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  • Other Sources  (344)
  • NASA Technical Reports  (344)
  • COMPOSITE MATERIALS  (344)
  • 1980-1984  (344)
  • 1984  (204)
  • 1981  (140)
  • 1
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    The effect of space environment exposure on the properties of polymer matrix composite materials (A0180) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The objective of this experiment is to determine the effect of various lengths of exposure to a space environment on the mechanical properties of selected commercial polymer matrix composite materials. Fiber materials will include graphite, boron, S-glass, and PRD-49. The mechanical properties to be investigated are orthotropic elastic constants, strength parameters (satisfying the tensor polynomial relation), coefficients of thermal expansion, impact resistance, crack propagation, and fracture toughness. In addition, the effect of laminate thickness on property changes will also be investigated.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 41-43
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  • 2
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    The effect of the space environment on composite materials (A0138-9) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The objective is to test different types of materials (laminates, thermal coatings, and adhesives) to determine their actual useful lifetime. These experiments will also make is possible to integrate the histories of the thermal and mechanical characteristics into models of the composite structures. The experiment is passive and is located in one of the boxes in a 12-in.-deep peripheral tray with nine other experiments from France. The box will provide protection for the samples from contamination during the launch and reentry phases of the Long Duration Exposure Facility mission. The experiment revolves around four themes of study: thermal coatings, adhesives, dimensional stability, and mechanical characteristics. The various materials will be arranged in six levels within the box, so only the first level will be subjected to direct solar radiation. Each level will consist of plates from which test specimens will be cut after the mission.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 32-34
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  • 3
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    Space environment effects on spacecraft materials (M0003) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The immediate objectives of this experiment are to understand changes in the properties and structure of materials after exposure to the space environment and to compare these changes with predictions based on laboratory experiments. The experiment consists of 19 subexperiments involving a number of DOD laboratories and contractor organizations. In general, the experimental approach with each of the subexperiments will involve comparison of preflight and postflight analyses. Typical analyses will include the measurement of optical properties (reflectance, transmittance, and refractive index), and macrophysical properties. In addition to measuring changes in the macroscopic properties of the returned specimens, microstructural properties will also be examined. Thus, it may be possible to increase our understanding of the changes induced by the environment. This increased understanding can then be used to predict the performance of materials based on knowledge of the space environment and the results of laboratory tests. This experiment will be a coopperative effort and will provide an opportunity for DOD space programs and laboratories to evaluate materials and components after long exposures to the space environment.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 44-48
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  • 4
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    Evaluation of long-duration exposure to the natural space environment on graphite-polyimide and graphite-epoxy mechanical properties (A0175) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The primary objective of this experiment is to accumulate the needed operational data associated with the exposure of graphite-polyimide and graphite-epoxy material to the environments of space. The experiment will be mounted in two 3-in.-deep peripheral trays. Graphite-polyimide specimens will occupy 1 1/3 trays and the graphite-epoxy specimens will occupy two-thirds of a tray. The experiment approach requires two matched sets of specimens with traceable records that are maintained for materials processing and specimen quality. After fabrication, one set of each test specimen will be sectioned and structurally tested to serve as a data baseline. After the flight, the other set of specimens will undergo extensive measurements of mechanical properties for comparison with the original data baseline. Structural testing of the graphite-polyimide specimens will provide strength and elastic data in tension, compression, and shear. Transverse tension microcracking and crack propagation will be evaluated by photomicroscopy. Structural testing of the graphite-epoxy specimens will include verification of laminate, core, adhesive, and fatigue properties as applied to the design and analysis of the payload bay door. Microcracking and crack propagation will also be analyzed by photomicroscopy.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 38-40
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  • 5
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    Effect of space exposure of some epoxy matrix composites on their thermal expansion and mechanical properties (A0138-8) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: This experiment has three objectives. The first and main objective is to detect a possible variation in the coefficient of thermal expansion of composite samples during a 1-year exposure to the near-Earth orbital environment. A second objective is to detect a possible change in the mechanical integrity of composite products, both simple elements and honeycomb sandwich assemblies. A third objective is to compare the behavior of two epoxy resins commonly used in space structural production. The experimental approach is to passively expose samples of epoxy matrix composite materials to the space environment and to compare preflight and postflight measurements of mechanical properties. The experiment will be located in one of the three FRECOPA (French cooperative payload) boxes in a 12-in.-deep peripheral tray that contains nine other experiments from France. The FRECOPA box will protect the samples from contamination during the launch and reentry phases of the mission. The coefficients of thermal expansion are measured on Earth before and after space exposure.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 27-31
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  • 6
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    Space exposure of composite materials for large space structures (A0134) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The objective of this experiment is to evaluate the effects of the near-Earth orbital environment on the physical and chemical properties of laminated continuous-filament composites and composites resin films for use in large space structures and advanced spacecraft. The experiment is passive and occupies about one-half of a 6-in.-deep peripheral tray. Specimens of composite materials and polymeric and resin films are arranged above and below the experiment mounting plate to enable both exposure and nonexposure to sunlight. This provides a comparison of the effects of ultraviolet plus vacuum plus thermal cycling and those of vacuum plus thermal cycling on these materials. The experiment tray is thermally isolated from the Long Duration Exposure Facility structure to allow the material specimens to experience a wide range of thermal cycles. Tensile and compression specimens will be used to evaluate the laminated composite materials. A number of the specimens are precut and ready for testing after space exposure, whereas other specimens will be prepared from larger samples.
    Keywords: COMPOSITE MATERIALS
    Type: Long Duration Exposure Facility (LDEF); p 24-26
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  • 7
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    Influence of extended exposure in space on mechanical properties of high-toughness graphite-epoxy composite material (A0019) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Graphite-epoxy composites are promising candidates for structural use in space vehicles because of their high strength and elastic modulus properties. The problem of low fracture toughness was solved by use of recently developed techniques of intermittent interlaminar bonding. Before this material can be adapted for space use, however, confidence must be gained that its mechanical properties are not degraded by exposure to the space environment. The objective of this experiment is to test the effect of extended exposure to a space environment on the mechanical properties of a specially toughened T300/5208 graphite-epoxy composite material. Specimens made by recently developed techniques of intermittent interlaminar bonding will be exposed and afterward tested for fracture toughness, tensile strength, and elastic modulus. The approach of this experiment is to provide a frame on which the specimens can be mounted with their flat sides normal to the Long Duration Exposure Facility radius, each specimen with an unobstructed exposure of about 2 pi sr. The specimens will be mounted so that they neither fracture from high stress nor fail from excessive heating during launch and return.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 19-20
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  • 8
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    Simplified composite micromechanics equations of hygral, thermal, and mechanical properties (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A unified set of composite micromechanics equations of simple form is summarized and described. This unified set can be used to predict unidirectional composite (ply) geometric, mechanical, thermal and hygral properties using constituent material (fiber/matrix) properties. This unified set also includes approximate equations for predicting (1) moisture absorption; (2) glass transition temperature of wet resins; and (3) hygrothermal degradation effects. Several numerical examples are worked-out to illustrate ease of use and versatility of these equations. These numerical examples also demonstrate the interrelationship of the various factors (geometric to environmental) and help provide insight into composite behavior at the micromechanistic level.
    Keywords: COMPOSITE MATERIALS
    Type: SAMPE Quarterly (ISSN 0036-0821); 15; 14-23
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  • 9
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    Off-axis tensile properties and fracture in a unidirectional graphite/polyimide composite (Celion 6000/PMR 15) (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Tensile properties of unidirectional Celion 6000 graphite/PMR 15 polyimide composites prepared by hot molding and cold molding processes were measured at room temperature and 316 C, the upper use temperature of the polyimide resin, at both 45 and 90 deg to the fiber axis. The resulting fractures were characterized by scanning electron microscopy and materialographic techniques. Variation in tensile properties with processing history occurred in the elastic modulus and strain to failure for specimens loaded at 90 deg at 316 C, and in the fracture stress, and hence the in-plane shear stress, for those loaded at 45 deg at room temperature. Significant plastic deformation was observed in the 45 deg orientation at 316 C for material produced by both processing methods. In general, fracture occurred by both failure within the matrix and at the fiber-matrix interface; the degree of interfacial failure increased with temperature. Secondary cracking below the primary fracture surface was also observed.
    Keywords: COMPOSITE MATERIALS
    Type: Polymer Composites (ISSN 0272-8397); 5; 179-185
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  • 10
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    Cyclic debonding of adhesively bonded composites (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: To analyze the fatigue behavior of a simple composite-to-composite bonded joint, a combined experimental and analytical study of the cracked-lap-shear specimen subjected to constant-amplitude cyclic loading was undertaken. Two bonded systems were studied: T300/5208 graphite/epoxy adherends bonded with adhesives EC 3445 and with FM-300. For each bonded system, two specimen geometries were tested: (1) a strap adherend of 16 plies bonded to a lap adherend of 8 plies, and (2) a strap adherend of 8 plies bonded to a lap adherend of 16 plies. In all specimens tested, the fatigue failure was in the form of cyclic debonding with some 0 deg fiber pull-off from the strap adherend. The debond always grew in the region of adhesive that had the highest mode I (peel) loading and that region was close to the adhesive-strap interface. Furthermore, the measured cyclic debond growth rates correlated well with total strain energy release rates G(T) as well as with its components G(I) (peel) and G(II) (shear) for the mixed-mode loading in the present study.
    Keywords: COMPOSITE MATERIALS
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  • 11
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    PMR polyimide composites for aerospace applications (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A novel class of addition-type polyimides has been developed in response to the need for high temperature polymers with improved processability. The new plastic materials are known as PMR (for in situ polymerization of monomer reactants) polyimides. The highly processable PMR polyimides have made it possible to realize much of the potential of high temperature resistant polymers. Monomer reactant combinations for several PMR polyimides have been identified. The present investigation is concerned with a review of the current status of PMR polyimides. Attention is given to details of PMR polyimide chemistry, the processing of composites and their properties, and aerospace applications of PMR-15 polyimide composites.
    Keywords: COMPOSITE MATERIALS
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  • 12
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    Environmental and high strain rate effects on composites for engine applications (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Previously cited in issue 13, p. 2034, Accession no. A82-30118
    Keywords: COMPOSITE MATERIALS
    Type: AIAA Journal (ISSN 0001-1452); 22; 128-134
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  • 13
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    Interlaminar fracture of random short-fiber SMC composite (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: In the experimental phase of the present study of the interlaminar fracture behavior of a randomly oriented short fiber sheet molding compound (SMC) composite, the double cantilever beam fracture test is used to evaluate the mode I interlaminar fracture toughness of different composite thicknesses. In the analytical phase of this work, a geometrically nonlinear analysis is introduced in order to account for large deflections and nonlinear load deflection curves in the evaluation of interlaminar fracture toughness. For the SMC-R50 material studied, interlaminar toughness is an order of magnitude higher than that of unreinforced neat resin, due to unusual damage mechanisms ahead of the crack tip, together with significant fiber bridging across crack surfaces. Composite thickness effects on interlaminar fracture are noted to be appreciable, and a detailed discussion is given on the influence of SMC microstructure.
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Composite Materials (ISSN 0021-9983); 18; 574-594
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  • 14
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    Phosphorus-containing imide resins - Modification by elastomers (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The syntheses and general features of addition-type maleimide resins based on bis(m-aminophenyl)phosphine oxide and tris(m-aminophenyl)phosphine oxide have been reported previously. These resins have been used to fabricate graphite cloth laminates having excellent flame resistance. These composites did not burn even in pure oxygen. However, these resins were somewhat brittle. This paper reports the modification of these phosphorus-containing resins by an amine-terminated butadiene-acrylonitrile copolymer (ATBN) and a perfluoroalkylene diaromatic amine elastomer (3F). An approximately two-fold increase in short beam shear strength and flexural strength was observed at 7 percent ATBN concentration. The tensile, flexural, and shear strengths were reduced when 18 percent ATBN was used. Anaerobic char yields of the resins at 800 C and the limiting oxygen indexes of the laminates decreased with increasing ATBN concentration. The perfluorodiamine (3F) was used with both imide resins at 6.4 percent concentration. The shear strength was doubled in the case of the bisimide with no loss of flammability characteristics. The modified trisimide laminate also had improved properties over the unmodified one. The dynamic mechanical analysis of a four-ply laminate indicated a glass transition temperature above 300 C. Scanning electron micrographs of the ATBN modified imide resins were also recorded.
    Keywords: COMPOSITE MATERIALS
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  • 15
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    Chemical feasibility of lithium as a matrix for structural composites (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The chemical compatibility of lithium with tows of carbon and aramid fibers and silicon carbide and boron monofilaments was investigated by encapsulating the fibers in liquid lithium and also by sintering. The lithium did not readily wet the various fibers. In particular, very little lithium infiltration into the carbon and aramid tows was achieved and the strength of the tows was seriously degraded. The strength of the boron and silicon carbide monofilaments, however, was not affected by the liquid lithium. Therefore lithium is not feasible as a matrix for carbon and aramid fibers, but a composite containing boron or silicon carbide fibers in a lithium matrix may be feasible for specialized applications.
    Keywords: COMPOSITE MATERIALS
    Type: Composites (ISSN 0010-4361); 15; 305-309
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  • 16
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    Investigating compression failure mechanisms in composite laminates with a transient fiberglass-epoxy birefringent material (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An experimental study is reported in which a nondestructive technique involving the use of a transparent fiberglass-epoxy composite birefringent material has been used to investigate compression failure mechanisms in graphite-epoxy laminates. It is shown that the birefringency and transparency of the fiberglass-epoxy material permits regions of high stress to be located and the mechanisms of local failure propagation to be identified within the laminate. The material may also be useful for studying stress fields and for identifying failure initiation and propagation mechanisms in a wide variety of composite-structure problems.
    Keywords: COMPOSITE MATERIALS
    Type: Experimental Techniques (ISSN 0732-8818); 8; 24
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  • 17
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    Carbon/graphite composite material study. Appendix C: NASA studies on modification of carbon/graphite fibers and alternative materials (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The feasibility of modifying resin matrix composites to reduce the potential of electrical shorting from fire released fiber was explored. The effort included modifications to or coatings for graphite fibers, alternative fibers, modifications to matrix materials, and hybrid composites. The objectives included reduction of the conductivity of the graphite fiber, char formation to reduce fiber release, glass formation to prevent fiber release, catalysis to assure fiber consumption in a fire, and replacement of the graphite fibers with nonconductive fibers of similar mechanical potential.
    Keywords: COMPOSITE MATERIALS
    Type: Executive Office of the President Carbon(Graphite Composite Material Study; p 101-105
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  • 18
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    Carbon/graphite composite material study, appendix A and appendix B (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A comprehensive assessment of the possible damage to electrical and electronic equipment caused by accidental release of carbon fibers from burning civil aircraft with carbon composite parts was completed. The study concluded that the amount of fiber likely to be released is much lower than initially predicted. Carbon fiber released from an aircraft crash fire was found (from atmospheric dissemination models) to disperse over a much larger area than originally estimated, with correspondingly lower fiber concentrations. Long term redissemination of fiber was shown to be insignificant if reasonable care is exercised in accident cleanup. The vulnerability of electrical equipment to structural fibers in current use was low. Consumer appliances, industrial electronics, and avionics were essentially invulnerable to carbon fibers. Shock hazards (and thus potential injury or death) were found to be extremely unlikely.
    Keywords: COMPOSITE MATERIALS
    Type: Executive Office of the President Carbon(Graphite Composite Material Study; p 48-100
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  • 19
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    Carbon/graphite composite material study. 3: Agency program activities. National Aeronautics and Space Administration (NASA) (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The accidental release of carbon fibers from civil aircraft and the need for protection of civil aircraft systems from such fibers were studied. It was concluded that the electrical hazard from carbon fibers accidentally released in an aircraft crash fire pose no threat to human life. Overall costs associated with carbon fiber release are predicted to be extremely low. The risk of electrical or electronic failures due to carbon fibers is so minimal that future exploitation of carbon composites in aircraft should be continued. Additional protection of aircraft avionics to guard against carbon fibers is unnecessary. A program to develop alternate materials specifically to overcome the potential electrical hazard is not justified.
    Keywords: COMPOSITE MATERIALS
    Type: Executive Office of the President Carbon(Graphite Composite Material Study; p 6-10
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  • 20
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    Dynamic crack propagation and arrest in orthotropic DCB fiber composite specimens (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An orthotropic double cantilever beam (DCB) model is used to study dynamic crack propagation and arrest in 90 deg unidirectional Hercules AS/3501-6 graphite fiber epoxy composites. The dynamic fracture toughness of the composite is determined from tests performed on the long-strip specimen and DCB crack arrest experiments are conducted. By using the dynamic fracture toughness in a finite-difference solution of the DCB governing partial differential equations, a numerical solution of the crack propagation and arrest events is computed. Excellent agreement between the experimental and numerical crack arrest results are obtained.
    Keywords: COMPOSITE MATERIALS
    Type: Engineering Fracture Mechanics; 14; 2, 19; 1981
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  • 21
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    Modification of epoxy-reinforced glass-cloth composites with a perfluorinated alkyl ether elastomer (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A perfluorinated alkyl ether diacyl fluoride prepolymer (molecular weight about 1500) was coreacted with Epon 828 epoxy resin and diamino diphenyl sulfone to obtain an elastomer-toughened, glass-cloth composite. Improvements in flexural toughness, impact resistance, and water resistance, without loss of strength, modulus of elasticity or a lowering of the glass-transition temperature, were realized over those of the unmodified composite. Factors concerning optimization of the process are discussed. Results suggest that a simultaneously interpenetrating polymer network may be formed which gives rise to a measured improvement in composite mechanical properties.
    Keywords: COMPOSITE MATERIALS
    Type: Polymer Composites (ISSN 0272-8397); 5; 198-201
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  • 22
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    Simplified composite micromechanics equations for strength, fracture toughness and environmental effects (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A unified set of composite micromechanics equations of simple form is summarized and described. This unified set includes composite micromechanics equations for predicting: (1) ply in-plane uniaxial strengths; (2) through-the-thickness strength (interlaminar and flexural); (3) in-plane fracture toughness; (4) in-plane impact resistance; and (5) through-the-thickness (interlaminar and flexural) impact resistance. Equations are also included for predicting the hygrothermal effects on strength, fracture toughness and impact resistance. Several numerical examples are worked out to illustrate the ease of use of the various composite micromechanics equations.
    Keywords: COMPOSITE MATERIALS
    Type: SAMPE Quarterly (ISSN 0036-0821); 15; 41-55
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  • 23
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    Thermogravimetric analysis of silicon carbide-silicon nitride fibers at ambient to 1000 C in air (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Thermogravimetric analysis of silicon carbide-silicon nitride fibers was carried out at ambient to 1000 C in air. The weight loss over this temperature range was negligible. In addition, the oxidative stability at high temperature for a short period of time was determined. Fibers heated at 1000 C in air for fifteen minutes showed negligible weight loss (i.e., less than 1 percent).
    Keywords: COMPOSITE MATERIALS
    Type: SAMPE Quarterly (ISSN 0036-0821); 15; 39
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  • 24
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    Processing and flammability parameters of bismaleimide and some other thermally stable resin matrices for composites (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The effect of processing variables on the flammability and mechanical properties of state-of-the-art and advanced resin matrices for graphite composites were studied. Resin matrices which were evaluated included state-of-the-art epoxy, phenolic-novolac, phenolic-Xylok, two types of bismaleimides, benzyl, polyethersulfone, and polyphenylsulfone. Comparable flammability and thermochemical data on graphite-reinforced laminates prepared with these resin matrices are presented, and the relationship of some of these properties to the anaerobic char yield of the resins is described.
    Keywords: COMPOSITE MATERIALS
    Type: Polymer Composites (ISSN 0272-8397); 5; 143-150
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  • 25
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    General Electric composite ring-disk flywheel: Recent and potential developments (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Recent developments of the General Electric hybrid rotor design are described. The relation of the hybrid rotor design to flywheel designs that are especially suitable for spacecraft applications is discussed. Potential performance gains that can be achieved in such rotor designs by applying latest developments in materials, processing, and design methodology are projected. Indications are that substantial improvements can be obtained.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center An Assessment of Integrated Flywheel System Technol.; p 209-231
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  • 26
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    Flexible matrix composite laminated disk/ring flywheel (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An energy storage flywheel consisting of a quasi-isotropic composite disk overwrapped by a circumferentially wound ring made of carbon fiber and a elastometric matrix is proposed. Through analysis it was demonstrated that with an elastomeric matrix to relieve the radial stresses, a laminated disk/ring flywheel can be designed to store a least 80.3 Wh/kg or about 68% more than previous disk/ring designs. at the same time the simple construction is preserved.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center An Assessment of Integrated Flywheel System Technol.; p 193-207
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  • 27
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    Generic composite flywheel designs (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Fiber reinforced composites belong to a new class of materials and allow great flexibility in flywheel design. The most efficient flywheel may no longer have the classic Stodola taper and indeed, may not even be round. Some of the flywheel designs that have been developed in the past are discussed. Although choice of material, mounts and service requirements often dictate the final design choice for a particular application, the composite flywheels in this paper are classified within a geometric framework, a simple stress analysis of a circular disk is carried out.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center An Assessment of Integrated Flywheel System Technol.; p 169-179
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  • 28
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    Inorganic composites for space applications (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The development of inorganic composite materials for space applications is reviewed. The composites do not contain any organic materials, and therefore, are not subject to degradation by ultraviolet radiation, volatilization of constituents, or embrittlement at low temperatures. The composites consist of glass, glass/ceramics or ceramic matrices, reinforced by refractory whiskers or fibers. Such composites have the low thermal expansion, refractories, chemical stability and other desirable properties usually associated with the matrix materials. The composites also have a degree of toughness which is extraordinary for refractory inorganic materials.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Marshall Space Flight Center 2nd Symp. on Space Industrialization; p 321-332
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    Development of a Heterogeneous Laminating Resin (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-17
    Description: The feasibility of toughening the common types of matrix resins such as Narmco 5208 by utilizing a heterogeneous additive was examined. Some basic concepts and principles in the toughening of matrix resins for advanced composites were studied. The following conclusions were advanced: (1) the use of damage volume as a guide for measurement of impact resistance appears to be a valid determination; (2) short beam shear is a good test to determine the effect of toughening agents on mechanical properties; (3) rubber toughening results in improved laminate impact strength, but with substantial loss in high temperature dry and wet strength; (4) in the all-epoxy systems, the polycarbonate toughening agent seemed to be the most effective, although hot-wet strength is sacrificed; ABS was not as effective; and (5) in general, the toughened all-epoxy systems showed better damage tolerance, but less hot-wet strength; toughened bismaleimides had better hot-wet strength.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 261-272
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    Fundamental Studies of Composite Toughness (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-17
    Description: Evaluation of drop weight impact testing of neat resin and crossplied graphite fiber reinforced composites resulted in three conclusions: (1) during impact of cross-ply laminates, resin properties appear to influence the extent and mechanism of damage propagation; (2) by itself, neat resin strain to fracture is not a controlling influence on resin or composite fracture toughness; and (3) impact failure energy of neat resin plates can give a misleading indication of the resin contribution to composite impact behavior because of differences in the magnitude of diaphragm action in the two systems. Both geometric and composite constituent materials properties influence the drop weight impact resistance of crossplied composite plates. The matrix influence appears to be reflected in the incipient damage mechanism and the propagation of damage.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 125-136
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    Accurate Measurement of Heat Capacity by Differential Scanning Calorimetry (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: Experience with high quality heat capacity measurement by differential scanning calorimetry is summarized and illustrated, pointing out three major causes of error: (1) incompatible thermal histories of the sample, reference and blank runs; (2) unstable initial and final isotherms; (3) incompatible differences between initial and final isotherm amplitudes for sample, reference and blank runs. Considering these problems, it is shown for the case of polyoxymethylene that accuracies in heat capacity of 0.1 percent may be possible.
    Keywords: COMPOSITE MATERIALS
    Type: Composite Struct. Mater.; p 127-145
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  • 32
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    Variation of Resin Properties Through the Thickness of Cured Samples (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: It is the purpose of this work to gain knowledge of the glassy materials used as matrices in composites and to study the homogeneity resulting from the curing process. An attempt is made to link the glass transition quantitatively with the presence of a given material. Expoxy resins containing various amounts of hardener (TGDDM/DDS system) were cured in a muffle furnace at 473 K for seven hours. The glass transition temperature, T sub g versus weight minus percent of hardener in the epoxy resin were measured. A limit was rapidly reached in T sub g at only two percent hardener. Thus, the glass transition of the fully cured epoxy-amine matrix seems not much different from the epoxide-epoxide cure. The T sub g versus cure-time for the epoxide-epoxide reaction was also studied. My 720 was cured by itself in an oil bath at 473 K for different lengths of time. The T sub g was found to increase exponentially with the cure time, and a maximum T sub g of about 450 K was reached after eleven hours. The reaction was found to be inhibited by running the sample under argon.
    Keywords: COMPOSITE MATERIALS
    Type: Composite Struct. Mater.; p 101-126
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  • 33
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    Chemical Modification of the Surface of High Modulus Carbon Fibers (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The deposition of selected monomers on the surface of high modulus carbon fibers was studied. The fundamental principles which provide the basis for the design of a predictable interfacial bond between carbon fibers and polymeric matrices are described.
    Keywords: COMPOSITE MATERIALS
    Type: Composite Struct. Mater.; p 11-25
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    Solvent Resistant Thermoplastic Composite Matrices (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The following approaches improved the solvent resistance and raised the Tg of thermoplastics: end-capping aligomers with ethynyl groups; incorporating ethynyl groups pendent along the polymer chain; and correcting polymers containing pendent ethynyl groups with a low molecular weight diethynyl compound. The following conclusions were reached: (1) film and composite properties off an ethynyl-terminated sulfone were better than those of UDEL (trademark); (2) fracture energy of an ethynyl-terminated sulfone was lower than that of UDEL (trademark); (3) residual palladium in the cured ethynyl-terminated sulfone lower the thermooxidative stability of the cured resin; (4) the properties of a phenoxy resin were altered considerably by placing pendent ethynyl groups along the polymer chain; and (5) property trade-offs must be considered when thermoplastics are modified via reactant groups.
    Keywords: COMPOSITE MATERIALS
    Type: Tough Composite Mater.; p 317-335
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  • 35
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    Newer Carbon Fibers and Their Properties (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The newer carbon fibers that are either on the market or coming in the near future are described. The structure of carbon fibers is discussed along with the relationship between structure and physical property. Finally, how different types of structure are designed by control of process parameters is described.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 245-257
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  • 36
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    Experimental and Theoretical Studies of Moisture and Temperature Effects on the Mechanical Properties of Graphite/Epoxy Laminates and Neat Resins (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The properties of high performnce composites which are strongly dependent on the physical properties of the matrix resin were studied. Moisture adversely affect the properties of both neat epoxy resin and epoxy matrix composites. Inhomogeneous swelling as to the moisture degradation of mechanical properties, both in the neat resin and the composite. It is postulated that the postcuring process can change structure/moisture interactions and partially alleviate its adverse effects. The study is directed toward are understanding of the physical/mechanical/thermodynamic aspects of this problem.
    Keywords: COMPOSITE MATERIALS
    Type: Composite Struct. Mater.; p 35-38
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  • 37
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    The Chemical Nature of the Fiber/resin Interface in Composite Materials (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: Carbon fiber/epoxy resin composites are considered. The nature of the fiber structure and the interaction that occurs at the interface between fiber and matrix are emphasized. Composite toughness can be improved by increased axial tensile and compressive strengths in the fibers. The structure of carbon fibers indicates that the fiber itself can fail transversely, and different transverse microstructures could provide better transverse strengths. The higher surface roughness of lower modulus and surface-treated carbon fibers provides better mechanical interlocking between the fiber and matrix. The chemical nature of the fiber surface was determined, and adsorption of species on this surface can be used to promote wetting and adhesion. Finally, the magnitude of the interfacial bond strength should be controlled such that a range of composites can be made with properties varying from relatively brittle and high interlaminar shear strength to tougher but lower interlaminar shear strength.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 209-225
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  • 38
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    Composites for Increased Wear Resistance: Current Achievements and Future Prospects (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: The various ways in which reductions in wear and/or friction can be achieved by the use of composite materials are reviewed. Reinforced plastics are emphasized and it is shown that fillers and fibers reduce wear via several mechanisms additional to their role of increasing overall mechanical strength, preferential transfer, counter face abrasion, preferential load support, or third-body formation on either the composite or its counterface. Examples are given from recent work on thin layer composites of the type widely used as dry bearings in aircraft flight control mechanisms. Developments in metal based composites and carbon-carbon composites for high energy brakes are discussed. The aspects which could benefit by increased fundamental understanding identified and the types of composites which appear to have greatest potential for further growth are indicated.
    Keywords: COMPOSITE MATERIALS
    Type: NASA Lewis Research Center Tribology in the 80's. Vol. 1; p 333-356
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  • 39
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    Quantification of Saint-Venant's Principle for a General Prismatic Member (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-17
    Description: A semi-analytic finite element method for finding the decay rates of edge effects in anisotropic layered plates was extended to the treatment of prismatic members of an arbitrary cross section composed of any number of anisotropic elements. The displacement fields corresponding to the decay rates with positive real part were determined for a homogenous graphite/epoxy plate two units thick. The behavior of a rectangular beam is also considered.
    Keywords: COMPOSITE MATERIALS
    Type: Composite Struct. Mater.; p 67-88
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  • 40
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    Composite Property Dependence on the Fiber, Matrix, and the Interphase (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-17
    Description: The matrix properties of a difunctional epoxy, Epon 828, were varied. The Hercules type A fiber was also utilized in this investigation. The fiber and the interface between fiber and matrix were examined in terms of shear strength. Micrographs of the epoxy matrix are presented.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 227-243
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  • 41
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    The Effect of Cross-Link Density on the Toughening Mechanism of Elastomer-Modified Epoxies (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-17
    Description: A DGEBA epoxide resin (EPON 828) was elastomer modified by using three different carboxyl terminated butadiene acrylonitrile copolymers. The fracture toughness of these elastomer modified epoxies was measured in terms of the critical strain energy release rate, G sub IC. The toughening mechanism was elucidated using a tensile dilatometry technique. A plot of volume strain versus longitudinal strain often reveals the types of micromechanical deformations occurring in the uniaxial tensile specimen up to yield. Several microscopy techniques were employed to corroborate the tensile dilatometry results. The role of matrix ductility on the toughening mechanism of elastomer modified epoxies was investigated. By reducing the cross link density with various equivalent weight epoxide resins. Fracture toughness was again measured in terms of G sub IC. The characterization of the toughening mechanism was performed using a uniaxial tensile dilatometry technique and corroborated using various microscopy techniques.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 173-194
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  • 42
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    Characterization of Interlaminar Crack Growth in Composites with the Double Cantilever Beam Specimen (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-17
    Description: A project to examine the double cantilever beam specimen as a quantitative test method to assess the resistance of various composite materials to interlaminar crack growth is discussed. A second objective is to investigate the micromechanics of failure for composites with tough matrix resins from certain generic types of polymeric systems: brittle thermosets, toughened thermosets, and thermoplastics. Emphasis is given to a discussion of preliminary results in two areas: the effects of temperature and loading rate for woven composites, and the effects of matrix toughening in woven and unidirectional composites.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 3-16
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  • 43
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    Improved Beam Theory for Anisotropic Materials (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-17
    Description: The behavior of beams made of anisotropic material was investigated in order to develop an appropriate model of such behavior. Closed form solutions of the problem were derived using two alternative approaches. In the first approach, the axial displacements are expanded as a series of eigenwarpings. In the second approach, the axial stresses are expanded as a series of eigenwarpings. A finite element solution was also derived using the same displacement field as in the first approach.
    Keywords: COMPOSITE MATERIALS
    Type: Composite Struct. Mater.; p 89-99
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  • 44
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    DC calibration of the strain sensitivity of a single mode optical fiber interferometer (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The strain sensitivity of an optical fiber interferometer developed for the detection of pulsed ultrasonic waves in solids was calibrated. Light from the output ends of both fibers was superimposed to form an interference fringe pattern that was interrogated in the far field to give a signal proportional to the differential optical fiber path length. Strain sensitivity is determined by comparing data obtained by clamping and bending the bar at different lengths to simple cantilever beam theory. A minimum theoretical detectable strain of less than 10 to the minus 10th power is indicated.
    Keywords: COMPOSITE MATERIALS
    Type: Va. Polytech. Inst. and State Univ. Opt. Fiber Interferometer for the Study of Ultrasonic Waves in Composite Mater.; p 13-15
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  • 45
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    Detection of ultrasonic waves in solids by an optical fiber interferometer (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: An optical fiber interferometer was developed for the detection of ultrasonic waves in solids. The optical paths in both the signal and reference arms of the Mach-Zehnder interferometer are through the cores of similar lengths of single mode fiber mode stripped at both input and output. Instantaneous translation of the pattern is proportional to the localized strain produced by ultrasonic bulk waves generated in the disc and integrated along the fiber path. By spatially filtering the moving fringe pattern and synchronously demodulating the filtered optical intensity distirbution, a signal proportional to the integrated strain is obtained.
    Keywords: COMPOSITE MATERIALS
    Type: Va. Polytech. Inst. and State Univ. Opt. Fiber Interferometer for the Study of Ultrasonic Waves in Composite Mater.; p 7-11
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  • 46
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    Optical fiber interferometer for the study of ultrasonic waves in composite materials, discussion (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Ultrasonic waves in composite materials using optical fiber waveguide as the detecting device were studied. The possibility of using embedded probes in composites for nondestructive evaluation is discussed. It is found that interferometric system is sensitive but requires accurate optical positioning at both fiber input and output.
    Keywords: COMPOSITE MATERIALS
    Type: Opt. Fiber Interferometer for the Study of Ultrasonic Waves in Composite Mater.; p 2-6
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  • 47
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    Acousto-ultrasonic measurements to monitor damage during fatigue of composites (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An acousto-ultrasonic nondestructive testing method used to monitor damage during static and fatigue loading of thin graphite epoxy laminates is described. The experimental procedure, the signal analysis by the Fast Fourier Transform (FFT) algorithm, and the results of this analysis are discussed. Quasi-static tension tests showed a sharp decrease in the quantitative parameters when transverse cracks developed in the 90 degrees plies of a (0, 90/2/)s laminate. When internal micro-delaminations unite to form macro-delaminations, a sharp decrease in the parameters is also observed. The parameters are found to correlate well with other indications of damage development such as stiffness and degradation. The root mean square value of the moment is found to be more sensitive to damage than stiffness. Various signals and spectrums of graphite epoxy systems are presented.
    Keywords: COMPOSITE MATERIALS
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  • 48
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    Ground exposure of composite materials for helicopters (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Residual strength results are presented on four composite material systems that were exposed for three years at locations on the North American Continent. The exposure locations are near the areas where Bell Model 206L Helicopters, that are in a NSA/U.S. Army sponsored flight service program, are flying in daily commercial service. The composite systems are: (1) Kevlar-49 fabric/F-185 epoxy; (2) Kevlar-49 fabric/LRF-277 epoxy; (3) Kevlar-49 fabric/CE-306 epoxy; and (4) T-300 Graphite/E-788 epoxy. All material systems exhibited good strength retention in compression and short beam shear. The Kevlar-49/LRF-277 epoxy retained 88 to 93 percent of the baseline strength while the other material systems exceeded 95 percent of baseline strength. Residual tensile strength of all materials did not show a significant reduction. The available moisture absorption data is also presented.
    Keywords: COMPOSITE MATERIALS
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  • 49
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    Finite element analysis of instability related delamination growth (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Instability-related growth of through-width delaminations in laminated coupons was investigated analytically and experimentally. In the analytical effort, a geometrically nonlinear finite-element stress analysis was used, and the numerical results were compared with exact solutions. In addition, measured lateral deflections of postbuckled through-width delaminations were compared with predicted deflections. Lateral deflections, stress distributions, and strain energy release rates were calculated for various delamination lengths, delamination depths, and applied loads. Delamination growth rates observed for unidirectional graphite/epoxy bonded to aluminum were qualitatively correlated with calculated strain-energy release rates and it was found that the Mode I component of energy release dominates the growth process.
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Composite Materials; 15; Sept
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  • 50
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    Micro-area Auger analysis of a SiC/Ti fibre composite (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Micro-area Auger electron spectroscopy with a spatial resolution of less than 50 nm has been used to study the concentration of elements across the reaction zone of a W-reinforced SiC fiber in a titanium matrix. Although the elemental concentrations obtained by this technique are affected by the reaction zone morphology to a greater extent than in the case of X-ray microprobe analysis, the proposed technique has the advantage of a much higher spatial resolution and avoids the problems of bulk averaging that characterize the X-ray technique.
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Materials Science; 16; Nov. 198
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    Development and characterization of orthotropic-birefringent materials (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Materials were selected and fabrication procedures developed for orthotropic birefringent materials. An epoxy resin (Maraset 658/558 system) was selected as the matrix material. Fibers obtained from style 3733 glass cloth and type 1062 glass roving were used as reinforcement. Two different fabrication procedures were used. In the first one, layers of unidirectional fibers removed from the glass cloth were stacked, impregnated with resin, bagged and cured in the autoclave at an elevated temperature. In the second procedure, the glass roving was drywound over metal frames, impregnated with resin and cured at room temperature under pressure and vacuum in an autoclave. Unidirectional, angle-ply and quasi-isotropic laminates of two thicknesses and with embedded flaws were fabricated. The matrix and the unidirectional glass/epoxy material were fully characterized. The density, fiber volume ratio, mechanical, and optical properties were determined. The fiber volume ratio was over 0.50. Birefringent properties were in good agreement with predictions based on a stress proportioning concept and also, with one exception, with properties predicted by a finite element analysis. Previously announced in STAR as N81-26183
    Keywords: COMPOSITE MATERIALS
    Type: Experimental Mechanics (ISSN 0014-4851); 24; 135-143
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  • 52
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    Effect of microcracks on the thermal expansion of composite laminates (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A finite element analysis was used to quantitatively predict the effect of matrix microcracks in the 90 deg plies of graphite/epoxy composites on the coefficient of thermal expansion in the 0 deg direction, alpha (y) (perpendicular to the cracks). Results were generated for (0m/90n)s, (0/+ or 45/90)s and (0/90/ + or - 45)s graphite/epoxy laminate configurations. Analytical predictions were compared with experimental results for the two quasi-isotropic laminate configurations. Both analytical and experimental results showed that microcracks reduced the effective stiffness of the 90 deg plies, thus causing the laminates, thermal response to be more like that of a (0) laminate. The change in alpha(y) was a function of lamina material properties, microcrack density, fiber orientation, and stacking sequence. A combination of classical lamination theory and finite element analysis was used to predict the effect of microcracks in both the 90 deg and 0 deg plies. Analytical results showed that the addition of microcracks in the 0 deg plies do affect alpha(y), but to a lesser extent than those in the 90 deg plies.
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Composite Materials (ISSN 0021-9983); 18; 173-187
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  • 53
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    Carboxyl-terminated butadiene-acrylonitrile-modified epoxy resin and its graphite fiber-reinforced composite - Morphology and dynamic mechanical properties (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: COMPOSITE MATERIALS
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  • 54
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    Impact properties of rubber-modified epoxy resin-graphite-fiber composites (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: To improve the impact resistance of graphite-fiber composites, a commercial and an experimental epoxy resin were modified with liquid reactive rubber and a brominated epoxy resin. The commercial epoxy was a tetrafunctional resin, and the experimental epoxy was a trifunctional resin. The reactive rubber was a carboxyl-terminated butadiene-acrylonitrile copolymer. The rubber content was varied from 0 to 25 percent (wt). The brominated epoxy resin was used at Br levels of 4, 19, and 35 percent of the resin. Composites were prepared with woven graphite cloth reinforcement. The composites were evaluated by using flexural strength in the dry state and an elevated temperature after saturation with water. The impact properties were determined by measuring shear strength after falling-ball impact and instrumented impact. The rubber-modified, trifunctional resin exhibited better properties, when tested in hot-wet conditions in a heated oven at 366 K (after boiling the material for 2 h in demineralized water), than the tetrafunctional resin. Improved impact resistance was observed with the addition of the reactive rubber to the epoxy resin. Further improvement was observed with the addition of the brominated epoxy resin.
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  • 55
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    Composite interlaminar fracture - Effect of matrix fracture energy (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A major result of the use of the double cantilever beam test to provide a measure of the interlaminar fracture energy in composites subjected to simple Mode I-type loading is the observation that increasing the toughness of the matrix resin by as much as a factor of 20 produced a major (approximately four-fold) increase in interlaminar fracture energy. The data presently analyzed show that, with brittle polymers, resin toughness is fully transferred to the composite, while in the case of tougher polymers the resin toughness is only partially transferred due to the fibers' restriction of the crack tip deformation zone in the polymer, together with their changing of local stress field details. Factors which tend to increase interlaminar toughness are fiber nesting and bridging, as well as fiber breakage and pull-out during crack growth.
    Keywords: COMPOSITE MATERIALS
    Type: Composites Technology Review; 6; 176-180
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  • 56
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    Effects of water during cure on the properties of a carbon/phenolic system (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The effects of prepreg water contamination on interlaminar shear strength, tranverse compressive strength, and longitudinal compressive strength were determined. Decreases in these properties due to water contamination were sugstantial: 28 percent for the interlaminar shear strength, 21 percent for the transverse compressive strength and 31 percent for the longitudinal compressive strength. Since voids were not detected by X-ray analysis, the most likely cause for these results is fiber-matrix debounding in the laminate.
    Keywords: COMPOSITE MATERIALS
    Type: SAMPE Quarterly (ISSN 0036-0821); 15; 47-49
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  • 57
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    Effects of thermal cycling on mechanical properties of graphite polyimide (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 13, p. 2034, Accession no. A82-30101
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 21; 274-280
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  • 58
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    Postbuckling behavior of graphite-epoxy panels (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Structurally efficient fuselage panels are often designed to allow buckling to occur at applied loads below ultimate. Interest in applying graphite-epoxy materials to fuselage primary structure led to several studies of the post-buckling behavior of graphite-epoxy structural components. Studies of the postbuckling behavior of flat and curved, unstiffened and stiffened graphite-epoxy panels loaded in compression and shear were summarized. The response and failure characteristics of specimens studied experimentally were described, and analytical and experimental results were compared. The specimens tested in the studies described were fabricated from commercially available 0.005-inch-thick unidirectional graphite-fiber tapes preimpregnated with 350 F cure thermosetting epoxy resins.
    Keywords: COMPOSITE MATERIALS
    Type: ACEE Composite Struct. Technol.; p 137-160
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    Synthesis and toughness properties of resins and composites (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Tensile and shear moduli of four ACEE (Aircraft Energy Efficiency Program) resins are presented along with ACEE composite material modulus predictions based on micromechanics. Compressive strength and fracture toughness of the resins and composites were discussed. In addition, several resin synthesis techniques are reviewed.
    Keywords: COMPOSITE MATERIALS
    Type: ACEE Composite Struct. Technol.; p 75-96
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  • 60
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    Residual-strength tests of L-1011 vertical fin components after 10 and 20 years of simulated flight service (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Part of the NASA/ACEE Program was to determine the effect of long-term durability testing on the residual strength of graphite-epoxy cover panel and spar components of the Lockheed L-1011 aircraft vertical stabilizer. The results of these residual strength tests are presented herein. The structural behavior and failure mode of both cover panel and spar components were addressed, and the test results obtained were compared with the static test results generated by Lockheed. The effect of damage on one of the spar specimens was described.
    Keywords: COMPOSITE MATERIALS
    Type: ACEE Composite Struct. Technol.; p 1-16
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  • 61
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    Comparison of toughened composite laminates using NASA standard damage tolerance tests (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The proposed application of composite materials to transport wing and fuselage structures prompted the search for tougher materials having improved resistance to impact damage and delamination. Several resin/graphite fiber composite materials were subjected to standard damage tolerance tests and the results were compared to ascertain which materials have superior toughness. In addition, test results from various company and NASA laboratories were compared for repeatability.
    Keywords: COMPOSITE MATERIALS
    Type: ACEE Composite Struct. Technol.; p 51-74
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  • 62
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    Impact dynamics research on composite transport structures (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The experimental and analytical efforts being undertaken to investigate the response of composite and aluminum structures under crash loading conditions were reviewed. A Boeing 720 airplane was used in the controlled-impact demonstration test. Energy absorption of composite materials, the tearing of fuselage skin panels, the friction and abrasion behavior of composite skins, and the crushing behavior and dynamic response of composite beams were among the topics addressed.
    Keywords: COMPOSITE MATERIALS
    Type: ACEE Composite Struct. Technol.; p 113-136
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  • 63
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    Tensile strength of composite sheets with unidirectional stringers and crack-like damage (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The damage tolerance characteristics of metal tension panels with riveted and bonded stringers are well known. The stringers arrest unstable cracks and retard propagation of fatigue cracks. Residual strengths and fatigue lives are considerably greater than those of unstiffened or integrally stiffened sheets. The damage tolerance of composite sheets with bonded composite stringers loaded in tension was determined. Cracks in composites do not readily propagate in fatigue, at least not through fibers. Moreover, the residual strength of notched composites is sometimes even increased by fatigue loading. Therefore, the residual strength aspect of damage tolerance, and not fatigue crack propagation, was investigated. About 50 graphite/epoxy composite panels were made with two sheet layups and several stringer configurations. Crack-like slots were cut in the middle of the panels to simulate damage. The panels were instrumented and monotonically loaded in tension to failure. The tests indicate that the composite panels have considerable damage tolerance, much like metal panels. The stringers arrested cracks that ran from the crack-like slots, and the residual strengths were considerably greater than those of unstiffened composite sheets. A stress intensity factor analysis was developed to predict the failing strains of the stiffened panels. Using the analysis, a single design curve was produced for composite sheets with bonded stringers of any configuration.
    Keywords: COMPOSITE MATERIALS
    Type: ACEE Composite Struct. Technol.; p 97-112
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  • 64
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    Worldwide flight and ground-based exposure of composite materials (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The long-term durability of those advanced composite materials which are applicable to aircraft structures was discussed. The composite components of various military and commercial aircraft and helicopters were reviewed. Both ground exposure and flight service were assessed in terms of their impact upon composite structure durability. The ACEE Program is mentioned briefly.
    Keywords: COMPOSITE MATERIALS
    Type: ACEE Composite Struct. Technol.; p 17-50
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  • 65
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    Study of utilization of advanced composites in fuselage structures of large transports (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effort required by the transport aircraft manufacturers to support the introduction of advanced composite materials into the fuselage structure of future commercial and military transport aircraft is investigated. Technology issues, potential benefits to military life cycle costs and commercial operating costs, and development plans are examined. The most urgent technology issues defined are impact dynamics, acoustic transmission, pressure containment and damage tolerance, post-buckling, cutouts, and joints and splices. A technology demonstration program is defined and a rough cost and schedule identified. The fabrication and test of a full-scale fuselage barrel section is presented. Commercial and military benefits are identified. Fuselage structure weight savings from use of advanced composites are 16.4 percent for the commercial and 21.8 percent for the military. For the all-composite airplanes the savings are 26 percent and 29 percent, respectively. Commercial/operating costs are reduced by 5 percent for the all-composite airplane and military life cycle costs by 10 percent.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-172404 , NAS 1.26:172404 , LR-30786
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  • 66
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    ACEE composite structures technology (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Topics addressed include: strength and hygrothermal response of L-1011 fin components; wing fuel containment and damage tolerance development; impact dynamics; acoustic transmission; fuselage structure; composite transport wing technology development; spar/assembly concepts.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-172360 , NAS 1.26:172360
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  • 67
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    ACEE composite structures technology (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The NASA Aircraft Energy Efficiency (ACEE) Composite Primary Aircraft Structures Program has made significant progress in the development of technology for advanced composites in commercial aircraft. Commercial airframe manufacturers have demonstrated technology readiness and cost effectiveness of advanced composites for secondary and medium primary components and have initiated a concerted program to develop the data base required for efficient application to safety-of-flight wing and fuselage structures. Oral presentations were compiled into five papers. Topics addressed include: damage tolerance and failsafe testing of composite vertical stabilizer; optimization of composite multi-row bolted joints; large wing joint demonstation components; and joints and cutouts in fuselage structure.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-172359 , NAS 1.26:172359
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  • 68
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    ACEE composite structures technology (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Toppics addressed include: advanced composites on Boeing commercial aircraft; composite wing durability; damage tolerance technology development; heavily loaded wing panel design; and pressure containment and damage tolerance in fuselages.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-172358 , NAS 1.26:172358
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  • 69
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    Advanced composite combustor structural concepts program (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An analytical study was conducted to assess the feasibility of and benefits derived from the use of high temperature composite materials in aircraft turbine engine combustor liners. The study included a survey and screening of the properties of three candidate composite materials including tungsten reinforced superalloys, carbon-carbon and silicon carbide (SiC) fibers reinforcing a ceramic matrix of lithium aluminosilicate (LAS). The SiC-LAS material was selected as offering the greatest near term potential primarily on the basis of high temperature capability. A limited experimental investigation was conducted to quantify some of the more critical mechanical properties of the SiC-LAS composite having a multidirection 0/45/-45/90 deg fiber orientation favored for the combustor linear application. Rigorous cyclic thermal tests demonstrated that SiC-LAS was extremely resistant to the thermal fatigue mechanisms that usually limit the life of metallic combustor liners. A thermal design study led to the definition of a composite liner concept that incorporated film cooled SiC-LAS shingles mounted on a Hastelloy X shell. With coolant fluxes consistent with the most advanced metallic liner technology, the calculated hot surface temperatures of the shingles were within the apparent near term capability of the material. Structural analyses indicated that the stresses in the composite panels were low, primarily because of the low coefficient of expansion of the material and it was concluded that the dominant failure mode of the liner would be an as yet unidentified deterioration of the composite from prolonged exposure to high temperature. An economic study, based on a medium thrust size commercial aircraft engine, indicated that the SiC-LAS combustor liner would weigh 22.8N (11.27 lb) less and cost less to manufacture than advanced metallic liner concepts intended for use in the late 1980's.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-174733 , NAS 1.26:174733 , PWA-5890-24
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  • 70
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    Durability and damage tolerance of Large Composite Primary Aircraft Structure (LCPAS) (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Analysis and testing addressing the key technology areas of durability and damage tolerance were completed for wing surface panels. The wing of a fuel-efficient, 200-passenger commercial transport airplane for 1990 delivery was sized using graphite-epoxy materials. Coupons of various layups used in the wing sizing were tested in tension, compression, and spectrum fatigue with typical fastener penetrations. The compression strength after barely visible impact damage was determined from coupon and structural element tests. One current material system and one toughened system were evaluated by coupon testing. The results of the coupon and element tests were used to design three distinctly different compression panels meeting the strength, stiffness, and damage-tolerance requirements of the upper wing panels. These three concepts were tested with various amounts of damage ranging from barely visible impact to through-penetration. The results of this program provide the key technology data required to assess the durability and damage-tolerance capability or advanced composites for use in commercial aircraft wing panel structure.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-3767 , NAS 1.26:3767 , D6-49579
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  • 71
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    Biaxial fatigue properties of thin-walled composite tubes (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A testing method for obtaining fatigue and fracture data under biaxial loading and for negative R-ratios is described. Thin-walled tubes of 1-in. outer nominal diameter with a tapered grip section were tested in an Axial-Torsion Servohydraulic Testing Machine with a 463 Data Control Processor at frequencies below 10 Hz up to the 1-million cycle range. Room temperature, uniaxial constant amplitude fatigue data for high temperature cure graphite-epoxy material are presented at R = -0.4 for a (+, - 5 deg) fiber orientation. The fatigue curve is almost horizontal. Tests on (+, - 5 deg) 'SP-328' resulted in failures which predominantly originated in the grip section. Presently, a new specimen design is being tested intended to eliminate cracking in the grip section. Biaxial in-phase loading of (0/+, - 45) tubes of Fiberite graphite-epoxy resulted in much steeper fatigue curves than observed under uniaxial loading.
    Keywords: COMPOSITE MATERIALS
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  • 72
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    Analyses of quasi-isotropic composite plates under quasi-static point loads simulating low-velocity impact phenomena (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: In thin composite laminates, the first level of visible damage occurs in the back face and is called back face spalling. A plate-membrane coupling model, and a finite element model to analyze the large deformation behavior of eight-ply quasi-isotropic circular composite plates under impact type point loads are developed. The back face spalling phenomenon in thin composite plates is explained by using the plate-membrane coupling model and the finite element model in conjunction with the fracture mechanics principles. The experimental results verifying these models are presented. Several conclusions concerning the deformation behavior are reached and discussed in detail.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-176485 , NAS 1.26:176485
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  • 73
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    The effect of cyclic loading on the stiffness degradation of angle-ply composite laminates (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation has been conducted to determine the effect of cyclic loading on the stiffness degradation of composite laminates. Specimens were tested in tension-tension fatigue at a frequency of 10 Hz and a stress ratio of 0.1, over a wide range of stress levels. The laminate employed for this investigation was made of graphite/epoxy in an angle-ply (+ or - 35)2s orientation. During this investigation both static and dynamic stiffness reduction data were recorded during constant amplitude fatigue testing, and the results are presented in tabular and graphical form.
    Keywords: COMPOSITE MATERIALS
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  • 74
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    An Investigation of the Adsorption Characteristics of 5'ATP and 5'AMP onto the Surface of Caso4 x 2H2O (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A model has been proposed in which solid surfaces can act as a site for cataletic activity of condensation reactions for certain biomolecules. From this model, the adsorption characteristics of 5'ATP and 5'AMP onto the surface of CaSO4.2H2O was chosen for study. It has been proven that 5'ATP and 5'AMP do adsorb onto the surface of CaSO4. Studies were then made to determine the dependence of absorption versus time, concentration, ionic strength and pH. It was found that the adsorption of the nucleotides is highly pH dependent, primarily determined by the phosphate acid groups of the nucleic acid molecule. From this investigation, the data obtained is discussed in relation to the model for the prebiotic earth.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-177005 , NAS 1.26:177005
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  • 75
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    Graphite/epoxy composite stiffened panel fabrication development (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This report describes the manufacturing development procedures used to fabricate a series of carbon/epoxy panels with integrally molded stiffeners. Panel size was started at 6 inches by 18 inches and one stiffener and increased to 30 inches by 60 inches and six integral stiffeners. Stiffener concepts were optimized for minimum weight (or mass) to carry stress levels from 1500 lbs/inch to 25,000 lbs/inch compression load. Designs were created and manufactured with a stiffener configuration of integrally molded hat, J, I, sine wave I, solid blade, and honeycomb blade shapes. Successful and unsuccessful detail methods of tooling, lay-up methods, and bagging methods are documented. Recommendations are made for the best state-of-the-art manufacturing technique developed for type of stiffener construction.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-172204 , NAS 1.26:172204
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  • 76
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    Advanced composite vertical fin for L-1011 aircraft (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The structural box of the L-1011 vertical fin was redesigned using advanced composite materials. The box was fabricated and ground tested to verify the structural integrity. This report summarizes the complete program starting with the design and analysis and proceeds through the process development ancillary test program production readiness verification testing, fabrication of the full-scale fin boxes and the full-scale ground testing. The program showed that advanced composites can economically and effectively be used in the design and fabrication of medium primary structures for commercial aircraft. Static-strength variability was demonstrated to be comparable to metal structures and the long term durability of advanced composite components was demonstrated.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-3816 , NAS 1.26:3816
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  • 77
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    Standard test evaluation of graphite fiber/resin matrix composite materials for improved toughness (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Programs sponsored by NASA with the commercial transport manufacturers to develop a technology data base are required to design and build composite wing and fuselage structures. To realize the full potential of composite structures in these strength critical designs, material systems having improved ductility and interlaminar toughness are being sought. To promote systematic evaluation of new materials, NASA and the commercial transport manufacturers have selected and standardized a set of five common tests. These tests evaluate open hole tension and compression performance, compression performance after impact at an energy level of 20 ft-lb, and resistance to delamination. Ten toughened resin matrix/graphite fiber composites were evaluated using this series of tests, and their performance is compared with a widely used composite system.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-86298 , NAS 1.15:86298
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  • 78
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    Advanced manufacturing development of a composite empennage component for L-1011 aircraft. Phase 3: Production readiness verification testing (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Twenty-two specimens of each of two key structural elements of the Advance Composite Vertical Fin (ACVF) were fabricated and tested. One element represented the front spar at the fuselage attachment area and the other element represented the cover at the fuselage joint area. Ten specimens of each element were selected for static testing. The coefficient of variation resulting from the tests was 3.28 percent for the ten cover specimens and 6.11 percent for the ten spar specimens, which compare well with metallic structures. The remaining twelve cover and twelve spar specimens were durability tested in environmental chambers which permitted the temperature and humidity environment to be cycled as well as the applied loads. Results of the durability tests indicated that such components will survive the service environment.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-172383-PH-3 , NAS 1.26:172383-PH-3
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  • 79
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    Free Volume Considerations in Thermoplastic and Thermosetting Resins (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-17
    Description: The direct measurement of physical aging and of the volume changes which go on during the course of this aging is discussed. Data on PMMA showing its physical aging as measured by its stress relaxation response and the accompanying volume changes are presented. An indication of how one can measure the free volume both directly from the volume change itself and relatively directly via a new technique is given. The application of this new technique (electron spin resonance spectroscopy) to other polymer systems is demonstrated.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 195-208
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  • 80
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    Effects of Constituent Properties on Compression Failure Mechanisms (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-17
    Description: Compression failure mechanisms were investigated through the analysis of matrix-embedded fiber bundles. The use of fiber bundle specimens can provide much needed information on compression failure mechanisms because failure of the bundle is well contained and can be monitored during testing. The method can clearly distinguish between buckling-induced failure and shear-induced failure. The results indicate that WY and T300 graphite fibers and E-glass fiber fail in buckling while the high-modulus P75S graphite fiber fails in shear. Buckling-induced failure becomes more evident with low-modulus fiber in softer epoxy.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 81-98
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  • 81
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    Composite Fracture Toughness and Impact Characterization (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The basic threat to the more widespread use of composites in aircraft primary structure is the problem of residual strength in the presence of damage. Specific problem areas that need to be addressed include the following: (1) modeling/understanding composite failure (impact: relate strain energy release rate to strain-to-failure, open hole compression: relate shear crippling to strain-to-failure, and account for variables such as thickness and stacking sequence); (2) micromechanics models; (3) consider the use of hybrid combinations, both interply and intraply, using graphite, Kevlar, and glass; and (4) modeling/understanding the role of the interface. Solving these problems involves a multidisciplinary approach including dynamics, structural stability, composite mechanics, and fracture mechanics.
    Keywords: COMPOSITE MATERIALS
    Type: Tough Composite Mater.; p 381-383
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  • 82
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    Constituent Property - Composite Property Relationships in Thermoset Matrices (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: A procedure to effectively screen and evaluate resins for aerospace structures and advanced composites is described. The following conclusions were advanced: (1) laminate damage tolerance correlates positively with neat resin G sub IC; (2) TGDDM/DDS resins can be toughened; (3) using butadiene-nitrile rubbers, neat resin G sub IC and ultimate strain increase with increasing nitrile content, with the number of chemically reactive groups per molecule, and with increasing molecular weight; (4) better balance of properties combined with high G sub IC may be achieved by using tough glassy thermoplastics instead of rubbers to modify TGDDM/DDS resins; (5) both toughening mechanisms require good phase separation with an effective interphase; (6) the kind and the amount of thermoplastic modifier remain to be selected; and (7) presently only about a fourfold increase in G sub IC was achieved, whereas a forty fold increase is sought; modification of the matrix backbone and of crosslinking is required.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 159-171
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  • 83
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    Matrix Synthesis and Characterization (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: The role of NASA in the area of composite material synthesis; evaluation techniques; prediction analysis techniques; solvent-resistant tough composite matrix; resistance to paint strippers; acceptable processing temperature and pressure for thermoplastics; and the role of computer modeling and fiber interface improvement were discussed.
    Keywords: COMPOSITE MATERIALS
    Type: Tough Composite Mater.; p 389-391
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  • 84
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    Matrix Resin Characterization in Cured Graphite Composites Using Diffuse Reflectance-Ftir (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: The chemical characterization of cured graphite fiber reinforced polymer matrix composites is complicated by the fact that the resins are insoluble and the composites are apaque. Standard analyses which depend either on the ability to dissolve the sample or to detect transmitted radiation are impossible. As a result, data reported on environmentally exposed composites primarily concern macroscopic information such as weight loss or changes in selected mechanical properties. Diffuse reflectance in combination with fourier transform infrared spectroscopy was developed to gain a basic chemical understanding of composite and adhesive behavior. Several composite and adhesive materials were characterized before and after environmental exposure. In each case significant changes in resin molecular structure were observed and correlated with changes in mechanical properties, providing new insights into material performance.
    Keywords: COMPOSITE MATERIALS
    Type: Tough Composite Mater.; p 295-316
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  • 85
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    Free-Edge Failures of Composite Laminates (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: The free-edge delamination of graphite/epoxy laminates under static loading is being analyzed to obtain fundamental understanding of the continuum mechanics involved. The analyses are conducted by idealizing the material response of each ply in the laminate as homogenous, linear elastic, and anisotropic. A generalized plane strain elastic boundary value problem was formulated to investigate the energy variation of such a body.
    Keywords: COMPOSITE MATERIALS
    Type: Composite Struct. Mater.; p 63-64
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  • 86
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    Constituent Properties and Interrelationships (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: The requirements and recommendations of constituent properties and relationships are: (1) goals/requirement statement; (2) better operational definition of toughness; (3) assess limitations of current micromechanics models/procedures; (4) explicity assess currently known resin toughening mechanisms and determine their relative importance to matrix resins; (5) method to define the interphase region in situ; (6) assess thermodynamic compatibility of any new resin with the fiber; and (7) model polymer systems.
    Keywords: COMPOSITE MATERIALS
    Type: Tough Composite Mater.; p 385-388
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  • 87
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    Morphology and Dynamic Mechanical Properties of Diglycidyl Ether of Bisphenol-A Toughened with Carboxyl-Terminated Butadiene-Acrylonitrile (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: The fracture toughness of an incorporation of a carboxyl-terminated butadiene acrylonitrile (CTBN) elastomer in diglycidyl ether bisphenol A (DGEBA) resin was investigated. Measurements of dynamic mechanical properties, scanning electron microscopy and small-angle X-ray scattering were carried out to characterize the state of cure, morphology and particle size and size distribution of the neat resins and their graphite fiber reinforced composites.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 285-294
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  • 88
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    Characterizing Delamination Resistance of Toughened Resin Composites (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: The delamination resistance of toughened resin composites was studied. Both the edge delamination test (EDT) and the double-cantilever-beam (DCB) test provided a useful ranking of improvements in delamination resistance between brittle and tough resin composites. Several layups were designed for the edge delamination test to cover a wide range of mixed-mode conditions. The DCB and the various layups of the EDT were then used to characterize the interlaminar fracture behavior of brittle and toughened resin composites subjected to both static and cyclic loading.
    Keywords: COMPOSITE MATERIALS
    Type: Tough Composite Mater.; p 17-31
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    Intermodulation Product Levels in Flame-sprayed Materials (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-12
    Description: A preliminary investigation on intermodulation product (IMP) levels of fiberglass-backed flame-sprayed surfaces was completed. The purpose was to demonstrate the use of modified techniques and materials in combustion flame spraying of formed surfaces in reducing intermodulation products. The approach used improved metal wire stock without impurities or with smaller droplet sizes, high-temperature release agents, wire stock with low electrical resistance, variations in spraying distances, and intense buffing processes which amalgamate the material gaps and droplets in an effort to fabricate IMP-free lightweight and low cost subreflectors. Positive material candidates were found with an IMP level around -150 dB, which is comparable to solid aluminum surfaces used as a reference.
    Keywords: COMPOSITE MATERIALS
    Type: The Telecommun. and Data Acquisition Rept.; p 79-98
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  • 90
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    Effect of Impact Damage and Open Holes on the Compression Strength of Tough Resin/high Strain Fiber Laminates (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: Tests to assess the performance of composite structures damaged by impact or containing local discontinuities such as cutouts are discussed. In particular, two plate specimen test configurations which were developed to define the serverity of compression strength reduction are described; one for impact damage and the other open hole specimens. The test technique for impact specimens involves damaging the plate at selected energies, measuring the size of damage by ultrasonic C-scan techniques and measuring the residual strength in a compression load test. Open-hole specimen compression tests are conducted for several different hole diameters and the failure strain and load and mode of failure recorded. The plate specimen used in these tests is designed with length, width, thickness and laminate stiffness to ensure that overall plate buckling is not responsible for initiating failure.
    Keywords: COMPOSITE MATERIALS
    Type: Tough Composite Mater.; p 61-80
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  • 91
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    Composite Materials Characterization and Development at AFWAL (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: The development of test methodology for characterizing matrix dominated failure modes is discussed emphasizing issues of matrix cracking, delamination under static loading, and the relationship of composite properties to matrix properties. Both strength characterization and classical techniques of linear elastic fracture mechanics were examined. Materials development studies are also discussed. Major areas of interest include acetylene-terminated and bismaleimide resins for 350 to 450 deg use, thermoplastics development, and failure resistant composite concepts.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 33-60
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  • 92
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    Numerical Investigation of the Micromechanics of Composite Fracture (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: A generalized program for the two-dimensional analysis of static crack growth problems was developed and is being tested. In addition to a detailed examination and development of fracture criteria needed to track cracks in composites at the micromechanical level, the program employs fully automatic finite element mesh generation. This is an entirely new approach in program structure that is being taken to allow for the automatic tracking of discrete crack growth. The maximum strain energy density criterion (T-criterion) was found to be a good alternative to the minimum strain energy density criterion (S-criterion).
    Keywords: COMPOSITE MATERIALS
    Type: Composite Struct. Mater.; p 39-62
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  • 93
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    Fatigue in Composite Materials (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The deformation and failure behavior of graphite/epoxy tubes under biaxial loading was investigated. The increase of basic understanding of and provide design information for the bi-axial response of graphite/epoxy composites to fatigue loads are considered.
    Keywords: COMPOSITE MATERIALS
    Type: Composite Struct. Mater.; p 27-34
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  • 94
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    Modified Epoxy Composites (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The properties of a rubber-modified experimental epoxy resin and a standard epoxy as composite matrices were studied. In addition, a brominated epoxy resin was used in varying quantities to improve the fire resistance of the composite. The experimental resin was tris-(hydroxyphenyl)methane triglycidyl ether, known as tris epoxy novolac (TEN). The standard epoxy resin used was tetraglycidyl 4,4'-diaminodiphenyl methane (TGDDM). The above resins were modified with carboxyl-terminated butadiene acrylonitrile (CTBN) rubber. It is concluded that: (1) modification of TEN resin with bromine gives better impact resistance than rubber modification alone; (2) 25% rubber addition is necessary to obtain significant improvement in impact resistance; (3) impact resistance increases with bromine content; (4) impact velocity does not significantly affect the energy absorbed by the test sample; (5) Tg did not decline with rubber modification; and (6) TEN resin had better hot/wet properties than TGDDM resin.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 273-284
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  • 95
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    Investigation of Toughened Neat Resins and Their Relations to Advanced Composite Mechanical Properties (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: Four epoxies (Hercules 3502, Hercules 2220-1 and 2220-3, and Ciba-Geigy Fibredux 914 epoxy) were evaluated to judge their merits within the ACEE program and also to provide material property input for a micromechanics finite element program. A casting procedure was developed for the four matrix systems mentioned and mechanical properties were studied at three test temperatures and two moisture contents. A scanning electron microscope study was performed to catalogue fracture surfaces for the unreinforced (neat) epoxies. In addition, tension testing, shear testing, a limited amount of fracture toughness testing, and thermal expansion coefficient and moisture expansion coefficient testing were carried out. Mechanical material properties were generated for input into a micromechanics program and to characterize these four matrix systems.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center Tough Composite Mater.; p 137-151
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  • 96
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    The Effect of Matrix and Fiber Properties on Impact Resistance (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The basic material properties which control impact damage are identified and testing techniques are assessed. It is demonstrated that static indentation tests can provide better information about failure processes than impact tests, and they are simpler to conduct. In thin and thick laminates, it was found that the matrix shear strength controls the onset of delamination damage and that the fiber strength controlled the penetration phase. In thin laminates, tough matrices do little to enhance impact resistance.
    Keywords: COMPOSITE MATERIALS
    Type: Tough Composite Mater.; p 99-121
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  • 97
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    Nonlinear analysis for high-temperature multilayered fiber composite structures (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A unique upward-integrated top-down-structured approach is presented for nonlinear analysis of high-temperature multilayered fiber composite structures. Based on this approach, a special purpose computer code was developed (nonlinear COBSTRAN) which is specifically tailored for the nonlinear analysis of tungsten-fiber-reinforced superalloy (TFRS) composite turbine blade/vane components of gas turbine engines. Special features of this computational capability include accounting of; micro- and macro-heterogeneity, nonlinear (stess-temperature-time dependent) and anisotropic material behavior, and fiber degradation. A demonstration problem is presented to mainfest the utility of the upward-integrated top-down-structured approach, in general, and to illustrate the present capability represented by the nonlinear COBSTRAN code. Preliminary results indicate that nonlinear COBSTRAN provides the means for relating the local nonlinear and anisotropic material behavior of the composite constituents to the global response of the turbine blade/vane structure.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-83754 , E-2242 , NAS 1.15:83754
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    Thermal barrier coating system (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A high temperature oxidation resistant, thermal barrier coating system is disclosed for a nickel cobalt, or iron base alloy substrate. An inner metal bond coating contacts the substrate, and a thermal barrier coating covers the bond coating. NiCrAlR, FeCrAlR, and CoCrAlR alloys are satisfactory as bond coating compositions where R=Y or Yb. These alloys contain, by weight, 24.9-36.7% chromium, 5.4-18.5% aluminum, and 0.05 to 1.55% yttrium or 0.05 to 0.53% ytterbium. The coatings containing ytterbium are preferred over those containing yttrium. An outer thermal barrier coating of partial stabilized zirconium oxide (zirconia) which is between 6% and 8%, by weight, of yttrium oxide (yttria) covers the bond coating. Partial stabilization provides a material with superior durability. Partially stabilized zirconia consists of mixtures of cubic, tetragonal, and monoclinic phases.
    Keywords: COMPOSITE MATERIALS
    Type: NAS 1.71:LEW-13324-2
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  • 99
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    Development of in situ stiffness properties for shuttle booster filament wound case (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Subscale tests were extensively used to develop a data base on elastic properties of graphite-epoxy wound pressure vessels. Scaling phenomena were observed to influence biaxial strains. Causes for scaling are proposed and lamina models with scaling factors are presented.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TP-2377 , NAS 1.60:2377
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  • 100
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    Analysis of instability-related growth of a through-width delamination (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effect of various parameters on instability related delamination growth was studied. The configuration studied consisted of a thick composite laminate with a single through width delamination located near one surface. Both mechanical and thermal loads were considered. It is assumed that GI and GII govern delamination growth. An approximate superposition stress analysis was developed which gives closed form expressions for GI and GII. It is found that both GI and GII are very sensitive to delamination length and location through the thickness and that the magnitude of GI is also sensitive to initial imperfection. Critical loads for delamination growth are calculated based on three growth criteria. Large differences in the predictions highlight the need for a verified mixed mode delamination growth criterion.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-86301 , NAS 1.15:86301
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