohesive damage model and an artificial neural network model. Mechanical behavior of a CFCC was investigated using a statistically equivalent RVE. A three-step procedure was developed for generating a randomized fiber distribution. Elastic properties and damage behavior of a CFCC were analyzed using the developed RVE models. Scattering of strength distribution in CFCCs was taken into account using a Weibull probability law. A multi-scale modeling framework was developed for evaluating the fracture behavior of a CFCC as a function of microstructural attributes. A finite element mesh of the microstructure was generated using an OOF tool. XFEM was used to study crack propagation in the microstructure and the fracture behavior was analyzed. The work performed provides a valuable procedure for developing a multi-scale framework for comprehensive damage study of CFCCs.

  3. 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.

  4. Creep behavior for advanced polycrystalline SiC fibers

    SciTech Connect

    Youngblood, G.E.; Jones, R.H.; Kohyama, Akira

    1997-08-01

    A bend stress relaxation (BSR) test is planned to examine irradiation enhanced creep in polycrystalline SiC fibers which are under development for use as fiber reinforcement in SiC/SiC composite. Baseline 1 hr and 100 hr BSR thermal creep {open_quotes}m{close_quotes} curves have been obtained for five selected advanced SiC fiber types and for standard Nicalon CG fiber. The transition temperature, that temperature where the S-shaped m-curve has a value 0.5, is a measure of fiber creep resistance. In order of decreasing thermal creep resistance, with the 100 hr BSR transition temperature given in parenthesis, the fibers ranked: Sylramic (1261{degrees}C), Nicalon S (1256{degrees}C), annealed Hi Nicalon (1215{degrees}C), Hi Nicalon (1078{degrees}C), Nicalon CG (1003{degrees}C) and Tyranno E (932{degrees}C). The thermal creep for Sylramic, Nicalon S, Hi Nicalon and Nicalon CG fibers in a 5000 hr irradiation creep BSR test is projected from the temperature dependence of the m-curves determined during 1 and 100 hr BSR control tests.

  5. Natural Curaua Fiber-Reinforced Composites in Multilayered Ballistic Armor

    NASA Astrophysics Data System (ADS)

    Monteiro, Sergio Neves; Louro, Luis Henrique Leme; Trindade, Willian; Elias, Carlos Nelson; Ferreira, Carlos Luiz; de Sousa Lima, Eduardo; Weber, Ricardo Pondé; Miguez Suarez, João Carlos; da Silva Figueiredo, André Ben-Hur; Pinheiro, Wagner Anacleto; da Silva, Luis Carlos; Lima, Édio Pereira

    2015-10-01

    The performance of a novel multilayered armor in which the commonly used plies of aramid fabric layer were replaced by an equal thickness layer of distinct curaua fiber-reinforced composites with epoxy or polyester matrices was assessed. The investigated armor, in addition to its polymeric layer (aramid fabric or curaua composite), was also composed of a front Al2O3 ceramic tile and backed by an aluminum alloy sheet. Ballistic impact tests were performed with actual 7.62 caliber ammunitions. Indentation in a clay witness, simulating human body behind the back layer, attested the efficacy of the curaua-reinforced composite as an armor component. The conventional aramid fabric display a similar indentation as the curaua/polyester composite but was less efficient (deeper indentation) than the curaua/epoxy composite. This advantage is shown to be significant, especially in favor of the lighter and cheaper epoxy composite reinforced with 30 vol pct of curaua fiber, as possible substitute for aramid fabric in multilayered ballistic armor for individual protection. Scanning electron microscopy revealed the mechanism associated with the curaua composite ballistic performance.

  6. Development of natural fiber reinforced polylactide-based biocomposites

    NASA Astrophysics Data System (ADS)

    Arias Herrera, Andrea Marcela

    Polylactide or PLA is a biodegradable polymer that can be produced from renewable resources. This aliphatic polyester exhibits good mechanical properties similar to those of polyethylene terephthalate (PET). Since 2003, bio-based high molecular weight PLA is produced on an industrial scale and commercialized under amorphous and semicrystalline grades for various applications. Enhancement of PLA crystallization kinetics is crucial for the competitiveness of this biopolymer as a commodity material able to replace petroleum-based plastics. On the other hand, the combination of natural fibers with polymer matrices made from renewable resources, to produce fully biobased and biodegradable polymer composite materials, has been a strong trend in research activities during the last decade. Nevertheless, the differences related to the chemical structure, clearly observed in the marked hydrophilic/hydrophobic character of the fibers and the thermoplastic matrix, respectively, represent a major drawback for promoting strong fiber/matrix interactions. The aim of the present study was to investigate the intrinsic fiber/matrix interactions of PLAbased natural fiber composites prepared by melt-compounding. Short flax fibers presenting a nominal length of ˜1 mm were selected as reinforcement and biocomposites containing low to moderate fiber loading were processed by melt-mixing. Fiber bundle breakage during processing led to important reductions in length and diameter. The mean aspect ratio was decreased by about 50%. Quiescent crystallization kinetics of PLA and biocomposite systems was examined under isothermal and non-isothermal conditions. The nucleating nature of the flax fibers was demonstrated and PLA crystallization was effectively accelerated as the natural reinforcement content increased. Such improvement was controlled by the temperature at which crystallization took place, the liquid-to-solid transition being thermodynamically promoted by the degree of supercooling

  7. Advanced fiber-optic acoustic sensors

    NASA Astrophysics Data System (ADS)

    Teixeira, João G. V.; Leite, Ivo T.; Silva, Susana; Frazão, Orlando

    2014-09-01

    Acoustic sensing is nowadays a very demanding field which plays an important role in modern society, with applications spanning from structural health monitoring to medical imaging. Fiber-optics can bring many advantages to this field, and fiber-optic acoustic sensors show already performance levels capable of competing with the standard sensors based on piezoelectric transducers. This review presents the recent advances in the field of fiber-optic dynamic strain sensing, particularly for acoustic detection. Three dominant technologies are identified — fiber Bragg gratings, interferometric Mach-Zehnder, and Fabry-Pérot configurations — and their recent developments are summarized.

  8. Glass fiber reinforced concrete for terrestrial photovoltaic arrays

    NASA Technical Reports Server (NTRS)

    Maxwell, H.

    1979-01-01

    The use of glass-fiber-reinforced concrete (GRC) as a low-cost structural substrate for terrestrial solar cell arrays is discussed. The properties and fabrication of glass-reinforced concrete structures are considered, and a preliminary design for a laminated solar cell assembly built on a GRC substrate is presented. A total cost for such a photovoltaic module, composed of a Korad acrylic plastic film front cover, an aluminum foil back cover, an ethylene/vinyl acetate pottant/adhesive and a cotton fabric electrical isolator in addition to the GRC substrate, of $9.42/sq m is projected, which is less than the $11.00/sq m cost goal set by the Department of Energy. Preliminary evaluations are concluded to have shown the design capabilities and cost effectiveness of GRC; however, its potential for automated mass production has yet to be evaluated.

  9. Arrangement for connecting a fiber-reinforced plastic pipe to a stainless steel flange

    DOEpatents

    Allais, Arnaud; Hoffmann, Ernst

    2008-02-05

    Arrangement for connecting a fiber-reinforced plastic pipe (18) to a stainless steel flange (12, 16), in which the end of the fiber-reinforced plastic pipe (18) is accommodated in a ring-shaped groove (12a, 16a) in the flange (12, 16), the groove conforming to the dimensions of the fiber-reinforced plastic pipe (18), where the gap remaining between the end of the fiber-reinforced plastic pipe (18) and the ring-shaped groove (12a, 16a) is filled with a sealant (19).

  10. Defect depth measurement of carbon fiber reinforced polymers by thermography

    NASA Astrophysics Data System (ADS)

    Chen, Terry Y.; Chen, Jian-Lun

    2016-01-01

    Carbon fiber reinforced polymers has been widely used in all kind of the industries. However the internal defects can result in the change of material or mechanical properties, and cause safety problem. In this study, step-heating thermography is employed to measure the time series temperature distribution of composite plate. The principle of heat conduction in a flat plate with defect inside is introduced. A temperature separation criterion to determine the depth of defect inside the specimen is obtained experimentally. Applying this criterion to CFRP specimens with embedded defects, the depth of embedded defect in CFRP can be determined quite well from the time series thermograms obtained experimentally.

  11. Postcrack creep of polymeric fiber-reinforced concrete in flexure

    SciTech Connect

    Kurtz, S.; Balaguru, P.

    2000-02-01

    Results of an experimental investigation of the creep-time behavior of polypropylene and nylon fiber-reinforced concrete (FRC) are presented. Gravity loads were applied in flexure to precracked low volume fraction (0.1%) polypropylene and nylon FRC beams. Beams were tested at a range of stress levels to produce three outcomes: load sustained indefinitely (low stress), creep failure (intermediate stress), and rapid failure (high stress). Emphasis was placed on determining the maximum flexural stress that is sustainable indefinitely. The results indicate that polypropylene FRC has higher initial strength but nylon FRC can sustain a higher stress level. For both groups the sustainable stress is much lower than the postcrack strength.

  12. Bond strength of glass fiber reinforced plastics (GFRP) grouted anchors

    SciTech Connect

    Bellavance, E.; Xu, H.; Benmokrane, B.

    1995-11-01

    This paper describes the results of laboratory and field pull-out tests on cement grouted glass fiber reinforced plastic (GFRP) anchors. As an alternative for grouted steel anchors, GFRP bars have many advantages over steel tendons, and can avoid corrosion and some difficulties in transportation, handling, and installation. Three types of 36 GFRP anchors and 20 steel anchors installed in three types of host media: steel pipe, concrete block, and rock mass were tested in the laboratory as well as in the field. The bond strength, load carrying capacity, load-displacement behavior, and critical bond length of cement grouted GFRP anchors were examined in comparison with conventional steel anchors.

  13. Fabrication of fiber reinforced plates with curvilinear layout by 3-D photolithography

    SciTech Connect

    Ogale, A.A.; Renault, T.; Charan, R.; Bagchi, A.

    1994-12-31

    A new technique to rapidly process fiber reinforced resins by 3-D photolithography was recently developed. Reinforcing fibers are added in situ to obtain parts with improved strength, stiffness, and toughness. An automated desktop photolithography unit (ADPU) was designed and built in-house, to add continuous E-glass fibers to the photoresin. The unique feature of this machine is its capability to dispense in situ continuous fibers in any desired direction. To demonstrate the advantages of this process, a case study was conducted, where a rectangular plate with a circular hole in the center was subjected to tensile loading. The parts were made with Somos 3100 resin as the matrix and continuous glass fibers as the reinforcement. The failure load of plates reinforced with a straightline fiber layout and a curvilinear fiber layout are compared. In the curvilinear format, the fibers were dispensed along the principal stress directions.

  14. A comparison of tensile properties of polyester composites reinforced with pineapple leaf fiber and pineapple peduncle fiber

    NASA Astrophysics Data System (ADS)

    Juraidi, J. M.; Shuhairul, N.; Syed Azuan, S. A.; Intan Saffinaz Anuar, Noor

    2013-12-01

    Pineapple fiber which is rich in cellulose, relatively inexpensive, and abundantly available has the potential for polymer reinforcement. This research presents a study of the tensile properties of pineapple leaf fiber and pineapple peduncle fiber reinforced polyester composites. Composites were fabricated using leaf fiber and peduncle fiber with varying fiber length and fiber loading. Both fibers were mixed with polyester composites the various fiber volume fractions of 4, 8 and 12% and with three different fiber lengths of 10, 20 and 30 mm. The composites panels were fabricated using hand lay-out technique. The tensile test was carried out in accordance to ASTM D638. The result showed that pineapple peduncle fiber with 4% fiber volume fraction and fiber length of 30 mm give highest tensile properties. From the overall results, pineapple peduncle fiber shown the higher tensile properties compared to pineapple leaf fiber. It is found that by increasing the fiber volume fraction the tensile properties has significantly decreased but by increasing the fiber length, the tensile properties will be increased proportionally. Minitab software is used to perform the two-way ANOVA analysis to measure the significant. From the analysis done, there is a significant effect of fiber volume fraction and fiber length on the tensile properties.

  15. Fiber-reinforced framework and Ceromer restorations: a technical review.

    PubMed

    Zanghellini, G

    1997-01-01

    The utilization of synthetic resins and ceramics in combination with metal frameworks continues to be the mainstay of crown and bridge prosthetics. Although most of these systems have resulted in years of clinical success, each material when used in combination has inherent properties that induce stresses to the system. The combination of ceramic technology and polymer research, in addition to fiber integration, has resulted in the development and introduction of a new category of crown and bridge materials--a ceromer and fiber-reinforced restorative system. This article examines the history of polymer and ceramic technology, and reports the clinical and research data currently available on one indirect ceromer system (Targis System, Ivoclar Williams, Amherst, NY).

  16. Finite element analysis of fiber-reinforced fixed partial dentures.

    PubMed

    Nakamura, Takashi; Ohyama, Tatsuo; Waki, Tomonori; Kinuta, Soichiro; Wakabayashi, Kazumichi; Takano, Naoki; Yatani, Hirofumi

    2005-06-01

    Two-dimensional finite element models were created for a three-unit posterior fixed partial denture. An experimental resin-impregnated glass fiber was used as the fiber-reinforced composite (FRC) for the framework. The FRC was evaluated using varying combinations of position and thickness, alongside with two types of veneering composite. A load of 50 N simulating bite force was applied at the pontic in a vertical direction. Tensile stress was examined using a finite element analysis program. Model without FRC showed tensile stress concentrations within the veneering composite on the cervical side of the pontic--from the connector area to the bottom of the pontic. Model with FRC at the top of the pontic had almost the same stress distribution as the model without FRC. Models with 0.4-0.8 mm thick FRC positioned at the bottom of the pontic showed maximum tensile stresses reduced by 4-19% within the veneering composite. PMID:16022451

  17. Electrical Insulation Characteristics of Glass Fiber Reinforced Resins

    SciTech Connect

    Tuncer, Enis; Sauers, Isidor; James, David Randy; Ellis, Alvin R

    2009-01-01

    Non-metallic structural materials that act as an electrical insulation are needed for cryogenic power applications. One of the extensively utilized materials is glass fiber reinforced resins (GFRR) and may also be known as GFRP and FRP. They are created from glass fiber cloth that are impregnated with an epoxy resin under pressure and heat. Although the materials based on GFRR have been employed extensively, reports about their dielectric properties at cryogenic temperatures and larger thicknesses are generally lacking in the literature. Therefore to guide electrical apparatus designers for cryogenic applications, GFRR samples with different thicknesses are tested in a liquid nitrogen bath. Scaling relation between the dielectric breakdown strength and the GFFR thickness is established. Their loss tangents are also reported at various frequencies.

  18. Carbon fiber-reinforced carbon as a potential implant material.

    PubMed

    Adams, D; Williams, D F; Hill, J

    1978-01-01

    A carbon fiber-reinforced carbon is being evaluated as a promising implant material. In a unidirectional composite, high strengths (1200 MN/m2 longitudinal flexural strength) and high modulus (140 GN/m2 flexural modulus) may be obtained with an interlaminar shear strength of 18 MN/m2. Alternatively, layers of fibers may be laid in two directions to give more isotopic properties. The compatibility of the material with bone has been studied by implanting specimens in holes drilled in rat femora. For a period of up to 8 weeks, a thin layer of fibrous tissue bridged the gap between bone and implant; but this tissue mineralizes and by 10 weeks, bone can be observed adjacent to the implant, giving firm fixation. Potential applications include endosseous dental implants where a greater strength in the neck than that provided by unreinforced carbon would be advantageous.

  19. The Application of Fiber-Reinforced Materials in Disc Repair

    PubMed Central

    Pei, Bao-Qing; Li, Hui; Zhu, Gang; Li, De-Yu; Fan, Yu-Bo; Wu, Shu-Qin

    2013-01-01

    The intervertebral disc degeneration and injury are the most common spinal diseases with tremendous financial and social implications. Regenerative therapies for disc repair are promising treatments. Fiber-reinforced materials (FRMs) are a kind of composites by embedding the fibers into the matrix materials. FRMs can maintain the original properties of the matrix and enhance the mechanical properties. By now, there are still some problems for disc repair such as the unsatisfied static strength and dynamic properties for disc implants. The application of FRMs may resolve these problems to some extent. In this review, six parts such as background of FRMs in tissue repair, the comparison of mechanical properties between natural disc and some typical FRMs, the repair standard and FRMs applications in disc repair, and the possible research directions for FRMs' in the future are stated. PMID:24383057

  20. Optimum design for fixed partial dentures made of hybrid resin with glass fiber reinforcement by finite element analysis: effect of vertical reinforced thickness on fiber frame.

    PubMed

    Ootaki, Masayuki; Shin-Ya, Akikazu; Gomi, Harunori; Shin-Ya, Akiyoshi; Nakasone, Yuji

    2007-03-01

    By means of finite element analysis, the optimal thickness of fiber framework placed in a fiber-reinforced composite bridge replacing the mandibular first molar was obtained. Test results demonstrated that more than 30% maximum principal stress was reduced by reinforcing with fiber framework in a thickness of up to 0.6 mm for 1.5-mm occlusal clearance. Indeed, maximum principal stress generated in lower embrasure of connectors was reduced from 107 MPa to 70 MPa by maximizing reinforcement effect. PMID:17621946

  1. Bisphenyl-Polymer/Carbon-Fiber-Reinforced Composite Compared to Titanium Alloy Bone Implant

    PubMed Central

    Petersen, Richard C.

    2014-01-01

    Aerospace/aeronautical thermoset bisphenyl-polymer/carbon-fiber-reinforced composites are considered as new advanced materials to replace metal bone implants. In addition to well-recognized nonpolar chemistry with related bisphenol-polymer estrogenic factors, carbon-fiber-reinforced composites can offer densities and electrical conductivity/resistivity properties close to bone with strengths much higher than metals on a per-weight basis. In vivo bone-marrow tests with Sprague-Dawley rats revealed far-reaching significant osseoconductivity increases from bisphenyl-polymer/carbon-fiber composites when compared to state-of-the-art titanium-6-4 alloy controls. Midtibial percent bone area measured from the implant surface increased when comparing the titanium alloy to the polymer composite from 10.5% to 41.6% at 0.8 mm, P < 10−4, and 19.3% to 77.7% at 0.1 mm, P < 10−8. Carbon-fiber fragments planned to occur in the test designs, instead of producing an inflammation, stimulated bone formation and increased bone integration to the implant. In addition, low-thermal polymer processing allows incorporation of minerals and pharmaceuticals for future major tissue-engineering potential. PMID:25553057

  2. Matrix cracking of fiber-reinforced ceramic composites in shear

    NASA Astrophysics Data System (ADS)

    Rajan, Varun P.; Zok, Frank W.

    2014-12-01

    The mechanics of cracking in fiber-reinforced ceramic matrix composites (CMCs) under general loadings remains incomplete. The present paper addresses one outstanding aspect of this problem: the development of matrix cracks in unidirectional plies under shear loading. To this end, we develop a model based on potential energy differences upstream and downstream of a fully bridged steady-state matrix crack. Through a combination of analytical solutions and finite element simulations of the constituent stresses before and after cracking, we identify the dominant stress components that drive crack growth. We show that, when the axial slip lengths are much larger than the fiber diameter and when interfacial slip precedes cracking, the shear stresses in the constituents are largely unaffected by the presence of the crack; the changes that do occur are confined to a 'core' region within a distance of about one fiber diameter from the crack plane. Instead, the driving force for crack growth derives mainly from the axial stresses-tensile in the fibers and compressive in the matrix-that arise upon cracking. These stresses are well-approximated by solutions based on shear-lag analysis. Combining these solutions with the governing equation for crack growth yields an analytical estimate of the critical shear stress for matrix cracking. An analogous approach is used in deriving the critical stresses needed for matrix cracking under arbitrary in-plane loadings. The applicability of these results to cross-ply CMC laminates is briefly discussed.

  3. Life Cycle Assessment of Carbon Fiber-Reinforced Polymer Composites

    SciTech Connect

    Das, Sujit

    2011-01-01

    Carbon fiber-reinforced polymer matrix composites is gaining momentum with the pressure to lightweight vehicles, however energy-intensity and cost remain some of the major barriers before this material could be used in large-scale automotive applications. A representative automotive part, i.e., a 30.8 kg steel floor pan having a 17% weight reduction potential with stringent cash performance requirements has been considered for the life cycle energy and emissions analysis based on the latest developments occurring in the precursor type (conventional textile-based PAN vs. renewable-based lignin), part manufacturing (conventional SMC vs. P4) and fiber recycling technologies. Carbon fiber production is estimated to be about 14 times more energy-intensive than conventional steel production, however life cycle primary energy use is estimated to be quite similar to the conventional part, i.e., 18,500 MJ/part, especially when considering the uncertainty in LCI data that exists from using numerous sources in the literature. Lignin P4 technology offers the most life cycle energy and CO2 emissions benefits compared to a conventional stamped steel technology. With a 20% reduction in energy use in the lignin conversion to carbon fiber and free availability of lignin as a by-product of ethanol and wood production, a 30% reduction in life cycle energy use could be obtained. A similar level of life cycle energy savings could also be obtained with a higher part weight reduction potential of 43%.

  4. A study of damping in fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Chandra, Rakesh; Singh, S. P.; Gupta, K.

    2003-05-01

    Damping contributions from the viscoelastic matrix, interphase and the dissipation resulting from damage sites are considered to evaluate composite material damping coefficients in various loading modes. The paper presents the results of the FEM/Strain energy investigations carried out to predict anisotropic-damping matrix comprising of loss factors η11, η22, η12 and η23 considering the dissipation of energy due to fiber and matrix (two phase) and correlate the same with various micromechanical theories. Damping in three phase (i.e., fiber-interphase-matrix) composite is also calculated as an attempt to understand the effect of interphase. The contribution of energy dissipation due to sliding at the fiber-matrix interface is incorporated to evaluate its effect on η11, η22, η12 and η23 in fiber-reinforced composite having damage in the form of hairline debonding. Comparative studies of the various micromechanical theories/models with FEM/Strain energy method for the prediction of damping coefficients have shown consistency when both the effect of variable nature of stress and the fiber interaction is considered. Parametric damping studies for three phase composite have shown that the change in properties of fiber, matrix and interphase leads to a change in the magnitude of effectiveness of interphase, but the manner in which the interphase would affect the various loss factors depends predominately upon whether the hard or soft interphase is chosen. Analysis of the effect of damage on composite damping indicates that it is sensitive to its orientation and type of loading.

  5. Advanced reinforcement systems for intermetallic applications

    NASA Technical Reports Server (NTRS)

    Merrick, Howard F.; Labib, Mohammed L.

    1993-01-01

    A 2-D axisymmetric model was employed to determine the magnitude of the radial, axial, and hoop stresses caused by the thermal expansion difference between fiber and matrix and which result from the fabrication temperature cycle. Finite element analysis was conducted for single fiber model systems based on SCS-6/Ti3Al+Nb and Al2O3/NiAl. The stress distribution due to the imposition of a graded intermediate layer for each system was determined and included variables of layer thickness and gradation in interlayer chemistry in order to vary the expansion gradient between fiber and matrix. Thermal cycling tests were conducted on sputter coated SCS-6 fibers selectively coated with Ti3Al+Nb, with and without an intermediate layer. Cracking of the Ti3Al+Nb layers was prevented by an interlayer based on Ti-TiN-Ti. The interlayer thickness appeared critical to its efficiency. Similarly, for the case of Al2O3/NiAl, an intermediate layer consisting of a Ni bond coat on the sapphire fiber followed by a graded Al2O3-NiAl layer did not crack when given a thermal excursion to 1100 C and then cooled to room temperature. Acoustic emission tests on single fiber specimens were unsuccessful in detecting load drops associated with the successive fracture of the fiber. For the SCS-6/Ti3Al system this was the result of several factors which included the matrix/fiber ratio and poor bonding of the matrix and fiber. In the case of the Al2O3/NiAl system brittle failure of the NiAl matrix precluded fiber breakdown during tensile loading.

  6. Oxidation-resistant interfacial coatings for fiber-reinforced ceramic composites

    SciTech Connect

    Lara-Curzio, Edgar; More, Karren L.; Lee, Woo Y.

    1999-04-22

    A ceramic-matrix composite having a multilayered interfacial coating adapted to protect the reinforcing fibers from long-term oxidation, while allowing these to bridge the wake of advancing cracks in the matrix, is provided by selectively mismatching materials within adjacent layers of the interfacial coating, the materials having different coefficients of thermal expansion so that a low toughness interface region is created to promote crack deflection either within an interior layer of the mismatched interfacial coating or between adjacent layers of the mismatched interfacial coating.

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

    NASA Astrophysics Data System (ADS)

    Sobhan, Khaled

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

  8. Acoustic emission of fire damaged fiber reinforced concrete

    NASA Astrophysics Data System (ADS)

    Mpalaskas, A. C.; Matikas, T. E.; Aggelis, D. G.

    2016-04-01

    The mechanical behavior of a fiber-reinforced concrete after extensive thermal damage is studied in this paper. Undulated steel fibers have been used for reinforcement. After being exposed to direct fire action at the temperature of 850°C, specimens were subjected to bending and compression in order to determine the loss of strength and stiffness in comparison to intact specimens and between the two types. The fire damage was assessed using nondestructive evaluation techniques, specifically ultrasonic pulse velocity (UPV) and acoustic emission (AE). Apart from the strong, well known, correlation of UPV to strength (both bending and compressive), AE parameters based mainly on the frequency and duration of the emitted signals after cracking events showed a similar or, in certain cases, better correlation with the mechanical parameters and temperature. This demonstrates the sensitivity of AE to the fracture incidents which eventually lead to failure of the material and it is encouraging for potential in-situ use of the technique, where it could provide indices with additional characterization capability concerning the mechanical performance of concrete after it subjected to fire.

  9. 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.

  10. Physico-mechanical properties of chemically treated palm and coir fiber reinforced polypropylene composites.

    PubMed

    Haque, Md Mominul; Hasan, Mahbub; Islam, Md Saiful; Ali, Md Ershad

    2009-10-01

    In this work, palm and coir fiber reinforced polypropylene bio-composites were manufactured using a single extruder and injection molding machine. Raw palm and coir were chemically treated with benzene diazonium salt to increase their compatibility with the polypropylene matrix. Both raw and treated palm and coir fiber at five level of fiber loading (15, 20, 25, 30 and 35 wt.%) was utilized during composite manufacturing. Microstructural analysis and mechanical tests were conducted. Comparison has been made between the properties of the palm and coir fiber composites. Treated fiber reinforced specimens yielded better mechanical properties compared to the raw composites, while coir fiber composites had better mechanical properties than palm fiber ones. Based on fiber loading, 30% fiber reinforced composites had the optimum set of mechanical properties.

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

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Elderidge, Jeffrey I.

    1998-01-01

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

  12. 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.

  13. Monitoring of reinforced composites processed by microwave radiation using fiber-Bragg gratings

    NASA Astrophysics Data System (ADS)

    Barrera, David; Roig, Inma; Sales, Salvador; Emmerich, Rudolf

    2014-05-01

    The use of microwave radiation for curing carbon-fiber reinforced polymer materials (CFRP) can solve the nonhomogeneous heating problems when using conventional techniques based on the use of catalysts and can reduce the processing times. Optical fiber sensors have well-known advantages for Fiber Reinforced Composites (FRC) monitoring. In this paper fiber Bragg gratings (FBGs) are used for online monitoring of the residual stress and distortions produced during the microwave curing process. The CFRP samples are composed by layers of unidirectional carbon fibers and epoxy resin. The results show a very different behavior between the direction of carbon fibers and the perpendicular direction. Results are compared with the conventional processing technique.

  14. Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various fibers

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1990-01-01

    An experimental study was conducted to measure the thermo-oxidative stability of PMR-15 polymer matrix composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers that were studied included graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber-sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

  15. Advanced fiber placement of composite fuselage structures

    NASA Technical Reports Server (NTRS)

    Anderson, Robert L.; Grant, Carroll G.

    1991-01-01

    The Hercules/NASA Advanced Composite Technology (ACT) program will demonstrate the low cost potential of the automated fiber placement process. The Hercules fiber placement machine was developed for cost effective production of composite aircraft structures. The process uses a low cost prepreg tow material form and achieves equivalent laminate properties to structures fabricated with prepreg tape layup. Fiber placement demonstrations planned for the Hercules/NASA program include fabrication of stiffened test panels which represent crown, keel, and window belt segments of a typical transport aircraft fuselage.

  16. Time-dependent failure in fiber-reinforced composites by fiber degradation

    SciTech Connect

    Iyengar, N.; Curtin, W.A.

    1997-04-01

    The failure of fiber-reinforced ceramic and metal matrix composites under a fixed load for extended times occurs because of strength degradation in the constituent fibers. Specifically, the ceramic fibers possess a Weibull strength distribution caused by crack-like flaws, which can grow according to a power-law growth mechanism. Failure of individual fibers causes interfacial slippage and stress redistribution to unfailed fibers, which in turn accelerates the degradation rate of the remaining fibers, and culminates in abrupt failure of the composite after sufficient damage has accumulated. This sequence of events is modeled both analytically and numerically within the Global Load Sharing (GLS) approximation previously utilized for quasi-static loading. Analytically, a general constitutive model for the relationship between the stress on the damaged fiber bundle, the strain in the unbroken fibers, and the extent of damage, is combined with a time-dependent damage evolution equation derived from the slow-crack-growth kinetics to yield an integral equation for the strain vs time at fixed applied load. A simple, accurate but approximate relationship between applied load, time to failure, fiber Weibull modulus, and slow crack growth exponent is presented. The numerical simulations of the same degradation process verify the general accuracy of the failure time obtained from the analytic results. The remaining tensile strength after some time at load but prior to failure is also studied, and the simulation results generally exhibited a more sudden-death failure than the analytical predictions. A specific application to the failure of a Nicalon fiber composite is presented.

  17. Mechanical Behavior of Electrospun Palmfruit Bunch Reinforced Polylactide Composite Fibers

    NASA Astrophysics Data System (ADS)

    Adeosun, S. O.; Akpan, E. I.; Gbenebor, O. P.; Peter, A. A.; Olaleye, Samuel Adebayo

    2016-01-01

    In this study, the mechanical characteristics of electrospun palm fruit bunch reinforced poly lactic acid (PLA) nanofiber composites using treated and untreated filler was examined. Poly lactic acid-palm fruit bunch-dichloromethane blends were electrospun by varying the concentration of the palm fruit bunch between 0 wt.% and 8 wt.%. A constant voltage of 26 kV was applied, the tip-to-collector distance was maintained at 27.5 cm and PLA-palm fruit bunch-dichloromethane (DCM) concentration of 12.5% (w/v) was used. The results revealed that the presence of untreated palm fruit bunch fillers in the electrospun PLA matrix significantly reduces the average diameters of the fibers, causing the formation of beads. As a result there are reductions in tensile strengths of the fibers. The presence of treated palm fruit bunch fillers in the electrospun PLA matrix increases the average diameters of the fibers with improvements in the mechanical properties. The optimal mechanical responses were obtained at 3 wt.% of the treated palm fruit bunch fillers in the PLA matrix. However, increase in the palm fruit fillers (treated and untreated) in the PLA matrix promoted the formation of beads in the nanofiber composites.

  18. 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.

  19. Oxidation Behavior of Carbon Fiber Reinforced Silicon Carbide Composites

    NASA Technical Reports Server (NTRS)

    Valentin, Victor M.

    1995-01-01

    Carbon fiber reinforced Silicon Carbide (C-SiC) composites offer high strength at high temperatures and good oxidation resistance. However, these composites present some matrix microcracks which allow the path of oxygen to the fiber. The aim of this research was to study the effectiveness of a new Silicon Carbide (SiC) coating developed by DUPONT-LANXIDE to enhance the oxidation resistance of C-SiC composites. A thermogravimetric analysis was used to determine the oxidation rate of the samples at different temperatures and pressures. The Dupont coat proved to be a good protection for the SiC matrix at temperatures lower than 1240 C at low and high pressures. On the other hand, at temperatures above 1340 C the Dupont coat did not seem to give good protection to the composite fiber and matrix. Even though some results of the tests have been discussed, because of time restraints, only a small portion of the desired tests could be completed. Therefore, no major conclusions or results about the effectiveness of the coat are available at this time.

  20. Mechanical Properties of Carbon Fiber-Reinforced Aluminum Manufactured by High-Pressure Die Casting

    NASA Astrophysics Data System (ADS)

    Kachold, Franziska; Singer, Robert

    2016-08-01

    Carbon fiber reinforced aluminum was produced by a specially adapted high-pressure die casting process. The MMC has a fiber volume fraction of 27%. Complete infiltration was achieved by preheating the bidirectional, PAN-based carbon fiber body with IR-emitters to temperatures of around 750 °C. The degradation of the fibers, due to attack of atmospheric oxygen at temperatures above 600 °C, was limited by heating them in argon-rich atmosphere. Additionally, the optimization of heating time and temperature prevented fiber degradation. Only the strength of the outer fibers is reduced by 40% at the most. The fibers in core of fiber body are nearly undamaged. In spite of successful manufacturing, the tensile strength of the MMC is below strength of the matrix material. Also unidirectional MMCs with a fiber volume fraction of 8% produced under the same conditions, lack of the reinforcing effect. Two main reasons for the unsatisfactory mechanical properties were identified: First, the fiber-free matrix, which covers the reinforced core, prevents effective load transfer from the matrix to the fibers. And second, the residual stresses in the fiber-free zones are as high as 100 MPa. This causes premature failure in the matrix. From this, it follows that the local reinforcement of an actual part is limited. The stress distribution caused by residual stresses and by loading needs to be known. In this way, the reinforcing phase can be placed and aligned accordingly. Otherwise delamination and premature failure might occur.

  1. The optimal fiber volume fraction and fiber-matrix property compatibility in fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Pan, Ning

    1992-01-01

    Although the question of minimum or critical fiber volume fraction beyond which a composite can then be strengthened due to addition of fibers has been dealt with by several investigators for both continuous and short fiber composites, a study of maximum or optimal fiber volume fraction at which the composite reaches its highest strength has not been reported yet. The present analysis has investigated this issue for short fiber case based on the well-known shear lag (the elastic stress transfer) theory as the first step. Using the relationships obtained, the minimum spacing between fibers is determined upon which the maximum fiber volume fraction can be calculated, depending on the fiber packing forms within the composites. The effects on the value of this maximum fiber volume fraction due to such factors as fiber and matrix properties, fiber aspect ratio and fiber packing forms are discussed. Furthermore, combined with the previous analysis on the minimum fiber volume fraction, this maximum fiber volume fraction can be used to examine the property compatibility of fiber and matrix in forming a composite. This is deemed to be useful for composite design. Finally some examples are provided to illustrate the results.

  2. Development of natural fiber reinforced polylactide-based biocomposites

    NASA Astrophysics Data System (ADS)

    Arias Herrera, Andrea Marcela

    Polylactide or PLA is a biodegradable polymer that can be produced from renewable resources. This aliphatic polyester exhibits good mechanical properties similar to those of polyethylene terephthalate (PET). Since 2003, bio-based high molecular weight PLA is produced on an industrial scale and commercialized under amorphous and semicrystalline grades for various applications. Enhancement of PLA crystallization kinetics is crucial for the competitiveness of this biopolymer as a commodity material able to replace petroleum-based plastics. On the other hand, the combination of natural fibers with polymer matrices made from renewable resources, to produce fully biobased and biodegradable polymer composite materials, has been a strong trend in research activities during the last decade. Nevertheless, the differences related to the chemical structure, clearly observed in the marked hydrophilic/hydrophobic character of the fibers and the thermoplastic matrix, respectively, represent a major drawback for promoting strong fiber/matrix interactions. The aim of the present study was to investigate the intrinsic fiber/matrix interactions of PLAbased natural fiber composites prepared by melt-compounding. Short flax fibers presenting a nominal length of ˜1 mm were selected as reinforcement and biocomposites containing low to moderate fiber loading were processed by melt-mixing. Fiber bundle breakage during processing led to important reductions in length and diameter. The mean aspect ratio was decreased by about 50%. Quiescent crystallization kinetics of PLA and biocomposite systems was examined under isothermal and non-isothermal conditions. The nucleating nature of the flax fibers was demonstrated and PLA crystallization was effectively accelerated as the natural reinforcement content increased. Such improvement was controlled by the temperature at which crystallization took place, the liquid-to-solid transition being thermodynamically promoted by the degree of supercooling

  3. The stress-strain relationships in wood and fiber-reinforced plastic laminae of reinforced glued-laminated wood beams

    NASA Astrophysics Data System (ADS)

    Tingley, Daniel Arthur

    The reinforcement of wood and wood composite structural products to improve their mechanical properties has been in practice for many years. Recently, the use of high-strength fiber-reinforced plastic (FRP) as a reinforcement in such applications has been commercialized. The reinforcement is manufactured using a standard pultrusion process or alternatively a sheet-forming process commonly referred to as "pulforming". The high-modulus fibers are predominately unidirectional, although off-axis fibers are often used to enhance off-axis properties. The fibers used are either of a single type or multiple types, which are called "hybrids". Unidirectional, single, and hybrid fiber FRP physical properties and characteristics were compared to wood. Full-scale reinforced glulams were tested. Aramid-reinforced plastics (ARP) used as tensile reinforcements were found to be superior in strength applications to other types of FRP made with fiber, such as carbon and fiberglass. Carbon/aramid-reinforced plastic (CARP) was shown to be superior in both modulus and strength design situations. Fiberglass was shown to be suitable only in hybrid situations with another fiber such as aramid or carbon and only in limited use situations where modulus was a design criteria. The testing and analysis showed that the global response of reinforced glulam beams is controlled by localized strength variations in the wood such as slope of grain, knots, finger joints, etc. in the tensile zone. The elemental tensile strains in the extreme wood tensile laminae, due to global applied loads, were found to be well below the strain at failure in clear wood samples recovered from the failure area. Two areas affecting the relationship between the wood and the FRP were investigated: compatibility of the wood and FRP materials and interface characteristics between the wood and FRP. The optimum strain value at yield point for an FRP was assessed to be slightly higher than the clear wood value in tension for a

  4. Circular Functions Based Comprehensive Analysis of Plastic Creep Deformations in the Fiber Reinforced Composites

    NASA Astrophysics Data System (ADS)

    Monfared, Vahid

    2016-06-01

    Analytically based model is presented for behavioral analysis of the plastic deformations in the reinforced materials using the circular (trigonometric) functions. The analytical method is proposed to predict creep behavior of the fibrous composites based on basic and constitutive equations under a tensile axial stress. New insight of the work is to predict some important behaviors of the creeping matrix. In the present model, the prediction of the behaviors is simpler than the available methods. Principal creep strain rate behaviors are very noteworthy for designing the fibrous composites in the creeping composites. Analysis of the mentioned parameter behavior in the reinforced materials is necessary to analyze failure, fracture, and fatigue studies in the creep of the short fiber composites. Shuttles, spaceships, turbine blades and discs, and nozzle guide vanes are commonly subjected to the creep effects. Also, predicting the creep behavior is significant to design the optoelectronic and photonic advanced composites with optical fibers. As a result, the uniform behavior with constant gradient is seen in the principal creep strain rate behavior, and also creep rupture may happen at the fiber end. Finally, good agreements are found through comparing the obtained analytical and FEM results.

  5. Fabrication of commercial-scale fiber-reinforced hot-gas filters by chemical vapor deposition

    SciTech Connect

    White, L.R.

    1992-11-01

    Goal was to fabricate a filter for removing particulates from hot gases; principal applications would be in advanced utility processes such as pressurized fluidized bed combustion or coal gasification combined cycle systems. Filters were made in two steps: make a ceramic fiber preform and coat it with SiC by chemical vapor infiltration (CVD). The most promising construction was felt/filament wound. Light, tough ceramic composite filters can be made; reinforcement by continuous fibers is needed to avoid brittleness. Direct metal to filter contact does not damage the top which simplifies installation. However, much of the filter surface of felt/filament wound structures is closed over by the CVD coating, and the surface is rough and subject to delamination. Recommendations are given for improving the filters.

  6. Influence of reinforcement morphology on the mechanical properties of short-fiber composites

    SciTech Connect

    Zhu, Y.T.; Valdez, J.A.; Shi, N.; Lovato, M.L.; Stout, M.G.; Zhou, S.; Blumenthal, W.R.; Lowe, T.C.

    1997-12-01

    A major problem of short-fiber composites is that the interfaces between the fiber and matrix become a limiting factor in improving mechanical properties such as strength. For a short fiber, a strong interface is desired to effectively transfer load from matrix to fiber, thus reducing the ineffective fiber length. However, a strong interface will make it difficult to relieve fiber stress concentration in front of an approaching crack. Stress concentrations result in fiber breakage. The authors report in this paper an innovative approach to overcome this problem: reinforcement morphology design. Short-fibers with enlarged ends are processed and used to reinforce a polyester matrix. The initial results show that the bone-shaped short-fibers produce a composite with significantly higher strength than can be attained with conventional short, straight fibers.

  7. PIP processing, microstructure and properties of Si{sub 3}N{sub 4} fiber and Al{sub 2}O{sub 3} fiber reinforced silicon nitride

    SciTech Connect

    Schwab, S.T.; Page, R.A.; Davidson, D.L.; Graef, R.C.

    1995-10-01

    Polymer infiltration/pyrolysis (PIP) processing has the potential to become an affordable means of manufacturing continuous fiber-reinforced ceramic-matrix components. The PIP method is very similar to the well-known polymer-matrix and carbon-carbon composite manufacturing techniques, the major difference being the use of a preceramic polymer in place of the organic polymer or carbon precursor. To date, the majority of research in the field of preceramic polymers has centered on precursors to silicon carbide (SiC). The Southwest Research institute (SwRI) has focused on the development of polymeric precursors to silicon nitride (Si{sub 3}N{sub 4}) because its high-temperature strength, resistance to oxidation, and other properties make it an attractive candidate for many advanced high-temperature structural applications. PIP Si{sub 3}N{sub 4} composites with NICALON SiC fiber reinforcement have exhibited good fracture toughness (K{sub IC} {approximately} 16 MPa {center_dot} m{sup 1/2}). The authors report here processing, microstructure and preliminary mechanical properties of two new PIP Si{sub 3}N{sub 4} composites. One is reinforced with Tonen Si{sub 3}N{sub 4} fiber (plain weave) while the other is reinforced with ALMAX Al{sub 2}O{sub 3} fiber (8 Harness satin weave).

  8. Structural Evolution of Silicon Oxynitride Fiber Reinforced Boron Nitride Matrix Composite at High Temperatures

    NASA Astrophysics Data System (ADS)

    Zou, Chunrong; Li, Bin; Zhang, Changrui; Wang, Siqing; Xie, Zhengfang; Shao, Changwei

    2016-02-01

    The structural evolution of a silicon oxynitride fiber reinforced boron nitride matrix (Si-N-Of/BN) wave-transparent composite at high temperatures was investigated. When heat treated at 1600 °C, the composite retained a favorable bending strength of 55.3 MPa while partially crystallizing to Si2N2O and h-BN from the as-received amorphous structure. The Si-N-O fibers still performed as effective reinforcements despite the presence of small pores due to fiber decomposition. Upon heat treatment at 1800 °C, the Si-N-O fibers already lost their reinforcing function and rough hollow microstructure formed within the fibers because of the accelerated decomposition. Further heating to 2000 °C led to the complete decomposition of the reinforcing fibers and only h-BN particles survived. The crystallization and decomposition behaviors of the composite at high temperatures are discussed.

  9. Effect of fiber reinforcements on thermo-oxidative stability and mechanical properties of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1991-01-01

    A number of studies have investigated the thermo-oxidative behavior of polymer matrix composites. Two significant observations have been made from these research efforts: (1) fiber reinforcement has a significant effect on composite thermal stability; and (2) geometric effects must be considered when evaluating thermal aging data. A compilation of some results from these studies is presented, and this information shows the influence of the reinforcement fibers on the oxidative degradation of various polymer matrix composites. The polyimide PMR-15 was the matrix material that was used in these studies. The control composite material was reinforced with Celion 6000 graphite fiber. T-40R graphite fibers, along with some very stable ceramic fibers were selected as reinforcing fibers because of their high thermal stability. The ceramic fibers were Nicalon (silicon carbide) and Nextel 312 (alumina-silica-boron oxide). The mechanical properties of the two graphite fiber composites were significantly different, probably owing to variations in interfacial bonding between the fibers and the polyimide matrix. The Celion 6000/PMR-15 bond is very tight but the T-40/PMR-15 bond is less tight. Three oxidation mechanisms were observed: (1) the preferential oxidation of the Celion 6000 fiber ends at cut surfaces, leaving a surface of matrix material with holes where the fiber ends were originally situated; (2) preferential oxidation of the composite matrix; and (3) interfacial degradation by oxidation. The latter two mechanisms were also observed on fiber end cut surfaces. The fiber and interface attacks appeared to initiate interfiber cracking along these surfaces.

  10. Placement protocol for an anterior fiber-reinforced composite restoration.

    PubMed

    Hornbrook, D S

    1997-01-01

    The new classification of metal-free restorative materials provides the clinician with a durable, flexible, and aesthetic laboratory-fabricated alternative to conventional porcelain-fused-to-metal (PFM) full-coverage crowns, inlay and onlay restorations, and single pontic bridges. With exceptional physical and optical characteristics, restorations fabricated utilizing the new ceramic optimized polymer (Ceromer) (Targis, Ivoclar Williams, Amherst, NY) and fiber-reinforced composite (FRC) framework (Vectris, Ivoclar Williams, Amherst, NY) materials can also be utilized predictably in the anterior segment. The success of metal-free restorations can be achieved by following conventional prosthodontic principles for preparation, cementation, and finishing. This article demonstrates the appropriate treatment protocol in order to achieve aesthetically acceptable and durable anterior results utilizing a metal-free restorative system for "Maryland-like" bridge restorations.

  11. Metal-bonded, carbon fiber-reinforced composites

    DOEpatents

    Sastri, Suri A.; Pemsler, J. Paul; Cooke, Richard A.; Litchfield, John K.; Smith, Mark B.

    1996-01-01

    Metal bonded carbon fiber-reinforced composites are disclosed in which the metal and the composite are strongly bound by (1) providing a matrix-depleted zone in the composite of sufficient depth to provide a binding site for the metal to be bonded and then (2) infiltrating the metal into the matrix-free zone to fill a substantial portion of the zone and also provide a surface layer of metal, thereby forming a strong bond between the composite and the metal. The invention also includes the metal-bound composite itself, as well as the provision of a coating over the metal for high-temperature performance or for joining to other such composites or to other substrates.

  12. Metal-bonded, carbon fiber-reinforced composites

    DOEpatents

    Sastri, S.A.; Pemsler, J.P.; Cooke, R.A.; Litchfield, J.K.; Smith, M.B.

    1996-03-05

    Metal bonded carbon fiber-reinforced composites are disclosed in which the metal and the composite are strongly bound by (1) providing a matrix-depleted zone in the composite of sufficient depth to provide a binding site for the metal to be bonded and then (2) infiltrating the metal into the matrix-free zone to fill a substantial portion of the zone and also provide a surface layer of metal, thereby forming a strong bond between the composite and the metal. The invention also includes the metal-bound composite itself, as well as the provision of a coating over the metal for high-temperature performance or for joining to other such composites or to other substrates. 2 figs.

  13. Glass Fiber Reinforced Metal Pressure Vessel Design Guide

    NASA Technical Reports Server (NTRS)

    Landes, R. E.

    1972-01-01

    The Engineering Guide presents curves and general equations for safelife design of lightweight glass fiber reinforced (GFR) metal pressure vessels operating under anticipated Space Shuttle service conditions. The high composite vessel weight efficiency is shown to be relatively insensitive to shape, providing increased flexibility to designers establishing spacecraft configurations. Spheres, oblate speroids, and cylinders constructed of GFR Inconel X-750, 2219-T62 aluminum, and cryoformed 301 stainless steel are covered; design parameters and performance efficiencies for each configuration are compared at ambient and cryogenic temperature for an operating pressure range of 690 to 2760 N/sq cm (1000 to 4000 psi). Design variables are presented as a function of metal shell operating to sizing (proof) stress ratios for use with fracture mechanics data generated under a separate task of this program.

  14. An inelastic constitutive equation of fiber reinforced plastic laminates

    SciTech Connect

    Kanagawa, Y.; Murakami, S.; Mizobe, T.

    1998-01-01

    A constitutive model for describing the time-dependent inelastic deformation of unidirectional and symmetric angle-ply CFRP (carbon Fiber Reinforced Plastics) laminates is developed. The kinematic hardening creep law of Malinin and Khadjinsky and the evolution equation of Armstrong and Frederick are extended to describe the creep deformation of initially anisotropic materials. In particular, the evolution equations of the back stresses of the anisotropic material were formulated by introducing a transformed strain tensor, by which the expression of the equivalent strain rate of the anisotropic material has the identical form as that of the isotropic materials. The resulting model is applied to analyze the time-dependent inelastic deformation of symmetric angle-ply laminates. Comparison between the predictions and the experimental observations shows that the present model can describe well the time-dependent inelastic behavior under different loadings.

  15. Large-aperture active optical carbon fiber reinforced polymer mirror

    NASA Astrophysics Data System (ADS)

    Jungwirth, Matthew E. L.; Wilcox, Christopher C.; Wick, David V.; Baker, Michael S.; Hobart, Clinton G.; Milinazzo, Jared J.; Robichaud, Joseph; Romeo, Robert C.; Martin, Robert N.; Ballesta, Jerome; Lavergne, Emeric; Dereniak, Eustace L.

    2013-05-01

    An active reflective component can change its focal length by physically deforming its reflecting surface. Such elements exist at small apertures, but have yet to be fully realized at larger apertures. This paper presents the design and initial results of a large-aperture active mirror constructed of a composite material called carbon fiber reinforced polymer (CFRP). The active CFRP mirror uses a novel actuation method to change radius of curvature, where actuators press against two annular rings placed on the mirror's back. This method enables the radius of curvature to increase from 2000mm to 2010mm. Closed-loop control maintains good optical performance of 1.05 waves peak-to-valley (with respect to a HeNe laser) when the active CFRP mirror is used in conjunction with a commercial deformable mirror.

  16. The dynamic inelastic behavior in fiber reinforced composite materials

    SciTech Connect

    Haberman, K.S.; Bennett, J.G.; Liu, Cheng

    1997-03-01

    Accurately simulating the complete dynamic behavior, elastic and inelastic, of engineering structures composed of fiber reinforced composite materials can be accomplished by integrating three components: (1) a physically based micromechanical material model that accounts for the experimentally observed mechanisms producing the inelastic behavior; (2) a dynamic three-dimensional continuum simulation capability in which the physically based micromechanical material model is incorporated; and (3) a complete set of robust dynamic experiments. These experiments are used (1) to establish the microstructural mechanisms that produce inelastic behavior and (2) to validate the dynamic simulation capability. This paper focuses on the implementation of a physically based micromechanical material model into an explicit 3D finite element code and shows the experimental comparison.

  17. 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.

  18. Durability Studies on Confined Concrete using Fiber Reinforced Polymer

    NASA Astrophysics Data System (ADS)

    Ponmalar, V.; Gettu, R.

    2014-06-01

    In this study, 24 concrete cylinders with a notch at the centre were prepared. Among them six cylinders were wrapped using single and double layers of fiber reinforced polymer; six cylinders were coated with epoxy resin; the remaining cylinders were used as a control. The cylinders were exposed to wet and dry cycling and acid (3 % H2SO4) solution for the period of 120 days. Two different concrete strengths M30 and M50 were considered for the study. It is found that the strength, ductility and failure mode of wrapped cylinders depend on number of layers and the nature of exposure conditions. It was noticed that the damage due to wet and dry cycling and acid attack was severe in control specimen than the epoxy coated and wrapped cylinders.

  19. Epoxy/carbon composite resins in dentistry: mechanical properties related to fiber reinforcements.

    PubMed

    Viguie, G; Malquarti, G; Vincent, B; Bourgeois, D

    1994-09-01

    Composite carbon/epoxy resin techniques for restorative dentistry have improved with the development of various composite resins classified according to fiber reinforcement, such as short fibers, woven materials, or long unidirectional fibers. This study of the mechanical properties with three-point flexion enabled comparison of the flexural strengths. The modulus of elasticity of different composite resin materials was determined so that the appropriate reinforced composite resin could be selected for specific clinical conditions.

  20. 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.

  1. Affordable Fiber-Reinforced Ceramic Composites Win 1995 R and D 100 Award

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Affordable fiber-reinforced ceramic matrix composites (AFReCC) with high strength and toughness, good thermal conductivity, thermal shock resistance, and oxidation resistance are needed for high-temperature structural applications. AFReCC materials will have various applications in advanced high-efficiency and high-performance engines: that is, the High Speed Civil Transport (HSCT), space propulsion components, and land-based systems. For example, silicon-carbide-fiber-reinforced silicon carbide matrix composites show promise for meeting the criteria of high strength, thermal conductivity, and toughness required for the HSCT combustor liner. AFReCC received R&D Magazine's prestigious R&D 100 Award in 1995. The fabrication process for these composites has three steps. In the first step, fiber preforms are made and chemical vapor infiltration is used to apply the desired interface coating on the fibers. This step also rigidizes the preform. The second step consists of resin infiltration, which after pyrolysis, yields an interconnected network of porous carbon as the matrix. In the final step of the process, the carbon-containing preform is infiltrated with molten silicon or silicon alloys in a furnace. This converts the carbon to silicon carbide leaving as little as 5 percent residual free silicon or refractory disilicide phase. This process is suitable for any type of small-diameter fiber (e.g., carbon, alumina, or silicon carbide) woven into a two- or three-dimensional architecture. This processing approach leads to dense composites where matrix microstructure and composition can be tailored for optimum properties. It has much lower processing cost (less than 50 percent) in comparison to other approaches to fabricating silicon-carbide-based composites. The photograph shows the various AFReCC components. Thermomechanical and thermochemical characterization of these composites under the hostile environments that will be encountered in engine applications is underway.

  2. Microsegregation during Solidification of Graphitic Fiber-Reinforced Aluminum Alloys under External Heat Sinks

    NASA Astrophysics Data System (ADS)

    Seong, H. G.; Lopez, H. F.; Rohatgi, P. K.

    2007-01-01

    Squeeze casting and melt infiltration were employed in processing continuous graphitic fiber-reinforced aluminum matrix composites. The fiber reinforcements were (1) uncoated carbon fiber (UNC-CF), (2) Ni-coated carbon fiber (NiC-CF), and (3) bare graphite fibers (GRFs), and they were externally cooled to enhance the local solidification of the matrix alloy. The solidified microstructures and their composition profiles were examined using optical microscopy, scanning electron microscopy energy-dispersive X-ray, and electron probe microanalysis wavelengh-dispersive X-ray. The resultant microstructures in the UNC-CF and NiC-CF reinforced composites exhibited significant differences from those found in the GRF-reinforced composite, in terms of solidified morphologies and compositions. It was found that coarse columnar dendrites developed in the fiber-free matrix, fine equiaxed dendrites in the chilled matrix, and columnar-like arms in the fiber-reinforced matrices. In contrast, in bare GRF-reinforced composites, two distinct regions were clearly distinguished: (1) a region consisting of coarse equiaxed dendrites in the fiber-free matrix and (2) a featureless morphology within the fiber reinforcement regions. These distinct microstructures were attributed to preferential heat extraction through the GRFs, which possess a relatively high thermal conductivity. Apparently, heat extraction through the GRFs led to the formation of single α-Al envelopes on the fiber surfaces. In addition, the extent of solute segregation found in the GRF-reinforced alloy composite was relatively small when compared with the CF-reinforced alloy composites.

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

    DOEpatents

    Meek, Thomas T.; Blake, Rodger D.

    1987-01-01

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

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

    DOEpatents

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

    1987-09-22

    A fracture-resistant, fiber-reinforced ceramic substrate is produced by a method which involves preparing a ceramic precursor mixture comprising glass material, a coupling agent, and resilient fibers, and then exposing the mixture to microwave energy. The microwave field orients the fibers in the resulting ceramic material in a desired pattern wherein heat later generated in or on the substrate can be dissipated in a desired geometric pattern parallel to the fiber pattern. Additionally, the shunt capacitance of the fracture-resistant, fiber-reinforced ceramic substrate is lower which provides for a quicker transit time for electronic pulses in any conducting pathway etched into the ceramic substrate. 2 figs.

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

    DOEpatents

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

    1985-04-03

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

  6. Carbon Fiber Reinforced Carbon Composite Valve for an Internal Combustion Engine

    NASA Technical Reports Server (NTRS)

    Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor)

    1999-01-01

    A carbon fiber reinforced carbon composite valve for internal combustion engines and the like formed of continuous carbon fibers throughout the valve's stem and head is disclosed. The valve includes braided carbon fiber material over axially aligned unidirectional carbon fibers forming a valve stem; the braided and unidirectional carbon fibers being broomed out at one end of the valve stem forming the shape of the valve head; the valve-shaped structure being densified and rigidized with a matrix of carbon containing discontinuous carbon fibers: and the finished valve being treated to resist oxidation. Also disclosed is a carbon matrix plug containing continuous and discontinuous carbon fibers and forming a net-shape valve head acting as a mandrel over which the unidirectional and braided carbon fibers are formed according to textile processes. Also disclosed are various preform valves and processes for making finished and preform carbon fiber reinforced carbon composite valves.

  7. Oxidation of carbon fiber surfaces for use as reinforcement in high-temperature cementitious material systems

    DOEpatents

    Sugama, Toshifumi.

    1990-05-22

    The interfacial bond characteristics between carbon fiber and a cement matrix, in high temperature fiber-reinforced cementitious composite systems, can be improved by the oxidative treatment of the fiber surfaces. Compositions and the process for producing the compositions are disclosed. 2 figs.

  8. Oxidation of carbon fiber surfaces for use as reinforcement in high-temperature cementitious material systems

    DOEpatents

    Sugama, Toshifumi

    1990-01-01

    The interfacial bond characteristics between carbon fiber and a cement matrix, in high temperature fiber-reinforced cementitious composite systems, can be improved by the oxidative treatment of the fiber surfaces. Compositions and the process for producing the compositions are disclosed.

  9. Morphological, mechanical properties and biodegradability of biocomposite thermoplastic starch and polycaprolactone reinforced with sisal fibers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The incorporation of fibers as reinforcements in polymer composites has increased due to their renewability, low cost and biodegradability. In this study, sisal fibers were added to a polymer matrix of thermoplastic starch and polycaprolactone, both biodegradable polymers. Sisal fibers (5% and 10%) ...

  10. Starch/polycaprolactone-containing composites reinforced with pre-treated sisal fibers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Composites based on thermoplastic cornstarch (TPS) and polycaprolactone (PCL) were reinforced with 5, 10 and 20% (wt%) of pretreated sisal fiber. The impact of the addition of sisal fiber on the mechanical, thermal and morphological properties of composites was investigated. Addition of 5-10% fibers...

  11. Rapid Prototyping of Continuous Fiber Reinforced Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Vaidyanathan, R.; Green, C.; Phillips, T.; Cipriani, R.; Yarlagadda, S.; Gillespie, J.; Effinger, M.; Cooper, K. C.; Gordon, Gail (Technical Monitor)

    2002-01-01

    For ceramics to be used as structural components in high temperature applications, their fracture toughness is improved by embedding continuous ceramic fibers. Ceramic matrix composite (CMC) materials allow increasing the overall operating temperature, raising the temperature safety margins, avoiding the need for cooling, and improving the damping capacity, while reducing the weight at the same time. They also need to be reliable and available in large quantities as well. In this paper, an innovative rapid prototyping technique to fabricate continuous fiber reinforced ceramic matrix composites is described. The process is simple, robust and will be widely applicable to a number of high temperature material systems. This technique was originally developed at the University of Delaware Center for Composite Materials (UD-CCM) for rapid fabrication of polymer matrix composites by a technique called automated tow placement or ATP. The results of mechanical properties and microstructural characterization are presented, together with examples of complex shapes and parts. It is believed that the process will be able to create complex shaped parts at an order of magnitude lower cost than current CVI and PIP processes.

  12. Unsaturated and Saturated Permeabilities of Fiber Reinforcement: Critics and Suggestions

    NASA Astrophysics Data System (ADS)

    Park, Chung Hae; Krawczak, Patricia

    2015-04-01

    In general, permeability measurement results show a strong scattering according to the measurement method, the type of test fluid and the fluid injection condition, even though permeability is regarded as a unique property of porous medium. In particular, the discrepancy between the unsaturated and saturated permeabilities for the same fabric has been widely reported. In the literature, relative permeability has been adopted to model the unsaturated flow. This approach has some limits in the modeling of double-scale porosity medium. We address this issue of permeability measurement by rigorously examining the mass conservation condition. Finally, we identify that the pressure gradient is non-linear with positive curvature in the unsaturated flow and a misinterpretation of pressure gradient is the main reason for the difference between the saturated and unsaturated permeabilities of the same fiber reinforcement. We propose to use a fixed value of permeability and to modify the mass conservation equation if there are air voids which are entrapped inside the fiber tow. Finally, we also suggest some guidelines and future perspectives to obtain more consistent permeability measurement results.

  13. Rapid Prototyping of Continuous Fiber Reinforced Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Vaidyanathan, R.; Green, C.; Phillips, T.; Cipriani, R.; Yarlagadda, S.; Gillespie, J. W., Jr.; Effinger, M.; Cooper, K. C.

    2003-01-01

    For ceramics to be used as structural components in high temperature applications, their fracture toughness is improved by embedding continuous ceramic fibers. Ceramic matrix composite (CMC) materials allow increasing the overall operating temperature, raising the temperature safety margins, avoiding the need for cooling, and improving the damping capacity, while reducing the weight at the same time. They also need to be reliable and available in large quantities as well. In this paper, an innovative rapid prototyping technique to fabricate continuous fiber reinforced ceramic matrix composites is described. The process is simple, robust and will be widely applicable to a number of high temperature material systems. This technique was originally developed at the University of Delaware Center for Composite Materials (UD-CCM) for rapid fabrication of polymer matrix composites by a technique called automated tow placement or ATP. The results of mechanical properties and microstructural characterization are presented, together with examples of complex shapes and parts. It is believed that the process will be able to create complex shaped parts at an order of magnitude lower cost than current chemical vapor infiltration (CVI) and polymer impregnation and pyrolysis (PIP) processes.

  14. Cyclic behavior, development, and characteristics of a ductile hybrid fiber-reinforced polymer (DHFRP) for reinforced concrete members

    NASA Astrophysics Data System (ADS)

    Hampton, Francis Patrick

    Reinforced concrete (R/C) structures especially pavements and bridge decks that constitute vital elements of the infrastructure of all industrialized societies are deteriorating prematurely. Structural repair and upgrading of these structural elements have become a more economical option for constructed facilities especially in the United States and Canada. One method of retrofitting concrete structures is the use of advanced materials. Fiber reinforced polymer (FRP) composite materials typically are in the form of fabric sheets or reinforcing bars. While the strength and stiffness of the FRP is high, composites are inherently brittle, with limited or no ductility. Conventional FRP systems cannot currently meet ductility demand, and therefore, may fail in a catastrophic failure mode. The primary goal of this research was to develop an optimized prototype 10-mm diameter DHFRP bar. The behavior of the bar under full load reversals to failure was investigated. However, this bar first needed to be designed and manufactured in the Fibrous Materials Research at Drexel University. Material properties were determined through testing to categorize the strength properties of the DHFRP. Similitude was used to demonstrate the scaling of properties from the original model bars. The four most important properties of the DHFRP bars are sufficient strength and stiffness, significant ductility for plasticity to develop in the R/C section, and sufficient bond strength for the R/C section to develop its full strength. Once these properties were determined the behavior of reinforced concrete members was investigated. This included the testing of prototype-size beams under monotonic loading and model and prototype beam-columns under reverse cyclic loading. These tests confirmed the large ductility exhibited by the DHFRP. Also the energy absorption capacity of the bar was demonstrated by the hysteretic behavior of the beam-columns. Displacement ductility factors in the range of 3

  15. [Preparation of carbon fiber reinforced fluid type resin denture (author's transl)].

    PubMed

    Kasuga, H; Sato, H; Nakabayashi, N

    1980-01-01

    Transverse strength of cured fluid resins is weaker than that of the heat cured. We have studied to improve the mechanical strength of self-cured acrylic resin by application of carbon fibers as reinforcement and simple methods which must be acceptable for technicians are proposed. A cloth type carbon fiber was the best reinforcement among studied carbon fibers such as chopped or mat. The chopped fibers were difficult to mix homogeneously with fluid resins and effectiveness of the reinforcement was low. Breaking often occurred at the interface between the reinforcement and resin in the cases of mat which gave defects to the test specimens. To prepare reinforced denture, the cloth was trimmed on the master cast after removal of wax and the prepreg was formed with the alginate impression on the cast by Palapress and the cloth. Other steps were same as the usual fluid resin. PMID:6929856

  16. [Preparation of carbon fiber reinforced fluid type resin denture (author's transl)].

    PubMed

    Kasuga, H; Sato, H; Nakabayashi, N

    1980-01-01

    Transverse strength of cured fluid resins is weaker than that of the heat cured. We have studied to improve the mechanical strength of self-cured acrylic resin by application of carbon fibers as reinforcement and simple methods which must be acceptable for technicians are proposed. A cloth type carbon fiber was the best reinforcement among studied carbon fibers such as chopped or mat. The chopped fibers were difficult to mix homogeneously with fluid resins and effectiveness of the reinforcement was low. Breaking often occurred at the interface between the reinforcement and resin in the cases of mat which gave defects to the test specimens. To prepare reinforced denture, the cloth was trimmed on the master cast after removal of wax and the prepreg was formed with the alginate impression on the cast by Palapress and the cloth. Other steps were same as the usual fluid resin.

  17. Evaluating cover depth of steel fiber reinforced concrete using impact-echo testing

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Feng

    2014-04-01

    The purpose of this research is to estimate of the cover depth of steel fiber reinforced concrete using the impact-echo testing. In order to evaluate the security of the construction, usually need to estimate the cover depth of the reinforced concrete. At present, the examination technique of the cover depth of the reinforced concrete without the steel fiber is mainly applied in the magnetic and electrical methods, its rapid detection and good results. But the research of the reactive powder concrete be gradually progress, with the steel fiber concrete structure will be increased, if should still operate the examination with the magnetic and electrical methods, theoretically the steel fiber will have the interference to its electromagnetism field. Therefore, this research designs four kinds of reinforced concrete plate that include different steel fiber contents, to evaluate test results of estimate of the cover depth of the reinforcing bar. The results showed that: estimate of the cover depth of steel fiber reinforced concrete reinforcing bar using the impact-echo testing, the variety of the steel fiber content does not have much influence, the test measurement error within ± 10%, and the most important source of uncertainty is the velocity of concrete.

  18. R&D on glass fiber reinforced epoxy resin composites for superconducting Tokamak.

    PubMed

    Hu, Nannan; Wang, Ke; Ma, Hongming; Pan, Wanjiang; Chen, Qingqing

    2016-01-01

    The glass fiber reinforced epoxy resin composites play an important role in superconducting Tokamak, which are used to insulate the metal components, such as superconducting winding, cooling pipes, metal electrodes and so on. For the components made of metal and glass fiber reinforced epoxy resin composites, thermal shrinkage leads to non-ignorable thermal stress, therefore, much attention should be paid on the thermal shrinkage rate of glass fiber reinforced epoxy resin composites. The structural design of glass fiber reinforced epoxy resin composites should aim at reducing thermal stress. In this paper, the density, glass fiber content and thermal shrinkage rate of five insulation tubes were tested. The testing results will be applied in structural design and mechanical analysis of isolators for superconducting Tokamak. PMID:27652137

  19. Improvement of mechanical properties of acrylic bone cement by fiber reinforcement.

    PubMed

    Saha, S; Pal, S

    1984-01-01

    Acrylic bone cement is significantly weaker and less stiff than compact bone. Bone cement is also weaker in tension than in compression. This limits its use in orthopaedics to areas where tensile stresses are minimum. We have attempted to improve the mechanical properties of PMMA by reinforcing it with metal wires, and graphite and aramid fibers. Normal, carbon fiber reinforced and aramid fiber reinforced bone cement specimens were tested in compression. Addition of a small percentage (1-2% by weight for carbon and up to 6% for aramid) of these fibers improved the mechanical properties significantly. Due to the improved mechanical properties of fiber reinforced bone cement, its clinical use may reduce the incidence of cement fracture and thus loosening of the prosthesis. PMID:6480622

  20. 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.

  1. R&D on glass fiber reinforced epoxy resin composites for superconducting Tokamak.

    PubMed

    Hu, Nannan; Wang, Ke; Ma, Hongming; Pan, Wanjiang; Chen, Qingqing

    2016-01-01

    The glass fiber reinforced epoxy resin composites play an important role in superconducting Tokamak, which are used to insulate the metal components, such as superconducting winding, cooling pipes, metal electrodes and so on. For the components made of metal and glass fiber reinforced epoxy resin composites, thermal shrinkage leads to non-ignorable thermal stress, therefore, much attention should be paid on the thermal shrinkage rate of glass fiber reinforced epoxy resin composites. The structural design of glass fiber reinforced epoxy resin composites should aim at reducing thermal stress. In this paper, the density, glass fiber content and thermal shrinkage rate of five insulation tubes were tested. The testing results will be applied in structural design and mechanical analysis of isolators for superconducting Tokamak.

  2. Mechanical and thermal expansion properties of glass fibers reinforced PEEK composites at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Chu, X. X.; Wu, Z. X.; Huang, R. J.; Zhou, Y.; Li, L. F.

    2010-02-01

    Polyetheretherketone (PEEK) has been widely used as matrix material for high performance composites. In this work, 30% chopped glass fibers reinforced PEEK composites were prepared by injection molding, and then the tensile, flexural and impact properties were tested at different temperatures. The modulus, strength and specific elongation of glass fibers reinforced PEEK at room temperature, 77 K and 20 K have been compared. And the fracture morphologies of different samples were investigated by scanning electron microscopy (SEM). The results showed a dependence of mechanical properties of glass fibers reinforced PEEK composites on temperature. The coefficient of thermal expansion of unfilled PEEK and glass fibers reinforced PEEK were also investigated from 77 K to room temperature. The results indicated that the thermal expansion coefficient (CTE) of PEEK matrix was nearly a constant in this temperature region, and it can be significantly decreased by adding glass fibers.

  3. Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites: Influence of Interface Modification

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Eldridge, Jeffrey I.

    1998-01-01

    Unidirectional celsian matrix composites having 42-45 vol % of uncoated or BN-SIC coated Hi-Nicalon fibers were tested in three-point bend at room temperature. The uncoated fiber-reinforced composites showed catastrophic failure with strength of 210 35 MPa and a flat fracture surface. In contrast, composites reinforced with coated fibers exhibited graceful failure with extensive fiber pullout. Values of first matrix cracking stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01%, respectively, with ultimate strength as high as 960 MPa. The elastic Young modulus of the uncoated and coated fiber-reinforced composites were 184 +/- 4 GPa and 165 +/- 5 GPa, respectively. Fiber push-through tests and microscopic examination indicated no chemical reaction at the uncoated or coated fiber-matrix interface. The low strength of composite with uncoated fibers is due to degradation of the fiber strength from mechanical damage during processing. Because both the coated- and uncoated-fiber-reinforced composites exhibited weak interfaces, the beneficial effect of the BN-SIC dual layer is primarily the protection of fibers from mechanical damage during processing.

  4. Microstructure of AI2O3 fiber-reinforced superalloy (INCONEL 718) composites

    NASA Astrophysics Data System (ADS)

    Nourbakhsh, S.; Sahin, O.; Rhee, W. H.; Margolin, H.

    1996-02-01

    Composites of INCONEL 718 alloy reinforced with either single-crystal (SAPHIKON) or polycrys-talline (Du Pont's FP) A12O3 fiber were fabricated by pressure casting. Optical and transmission electron microscopy were used to characterize the microstructure of the composites and to determine the nature of the fiber/matrix reaction. The widely dispersed fibers in the SAPHIKON-fiber-reinforced composite had no influence on the solidification of the matrix. Six phases, γ-Ni3Al, γ'-Ni3Nb, δ-Ni3Nb, TiC, NbC, and Laves, were present in the matrix of the composite. The last three phases were formed during solidification and the others precipitated during subsequent cooling. The high density of fibers in the FP-fiber-reinforced composite led to a more uniform microstructure within the matrix. Only three phases, γ″-Ni3Nb, NbC, and Laves, were identified. Diffusion of Ti into the A12O3 fiber resulted in preferential grain growth in the FP fiber in areas adjacent to the fiber/matrix interface. The fiber/matrix bond strength in shear in the SAPHIKON-fiber-reinforced composite was in excess of 150 MPa.

  5. Preimpregnated, fiber-reinforced prostheses. Part II. Direct applications: splints and fixed partial dentures.

    PubMed

    Meiers, J C; Duncan, J P; Freilich, M A; Goldberg, A J

    1998-12-01

    This article is the second in a series that describes the development, physical properties, and clinical applications of fiber-reinforced composite materials. The development of fiber-reinforced composite technology has opened new avenues for fabricating direct tooth replacements and splints that are esthetic and simple in design and execution and have the potential for excellent durability. Splinting techniques for hypermobile dentitions or postorthodontic retention and the replacement of anterior and posterior teeth using a groove preparation, a denture tooth, and a fiber-reinforced composite framework will be described.

  6. Al2O3/GdAlO3 fiber for dental porcelain reinforcement.

    PubMed

    Medeiros, Igor S; Luz, Luciana A; Yoshimura, Humberto N; Cesar, Paulo F; Hernandes, Antonio C

    2009-10-01

    The aim of this study was to test the hypothesis that the addition of continuous or milled GdAlO3/Al2O3 fibers to a dental porcelain increases its mechanical properties. Porcelain bars without reinforcement (control) were compared to those reinforced with long fibers (30 vol%). Also, disk specimens reinforced with milled fibers were produced by adding 0 (control), 5 or 10 vol% of particles. The reinforcement with continuous fibers resulted in significant increase in the uniaxial flexural strength from 91.5 to 217.4 MPa. The addition of varied amounts of milled fibers to the porcelain did not significantly affect its biaxial flexural strength compared to the control group. SEM analysis showed that the interface between the continuous fiber and the porcelain was free of defects. On the other hand, it was possible to note the presence of cracks surrounding the milled fiber/porcelain interface. In conclusion, the reinforcement of the porcelain with continuous fibers resulted in an efficient mechanism to increase its mechanical properties; however the addition of milled fibers had no significant effect on the material because the porcelain was not able to wet the ceramic particles during the firing cycle.

  7. Reinforcing and Toughening Effects of Bamboo Pulp Fiber on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Fiber Composites.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/bamboo pulp fiber composites were melt-compounded and injection-molded. Tensile, impact and dynamic mechanical properties of the composites were studied. In contrast to many other short natural fiber reinforced biocomposites which demonstrate decre...

  8. Improving the mechanical performance of wood fiber reinforced bio-based polyurethane foam

    NASA Astrophysics Data System (ADS)

    Chang, Li-Chi

    Because of the environmental impact of fossil fuel consumption, soybean-based polyurethane (PU) foam has been developed as an alternative to be used as the core in structural insulated panels (SIPs). Wood fibers can be added to enhance the resistance of foam against bending and buckling in compression. The goal of this work is to study the effect of three modifications: fiber surface treatment, catalyst choice, and mixing method on the compression performance of wood fiber-reinforced PU foam. Foams were made with a free-rising process. The compression performance of the foams was measured and the foams were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray computed tomography (CT). The foam reinforced with alkali-treated fibers had improved compression performance. The foams made with various catalysts shared similar performance. The foam made using a mechanical stirrer contained well-dispersed fibers but the reinforcing capability of the fibers was reduced.

  9. Novel hybrid columns made of ultra-high performance concrete and fiber reinforced polymers

    NASA Astrophysics Data System (ADS)

    Zohrevand, Pedram

    The application of advanced materials in infrastructure has grown rapidly in recent years mainly because of their potential to ease the construction, extend the service life, and improve the performance of structures. Ultra-high performance concrete (UHPC) is one such material considered as a novel alternative to conventional concrete. The material microstructure in UHPC is optimized to significantly improve its material properties including compressive and tensile strength, modulus of elasticity, durability, and damage tolerance. Fiber-reinforced polymer (FRP) composite is another novel construction material with excellent properties such as high strength-to-weight and stiffness-to-weight ratios and good corrosion resistance. Considering the exceptional properties of UHPC and FRP, many advantages can result from the combined application of these two advanced materials, which is the subject of this research. The confinement behavior of UHPC was studied for the first time in this research. The stress-strain behavior of a series of UHPC-filled fiber-reinforced polymer (FRP) tubes with different fiber types and thicknesses were tested under uniaxial compression. The FRP confinement was shown to significantly enhance both the ultimate strength and strain of UHPC. It was also shown that existing confinement models are incapable of predicting the behavior of FRP-confined UHPC. Therefore, new stress-strain models for FRP-confined UHPC were developed through an analytical study. In the other part of this research, a novel steel-free UHPC-filled FRP tube (UHPCFFT) column system was developed and its cyclic behavior was studied. The proposed steel-free UHPCFFT column showed much higher strength and stiffness, with a reasonable ductility, as compared to its conventional reinforced concrete (RC) counterpart. Using the results of the first phase of column tests, a second series of UHPCFFT columns were made and studied under pseudo-static loading to study the effect of column

  10. Analysis of pultrusion processing for long fiber reinforced thermoplastic composite system

    NASA Technical Reports Server (NTRS)

    Tso, W.; Hou, T. H.; Tiwari, S. N.

    1993-01-01

    Pultrusion is one of the composite processing technology, commonly recognized as a simple and cost-effective means for the manufacturing of fiber-reinforced, resin matrix composite parts with different regular geometries. Previously, because the majority of the pultruded composite parts were made of thermosetting resin matrix, emphasis of the analysis on the process has been on the conservation of energy from various sources, such as heat conduction and the curing kinetics of the resin system. Analysis on the flow aspect of the process was almost absent in the literature for thermosetting process. With the increasing uses of thermoplastic materials, it is desirable to obtain the detailed velocity and pressure profiles inside the pultrusion die. Using a modified Darcy's law for flow through porous media, closed form analytical solutions for the velocity and pressure distributions inside the pultrusion die are obtained for the first time. This enables us to estimate the magnitude of viscous dissipation and it's effects on the pultruded parts. Pulling forces refined in the pultrusion processing are also analyzed. The analytical model derived in this study can be used to advance our knowledge and control of the pultrusion process for fiber reinforced thermoplastic composite parts.

  11. Validation of the numerical model of single-layer composites reinforced with carbon fiber and aramid

    NASA Astrophysics Data System (ADS)

    Sava, Mihaela; Hadǎr, Anton; Pǎrǎuşanu, Ioan; Petrescu, Horia-Alexandru; Baciu, Florin; Marinel, Stǎnescu Marius

    2016-06-01

    In this work we studied the experimental validation of the model and finite element analysis for a single layer of composite materials reinforced with carbon (denoted as C), aramid (K) and carbon-aramid (C-K) fibers. In the literature there are not many details about the differences that arise between transversal and longitudinal characteristics of composite materials reinforced with fabric, compared to those with unidirectional fibers. In order to achieve carbon and aramid composites we used twill fabric and for carbon-aramid plain fabric, as shown in Figure 1. In order to observe the static behavior of the considered specimens, numerical simulations were carried out in addition to the experimental determination of the characteristics of these materials. Layered composites are obviously the most widespread formula for getting advanced composite structures. It allows a unique variety of material and structural combinations leading to optimal design in a wide range of applications [1,2]. To design and verify the material composites it is necessary to know the basic mechanical constants of the materials. Almost all the layered composites consider that the every layer is an orthotropic material, so there are nine independent constants of material corresponding to the three principal directions: Young modulus E1, E2 and E3, shear modulus G12, G23 and G13, and major poison ratios ν12, ν23, ν13. Experimental determinations were performed using traction tests and strain gauges. For each of the three above mentioned materials, five samples were manufactured.

  12. [Tribological properties of carbon fiber-reinforced plastic. Experimental and clinical results].

    PubMed

    Früh, H J; Ascherl, R; Hipp, E

    1997-02-01

    Wear of the articulating components (especially PE-UHMW) of total hip endoprostheses is the most important technical factor limiting the functional lifetime. To minimize wear debris, ceramic heads, according to ISO 6474 (Al2O3), have been used, from 1969 paired with Al2O3 and since 1975 paired with PE-UHMW. Al2O3 balls articulating with cups made from CFRP have been in clinical use since 1988. Laboratory experiments and in-vivo testing showed minimized wear debris and mild biological response to wear products using CFRP (carbon fiber reinforced plastic) instead of PE-UHMW as the cup material. The articulating surfaces of retrieved ceramic heads (Al2O3-Biolox) and cementless CFRP cups (carbon fiber reinforced plastic, Caproman) were compared using sphericity measurement techniques, scanning electron microscopy (SEM) and roughness measurements (including advanced roughness parameters Rvk or Rpk according to ISO 4287). Altogether, the first results of the clinical study showed that the combination Al2O3-ball/CFRP-cup came up to the expected lower wear rates compared with the conventional combinations. The wear rates are comparable with the combination Al2O3/Al2O3 without the material-related problems of ceramic components in all ceramic combinations.

  13. Characterization of carbon fiber reinforced resin composites by the nanoindentation technique

    NASA Astrophysics Data System (ADS)

    Sun, Yuli; Zuo, Dunwen; Cao, Lianjing; Lu, Wenzhuang; Zhu, Yongwei; Li, Jun

    2013-08-01

    The mechanical properties of carbon fiber reinforced resin composites (CFRP) including the epoxy matrix, the carbon fiber and the interface of the carbon fiber/epoxy composites were investigated by means of nanoindentation technique. The hardness, Young's modulus of the components in CFRP were obtained. The results show that the hardness and Young's modulus have a gradient variation from the epoxy matrix to carbon fiber.

  14. Laser cutting of carbon fiber reinforced thermo-plastics (CFRTP) by single-mode fiber laser irradiation

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Kawaguchi, Yoshizo; Sato, Tadatake; Narazaki, Aiko; Kurosaki, Ryozo; Muramatsu, Mayu; Harada, Yoshihisa; Anzai, Kenji; Aoyama, Mitsuaki; Matsushita, Masafumi; Furukawa, Koichi; Nishino, Michiteru; Fujisaki, Akira; Miyato, Taizo; Kayahara, Takashi

    2014-03-01

    We report on the laser cutting of carbon fiber reinforced thermo-plastics (CFRTP) with a cw IR fiber laser (single-mode fiber laser, average power: 350 W). CFRTP is a high strength composite material with a lightweight, and is increasingly being used various applications. A well-defined cutting of CFRTP which were free of debris and thermal-damages around the grooves, were performed by the laser irradiation with a fast beam galvanometer scanning on a multiple-scanpass method.

  15. Effect of fiber reinforcement on thermo-oxidative stability and mechanical properties of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Bowles, K. J.

    1992-01-01

    A number of studies have investigated the thermooxidative behavior of polymer matrix composites. Two significant observations have been made from these research efforts: (1) fiber reinforcement has a significant effect on composite thermal stability; and (2) geometric effects must be considered when evaluating thermal aging data. The polyimide PMR-15 was the matrix material used in these studies. The control composite material was reinforced with Celion 6000 graphite fiber. T-4OR graphite fibers, along with some very stable ceramic fibers were selected as reinforcing fibers because of their high thermal stability. The ceramic fibers were Nicalon (silicon carbide) and Nextel 312 (alumina-silica-boron oxide). The mechanical properties of the two graphite fiber composites were significantly different, probably owing to variations in interfacial bonding between the fibers and the polyimide matrix. Three oxidation mechanisms were observed: (1) the preferential oxidation of the Celion 6000 fiber ends at cut surfaces, leaving a surface of matrix material with holes where the fiber ends were originally situated; (2) preferential oxidation of the composite matrix; and (3) interfacial degradation by oxidation. The latter two mechanisms were also observed on fiber end cut surfaces. The fiber and interface attacks appeared to initiate interfiber cracking along these surfaces.

  16. A New Fiber Preform with Nanocarbon Binder for Manufacturing Carbon Fiber Reinforced Composite by Liquid Molding Process.

    PubMed

    Seong, Dong Gi; Ha, Jong Rok; Lee, Jea Uk; Lee, Wonoh; Kim, Byung Sun

    2015-11-01

    Carbon fiber reinforced composite has been a good candidate of lightweight structural component in the automotive industry. As fast production speed is essential to apply the composite materials for the mass production area such as automotive components, the high speed liquid composite molding processes have been developed. Fast resin injection through the fiber preform by high pressure is required to improve the production speed, but it often results in undesirable deformations of the fiber preform which causes defectives in size and properties of the final composite products. In order to prevent the undesirable deformation and improve the stability of preform shape, polymer type binder materials are used. More stable fiber preform can be obtained by increasing the amount of binder material, but it disturbs the resin impregnation through the fiber preform. In this study, carbon nanomaterials such as graphene oxide were embedded on the surface of carbon fiber by electrophoretic deposition method in order to improve the shape stability of fiber preform and interfacial bonding between polymer and the reinforcing fiber. Effects of the modified reinforcing fiber were investigated in two respects. One is to increase the binding energy between fiber tows, and the other is to increase the interfacial bonding between polymer matrix and fiber surface. The effects were analyzed by measuring the binding force of fiber preform and interlaminar shear strength of the composite. This study also investigated the high speed liquid molding process of the composite materials composed of polymer matrix and the carbon fiber preforms embedded by carbon nanomaterials. Process parameter such as permeability of fiber preform was measured to investigate the effect of nanoscale surface modification on the macroscale processing condition for composite manufacturing. PMID:26726642

  17. A New Fiber Preform with Nanocarbon Binder for Manufacturing Carbon Fiber Reinforced Composite by Liquid Molding Process.

    PubMed

    Seong, Dong Gi; Ha, Jong Rok; Lee, Jea Uk; Lee, Wonoh; Kim, Byung Sun

    2015-11-01

    Carbon fiber reinforced composite has been a good candidate of lightweight structural component in the automotive industry. As fast production speed is essential to apply the composite materials for the mass production area such as automotive components, the high speed liquid composite molding processes have been developed. Fast resin injection through the fiber preform by high pressure is required to improve the production speed, but it often results in undesirable deformations of the fiber preform which causes defectives in size and properties of the final composite products. In order to prevent the undesirable deformation and improve the stability of preform shape, polymer type binder materials are used. More stable fiber preform can be obtained by increasing the amount of binder material, but it disturbs the resin impregnation through the fiber preform. In this study, carbon nanomaterials such as graphene oxide were embedded on the surface of carbon fiber by electrophoretic deposition method in order to improve the shape stability of fiber preform and interfacial bonding between polymer and the reinforcing fiber. Effects of the modified reinforcing fiber were investigated in two respects. One is to increase the binding energy between fiber tows, and the other is to increase the interfacial bonding between polymer matrix and fiber surface. The effects were analyzed by measuring the binding force of fiber preform and interlaminar shear strength of the composite. This study also investigated the high speed liquid molding process of the composite materials composed of polymer matrix and the carbon fiber preforms embedded by carbon nanomaterials. Process parameter such as permeability of fiber preform was measured to investigate the effect of nanoscale surface modification on the macroscale processing condition for composite manufacturing.

  18. Advanced fiber/matrix material systems

    NASA Technical Reports Server (NTRS)

    Hartness, J. Timothy

    1991-01-01

    Work completed in Phase 1 of the NASA Advanced Composite Technology program is discussed. Two towpreg forms (commingled yarns and fused powder towpregs) are being characterized under the program. These towpregs will be used to evaluate textile fabrication technologies for advanced aircraft composite structures. The unique characteristic of both of these material forms is that both fiber and matrix resin are handled in a single operation such as weaving, braiding, or fiber placement. The evaluation of both commingled and fused powder towpreg is described. Various polymer materials are considered for both subsonic and supersonic applications. Polymers initially being evaluated include thermoplastic polyimides such as Larc-TPI and New-TPI, thermoplastics such as PEEK and PEKEKK as well as some toughened crosslinked polyimides. Preliminary mechanical properties as well as tow handling are evaluated.

  19. Energy absorption at high strain rate of glass fiber reinforced mortars

    NASA Astrophysics Data System (ADS)

    Fenu, Luigi; Forni, Daniele; Cadoni, Ezio

    2015-09-01

    In this paper, the dynamic behaviour of cement mortars reinforced with glass fibers was studied. The influence of the addition of glass fibers on energy absorption and tensile strength at high strain-rate was investigated. Static tests in compression, in tension and in bending were first performed. Dynamic tests by means of a Modified Hopkinson Bar were then carried out in order to investigate how glass fibers affected energy absorption and tensile strength at high strain-rate of the fiber reinforced mortar. The Dynamic Increase Factor (DIF) was finally evaluated.

  20. Failure mode interaction in fiber reinforced laminated composites

    NASA Astrophysics Data System (ADS)

    Prabhakar, Pavana

    A novel computational modeling framework to predict the compressive strength of fiber reinforced polymer matrix composite (FRPC) laminates has been presented. The model development has been motivated by a set of experimental results on the compression response of two different FRPCs. The model accounts for failure mode interaction between kink-banding and interface fracture (or delamination), which are observed in the experimental results. To reduce the size of the computational model, those interfaces that are most susceptible to delamination are first determined through a free-edge stress analysis. Furthermore, 0-axis layers, which are passive in the failure process are represented through an equivalent homogenized model, but the microstructural features of the on-axis layers (zero plies) are retained in the computational model. The predictions of the model matched well with the experimental observations, and they were found to accurately account for failure mechanism interactions. Therefore, this model has the potential to replace the need to carry out large numbers of tests to obtain the compressive strength allowable for FRPC laminates, the latter allowable being an essential element in the design of lightweight FRPC aerostructures. Furthermore, the thesis presents a new computational model to predict fiber/matrix splitting failure, a failure mode that is frequently observed in in-plane tensile failure of FRPC's. By considering a single lamina, this failure mechanism was seamlessly modeled through the development of a continuum-decohesive nite element (CDFE). The CDFE was motivated by the variational multiscale cohesive method (VMCM) presented earlier by Rudraraju et al. (2010) at the University of Michigan. In the CDFE, the transition from a continuum to a non-continuum is modeled directly (physically) without resorting to enrichment of the shape functions of the element. Thus, the CDFE is a natural merger between cohesive elements and continuum elements. The

  1. Constitutive modeling of fiber-reinforced cement composites

    NASA Astrophysics Data System (ADS)

    Boulfiza, Mohamed

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

  2. On Healable Polymers and Fiber-Reinforced Composites

    NASA Astrophysics Data System (ADS)

    Nielsen, Christian Eric

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

  3. High-temperature testing of high performance fiber reinforced concrete

    NASA Astrophysics Data System (ADS)

    Fořt, Jan; Vejmelková, Eva; Pavlíková, Milena; Trník, Anton; Čítek, David; Kolísko, Jiří; Černý, Robert; Pavlík, Zbyšek

    2016-06-01

    The effect of high-temperature exposure on properties of High Performance Fiber Reinforced Concrete (HPFRC) is researched in the paper. At first, reference measurements are done on HPFRC samples without high-temperature loading. Then, the HPFRC samples are exposed to the temperatures of 200, 400, 600, 800, and 1000 °C. For the temperature loaded samples, measurement of residual mechanical and basic physical properties is done. Linear thermal expansion coefficient as function of temperature is accessed on the basis of measured thermal strain data. Additionally, simultaneous difference scanning calorimetry (DSC) and thermogravimetry (TG) analysis is performed in order to observe and explain material changes at elevated temperature. It is found that the applied high temperature loading significantly increases material porosity due to the physical, chemical and combined damage of material inner structure, and negatively affects also the mechanical strength. Linear thermal expansion coefficient exhibits significant dependence on temperature and changes of material structure. The obtained data will find use as input material parameters for modelling the damage of HPFRC structures exposed to the fire and high temperature action.

  4. Effect of stress on ultrasonic pulses in fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Hemann, J. H.; Baaklini, G. Y.

    1986-01-01

    An acoustical-ultrasonic technique was used to demonstrate relationships existing between changes in attenuation of stress waves and tensile stress on an eight ply 0 degree graphite-epoxy fiber reinforced composite. All tests were conducted in the linear range of the material for which no mechanical or macroscopic damage was evident. Changes in attenuation were measured as a function of tensile stress in the frequency domain and in the time domain. Stress wave propagation in these specimens was dispersive, i.e., the wave speed depends on frequency. Wave speeds varied from 267,400 cm/sec to 680,000 cm/sec as the frequency of the signal was varied from 150 kHz to 1.9 MHz which strongly suggests that flexural/lamb wave modes of propagation exist. The magnitude of the attenuation changes depended strongly on tensile stress. It was further observed that the wave speeds increased slightly for all tested frequencies as the stress was increased.

  5. Conservative Approach for Restoring Posterior Missing Tooth with Fiber Reinforcement Materials: Four Clinical Reports

    PubMed Central

    Karaarslan, Emine Sirin; Ertas, Ertan; Ozsevik, Semih; Usumez, Aslihan

    2011-01-01

    Adhesively luted, fiber-reinforced, composite-inlay, retained fixed-partial dentures can be a clinical alternative for the replacement of missing posterior teeth in selective situations. This type of restoration allows for satisfactory esthetics and reduced tooth preparation compared to a conventional, fixed-partial denture. This clinical report describes the use of a fiber-reinforced, composite-inlay, retained fixed-partial denture as a conservative alternative for the replacement of missing posterior teeth. PMID:21912503

  6. Smart fiber-reinforced polymer rods featuring improved ductility and health monitoring capabilities

    NASA Astrophysics Data System (ADS)

    Belarbi, Abdeldjelil; Watkins, Steve E.; Chandrashekhara, K.; Corra, Josh; Konz, Bethany

    2001-06-01

    The strain-measuring capability of fiber optic strain gages in fiber-reinforced polymer (FRP) rebars was investigated for failure-inducing loads. Fiber optic interferometric sensors were embedded in a pultruded carbon fiber core and then another layer of carbon fibers were filament wound around the core to form a shell. Pultrusion and filament winding techniques protect the fiber optic strain gages from the concrete environment while providing a secure bond to the core and additional ductility to the overall FRP rebar. Tests of coupon FRP rebar and of FRP-rebar-reinforced concrete beams show that the fiber optic strain gages can read internal strain through failure and can duplicate data from conventional linear variable differential transformers and electrical resistance strain gages. Also, the shell of the FRP rebar inside the concrete beams failed before the rebar core providing pseudo-ductility.

  7. 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.

  8. On Complexities of Impact Simulation of Fiber Reinforced Polymer Composites: A Simplified Modeling Framework

    PubMed Central

    Alemi-Ardakani, M.; Milani, A. S.; Yannacopoulos, S.

    2014-01-01

    Impact modeling of fiber reinforced polymer composites is a complex and challenging task, in particular for practitioners with less experience in advanced coding and user-defined subroutines. Different numerical algorithms have been developed over the past decades for impact modeling of composites, yet a considerable gap often exists between predicted and experimental observations. In this paper, after a review of reported sources of complexities in impact modeling of fiber reinforced polymer composites, two simplified approaches are presented for fast simulation of out-of-plane impact response of these materials considering four main effects: (a) strain rate dependency of the mechanical properties, (b) difference between tensile and flexural bending responses, (c) delamination, and (d) the geometry of fixture (clamping conditions). In the first approach, it is shown that by applying correction factors to the quasistatic material properties, which are often readily available from material datasheets, the role of these four sources in modeling impact response of a given composite may be accounted for. As a result a rough estimation of the dynamic force response of the composite can be attained. To show the application of the approach, a twill woven polypropylene/glass reinforced thermoplastic composite laminate has been tested under 200 J impact energy and was modeled in Abaqus/Explicit via the built-in Hashin damage criteria. X-ray microtomography was used to investigate the presence of delamination inside the impacted sample. Finally, as a second and much simpler modeling approach it is shown that applying only a single correction factor over all material properties at once can still yield a reasonable prediction. Both advantages and limitations of the simplified modeling framework are addressed in the performed case study. PMID:25431787

  9. On complexities of impact simulation of fiber reinforced polymer composites: a simplified modeling framework.

    PubMed

    Alemi-Ardakani, M; Milani, A S; Yannacopoulos, S

    2014-01-01

    Impact modeling of fiber reinforced polymer composites is a complex and challenging task, in particular for practitioners with less experience in advanced coding and user-defined subroutines. Different numerical algorithms have been developed over the past decades for impact modeling of composites, yet a considerable gap often exists between predicted and experimental observations. In this paper, after a review of reported sources of complexities in impact modeling of fiber reinforced polymer composites, two simplified approaches are presented for fast simulation of out-of-plane impact response of these materials considering four main effects: (a) strain rate dependency of the mechanical properties, (b) difference between tensile and flexural bending responses, (c) delamination, and (d) the geometry of fixture (clamping conditions). In the first approach, it is shown that by applying correction factors to the quasistatic material properties, which are often readily available from material datasheets, the role of these four sources in modeling impact response of a given composite may be accounted for. As a result a rough estimation of the dynamic force response of the composite can be attained. To show the application of the approach, a twill woven polypropylene/glass reinforced thermoplastic composite laminate has been tested under 200 J impact energy and was modeled in Abaqus/Explicit via the built-in Hashin damage criteria. X-ray microtomography was used to investigate the presence of delamination inside the impacted sample. Finally, as a second and much simpler modeling approach it is shown that applying only a single correction factor over all material properties at once can still yield a reasonable prediction. Both advantages and limitations of the simplified modeling framework are addressed in the performed case study. PMID:25431787

  10. On complexities of impact simulation of fiber reinforced polymer composites: a simplified modeling framework.

    PubMed

    Alemi-Ardakani, M; Milani, A S; Yannacopoulos, S

    2014-01-01

    Impact modeling of fiber reinforced polymer composites is a complex and challenging task, in particular for practitioners with less experience in advanced coding and user-defined subroutines. Different numerical algorithms have been developed over the past decades for impact modeling of composites, yet a considerable gap often exists between predicted and experimental observations. In this paper, after a review of reported sources of complexities in impact modeling of fiber reinforced polymer composites, two simplified approaches are presented for fast simulation of out-of-plane impact response of these materials considering four main effects: (a) strain rate dependency of the mechanical properties, (b) difference between tensile and flexural bending responses, (c) delamination, and (d) the geometry of fixture (clamping conditions). In the first approach, it is shown that by applying correction factors to the quasistatic material properties, which are often readily available from material datasheets, the role of these four sources in modeling impact response of a given composite may be accounted for. As a result a rough estimation of the dynamic force response of the composite can be attained. To show the application of the approach, a twill woven polypropylene/glass reinforced thermoplastic composite laminate has been tested under 200 J impact energy and was modeled in Abaqus/Explicit via the built-in Hashin damage criteria. X-ray microtomography was used to investigate the presence of delamination inside the impacted sample. Finally, as a second and much simpler modeling approach it is shown that applying only a single correction factor over all material properties at once can still yield a reasonable prediction. Both advantages and limitations of the simplified modeling framework are addressed in the performed case study.

  11. Growth, structure, and optical properties of carbon-reinforced silica fibers

    SciTech Connect

    Zhang, Z. J.; Ajayan, P. M.; Ramanath, G.; Vacik, J.; Xu, Y. H.

    2001-06-11

    We report the synthesis of carbon-reinforced silica fibers by methane exposure of metallocene-treated oxidized-Si(001) substrates at 1100{degree}C. The SiO{sub 2} cap layer transforms into silica fibers reinforced by glassy carbon in the core during methane exposure. High-resolution electron microscopy and spatially resolved spectroscopy measurements of the fibers reveal an amorphous structure without a hollow, and domains of glassy carbon embedded at the fiber core. The carbon-reinforced fibers are optically transparent and have an optical band gap of {approx_equal}3.1 eV. These fibers are organized in radial patterns that vary for different metallocene species. On nickelocene-treated substrates, the fibers originate from the circumference of the circular templates and grow outwards, forming radial patterns. On ferrocene-treated substrates, randomly oriented fibers grow within as well as slightly outside the perimeter of the templates, forming wreath-like patterns. Aligned growth of such fibers could be useful for fabricating optoelectronics devices and reinforced composites. {copyright} 2001 American Institute of Physics.

  12. Effects of EB irradiation on stress-strain curves for carbon fiber reinforced composite materials

    NASA Astrophysics Data System (ADS)

    Kobayashi, H.; Yamada, K.; Mizutani, A.; Uchida, N.; Tanaka, K.; Nishi, Yoshitake

    2004-02-01

    In order to evaluate influence of electron beam (EB) irradiation on elasticity and stress- strain curve of composite materials reinforced by carbon fiber (CF), carbon fiber reinforced polymer (CFRP) and carbon fiber reinforced graphite (C/C) were treated by EB irradiation of 0.3 MGy. Since the EB strengthening was mainly dominated by the ductility enhancements of carbon fiber and matrix of epoxy resin, EB irradiation enlarged fracture stress and enhanced fracture strain of CFRP. Furthermore, EB irradiation slightly enhanced bending elasticity of CFRP and largely enhanced the initial spring constant related to elasticity of C/C coil. Although the elasticity enhancement of carbon fibers did not largely contribute that of CFRP, that of treated graphite matrix in C/C mainly caused the C/C coil elasticity enhancement by EB irradiation. Such a new treatment is a dream-worthy technology for structural materials to be applied in the fields of future engineering.

  13. Effect of hot-dry environment on fiber-reinforced self-compacting concrete

    NASA Astrophysics Data System (ADS)

    Tioua, Tahar; Kriker, Abdelouahed; Salhi, Aimad; Barluenga, Gonzalo

    2016-07-01

    Drying shrinkage can be a major reason for the deterioration of concrete structures. Variation in ambient temperature and relative humidity cause changes in the properties of hardened concrete which can affect their mechanical and drying shrinkage characteristics. The present study investigated mechanical strength and particularly drying shrinkage properties of self-compacting concretes (SCC) reinforced with date palm fiber exposed to hot and dry environment. In this study a total of nine different fibers reinforced self compacting concrete (FRSCC) mixtures and one mixture without fiber were prepared. The volume fraction and the length of fibers reinforcement were 0.1-0.2-0.3% and 10-20-30 mm. It was observed that drying shrinkage lessened with adding low volumetric fraction and short length of fibers in curing condition (T = 20 °C and RH = 50 ± 5 %), but increased in hot and dry environment.

  14. Carbon aerogel composites prepared by ambient drying and using oxidized polyacrylonitrile fibers as reinforcements.

    PubMed

    Feng, Junzong; Zhang, Changrui; Feng, Jian; Jiang, Yonggang; Zhao, Nan

    2011-12-01

    Carbon fiber-reinforced carbon aerogel composites (C/CAs) for thermal insulators were prepared by copyrolysis of resorcinol-formaldehyde (RF) aerogels reinforced by oxidized polyacrylonitrile (PAN) fiber felts. The RF aerogel composites were obtained by impregnating PAN fiber felts with RF sols, then aging, ethanol exchanging, and drying at ambient pressure. Upon carbonization, the PAN fibers shrink with the RF aerogels, thus reducing the difference of shrinkage rates between the fiber reinforcements and the aerogel matrices, and resulting in C/CAs without any obvious cracks. The three point bend strength of the C/CAs is 7.1 ± 1.7 MPa, and the thermal conductivity is 0.328 W m(-1) K(-1) at 300 °C in air. These composites can be used as high-temperature thermal insulators (in inert atmospheres or vacuum) or supports for phase change materials in thermal protection system.

  15. Method of producing a ceramic fiber-reinforced glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P. (Inventor)

    1994-01-01

    A fiber-reinforced composite composed of a BaO-Al2O3-2SiO2 (BAS) glass ceramic matrix is reinforced with CVD silicon carbide continuous fibers. A slurry of BAS glass powders is prepared and celsian seeds are added during ball melting. The slurry is cast into tapes which are cut to the proper size. Continuous CVD-SiC fibers are formed into mats of the desired size. The matrix tapes and the fiber mats are alternately stacked in the proper orientation. This tape-mat stack is warm pressed to produce a 'green' composite. The 'green' composite is then heated to an elevated temperature to burn out organic constituents. The remaining interim material is then hot pressed to form a silicon carbide fiber-reinforced celsian (BAS) glass-ceramic matrix composite which may be machined to size.

  16. Evaluation of a glass-fiber-reinforced, bonded, inlay-supported fixed partial denture--4-year results.

    PubMed

    Jain, Poonam; Cobb, Deborah

    2002-09-01

    Glass-fiber-reinforced composite resin systems may be used as conservative alternatives to conventional fixed partial dentures (FPDs) for the replacement of a single missing tooth. This article describes a clinical technique and 4-year evaluation of an inlay bonded FPD. The patient presented with a missing maxillary right second premolar. A high-caries risk and moderate-to-advanced attachment loss around the abutment teeth, which were clinically stable, were noted. The patient had a strong desire to maintain his remaining dentition. Advantages of supragingival margins and minimal tooth structure removal made the bonded inlay bridge a viable alternative to a conventional FPD for this compromised restorative situation. The clinical performance of this glass-fiber-reinforced resin inlay FPD at the 4-year follow-up is provided. The restoration has served satisfactorily for more than 4 years and holds promise as a conservative, esthetic alternative to the conventional FPD in certain clinical cases.

  17. The recycling of comminuted glass-fiber-reinforced resin from electronic waste.

    PubMed

    Duan, Huabo; Jia, Weifeng; Li, Jinhui

    2010-05-01

    The reuse of comminuted glass-fiber-reinforced resin with various granularities gathered from printed circuit manufacturing residues was investigated. As fillers, these residues were converted into polymeric composite board by an extrusion and injection process using polypropylene as a bonding agent. The mechanical properties of the reproduced composite board were examined by considering the effects of mass fraction and glass-fiber distribution. Interfacial-layer micrograph analysis of the composite material fracture surface was used to study the fiber reinforcement mechanism. Results showed that using comminuted glass-fiber-reinforced resin as a filler material greatly enhanced the performance properties of the composite board. Although the length and diameter of filler varied, these variations had no appreciable effect on the mechanical properties of the processed board. Maximum values of 48.30 MPa for flexural strength, 31.34 MPa for tensile strength, and 31.34 J/m for impact strength were achieved from a composite board containing mass fractions of 30, 10, and 20% glass-fiber-reinforced resin waste, respectively. It was found that the maximum amount of recyclate that could be added to a composite board was 30% of weight. Beyond these percentages, the materials blend became unmanageable and the mixture less amenable to impregnation with fiber. Presented studies indicated that comminuted glass-fiber-reinforced resin waste-filled polypropylene composites are promising candidates for structural applications where high stiffness and fracture resistance are required.

  18. Delamination behavior of carbon fiber/epoxy composite laminates with short fiber reinforcement

    SciTech Connect

    Sohn, M.S.; Hu, X.Z. . Dept. of Mechanical and Materials Engineering)

    1994-06-01

    Delamination in laminated materials is one major mode of damage and failure encountered in application. Fracture mechanics is often used to characterize the interlaminar fracture behavior. The interlaminar fracture energies, G[sub I], G[sub II] and G[sub I/II] are the major concerns to characterize the interlaminar toughness of the composite laminates. Typical mode-I fracture is caused by normal tension, and typical mode-II fracture by shear in the direction of crack extension. The objective of the present study is to compare and discuss the mode-I and mode-II interlaminar fracture energies, G[sub I] and G[sub II] of carbon fiber/epoxy composite laminates with and without the reinforcement of short Kevlar fibers (5--7 mm in length) and to identify the microfracture features of the Kevlar fibers under those two delamination modes through SEM observations. Double cantilever beam (DCB) specimens and end notched flexure (ENF) specimens are used for the mode-I and -II delamination experiments.

  19. Design overview of fiber-reinforced superalloy composites for the Space Shuttle main engine

    NASA Technical Reports Server (NTRS)

    Lewis, J. R.

    1985-01-01

    This preliminary design study evaluated the potential of fiber-reinforced superalloys (FRS) for hot-section components of Space Shuttle Main Engine turbopumps. Emphasis was placed on uncooled turbine blades, with a more limited evaluation of FRS turbine stator vanes. The study included FRS properties evaluation, current structural design capability, and preliminary design and structural analysis. In addition, key technology needs were identified, and a plan was generated to develop operational hardware for advanced versions of the SSME. Based on projections of design properties for FRS composites comprising 50 volume percent of W-4Re-0.38Hf-0.02C wire filaments in a ductile superalloy matrix, it was concluded that FRS turbine blades offer the potential of significant improved operating life and higher temperature capability over the MAR-M-246(Hf) (DS) blades currently used in the SSME.

  20. [The behavior of fiber-reinforced plastics during laser cutting].

    PubMed

    Emmrich, M; Levsen, K; Trasser, F J

    1992-06-01

    The pattern of the organic emissions, which are produced by processing of fibre reinforced plastics (epoxy resins reinforced by aramid and glass fibres and phenol resins reinforced by aramid fibre) with laser beam was studied and the concentrations of the main components determined. Despite the application of plastic materials with different chemical structures, the observed patterns are very similar. Mainly aromatic hydrocarbons are emitted, especially benzene and toluene, as well as some heteroatom-containing aromatic hydrocarbons (e.g. phenol). By use of oxygen as process gas the emissions during cutting of glass fibre reinforced plastics can be reduced, while they will be constantly high with aramid fibre reinforced plastics.

  1. Properties of indirect composites reinforced with monomer-impregnated glass fiber.

    PubMed

    Tanoue, Naomi; Sawase, Takashi; Matsumura, Hideo; McCabe, John F

    2012-07-01

    Sufficient flexural strength is required for long-term clinical use of fixed partial dentures made with fiber-reinforced composite. The flexural strengths of indirect composite materials reinforced with a monomer-preimpregnated glass fiber material were determined to evaluate the compatibility of the composites to glass fiber material. Four types (microhybrid, nanohybrid, microfilled, and minifilled) of indirect composites and a unidirectional long glass fiber material were selected for investigation. The composites were placed on a fiber plate and polymerized in accordance with the respective manufacturer's instructions. Rectangular bar fiber-composite specimens were machined and the flexural strength was calculated. The flexural strength of each indirect composite was also measured. The microfilled composite with the lowest filler content (70 wt%) exhibited the highest increase ratio using the fiber, although its strength without fiber reinforcement was the lowest (62.1 MPa). The fiber-microhybrid specimen demonstrated the highest mean strength (355.9 MPa), although the filler content of the microhybrid composite was comparatively low (73 wt%). The type of composite material should be considered for the selection of an optimal fiber-composite combination. PMID:21932008

  2. Fluorescent protein senses and reports mechanical damage in glass-fiber-reinforced polymer composites.

    PubMed

    Makyła, Katarzyna; Müller, Christoph; Lörcher, Samuel; Winkler, Thomas; Nussbaumer, Martin G; Eder, Michaela; Bruns, Nico

    2013-05-21

    Yellow fluorescent protein (YFP) is used as a mechanoresponsive layer at the fiber/resin interface in glass-fiber-reinforced composites. The protein loses its fluorescence when subjected to mechanical stress. Within the material, it reports interfacial shear debonding and barely visible impact damage by a transition from a fluorescent to a non-fluorescent state. PMID:23423911

  3. A constitutive function for the heat flux in short-fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Herrmann, Heiko

    2015-12-01

    A constitutive function for heat flux in short-fiber-reinforced composites is developed. The fiber orientation distribution is considered using second-order orientation tensor; therefore, the constitutive function for the heat flux will depend on the orientation tensor. The resulting orthotropic equation is discussed also in the context of energy efficiency of buildings.

  4. Fiber reinforced glasses and glass-ceramics for high performance applications

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Brennan, J. J.; Layden, G. K.

    1986-01-01

    The development of fiber reinforced glass and glass-ceramic matrix composites is described. The general concepts involved in composite fabrication and resultant composite properties are given for a broad range of fiber and matrix combinations. It is shown that composite materials can be tailored to achieve high levels of toughness, strength, and elastic stiffness, as well as wear resistance and dimensional stability.

  5. 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.

  6. Comparative study of nanomaterials for interlaminar reinforcement of fiber-composite panels

    NASA Astrophysics Data System (ADS)

    Chiu, Karen Rachel; Duenas, Terrisa; Dzenis, Yuris; Kaser, Jase; Bakis, Charles E.; Roberts, J. Keith; Carter, Daniel

    2013-04-01

    Carbon-fiber reinforced polymer (CFRP) composites offer benefits of reduced weight and increased specific strength; however, these materials can have relatively weak interlaminar toughness. The first modes of composite material failure often remain undetected, since failure is not always visually apparent on the surface of composite materials. In this study, several nano-sized materials and integration approaches are investigated as nanoreinforcement for composite materials. Performance is characterized by the ability of each nanoreinforced composite type to improve Mode I interlaminar toughness. The nanomaterials include 1) commercially available surface-modified silica nanoparticles and 2) continuous polyacrylonitrile (PAN) nanofibers. Test articles are manufactured using hand-layup vacuum bagging and feature either reinforced unidirectional carbon fiber or woven carbon fiber material and one of two investigated epoxy-based resin systems. The nanosilica particles were integrated into the fiber composite structure by mixing with the resin system prior to layup. The PAN nanofibers were produced by an electrospinning process; these fibers were integrated by either collecting the fibers of various areal densities as respective "nanomats" on an interim substrate for subsequent transfer during layup, or directly electrospun onto dry carbon fiber ply surfaces. Test articles were characterized according to ASTM D5528 for finding Mode I strain energy release rates. Results were compared to baseline coupons to determine fracture toughness performance. Results showed that the nanosilica-reinforced coupons increased an average of 35% and 25% in strain energy release rates for the coupons featuring unidirectional fibers and woven fibers, respectively, as compared to the corresponding baseline, whereas the nanomat-reinforced and directly deposited nanofiber-reinforced composites decreased. Low strain energy release rates for the PAN nanofiber-reinforced coupons is attributed

  7. Evaluation of tensile strength of hybrid fiber (jute/gongura) reinforced hybrid polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Venkatachalam, G.; Gautham Shankar, A.; Vijay, Kumar V.; Chandan, Byral R.; Prabaharan, G. P.; Raghav, Dasarath

    2015-07-01

    The polymer matrix composites attract many industrial applications due to its light weight, less cost and easy for manufacturing. In this paper, an attempt is made to prepare and study of the tensile strength of hybrid (two natural) fibers reinforced hybrid (Natural + Synthetic) polymer matrix composites. The samples were prepared with hybrid reinforcement consists of two different fibers such as jute and Gongura and hybrid polymer consists of polyester and cashew nut shell resins. The hybrid composites tensile strength is evaluated to study the influence of various fiber parameters on mechanical strength. The parameters considered here are the duration of fiber treatment, the concentration of alkali in fiber treatment and nature of fiber content in the composites.

  8. Tensile strength and its scatter of unidirectional carbon fiber reinforced composites

    SciTech Connect

    Hamada, H.; Oya, N.; Yamashita, K.; Maekawa, Z.I.

    1995-12-31

    0 (along the fiber direction) and 90 degree (transverse to the fiber direction) tension tests of Carbon Fiber Reinforced Plastics (CFRP) using a great number of specimens were conducted. Tensile properties and their scatter were evaluated by means of the data base. Materials used in this study were seven kinds of carbon fibers and three kinds of epoxy resins. Reinforcing fiber and matrix resin properties strongly affected on 0 and 90 degree properties of CFRP respectively. In 0 degree tension tests, fracture mode of specimen vaned in each material, and a relationship between the scatter of strength and the fracture mode existed. From the results of 9 degree tension tests, some differences of interfacial properties between each laminate were` also detected. According to some considerations on fracture mechanism in 0 degree tension test, it was deduced that the fracture mode depended on the balance of fiber, matrix and interface properties.

  9. A nonlinear biphasic fiber-reinforced porohyperviscoelastic model of articular cartilage incorporating fiber reorientation and dispersion.

    PubMed

    Seifzadeh, A; Wang, J; Oguamanam, D C D; Papini, M

    2011-08-01

    A nonlinear biphasic fiber-reinforced porohyperviscoelastic (BFPHVE) model of articular cartilage incorporating fiber reorientation effects during applied load was used to predict the response of ovine articular cartilage at relatively high strains (20%). The constitutive material parameters were determined using a coupled finite element-optimization algorithm that utilized stress relaxation indentation tests at relatively high strains. The proposed model incorporates the strain-hardening, tension-compression, permeability, and finite deformation nonlinearities that inherently exist in cartilage, and accounts for effects associated with fiber dispersion and reorientation and intrinsic viscoelasticity at relatively high strains. A new optimization cost function was used to overcome problems associated with large peak-to-peak differences between the predicted finite element and experimental loads that were due to the large strain levels utilized in the experiments. The optimized material parameters were found to be insensitive to the initial guesses. Using experimental data from the literature, the model was also able to predict both the lateral displacement and reaction force in unconfined compression, and the reaction force in an indentation test with a single set of material parameters. Finally, it was demonstrated that neglecting the effects of fiber reorientation and dispersion resulted in poorer agreement with experiments than when they were considered. There was an indication that the proposed BFPHVE model, which includes the intrinsic viscoelasticity of the nonfibrillar matrix (proteoglycan), might be used to model the behavior of cartilage up to relatively high strains (20%). The maximum percentage error between the indentation force predicted by the FE model using the optimized material parameters and that measured experimentally was 3%. PMID:21950897

  10. Using Plasma-Activated High Performance Fibers with Nanocrystalline Structure in Producing New Reinforced Composite Materials

    NASA Astrophysics Data System (ADS)

    Kudinov, V.; Korneeva, N.

    2008-08-01

    A wet-pull-out method for investigation of interaction between the high performance polyethylene (HPPE) fiber and polymer matrix is discussed. The paper concerns a cold plasma technique for improving the bond of the HPPE fibers to the matrices and the fibers impregnation with the matrix. Controlled parameters are pull-out force and the height of the matrix capillary lifting along the fiber both in air and in vacuum, in combination with plasma activation of the fibers. The method allows one to estimate the wetting and impregnation of multi-filament fiber with the matrix and simultaneously measure the joint strength. Coupled action of plasma treatment and vacuum impregnation of the fibers improves the joint strength by a factor of 3. Plasma activated HPPE fibers impregnated in air show the value of shear strength τ of 4 Kg/mm2. To understand the effect of treatment initial and plasma-activated fibers were used to fabricate composite materials (CM). The properties and failure modes were compared to those of CM reinforced with untreated fibers. The failure mode of CM reinforced with plasma-activated fibers points to a high strength of the bond between the fibers and the matrix.

  11. Study of fracture mechanisms of short fiber reinforced AS composite by acoustic emission technique

    SciTech Connect

    Kida, Sotoaki; Suzuki, Megumu

    1995-11-01

    The fracture mechanisms of short fiber reinforced AS composites are studied by acoustic emission technique for examining the effects of fiber contents. The loads P{sub b} and P{sub c} which the damage mechanisms change are obtained at the inflection points of the total AE energy curve the energy gradient method. The damages are generated by fiber breaking at the load point of P{sub b} and P{sub c} in B material, and by the fiber breaking and the debonding between resin and fiber at the load points of P{sub b} and P{sub c} in C material.

  12. Research on the melt impregnation of continuous carbon fiber reinforced nylon 66 composites

    NASA Astrophysics Data System (ADS)

    Jia, M. Y.; Li, C. X.; Xue, P.; Chen, K.; Chen, T. H.

    2016-07-01

    Impregnation mold of continuous carbon fiber reinforced thermoplastic composites was designed and built in the article. Based on the theory of fluid mechanics and Darcy's law, a model of the melt impregnation was also established. The influences of fiber bundle width and impregnation pins’ diameter on the impregnation degree were studied by numerical simulation. Continuous carbon fiber reinforced nylon 66 composites were prepared. The effects of coated angle and impregnation mold temperature on the mechanical properties of the composites were also described.The agreement between the experimental data and prediction by the model was found to be satisfactory.

  13. Solid Free-Form Fabrication of Continuous Fiber Reinforced Composites for Propulsion Application

    NASA Technical Reports Server (NTRS)

    Vaidyanathan, R.; Walish, J.; Fox, M.; Rigali, M.; Sutaria, M.; Gillespie, John W., Jr.; Yarlagadda, Shridhar; Effinger, Mike; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    For propulsion related applications, materials must be able to demonstrate excellent ablation and oxidation resistance at temperature approaching 3500 C, adequate load bearing capabilities, non-catastrophic failure modes, and ability to withstand transient thermal shock. A potential list of propulsion-material property requirements includes, low density, high elastic modulus, low thermal-expansion coefficient, high thermal conductivity, excellent erosion and oxidation/corrosion resistance, and flaw-insensitivity. In many cases, they will also need to be able to be joined, survive thermal cycling and multi-axial stress states, and for reusable applications, the materials must maintain the above attributes after prolonged exposure to extremely harsh chemical environments. The final and possibly most important attribute for these materials are the need to be lower cost and readily available in large quantities. Recently, Advanced Ceramics Research, Inc. (ACR) has developed low cost, flexible-manufacturing processes for Zr & Hf-based carbon fiber reinforced composites, materials with good oxidation and ablation resistance up to 3500 C. This process, called Continuous Composite Co-extrusion (C(sup 3)), incorporates carbon fibers to fabricate 'in-situ' carbide and boride-matrix/carbon fiber composites. M is a variation of ACR's manufacturing process for low-cost structural ceramic materials called Fibrous Monoliths with carbon fiber reinforcements. Fibrous Monolithic materials have a distinct fibrous texture, consist of intertwined cells of a primary phase, separated by cell boundaries of a tailored secondary phase and show very high fracture energies, damage tolerance, and graceful failure. Since they are monolithic powder based composites; they can be manufactured by conventional powder processing techniques using inexpensive raw materials. This combination of high performance and low cost is a breakthrough that could enable wider application of ceramics in high

  14. Solid Freeform Fabrication of Continuous Fiber Reinforced Composites for Propulsion Applications

    NASA Technical Reports Server (NTRS)

    Vaidyanathan, R.; Walish, J.; Fox, M.; Rigali, M.; Sutaria, M.; Gillespie, John W., Jr.; Yarlagadda, Shridhar; Effinger, Mike

    2000-01-01

    For propulsion related applications, materials must be able to demonstrate excellent ablation and oxidation resistance at temperature approaching 3500'C, adequate load bearing capabilities, non-catastrophic failure modes, and ability to withstand transient thermal shock. A potential list of propulsion-material property requirements includes, low density, high elastic modulus, low thermal-expansion coefficient, high thermal conductivity, excellent erosion and oxidation/corrosion resistance, and flaw-insensitivity. In many cases, they will also need to be able to be joined, survive thermal cycling and multi-axial stress states, and for reusable applications, the materials must maintain the above attributes after prolonged exposure to extremely harsh chemical environments. The final and possibly most important attribute for these materials are the need to be lower cost and readily available in large quantities. Recently, Advanced Ceramics Research, Inc. (ACR) has developed low cost, flexible- manufacturing processes for Zr & Hf-based carbon fiber reinforced composites, materials with good oxidation and ablation resistance up to 3500 C. This process, called Continuous Composite Co-extrusion (C(sup 3)), incorporates carbon fibers to fabricate 'in-situ' carbide and boride-matrix/carbon fiber composites. This is a variation of ACR's manufacturing process for low-cost structural ceramic materials called Fibrous Monoliths With carbon fiber reinforcements. Fibrous Monolithic materials have a distinct fibrous texture, consist of intertwined cells of a primary phase, separated by cell boundaries of a tailored secondary phase and show very high fracture energies, damage tolerance, and graceful failure. Since they are monolithic powder based composites-, they can be manufactured by conventional powder processing techniques using inexpensive raw materials. This combination of high performance and low cost is a breakthrough that could enable wider application of ceramics in high

  15. Finite element simulation of an artificial intervertebral disk using fiber reinforced laminated composite model.

    PubMed

    Shahmohammadi, Mehrdad; Asgharzadeh Shirazi, Hadi; Karimi, Alireza; Navidbakhsh, Mahdi

    2014-10-01

    Degeneration of intervertebral disk (IVD) has been increased in recent years. The lumbar herniation can be cured using conservative and surgical procedures. Surgery is considered after failure of conservative treatment. Partial discectomy, fusion, and total disk replacement (TDR) are also common surgical treatments for degenerative disk disease. However, due to limitations and disadvantages of the current treatments, many studies have been carried out to approach the best design of mimicking natural disk. Recently, a new method of TDRs has been introduced using nature deformation of IVD by reinforced fibers of annulus fibrosis. Nonetheless, owing to limitations of experimental works on the human body, numerical studies of IVD may help to understand load transfer and biomechanical properties within the disks with reinforced fibers. In this study, a three-dimensional (3D) finite element model of the L2-L3 disk vertebrae unit with 12 vertical fibers embedded into annulus fibrosis was constructed. The IVD was subjected to compressive force, bending moment, and axial torsion. The most important parameters of disk failures were compared to that of experimental data. The results showed that the addition of reinforced fibers into the disk invokes a significant decrease of stress in the nucleus and annulus. The findings of this study may have implications not only for developing IVDs with reinforced fibers but also for the application of fiber reinforced IVD in orthopedics surgeries as a suitable implant. PMID:24981720

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

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

  17. Recycling high-performance carbon fiber reinforced polymer composites using sub-critical and supercritical water

    NASA Astrophysics Data System (ADS)

    Knight, Chase C.

    Carbon fiber reinforced plastics (CFRP) are composite materials that consist of carbon fibers embedded in a polymer matrix, a combination that yields materials with properties exceeding the individual properties of each component. CFRP have several advantages over metals: they offer superior strength to weight ratios and superior resistance to corrosion and chemical attack. These advantages, along with continuing improvement in manufacturing processes, have resulted in rapid growth in the number of CFRP products and applications especially in the aerospace/aviation, wind energy, automotive, and sporting goods industries. Due to theses well-documented benefits and advancements in manufacturing capabilities, CFRP will continue to replace traditional materials of construction throughout several industries. However, some of the same properties that make CFRP outstanding materials also pose a major problem once these materials reach the end of service life. They become difficult to recycle. With composite consumption in North America growing by almost 5 times the rate of the US GDP in 2012, this lack of recyclability is a growing concern. As consumption increases, more waste will inevitably be generated. Current composite recycling technologies include mechanical recycling, thermal processing, and chemical processing. The major challenge of CFRP recycling is the ability to recover materials of high-value and preserve their properties. To this end, the most suitable technology is chemical processing, where the polymer matrix can be broken down and removed from the fiber, with limited damage to the fibers. This can be achieved using high concentration acids, but such a process is undesirable due to the toxicity of such materials. A viable alternative to acid is water in the sub-critical and supercritical region. Under these conditions, the behavior of this abundant and most environmentally friendly solvent resembles that of an organic compound, facilitating the breakdown

  18. The effect of ductile innerlayers on the mechanical performance of fiber-reinforced composite materials

    SciTech Connect

    Hsu, Meng-Bor.

    1990-01-01

    The effects of ductile innerlayers on the mechanical behavior of unidirectional fiber reinforced composites were studied. Two fiber systems were used as the reinforcement; a monofilament system and a roving system. The ductile innerlayer materials were applied on fiber surfaces using coating equipment that was first designed for monofilament coating. For composites reinforced by rovings, problems such as nonuniform fiber distribution and resin starvation in spaces between closely packed filaments arise from the coating process. Even with these problems, improvement in transverse tensile strength, longitudinal compressive strength, flexural fatigue resistance, and fatigue endurance limit were achieved. For monofilament systems, properties such as flexural strength, interlaminar shear strength, and transverse tensile strength are improved by the application of ductile innerlayers. Three mechanisms were shown to be responsible for the improvements: by acting as a spacer and preventing fiber-fiber contact; local ductility is provided near the fiber-matrix interface and lowering stress concentrations; and healing surface flaws in large diameter fiber systems, thus increasing fiber strength.

  19. 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

  20. Strain-rate dependence of the compressive properties of normal and carbon-fiber-reinforced bone cement.

    PubMed

    Saha, S; Pal, S

    1983-11-01

    Normal and carbon-fiber-reinforced (1 wt. %) bone cement samples were tested in compression at various strain rates. Both the compressive strength and proportional limit increased in general with increasing strain rate. Similar strain-rate sensitivity was also shown by the carbon-fiber-reinforced bone cement. The mechanical properties, namely the modulus of elasticity, the proportional limit, and the compressive strength of the carbon-fiber-reinforced bone cement showed highly significant positive correlations with the strain rate. PMID:6654926

  1. Health monitoring of precast bridge deck panels reinforced with glass fiber reinforced polymer bars

    NASA Astrophysics Data System (ADS)

    Ries, James Mcdaniel

    The Beaver Creek Bridge on US highway 6 is the pilot project for Glass Fiber Reinforced Polymer (GFRP) bridge decks and posttensioned bridge decks in the state of Utah. The bridge was built in 2009, using accelerated bridge construction practices, including the use of precast prestressed girders, as well as precast decking. The westbound bridge decking was composed of 12 precast panels each measuring 41'-5" long, 6'-10" wide, and 9¼" thick, and weighing approximately 33 kips. At the time, these panels were the longest GFRP panels in the United States. The Utah Department of Transportation has decided to evaluate GFRP reinforcing bars as an alternative to steel rebar in this bridge deck. The hope is to increase the lifespan of bridge decks to match the service life of the entire bridge. Due to the nature of the GFRP bars, the panels were lifted at four points using straps instead of imbedded anchors. During the four-point lifting, the panels exhibited small deflections and strains; furthermore, no cracks larger than hairline cracks were found in the panels after lifting. The Beaver Creek Bridge deck is the first precast deck in the state of Utah to be posttensioned in the direction of traffic. Posttensioning bridge decks is expected to become the norm in the state of Utah. The posttensioning resulted in increased continuity between panels. In order to quantify the expected performance of the bridge during its service life, a truck load test was performed. The truck load test was comprised of a static and dynamic test. During the truck load test, the bridge experienced deflections in the panels which were 93% below design values. Girder deflections were also small. The use of GFRP bars has the potential to extend the life of bridge decks exposed to deicing salts from 45 years to 100 years, while only requiring an increased capital cost in the bridge of 8%. Furthermore, the use of GFRP bars in conjunction with accelerated building practices has the potential to

  2. Provisional anterior tooth replacement using nonimpregnated fiber and fiber-reinforced composite resin materials: a clinical report.

    PubMed

    Chan, Daniel C N; Giannini, Marcelo; De Goes, Mario Fernando

    2006-05-01

    The loss of anterior teeth is often a serious esthetic concern. While conventional fixed partial dentures and implant-supported restorations may be the treatments of choice, nonimpregnated fibers (NFs) and fiber-reinforced composite (FRC) resins offer a conservative alternative for improving esthetics. This article describes 2 clinical situations in which NF glass ribbon and FRC were successfully used to provisionally restore anterior edentulous areas in an esthetic, functional, and timely manner. PMID:16679128

  3. Provisional anterior tooth replacement using nonimpregnated fiber and fiber-reinforced composite resin materials: a clinical report.

    PubMed

    Chan, Daniel C N; Giannini, Marcelo; De Goes, Mario Fernando

    2006-05-01

    The loss of anterior teeth is often a serious esthetic concern. While conventional fixed partial dentures and implant-supported restorations may be the treatments of choice, nonimpregnated fibers (NFs) and fiber-reinforced composite (FRC) resins offer a conservative alternative for improving esthetics. This article describes 2 clinical situations in which NF glass ribbon and FRC were successfully used to provisionally restore anterior edentulous areas in an esthetic, functional, and timely manner.

  4. A new constitutive theory for fiber-reinforced incompressible nonlinearly elastic solids

    NASA Astrophysics Data System (ADS)

    Horgan, Cornelius O.; Saccomandi, Giuseppe

    2005-09-01

    We consider an incompressible nonlinearly elastic material in which a matrix is reinforced by strong fibers, for example fibers of nylon or carbon aligned in one family of curves in a rubber matrix. Rather than adopting the constraint of fiber inextensibility as has been previously assumed in the literature, here we develop a theory of fiber-reinforced materials based on the less restrictive idea of limiting fiber extensibility. The motivation for such an approach is provided by recent research on limiting chain extensibility models for rubber. Thus the basic idea of the present paper is simple: we adapt the limiting chain extensibility concept to limiting fiber extensibility so that the usual inextensibility constraint traditionally used is replaced by a unilateral constraint. We use a strain-energy density composed with two terms, the first being associated with the isotropic matrix or base material and the second reflecting the transversely isotropic character of the material due to the uniaxial reinforcement introduced by the fibers. We consider a base neo-Hookean model plus a special term that takes into account the limiting extensibility in the fiber direction. Thus our model introduces an additional parameter, namely that associated with limiting extensibility in the fiber direction, over previously investigated models. The aim of this paper is to investigate the mathematical and mechanical feasibility of this new model and to examine the role played by the extensibility parameter. We examine the response of the proposed models in some basic homogeneous deformations and compare this response to those of standard models for fiber reinforced rubber materials. The role of the strain-stiffening of the fibers in the new models is examined. The enhanced stability of the new models is then illustrated by investigation of cavitation instabilities. One of the motivations for the work is to apply the model to the biomechanics of soft tissues and the potential merits

  5. CO disintegration of stainless steel fiber-reinforced refractory castables

    SciTech Connect

    Martin, C.; Brown, J.J. Jr.

    1986-07-01

    The effects of stainless steel fiber additions on the resistance of refractory castables to CO and steam were investigated. A series of high and intermediate alumina calcium aluminate-bonded castables was prepared containing several commercial stainless steel fibers. Compressive strength and abrasion resistance of the castables following exposure to high pressure carbon monoxide and steam at 500/sup 0/C were comparable to those of samples without stainless steel fibers. The addition of stainless steel fibers to refractory castables did not change the CO resistance of the castables unless they were fired in air before CO exposure. Airfiring creates oxide layer so the fibers which ultimately causes castable disintegration.

  6. Screening of matrices and fibers for reinforced thermoplastics intended for dental applications.

    PubMed

    Goldberg, A J; Burstone, C J; Hadjinikolaou, I; Jancar, J

    1994-02-01

    Plastics reinforced with continuous fibers (FRC) are being developed for dental applications, such as prosthodontic frameworks and orthodontic retainers. Flexure properties, stress relaxation and hydrolytic stability of FRC based on six thermoplastic matrices, three types of fibers, and three fiber volume fractions were evaluated. Samples with clinically relevant dimensions were tested. Polycarbonate was the preferred matrix material. Polycarbonate reinforced with 42 volume percent glass fibers exhibited the highest combination of flexure modulus (17.9 +/- 2.6 GPa), flexure strength (426 +/- 40 MPa), reinforcing efficiency (0.79), and resistance to stress relaxation. No statistically significant difference was observed between E and S2 glass reinforced composites under the experimental conditions used. Kevlar reinforced materials exhibited a low flexure modulus and strength. The apparent flexure moduli of all composites decreased with span length in the range of clinical interest. Generally, the prevalent mode of failure for all FRC investigated was brittle failure under flexure loading. Relatively large sample-to-sample variation in both composition and properties indicated that improved fabrication methods will be needed in future studies. The combination of good flexure properties, formability, and translucency suggests that novel appliance designs for dentistry are feasible with FRC, but further studies of its properties and particularly the effects of fiber/matrix interfacial quality are needed.

  7. Microstructural effects on the dynamic fracture toughness of cellulose-fiber-reinforced polypropylene

    NASA Astrophysics Data System (ADS)

    Clemons, Craig Merrill

    Natural fiber reinforced thermoplastics are a rapidly growing, commercially interesting area. Unlike their glass reinforced counterparts, microstructure and dynamic fracture behavior of natural fiber reinforced thermoplastics have hardly been investigated. We characterized the microstructure of cellulose fiber reinforced polypropylene and determined its effect on dynamic fracture toughness. Scanning electron microscopy of the fracture surfaces and x-ray diffraction were used to investigate fiber orientation in injection molded composites. The polypropylene matrix was removed by solvent extraction, and the lengths of the residual fibers were optically determined. Fiber lengths were reduced by one-half when compounded in a high-intensity thermokinetic mixer and then injection molded. At low fiber contents, there was little fiber orientation; at high fiber contents, a layered structure arose exhibiting differing fiber orientations through the thickness of the injection molded specimen. Scanning electron microscopy of acid etched specimens revealed spherulitic structure emanating from cellulose fibers (i.e. transcrystallinity) in injection molded composites containing less than 5% fibers. The etching procedure failed to provide any matrix surface relief in high fiber content composites. To better understand fracture under impact loading, dynamic fracture analysis was performed based on linear elastic fracture mechanics. Dynamic critical energy release rates and dynamic critical stress intensity factors were deduced from instrumented Charpy impact test measurements. Dynamic fracture toughness increased with cellulose content and with orientation of fibers perpendicular to the crack plane. To better control composite microstructure, model laminates of highly aligned plies were produced and tested. Dynamic fracture toughness decreased with fiber alignment angle. A simple model successfully related the microstructure to the dynamic fracture toughness. Increasing test

  8. In Vitro Evaluation of Veneering Composites and Fibers on the Color of Fiber-Reinforced Composite Restorations

    PubMed Central

    Hasani Tabatabaei, Masoomeh; Hasani, Zahra; Ahmadi, Elham

    2014-01-01

    Objective: Color match between fiber-reinforced composite (FRC) restorations and teeth is an imperative factor in esthetic dentistry. The purpose of this study is to evaluate the influence of veneering composites and fibers on the color change of FRC restorations. Materials and Methods: Glass and polyethylene fibers were used to reinforce a direct microhybrid composite (Z250, 3M ESPE) and a microfilled composite (Gradia Indirect, GC). There were eight experimental groups (n=5 disks per group). Four groups were used as the controls (non-FRC control) and the others were used as experimental groups. CIELAB parameters (L*, a* and b*) of specimens were evaluated against a white background using a spectrophotometer to assess the color change. The color difference (ΔE*) and color coordinates were (L*, a* and b*) analyzed by two-way ANOVA and Tukey’s test. Results: Both types of composite and fiber influenced the color parameters (ΔL*, Δa*). The incorporation of fibers into the composite in the experimental groups made them darker than the control groups, except in the Gradia Indirect+ glass fibers group. Δb* is affected by types of fibers only in direct fiber reinforced composite. No statistically significant differences were recognized in ΔE* among the groups (p>0.05). Conclusion: The findings of the present study suggest that the tested FRC restorations exhibited no difference in color in comparison with non-FRC restoration. Hence, the types of veneering composites and fibers did not influence the color change (ΔE*) of FRC restorations. PMID:25584060

  9. Fiber reinforced concrete: Characterization of flexural toughness and some studies on fiber-matrix bond-slip interaction

    NASA Astrophysics Data System (ADS)

    Dubey, Ashish

    One major problem associated with the testing of fiber reinforced concrete specimens under flexural loading is that the measured post-cracking response is severely affected by the stiffness of the testing machine. As a consequence, misleading results are obtained when such a flexural response is used for the characterization of composite toughness. An assessment of a new toughness characterization technique termed the Residual Strength Test Method (RSTM) has been made. In this technique, a stable narrow crack is first created in the specimen by applying a flexural load in parallel with a steel plate under controlled conditions. The plate is then removed, and the specimen is tested in a routine manner in flexure to obtain the post-crack load versus displacement response. Flexural response for a variety of fiber reinforced cementitious composites obtained using the Residual Strength Test Method has been found to correlate very well with those obtained with relatively stiffer test configurations such as closed-loop test machines. The Residual Strength Test Method is found to be effective in differentiating between different fiber types, fiber lengths, fiber configurations, fiber volume fractions, fiber geometries and fiber moduli. In particular, the technique has been found to be extremely useful for testing cement-based composites containing fibers at very low dosages (<0.5% by volume). An analytical model based on shear lag theory is introduced to study the problem of fiber pullout in fiber reinforced composites. The proposed model eliminates limitations of many earlier models and captures essential features of pullout process, including progressive interfacial debonding, Poisson's effect, and variation in interfacial properties during the fiber pullout process. Interfacial debonding is modeled using an interfacial shear strength criterion. Influence of normal contact stress at the fiber-matrix interface is considered using shrink-fit theory, and the interfacial

  10. Innovative Composites Through Reinforcement Morphology Design - a Bone-Shaped-Short-Fiber Composite

    SciTech Connect

    Zhu, Y.T.; Valdez, J.A.; Beyerlain, I.J.; Stout, M.G.; Zhou, S.; Shi, N.; Lowe, T.C.

    1999-06-29

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objective of this project is to improve the strength and toughness of conventional short-fiber composites by using innovative bone-shaped-short (BSS) fibers as reinforcement. We fabricated a model polyethylene BSS fiber-reinforced polyester-matrix composite to prove that fiber morphology, instead of interfacial strength, solves the problem. Experimental tensile and fracture toughness test results show that BSS fibers can bridge matrix cracks more effectively, and consume many times more energy when pulled out, than conventional-straight-short (CSS) fibers. This leads to both higher strength and fracture toughness for the BSS-fiber composites. A computational model was developed to simulate crack propagation in both BSS- and CSS-fiber composites, accounting for stress concentrations, interface debonding, and fiber pullout. Model predictions were validated by experimental results and will be useful in optimizing BSS-fiber morphology and other material system parameters.

  11. Manufacturing and Mechanical Testing of a New Functionally Graded Fiber Reinforced Cement Composite

    SciTech Connect

    Shen Bin; Hubler, Mija; Paulino, Glaucio H.; Struble, Leslie J.

    2008-02-15

    A functionally graded (FG) material system is employed to make fiber use more efficient in a fiber reinforced cement composite (FRCC). This preliminary study demonstrates beam elements that were functionally graded fiber reinforced cement composite (FGFRCC) with four layers, each with a different fiber volume ratio. Fiber volume ratio was graded in accordance with its potential contribution to the mechanical load-bearing capacity so as to reduce the overall fiber volume ratio while preserving the flexural strength and ductility of the beam. Extrusion was used to produce single homogeneous layers of constant fiber volume ratio. The FRCC layers with different fiber volume ratios were stacked according to a desired configuration and then pressed to make an integrated FGFRCC. Flexural tests were carried out to characterize the mechanical behavior, and the results were analyzed to evaluate the effectiveness of the designed fiber distribution. Compared with homogeneous FRCC with the same overall fiber volume fraction, the FGFRCC exhibited about 50% higher strength and comparable ductility.

  12. Evaluation of post-fire strength of concrete flexural members reinforced with glass fiber reinforced polymer (GFRP) bars

    NASA Astrophysics Data System (ADS)

    Ellis, Devon S.

    Owing to their corrosion resistance and superior strength to weight ratio, there has been, over the past two decades, increased interest in the use of fiber-reinforced polymer (FRP) reinforcing bars in reinforced concrete structural members. The mechanical behavior of FRP reinforcement differs from that of steel reinforcement. For example, FRP reinforcement exhibit a linear stress-strain behavior until the bar ruptures and the strength, stiffness and bond properties of FRP reinforcement are affected more adversely by elevated temperatures. All structures are subject to the risk of damage by fire and fires continue to be a significant cause of damage to structures. Many structures do not collapse after being exposed to fire. The safety of the structure for any future use is dependent on the ability to accurately estimate the post-fire load capacity of the structure. Assuming that the changes, due to fire exposure, in the mechanical behavior of the GFRP reinforcing bar and concrete, and the bond between the reinforcing bar and the concrete are understood, an analytical procedure for estimating the post-fire strength of GFRP reinforced concrete flexural elements can be developed. This thesis investigates the changes in: a) tensile properties and bond of GFRP bars; and b) the flexural behavior of GFRP reinforced concrete beams flexural after being exposed to elevated temperatures up to 400°C and cooled to ambient temperature. To this end, twelve tensile tests, twelve pullout bond tests and ten four-point beam tests were performed. The data from the tests were used to formulate analytical procedures for evaluating the post-fire strength of GFRP reinforced concrete beams. The procedure produced conservative results when compared with the experimental data. In general, the residual tensile strength and modulus of elasticity of GFRP bars decrease as the exposure temperature increases. The loss in properties is however, smaller than that observed by other researchers when

  13. TECHNIQUES AND RESULTS FOR FIBER LENGTH DISTRIBUTION DETERMINATION AS A FUNCTION OF THICKNESS IN LONG FIBER REINFORCED INJECTION MOLDED THERMOPLASTICS

    SciTech Connect

    Kunc, Vlastimil; Frame, Barbara J; Pryor, Jeff M; Nguyen, Ba N.; TuckerIII, Charles L.; Case, Scott; Penumadu, Dayakar; Guffey, Eric W

    2008-01-01

    A novel measurement technique was developed to obtain unbiased fiber length distribution (FLD) measurements at specified locations in the thickness of the sample. This technique relies on elastic energy stored in long fiber thermoplastics (LFT), which is released during partially constrained burn-off. This release results in an increase of thickness dimension of the sample and partial disentanglement, allowing sample selection and subsequent filament separation. Quantitative FLD results and the measurement technique are discussed in detail. The FLD in long fiber reinforced injection molded thermoplastics is shown to vary as a function of thickness.

  14. Electron processing of fibre-reinforced advanced composites

    NASA Astrophysics Data System (ADS)

    Singh, Ajit; Saunders, Chris B.; Barnard, John W.; Lopata, Vince J.; Kremers, Walter; McDougall, Tom E.; Chung, Minda; Tateishi, Miyoko

    1996-08-01

    Advanced composites, such as carbon-fibre-reinforced epoxies, are used in the aircraft, aerospace, sporting goods, and transportation industries. Though thermal curing is the dominant industrial process for advanced composites, electron curing of similar composites containing acrylated epoxy matrices has been demonstrated by our work. The main attraction of electron processing technology over thermal technology is the advantages it offers which include ambient temperature curing, reduced curing times, reduced volatile emissions, better material handling, and reduced costs. Electron curing technology allows for the curing of many types of products, such as complex shaped, those containing different types of fibres, and up to 15 cm thick. Our work has been done principally with the AECL's 10 MeV, 1 kW electron accelerator; we have also done some comparative work with an AECL Gammacell 220. In this paper we briefly review our work on the various aspects of electron curing of advanced composites and their properties.

  15. 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.

  16. Processing and properties of multiscale cellular thermoplastic fiber reinforced composite (CellFRC)

    NASA Astrophysics Data System (ADS)

    Sorrentino, L.; Cafiero, L.; D'Auria, M.; Iannace, S.

    2015-12-01

    High performance fiber reinforced polymer composites are made by embedding high strength/modulus fibers in a polymeric matrix. They are a class of materials that owe its success to the impressive specific mechanical properties with respect to metals. In many weight-sensitive applications, where high mechanical properties and low mass are required, properties per unit of mass are more important than absolute properties and further weight reduction is desirable. A route to reach this goal could be the controlled induction of porosity into the polymeric matrix, while still ensuring load transfer to the reinforcing fibers and fiber protection from the environment. Cellular lightweight fiber reinforced composites (CellFRC) were prepared embedding gas bubbles of controlled size within a high performance thermoplastic matrix reinforced with continuous fibers. Pores were induced after the composite was first saturated with CO2 and then foamed by using an in situ foaming/shaping technology based on compression moulding with adjustable mould cavities. The presence of micro- or submicro-sized cells in the new CellFRC reduced the apparent density of the structure and led to significant improvements of its impact properties. Both structural and functional performances were further improved through the use of a platelet-like nanofiller (Expanded Graphite) dispersed into the matrix.

  17. Effect of surface modification on carbon fiber and its reinforced phenolic matrix composite

    NASA Astrophysics Data System (ADS)

    Yuan, Hua; Wang, Chengguo; Zhang, Shan; Lin, Xue

    2012-10-01

    In this work, polyacrylonitrile (PAN)-based carbon fiber were chemically modified with H2SO4, KClO3 and silane coupling agent (γ-aminopropyltriethoxysilane, APS), and carbon fiber reinforced phenolic matrix composites were prepared. The structural and surface characteristics of the carbon fiber were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), laser Raman scattering (LRS) and Fourier transform infrared spectroscopy (FTIR). Single fiber mechanical properties, specific surface area, composite impact properties and interfacial shear strength (ILSS) were researched to indicate the effects of surface modification on fibers and the interaction between modified fiber surface and phenolic matrix. The results showed that carbon fiber surface modification by oxidation and APS can strengthen fiber surface chemical activity and enlarge the fiber surface area as well as its roughness. When carbon fiber (CF) is oxidized treatment, the oxygen content as well as the O/C ratio will be obviously increased. Oxygen functional groups increase with oxidation time increasing. Carbon fiber treated with APS will make Csbnd Osbnd R content increase and Osbnd Cdbnd O content decrease due to surface reaction. Proper treatment of carbon fiber with acid and silane coupling agent prove an effective way to increase the interfacial adhesion and improve the mechanical and outdoor performance of the resulting fiber/resin composites.

  18. Investigation of failure modes in fiber-reinforced ceramic-matrix composites. Master's thesis

    SciTech Connect

    Moschler, J.W.

    1988-12-01

    This experimental study was conducted to investigate the damage progression in fiber-reinforced ceramic-matrix composites under tensile loading. As part of this study, the effect of the residual stresses at the fiber-matrix interface on damage progression was evaluated. Composite samples were fabricated from silicon carbide fibers and borosilicate glass matrices. Each glass had a different coefficient of thermal expansion than the fiber and through the variation of this mismatch, the residual stresses at the fiber-matrix interface were varied resulting in different bonding conditions at the fiber-matrix interface. The mechanical properties of the composites were measured using a servo-hydraulic mechanical testing machine. During these tests, transverse strain reversal was observed that is believed to be caused by axial matrix cracks and fiber-matrix debonding. Tensile tests were conducted on the composites using a constant-load straining device in which damage progression was observed using an optical microscope.

  19. Influence of veneering composite composition on the efficacy of fiber-reinforced restorations (FRR).

    PubMed

    Ellakwa, A; Shortall, A; Shehata, M; Marquis, P

    2001-01-01

    This study investigated the influence of fiber reinforcement on the flexural properties of four commercial (Artglass, Belleglass HP, Herculite XRV and Solidex) veneering composites (Series A) and two experimental composites (Series B&C). This study investigated how the composition of the veneering composites influenced the enhancement of strength and modulus produced by fiber reinforcement. The formulation of the experimental composites were varied by changing the filler load (Series B) or the resin matrix chemistry (Series C) to assess the effect these changes would have on the degree of reinforcement. In Series A, the commercial veneering composites were reinforced by an Ultra-High-Molecular-Weight Polyethylene fiber (UHMW-PE/Connect) to evaluate flexural properties after 24 hours and six months. In Series B, experimental composites with the same organic matrix but with different filler loads (40% to 80% by weight) were also reinforced by Connect fiber to evaluate flexural properties. In Series C, experimental composites (Systems 1-4) with the same filler load (76.5% by weight) but with different organic matrix compositions were reinforced by Connect fiber to evaluate flexural properties. For Series B and C, flexural properties were evaluated after 24 hours water storage. All the samples were prepared in a mold 2 mm x 2 mm x 25 mm and stored in distilled water at 37 degrees C until they were ready for flexural testing in an Instron Universal Testing Machine using a crosshead speed of 1 mm/minute. The results showed no significant differences in the flexural strength (FS) between any of the commercial reinforced composites in Series A. The flexural modulus (FM) of the fiber-reinforced Belleglass HP group was significantly higher than for Artglass and Solidex. Water storage for six months had no significant (p>0.05) effect on the flexural strength of three of the four reinforced veneering composites. The flexural strength for Artglass was significantly reduced (p<0

  20. Reinforcement of a self-setting calcium phosphate cement with different fibers.

    PubMed

    Xu, H H; Eichmiller, F C; Giuseppetti, A A

    2000-10-01

    A water-based calcium phosphate cement (CPC) has been used in a number of medical and dental procedures due to its excellent osteoconductivity and bone replacement capability. However, the low tensile strength of CPC prohibits its use in many unsupported defects and stress-bearing locations. Little investigation has been carried out on the fiber reinforcement of CPC. The aims of the present study, therefore, were to examine whether fibers would strengthen CPC, and to investigate the effects of fiber type, fiber length, and volume fraction. Four different fibers were used: aramid, carbon, E-glass, and polyglactin. Fiber length ranged from 3-200 mm, and fiber volume fraction ranged from 1.9-9.5%. The fibers were mixed with CPC paste and placed into molds of 3 x 4 x 25 mm. A flexural test was used to fracture the set specimens and to measure the ultimate strength, work-of-fracture, and elastic modulus. Scanning electron microscopy was used to examine specimen fracture surfaces. Fiber type had significant effects on composite properties. The composite ultimate strength in MPa (mean +/- SD; n = 6) was (62+/-16) for aramid, (59+/-11) for carbon, (29+/-8) for E-glass, and (24+/-4) for polyglactin, with 5.7% volume fraction and 75 mm fiber length. In comparison, the strength of unreinforced CPC was (13+/-3). Fiber length also played an important role. For composites containing 5.7% aramid fibers, the ultimate strength was (24+/-3) for 3 mm fibers, (36+/-13) for 8 mm fibers, (48 +/-14) for 25 mm fibers, and (62+/-16) for 75 mm fibers. At 25 mm fiber length, the ultimate strength of CPC composite was found to be linearly proportional to fiber strength. In conclusion, a self-setting calcium phosphate cement was substantially strengthened via fiber reinforcement. Fiber length, fiber volume fraction, and fiber strength were found to be key microstructural parameters that controlled the mechanical properties of CPC composites.

  1. Experimental evaluation and simulation of volumetric shrinkage and warpage on polymeric composite reinforced with short natural fibers

    NASA Astrophysics Data System (ADS)

    Santos, Jonnathan D.; Fajardo, Jorge I.; Cuji, Alvaro R.; García, Jaime A.; Garzón, Luis E.; López, Luis M.

    2015-09-01

    A polymeric natural fiber-reinforced composite is developed by extrusion and injection molding process. The shrinkage and warpage of high-density polyethylene reinforced with short natural fibers of Guadua angustifolia Kunth are analyzed by experimental measurements and computer simulations. Autodesk Moldflow® and Solid Works® are employed to simulate both volumetric shrinkage and warpage of injected parts at different configurations: 0 wt.%, 20 wt.%, 30 wt.% and 40 wt.% reinforcing on shrinkage and warpage behavior of polymer composite. Become evident the restrictive effect of reinforcing on the volumetric shrinkage and warpage of injected parts. The results indicate that volumetric shrinkage of natural composite is reduced up to 58% with fiber increasing, whereas the warpage shows a reduction form 79% to 86% with major fiber content. These results suggest that it is a highly beneficial use of natural fibers to improve the assembly properties of polymeric natural fiber-reinforced composites.

  2. Reinforcing effects of different fibers on denture base resin based on the fiber type, concentration, and combination.

    PubMed

    Yu, Sang-Hui; Lee, Yoon; Oh, Seunghan; Cho, Hye-Won; Oda, Yutaka; Bae, Ji-Myung

    2012-01-01

    The aim of this study was to evaluate the reinforcing effects of three types of fibers at various concentrations and in different combinations on flexural properties of denture base resin. Glass (GL), polyaromatic polyamide (PA) and ultra-high molecular weight polyethylene (PE) fibers were added to heat-polymerized denture base resin with volume concentrations of 2.6%, 5.3%, and 7.9%, respectively. In addition, hybrid fiber-reinforced composite (FRC) combined with either two or three types of fibers were fabricated. The flexural strength, modulus and toughness of each group were measured with a universal testing machine at a crosshead speed of 5 mm/min. In the single fiber-reinforced composite groups, the 5.3% GL and 7.9% GL had the highest flexural strength and modulus; 5.3% PE was had the highest toughness. Hybrid FRC such as GL/PE, which showed the highest toughness and the flexural strength, was considered to be useful in preventing denture fractures clinically. PMID:23207213

  3. Fiber release from impacted graphite reinforced epoxy composites

    NASA Technical Reports Server (NTRS)

    Babinsky, T. C.

    1980-01-01

    Carbon fibers released from composites by aircraft fires and crashes can cause electrical shorts and consequent equipment damage. This report investigates less vigorous release mechanisms than that previously simulated by explosive burn/blast tests. When AS/3501-6 composites are impacted by various head and weight configurations of a pendulum impactor, less than 0.2 percent by weight of the original sample is released as single fibers. Other fiber release mechanisms studied were air blasts, constant airflow, torsion, flexural, and vibration of composite samples. The full significance of the low single fiber release rates found here is to be evaluated by NASA in their aircraft vulnerability studies.

  4. Electromagnetic Field of Surface Waves Propagation in Fiber-Reinforced Generalized Thermoelastic Medium

    NASA Astrophysics Data System (ADS)

    Lotfy, Kh.; Salem, Al. M.; Al-Sayed, A.

    2015-05-01

    The objective of this paper is to investigate the surface waves in fiber-reinforced anisotropic elastic medium subjected to magnetic and thermal fields. We introduce the coupled theory (CD), Lord-Shulman (LS) theory and Green-Lindsay (GL) theory to study the influence of magnetic field on 2D problem of a fiber-reinforced thermoelastic. The analytical expressions for displacement components and force stress are obtained in the physical domain by using the harmonic vibrations. The wave velocity equations have been obtained in different cases. Numerical results for the temperature, displacement, and thermal stress components are given and illustrated graphically in the presence and absence of the magnetic field of the material medium. A comparison is also made between the three theories in the case of presence and absence of fiber-reinforced parameters.

  5. 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.

  6. Comparison of denture base resin reinforced with polyaromatic polyamide fibers of different orientations.

    PubMed

    Yu, Sang-Hui; Ahn, Dae-Hyung; Park, Ji-Su; Chung, Yong Sik; Han, In-Sik; Lim, Jung-Seop; Oh, Seunghan; Oda, Yutaka; Bae, Ji-Myung

    2013-01-01

    The aim of this study was to evaluate the effect of reinforcing polyaromatic polyamide (aramid) fibers with various orientations on the flexural properties of denture base resin. Aramid fibers with four orientations of unidirectional, woven, non-woven and paper-type were pre-impregnated and placed at the bottom of a specimen mold. Heat-polymerized denture base resin was packed over the fibers and polymerized. A three-point bending test was performed using a universal testing machine at a crosshead speed of 5 mm/min. The flexural strengths and flexural moduli of the unidirectional and woven groups were significantly higher than those of the control and other experimental groups.For the flexural moduli, all experimental groups showed significantly higher reinforcing effects than the control group. In conclusion, the unidirectional group located perpendicular to the direction of the load was most effective in reinforcing the denture base resin, followed by the woven group. PMID:23538771

  7. Comparison of denture base resin reinforced with polyaromatic polyamide fibers of different orientations.

    PubMed

    Yu, Sang-Hui; Ahn, Dae-Hyung; Park, Ji-Su; Chung, Yong Sik; Han, In-Sik; Lim, Jung-Seop; Oh, Seunghan; Oda, Yutaka; Bae, Ji-Myung

    2013-01-01

    The aim of this study was to evaluate the effect of reinforcing polyaromatic polyamide (aramid) fibers with various orientations on the flexural properties of denture base resin. Aramid fibers with four orientations of unidirectional, woven, non-woven and paper-type were pre-impregnated and placed at the bottom of a specimen mold. Heat-polymerized denture base resin was packed over the fibers and polymerized. A three-point bending test was performed using a universal testing machine at a crosshead speed of 5 mm/min. The flexural strengths and flexural moduli of the unidirectional and woven groups were significantly higher than those of the control and other experimental groups.For the flexural moduli, all experimental groups showed significantly higher reinforcing effects than the control group. In conclusion, the unidirectional group located perpendicular to the direction of the load was most effective in reinforcing the denture base resin, followed by the woven group.

  8. Processing and damage recovery of intrinsic self-healing glass fiber reinforced composites

    NASA Astrophysics Data System (ADS)

    Sordo, Federica; Michaud, Véronique

    2016-08-01

    Glass fiber reinforced composites with a self-healing, supramolecular hybrid network matrix were produced using a modified vacuum assisted resin infusion moulding process adapted to high temperature processing. The quality and fiber volume fraction (50%) of the obtained materials were assessed through microscopy and matrix burn-off methods. The thermo-mechanical properties were quantified by means of dynamic mechanical analysis, revealing very high damping properties compared to traditional epoxy-based glass fiber reinforced composites. Self-healing properties were assessed by three-point bending tests. A high recovery of the flexural properties, around 72% for the elastic modulus and 65% of the maximum flexural stress, was achieved after a resting period of 24 h at room temperature. Recovery after low velocity impact events was also visually observed. Applications for this intrinsic and autonomic self-healing highly reinforced composite material point towards semi-structural applications where high damping and/or integrity recovery after impact are required.

  9. Clinical evaluation of carbon fiber reinforced carbon endodontic post, glass fiber reinforced post with cast post and core: A one year comparative clinical study

    PubMed Central

    Preethi, GA; Kala, M

    2008-01-01

    Aim: Restoring endodontically treated teeth is one of the major treatments provided by the dental practitioner. Selection and proper use of restorative materials continues to be a source of frustration for many clinicians. There is controversy surrounding the most suitable choice of restorative material and the placement method that will result in the highest probability of successful treatment. This clinical study compares two different varieties of fiber posts and one cast post and core in terms of mobility of crown margin under finger pressure, recurrent caries detected at the crown margin, fracture of the restoration, fracture of the root and periapical and periodontal pathology requiring crown removal over the period of 12months as evaluated by clinical and radiographical examination. Materials and Methods: 30 root canal treated, single rooted maxillary anterior teeth of 25 patients in the age range of 18–60 years where a post retained crown was indicated were selected for the study between January 2007 and August 2007; and prepared in a standard clinical manner. It was divided into 3 groups of 10 teeth in each group. After post space preparation, the Carbon fiber and Glass fiber reinforced posts were cemented with Scotch bond multipurpose plus bonding agent and RelyX adhesive resin cement in the first and second groups respectively. The Cast post and cores were cemented with Zinc Phosphate cement in the third group. Following post- cementation, the preparation was further refined and a rubber base impression was taken for metal-ceramic crowns which was cemented with Zinc Phosphate cement. A baseline periapical radiograph was taken once each crown was cemented. All patients were evaluated after one week (baseline), 3 months, 6 months and one year for following characteristics mobility of crown margin under finger pressure, recurrent caries detected at the crown margin, fracture of the restoration, fracture of the root and periapical and periodontal pathology

  10. Influence of the curing cycles on the fatigue performance of unidirectional glass fiber reinforced epoxy composites

    NASA Astrophysics Data System (ADS)

    Hüther, Jonas; Brøndsted, Povl

    2016-07-01

    During the manufacturing process of fiber reinforced polymers the curing reaction of the resin results in shrinkage of the resin and introduces internal stresses in the composites. When curing at higher temperatures in order to shorten up the processing time, higher curing stresses and thermal stresses are built up and frozen, as residual stresses occur. In the present work, a glass fiber reinforced epoxy composite laminate with an unidirectional architecture based on non-crimp fabrics with backing fibers is investigated. Three different curing cycles (time-temperature cycles) are used, leading to different levels of internal stresses. The mechanical properties, static strength and fatigue life time, are measured in three different directions of the material, i.e. the fiber direction, 0°, the 30° off axis direction, and the 90° direction transverse to the fiber direction. It is experimentally demonstrated that the resulting residual stresses barely influences the quasi-static mechanical properties of reinforced glass-fiber composites. It is found that the fatigue performance in the 0° direction is significantly influenced by the internal stresses, whereas the fatigue performance in the off axes directions so is not significantly influenced of these stresses. This is related to the observations that the damage mechanisms in the off axes directions are mainly related to shear failure in the matrix and in the interface between fiber and matrix and different from the damage mechanisms in the fiber direction, where the damage initiates in the transverse backing fibers and is directly related to fiber fractures in the load-carrying axial fiber bundles.

  11. Mechanical properties and shape memory effect of short fiber reinforced SMP composite

    NASA Astrophysics Data System (ADS)

    Yu, Kai; Lv, Haibao; Yi, Guo; Liu, Yanju; Leng, Jinsong

    2010-04-01

    By adding randomly distributed short fiber into a shape memory polymer (SMP) matrix, both the mechanical properties and the shape memory behavior are improved significantly, overcoming some traditional defects of SMP composite reinforced by long fiber and particles. In this paper, the short fiber reinforced SMP composite are developed for the improvement of the mechanical and thermal properties of styrene-based SMP bulk. The specimens with different chopped fiber weight fractions are prepared, and then their mechanical behavior and electrical properties are investigated. As a result, the resistance against mechanical and thermal mechanical loads in the developed materials increases due to the role of reinforcement fiber. For the conducting composite filled with short carbon fiber, not only the actuation of SMP composite can be driven by low voltage, but also its tensile, bending strength, glass transition temperature, storage modulus and thermal conductivity increase by a factor of filler content of carbon fiber increasing. The results show meaningful guidance for further design and the performance evaluation of such composite materials.

  12. Plane Waves of a Fiber-Reinforcement Magneto-thermoelastic Comparison of Three Different Theories

    NASA Astrophysics Data System (ADS)

    Othman, Mohamed I. A.; Said, Samia M.

    2013-02-01

    In this article, the coupled theory, Lord-Shulman theory, and Green-Lindsay (GL) theory are used to study the influence of a magnetic field on a fiber-reinforced thermoelastic half-space. Normal mode analysis is used to solve a thermal shock problem. Numerical results for the temperature, displacement components, and stress components are given and illustrated graphically. A comparison is made between the coupled and GL theories in the absence and presence of a magnetic field and reinforcement.

  13. Reinforcement of conventional glass-ionomer restorative material with short glass fibers.

    PubMed

    Hammouda, Ibrahim M

    2009-01-01

    This study investigated the strengthening effect of glass fibers when added to conventional glass-ionomer restorative material. Glass fibers were incorporated into glass-ionomer powder in 3 wt% and 5 wt%. The fibers used had 1 mm length and 10 microm thickness. These criteria of fiber length, diameter, and concentration represent a new approach for reinforcing conventional glass-ionomer [Medifill, conventional restorative glass-ionomer]. The mechanical properties tested were diametral tensile strength, hardness, flexural strength, flexural modulus and fracture toughness after 24-h and 7-days of storage in deionized water. Glass short fibers were mixed thoroughly into the glass-ionomer powder before mixing with the cement liquid. Samples of specific dimensions were prepared for each time interval and fiber loading according to the manufacturer's instructions and international standards. Hardness was measured using a micro-hardness tester at 100 gram applied load for 15 s. The other mechanical properties were measured using a Lloyd universal testing machine. The results showed increased diametral tensile strength, flexural strength, flexural modulus, and fracture toughness by the addition of glass fibers. There was an appreciable increase of the tested mechanical properties of glass-ionomer restorative material as a result of increasing fiber loading and water storage for 1 week. It was concluded that conventional glass-ionomer can be reinforced by the addition of short glass fibers.

  14. Mussel-inspired catecholamine polymers as new sizing agents for fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Lee, Wonoh; Lee, Jea Uk; Byun, Joon-Hyung

    2015-04-01

    Mussel-inspired catecholamine polymers (polydopamine and polynorepinephrine) were coated on the surface of carbon and glass fibers in order to increase the interfacial shear strength between fibers and polymer matrix, and consequently the interlaminar shear strength of fiber-reinforced composites. By utilizing adhesive characteristic of the catecholamine polymer, fiber-reinforced composites can become mechanically stronger than conventional composites. Since the catecholamine polymer is easily constructed on the surface by the simultaneous polymerization of its monomer under a weak basic circumstance, it can be readily coated on micro-fibers by a simple dipping process without any complex chemical treatments. Also, catecholamines can increase the surface free energy of micro-fibers and therefore, can give better wettability to epoxy resin. Therefore, catecholamine polymers can be used as versatile and effective surface modifiers for both carbon and glass fibers. Here, catecholamine-coated carbon and glass fibers exhibited higher interfacial shear strength (37 and 27% increases, respectively) and their plain woven composites showed improved interlaminar shear strength (13 and 9% increases, respectively) compared to non-coated fibers and composites.

  15. Kenaf-glass fiber reinforced unsaturated polyester hybrid composites: Tensile properties

    NASA Astrophysics Data System (ADS)

    Zhafer, S. F.; Rozyanty, A. R.; Shahnaz, S. B. S.; Musa, L.; Zuliahani, A.

    2016-07-01

    The use of natural fibers in composite is rising in recent years due their lightweight, non-abrasive, combustible, non-toxic, low cost and biodegradable properties. However, in comparison with synthetic fibers, the mechanical properties of natural fibers are lower. Therefore, the inclusion of synthetic fibers could improve the mechanical performance of natural fiber based composites. In this study, kenaf bast fiber and glass fiber at different weight percentage loading were used as reinforcement to produce hybrid composites. Unsaturated polyester (UP) resin was used as matrix and hand lay-up process was performed to apply the UP resin on the hybrid kenaf bast/glass fiber composite. Effect of different fiber loading on tensile strength, tensile modulus and elongation at break of the hybrid composite was studied. It has been found that the highest value of tensile strength and modulus was achieved at 10 wt.% kenaf/10 wt.% glass fiber loading. It was concluded that addition of glass fiber has improved the tensile properties of kenaf bast fiber based UP composites.

  16. Continuous unidirectional fiber reinforced composites: Fabrication and testing

    NASA Technical Reports Server (NTRS)

    Weber, M. D.; Spiegel, F. X.; West, Harvey A.

    1994-01-01

    The study of the anisotropic mechanical properties of an inexpensively fabricated composite with continuous unidirectional fibers and a clear matrix was investigated. A method has been developed to fabricate these composites with aluminum fibers and a polymer matrix. These composites clearly demonstrate the properties of unidirectional composites and cost less than five dollars each to fabricate.

  17. Bonded ceramic foams reinforced with fibers for high temperature use

    NASA Technical Reports Server (NTRS)

    Mcdonald, G.; Hendricks, R. C.; Mullen, R. L.

    1992-01-01

    High quality SiC ceramic foams, which have only recently become available, have for the first time made possible the construction of low density ceramic fiber-ceramic foam sandwiches for high temperature applications. This report describes the construction of some ceramic fiber-ceramic foam structures and the preliminary measurement of strength at elevated temperature.

  18. Electrospun polyacrylonitrile nanocomposite fibers reinforced with iron nitrate nanoparticles

    NASA Astrophysics Data System (ADS)

    Mohammed, Asif

    The methodology of preparing pure Polyacrylonitrile (PAN) fibers and magnetic PAN/FeNO3 composite Nanofibers is the traditional electrospinning process where fibers of diameter ranging less than 100 nm and larger lengths can be sophisticatedly produced on laboratory bench. With varying properties of polymer concentration, voltage and other parameters pure PAN fibers and those loaded with FeNO3 are produced. Analysis of those prepared fibers has been done through a series of experiments like SEM, FITR and X-ray Diffraction. SEM analysis explains the formation of fibers and leads to the selection of best possible ones for future methods of rheological and TGA analysis. In the past where similar contributions have been done for the fibers with FeO and Fe3O4 and the Nanoparticles, the same mentioned procedure replaces them with FeNO3. On the whole, uniform bead-less fibers are obtained and their behaviors' are studied as well. Also, graphical information for correlating the size of fibers and their polymer concentrations has been obtained. TGA analysis for recording their stability under different thermal conditions is reported. Anilining methods using microwave equipment are done instead of conventional ones.

  19. Behavior of fiber reinforced sandy slopes under seepage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seepage flow is a major contributor to instability of natural hill slopes, river banks and engineered embankments. In order to increase the factor of safety, an emerging technology involves the inclusion of synthetic fibers in the soil. The addition of tension resisting fibers has a favorable effec...

  20. Tribological study of non-asbestos fiber reinforced phenolic composites for braking applications

    SciTech Connect

    Gopal, P.; Dharani, L.R.; Blum, F.D.

    1994-12-31

    A cashew modified phenolic resin was used as the binder to prepare several different nonasbestos fiber reinforced composite friction materials. Friction-wear tests were conducted at various loads, speeds and temperatures on a Chase friction testing machine. The fade and wear characteristics of glass and carbon fiber reinforced friction materials were studied. The wear rates of hybrid composites containing Kevlar{reg_sign} (registered trademark of E.I. duPont de Nemours) pulp were compared to those of control composites without Kevlar{reg_sign} pulp.

  1. The Effect of Mechanical Force on Generalized Thermoelasticity in a Fiber-Reinforcement Under Three Theories

    NASA Astrophysics Data System (ADS)

    Othman, Mohamed I. A.; Said, Samia M.

    2012-06-01

    The present paper is concerned with effect of mechanical force on generalized thermoelasticity in a fiber-reinforcement. The formulation is applied to generalized thermoelasticity based on the coupled theory, Lord-Shulman theory, and Green-Lindsay theory. The analytical expression of the displacement components, stresses, and temperature are obtained in the physical domain and illustrated graphically using normal mode analysis. Comparisons are made among the three theories for the field quantities in the absence and in the presence of a fiber-reinforcement as well as for different values of mechanical force.

  2. Tooth splinting with fiber-reinforced composite materials: achieving predictable aesthetics.

    PubMed

    Rappelli, Giorgio; Putignano, Angelo

    2002-08-01

    The need to respond to the ever-increasing patient demand for aesthetics, tissue maintenance, and cost efficiency has resulted in the evolution of techniques and materials that allow predictable restoration of teeth that would otherwise be compromised. The development of synthetic dental materials has allowed the incorporation of fiber-reinforced materials to replace metal splints. These contemporary materials provide increased flexural strength, as well as improved aesthetics, to the restoration. This article describes a conservative tooth splinting procedure using polyethylene fibers as reinforcement for both direct and indirect restorations.

  3. NDE of Fiber Reinforced Foam Composite Structures for Future Aerospace Vehicles

    NASA Technical Reports Server (NTRS)

    Walker, james; Roth, Don; Hopkins, Dale

    2010-01-01

    This slide presentation reviews the complexities of non-destructive evaluation (NDE) of fiber reinforced foam composite structures to be used for aerospace vehicles in the future.Various views of fiber reinforced foam materials are shown and described. Conventional methods of NDE for composites are reviewed such as Micro-computed X-Ray Tomography, Thermography, Shearography, and Phased Array Ultrasonics (PAUT). These meth0ods appear to work well on the face sheet and face sheet ot core bond, they do not provide adequate coverage for the webs. There is a need for additional methods that will examine the webs and web to foam core bond.

  4. Behavior of Concrete Panels Reinforced with Synthetic Fibers, Mild Steel, and GFRP Composites Subjected to Blasts

    SciTech Connect

    C. P. Pantelides; T. T. Garfield; W. D. Richins; T. K. Larson; J. E. Blakeley

    2012-03-01

    The paper presents experimental data generated for calibrating finite element models to predict the performance of reinforced concrete panels with a wide range of construction details under blast loading. The specimens were 1.2 m square panels constructed using Normal Weight Concrete (NWC) or Fiber Reinforced Concrete (FRC). FRC consisted of macro-synthetic fibers dispersed in NWC. Five types of panels were tested: NWC panels with steel bars; FRC panels without additional reinforcement; FRC panels with steel bars; NWC panels with glass fiber reinforced polymer (GFRP) bars; and NWC panels reinforced with steel bars and external GFRP laminates on both faces. Each panel type was constructed with three thicknesses: 152 mm, 254 mm, and 356 mm. FRC panels with steel bars had the best performance for new construction. NWC panels reinforced with steel bars and external GFRP laminates on both faces had the best performance for strengthening or rehabilitation of existing structures. The performance of NWC panels with GFRP bars was strongly influenced by the bar spacing. The behavior of the panels is classified in terms of damage using immediate occupancy, life safety, and near collapse performance levels. Preliminary dynamic simulations are compared to the experimental results.

  5. Effects of Temperature, Oxidation and Fiber Preforms on Fatigue Life of Carbon Fiber-Reinforced Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2016-08-01

    In this paper, the effects of temperature, oxidation and fiber preforms on the fatigue life of carbon fiber-reinforced silicon carbide ceramic-matrix composites (C/SiC CMCs) have been investigated. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface wear model and fibers statistical failure model at room temperature, and interface/fibers oxidation model, interface wear model and fibers statistical failure model at elevated temperatures in the oxidative environments. When the broken fibers fraction approaches to the critical value, the composites fatigue fracture. The fatigue life S-N curves and fatigue limits of unidirectional, cross-ply, 2D, 2.5D and 3D C/SiC composites at room temperature, 800 °C in air, 1100, 1300 and 1500 °C in vacuum conditions have been predicted.

  6. Mechanical properties of glass fiber-reinforced endodontic posts.

    PubMed

    Cheleux, Nicolas; Sharrock, Patrick J

    2009-10-01

    Five types of posts from three different manufacturers (RTD, France, Carbotech, France and Ivoclar-Vivadent, Liechenstein) were subjected to three-point bending tests in order to obtain fatigue results, flexural strength and modulus. Transverse and longitudinal polished sections were examined by scanning electron microscopy and evaluated by computer-assisted image analysis. Physical parameters, including volume % of fibers, their dispersion index and coordination number, were calculated and correlated with mechanical properties. The weaker posts showed more fiber dispersion, higher resin contents, larger numbers of visible defects and reduced fatigue resistance. The flexural strength was inversely correlated with fiber diameter and the flexural modulus was weakly related to coordination number, volume % of fibers and dispersion index. The interfacial adhesion between the silica fibers and the resin matrix was observed to be of paramount importance.

  7. Effect of polyester fiber reinforcement on the mechanical properties of interim fixed partial dentures

    PubMed Central

    Gopichander, N.; Halini Kumarai, K.V.; Vasanthakumar, M.

    2015-01-01

    Background Different reinforcements currently available for interim fixed partial denture (FPD) materials do not provide the ideal strength for long-term use. Therefore, the aim of this investigation was to develop a more ideal provisional material for long-term use with better mechanical properties. This study evaluated the effectiveness of polyester fiber reinforcement on different interim FPD materials. Methods Thirty resin-bonded FPDs were constructed from three provisional interim FPD materials. Specimens were tested with a universal testing machine (UTM). The modulus of elasticity and flexural strength were recorded in MPa. The compressive strength and degree of deflection were calculated from the obtained values, and a two-way analysis of variance (ANOVA) was used to determine the significance. Results The polyester fiber reinforcement increased the mechanical properties. The modulus of elasticity for heat-polymerized polymethyl methacrylate (PMMA) was 624 MPa, compared to 700.2 MPa for the reinforced heat-cured sample. The flexural strengths of the bis-acrylic and cold-polymerized reinforced samples increased significantly to 2807 MPa and 979.86 MPa, respectively, compared to the nonreinforced samples. The mean compressive strength of the reinforced cold-polymerized PMMA samples was 439.17 MPa; and for the reinforced heat-polymerized PMMA samples, it was 1117.41 MPa. The degree of deflection was significantly greater (P < 0.05) in the reinforced bis-acrylic sample (5.03 MPa), compared with the nonreinforced bis-acrylic sample (2.95 MPa). Conclusion Within the limitations of this study, polyester fiber reinforcements improved the mechanical properties of heat-polymerized PMMA, cold-polymerized PMMA, and bis-acrylic provisional FPD materials. PMID:26644754

  8. 21st century market opportunities for advanced fibers and composites

    SciTech Connect

    Segal, C.L.

    1996-07-01

    High-strength, high-modulus fibers based upon either carbon, organic polymers, or ceramics are relatively new materials. Full-scale commercial production of these fibers began within the last 25 years. Current sales of advanced fibers are measured in thousands of tons per year, not in hundreds of thousands of tons per year, as are sales of glass structural fibers. Selling prices are measured in tens of dollars per pound as compared to dollars per pound for glass fiber. Therefore, advanced fibers must still be considered as specialty materials that will be selected based only upon their high performance. While much thanks is due to the aerospace and sporting goods industries for keeping the interest in advanced fibers and composites alive, it is generally agreed that the market will not grow (and prices will not decline) until these fibers are accepted in the industrial market. This presentation identifies industrial market opportunities for advanced fibers and composites in the next century, which is actually tomorrow in the time-line from the beginning of commercialization of advanced fibers. Specific, potential applications are cited, and the estimated volumes and values of these application given. 3 tabs.

  9. Evolution of damage and plasticity in titanium-based, fiber-reinforced composites

    NASA Technical Reports Server (NTRS)

    Majumdar, B. S.; Newaz, G. M.; Ellis, J. R.

    1993-01-01

    The inelastic deformation mechanisms were evaluated for a model titanium-based, fiber-reinforced composite: a beta titanium alloy (Ti-15V-3Al-3Cr-3Sn) reinforced with SiC (SCS-6) fibers. The primary emphasis of this article is to illustrate the sequence in which damage and plasticity evolved for this system. The mechanical responses and the results of detailed microstructural evaluations for the 0(8), 90(8), and +/- 45(2s) line oriented laminates are provided. It is shown that the characteristics of the reaction zone around the fiber play a very important role in the way damage and plasticity evolve, particularly in the microyield regime of deformation, and must be included in any realistic constitutive model. Fiber-matrix debonding was a major damage mode for the off-axis systems. The tension test results are also compared with the predictions of a few constitutive models.

  10. Mechanical Properties of Sisal/Coir Fiber Reinforced Hybrid Composites Fabricated by Cold Pressing Method

    NASA Astrophysics Data System (ADS)

    Akash; Sreenivasa Rao, K. V.; Venkatesha Gupta, N. S.; kumar, D. S. Arun

    2016-09-01

    Bio-composites have less density and are environmental friendly materials that require less energy during production and subsequent machining. This paper reports the mechanical and water absorption properties of sodium hydroxide (NaOH) treated sisal and coir fiber reinforced epoxy resin thermo set hybrid composites. The hybrid composites were prepared by traditional cold pressing method at room temperature with applied pressure of 410.4 kg/cm2 for 3 hours pressurization time. The mechanical properties were characterized according to ASTM standards. Hybrid composites with 40wt% of sisal and coir fiber were found to possess higher tensile strength of 48.2MPa and flexural strength of 76.68 MPa among the fabricated hybrid composite specimens. Absorption of water increases with increasing fiber volume. The experimental result also show that the sisal and coir fibers are promising reinforcement for use in low cost bio-composites which have high strength to weight ratio.

  11. Evolution of damage and plasticity in titanium-based, fiber-reinforced composites

    SciTech Connect

    Majumdar, B.S. ); Newaz, G.M. ); Ellis, J.R. . Fatigue and Failure Branch)

    1993-07-01

    The inelastic deformation mechanisms were evaluated for a model titanium-based, fiber-reinforced composite: a beta titanium alloy (Ti-15V-3Al-3Cr-3Sn) reinforced with SiC (SCS-6) fibers. The primary emphasis of this article is to illustrate the sequence in which damage and plasticity evolved for this system. The mechanical responses and the results of detailed microstructural evaluations for the [0][sub 8], [90][sub 8], and [[plus minus]45][sub 2s] laminates are provided. It is shown that the characteristics of the reaction zone around the fiber play a very important role in the way damage and plasticity evolve, particularly in the microyield regime of deformation, and must be included in any realistic constitutive model. Fiber-matrix debonding was a major damage mode for the off-axis systems. The tension test results are also compared with the predictions of a few constitutive models.

  12. Characteristics of fatigue life and damage accumulation of short fiber-reinforced polymer composites

    SciTech Connect

    Yokobori, A.T. Jr.; Takeda, Hidetoshi; Adachi, Takeshi; Ha, J.C.; Yokobori, Takeo

    1996-12-31

    The relation between fatigue life and damage accumulation of fiber-reinforced polymer composite (FRP) is not yet clarified. For practical use of FRP, it is necessary to relate the fatigue life to the mechanism of damage accumulation. Damage formation is controlled by the mechanical behavior of the interface between the matrix and fiber. The authors used short glass fiber-reinforced polycarbonate composite in the experiments. By using an in situ (real time) observational fatigue testing machine, they investigated the relationship between fatigue life and damage accumulation. From these results, the fatigue life of this material was found to be dominated by damage accumulation which results from microfracture at the interface between the matrix and fiber. This microfracture is controlled by a cycle-dependent mechanism.

  13. Impact resistance of composite fan blades. [fiber reinforced graphite and boron epoxy blades for STOL operating conditions

    NASA Technical Reports Server (NTRS)

    Premont, E. J.; Stubenrauch, K. R.

    1973-01-01

    The resistance of current-design Pratt and Whitney Aircraft low aspect ratio advanced fiber reinforced epoxy matrix composite fan blades to foreign object damage (FOD) at STOL operating conditions was investigated. Five graphite/epoxy and five boron/epoxy wide chord fan blades with nickel plated stainless steel leading edge sheath protection were fabricated and impact tested. The fan blades were individually tested in a vacuum whirlpit under FOD environments. The FOD environments were typical of those encountered in service operations. The impact objects were ice balls, gravel, stralings and gelatin simulated birds. Results of the damage sustained from each FOD impact are presented for both the graphite boron reinforced blades. Tests showed that the present design composite fan blades, with wrap around leading edge protection have inadequate FOD impact resistance at 244 m/sec (800 ft/sec) tip speed, a possible STOL operating condition.

  14. Three-dimensional finite element analysis of posterior fiber-reinforced composite fixed partial denture Part 2: influence of fiber reinforcement on mesial and distal connectors.

    PubMed

    Aida, Nobuhisa; Shinya, Akikazu; Yokoyama, Daiichiro; Lassila, Lippo V J; Gomi, Harunori; Vallittu, Pekka K; Shinya, Akiyoshi

    2011-01-01

    The aim of this study was to evaluate the influence of connectors under two different loading conditions on displacement and stress distribution generated in isotropic hybrid composite fixed partial denture (C-FPD) and partially anisotropic fiber-reinforced hybrid composite fixed partial denture (FRC-FPD). To this end, two three-dimensional finite element (FE) models of three-unit FPD from mandibular second premolar to mandibular second molar - intended to replace the mandibular first molar - were developed. The two loading conditions employed were a vertical load of 629 N (applied to eight points on the occlusal surface) and a lateral load of 250 N (applied to three points of the pontic). The results suggested that the reinforcing fibers in FRC framework significantly improved the rigidity of the connectors against any twisting and bending moments induced by loading. Consequently, maximum principal stress and displacement generated in the connectors of FRC-FPD were significantly reduced because stresses generated by vertical and lateral loading were transferred to the reinforcing fibers. PMID:21282891

  15. SYLRAMIC™ SiC fibers for CMC reinforcement

    NASA Astrophysics Data System (ADS)

    Jones, Richard E.; Petrak, Dan; Rabe, Jim; Szweda, Andy

    2000-12-01

    Dow Corning researchers developed SYLRAMIC SiC fiber specifically for use in ceramic-matrix composite (CMC) components for use in turbine engine hot sections where excellent thermal stability, high strength and high thermal conductivity are required. This is a stoichiometric SiC fiber with a high degree of crystallinity, high tensile strength, high tensile modulus and good thermal conductivity. Owing to the small diameter, this textile-grade fiber can be woven into 2-D and 3-D structures for CMC fabrication. These properties are also of high interest to the nuclear community. Some initial studies have shown that SYLRAMIC fiber shows very good dimensional stability in a neutron flux environment, which offers further encouragement. This paper will review the properties of SYLRAMIC SiC fiber and then present the properties of polymer impregnation and pyrolysis (PIP) processed CMC made with this fiber at Dow Corning. While these composites may not be directly applicable to applications of interest to this audience, we believe that the properties shown will give good evidence that the fiber should be suitable for high temperature structural applications in the nuclear arena.

  16. Fiber-Reinforced Reactive Nano-Epoxy Composites

    NASA Technical Reports Server (NTRS)

    Zhong, Wei-Hong

    2011-01-01

    An ultra-high-molecular-weight polyethylene/ matrix interface based on the fabrication of a reactive nano-epoxy matrix with lower surface energy has been improved. Enhanced mechanical properties versus pure epoxy on a three-point bend test include: strength (25 percent), modulus (20 percent), and toughness (30 percent). Increased thermal properties include higher Tg (glass transition temperature) and stable CTE (coefficient of thermal expansion). Improved processability for manufacturing composites includes faster wetting rates on macro-fiber surfaces, lower viscosity, better resin infusion rates, and improved rheological properties. Improved interfacial adhesion properties with Spectra fibers by pullout tests include initial debonding force of 35 percent, a maximum pullout force of 25 percent, and energy to debond at 65 percent. Improved mechanical properties of Spectra fiber composites (tensile) aging resistance properties include hygrothermal effects. With this innovation, high-performance composites have been created, including carbon fibers/nano-epoxy, glass fibers/nano-epoxy, aramid fibers/ nano-epoxy, and ultra-high-molecularweight polyethylene fiber (UHMWPE).

  17. Effect of random/aligned nylon-6/MWCNT fibers on dental resin composite reinforcement.

    PubMed

    Borges, Alexandre L S; Münchow, Eliseu A; de Oliveira Souza, Ana Carolina; Yoshida, Takamitsu; Vallittu, Pekka K; Bottino, Marco C

    2015-08-01

    The aims of this study were (1) to synthesize and characterize random and aligned nanocomposite fibers of multi-walled carbon nanotubes (MWCNT)/nylon-6 and (2) to determine their reinforcing effects on the flexural strength of a dental resin composite. Nylon-6 was dissolved in hexafluoropropanol (10 wt%), followed by the addition of MWCNT (hereafter referred to as nanotubes) at two distinct concentrations (i.e., 0.5 or 1.5 wt%). Neat nylon-6 fibers (without nanotubes) were also prepared. The solutions were electrospun using parameters under low- (120 rpm) or high-speed (6000 rpm) mandrel rotation to collect random and aligned fibers, respectively. The processed fiber mats were characterized by scanning (SEM) and transmission (TEM) electron microscopies, as well as by uni-axial tensile testing. To determine the reinforcing effects on the flexural strength of a dental resin composite, bar-shaped (20×2×2 mm(3)) resin composite specimens were prepared by first placing one increment of the composite, followed by one strip of the mat, and one last increment of composite. Non-reinforced composite specimens were used as the control. The specimens were then evaluated using flexural strength testing. SEM was done on the fractured surfaces. The data were analyzed using ANOVA and the Tukey׳s test (α=5%). Nanotubes were successfully incorporated into the nylon-6 fibers. Aligned and random fibers were obtained using high- and low-speed electrospinning, respectively, where the former were significantly (p<0.001) stronger than the latter, regardless of the nanotubes׳ presence. Indeed, the dental resin composite tested was significantly reinforced when combined with nylon-6 fibrous mats composed of aligned fibers (with or without nanotubes) or random fibers incorporated with nanotubes at 0.5 wt%.

  18. Corrosion detection of steel reinforced concrete using combined carbon fiber and fiber Bragg grating active thermal probe

    NASA Astrophysics Data System (ADS)

    Li, Weijie; Ho, Siu Chun Michael; Song, Gangbing

    2016-04-01

    Steel reinforcement corrosion is one of the dominant causes for structural deterioration for reinforced concrete structures. This paper presents a novel corrosion detection technique using an active thermal probe. The technique takes advantage of the fact that corrosion products have poor thermal conductivity, which will impede heat propagation generated from the active thermal probe. At the same time, the active thermal probe records the temperature response. The presence of corrosion products can thus be detected by analyzing the temperature response after the injection of heat at the reinforcement-concrete interface. The feasibility of the proposed technique was firstly analyzed through analytical modeling and finite element simulation. The active thermal probe consisted of carbon fiber strands to generate heat and a fiber optic Bragg grating (FBG) temperature sensor. Carbon fiber strands are used due to their corrosion resistance. Wet-dry cycle accelerated corrosion experiments were performed to study the effect of corrosion products on the temperature response of the reinforced concrete sample. Results suggest a high correlation between corrosion severity and magnitude of the temperature response. The technique has the merits of high accuracy, high efficiency in measurement and excellent embeddability.

  19. Rate dependent response and failure of a ductile epoxy and carbon fiber reinforced epoxy composite

    SciTech Connect

    Brown, Eric N; Rae, Philip J; Dattelbaum, Dana M; Stahl, David B

    2010-01-01

    An extensive characterization suite has been performed on the response and failure of a ductile epoxy 55A and uniaxial carbon fiber reinforced epoxy composite of IM7 fibers in 55A resin from the quasistatic to shock regime. The quasistatic and intermediate strain rate response, including elastic modulus, yield and failure have are characterized by quasistatic, SHPB, and DMA measurements as a function of fiber orientation and temperature. The high strain rate shock effect of fiber orientation in the composite and response of the pure resin are presented for plate impact experiments. It has previously been shown that at lower impact velocities the shock velocity is strongly dependent on fiber orientation but at higher impact velocity the in-plane and through thickness Hugoniots converge. The current results are compared with previous studies of the shock response of carbon fiber composites with more conventional brittle epoxy matrices. The spall response of the composite is measured and compared with quasistatic fracture toughness measurements.

  20. Damage evaluation of reinforced concrete frame based on a combined fiber beam model

    NASA Astrophysics Data System (ADS)

    Shang, Bing; Liu, ZhanLi; Zhuang, Zhuo

    2014-04-01

    In order to analyze and simulate the impact collapse or seismic response of the reinforced concrete (RC) structures, a combined fiber beam model is proposed by dividing the cross section of RC beam into concrete fiber and steel fiber. The stress-strain relationship of concrete fiber is based on a model proposed by concrete codes for concrete structures. The stress-strain behavior of steel fiber is based on a model suggested by others. These constitutive models are implemented into a general finite element program ABAQUS through the user defined subroutines to provide effective computational tools for the inelastic analysis of RC frame structures. The fiber model proposed in this paper is validated by comparing with experiment data of the RC column under cyclical lateral loading. The damage evolution of a three-dimension frame subjected to impact loading is also investigated.

  1. Evaluation of Mechanical Properties of Injection Molding Composites Reinforced by Bagasse Fiber

    NASA Astrophysics Data System (ADS)

    Cao, Yong; Fukumoto, Isao

    BMC (Bulk Molding Compound) is composed of UP (Unsaturated Polyester) resin, glass fibers, and bagasse fibers which have been obtained after squeezing sugar cane. Our purpose is to use the bagasse fibers as reinforcement and filler in BMC to fabricate composites by injection molding and injection compression molding. The mechanical properties of injection molding composites were improved after adding the bagasse fibers. Observing the fracture surface of the tensile test specimen through SEM, we could notice the glass fibers were penetrated into the bagasse fibers longitudinally. Along with UP resin solidifying, the glass fibers were firmly fixed in the bagasse fibers and finally united with them. This phenomenon could bring on the same effect as the glass fibers length was prolonged, so that the adhesion interface between fiber and matrix resin became larger, which leads to the increase in the mechanical properties. Otherwise, it was observed that UP resin sufficiently permeated the bagasse fibers and solidified. This also contributes to enhancing the mechanical properties drastically.

  2. CN force predication model in milling of carbon fiber reinforced polymers

    NASA Astrophysics Data System (ADS)

    Kalla, Devi; Lodhia, Prashant; Bajracharya, Bijay; Twomey, Janet; Sheikh-Ahmad, Jamal

    2005-11-01

    Fiber reinforced polymers are widely used in the transportation, aerospace and chemical industries. In rare instances these materials are produced net-shape, and secondary processing such as machining and assembly may be required to produce a finished product. Because fiber reinforced polymers are heterogeneous materials, they do not machine in a similar way to metals. Thus, the theory of metal machining is not valid for the analysis of machining of fiber- reinforced composites. Previous attempts in modeling this problem have adopted Merchant's theory from metal cutting by assuming that chip formation takes place in a shear plane which inclination angle is determined by the minimum energy principle. This class of models showed that model predictions are valid only for fiber orientations less than 60°. The work presented here focuses on providing predictive models for the cutting forces in unidirectional composites. The models are based on the specific cutting energy principle and account for a wide range of fiber orientations and chip thickness. Results from two forms of non-linear modeling methods, non-linear regression and committee neural networks, were compared. It was found that committee neural networks provide better prediction capability by smoothing and capturing the inherent non-linearity in the data. The model predictions were found to be in good agreement with experimental results over the entire range of fiber orientations from 0 to 180°.

  3. Natural-fiber-reinforced polymer composites in automotive applications

    NASA Astrophysics Data System (ADS)

    Holbery, James; Houston, Dan

    2006-11-01

    In the past decade, natural-fiber composites with thermoplastic and thermoset matrices have been embraced by European car manufacturers and suppliers for door panels, seat backs, headliners, package trays, dashboards, and interior parts. Natural fibers such as kenaf, hemp, flax, jute, and sisal offer such benefits as reductions in weight, cost, and CO2, less reliance on foreign oil sources, and recyclability. However, several major technical considerations must be addressed before the engineering, scientific, and commercial communities gain the confidence to enable wide-scale acceptance, particularly in exterior parts where a Class A surface finish is required. Challenges include the homogenization of the fiber's properties and a full understanding of the degree of polymerization and crystallization, adhesion between the fiber and matrix, moisture repellence, and flame-retardant properties, to name but a few.

  4. Use of an alternative pontic foundation technique for a fiber-reinforced composite fixed partial denture: a clinical report.

    PubMed

    Ayna, Emrah; Celenk, Sema

    2005-05-01

    This article describes the treatment of a patient for whom a fiber-composite laminate dowel and core and polyethylene fiber were used as a conservative alternative to provide a dowel-and-core and fixed partial denture foundation. The treatment plan included removing the existing restoration on the maxillary right first molar, placing a fiber-reinforced resin dowel and core for retention and reinforcement of the maxillary first premolar, and fabricating a definitive restoration using polyethylene fiber to reinforce the fixed partial denture.

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  6. Method of Manufacturing Carbon Fiber Reinforced Carbon Composite Valves

    NASA Technical Reports Server (NTRS)

    Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor)

    1998-01-01

    A method for forming a carbon composite valve for internal combustion engines is discussed. The process includes the steps of braiding carbon fiber into a rope thereby forming a cylindrically shaped valve stem portion and continuing to braid said fiber while introducing into the braiding carbon fiber rope a carbon matrix plug having an outer surface in a net shape of a valve head thereby forming a valve head portion. The said carbon matrix plug acting as a mandrel over which said carbon fiber rope is braided, said carbon fiber rope and carbon matrix plug forming a valve head portion suitable for mating with a valve seat; cutting said braided carbon valve stem portion at one end to form a valve tip and cutting said braided carbon fiber after said valve head portion to form a valve face and thus provide a composite valve preform; and densifying said preform by embedding the braided carbon in a matrix of carbon to convert said valve stem portion to a valve stem and said valve head portion to a valve head thereby providing said composite valve.

  7. 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.

  8. Durability-Based Design Criteria for a Quasi-Isotropic Carbon-Fiber-Reinforced Thermoplastic Automotive Composite

    SciTech Connect

    Naus, Dan J; Corum, James; Klett, Lynn B; Davenport, Mike; Battiste, Rick; Simpson, Jr., William A

    2006-04-01

    This report provides recommended durability-based design properties and criteria for a quais-isotropic carbon-fiber thermoplastic composite for possible automotive structural applications. The composite consisted of a PolyPhenylene Sulfide (PPS) thermoplastic matrix (Fortron's PPS - Ticona 0214B1 powder) reinforced with 16 plies of carbon-fiber unidirectional tape, [0?/90?/+45?/-45?]2S. The carbon fiber was Hexcel AS-4C and was present in a fiber volume of 53% (60%, by weight). The overall goal of the project, which is sponsored by the U.S. Department of Energy's Office of Freedom Car and Vehicle Technologies and is closely coordinated with the Advanced Composites Consortium, is to develop durability-driven design data and criteria to assure the long-term integrity of carbon-fiber-based composite systems for automotive structural applications. This document is in two parts. Part 1 provides design data and correlations, while Part 2 provides the underlying experimental data and models. The durability issues addressed include the effects of short-time, cyclic, and sustained loadings; temperature; fluid environments; and low-energy impacts (e.g., tool drops and kickups of roadway debris) on deformation, strength, and stiffness. Guidance for design analysis, time-independent and time-dependent allowable stresses, rules for cyclic loadings, and damage-tolerance design guidance are provided.

  9. Reactive processing of textile-natural fiber reinforced anionic polyamide-6 composites

    SciTech Connect

    Kan, Ze; Chen, Peng; Liu, Zhengying; Feng, Jianmin; Yang, Mingbo

    2015-05-22

    Nowadays natural fiber, used in reinforced composites, is widely concerned. However, no natural fiber reinforced reactive thermoplastic polymer grades had been prepared so far. Through our studies, it was demonstrated that there was a severe retardation and discoloration occurred in the reactive processing between anionic polyamide-6 (APA-6) and natural fiber, which result in incomplete polymerization when put together. In order to solve the problem, two methods were adopted in this paper, which are fiber pretreatment and usage of a new-style initiator called caprolactam magnesium bromide. The former is to remove sizing agent and impurities on the surface of fiber, and the latter is to weaken the side reactions between APA-6 and natural fiber by the nature of its lower reactivity and weaker alkaline. In cooperation with both methods, the severe retardation and discoloration had been improved significantly, so that the polymerization of APA-6 in natural fiber was occurred smoothly. Following textile-natural fiber reinforced APA-6 composites with an average thickness of 2.5 mm and a fiber volume content of 50% was prepared by vacuum assisted resin transfer molding (VARTM). The soxhlet extraction, dilute solution viscometry and differential scanning calorimeter (DSC) measurements respectively suggested the degree of conversion, viscosity-average molar mass and crystallization of composites was up to 94%, 11.3×104 and 50%. Remarkable improvement of mechanical properties were achieved through dynamic mechanical analysis (DMA), tensile and three-point bending test. Favorable interfacial adhesion and wettability were revealed by scanning electron microscopy (SEM) observation. Therefore, all of the above good performance make this new-style and environmentally friendly composites have broad application prospects.

  10. Carbon fiber-reinforced composites: Applications in alternative energy & transportation systems

    SciTech Connect

    Dry, A.; Betts, J.; Strandburg, D.

    1996-12-31

    Historically, carbon fiber-reinforced composites (CFRCs) were limited to aerospace applications, primarily due to the high cost of the staple carbon fiber strands and labor-intensive composite manufacturing. By the early 1990s, new cost-effective fabrication methods reduced the price of carbon fiber tenfold from the initial level of over $100.00/lb. to around $12.00/lb. As a result, entirely new markets for CFRCs emerged to take advantage of the unbeatable strength/weight properties, primarily in the sporting goods industry. Today`s market is much more varied, with applications appearing in infrastructure, industrial and mechanical components, and alternative energy and transportation systems. In fact, carbon fiber-reinforced composites are enabling the technologies for the myriad of new alternative energy and transportation systems in development. Compressed natural gas (CNG) and liquid natural gas (LNG) tanks are filament wound from carbon fiber, which provides the lightweight/high strength construction necessary for efficient energy storage. Similarly, carbon fiber flywheels allow higher rotor speeds for greater energy storage capability. Lightweight carbon fiber-reinforced windmill blades, are in development with longer chord lengths for greater energy capture. In summary, CFRCs are being evaluated for structural components in practically all alternative fuel and transportation sectors, including automotive, due to the increased energy efficiency allowed by the overall weight reduction. As new programs to further develop these high volume applications emerge, the carbon fiber industry will be challenged to reduce the cost of carbon fiber and composite manufacturing methods to ensure continued market expansion.

  11. Development and Evaluation of Novel Coupling Agents for Kenaf-Fiber-Reinforced Unsaturated Polyester Composites

    NASA Astrophysics Data System (ADS)

    Ren, Xiaofeng

    Natural fibers are gaining popularity as reinforcement materials for thermoset resins over the last two decades. Natural fibers are inexpensive, abundant, renewable and environmentally friendly. Kenaf fibers are one of the natural fibers that can potentially be used for reinforcing unsaturated polyester (UPE). As a polymer matrix, UPE enjoys a 40% market share of all the thermoset composites. This widespread application is due to many favorable characteristics including low cost, ease of cure at room temperature, ease of molding, a good balance of mechanical, electrical and chemical properties. One of the barriers for the full utilization of the kenaf fiber reinforced UPE composites, however, is the poor interfacial adhesion between the natural fibers and the UPE resins. The good interfacial adhesion between kenaf fibers and UPE matrix is essential for generating the desired properties of kenaf-UPE composites for most of the end applications. Use of a coupling agent is one of the most effective ways of improving the interfacial adhesion. In this study, six novel effective coupling agents were developed and investigated for kenaf-UPE composites: DIH-HEA, MFA, NMA, AESO-DIH, AESO-MDI, and AESO-PMDI. All the coupling agents were able to improve the interfacial adhesion between kanaf and UPE resins. The coupling agents were found to significantly enhance the flexural properties and water resistance of the kenaf-UPE composites. Fourier transform infrared spectroscopy (FTIR) confirmed all the coupling agents were covalently bonded onto kenaf fibers. Scanning electron microscopy (SEM) images of the composites revealed the improved interfacial adhesion between kanaf fibers and UPE resins.

  12. Reactive processing of textile-natural fiber reinforced anionic polyamide-6 composites

    NASA Astrophysics Data System (ADS)

    Kan, Ze; Chen, Peng; Liu, Zhengying; Feng, Jianmin; Yang, Mingbo

    2015-05-01

    Nowadays natural fiber, used in reinforced composites, is widely concerned. However, no natural fiber reinforced reactive thermoplastic polymer grades had been prepared so far. Through our studies, it was demonstrated that there was a severe retardation and discoloration occurred in the reactive processing between anionic polyamide-6 (APA-6) and natural fiber, which result in incomplete polymerization when put together. In order to solve the problem, two methods were adopted in this paper, which are fiber pretreatment and usage of a new-style initiator called caprolactam magnesium bromide. The former is to remove sizing agent and impurities on the surface of fiber, and the latter is to weaken the side reactions between APA-6 and natural fiber by the nature of its lower reactivity and weaker alkaline. In cooperation with both methods, the severe retardation and discoloration had been improved significantly, so that the polymerization of APA-6 in natural fiber was occurred smoothly. Following textile-natural fiber reinforced APA-6 composites with an average thickness of 2.5 mm and a fiber volume content of 50% was prepared by vacuum assisted resin transfer molding (VARTM). The soxhlet extraction, dilute solution viscometry and differential scanning calorimeter (DSC) measurements respectively suggested the degree of conversion, viscosity-average molar mass and crystallization of composites was up to 94%, 11.3×104 and 50%. Remarkable improvement of mechanical properties were achieved through dynamic mechanical analysis (DMA), tensile and three-point bending test. Favorable interfacial adhesion and wettability were revealed by scanning electron microscopy (SEM) observation. Therefore, all of the above good performance make this new-style and environmentally friendly composites have broad application prospects.

  13. An In Vitro Comparative Evaluation of Fracture Resistance of Custom Made, Metal, Glass Fiber Reinforced and Carbon Reinforced Posts in Endodontically Treated Teeth

    PubMed Central

    Sonkesriya, Subhash; Olekar, Santosh T; Saravanan, V; Somasunderam, P; Chauhan, Rashmi Singh; Chaurasia, Vishwajit Rampratap

    2015-01-01

    Background: Posts are used to enhance crown buildup in pulpless teeth with destructed crown portion. Different types of post are used in endodontically treated teeth. The aim of the present in vitro study was to evaluate fracture resistance of custom made, metal, glass fiber reinforced and carbon reinforced posts in endodontically treated teeth. Materials and Methods: An in vitro study was carried out on extracted 40 human maxillary central incisor teeth, which was divided into four groups with 10 samples in each group with custom made, metal post, glass fiber reinforced, and carbon reinforced posts. The samples were decoronated at cemento-enamel junction and endodontically treated. Post space was prepared and selected posts were cemented. The composite cores were prepared at the height of 5 mm and samples mounted on acrylic blocks. Later fracture resistance to the compressive force of samples was measured using Universal Testing Machine. Results: The maximum resistance to the compressive force was observed in carbon reinforced and glass fiber reinforced posts compared others which is statistically significant (P > 0.001) and least was seen in custom fabricated post. Conclusion: It is concluded that carbon reinforced fiber post and glass fiber posts showed good fracture resistance compared to custom made and metal posts. PMID:26028904

  14. Method of making carbon fiber-carbon matrix reinforced ceramic composites

    NASA Technical Reports Server (NTRS)

    Williams, Brian (Inventor); Benander, Robert (Inventor)

    2007-01-01

    A method of making a carbon fiber-carbon matrix reinforced ceramic composite wherein the result is a carbon fiber-carbon matrix reinforcement is embedded within a ceramic matrix. The ceramic matrix does not penetrate into the carbon fiber-carbon matrix reinforcement to any significant degree. The carbide matrix is a formed in situ solid carbide of at least one metal having a melting point above about 1850 degrees centigrade. At least when the composite is intended to operate between approximately 1500 and 2000 degrees centigrade for extended periods of time the solid carbide with the embedded reinforcement is formed first by reaction infiltration. Molten silicon is then diffused into the carbide. The molten silicon diffuses preferentially into the carbide matrix but not to any significant degree into the carbon-carbon reinforcement. Where the composite is intended to operate between approximately 2000 and 2700 degrees centigrade for extended periods of time such diffusion of molten silicon into the carbide is optional and generally preferred, but not essential.

  15. Predicted inlet gas temperatures for tungsten fiber reinforced superalloy turbine blades

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    Tungsten fiber reinforced superalloy composite (TFRS) impingement cooled turbine blade inlet gas temperatures were calculated taking into account material spanwise strength, thermal conductivity, material oxidation resistance, fiber-matrix interaction, and coolant flow. Measured values of TFRS thermal conductivities are presented. Calculations indicate that blades made of 30 volume percent fiber content TFRS having a 12,000 N-m/kg stress-to-density ratio while operating at 40 atmospheres and a 0.06 coolant flow ratio could permit a turbine blade inlet gas temperature of over 1900K. This is more than 150K greater than similar superalloy blades.

  16. Complementary methods for nondestructive testing of composite materials reinforced with carbon woven fibers

    NASA Astrophysics Data System (ADS)

    Steigmann, R.; Iftimie, N.; Sturm, R.; Vizureanu, P.; Savin, A.

    2015-11-01

    This paper presents complementary methods used in nondestructive evaluation (NDE) of composite materials reinforced with carbon woven fibers as two electromagnetic methods using sensor with orthogonal coils and sensor with metamaterials lens as well as ultrasound phased array method and Fiber Bragg gratings embedded instead of a carbon fiber for better health monitoring. The samples were impacted with low energy in order to study delamination influence. The electromagnetic behavior of composite was simulated by finite- difference time-domain (FDTD) software, showing a very good concordance with electromagnetic nondestructive evaluation tests.

  17. Carbon Fiber Reinforced Carbon Composite Rotary Valve for an Internal Combustion Engine

    NASA Technical Reports Server (NTRS)

    Northam, G.Burton (Inventor); Ransone, Philip O. (Inventor); Rivers, H. Kevin (Inventor)

    2000-01-01

    Carbon fiber reinforced carbon composite rotary sleeve, and disc valves for internal combustion engines and the like are disclosed. The valves are formed from knitted or braided or wrap-locked carbon fiber shapes. Also disclosed are valves fabricated from woven carbon fibers and from molded carbon matrix material. The valves of the present invention with their very low coefficient of thermal expansion and excellent thermal and self-lubrication properties do not present the sealing and lubrication problems that have prevented rotary sleeve and disc valves from operating efficiently and reliably in the past. Also disclosed are a sealing tang to further improve sealing capabilities and anti-oxidation treatments.

  18. Carbon Fiber Reinforced Carbon Composites Rotary Valves for Internal Combustion Engines

    NASA Technical Reports Server (NTRS)

    Northam, G. Burton (Inventor); Ransone, Philip O. (Inventor); Rivers, H. Kevin (Inventor)

    1999-01-01

    Carbon fiber reinforced carbon composite rotary, sleeve, and disc valves for internal combustion engines and the like are disclosed. The valves are formed from knitted or braided or warp-locked carbon fiber shapes. Also disclosed are valves fabricated from woven carbon fibers and from molded carbon matrix material. The valves of the present invention with their very low coefficient of thermal expansion and excellent thermal and self-lubrication properties, do not present the sealing and lubrication problems that have prevented rotary, sleeve, and disc valves from operating efficiently and reliably in the past. Also disclosed are a sealing tang to further improve sealing capabilities and anti-oxidation treatments.

  19. Crystalline and tensile properties of carbon nanotube and graphene reinforced polyamide 12 fibers

    NASA Astrophysics Data System (ADS)

    Chatterjee, S.; Nüesch, F. A.; Chu, B. T. T.

    2013-02-01

    The influence of carbon nanotubes (CNTs) and graphene nanoplatelets (GnPs) on the structure and mechanical properties of polyamide 12 (PA12) fibers was investigated. As seen from wide-angle X-ray diffraction analysis the crystallinity index increases with incorporation of nanofillers due to nucleation effects. Marked improvement was noted for mechanical properties of the composites with increase in elastic modulus, yield stress and strength of the fibers. The most significant improvement of a factor of 4 could be observed for elastic modulus with the inclusion of 0.5 wt.% GnP. A comparative study was made between the fibers reinforced with CNTs and GnPs.

  20. Boron fiber reinforced plastics. (Latest citations from the Rubber and Plastics Research Association database). Published Search

    SciTech Connect

    Not Available

    1994-02-01

    The bibliography contains citations concerning the applications, molding processes, properties, design concepts, and market trends of polyester and epoxy resins reinforced with boron fibers. Performance evaluations from nondestructive test results are also included. (Contains 250 citations and includes a subject term index and title list.)

  1. Practical experience of steel fiber reinforced wet shotcrete in large underground construction projects

    SciTech Connect

    Garshol, K.

    1995-12-31

    The paper discusses advantages of SFRS (steel fiber reinforced shotcrete) in underground construction projects, including trends in rock support design; quality and durability of wet mix shotcrete; advantages in safety and working environment and the technical properties of SFRS. Key data from cases illustrate the above. Cost and time factors are highlighted.

  2. Modeling root-reinforcement with a Fiber-Bundle Model and Monte Carlo simulation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This paper uses sensitivity analysis and a Fiber-Bundle Model (FBM) to examine assumptions underpinning root-reinforcement models. First, different methods for apportioning load between intact roots were investigated. Second, a Monte Carlo approach was used to simulate plants with heartroot, platero...

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

    PubMed

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

    2014-01-01

    Fractured abutment screws may be replaced; however, sometimes, the screw cannot be removed and the entire implant must be surgically removed and replaced. The aim of this study was to compare the fracture resistance of abutment retention screws made of titanium, polyetheretherketone (PEEK) and 30% carbon fiber-reinforced PEEK, using an external hexagonal implant/UCLA-type abutment interface assembly. UCLA-type abutments were fixed to implants using titanium screws (Group 1), polyetheretherketone (PEEK) screws (Group 2), and 30% carbon fiber-reinforced PEEK screws (Group 3). The assemblies were placed on a stainless steel holding apparatus to allow for loading at 45o off-axis, in a universal testing machine. A 200 N load (static load) was applied at the central point of the abutment extremity, at a crosshead speed of 5 mm/minute, until failure. Data was analyzed by ANOVA and Tukey's range test. The titanium screws had higher fracture resistance, compared with PEEK and 30% carbon fiber-reinforced PEEK screws (p < 0.05). In contrast, no statistically significant difference was observed between the fracture resistance of the PEEK and the 30% carbon fiber-reinforced PEEK screws (p> 0.05). Finally, visual analysis of the fractions revealed that 100% of them occurred at the neck of the abutment screw, suggesting that this is the weakest point of this unit. PEEK abutment screws have lower fracture resistance, in comparison with titanium abutment screws. PMID:25098826

  4. PILOT-SCALE EVALUATION OF NEW RESIN APPLICATION EQUIPMENT FOR FIBER- REINFORCED PLASTICS

    EPA Science Inventory

    The article gives results of a pilot-scale evaluation of new resin application equipment for fiber- reinforced plastics. The study, an evaluation and comparison of styrene emissions, utilized Magnum's FIT(TM) nozzle with conventional spray guns and flow coaters (operated at both ...

  5. Seamless metal-clad fiber-reinforced organic matrix composite structures and process for their manufacture

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    A metallic outer sleeve is provided which is capable of enveloping a hollow metallic inner member having continuous reinforcing fibers attached to the distal end thereof. The inner member is then introduced into outer sleeve until inner member is completely enveloped by outer sleeve. A liquid matrix member is then injected into space between inner member and outer sleeve. A pressurized heat transfer medium is flowed through the inside of inner member, thereby forming a fiber reinforced matrix composite material. The wall thicknesses of both inner member and outer sleeve are then reduced to the appropriate size by chemical etching, to adjust the thermal expansion coefficient of the metal-clad composite structure to the desired value. thereby forming a fiber reinforced matrix composite material. The wall thicknesses of both inner member and outer sleeve are then reduced to the appropriate size by chemical etching, to adjust the thermal expansion coefficient of the metal-clad composite structure to the desired value. The novelty of this invention resides in the development of a efficient method of producing seamless metal clad fiber reinforced organic matrix composite structures.

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

    SciTech Connect

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

    2008-02-15

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

  7. AN EMPIRICAL MODEL TO PREDICT STYRENE EMISSIONS FROM FIBER-REINFORCED PLASTICS FABRICATION PROCESSES

    EPA Science Inventory

    Styrene is a designated hazardous air pollutant, per the 1990 Clean Air Act Amendments. It is also a tropospheric ozone precursor. Fiber-reinforced plastics (FRP) fabrication is the primary source of anthropogenic styrene emissions in the United States. This paper describes an em...

  8. Constitutive modelling of fiber-reinforced concrete under uniaxial tensile loading

    NASA Astrophysics Data System (ADS)

    Kullaa, Jyrki

    1993-01-01

    The mechanics of fiber reinforced concrete under uniaxial loading is studied. The focus is on the behavior after cracking. The interaction between the fiber and the matrix is the shear stress transfer. The stress can be elastic or frictional in nature. The bond parameters can be obtained by a simple pull-out test and theory. The load displacement curves for fibers of different lengths can be created by means of the calculated parameters. In a simple constitutive model, the main assumption is that the fibers are continuous and there exists multiple cracking in the matrix. After cracking, the fibers only carry the loading. The model uses efficiency factors in taking into account the short and randomly distributed fibers. Only the strengthening portion of the stress strain curve is analyzed. In the statistical model created, it is assumed that only one crack will develop. The theory ignores the strain of the matrix in fiber pull-out. The strain softening behavior is taken into consideration. A constitutive model which takes into account the strain softening part of the stress strain curve is developed. The crack distance and crack width are also calculated. The model takes into account one crack or multiple cracking states and different fracture mechanisms: fiber fracture or pull-out. The fibers are smooth and straight. They can be short or continuous, aligned or randomly distributed, brittle or ductile, and stiff or flexible. fibers may lie in the same matrix. &The results of the model are consistent with the other two models referred. The effects of different parameters can be studied and even new formulas can be found. The model can be used in the design of composite materials and is valid for other brittle matrix composites, such as fiber reinforced ceramics.

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

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Eldridge, Jeffrey I.

    1997-01-01

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

  10. Preparation and characterization of glass fibers - polymers (epoxy) bars (GFRP) reinforced concrete for structural applications

    NASA Astrophysics Data System (ADS)

    Alkjk, Saeed; Jabra, Rafee; Alkhater, Salem

    2016-06-01

    The paper presents some of the results from a large experimental program undertaken at the Department of Civil Engineering of Damascus University. The project aims to study the ability to reinforce and strengthen the concrete by bars from Epoxy polymer reinforced with glass fibers (GFRP) and compared with reinforce concrete by steel bars in terms of mechanical properties. Five diameters of GFRP bars, and steel bars (4mm, 6mm, 8mm, 10mm, 12mm) tested on tensile strength tests. The test shown that GFRP bars need tensile strength more than steel bars. The concrete beams measuring (15cm wide × 15cm deep × and 70cm long) reinforced by GFRP with 0.5 vol.% ratio, then the concrete beams reinforced by steel with 0.89 vol.% ratio. The concrete beams tested on deflection test. The test shown that beams which reinforced by GFRP has higher deflection resistance, than beams which reinforced by steel. Which give more advantage to reinforced concrete by GFRP.

  11. Fiber-reinforced piston for internal combustion engines and associated method of construction

    SciTech Connect

    Ban, K.; Daimaru, A.

    1987-07-07

    This patent describes a fiber reinforced piston for an internal combustion engine comprising a top land and a ring region provided with an uppermost ring groove. The top land and the ring region are defined by a reinforced part of the piston formed by a matrix metal reinforced with inorganic fibers. The reinforced part of the piston is circularly symmetrical around an axis of the piston and forms an annulus around a top portion of the piston. The reinforced part has a cross-section, in a plane containing the axis of the piston, of substantially rectangular shape except for the uppermost ring groove. The piston has an upper crown surface, the reinforced part being formed as a cylindrical shell having an upper radial surface which is continuously formed in the upper crown surface. A lower radial surface and an inner cylindrical surface join the upper and lower radial surfaces and an outer cylindrical surface has a radius equal to that of the outer cylindrical surface of the piston. The uppermost ring groove has an upper annular side wall surface, a lower annular side wall surface and an annular bottom surface connecting the upper and lower annular side wall surfaces, the inner cylindrical surface of the reinforced part having a smaller radius than that of the annular bottom surface of the uppermost ring groove. The reinforced part extends in the axial direction of the piston from the upper crown surface to a position below the lower annular side surface of the uppermost ring groove. The uppermost ring groove is totally defined within the reinforced part.

  12. Generalized Magneto-thermoelasticity in a Fiber-Reinforced Anisotropic Half-Space with Energy Dissipation

    NASA Astrophysics Data System (ADS)

    Othman, Mohamed I. A.; Atwa, Sarhan Y.

    2012-06-01

    The propagation of plane waves in a fiber-reinforced, anisotropic thermoelastic half-space proposed by Green and Naghdi theory under the effect of magnetic field is discussed. The problem has been solved analytically using normal mode analysis to obtain the exact solution of the temperature, the displacement components, and the thermal stress. Numerical results for the temperature distribution, the displacement components, and the thermal stress are given and illustrated graphically. Comparisons are made with the results predicted by types II and III in the presence and in the absence of the effect of a magnetic field and fiber reinforcement. It is found that the reinforcement and magnetic field have great effects on the distribution of the field quantities.

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

    PubMed

    Chen, Xi; Li, Yan; Gu, Ning

    2010-08-01

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

  14. 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.

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

    SciTech Connect

    Matlin, W.M.; Stinton, D.P.; Besmann, T.M.

    1995-08-01

    A two-step forced chemical vapor infiltration process was developed that reduced infiltration times for 4.45 cm dia. by 1.27 cm thick Nicalon{sup +} fiber preforms by two thirds while maintaining final densities near 90 %. In the first stage of the process, micro-voids within fiber bundles in the cloth were uniformly infiltrated throughout the preform. In the second stage, the deposition rate was increased to more rapidly fill the macro-voids between bundles within the cloth and between layers of cloth. By varying the thermal gradient across the preform uniform infiltration rates were maintained and high final densities achieved.

  16. Friction and wear behavior of graphite fiber reinforced polymide composites

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.; Sliney, H. E.

    1977-01-01

    The friction and wear rate characteristics of 50/50 (weight percent) graphite fiber polyimide composites were studied by sliding metallic hemispherically tipped riders against disks made from the composites. Two different polyimides and two different graphite fibers were evaluated. Also studied were such variables as the effect of moisture in an air atmosphere; the effect of temperature; and the effect of different sliding speeds. In general, wear to the the metallic riders was negligible, and composite wear increased at a constant rate as a function of number of sliding cycles.

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

    NASA Astrophysics Data System (ADS)

    Setoodeh, Shahriar

    The growing number of applications of composite materials in aerospace and naval structures along with advancements in manufacturing technologies demand continuous innovations in the design of composite structures. In the traditional design of composite laminates, fiber orientation angles are constant for each layer and are usually limited to 0, 90, and +/-45 degrees. To fully benefit from the directional properties of composite laminates, such limitations have to be removed. The concept of variable-stiffness laminates allows the stiffness properties to vary spatially over the laminate. Through tailoring of fiber orientations and laminate thickness spatially in an optimal fashion, mechanical properties of a part can be improved. In this thesis, the optimal design of variable-stiffness fiber-reinforced composite laminates is studied using an emerging numerical engineering optimization scheme based on the cellular automata paradigm. A cellular automaton (CA) based design scheme uses local update rule for both field variables (displacements) and design variables (lay-up configuration and laminate density measure) in an iterative fashion to convergence to an optimal design. In the present work, the displacements are updated based on the principle of local equilibrium and the design variables are updated according to the optimality criteria for minimum compliance design. A closed form displacement update rule for constant thickness isotropic continua is derived, while for the general anisotropic continua with variable thickness a numeric update rule is used. Combined lay-up and topology design of variable-stiffness flat laminates is performed under the action of in-plane loads and bending loads. An optimality criteria based formulation is used to obtain local design rules for minimum compliance design subject to a volume constraint. It is shown that the design rule splits into a two step application. In the first step an optimal lay-up configuration is computed and in

  18. Poly(ɛ-caprolactone) composites reinforced by biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fiber.

    PubMed

    Ju, Dandan; Han, Lijing; Li, Fan; Chen, Shan; Dong, Lisong

    2014-06-01

    Biodegradable and biosourced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) fiber was used as a reinforcing agent, and environment friendly poly(ɛ-caprolactone) (PCL) composites were prepared by melt compounding. The mechanical properties, rheological properties, and enzymatic degradation of the PCL composites were investigated in detail. With the addition of PHBV fibers, the PCL composites showed increased tensile yielding strength and modulus. Especially, the storage modulus from the results of dynamic mechanical analysis was increased significantly, suggesting that PCL was obviously reinforced by adding PHBV fibers. With increasing the PHBV fiber content, the complex viscosity and modulus of PCL increased, especially at low frequencies, indicating that a network structure was formed in the composites. The network structure resulted in evident solid-like response due to the restriction of the chain mobility of PCL matrix, which was further confirmed by the Han and Cole-Cole plots. The morphology, evaluated by scanning electron microscopy, indicated PCL and PHBV fiber were not highly incompatible and the interfacial adhesion was good, which was beneficial to the reinforcement effect. The biodegradability of the PCL was significantly promoted after composites preparation. Such studies are of great interest in the development of environment friendly composites from biodegradable polymers.

  19. Deformation behavior of FRP-metal composites locally reinforced with carbon fibers

    NASA Astrophysics Data System (ADS)

    Scholze, M.; Kolonko, A.; Lindner, T.; Lampke, T.; Helbig, F.

    2016-03-01

    This study investigates variations of hybrid laminates, consisting of one aluminum sheet and a unidirectional glass fiber (GF) reinforced polyamide 6 (PA6) basic structure with partial carbon fiber (CF) reinforcement. To create these heterogeneous FRP laminates, it is necessary to design and produce semi-finished textile-based products. Moreover, a warp knitting machine in conjunction with a warp thread offset unit was used to generate bionic inspired compounds. By the variation of stacking prior to the consolidation process of the hybrid laminate, an oriented CF reinforcement at the top and middle layer of the FRP is realized. In both cases the GFRP layer prevents contact between the aluminum and carbon fibers. In so doing, the high strength of carbon fibers can be transferred to the hybrid laminate in load directions with an active prevention of contact corrosion. The interface strength between thermoplastic and metal component was improved by a thermal spray coating on the aluminum sheet. Because of the high surface roughness and porosity, mechanical interlock was used to provide high interface strength without bonding agents between both components. The resulting mechanical properties of the hybrid laminates are evaluated by three point bending tests in different load directions. The effect of local fiber orientation and layer positioning on failure and deformation mechanism is additionally investigated by digital image correlation (DIC).

  20. Fatigue Hysteresis of Carbon Fiber-Reinforced Ceramic-Matrix Composites at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Li, Longbiao

    2016-02-01

    When the fiber-reinforced ceramic-matrix composites (CMCs) are first loading to fatigue peak stress, matrix multicracking and fiber/matrix interface debonding occur. Under fatigue loading, the stress-strain hysteresis loops appear as fiber slipping relative to matrix in the interface debonded region upon unloading/reloading. Due to interface wear at room temperature or interface oxidation at elevated temperature, the interface shear stress degredes with increase of the number of applied cycles, leading to the evolution of the shape, location and area of stress-strain hysteresis loops. The evolution characteristics of fatigue hysteresis loss energy in different types of fiber-reinforced CMCs, i.e., unidirectional, cross-ply, 2D and 2.5D woven, have been investigated. The relationships between the fatigue hysteresis loss energy, stress-strain hysteresis loops, interface frictional slip, interface shear stress and interface radial thermal residual stress, matrix stochastic cracking and fatigue peak stress of fiber-reinforced CMCs have been established.

  1. Carbon fibers: Thermochemical recovery from advanced composite materials and activation to an adsorbent

    NASA Astrophysics Data System (ADS)

    Staley, Todd Andrew

    This research addresses an expanding waste disposal problem brought about by the increasing use of advanced composite materials, and the lack of technically and environmentally viable recycling methods for these materials. A thermochemical treatment process was developed and optimized for the recycling of advanced composite materials. Counter-current gasification was employed for the treatment of carbon fiber reinforced-epoxy resin composite wastes. These materials were treated, allowing the reclamation of the material's valuable components. As expected in gasification, the organic portion of the waste was thermochemically converted to a combustible gas with small amounts of organic compounds that were identified by GC/MS. These compounds were expected based on data in the literature. The composites contain 70% fiber reinforcement, and gasification yielded approximately 70% recovered fibers, representing nearly complete recovery of fibers from the waste. Through SEM and mechanical testing, the recovered carbon fibers were found to be structurally and mechanically intact, and amenable to re-use in a variety of applications, some of which were identified and tested. In addition, an application was developed for the carbon fiber component of the waste, as an activated carbon fiber adsorbent for the treatment of wastewaters. This novel class of adsorbent was found to have adsorption rates, for various organic molecules, up to a factor of ten times those of commercial granular activated carbon, and adsorption capacities similar to conventional activated carbons. Overall, the research addresses an existing environmental waste problem, employing a thermochemical technique to recycle and reclaim the waste. Components of the reclaimed waste material are then employed, after further modification, to address other existing and potential environmental waste problems.

  2. Modeling the Effect of Active Fiber Cooling on the Microstructure of Fiber-Reinforced Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Nguyen, Nguyen Q.; Peterson, Sean D.; Gupta, Nikhil; Rohatgi, Pradeep K.

    2009-08-01

    A modified pressure infiltration process was recently developed to synthesize carbon-fiber-reinforced aluminum matrix composites. In the modified process, the ends of carbon fibers are extended out of the crucible to induce selective cooling. The process is found to be effective in improving the quality of composites. The present work is focused on determining the effect of the induced conductive heat transfer on the composite system through numerical methods. Due to the axisymmetry of the system, a two-dimensional (2-D) model is studied that can be expanded into three dimensions. The variables in this transient analysis include the fiber radius, fiber length, and melt superheat temperature. The results show that the composite system can be tailored to have a temperature on the fiber surface that is lower than the melt, to promote nucleation on the fiber surface. It is also observed that there is a point of inflection in the temperature profile along the particle/melt interface at which there is no temperature gradient in the radial direction. The information about the inflection point can be used to control the diffusion of solute atoms in the system. The result can be used in determining the optimum fiber volume fraction in metal matrix composite (MMC) materials to obtain the desired microstructure.

  3. Mechanical behavior of fiber reinforced SiC/RBSN ceramic matrix composites: Theory and experiment

    NASA Technical Reports Server (NTRS)

    Chulya, Abhisak; Gyekenyesi, John P.; Bhatt, Ramakrishna T.

    1991-01-01

    The mechanical behavior of continuous fiber reinforced SiC/RBSN (Reaction Bonded Silicon Nitride) composites with various fiber contents is evaluated. Both catastrophic and noncatastrophic failures are observed in tensile specimens. Damage and failure mechanisms are identified via in-situ monitoring using NDE (nondestructive evaluation) techniques through the loading history. Effects of fiber/matrix interface debonding (splitting) parallel to fibers are discussed. Statistical failure behavior of fibers is also observed, especially when the interface is weak. Micromechanical models incorporating residual stresses to calculate the critical matrix cracking strength, ultimate strength, and work of pull-out are reviewed and used to predict composite response. For selected test problems, experimental measurements are compared to analytical predictions.

  4. Hemp-Fiber-Reinforced Unsaturated Polyester Composites: Optimization of Processing and Improvement of Interfacial Adhesion

    SciTech Connect

    Qui, Renhui; Ren, Xiaofeng; Fifield, Leonard S.; Simmons, Kevin L.; Li, Kaichang

    2011-02-25

    The processing variables for making hemp-fiber-reinforced unsaturated polyester (UPE) composites were optimized through orthogonal experiments. It was found that the usage of initiator, methyl ethyl ketone peroxide, had the most significant effect on the tensile strength of the composites. The treatment of hemp fibers with a combination of 1, 6-diisocyanatohexane (DIH) and 2-hydroxylethyl acrylate (HEA) significantly increased tensile strength, flexural modulus of rupture and flexural modulus of elasticity, and water resistance of the resulting hemp-UPE composites. FTIR spectra revealed that DIH and HEA were covalently bonded to hemp fibers. Scanning electronic microscopy graphs of the fractured hemp-UPE composites demonstrated that treatment of hemp fibers with a combination of DIH and HEA greatly improved the interfacial adhesion between hemp fibers and UPE. The mechanism of improving the interfacial adhesion is proposed.

  5. Model of brittle matrix composite toughening based on discrete fiber reinforcement

    NASA Technical Reports Server (NTRS)

    Rubinstein, Asher A.

    1992-01-01

    An analytical approach for the analysis of the effectiveness of fiber reinforcement in brittle matrix composites is presented. The analytical method allows consideration of discrete fiber distribution and examination of the development of crack growth parameters on microscale. The problem associated with the bridging zone development is addressed here; therefore, the bridging zone is considered to be smaller than the main preexisting crack, and the small scale approach is used. The mechanics of the reinforcement is accurately accounted for in the process zone of a growing crack. Closed form solutions characterizing the initial failure process are presented for linear and nonlinear force - fiber pullout displacement relationships. The implicit exact solution for the extended bridging zone is presented as well.

  6. Design and realization a skiff racing boat hull made of natural fibers reinforced composite

    NASA Astrophysics Data System (ADS)

    Collotta, M.; Solazzi, L.; Pandini, S.; Tomasoni, G.; Alberti, M.; Donzella, G.

    2016-05-01

    This paper discusses the development of a racing boat with an hull made of a composite material reinforced by natural fibers. In particular, we report here the design and realization of the boat hull, the assessment of its mechanical performance by means of a computer assisted simulation, and the cost analysis to assess the economic sustainability of the new composite developed. The results have shown that the new composite has a performance comparable with conventional glass fiber reinforced composites employed for the realization of this type of boat, accordingly to the technology employed and the lamination sequence adopted. Moreover, the FEM analysis performed over the skiff of the designed and constructed boat has demonstrated a successful choice of the material for real application, as it was later confirmed by the good performance of the boat in water. Finally, the cost analysis highlighted the economic sustainability of the new composite, allowing a cost saving of over 28% with respect to carbon fiber composites.

  7. Evaluation of RC Bridge Piers Retrofitted using Fiber-Reinforced Polymer (FRP)

    SciTech Connect

    Shayanfar, M. A.; Zarrabian, M. S.

    2008-07-08

    For many long years, steel reinforcements have been considered as the only tool for concrete confinements and studied widely, but nowadays application of Fiber Reinforced Polymer (FRP) as an effective alternative is well appreciated. Many bridges have been constructed in the past that are necessary to be retrofitted for resisting against the earthquake motions. The objective of this research is evaluation of nonlinear behavior of RC bridge piers. Eight RC bridge piers have been modeled by ABAQUS software under micromechanical model for homogeneous anisotropic fibers. Also the Bilinear Confinement Model by Nonlinear Transition Zone of Mirmiran has been considered. Then types and angles of fibers and their effects on the final responses were evaluated. Finally, effects of retrofitting are evaluated and some suggestions presented.

  8. 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.

  9. Fiber-reinforced Composite for Chairside Replacement of Anterior Teeth: A Case Report.

    PubMed

    Garoushi, S; Vallittu, Pk; Lassila, Lvj

    2008-01-01

    A variety of therapeutic modalities, from implant to conventional Maryland prosthesis, can be used for the replacement of a missing anterior tooth. Whenever a minimal tooth reduction is preferred, a fiber reinforced composite (FRC) prosthesis could be a good alternative to conventional prosthetic techniques, chiefly as temporary restoration before making a final decision on the treatment. The purpose of this case report is to describe the clinical procedure of fabricating anterior chairside FRC prosthesis with pre-impregnated unidirectional E-glass fibers and veneered particulate filler composite. Fiber-reinforced composite in combination with adhesive technology appears to be a promising treatment option for replacing missing teeth. However, further and long-term clinical investigation will be required to provide additional information on the survival of directly-bonded anterior fixed prosthesis made with FRC systems. PMID:21499473

  10. Fiber-reinforced composite fixed partial denture to restore missing posterior teeth: a case report.

    PubMed

    Rappelli, Giorgio; Coccia, Erminia

    2005-11-15

    In patients refusing implant surgery for psychological reasons, when minimal tooth reduction is desired, a fiber-reinforced composite inlay fixed partial denture (IFPD) can be used to replace missing teeth. In comparison to other restorative systems this conservative approach carries a lower risk of pulp exposure and/or periodontal inflammation, maintaining the health of supporting tissues. The purpose of this case report is to describe the clinical procedure for fabricating an IFPD with a pre-impregnated glass fiber system and a hybrid composite. Fiber-reinforced composite, in combination with adhesive techniques, appears promising for an IFPD. Further clinical investigation will be required to provide additional information on this technique. PMID:16299619

  11. Radiation processing of carbon fibre-reinforced advanced composites

    NASA Astrophysics Data System (ADS)

    Singh, Ajit

    2001-12-01

    Carbon fibre-reinforced advanced composites are being used for a variety of structural applications, because of their useful mechanical properties, including high strength-to-weight ratio and corrosion resistance. Thermal curing of composite products results in internal stresses, due to the mismatch of the coefficients of expansion of the tools and the composite products. Because radiation curing can be done at ambient temperatures, the possibility that the residual stresses might be absent, or much lower in the radiation-cured products, originally led to the start of work on radiation curing of advanced composites at AECL's Whiteshell Laboratories in Pinawa, Canada, in 1985. Research work during the last two decades has shown that advanced composites can be radiation-cured with electron beams or γ radiation. Many of the advantages of radiation curing, as compared to thermal curing, which include curing at ambient temperature, reduced curing time, improved resin stability and reduced volatile emissions, have now been demonstrated. The initial work focussed on electron curing of acrylated epoxy matrices. Since then, procedures have been developed to radiation cure conventional aerospace epoxies, as well. Electron beam cured advanced composites are now being developed for use in the aircraft and aerospace industry. Repair of advanced composite structures is also possible using radiation curing technology. Radiation curing work is continuing at Pinawa and has also been done by Aerospatiale, who have facilities for electron curing composite rocket motor casings and by Chappas and co-workers who have electron cured part of a boat hull. In this paper, the work done on this emerging new technology by the various groups is briefly reviewed.

  12. Mycelium reinforced agricultural fiber bio-composites: Summary of research

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Industry and the public sector have a growing interest in utilizing natural fibers, such as agricultural substrates, in the manufacture of components and products currently manufactured from fossil fuels. A patented process, developed by Ecovative Design, LLC (Ecovative), for growing fungal species ...

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    SciTech Connect

    Nguyen Thi, T. B. E-mail: yokoyama@kit.ac.jp; Yokoyama, A. E-mail: yokoyama@kit.ac.jp; Ota, K. E-mail: katsuhiro-kodama@toyobo.jp E-mail: yumiko-isogai@toyobo.jp E-mail: chisato-nonomura@toyobo.jp; Kodama, K. E-mail: katsuhiro-kodama@toyobo.jp E-mail: yumiko-isogai@toyobo.jp E-mail: chisato-nonomura@toyobo.jp; Yamashita, K. E-mail: katsuhiro-kodama@toyobo.jp E-mail: yumiko-isogai@toyobo.jp E-mail: chisato-nonomura@toyobo.jp; Isogai, Y. E-mail: katsuhiro-kodama@toyobo.jp E-mail: yumiko-isogai@toyobo.jp E-mail: chisato-nonomura@toyobo.jp; Furuichi, K. E-mail: katsuhiro-kodama@toyobo.jp E-mail: yumiko-isogai@toyobo.jp E-mail: chisato-nonomura@toyobo.jp; Nonomura, C. E-mail: katsuhiro-kodama@toyobo.jp E-mail: yumiko-isogai@toyobo.jp E-mail: chisato-nonomura@toyobo.jp

    2014-05-15

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

  15. Distributed fiber optic sensors for monitoring reinforced concrete piles using Brillouin scattering

    NASA Astrophysics Data System (ADS)

    de Battista, N.; Kechavarzi, C.; Soga, K.

    2016-05-01

    In this paper we report on advances made in the installation and use of distributed fiber optic sensors to monitor reinforced concrete piles subjected to static load tests. Eight concrete test piles, at three construction sites in London, have recently been instrumented with embedded DFOS. The Brillouin optical time domain reflectometry (BOTDR) technique was used to measure the changes in internal strain and temperature of the piles, during concrete curing and during load testing. These data were used to assess the quality of the pile and derive the load capacity parameters to be used in the foundation design of tall buildings which are to be erected on these sites. The measurements obtained from the DFOS system agreed well with the measurements taken simultaneously using conventional point sensors embedded in the piles. Whereas the conventional sensors only provided measurements at a small number of locations within the piles, the DFOS system made it possible to record the complete strain / temperature profiles along the length of the piles.

  16. Recycling high-performance carbon fiber reinforced polymer composites using sub-critical and supercritical water

    NASA Astrophysics Data System (ADS)

    Knight, Chase C.

    Carbon fiber reinforced plastics (CFRP) are composite materials that consist of carbon fibers embedded in a polymer matrix, a combination that yields materials with properties exceeding the individual properties of each component. CFRP have several advantages over metals: they offer superior strength to weight ratios and superior resistance to corrosion and chemical attack. These advantages, along with continuing improvement in manufacturing processes, have resulted in rapid growth in the number of CFRP products and applications especially in the aerospace/aviation, wind energy, automotive, and sporting goods industries. Due to theses well-documented benefits and advancements in manufacturing capabilities, CFRP will continue to replace traditional materials of construction throughout several industries. However, some of the same properties that make CFRP outstanding materials also pose a major problem once these materials reach the end of service life. They become difficult to recycle. With composite consumption in North America growing by almost 5 times the rate of the US GDP in 2012, this lack of recyclability is a growing concern. As consumption increases, more waste will inevitably be generated. Current composite recycling technologies include mechanical recycling, thermal processing, and chemical processing. The major challenge of CFRP recycling is the ability to recover materials of high-value and preserve their properties. To this end, the most suitable technology is chemical processing, where the polymer matrix can be broken down and removed from the fiber, with limited damage to the fibers. This can be achieved using high concentration acids, but such a process is undesirable due to the toxicity of such materials. A viable alternative to acid is water in the sub-critical and supercritical region. Under these conditions, the behavior of this abundant and most environmentally friendly solvent resembles that of an organic compound, facilitating the breakdown

  17. Mechanical characterization and structural analysis of recycled fiber-reinforced-polymer resin-transfer-molded beams

    NASA Astrophysics Data System (ADS)

    Tan, Eugene Wie Loon

    1999-09-01

    The present investigation was focussed on the mechanical characterization and structural analysis of resin-transfer-molded beams containing recycled fiber-reinforced polymers. The beams were structurally reinforced with continuous unidirectional glass fibers. The reinforcing filler materials consisted entirely of recycled fiber-reinforced polymer wastes (trim and overspray). The principal resin was a 100-percent dicyclo-pentadiene unsaturated polyester specially formulated with very low viscosity for resin transfer molding. Variations of the resin transfer molding technique were employed to produce specimens for material characterization. The basic materials that constituted the structural beams, continuous-glass-fiber-reinforced, recycled-trim-filled and recycled-overspray-filled unsaturated polyesters, were fully characterized in axial and transverse compression and tension, and inplane and interlaminar shear, to ascertain their strengths, ultimate strains, elastic moduli and Poisson's ratios. Experimentally determined mechanical properties of the recycled-trim-filled and recycled-overspray-filled materials from the present investigation were superior to those of unsaturated polyester polymer concretes and Portland cement concretes. Mechanical testing and finite element analyses of flexure (1 x 1 x 20 in) and beam (2 x 4 x 40 in) specimens were conducted. These structurally-reinforced specimens were tested and analyzed in four-point, third-point flexure to determine their ultimate loads, maximum fiber stresses and mid-span deflections. The experimentally determined load capacities of these specimens were compared to those of equivalent steel-reinforced Portland cement concrete beams computed using reinforced concrete theory. Mechanics of materials beam theory was utilized to predict the ultimate loads and mid-span deflections of the flexure and beam specimens. However, these predictions proved to be severely inadequate. Finite element (fracture propagation

  18. Crystallization kinetics and thermal resistance of bamboo fiber reinforced biodegradable polymer composites

    NASA Astrophysics Data System (ADS)

    Thumsorn, S.; Srisawat, N.; On, J. Wong; Pivsa-Art, S.; Hamada, H.

    2014-05-01

    Bamboo fiber reinforced biodegradable polymer composites were prepared in this study. Biodegradable poly(butylene succinate) (PBS) was blended with bamboo fiber in a twin screw extruder with varied bamboo content from 20-0wt%. PBS/bamboo fiber composites were fabricated by compression molding process. The effect of bamboo fiber contents on properties of the composites was investigated. Non-isothermal crystallization kinetic study of the composites was investigated based on Avrami equation. The kinetic parameters indicated that bamboo fiber acted as heterogeneous nucleation and enhanced crystallinity of the composites. Bamboo fiber was well dispersed on PBS matrix and good adhered with the matrix. Tensile strength of the composites slightly deceased with adding bamboo fiber. However, tensile modulus and impact strength of the composites increased when increasing bamboo fiber contents. It can be noted that bamboo fiber promoted crystallization and crystallinity of PBS in the composites. Therefore, the composites were better in impact load transferring than neat PBS, which exhibited improving on impact performance of the composites.

  19. Comparison of Mechanical Properties of Fiber-Reinforced Sand under Triaxial Compression and Direct Shear

    NASA Astrophysics Data System (ADS)

    Noorzad, Reza; Zarinkolaei, Seyed Taher Ghoreyshi

    2015-10-01

    This research investigates the behavior of sand reinforced with polypropylene fiber. To do this, 40 direct shear tests and 40 triaxial tests were performed on the coastal beaches of Babolsar, a city in the North of Iran. The effect of parameters such as fiber content, length of fiber and normal or confining pressure on the behavior of Babolsar sand have been studied. In this study, four various fiber contents (0, 0.25, 0.5 and 1 percent), three different lengths of fiber (6, 12 and 18 mm) and four normal or confining pressures (50, 100, 200 and 400 kPa) have been employed. The test results show that fiber inclusion has a significant effect on the behavior of sand. In both direct shear and triaxial tests, the addition of fibers improved shear strength parameters (C, '), increased peak shear strength and axial strain at failure, and also limited the amount of post-peak reduction in shear resistance. The comparison of the test results revealed that due to better fiber orientation toward the direction of principal tensile strain in triaxial test as compared to direct shear tests, the fiber efficiency and its effect on soil behavior is much more significant in triaxial specimens.

  20. Self-reinforced composites of hydroxyapatite-coated PLLA fibers: fabrication and mechanical characterization.

    PubMed

    Charles, Lyndon F; Kramer, Erica R; Shaw, Montgomery T; Olson, James R; Wei, Mei

    2013-01-01

    Self-reinforced composites (SRCs) are materials where both the matrix and fiber-reinforcing phase are made up of the same polymer. Improved bonding can be achieved with self-reinforced composites compared to traditional dual-polymer, fiber-reinforced composites owing to the identical chemistry of the components in SRCs. Bonding between the fiber and matrix phase is an important factor in applications where mechanical stability is required, such as in the field of bone repair. In this study, we prepared bioabsorbable poly(L-lactic acid)/hydroxyapatite (PLLA/HA) self-reinforced composites via a three-step process that includes surface etching of the fiber, the deposition of the HA coating onto the PLLA fibers through immersion in simulated body fluid (SBF), and hot compaction molding. Although coated with a layer of HA, self-reinforced composites were successfully generated by hot compaction. The effects of compaction time (15 and 30 min), compaction temperature (140, 150, 155, 160, 165, and 170 °C), and HA wt% (0, 5, 10, and 15 wt%) on flexural mechanical properties were studied. Mechanical test results indicated that in unfilled (no HA) PLLA SRCs, compaction time and temperature increased the flexural modulus of the composites tested. Based on the results obtained for unfilled composites, a single compaction time and temperature condition of 15 min and 170 °C were selected to study the effect of HA loading on the composite mechanical properties. HA was successfully loaded onto the fibers at 0, 5, 10, and 15 wt% before hot compaction and was found to significantly increase flexural modulus (P=0.0001). Modulus values ranged from 8.3 GPa±0.5 (0 wt% HA) to 9.7 GPa±0.6 (15 wt% HA). Microscopy results suggest that the HA in these composites forms a nodular-like structure along the fibers, which allows polymer-polymer contact yet prevents longitudinal shear. The procedure used successfully generated composites with flexural moduli near the lower range of bone that may

  1. 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

  2. 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.

  3. 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

  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. Effect of thermal cycling on interface bonding requirements in Al2O3 fiber-reinforced superalloy composites

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1993-01-01

    CTE (coefficient of thermal expansion) mismatch-induced stresses as they affect the fiber-matrix bond integrity of Al2O3 fiber-reinforced superalloy composites are examined. Of the three individual stress components, only the radial stress directly affects the integrity of the fiber-matrix interface. It is noted that a compressive radial stress leads to a clamping action on the fiber and is therefore beneficial to the integrity of the fiber-matrix bond. A radial tensile stress, on the other hand, can cause debonding of the fiber from the matrix for a weak fiber-matrix bond.

  6. Some properties of an advanced boron fiber. [high strength, splittable fibers

    NASA Technical Reports Server (NTRS)

    Behrendt, D. R.

    1979-01-01

    An advanced coreless boron fiber exhibits tensile strengths which are more than twice that of the normal CVD B/W fibers. The coreless fiber is made by the chemical removal of the tungsten boride core exposed by splitting the as-grown fiber. The easily splittable fiber is made by the chemical vapor deposition of boron on a larger than usual tungsten substrate. It is expected that the ease of splitting is related to residual stresses in these fibers. Measurements of the axial residual stresses in both the normal and the splittable fibers are presented and the results compared. Differences in these stresses are discussed in connection with the ease of splitting in the splittable fibers.

  7. Magnesium coated phosphate glass fibers for unidirectional reinforcement of polycaprolactone composites.

    PubMed

    Liu, Xiaoling; Grant, David M; Palmer, Graham; Parsons, Andrew J; Rudd, Chris D; Ahmed, Ifty

    2015-10-01

    Bioresorbable composites have shown much potential for bone repair applications, as they have the ability to degrade completely over time and their degradation and mechanical properties can be tailored to suit the end application. In this study, phosphate glass fiber (from the system 45% P2 O5-16% CaO-24% MgO-11% Na2 O-4% Fe2 O3 (given in mol%)) were used to reinforce polycaprolactone (PCL) with approximately 20% fiber volume fraction. The glass fiber surfaces were coated with magnesium (Mg) through magnetron sputtering to improve the fiber-matrix interfacial properties. The Mg coating provided a rough fiber surface (roughness (Ra) of about 44nm). Both noncoated and Mg-coated fiber-reinforced composites were assessed. The water uptake and mass loss properties for the composites were assessed in phosphate-buffered saline (PBS) at 37°C for up to 28 days, and ion release profiles were also investigated in both water and PBS media. Inhibition of media influx was observed for the Mg-coated composites. The composite mechanical properties were characterized on the basis of both tensile and flexural tests and their retention in PBS media at 37°C was also investigated. A higher retention of the mechanical properties was observed for the Mg-coated composites over the 28 days degradation period.

  8. Aspects regarding wearing behaviour in case of aluminium composite materials reinforced with carbon fibers

    NASA Astrophysics Data System (ADS)

    Caliman, R.

    2016-08-01

    This paper presents a study regarding wear comportment of sintered composite materials obtained by mixture of aluminium with short carbon fibers. The necessity to satisfying more and more the specific functions during design of high performance structures leads to perform multi-materials such as reinforced composite parts. The wear tests were made on three different orientations of fibers on a standard machine of tribology, pin disk type. Counter-disk was made of cast iron with a superficial hardness of 92 HB. The wear rate and friction coefficient decreased exponentially with time of friction and reached a stationary value. This behaviour was attributed to the development of a lubricating film on the friction surface. To conduct this work was performed measurements on samples from the Al matrix composites and carbon fiber 43%, wear mechanism was investigated by scanning electron microscopy. In addition to fiber orientation, the tribological behaviour of metal matrix composites reinforced with fiber is influenced by the interfacial reaction of fiber-matrix. The characteristics and the dimensions of the interface depend on the cycle of temperature and time at which the material has been subjected during the manufacturing process and thereafter.

  9. Properties of fiber reinforced plastics about static and dynamic loadings

    NASA Astrophysics Data System (ADS)

    Kudinov, Vladimir V.; Korneeva, Natalia V.

    2016-05-01

    A method for investigation of impact toughness of anisotropic polymer composite materials (reinforced plastics) with the help of CM model sample in the configuration of microplastic (micro plastic) and impact pendulum-type testing machine under static and dynamic loadings has been developed. The method is called "Break by Impact" (Impact Break IB). The estimation of impact resistance CFRP by this method showed that an increase in loading velocity ~104 times the largest changes occurs in impact toughness and deformation ability of a material.

  10. 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.

  11. Laminate behavior for SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Phillips, Ronald E.

    1990-01-01

    The room temperature mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composite laminates (SiC/RBSN) have been measured. The laminates contained approx 30 volume fraction of aligned 142-micron diameter SiC fiber in a porous RBSN matrix. Three types of laminate studied were unidirectional: (1) (0) sub 8, (2) (10) sub 8, and (3) (45) sub 8, and (90) sub 8; cross plied laminates (0 sub 2/90 sub 2); and angle plied laminates: (+45 sub 2/-45 sub 2). Each laminate contained eight fiber plies. Results of the unidirectionally reinforced composites tested at various angles to the reinforcement direction indicate large anisotropy in in-plane properties. In addition, strength properties of these composites along the fiber direction were independent of specimen gage length and were unaffected by notches normal to the fiber direction. Splitting parallel to the fiber at the notch tip appears to be the dominant crack blunting mechanism responsible for notch insensitive behavior of these composites. In-plane properties of the composites can be improved by 2-D laminate construction. Mechanical property results for (0 sub 2/90 sub 2) sub s and (+45/-45 sub 2) sub s laminates showed that their matrix failure strains were similar to that for (0) sub 8 laminates, but their primary elastic moduli, matrix cracking strengths, and ultimate composite strengths were lower. The elastic properties of unidirectional, cross-ply, and angle-ply composites can be predicted from modified constitutive equations and laminate theory. Further improvements in laminate properties may be achieved by reducing the matrix porosity and by optimizing the bond strength between the SiC fiber and RBSN matrix.

  12. Laminate behavior for SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Rhatt, R. T.; Phillips, R. E.

    1988-01-01

    The room temperature mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composite laminates (SiC/RBSN) have been measured. The laminates contained approx 30 volume fraction of aligned 142-micron diameter SiC fiber in a porous RBSN matrix. Three types of laminate studied were unidirectional: (1) (0) sub 8, (2) (10) sub 8, and (3) (45) sub 8, and (90) sub 8; cross plied laminates (0 sub 2/90 sub 2); and angle plied laminates: (+45 sub 2/-45 sub 2). Each laminate contained eight fiber plies. Results of the unidirectionally reinforced composites tested at various angles to the reinforcement direction indicate large anisotropy in in-plane properties. In addition, strength properties of these composites along the fiber direction were independent of specimen gage length and were unaffected by notches normal to the fiber direction. Splitting parallel to the fiber at the notch tip appears to be the dominant crack blunting mechanism responsible for notch insensitive behavior of these composites. In-plane properties of the composites can be improved by 2-D laminate construction. Mechanical property results for (0 sub 2/90 sub 2)sub s and (+45/-45 sub 2) sub s laminates showed that their matrix failure strains were similar to that for (0) sub 8 laminates, but their primary elastic moduli, matrix cracking strengths, and ultimate composite strengths were lower. The elastic properties of unidirectional, cross-ply, and angle-ply composites can be predicted from modified constitutive equations and laminate theory. Further improvements in laminate properties may be achieved by reducing the matrix porosity and by optimizing the bond strength between the SiC fiber and RBSN matrix.

  13. Characterization of bond in steel-fiber-reinforced cementitious composites under tensile loads

    SciTech Connect

    Namur, G.G.

    1989-01-01

    Investigated was bonding in steel fiber reinforced cementitious composites, like fiber-reinforced mortar. The study was basically analytical, consisting primarily of two analytical models that predict the bond shear stress distribution at the interface between the fibers and the matrix, as well as the normal tensile distributions in the fibers and the matrix. The two models were, however, based on separate assumptions. While the first model assumed a known bond shear stress versus slip relationship at the interface between the fibers and the surrounding matrix, the second model was based on a mechanism of force transfer between the fibers and the matrix, hence circumventing the rather complex task of determining the relationship between the bond stress and the slip for the given type of fiber and matrix. Some applications to this second model, such as the bond modulus, the debonding stress, the length of the debonded zone were also investigated. A theoretical study of the pull-out process of steel fibers in cementitious matrices is included. The problem consisted of relating an idealized bond shear stress versus slip relationship to a pull-out curve. The derivation as based on the assumption that this relationship is linearly elastic-perfectly frictional, and then extended to the case of a fiction decaying linearly with the slip. The problem was subdivided into two components: a primal problem, whereby the pull-out curve is predicted from an assumed bond shear stress-slip relationship, and the dual problem, in which an experimentally obtained pull-out curve was used to predict the interfacial constitutive model, namely the bond-slip curve. Model application was illustrated by three examples of pull-out tests. The pull-out curves obtained in the laboratory, which featured the pull-out force versus the end slip of the pull-out fiber, were used to predict bond shear stress-slip relationships.

  14. Impact Resistance Behaviour of Banana Fiber Reinforced Slabs

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Syamsir, Agusril; Nasharuddin Mustapha, Kamal; Rifdy Samsudin, Muhamad; Thiruchelvam, Sivadass; Usman, Fathoni; Beddu, Salmia; Liyana Mohd Kamal, Nur; Ashraful Alam, Md; Birima, Ahmed H.; Zaroog, O. S.

    2016-03-01

    This paper investigate the performance of banana fibre reinforced slabs 300mm × 300mm size with varied thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.25 kg drop at 1 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the BF contents and slab thickness. A linear relationship has been established between first and ultimate crack resistance against BF contents and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the BF contents for a constant spacing for various banana fibre reinforced slab thickness. The increment in BF content has more effect on the first crack resistance than the ultimate crack resistance. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the various slab thickness. Overall 1.5% BF content with slab thickness of 40 mm exhibit better first and ultimate crack resistance up to 16 times and up to 17 times respectively against control slab (without BF)

  15. Properties of fiber composites for advanced flywheel energy storage devices

    SciTech Connect

    DeTeresa, S J; Groves, S E

    2001-01-12

    The performance of commercial high-performance fibers is examined for application to flywheel power supplies. It is shown that actual delivered performance depends on multiple factors such as inherent fiber strength, strength translation and stress-rupture lifetime. Experimental results for recent stress-rupture studies of carbon fibers will be presented and compared with other candidate reinforcement materials. Based on an evaluation of all of the performance factors, it is concluded that carbon fibers are preferred for highest performance and E-glass fibers for lowest cost. The inferior performance of the low-cost E-glass fibers can be improved to some extent by retarding the stress-corrosion of the material due to moisture and practical approaches to mitigating this corrosion are discussed. Many flywheel designs are limited not by fiber failure, but by matrix-dominated failure modes. Unfortunately, very few experimental results for stress-rupture under transverse tensile loading are available. As a consequence, significant efforts are made in flywheel design to avoid generating any transverse tensile stresses. Recent results for stress-rupture of a carbon fiber/epoxy composite under transverse tensile load reveal that these materials are surprisingly durable under the transverse loading condition and that some radial tensile stress could be tolerated in flywheel applications.

  16. Hydrothermal and mechanical stresses degrade fiber-matrix interfacial bond strength in dental fiber-reinforced composites.

    PubMed

    Bouillaguet, Serge; Schütt, Andrea; Alander, Pasi; Schwaller, Patrick; Buerki, Gerhard; Michler, Johann; Cattani-Lorente, Maria; Vallittu, Pekka K; Krejci, Ivo

    2006-01-01

    Fiber-reinforced composites (FRCs) show great promise as long-term restorative materials in dentistry and medicine. Recent evidence indicates that these materials degrade in vivo, but the mechanisms are unclear. The objective of this study was to investigate mechanisms of deterioration of glass fiber-polymer matrix bond strengths in dental fiber-reinforced composites during hydrothermal and mechanical aging. Conventional three-point bending tests on dental FRCs were used to assess flexural strengths and moduli. Micro push-out tests were used to measure glass fiber-polymer matrix bond strengths, and nanoindentation tests were used to determine the modulus of elasticity of fiber and polymer matrix phases separately. Bar-shaped specimens of FRCs (EverStick, StickTech, and Vectris Pontic, Ivoclar-Vivadent) were either stored at room temperature, in water (37 and 100 degrees C) or subjected to ageing (10(6) cycles, load: 49 N), then tested by three-point bending. Thin slices were prepared for micro push-out and nanoindentation tests. The ultimate flexural strengths of both FRCs were significantly reduced after aging (p < 0.05). Both water storage and mechanical loading reduced the interfacial bond strengths of glass fibers to polymer matrices. Nanoindentation tests revealed a slight reduction in the elastic modulus of the EverStick and Vectris Pontic polymer matrix after water storage. Mechanical properties of FRC materials degrade primarily by a loss of interfacial bond strength between the glass and resin phases. This degradation is detectable by micro push-out and nanoindentation methods.

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

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

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

  18. Sensing uniaxial tensile damage in fiber-reinforced polymer composites using electrical resistance tomography

    NASA Astrophysics Data System (ADS)

    Lestari, Wahyu; Pinto, Brian; La Saponara, Valeria; Yasui, Jennifer; Loh, Kenneth J.

    2016-08-01

    This work describes the application of electrical resistance tomography (ERT) in sensing damage in fiber-reinforced polymer composites under uniaxial quasi-static tension. Damage is manifested as numerous matrix cracks which are distributed across the composite volume and which eventually coalesce into intralayer cracks. Hence, tensile damage is distributed throughout the volume, and could be more significant outside the sensor area. In this work, tensile damage of unidirectional glass fiber-reinforced polymer composites (GFRP) and plain weave carbon fiber-reinforced polymer composites (CFRP) is sensed by utilizing a spray-on nanocomposite sensor, which is then instrumented by boundary electrodes. The resistance change distribution within the sensor area is reconstructed from a series of boundary voltage measurements, and ERT is implemented using a maximum a posteriori approach and assumptions on the type of noise in the reconstruction. Results show that this technique has promise in tracking uniaxial damage in composites. The different fiber architectures (unidirectional GFRP, plain weave CFRP) give distinct features in the ERT, which are consistent with the physical behavior of the tested samples.

  19. Physico-chemical studies of hardened cement paste structure with micro-reinforcing fibers

    NASA Astrophysics Data System (ADS)

    Steshenko, Aleksei; Kudyakov, Aleksander; Konusheva, Viktoriya

    2016-01-01

    The results of physico-chemical studies of modified hardened cement paste with micro-reinforcing fibers are given in this article. The goal was to study the reasons of the increase of strength properties of modified hardened cement paste by the method of X-ray diffraction and electron microscopy. It is shown that the use of mineral fibers in the production of cement based material has positive effect on its properties. The study found out that the increase in the strength of the hardened cement paste with micro-reinforcing fibers is due to the increase of the rate of hydration of cement without a significant change in the phase composition in comparison with hardened cement paste without additive. The results of microstructure investigation (of control samples and samples of the reinforced hardened cement paste) have shown that introduction of mineral fibers in the amount of 0.1-2 % by weight of cement provides the structure of the homogeneous microporous material with uniform distribution of the crystalline phase provided by densely packed hydrates.

  20. Buckling and Vibration of Fiber Reinforced Composite Plates With Nanofiber Reinforced Matrices

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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 for buckling: 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. For vibration the same conditions were used with the applied cods about a small fraction of the buckling loads. The buckling and vibration results showed that the NFRM plates buckled at about twice those with conventional matrix.

  1. Matrix free fiber reinforced polymeric composites via high-temperature high-pressure sintering

    NASA Astrophysics Data System (ADS)

    Xu, Tao

    2004-11-01

    A novel manufacturing process called high-temperature high-pressure sintering was studied and explored. Solid fiber reinforced composites are produced by consolidating and compacting layers of polymeric fabrics near their melting temperature under high pressure. There is no need to use an additional matrix as a bonding material. Partial melting and recrystallization of the fibers effectively fuse the material together. The product is called a "matrix free" fiber reinforced composite and essentially a one-polymer composite in which the fiber and the matrix have the same chemical composition. Since the matrix is eliminated in the process, it is possible to achieve a high fiber volume fraction and light weight composite. Interfacial adhesion between fibers and matrix is very good due to the molecular continuity throughout the system and the material is thermally shapeable. Plain woven Spectra RTM cloth made of SpectraRTM fiber was used to comprehensively study the process. The intrinsic properties of the material demonstrate that matrix free SpectraRTM fiber reinforced composites have the potential to make ballistic shields such as body armor and helmets. The properties and structure of the original fiber and the cloth were carefully examined. Optimization of the processing conditions started with the probing of sintering temperatures by Differential Scanning Calorimetry. Coupled with the information from structural, morphological and mechanical investigations on the samples sintered at different processing conditions, the optimal processing windows were determined to ensure that the outstanding original properties of the fibers translate into high ballistic performance of the composites. Matrix free SpectraRTM composites exhibit excellent ballistic resistance in the V50 tests conducted by the US Army. In the research, process-structure-property relationship is established and correlations between various properties and structures are understood. Thorough knowledge is

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

    SciTech Connect

    Tran, Ngoc Thanh; Tran, Tuan Kiet; Kim, Dong Joo

    2015-03-15

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

  3. Modeling the Tensile Strength of Carbon Fiber - Reinforced Ceramic - Matrix Composites Under Multiple Fatigue Loading

    NASA Astrophysics Data System (ADS)

    Li, Longbiao

    2016-06-01

    An analytical method has been developed to investigate the effect of interface wear on the tensile strength of carbon fiber - reinforced ceramic - matrix composites (CMCs) under multiple fatigue loading. The Budiansky - Hutchinson - Evans shear - lag model was used to describe the micro stress field of the damaged composite considering fibers failure and the difference existed in the new and original interface debonded region. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. The interface shear stress degradation model and fibers strength degradation model have been adopted to analyze the interface wear effect on the tensile strength of the composite subjected to multiple fatigue loading. Under tensile loading, the fibers failure probabilities were determined by combining the interface wear model and fibers failure model based on the assumption that the fiber strength is subjected to two - parameter Weibull distribution and the loads carried by broken and intact fibers satisfy the Global Load Sharing criterion. The composite can no longer support the applied load when the total loads supported by broken and intact fibers approach its maximum value. The conditions of a single matrix crack and matrix multicrackings for tensile strength corresponding to multiple fatigue peak stress levels and different cycle number have been analyzed.

  4. Fiber-content dependency of the optical transparency and thermal expansion of bacterial nanofiber reinforced composites

    NASA Astrophysics Data System (ADS)

    Nogi, Masaya; Ifuku, Shinsuke; Abe, Kentaro; Handa, Keishin; Nakagaito, Antonio Norio; Yano, Hiroyuki

    2006-03-01

    We produced transparent nanocomposite reinforced with bacterial cellulose having a wide range of fiber contents, from 7.4to66.1wt%, by the combination of heat drying and organic solvent exchange methods. The addition of only 7.4wt% of bacterial cellulose nanofibers, which deteriorated light transmittance by only 2.4%, was able to reduce the coefficient of thermal expansion of acrylic resin from 86×10-6to38×10-6K-1. As such, the nanofiber network of bacterial cellulose has an extraordinary potential as a reinforcement to obtain optically transparent and low thermal expansion materials.

  5. Generalized Magneto-thermoelasticity in a Fiber-Reinforced Anisotropic Half-Space

    NASA Astrophysics Data System (ADS)

    Abbas, Ibrahim A.; Abd-alla, Abo-el-nour N.; Othman, Mohamed I. A.

    2011-05-01

    The propagation of plane waves in a fiber-reinforced, anisotropic thermoelastic half-space proposed by Lord-Shulman under the effect of a magnetic field is discussed. The problem has been solved numerically using a finite element method. Numerical results for the temperature distribution, the displacement components, and the thermal stress are given and illustrated graphically. Comparisons are made with the results predicted by the theory of generalized thermoelasticity with one relaxation time for different values of time. It is found that the reinforcement has a great effect on the distribution of field quantities.

  6. Development of multifunctional carbon fiber reinforced composites (CFRCs) - Manufacturing process

    NASA Astrophysics Data System (ADS)

    Guadagno, Liberata; Raimondo, Marialuigia; Vietri, Umberto; Barra, Giuseppina; Vertuccio, Luigi; Volponi, Ruggero; Cosentino, Giovanni; De Nicola, Felice; Grilli, Andrea; Spena, Paola

    2014-05-01

    This work describes a successful attempt toward the development of CFRCs based on nanofilled epoxy resins. The epoxy matrix was prepared by mixing a tetrafunctional epoxy precursor with a reactive diluent which allows to reduce the viscosity of the initial epoxy precursor and facilitate the nanofiller dispersion step. As nanofiller, multiwall carbon nanotubes (MWCNTs) were embedded in the epoxy matrix with the aim of improving the electrical properties of the resin used to manufacture CFRCs. Panels were manufactured by Resin Film Infusion (RFI) using a non-usual technique to infuse a nano-filled resin into a carbon fiber dry preform.

  7. Strong and Tough Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1997-01-01

    Strong, tough and almost fully dense Hi-Nicalon/BN/SiC fiber reinforced celsian matrix composites have been fabricated by impregnation of the fiber tows with the matrix slurry, winding on a drum, stacking the prepreg tapes in the desired orientation, and hot pressing. The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from a mixed oxide precursor. The unidirectional composites having approx. 42 volume percent of fibers exhibited graceful failure with extensive fiber pullout in three-point bend tests at room temperature. Values of first matrix cracking stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01 %, respectively, and ultimate strengths of 900 +/- 60 MPa were observed. The Young's modulus of the composites was 165 +/- 5 GPa.

  8. Load-Bearing Capacity of Fiber-Reinforced Composite Abutments and One-Piece Implants.

    PubMed

    Etxeberria, Marina; Abdulmajeed, Aous A; Escuin, Tomas; Vinas, Miguel; Lassila, Lippo V J; Närhi, Timo O

    2015-06-01

    Fiber-reinforced composites (FRC) can potentially help in a physiologic stress transmission due to its excellent biomechanical matching with living tissues. Novel one-piece FRC implants and abutments with two different fiber orientations were loaded until failure to assess the load-bearing capacity, fracture patterns, and precision of fit. The one-piece FRC implants showed significantly higher load-bearing capacity compared to FRC abutments regardless of the fiber orientation (p < 0.001). For FRC abutments, bidirectional abutments showed significantly higher loads compared to unidirectional abutments (p < 0.001). The type of structure and fiber orientation are strong determinant factors of the load-bearing capacity of FRC implants and abutments. PMID:26373199

  9. Temperature Dependence of Sound Velocity in High-Strength Fiber-Reinforced Plastics

    NASA Astrophysics Data System (ADS)

    Nomura, Ryuji; Yoneyama, Keiichi; Ogasawara, Futoshi; Ueno, Masashi; Okuda, Yuichi; Yamanaka, Atsuhiko

    2003-08-01

    Longitudinal sound velocity in unidirectional hybrid composites or high-strength fiber-reinforced plastics (FRPs) was measured along the fiber axis over a wide temperature range (from 77 K to 420 K). We investigated two kinds of high-strength crystalline polymer fibers, polyethylene (Dyneema) and polybenzobisoxazole (Zylon), which are known to have negative thermal expansion coefficients and high thermal conductivities along the fiber axis. Both FRPs had very high sound velocities of about 9000 m/s at low temperatures and their temperature dependences were very strong. Sound velocity monotonically decreased with increasing temperature. The temperature dependence of sound velocity was much stronger in Dyneema-FRP than in Zylon-FRP.

  10. [Carbon fiber reinforced polysulfone--a new implant material].

    PubMed

    Claes, L

    1989-12-01

    Carbon fibre reinforced polysulfone is a composite material which contains two materials of well known biocompatibility. In comparison to metals this composite material has some advantages which makes it favourable particularly for implants in tumor surgery. The custom made arrangement of fibres in the composite allows the development of implants with special mechanical properties. The radiolucency of the material avoids problems caused by the reflection of x-rays, using metal implants. This special property allows the exact calculation of postoperative radiation doses of tumor patients. Simultaneously the structures behind the implants are not hidden. All implants can be machined during the operation to adapt them to the individual anatomical situation. Animal experimental and clinical applications of plates, screws and spinal segmental replacement implants made of this composite material have shown good results so far.

  11. Development of laminated fiber-reinforced nanocomposites for bone regeneration

    NASA Astrophysics Data System (ADS)

    Xu, Weijie

    There have been numerous efforts to develop synthetic and/or natural tissue engineering scaffolds that are suitable for bone regeneration applications to replace autograft and allograft bones. Current biomaterials as a scaffold for bone regeneration are limited by the extent of degradation concurrent with bone formation, mechanical strength, and the extent of osteogenic differentiation of marrow stromal cells migrating from the surrounding tissues. In this project, a novel laminated nanocomposite scaffold is fabricated, consisting of poly (L-lactide ethylene oxide fumarate) (PLEOF) hydrogel reinforced with poly (L-lactic acid) (PLLA) electrospun nanofibers and hydroxyapatite (HA) nanoparticles. PLEOF is a novel in situ crosslinkable macromer synthesized from biocompatible building units which can be functionalized with bioactive peptides like the cell-adhesive Arg--Gly--Asp (RGD) amino acid sequence. The hydrophilicity and degradation rate of the macromer can be tailored to a particular application by controlling the ratio of PEG to PLA blocks in the macromer and the unsaturated fumarate units can be used for in-situ crosslinking. The PLLA nanofibers were electrospun from high molecular weight PLLA. The laminated nanocomposites were fabricated by dry-hand lay up technique followed by compression molding and thermal crosslinking. The laminated nanocomposites were evaluated with respect to degradation, water uptake, mechanical strength, and the extent of osteogenic differentiation of bone marrow stromal (BMS) cells. Laminates with or without HA nanoparticles showed modulus values much higher than that of trabecular bone (50-100 MPa). The effect of laminated nanocomposites on osteogenic differentiation of BMS cells was determined in terms of cell number, ALPase activity and calcium content. Our results demonstrate that grafting RGD peptide and HA nanoparticles to a PLEOF hydrogel reinforced with PLLA nanofibers synergistically enhance osteogenic differentiation of BMS

  12. Advances in sapphire optical fiber sensors

    NASA Technical Reports Server (NTRS)

    Wang, Anbo; Wang, George Z.; Gollapudi, Sridhar; May, Russell G.; Murphy, Kent A.; Claus, Richard O.

    1993-01-01

    We describe the development and testing of two sapphire fiber sensor designs intended for use in high temperature environments. The first is a birefringence-balanced polarimetric sapphire fiber sensor. In this sensor, two single crystal sapphire rods, acting as the birefringence sensing element, are connected to each other in such a way that the slow axis of the first rod is aligned along with the fast axis of the second rod, and the fast axis of the first rod is along the slow axis of the second rod. This sensor has been demonstrated for measurement of temperature up to 1500 C. The second is a sapphire-fiber-based intrinsic interferometric sensor. In this sensor, a length of uncoated, unclad, structural-graded multimode sapphire fiber is fusion spliced to a singlemode silica fiber to form a Fabry-Perot cavity. The reflections from the silica-to-sapphire fiber splice and the free endface of the sapphire fiber give rise to the interfering fringe output. This sensor has been demonstrated for the measurement of temperature above 1510 C, and a resolution of 0.1 C has been obtained.

  13. Oxidation Behavior of Carbon Fiber-Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Sullivan, Roy M.

    2008-01-01

    OXIMAP is a numerical (FEA-based) solution tool capable of calculating the carbon fiber and fiber coating oxidation patterns within any arbitrarily shaped carbon silicon carbide composite structure as a function of time, temperature, and the environmental oxygen partial pressure. The mathematical formulation is derived from the mechanics of the flow of ideal gases through a chemically reacting, porous solid. The result of the formulation is a set of two coupled, non-linear differential equations written in terms of the oxidant and oxide partial pressures. The differential equations are solved simultaneously to obtain the partial vapor pressures of the oxidant and oxides as a function of the spatial location and time. The local rate of carbon oxidation is determined at each time step using the map of the local oxidant partial vapor pressure along with the Arrhenius rate equation. The non-linear differential equations are cast into matrix equations by applying the Bubnov-Galerkin weighted residual finite element method, allowing for the solution of the differential equations numerically.

  14. Creep rupture testing of carbon fiber-reinforced epoxy composites

    NASA Astrophysics Data System (ADS)

    Burton, Kathryn Anne

    Carbon fiber is becoming more prevalent in everyday life. As such, it is necessary to have a thorough understanding of, not solely general mechanical properties, but of long-term material behavior. Creep rupture testing of carbon fiber is very difficult due to high strength and low strain to rupture properties. Past efforts have included testing upon strands, single tows and overwrapped pressure vessels. In this study, 1 inch wide, [0°/90°]s laminated composite specimens were constructed from fabric supplied by T.D. Williamson Inc. Specimen fabrication methods and gripping techniques were investigated and a method was developed to collect long term creep rupture behavior data. An Instron 1321 servo-hydraulic material testing machine was used to execute static strength and short term creep rupture tests. A hanging dead-weight apparatus was designed to perform long-term creep rupture testing. The testing apparatus, specimens, and specimen grips functioned well. Collected data exhibited a power law distribution and therefore, a linear trend upon a log strength-log time plot. Statistical analysis indicated the material exhibited slow degradation behavior, similar to previous studies, and could maintain a 50 year carrying capacity at 62% of static strength, approximately 45.7 ksi.

  15. Electrospun carbon nanofibers for improved electrical conductivity of fiber reinforced composites

    NASA Astrophysics Data System (ADS)

    Alarifi, Ibrahim M.; Alharbi, Abdulaziz; Khan, Waseem S.; Asmatulu, Ramazan

    2015-04-01

    Polyacrylonitrile (PAN) was dissolved in dimethylformamide (DMF), and then electrospun to generate nanofibers using various electrospinning conditions, such as pump speeds, DC voltages and tip-to-collector distances. The produced nanofibers were oxidized at 270 °C for 1 hr, and then carbonized at 850 °C in an argon gas for additional 1 hr. The resultant carbonized PAN nanofibers were placed on top of the pre-preg carbon fiber composites as top layers prior to the vacuum oven curing following the pre-preg composite curing procedures. The major purpose of this study is to determine if the carbonized nanofibers on the fiber reinforced composites can detect the structural defects on the composite, which may be useful for the structural health monitoring (SHM) of the composites. Scanning electron microscopy images showed that the electrospun PAN fibers were well integrated on the pre-preg composites. Electrical conductivity studies under various tensile loads revealed that nanoscale carbon fibers on the fiber reinforced composites detected small changes of loads by changing the resistance values. Electrically conductive composite manufacturing can have huge benefits over the conventional composites primarily used for the military and civilian aircraft and wind turbine blades.

  16. Recycled and virgin plastics in fiber reinforced concrete. Final report, October 1994--August 1997

    SciTech Connect

    Tawfiq, K.S.

    1998-08-30

    The primary objectives of this study is to conduct a laboratory investigation to evaluate the intrinsic stress that can cause cracking of concrete mixed recommended by the Florida Department of Transportation with the addition of monofilament and fibrillated polypropylene and monofilament polyolefin fibers, subjected to highly cyclic loading. In addition, the flexural behavior of concrete reinforced with recycled post-consumer in-house made fibers will be study and Finite Element Methods (FEM) following laboratory work would be used to establish comparable numerical models for the flexural test and pavement overlays.

  17. Tribological properties of graphite-fiber-reinforced, partially fluorinated polyimide composites

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.; Hady, W. F.

    1985-01-01

    Graphite-fiber-reinforced polyimide (GFRPI) composites were formulated from three new partially fluorinated polyimides and three types of graphite fiber. Nine composites were molded into pins and evaluated in a pin-on-disk tribometer. Friction coefficients, wear rates, pin wear surface morphology, and transfer film formation were assessed at 25 and 300 C. Also assessed was the effect of sliding speed on friction. Wear was up to two orders of magnitude lower at 25 C and up to one order of magnitude lower at 300 C than with previously formulated NASA GFRPI composites.

  18. Tribological properties of graphite-fiber-reinforced, partially fluorinated polyimide composites

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.; Hady, W. F.

    1986-01-01

    Graphite-fiber-reinforced polyimide (GFRPI) composites were formulated from three new partially fluorinated polyimides and three types of graphite fiber. Nine composites were molded into pins and evaluated in a pin-on-disk tribometer. Friction coefficients, wear rates, pin wear surface morphology, and transfer film formation were assessed at 25 and 300 C. Also assessed was the effect of sliding speed on friction. Wear was up to two orders of magnitude lower at 25 C and up to one order of magnitude lower at 300 C than with previously formulated NASA GFRPI composites.

  19. Method of producing a silicon carbide fiber reinforced strontium aluminosilicate glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P. (Inventor)

    1995-01-01

    A SrO-Al2O3-2SrO2 (SAS) glass ceramic matrix is reinforced with CVD SiC continuous fibers. This material is prepared by casting a slurry of SAS glass powder into tapes. Mats of continuous CVD-SiC fibers are alternately stacked with the matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite. Organic constituents are burned out of the 'green' composite, and the remaining interim material is hot pressed.

  20. Silicon carbide fiber reinforced strontium aluminosilicate glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam (Inventor)

    1992-01-01

    A SrO-Al2O3 - 2SrO2 (SAS) glass ceramic matrix is reinforced with CVD SiC continuous fibers. This material is prepared by casting a slurry of SAS glass powder into tapes. Mats of continuous CVD-SiC fibers are alternately stacked with the matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite. Organic constituents are burned out of the 'green' composite, and the remaining interim material is hot pressed.

  1. Thermal Properties of Capparis Decidua (ker) Fiber Reinforced Phenol Formaldehyde Composites

    SciTech Connect

    Singh, G. P.; Mangal, Ravindra; Bhojak, N.; Dixit, Manasvi; Saxena, N. S.

    2010-06-29

    Simultaneous measurement of effective thermal conductivity ({lambda}), effective thermal diffusivity ({kappa}) and specific heat of Ker fiber reinforced phenol formaldehyde composites have been studied by transient plane source (TPS) technique. The samples of different weight percentage typically (5, 10, 15, 20 and 25%) have been taken. It is found that values of effective thermal conductivity and effective thermal diffusivity of the composites decrease, as compared to pure phenol formaldehyde, as the fraction of fiber loading increases. Experimental data is fitted on Y. Agari model. Values of thermal conductivity of composites are calculated with two models (Rayleigh, Maxwell and Meredith-Tobias model). Good agreement between theoretical and experimental result has been found.

  2. Processing and characterization of natural fiber reinforced thermoplastic composites using micro-braiding technique

    NASA Astrophysics Data System (ADS)

    Kobayashi, Satoshi; Ogihara, Shinji

    In the present study, we investigate fatigue properties of green composites. A hemp fiber yarn reinforced poly(lactic acid) composite was selected as a green composite. Unidirectional (UD) and textile (Textile) composites were fabricated using micro-braiding technique. Fatigue tests results indicated that fatigue damages in UD composites was splitting which occurred just before the final fracture, while matrix crack and debonding between matrix and fiber yarn occurred and accumulated stably in Textile composites. These results were consistent with modulus reduction and acoustic emission measurement during fatigue tests.

  3. Evaluation of residual strength in the basalt fiber reinforced composites under impact damage

    NASA Astrophysics Data System (ADS)

    Kim, Yun-Hae; Lee, Jin-Woo; Moon, Kyung-Man; Yoon, Sung-Won; Baek, Tae-Sil; Hwang, Kwang-Il

    2015-03-01

    Composites are vulnerable to the impact damage by the collision as to the thickness direction, because composites are being manufactured by laminating the fiber. The understanding about the retained strength after the impact damage of the material is essential in order to secure the reliability of the structure design using the composites. In this paper, we have tried to evaluate the motion of the material according to the kinetic energy and potential energy and the retained strength after impact damage by testing the free fall test of the basalt fiber reinforced composite in the limelight as the environment friendly characteristic.

  4. Model for the Effect of Fiber Bridging on the Fracture Resistance of Reinforced-Carbon-Carbon

    NASA Technical Reports Server (NTRS)

    Chan, Kwai S.; Lee, Yi-Der; Hudak, Stephen J., Jr.

    2009-01-01

    A micromechanical methodology has been developed for analyzing fiber bridging and resistance-curve behavior in reinforced-carbon-carbon (RCC) panels with a three-dimensional (3D) composite architecture and a silicon carbide (SiC) surface coating. The methodology involves treating fiber bridging traction on the crack surfaces in terms of a weight function approach and a bridging law that relates the bridging stress to the crack opening displacement. A procedure has been developed to deduce material constants in the bridging law from the linear portion of the K-resistance curve. This report contains information on the application of procedures and outcomes.

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

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2015-12-01

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

  6. Network model for thermal conductivities of unidirectional fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Peng, Chaoyi; Zhang, Weihua

    2014-12-01

    An empirical network model has been developed to predict the in-plane thermal conductivities along arbitrary directions for unidirectional fiber-reinforced composites lamina. Measurements of thermal conductivities along different orientations were carried out. Good agreement was observed between values predicted by the network model and the experimental data; compared with the established analytical models, the newly proposed network model could give values with higher precision. Therefore, this network model is helpful to get a wider and more comprehensive understanding of heat transmission characteristics of fiber-reinforced composites and can be utilized as guidance to design and fabricate laminated composites with specific directional or specific locational thermal conductivities for structures that simultaneously perform mechanical and thermal functions, i.e. multifunctional structures (MFS).

  7. Effect of Initial Stress on a Fiber-Reinforced Anisotropic Thermoelastic Thick Plate

    NASA Astrophysics Data System (ADS)

    Abbas, Ibrahim A.; Abd-alla, Abo-el-nour N.

    2011-05-01

    The two-dimensional problem of generalized thermoelasticity for a fiber-reinforced anisotropic thick plate under initial stress is studied in the context of the Lord and Shulman theory. The upper surface of the plate is thermally insulated with prescribed surface loading while the lower surface of the plate rests on a rigid foundation and temperature. The problem is solved numerically using a finite element method. Numerical results for the temperature distribution, and the displacement and stress components are given and illustrated graphically. It is found from the graphs that the initial stress significantly influences the variations of field quantities. The results obtained in this paper may offer a theoretical basis and meaningful suggestions for the design of various fiber-reinforced anisotropic thermoelastic elements under loading to meet special engineering requirements.

  8. Microwave excitation of ultrasound in graphite-fiber reinforced composite plates.

    PubMed

    Guilliorit, Emmanuel; Hosten, Bernard; Bacon, Christophe; Chimenti, D E

    2003-03-01

    In this paper is demonstrated the effect of microwave beam polarization on the thermal generation of acoustic waves in continuous fiber-reinforced composite laminates. It is found that beam polarization strongly influences the dielectric interaction that leads to thermal losses, bulk expansion, and acoustic wave generation. The oriented graphite fibers in the composite laminate effectively short the microwave fields and reduce the generation efficiency nearly to zero. Ultrasonic waves at several hundred kHz generated in the composite are detected by air-coupled acoustic transducers located on the opposite side of the plate specimen from the 9.41 GHz incident microwave beam. With some averaging signal-to-noise ratios of better than 26 dB are obtained. Applying a conventional model of electromagnetic wave scattering in anisotropic media to this experiment yields good agreement between calculations and measured data. Implications for microwave-acoustic testing of graphite-reinforced composites are also discussed. PMID:12565073

  9. Tensile creep and creep fracture of a fiber-reinforced SiC/SiC composite

    SciTech Connect

    Wilshire, B.; Carreno, F.; Percival, M.J.L.

    1998-08-11

    Several studies have been completed on silicon carbide fiber-reinforced silicon carbide (SiC{sub f}/SiC) composites produced with carbon-coated fibres having a 0/90{degree} architecture. Yet, while mechanical property measurements have been made at temperatures up to 1,473K in air and argon high-temperature creep tests have been carried out only under protective atmospheres. To clarify the creep behavior patterns displayed by continuous-fiber-reinforced CMCs, while simultaneously providing information relevant to aeroengine turbine design, the tensile creep and creep fracture properties of a 0/90{degree} SiC{sub f}/SiC composite have been determined over a stress range giving creep rupture lives up to approximately 2,000 hours in air at 1,573K.

  10. 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.

  11. Prediction of plastic deformation of fiber-reinforced copper matrix composites

    NASA Astrophysics Data System (ADS)

    You, J. H.; Bolt, H.

    2002-12-01

    Copper alloys have been considered as a structural material for the heat sink of the actively cooled plasma facing components due to its high thermal conductivity. However, the decrease of strength at elevated temperatures and their large thermal expansion are detrimental aspects. The fiber-reinforced copper matrix composites (FRCMC) can be a potential candidate as heat sink material. In this article, the non-linear constitutive behavior of the FRCMCs reinforced with continuous SiC fibers is predicted. To this end, a simulation tool was developed using analytical micro-mechanics theory. The effects of thermal residual stress and of the matrix flow stress are estimated. The results show that these composites have a significantly increased work-hardening rate compared to the unreinforced matrix metals. The thermal residual stress has a marked influence on the initial yield surface as well as on the stress-strain curve showing asymmetry in tension and compression.

  12. Bioactive Glass Fiber Reinforced Starch-Polycaprolactone Composite for Bone Applications

    NASA Astrophysics Data System (ADS)

    Jukola, H.; Nikkola, L.; Gomes, M. E.; Chiellini, F.; Tukiainen, M.; Kellomäki, M.; Chiellini, E.; Reis, R. L.; Ashammakhi, N.

    2008-02-01

    For bone regeneration and repair, combinations of different materials are often needed. Biodegradable polymers are often combined with osteoconductive materials, such as bioactive glass (BaG), which can also improve the mechanical properties of the composite. The aim of this study was to develop and characterize BaG fiber-reinforced starch-poly-ɛ-caprolactone (SPCL) composite. Sheets of SPCL (30/70 wt%) were produced using single-screw extrusion. They were then cut and compression molded in layers with BaG fibers to form composite structures of different combinations. Thermal, mechanical, and degradation properties of the composites were studied. The actual amount of BaG in the composites was determined using combustion tests. A strong endothermic peak indicating melting at about 56 °C was observed by differential scanning calorimetry (DSC) analysis. Thermal gravimetry analysis (TGA) showed that thermal decomposition of SPCL started at 325 °C with the decomposition of starch and continued at 400 °C with the degradation of polycaprolactone (PCL). Initial mechanical properties of the reinforced composites were at least 50% better than the properties of the non-reinforced composites. However, the mechanical properties of the composites after two weeks of hydrolysis were comparable to those of the non-reinforced samples. During the six weeks' hydrolysis the mass of the composites had decreased only by about 5%. The amount of glass in the composites remained the same for the six-week period of hydrolysis. In conclusion, it is possible to enhance the initial mechanical properties of SPCL by reinforcing it with BaG fibers. However, the mechanical properties of the composites are only sufficient for use as filler material and they need to be further improved to allow long-lasting bone applications.

  13. Bioactive Glass Fiber Reinforced Starch-Polycaprolactone Composite for Bone Applications

    SciTech Connect

    Jukola, H.; Nikkola, L.; Tukiainen, M.; Kellomaeki, M.; Ashammakhi, N.; Gomes, M. E.; Reis, R. L.; Chiellini, F.; Chiellini, E.

    2008-02-15

    For bone regeneration and repair, combinations of different materials are often needed. Biodegradable polymers are often combined with osteoconductive materials, such as bioactive glass (BaG), which can also improve the mechanical properties of the composite. The aim of this study was to develop and characterize BaG fiber-reinforced starch-poly-{epsilon}-caprolactone (SPCL) composite. Sheets of SPCL (30/70 wt%) were produced using single-screw extrusion. They were then cut and compression molded in layers with BaG fibers to form composite structures of different combinations. Thermal, mechanical, and degradation properties of the composites were studied. The actual amount of BaG in the composites was determined using combustion tests. A strong endothermic peak indicating melting at about 56 deg. C was observed by differential scanning calorimetry (DSC) analysis. Thermal gravimetry analysis (TGA) showed that thermal decomposition of SPCL started at 325 deg. C with the decomposition of starch and continued at 400 deg. C with the degradation of polycaprolactone (PCL). Initial mechanical properties of the reinforced composites were at least 50% better than the properties of the non-reinforced composites. However, the mechanical properties of the composites after two weeks of hydrolysis were comparable to those of the non-reinforced samples. During the six weeks' hydrolysis the mass of the composites had decreased only by about 5%. The amount of glass in the composites remained the same for the six-week period of hydrolysis. In conclusion, it is possible to enhance the initial mechanical properties of SPCL by reinforcing it with BaG fibers. However, the mechanical properties of the composites are only sufficient for use as filler material and they need to be further improved to allow long-lasting bone applications.

  14. Crack bridging in fiber reinforced cementitious composites with slip-hardening interfaces

    NASA Astrophysics Data System (ADS)

    Lin, Zhong; Li, Victor C.

    1997-05-01

    A new crack bridging model accounting for slip-hardening interfacial shear stress is derived for randomly oriented discontinuous flexible fibers in cement-based composites, based on a micromechanics analysis of single fiber pull-out. The complete composite bridging stress versus crack opening curve ( σB - δ relation) and associated fracture energy are theoretically determined. A micromechanics-based criterion which governs the existence of post-debonding rising branch of the σB - δ curve is obtained. Implications of the present model on various composite properties, including uniaxial tensile strength, flexural strength, ductility and critical fiber volume fraction for strain-hardening, are discussed together with an example of a 2% polyethylene fiber reinforced cement composite. It is found that the present model can very well describe the slip-hardening behavior during fiber pull-out which originates from fiber surface abrasion at fiber/matrix interface. In addition, the new model predicts accurately the enhanced toughness in terms of both ultimate tensile strain and fracture energy of the composite and resolves the deficiency of constant interface shear stress model in predicting the crack opening and ultimate strain, which are critical for material design of pseudo strain hardening engineered cementitious composites (ECCs).

  15. Alignment of carbon nanotubes and reinforcing effects in nylon-6 polymer composite fibers

    NASA Astrophysics Data System (ADS)

    Rangari, Vijaya K.; Yousuf, Mohammed; Jeelani, Shaik; Pulikkathara, Merlyn X.; Khabashesku, Valery N.

    2008-06-01

    Alignment of pristine carbon nanotubes (P-CNTs) and fluorinated carbon nanotubes (F-CNTs) in nylon-6 polymer composite fibers (PCFs) has been achieved using a single-screw extrusion method. CNTs have been used as filler reinforcements to enhance the mechanical and thermal properties of nylon-6 composite fibers. The composites were fabricated by dry mixing nylon-6 polymer powder with the CNTs as the first step, then followed by the melt extrusion process of fiber materials in a single-screw extruder. The extruded fibers were stretched to their maxima and stabilized using a godet set-up. Finally, fibers were wound on a Wayne filament winder machine and tested for their tensile and thermal properties. The tests have shown a remarkable change in mechanical and thermal properties of nylon-6 polymer fibers with the addition of 0.5 wt% F-CNTs and 1.0 wt% of P-CNTs. To draw a comparison between the improvements achieved, the same process has been repeated with neat nylon-6 polymer. As a result, tensile strength has been increased by 230% for PCFs made with 0.5% F-CNTs and 1% P-CNTs as additives. These fibers have been further characterized by DSC, Raman spectroscopy and SEM which confirm the alignment of CNTs and interfacial bonding to nylon-6 polymer matrix.

  16. Investigations on Thermal Conductivities of Jute and Banana Fiber Reinforced Epoxy Composites

    NASA Astrophysics Data System (ADS)

    Pujari, Satish; Ramakrishna, Avasarala; Balaram Padal, Korabu Tulasi

    2016-01-01

    The Jute and Banana fibers are used as reinforcement in epoxy resin matrix for making partially green biodegradable material composite via hand lay-up technique. The thermal conductivity of the jute fiber epoxy composites and banana fiber epoxy composites at different volume fraction of the fiber is determined experimentally by using guarded heat flow meter method. The experimental results had shown that thermal conductivity of the composites decrease with an increase in the fiber content. Experimental results are compared with theoretical models (Series model, Hashin model and Maxwell model) to describe the variation of the thermal conductivity versus the volume fraction of the fiber. Good agreement between theoretical and experimental results is observed. Thermal conductivity of Banana fiber composite is less when compared to that of Jute composite which indicates banana is a good insulator and also the developed composites can be used as insulating materials in building, automotive industry and in steam pipes to save energy by reducing rate of heat transfer.

  17. Fiber Reinforced Polyester Resins Polymerized by Microwave Source

    NASA Astrophysics Data System (ADS)

    Visco, A. M.; Calabrese, L.; Cianciafara, P.; Bonaccorsi, L.; Proverbio, E.

    2007-12-01

    Polyester resin based composite materials are widely used in the manufacture of fiberglass boats. Production time of fiberglass laminate components could be strongly reduced by using an intense energy source as well as microwaves. In this work a polyester resin was used with 2% by weight of catalyst and reinforced with chopped or woven glass fabric. Pure resin and composite samples were cured by microwaves exposition for different radiation times. A three point bending test was performed on all the cured samples by using an universal testing machine and the resulting fracture surfaces were observed by means of scanning electron microscopy (SEM). The results of mechanical and microscopy analyses evidenced that microwave activation lowers curing time of the composite while good mechanical properties were retained. Microwaves exposition time is crucial for mechanical performance of the composite. It was evidenced that short exposition times suffice for resin activation while long exposure times cause fast cross linking and premature matrix fracture. Furthermore high-radiation times induce bubbles growth or defects nucleation within the sample, decreasing composite performance. On the basis of such results microwave curing activation of polyester resin based composites could be proposed as a valid alternative method for faster processing of laminated materials employed for large-scale applications.

  18. Thermal characterization and tomography of carbon fiber reinforced plastics using individual identification technique

    SciTech Connect

    Vavilov, V.P.; Grinzato, E.; Bison, P.G.; Marinetti, S.; Bressan, C.

    1996-05-01

    A method for thermal characterization of defect depth and thickness using individual inversion functions is described. Experimental results are obtained with standard carbon fiber reinforced plastic specimens which contained Teflon inserts and impact damage. Accuracy in determining defect dimensions was about 10 percent for defect depth and 33 percent for defect thickness. A technique to synthesize images of defect parameters is proposed. Thermal tomography advantages in analyzing defect in-depth propagation are illustrated.

  19. Coded excitation for infrared non-destructive testing of carbon fiber reinforced plastics.

    PubMed

    Mulaveesala, Ravibabu; Venkata Ghali, Subbarao

    2011-05-01

    This paper proposes a Barker coded excitation for defect detection using infrared non-destructive testing. Capability of the proposed excitation scheme is highlighted with recently introduced correlation based post processing approach and compared with the existing phase based analysis by taking the signal to noise ratio into consideration. Applicability of the proposed scheme has been experimentally validated on a carbon fiber reinforced plastic specimen containing flat bottom holes located at different depths.

  20. Ultrasonic velocity technique for monitoring property changes in fiber-reinforced ceramic matrix composites

    NASA Technical Reports Server (NTRS)

    Kautz, Harold E.; Bhatt, Ramakrishna T.

    1991-01-01

    A technique for measuring ultrasonic velocity was used to monitor changes that occur during processing and heat treatment of a SiC/RBSM composite. Results indicated that correlations exist between the ultrasonic velocity data and elastic modulus and interfacial shear strength data determined from mechanical tests. The ultrasonic velocity data can differentiate strength. The advantages and potential of this nondestructive evaluation method for fiber reinforced ceramic matrix composite applications are discussed.

  1. Space maintainer using fiber-reinforced composite and natural tooth--a non-invasive technique.

    PubMed

    Tayab, Tabassum; Vizhi, Kayal; Srinivasan, Ila

    2011-04-01

    Dental traumatic injuries are widespread in the population and are a frequent pathology among children and teenagers. Dentists and especially pediatric dentists are commonly confronted with managing dental crown root fractures on a regular basis. Fiber-reinforced composite (FRC) have been used as an alternative to conventional space maintainers in pediatric dentistry. We present here a case of a 11-year-old boy with oblique crown root fracture, treated by placing extracted natural crown with FRC as space maintainer.

  2. Effects of high energy radiation on the mechanical properties of epoxy graphite fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Gilbert, R. D.; Fornes, R. E.; Memory, J. D.

    1983-01-01

    The effects of high energy radiation on mechanical properties and on the molecular and structural properties of graphite fiber reinforced composites are assessed so that durability in space applications can be predicted. A listing of composite systems irradiated along with the maximum radiation dose applied and type of mechanical tests performed is shown. These samples were exposed to 1/2 MeV electrons.

  3. Replacement of missing teeth with fiber-reinforced composite FPDs: clinical protocol.

    PubMed

    Bouillaguet, Serge; Schütt, Andrea; Marin, Isabelle; Etechami, Leila; Di Salvo, Giancarlo; Krejci, Ivo

    2003-04-01

    The concept of minimally invasive preparation protocols has resulted in reduced loss of critical tooth structures and maintenance of optimal strength, form, and aesthetics. While various treatment options have been described for single-tooth replacement, fiber-reinforced composite (FRC) fixed partial dentures (FPDs) provide a viable treatment alternative with proven mechanical properties, aesthetics, and function. This article presents several clinical scenarios in which minimally invasive adhesive FRC FPDs are provided to deliver enhanced predictability, strength, and durability. PMID:12956045

  4. Single visit replacement of maxillary canine using fiber-reinforced composite resin.

    PubMed

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

    2012-01-01

    Missing a canine is of serious concern in social life of a patient in most of societies. While conventional fixed partial dentures and implant-supported restorations may often be the treatment of choice, fiber-reinforced composite (FRC) resins offer a conservative, fast and cost-effective alternative for single and multiple teeth replacement. This clinical report presents two cases where FRC technology was successfully used to restore canine edentulous area in terms of esthetic-cosmetic values and functionality. PMID:22430706

  5. Fiber-reinforced composite anterior bridge in pediatric traumatology: clinical considerations.

    PubMed

    Chafaie, Amir; Dahan, Serge; Le Gall, Michel

    2013-12-01

    This article describes the protocol for creation of a fiber-reinforced composite bridge for temporary treatment of traumatic tooth loss affecting young adult dentition. This non-invasive solution is justified by the time lapse between the end of orthodontic treatment and the moment when the state of maturity of the various tissues makes it possible to install a conventional or implant-based prosthesis. PMID:24144520

  6. Reinforcement of asphalt concrete pavement by segments of exhausted fiber used for sorption of oil spill

    NASA Astrophysics Data System (ADS)

    Lukashevich, V. N.; Efanov, I. N.

    2015-01-01

    The paper is aimed at construction of the experimental road pavement made of dispersed reinforced asphalt concrete. Electronic paramagnetic resonance, infrared spectroscopy and fluorescent bitumen studies were used to prove that disperse reinforcement of asphalt concrete mixtures with fibers of exhausted sorbents reduce the selective filtration of low polymeric fractions of petroleum bitumen and improve its properties in the adsorption layer. Sesquioxides are neutralized as catalysts aging asphalt binder. This leads to improvement in the elasticity of bitumen films at low temperatures and provide better crack resistance of coatings to reduce the intensity of the aging of asphalt binder, and, therefore, to increase the durability of road pavements. The experimental road pavement made of dispersed reinforced asphalt concrete operated during 4 years and demonstrated better transport- performance properties in comparison with the analogue pavements.

  7. Lincoln Advanced Science and Engineering Reinforcement (LASER) program

    NASA Astrophysics Data System (ADS)

    Williams, Willie E.

    Lincoln University, under the Lincoln Advanced Science and Engineering Reinforcement (LASER) Program, has identified and successfully recruited over 100 students for majors in technical fields. To date, over 70 percent of these students have completed or will complete technical degrees in engineering, physics, chemistry, and computer science. Of those completing the undergraduate degree, over 40 percent have gone on to graduate and professional schools. This success is attributable to well planned approaches to student recruitment, training, personal motivation, retention, and program staff. Very closely coupled to the above factors is a focus designed to achieve excellence in program services and student performance. Future contributions by the LASER Program to the pool of technical minority graduates will have a significant impact. This is already evident from the success of the students that began the first year of the program. With program plans to refine many of the already successful techniques, follow-on activities are expected to make even greater contributions to the availability of technically trained minorities. For example, undergraduate research exposure, broadened summer, and co-op work experiences will be enhanced.

  8. Orbiter Reinforced Carbon-Carbon Advanced Sealant Systems: Screening Tests

    NASA Technical Reports Server (NTRS)

    Curry, Donald M.; Lewis, Ronad K.; Norman, Ignacio; Chao, Dennis; Nicholson, Leonard S. (Technical Monitor)

    2000-01-01

    Oxidation protection for the Orbiter reinforced carbon-carbon (RCC consists of three components: silicon carbide coating, tetraethyl orthosilicate (TEOS) impregnated into the carbon substrate and a silicon based surface sealant (designated Type A). The Orbiter Type A sealant is being consumed each mission, which results in increased carbon-carbon substrate mass loss, which adversely impacts the mission life of the RCC components. In addition, the sealant loss in combination with launch pad contamination (salt deposit and zinc oxide) results in RCC pinholes. A sealant refurbishment schedule to maintain mission life and minimize affects of pin hole formation has been implemented in the Orbiter maintenance schedule. The objective of this investigation is to develop an advanced sealant system for the RCC that extends the refurbishment schedule by reducing sealant loss/pin hole formation and that can be applied to existing Orbiter RCC components. This paper presents the results of arc jet screening tests conducted on several sealants that are being considered for application to the Orbiter RCC.

  9. Lincoln Advanced Science and Engineering Reinforcement (LASER) program

    NASA Technical Reports Server (NTRS)

    Williams, Willie E.

    1989-01-01

    Lincoln University, under the Lincoln Advanced Science and Engineering Reinforcement (LASER) Program, has identified and successfully recruited over 100 students for majors in technical fields. To date, over 70 percent of these students have completed or will complete technical degrees in engineering, physics, chemistry, and computer science. Of those completing the undergraduate degree, over 40 percent have gone on to graduate and professional schools. This success is attributable to well planned approaches to student recruitment, training, personal motivation, retention, and program staff. Very closely coupled to the above factors is a focus designed to achieve excellence in program services and student performance. Future contributions by the LASER Program to the pool of technical minority graduates will have a significant impact. This is already evident from the success of the students that began the first year of the program. With program plans to refine many of the already successful techniques, follow-on activities are expected to make even greater contributions to the availability of technically trained minorities. For example, undergraduate research exposure, broadened summer, and co-op work experiences will be enhanced.

  10. Adhesion bonding techniques for highly loaded parts of continuous carbon-fiber reinforced polyetheretherketone (CF-PEEK/APC2)

    NASA Astrophysics Data System (ADS)

    Kempe, G.; Krauss, H.

    It is shown that the adhesion technology is applicable to the bonding of continuous fiber reinforced thermplastics. The influences and conditions under which an enhancement of the bonding strength can be achieved are described. Attention is focused on the applicability of the adhesion method to continuous fiber reinforced PEEK, acknowledging that PEEK is very resistant to chemicals and thereby, a poor candidate for the technique.

  11. Ballistic impact damage and penetration mechanics of fiber-reinforced composite laminates

    NASA Astrophysics Data System (ADS)

    Patts, Henry Michael

    2000-10-01

    Experimental and theoretical studies were performed to characterize and model the processes of damage evolution and resulting penetration failure of graphite fiber-reinforced epoxy resin composite laminates ("structural grade") under ballistic impact. In contrast to the local yielding demonstrated by ductile isotropic materials, the penetration failure of fiber-reinforced composites produced extensive fragmentation of material with multiple modes of damage propagation such as "delamination," "interfiber matrix splitting," "transverse fiber cuts," and "through-the-thickness plugging." Due to the formation of damage zones in three-dimensional scale, the increase in target thickness raised the amount of kinetic energy absorption for full penetration in a "non-linear" fashion in fiber composites unlike the linear correlation for isotropic material such as polycarbonate and aluminum. Interfiber matrix splitting and delamination were found to be the first sign of structural deterioration occurring far below V50 and precede transverse cutting of fibers and plugging. The development of interfiber splitting into delamination of composites is explained by relying on the contact mechanics of a spherical indentor. Matrix splits on adjacent plies formed one pair of geometrical "wedges" at the ply interface, resulting in a delamination zone connected through an "isthmus." Contained in this free ply region, stress concentration readily led to transverse cutting (approximately at 85 percent of the V50) of plies when longitudinal stress of the reinforcing fibers reaches a critical level for fracture. The observed distribution of the damage leading to transverse fiber cuts was modeled by idealizing a circular target panel of staircase laminate into three zones with different values of bending stiffness due to the progression of damage. In "three-zone" model, the energy absorbed by the panel were represented in three forms of potential energy; surface free energy due to delamination

  12. Low Cost Fabrication of Silicon Carbide Based Ceramics and Fiber Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Singh, M.; Levine, S. R.

    1995-01-01

    A low cost processing technique called reaction forming for the fabrication of near-net and complex shaped components of silicon carbide based ceramics and composites is presented. This process consists of the production of a microporous carbon preform and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture with very good control of pore volume and pore size thereby yielding materials with tailorable microstructure and composition. Mechanical properties (elastic modulus, flexural strength, and fracture toughness) of reaction-formed silicon carbide ceramics are presented. This processing approach is suitable for various kinds of reinforcements such as whiskers, particulates, fibers (tows, weaves, and filaments), and 3-D architectures. This approach has also been used to fabricate continuous silicon carbide fiber reinforced ceramic composites (CFCC's) with silicon carbide based matrices. Strong and tough composites with tailorable matrix microstructure and composition have been obtained. Microstructure and thermomechanical properties of a silicon carbide (SCS-6) fiber reinforced reaction-formed silicon carbide matrix composites are discussed.

  13. Fiber-reinforced Composite Resin Bridge: A Treatment Option in Children

    PubMed Central

    Yelluri, Rama Krishna; Munshi, AK

    2015-01-01

    ABSTRACT A number of treatment options, ranging from Maryland bridges to implants, are available for the replacement of congenitally or traumatically missing permanent anterior teeth. But, there are several limitations of these therapeutic options when they have to be used before the completion of the growth, particularly in children. Reinforcement of composite resins with polyethylene fibers significantly improves their mechanical properties. Fiber-reinforced composite (FRC) bridge can offer a good alternative to conventional treatment options in replacing a missing permanent anterior tooth until a more definitive prosthesis can be provided at the end of the growth period. The purpose of this article is to present a clinical case of a single tooth replacement utilizing noninvasive and metal free fixed FRC bridge in a 13 years old child as an interim treatment option. How to cite this article: Gupta A, Yelluri RK, Munshi AK. Fiber-reinforced Composite Resin Bridge: A Treatment Option in Children. Int J Clin Pediatr Dent 2015;8(1):62-65. PMID:26124584

  14. Studying impact damage on carbon-fiber reinforced aircraft composite panels with sonicir

    SciTech Connect

    Han Xiaoyan; Zhang Ding; He Qi; Song Yuyang; Lubowicki, Anthony; Zhao Xinyue; Newaz, Golam.; Favro, Lawrence D.; Thomas, Robert L.

    2011-06-23

    Composites are becoming more important materials in commercial aircraft structures such as the fuselage and wings with the new B787 Dreamliner from Boeing which has the target to utilize 50% by weight of composite materials. Carbon-fiber reinforced composites are the material of choice in aircraft structures. This is due to their light weight and high strength (high strength-to-weight ratio), high specific stiffness, tailorability of properties, design flexibility etc. Especially, by reducing the aircraft's body weight by using such lighter structures, the cost of fuel can be greatly reduced with the high jet fuel price for commercial airlines. However, these composites are prone to impact damage and the damage may occur without any observable sign on the surface, yet resulting in delaminations and disbonds that may occur well within the layers. We are studying the impact problem with carbon-fiber reinforced composite panels and developing SonicIR for this application as a fast and wide-area NDE technology. In this paper, we present our results in studying composite structures including carbon-fiber reinforced composite materials, and preliminary quantitative studies on delamination type defect depth identification in the panels.

  15. Application of fiber-reinforced plastic rods as prestressing tendons in concrete structures. Final report

    SciTech Connect

    Mattock, A.H.; Babaei, K.

    1989-08-01

    The study is concerned with the possibility of utilizing fiber-reinforced plastic rods as prestressing tendons, in place of traditional steel tendons, in elements of prestressed-concrete bridges exposed to corrosive environments. A survey was made of available information on the behavior characteristics of fiber-reinforced plastic tension elements and, in particular, those of glass-fiber-reinforced (GFR) tension elements. Also, an analytical study was made of the flexural behavior of concrete elements prestressed by GFR tendons. Based on the analytical study and on the survey of available information, an assessment is made of the impact on the design of prestressed-concrete members if GFR tendons are used. Some preliminary design recommendations are made, together with proposals for research needed before GFR prestressing tendons should be used in practice. Four GFR tendons with Con-Tech Systems anchorages were tested, the primary variable being the embedded length of the GFR rods in the anchorages. All the tendons failed by the rods pulling out of the anchorages. For embedded lengths of 15.2 in or greater, the failure loads were 90% of the advertised tendon strength of 220 ksi, or about 100% of the guaranteed tensile strength of 197 ksi (60 kN/rod).

  16. Strength and conductivity of unidirectional copper composites reinforced by continuous SiC fibers

    NASA Astrophysics Data System (ADS)

    Kimmig, S.; Allen, I.; You, J. H.

    2013-09-01

    A SiC long fiber-reinforced copper composite offers a beneficial combination of high strength and high thermal conductivity at elevated temperatures. Both properties make the composite a promising material for the heat sink of high-heat-flux components. In this work, we developed a novel Cu/SiCf composite using the Sigma fiber. Based on HIP technique, a metallurgical process was established for fabricating high quality specimens using a TiC interface coating. Extensive tensile tests were conducted on the unidirectionally reinforced composite at 20 °C and 300 °C for a wide range of fiber volume fraction (Vf). In this paper, a large amount of test data is presented. The transversal thermal conductivity varies from 260 to 130 W/mK at 500 °C as Vf is increased from 13% to 37%. The tensile strength reached up to 1246 MPa at 20 °C for Vf = 37.6%, where the fracture strain was limited to 0.8%. The data of both elastic modulus and ultimate strength exhibited a good agreement with the rule-of-mixture predictions indicating a high quality of the materials. The strength of the composite with the Sigma fibers turned out to be superior to those of the SCS6 fibers at 300 °C, although the SCS6 fiber actually has a higher strength than the Sigma fiber. The fractographic pictures of tension test and fiber push-out test manifested a sufficient interfacial bonding. Unidirectional copper composite reinforced by long SiC fibers was fabricated using the Sigma SM1140+ fiber for a wide range of fiber volume fraction from 14% to 40%. Extensive tensile tests were carried out at RT and 300 °C. The data of ultimate strength as well as elastic modulus exhibited a good agreement with the rule-of-mixture predictions indicating a high quality of the materials. In terms of the tensile strength, the Cu/Sigma composite turned out to be superior to the previous Cu/SCS6 composite at 300 °C, while comparable at RT, although the SCS6 fiber has a higher strength than the Sigma fiber. Such a

  17. Improvement of fatigue life and prevention of internal crack initiation of chopped carbon fiber reinforced plastics modified with micro glass fibers

    NASA Astrophysics Data System (ADS)

    Fujitani, Ryohei; Okubo, Kazuya; Fujii, Toru

    2016-04-01

    The purpose of this study is to improve fatigue properties of chopped carbon fiber reinforced plastics fabricated by SMC (Sheet Molding Compound) method and to clarify the mechanism for improvement. To enhance the properties, micro glass fibers with 500nm in diameter were added directly into vinyl ester resin with 0.3wt% contents. The chopped carbon fiber reinforced plastics were fabricated and cured at room temperature for 1hour under 1MPa and then at 60degree-C for 3hours. After curing, the fabricated plate was cut into the dimension of specimen. Tensile and bending strength and fatigue life of chopped carbon fiber reinforced plastics were investigated by tensile and three point bending test and cyclic tension-tension test, respectively. The behavior of strain concentration around the tips of carbon fiber were discussed with model specimen on the observations with DIC (Digital Image Correlation) method and polarizing microscope under tensile loading, in which one chopped carbon fiber was embedded into the matrix. In conclusion, when toughened vinyl ester resin modified with micro glass fibers was used as matrix, tensile and bending strength and fatigue life of chopped carbon fiber reinforced plastics were increased 56.6%, 49.8% and 14 to 23 times compared with those of unmodified specimens. It should be explained that static and dynamic properties of chopped carbon fiber reinforced plastics were improved by that crack initiation and propagation were prevented according to the prevention of the locally increasing of strain around the tip of carbon fiber, when vinyl ester resin modified with micro glass fibers was used as matrix.

  18. Detection of environmental deterioration in fiber reinforced composites by Ft-Raman spectroscopy. Phase I. Final report, 30 July 1993-30 April 1994

    SciTech Connect

    Farquharson, S.; Bananno, A.; Basilakis, R.; Carangelo, M.; DiTaranto, M.

    1994-05-01

    A number of advanced fiber reinforced organic matrix composites are being developed and applied in the aerospace industry. In these applications, the composites may be exposed to a variety of harsh environments, which may induce chemical and physical changes in the composite material, and ultimately lead to component failure. The successful use of these composites, therefore, requires methods to reliably detect and assess these changes. During this Phase I Program, a fiber optic based Fourier transform Raman spectrometer was specifically developed to perform nondestructive evaluation of environmentally damaged composites. Specifically, graphite and Kevlar reinforced epoxy and polyimide composite samples were subjected to thermal cycling, moisture exposure and ultraviolet irradiation. Three point flexure tests were used to measure flexural strength, flexural modulus, failure strain and failure load to assess induced mechanical property changes in the composites. Reflectance infrared spectra of the sample surfaces, as well as transmission infrared spectra of evolved gas phase chemical species were used to further characterize these changes.

  19. Influence of calcium sulfoaluminate cement on the pullout performance of reinforcing fibers: An evaluation of the micro-mechanical behavior

    NASA Astrophysics Data System (ADS)

    Jewell, Robert Benjamin

    The objective of this research was to determine the influence of calcium sulfoaluminate (CSA) cement on reinforcing fibers by evaluating the fiber pullout behavior, and bonding characteristics, of a single fiber embedded in a cementitious paste matrix. Four types of fibers commonly used in industry were evaluated: 1) Polyvinyl alcohol; 2) Polypropylene; 3) Coated Steel; and 4) Plain Steel. Upward trends in energy costs and potential greenhouse gas regulations favor an increased use of construction materials that require lower energy and lower CO2 emissions to fabricate, such as CSA cement, as opposed to the production of ordinary portland cement (OPC), which is more energy intensive and produces more CO2 emissions. However, widespread use of CSA cement requires a more in-depth understanding of the engineering characteristics that govern its performance, including interaction with reinforcing fibers. The overarching objective of this research was to provide the engineering base needed for the utilization of reinforcing fibers in CSA cement-based construction materials. The aims of the research were (1) to develop an ettringite-rich calcium sulfoaluminate cement, and (2) evaluate the pullout characteristics of reinforcing fibers embedded in a CSA-cement matrix. Key elements of the strategy included (1) Compare the performance of a laboratory-fabricated CSA cement to a commercial CSA cement and OPC, (2) Evaluate the peak load, and toughness of reinforcing fibers in CSA cement and OPC, (3) Evaluate the debonding-energy density and multiple-cracking behavior of fibers in CSA cement and OPC, and (4) Evaluate the shear bond strength of reinforcing fibers in CSA cement and OPC. Based on the findings of this PhD dissertation, calcium sulfoaluminate cement has a significant influence on the characteristics and behavior of embedded reinforcing fibers. An important factor contributing to the bond strength between fiber and matrix was the ability to transfer interfacial

  20. Computational Implementation of a Thermodynamically Based Work Potential Model For Progressive Microdamage and Transverse Cracking in Fiber-Reinforced Laminates

    NASA Technical Reports Server (NTRS)

    Pineda, Evan J.; Waas, Anthony M.; Bednarcyk, Brett A.; Collier, Craig S.

    2012-01-01

    A continuum-level, dual internal state variable, thermodynamically based, work potential model, Schapery Theory, is used capture the effects of two matrix damage mechanisms in a fiber-reinforced laminated composite: microdamage and transverse cracking. Matrix microdamage accrues primarily in the form of shear microcracks between the fibers of the composite. Whereas, larger transverse matrix cracks typically span the thickness of a lamina and run parallel to the fibers. Schapery Theory uses the energy potential required to advance structural changes, associated with the damage mechanisms, to govern damage growth through a set of internal state variables. These state variables are used to quantify the stiffness degradation resulting from damage growth. The transverse and shear stiffness of the lamina are related to the internal state variables through a set of measurable damage functions. Additionally, the damage variables for a given strain state can be calculated from a set of evolution equations. These evolution equations and damage functions are implemented into the finite element method and used to govern the constitutive response of the material points in the model. Additionally, an axial failure criterion is included in the model. The response of a center-notched, buffer strip-stiffened panel subjected to uniaxial tension is investigated and results are compared to experiment.