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  • 1
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    The effect of space environment exposure on the properties of polymer matrix composite materials (A0180) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: 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
    Publikationsdatum: 2006-02-14
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: 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
    Publikationsdatum: 2006-02-14
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: 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
    Publikationsdatum: 2006-02-14
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: 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
    Publikationsdatum: 2006-02-14
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: 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
    Publikationsdatum: 2006-02-14
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: 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
    Publikationsdatum: 2006-02-14
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: 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
    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: 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
    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Polymer Composites (ISSN 0272-8397); 5; 179-185
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  • 10
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    Metallurgical and tensile property analysis of several silicon carbide/titanium composite systems (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Several silicon-carbide fiber reinforced titanium matrix composite systems were investigated to determine composite degradation mechanisms and to develop techniques to minimize loss of mechanical properties during fabrication and in service. Emphasis was on interface control by fiber or matrix coatings. Fibers and matrix materials were sputter coated with various metals to determine the effects of the coatings on basic fiber properties, fiber-matrix interactions, and on composite properties. The effects of limited variations in fabrication temperature on composite properties were determined for composites consolidated by standard press-diffusion-bonding techniques.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 11
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    Buffer strips in composites at elevated temperature (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The composite material 'buffer strip' concept is presently investigated at elevated temperatures for the case of graphite/polyimide buffer strip panels using a (45/0/45/90)2S layup, where the buffer strip material was 0-deg S-glass/polyimide. Each panel was loaded in tension until it failed, and radiographs and crack opening displacements were recorded during the tests to determine fracture onset, fracture arrest, and the extent of damage in the buffer strip after crack arrest. At 177 + or - 3 C, the buffer strips increased the panel strength by at least 40 percent in comparison with panels without buffer strips. Compared to similar panels tested at room temperature, those tested at elevated temperature had lower residual strengths, but higher failure strains.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Journal of Composite Materials (ISSN 0021-9983); 17; 549-560
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  • 12
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    Processing of fused silicide coatings for carbon-based materials (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The processing and oxidation resistance of fused Al-Si and Ni-Si slurry coatings on ATJ graphite was studied. Ni-Si coatings in the 70 to 90 percent Si range were successfully processed to melt, wet, and bond to the graphite. The molten coatings also infiltrated the porosity in graphite and reacted with it to form SiC in the coating. Cyclic oxidation at 1200 C showed that these coatings were not totally protective because of local attack of the substrate, due to the extreme thinness of the coatings in combination with coating cracks. Previously announced in STAR as N83-27019
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 4; 757-783
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  • 13
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    Cyclic debonding of adhesively bonded composites (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 14
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    PMR polyimide composites for aerospace applications (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 15
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    Thermal and mechanical properties of advanced, high temperature ceramic-composite insulation (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is found that the mechanical properties of fibrous refractory composite insulation (FRCI) can be improved if a higher calcination temperature is used before final processing. The results also reveal that a higher density FRCI containing 60 wt pct aluminoborosilicate fibers will exhibit minimal surface recession at 1480 C in a convective-heating environment. Another finding is that the material performance in the convective-heating environment is limited by the coating and the temperature capability of its emittance agent. A table is included giving the coating compositions used with the composite insulation and tested in the convectively heated environment at a surface temperature of 1480 C.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 4; 551-563
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  • 16
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    Environmental and high strain rate effects on composites for engine applications (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Previously cited in issue 13, p. 2034, Accession no. A82-30118
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: AIAA Journal (ISSN 0001-1452); 22; 128-134
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  • 17
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    Mechanical properties of a fiberglass prepreg system at cryogenic and other temperatures (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Previously cited in issue 13, p. 2024, Accession no. A82-30099
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: AIAA Journal (ISSN 0001-1452); 21; 1722-172
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  • 18
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    Interlaminar fracture of random short-fiber SMC composite (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Journal of Composite Materials (ISSN 0021-9983); 18; 574-594
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  • 19
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    Phosphorus-containing imide resins - Modification by elastomers (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 20
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    Chemical feasibility of lithium as a matrix for structural composites (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Composites (ISSN 0010-4361); 15; 305-309
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  • 21
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    Investigating compression failure mechanisms in composite laminates with a transient fiberglass-epoxy birefringent material (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Experimental Techniques (ISSN 0732-8818); 8; 24
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  • 22
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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
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Executive Office of the President Carbon(Graphite Composite Material Study; p 101-105
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  • 23
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    Carbon/graphite composite material study, appendix A and appendix B (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Executive Office of the President Carbon(Graphite Composite Material Study; p 48-100
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  • 24
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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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Executive Office of the President Carbon(Graphite Composite Material Study; p 6-10
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  • 25
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    Dynamic crack propagation and arrest in orthotropic DCB fiber composite specimens (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Engineering Fracture Mechanics; 14; 2, 19; 1981
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  • 26
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    Modification of epoxy-reinforced glass-cloth composites with a perfluorinated alkyl ether elastomer (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Polymer Composites (ISSN 0272-8397); 5; 198-201
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  • 27
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    Simplified composite micromechanics equations for strength, fracture toughness and environmental effects (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: SAMPE Quarterly (ISSN 0036-0821); 15; 41-55
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  • 28
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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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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).
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: SAMPE Quarterly (ISSN 0036-0821); 15; 39
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  • 29
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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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Polymer Composites (ISSN 0272-8397); 5; 143-150
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  • 30
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    Optimization of composite structures (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Structural optimization is introduced and examples which illustrate potential problems associated with optimized structures are presented. Optimized structures may have very low load carrying ability for an off design condition. They tend to have multiple modes of failure occurring simultaneously and can, therefore, be sensitive to imperfections. Because composite materials provide more design variables than do metals, they allow for more refined tailoring and more extensive optimization. As a result, optimized composite structures can be especially susceptible to these problems. Previously announced in STAR as N83-10447
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  • 31
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    Tungsten-fiber-reinforced superalloy composite, high-temperature component design considerations (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Tungsten fiber reinforced superalloy composites (TFRS) are intended for use in high temperature turbine components. Current turbine component design methodology is based on applying the experience, sometimes semiempirical, gained from over 30 years of superalloy component design. Current composite component design capability is generally limited to the methodology for low temperature resin matrix composites. Often the tendency is to treat TFRS as just another superalloy or low temperature composite. However, TFRS behavior is significantly different than that of superalloys, and the high environment adds consideration not common in low temperature composite component design. The methodology used for preliminary design of TFRS components are described. Considerations unique to TFRS are emphasized. Previously announced in STAR as N82-21259
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  • 32
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    Factors influencing the thermally-induced strength degradation of B/Al composites (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Literature data related to the thermally-induced strength degradation of B/Al composites were examined in the light of fracture theories based on reaction-controlled fiber weakening. Under the assumption of a parabolic time-dependent growth for the interfacial reaction product, a Griffith-type fracture model was found to yield simple equations whose predictions were in good agreement with data for boron fiber average strength and for B/Al axial fracture strain. The only variables in these equations were the time and temperature of the thermal exposure and an empirical factor related to fiber surface smoothness prior to composite consolidation. Such variables as fiber diameter and aluminum alloy composition were found to have little influence. The basic and practical implications of the fracture model equations are discussed. Previously announced in STAR as N82-24297
    Schlagwort(e): COMPOSITE MATERIALS
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  • 33
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    Thermal degradation of the tensile properties of undirectionally reinforced FP-Al2O3/EZ 33 magnesium composites (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The effects of isothermal and cyclic exposure on the room temperature axial and transverse tensile strength and dynamic flexural modulus of 35 volume percent and 55 volume percent FP-Al203/EZ 33 magnesium composites were studied. The composite specimens were continuously heated in a sand bath maintained at 350 C for up to 150 hours or thermally cycled between 50 and 250 C or 50 and 350 C for up to 3000 cycles. Each thermal cycle lasted for a total of six minutes with a hold time of two minutes at the maximum temperature. Results indicate no significant loss in the room temperature axial tensile strength and dynamic flexural modulus of composites thermally cycled between 50 and 250 C or of composites isothermally heated at 350 C for up to 150 hours from the strength and modulus data for the untreated, as-fabricated composites. In contrast, thermal cycling between 50 and 350 C caused considerable loss in both room temperature strength and modulus. Fractographic analysis and measurement of composite transverse strength and matrix hardness of thermally cycled and isothermally heated composites indicated matrix softening and fiber/matrix debonding due to void growth at the interface and matrix cracking as the likely causes of the strength and modulus loss behavior. Previously announced in STAR as N82-21260
    Schlagwort(e): COMPOSITE MATERIALS
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  • 34
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    The effect of a coating on the thermo-oxidative stability of Celion 6000 graphite fiber/PMR 15 polyimide composites (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The thermooxidative stability in air at 316 C of unidirectional, uncoated and aluminum-coated Celion 6000 graphite fiber/PMR 15 polyimide composites has been determined for exposure times up to nominally 2000 h. Comparison of the weight loss data and microstructural integrity reveals that a thin aluminum-foil coating can provide significant protection from oxidation. A quantitative description of the average depth of the reaction zone and the maximum length of cracks produced during oxidation as a function of time in uncoated Celion 6000/PMR 15 are given.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Composites Technology Review; 5; 109-114
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  • 35
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    General Electric composite ring-disk flywheel: Recent and potential developments (1984)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA. Langley Research Center An Assessment of Integrated Flywheel System Technol.; p 209-231
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  • 36
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    Flexible matrix composite laminated disk/ring flywheel (1984)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA. Langley Research Center An Assessment of Integrated Flywheel System Technol.; p 193-207
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  • 37
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    Generic composite flywheel designs (1984)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA. Langley Research Center An Assessment of Integrated Flywheel System Technol.; p 169-179
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  • 38
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    Inorganic composites for space applications (1984)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA. Marshall Space Flight Center 2nd Symp. on Space Industrialization; p 321-332
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  • 39
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    Studies of noise transmission in advanced composite material structures (1983)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: Noise characteristics of advanced composite material fuselages were discussed from the standpoints of applicable research programs and noise transmission theory. Experimental verification of the theory was also included.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: ACEE Composite Struct. Technol.; p 161-178
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  • 40
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    Development of a Heterogeneous Laminating Resin (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA. Langley Research Center Tough Composite Mater.; p 261-272
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  • 41
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    Fundamental Studies of Composite Toughness (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA. Langley Research Center Tough Composite Mater.; p 125-136
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  • 42
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    Accurate Measurement of Heat Capacity by Differential Scanning Calorimetry (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-16
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Composite Struct. Mater.; p 127-145
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  • 43
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    Variation of Resin Properties Through the Thickness of Cured Samples (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-16
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Composite Struct. Mater.; p 101-126
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  • 44
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    Chemical Modification of the Surface of High Modulus Carbon Fibers (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-16
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Composite Struct. Mater.; p 11-25
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  • 45
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    Solvent Resistant Thermoplastic Composite Matrices (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-16
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Tough Composite Mater.; p 317-335
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  • 46
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    Newer Carbon Fibers and Their Properties (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-16
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA. Langley Research Center Tough Composite Mater.; p 245-257
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  • 47
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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
    Publikationsdatum: 2014-09-16
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Composite Struct. Mater.; p 35-38
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  • 48
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    The Chemical Nature of the Fiber/resin Interface in Composite Materials (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-13
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA. Langley Research Center Tough Composite Mater.; p 209-225
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  • 49
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    Composites for Increased Wear Resistance: Current Achievements and Future Prospects (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-11
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA Lewis Research Center Tribology in the 80's. Vol. 1; p 333-356
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  • 50
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    Mechanical Property Characterization of F-100/934 Graphite-Epoxy Composite Material (1983)
    In:  CASI
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    Publikationsdatum: 2014-09-11
    Beschreibung: Procedures for quality control, fabrication techniques, specimen machining, test methodologies, and data collection and interpretation were defined using Thornel P-100 carbon fiber combined with Fiberite's 934 epoxy resin in unidirectional tape form. Tests on the prepreg material, including gel time, resin solids content, tack, volatile content, and flow are detailed. The steps of the fabrication and machining processes are described. Both destructive and nondestructive techniques were employed to assess the properties of the cured laminates. Tests to determine tensile strength and modulus, compressive strength and modulus, interlaminar and inplane shear strength, and flexural strength and modulus are discussed. The results of these experiments are compared with data generated by other researchers.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Alabama Univ. Res. Rept.: 1983 NASA(ASEE Summer Faculty Fellowship Program; 28 p
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  • 51
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    Quantification of Saint-Venant's Principle for a General Prismatic Member (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Composite Struct. Mater.; p 67-88
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  • 52
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    Composite Property Dependence on the Fiber, Matrix, and the Interphase (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA. Langley Research Center Tough Composite Mater.; p 227-243
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  • 53
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    The Effect of Cross-Link Density on the Toughening Mechanism of Elastomer-Modified Epoxies (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA. Langley Research Center Tough Composite Mater.; p 173-194
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  • 54
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    Characterization of Interlaminar Crack Growth in Composites with the Double Cantilever Beam Specimen (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-17
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA. Langley Research Center Tough Composite Mater.; p 3-16
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    Improved Beam Theory for Anisotropic Materials (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-17
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Composite Struct. Mater.; p 89-99
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  • 56
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    DC calibration of the strain sensitivity of a single mode optical fiber interferometer (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: 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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    Detection of ultrasonic waves in solids by an optical fiber interferometer (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: 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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  • 58
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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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Opt. Fiber Interferometer for the Study of Ultrasonic Waves in Composite Mater.; p 2-6
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  • 59
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    A unifying strain criterion for fracture of fibrous composite laminates (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Fibrous composite materials, such as graphite/epoxy, are light, stiff, and strong. They have great potential for reducing weight in aircraft structures. However, for a realization of this potential, designers will have to know the fracture toughness of composite laminates in order to design damage tolerant structures. In connection with the development of an economical testing procedure, there is a great need for a single fracture toughness parameter which can be used to predict the stress-intensity factor (K(Q)) for all laminates of interest to the designer. Poe and Sova (1980) have derived a general fracture toughness parameter (Qc), which is a material constant. It defines the critical level of strains in the principal load-carryng plies. The present investigation is concerned with the calculation of values for the ratio of Qc and the ultimate tensile strain of the fibers. The obtained data indicate that this ratio is reasonably constant for layups which fail largely by self-similar crack extension.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Engineering Fracture Mechanics; 17; 2, 19; 1983
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  • 60
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    Acousto-ultrasonic measurements to monitor damage during fatigue of composites (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 61
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    Ground exposure of composite materials for helicopters (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 62
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    Rubber-toughened polyfunctional epoxies - Brominated vs nonbrominated formulated for graphite composites (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A new, commercially available, trifunctional epoxy resin (tris-(hydroxyphenyl)-methane triglycidyl ether) was modified with synthetic rubber to increase the impact resistance of epoxy/graphite composites. These composites were reinforced with commercially available satin-weave carbon cloth using two formulations of epoxies (brominated and nonbrominated) containing various amounts of carboxy-terminated butadience acrylonitrile (CTBN) rubber that had been prereacted with epoxy resin. The impact resistance was determined by measuring the interlaminar shear strength of the composites after impact. The mechanical properties, such as flexural strength and modulus at room temperature and at 93 C, were also determined. Measurements were taken of the flammability and glass transition temperature (Tg); and a thermal-gravimetric analysis was made.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: SAMPE Quarterly (ISSN 0036-0821); 14; 34-38
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  • 63
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    Preliminary evaluation of large area bonding processes for repair of graphite/polyimide composites (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is pointed out that graphite/polyimide (Gr/PI) composites are potential candidates for primary and secondary structural components in the next generation of reusable space vehicles and supersonic aircraft which are to possess operational capabilities involving the temperature range from 400 to 600 F. In connection with the considered applications, it is necessary to establish economic and reliable methods for the repair of Gr/PI composite components which have been damaged. The present investigation is concerned with the results of research conducted to develop a bonding process applicable to the repair of large areas in Gr/PI composite structural components. Attention is given to five repair techniques for Gr/PI composite materials. The techniques were employed to fabricate large panels from which flexure and short-beam-shear specimens were machined.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 64
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    Polyfunctional epoxies - Different molecular weights of brominated polymeric additives as flame retardants in graphite composites (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The imparting of flame retardancy to graphite-reinforced composites without incurring mechanical property deterioration is investigated for the case of an experimental, trifunctional epoxy resin incorporating brominated polymeric additives (BPAs) of the diglycidyl type. Such mechanical properties as flexural strength and modulus, and short beam shear strength, were measured in dry and in hot/wet conditions, and the glass transition temperature, flammability, and water absorption were measured and compared with nonbromilated systems. Another comparison was made with a tetrafunctional epoxy system. The results obtained are explained in terms of differences in the polymeric backbone length of the bromine carrier polymer. BPAs are found to be a reliable bromine source for fire inhibition in carbon-reinforced composites without compromise of mechanical properties.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 65
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    Finite element analysis of instability related delamination growth (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Journal of Composite Materials; 15; Sept
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  • 66
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    Micro-area Auger analysis of a SiC/Ti fibre composite (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Journal of Materials Science; 16; Nov. 198
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  • 67
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    Dynamic-mechanical response of graphite/epoxy composite laminates and neat resin (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Dynamic mechanical measurement results are presented for the case of carbon fiber-reinforced, epoxy matrix composite laminates subjected to loading perpendicular to the lamination plane, as well as for neat epoxy resin under the same conditions, where temperatures ranged between 20 and 200 C and deformation levels lie within the linear viscoelastic region. In-phase and out-of-phase stiffnesses are found to become superposed, forming master curves that cover a 12-decade frequency range. The application of a master curve scaling procedure shows that the in-phase stiffness has the same shape, and out-of-phase stiffness has the same dispersion, for all laminates irrespective of stacking sequence and are, in turn, nearly identical to those for the neat epoxy resin. An empirical function is found for the relaxation modulus which, when converted to a dynamic modulus, yields good overall agreement for both of the dynamic stiffness components as a function of frequency.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: (ISSN 0272-8397)
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    Interlaminar shear properties of graphite fiber, high-performance resin composites (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Short beam testing was used to determine the shear properties of laminates consisting of T-300 and Celion 3000 and 6000 graphite fibers, in epoxy, hot melt and solvent bismaleimide, polyimide and polystyrylpyridine (PSP). Epoxy, composites showed the highest interlaminar shear strength, with values for all other resins being substantially lower. The dependence of interlaminar shear properties on the fiber-resin interfacial bond and on resin wetting characteristics and mechanical properties is investigated, and it is determined that the lower shear strength of the tested composites, by comparison with epoxy resin matrix composites, is due to their correspondingly lower interfacial bond strengths. An investigation of the effect of the wettability of carbon fiber tow on shear strength shows wetting variations among resins that are too small to account for the large shear strength property differences observed.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Polymer Composites (ISSN 0272-8397); 4; April 19
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  • 69
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    Dynamic mechanical characterization of cure of a polyimide-graphite fiber composite (PMR 15/Celion 6000) (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Dynamic mechanical studies of thermosetting PMR 15 polyimide/Celion 6000 composites were used to characterize cure behavior. Variation in composite shear modulus with cure time for laminates partially cured under 3.45 MPa pressure was compared with that of laminates fully cured under pressure to select a partially cured system whose behavior corresponded with that of the pressure-cured composites. An empirical kinetic model was developed that relates relative composite shear moduli to cure time and temperature. This model, coupled with standard statistical techniques, was used in the determination of an overall activation energy, E = 145 kj/mole (35 kcal/mole) and order of reaction, n, for the cure reaction(s). The empirical relationship defining dynamic modulus as a function of time and temperature remained linear well into the glassy region. Changes in dynamic glass-transition temperature and in the breadth of the transition peaks with cure time are discussed. Shear modulus and damping were found to be more sensitive measures of relative extent of cure than Fourier transform infrared spectroscopy.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Polymer Composites (ISSN 0272-8397); 4; April 19
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    Development and characterization of orthotropic-birefringent materials (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Experimental Mechanics (ISSN 0014-4851); 24; 135-143
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  • 71
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    Effect of microcracks on the thermal expansion of composite laminates (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Journal of Composite Materials (ISSN 0021-9983); 18; 173-187
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  • 72
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    Compressive behavior of unidirectional fibrous composites (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The longitudinal compressive behavior of unidirectional fiber composites was investigated by using the Illinois Institute of Technology Research Institute (IITRI) test method with thick and thin test specimens. The test data obtained are interpreted by means of stress/strain curves from back-to-back strain gages, examination of fracture surfaces by scanning electron microscope, and predictive equations for distinct failure modes including fiber compression failure. Euler buckling, delamination, and flexure. The results show that longitudinal compressive fracture is induced by a combination of delamination, flexure, and fiber tier breaks. No distinct fracture surface characteristics can be associated with unique failure modes. An equation is described that can be used to extract the longitudinal compressive strength from the longitudinal tensile and flexural strengths of the same composite system.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 73
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    Method for compression testing of composite materials at high strain rates (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A method is presented for testing composite materials in compression at strain rates up to approximately 500 per s. The method uses a thin ring specimen (4 in. in diameter, 1 in. wide, six-eight plies thick) loaded dynamically by an external pressure pulse applied explosively through a liquid. Strains in the specimen and in a steel calibration ring are recoorded with a digital processing oscilloscope. Results are plotted by an x-y plotter in the form of a dynamic stress-strain curve. Data analysis is based on a numerical solution of the equation of motion. A computer program is used which involves smoothing and approximation of the strain magnitude, strain rate, and strain acceleration. Dynamic stress-strain curves obtained for 0-deg and 90-deg specimens of two graphite/epoxy composites are presented.
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  • 74
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    New fireworthy composites for use in transportation vehicles (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: This paper presents an overview of certain aspects of the evaluation of the fireworthiness of air transport interiors. It examines some technical opportunities that are available today through the modification of aircraft interior subsystem components, modifications that may reasonably be expected to provide improvements in aircraft fire safety. These modifications have the potential of reducing the rate of fire growth, with a consequent reduction of heat, toxic gas, and smoke emission throughout the habitable interior of an aircraft, whatever the initial source of the fire. It is shown that these new materials modifications reduce the fire hazard not only because of their unique ablative properties, which help to contain or isolate the fire source, but also because there is a significant reduction in their characteristic flame spread, heat release, and smoke and toxic gas emissions.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Journal of Fire Sciences (ISSN 0734-9041); 1; 432-458
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  • 75
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    A conceptual model of the thermal-spike mechanism in graphte/epoxy laminates (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The influence of a thermal spike on a moisture-saturated graphite/epoxy composite was studied in detail. A single thermal spike from 25 to 132 C was found to produce damage, as evidenced by a significant increase in the level of moisture saturation in the composite. Approximately half of this increase remained after a vacuum-anneal at 150 C for seven days, suggesting the presence of an irreversible damage component. Subsequent thermal spikes created less and less additional moisture absorption, with the cumulative effect being a maximum or limiting moisture capacity of the composite. These observations are explained in terms of a model previously developed to explain the reverse thermal effect of moisture absorption in epoxy and epoxy-matrix composites. This model, based on the inverse temperature dependence of free volume, improves current understanding of thermal spike effects in graphite/epoxy composites.
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  • 76
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    Thermal aging of graphite/polyimide composites (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Celion 6000/PMR-15, Celion 6000/LARC-160, and Celion 6000/RK-99 graphite/polyimides were aged in circulating air ovens at temperatures of 202, 232, 260, and 288 C for various times, up to 15,000 h. Three unidirectional specimens were studied: short-beam-shear (SBS), flexure, and 153-mm square panels. The interior region of the square panels exhibited little or no property degradation. Based on the individually aged SBS specimen results, the relative thermal-oxidative stability from highest to lowest is as follows: PMR-15, LARC-160, RK-99, Celion 6000/PMR-15 and Celion 6000/LARC-160 laminates retained at least 80 percent of their initial flexural strengths for the duration of aging at each temperature. Celion 6000/RK-99 laminates exhibited a 20 to 50 percent loss of flexural strength at all aging temperatures. All three graphite/polyimide laminate materials degraded preferentially at the specimen edge perpendicular to the fibers.
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  • 77
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    Bolt clampup relaxation in a graphite/epoxy laminate (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A simple bolted joint was analyzed to calculate bolt clampup relaxation for a graphite/epoxy (T300/5208) laminate. A viscoelastic finite element analysis of a double-lap joint with a steel bolt was conducted. Clampup forces were calculated for various steady-state temperature-moisture conditions using a 20-year exposure duration. The finite element analysis predicted that clampup forces relax even for the room-temperature-dry condition. The relaxations were 8, 13, 20, and 30 percent for exposure durations of 1 day, 1 month, 1 year, and 20 years, respectively. As expected, higher temperatures and moisture levels each increased the relaxation rate. The combined viscoelastic effects of steady-state temperature and moisture appeared to be additive. From the finite-element analysis, a simple equation was used to calculate clampup forces for the same temperature-moisture conditions as used in the finite-element analysis. The two sets of calculated results agreed well. Previously announced in STAR as N82-19320
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  • 78
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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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    Publikationsdatum: 2011-08-19
    Schlagwort(e): COMPOSITE MATERIALS
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  • 79
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    Impact properties of rubber-modified epoxy resin-graphite-fiber composites (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 80
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    Composite interlaminar fracture - Effect of matrix fracture energy (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Composites Technology Review; 6; 176-180
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    Effects of water during cure on the properties of a carbon/phenolic system (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: SAMPE Quarterly (ISSN 0036-0821); 15; 47-49
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  • 82
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    Effects of thermal cycling on mechanical properties of graphite polyimide (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Previously cited in issue 13, p. 2034, Accession no. A82-30101
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 21; 274-280
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  • 83
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    Failure characteristics of graphite-epoxy structural components loaded in compression (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Failure characteristics of compressively loaded graphite-epoxy components are described. Experimental results for both strength-critical laminates and structural components with postbuckling strength are presented. Effects of low speed impact damage and circular holes on compressive strength are discussed. Delamination and shear crippling failure mechanisms that limit the performance of strength-critical laminates are described. Transverse shear and skin-stiffener separation failure mechanisms that limit the performance of components with postbuckling strength are also described. The influence of matrix properties on compressive strength improvements for impact damaged laminates is discussed. Experimental data and results from a failure analysis for strength-critical laminates with cutouts are discussed and compared with impact damage results. Typical postbuckling test results are compared with analytical predictions. Previously announced in STAR as N83-12174
    Schlagwort(e): COMPOSITE MATERIALS
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  • 84
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    Modeling stiffness loss in boron/aluminum laminates below the fatigue limit (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Boron/aluminum can develop significant internal matrix cracking when fatigued. These matrix cracks can result in a 40 percent secant modulus loss in some laminates, even when fatigued below the fatigue limit. It is shown that the same amount of fatigue damage will develop during stress or strain-controlled tests. Stacking sequence has little influence on secant modulus loss. The secant modulus loss in unidirectional composites is small, whereas the losses are substantial in laminates containing off-axis plies. A simple analysis is presented that predicts unnotched laminate secant modulus loss due to fatigue. The analysis is based upon the elastic modulus and Poisson's ratio of the fiber and matrix, fiber volume fraction, fiber orientations, and the cyclic-hardened yield stress of the matrix material. Excellent agreement was achieved between model predictions and experimental results. With this model, designers can project the material stiffness loss for design load or strain levels and assess the feasibility of its use in stiffness-critical parts. Previously announced in STAR as N82-24298
    Schlagwort(e): COMPOSITE MATERIALS
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  • 85
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    Impact damage resistance of flat glass/cellular glass solar mirror experimental panels (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: An attempt is made to characterize the hail-impact behavior of a solar concentrator structural material which consists of thin, second-surface silvered glass sheets bonded to structural support panels of cellular glass. The resulting glass/cellular glass panel can be described as a thin, brittle plate supported by an elastic foundation, with the adhesive bonding the two as a third component. The plate will bend during impact. Attention is experimentally given to how variations in the characteristics or geometry of the flat glass, adhesive and cellular glass affect hail-impact damage resistance. The critical energy needed to cause impact damage is calculated from the critical velocity of the iceball by means of the kinetic energy formula. The complexity of this structural system and the variability of the specimens render it impossible to completely develop an analytical treatment for the prediction of impact damage resistance.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 86
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    Postbuckling behavior of graphite-epoxy panels (1984)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: ACEE Composite Struct. Technol.; p 137-160
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  • 87
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    Synthesis and toughness properties of resins and composites (1984)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: ACEE Composite Struct. Technol.; p 75-96
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  • 88
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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
    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: ACEE Composite Struct. Technol.; p 1-16
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  • 89
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    Comparison of toughened composite laminates using NASA standard damage tolerance tests (1984)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: ACEE Composite Struct. Technol.; p 51-74
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  • 90
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    Impact dynamics research on composite transport structures (1984)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: ACEE Composite Struct. Technol.; p 113-136
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  • 91
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    Tensile strength of composite sheets with unidirectional stringers and crack-like damage (1984)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: ACEE Composite Struct. Technol.; p 97-112
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  • 92
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    Worldwide flight and ground-based exposure of composite materials (1984)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: ACEE Composite Struct. Technol.; p 17-50
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  • 93
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    Mechanics of composite materials: Recent advances; Proceedings of the Symposium, Virginia Polytechnic Institute and State University, Blacksburg, VA, August 16-19, 1982 (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2016-03-09
    Beschreibung: The present conference on the mechanics of composites discusses microstructure's influence on particulate and short fiber composites' thermoelastic and transport properties, the elastoplastic deformation of composites, constitutive equations for viscoplastic composites, the plasticity and fatigue of metal matrix composites, laminate damping mechanisms, the micromechanical modeling of Kevlar/epoxy composites' time-dependent failure, the variational characterization of waves in composites, and computational methods for eigenvalue problems in composite design. Also discussed are the elastic response of laminates, elastic coupling nonlinear effects in unsymmetrical laminates, elasticity solutions for laminate problems having stress singularities, the mechanics of bimodular composite structures, the optimization of laminated plates and shells, NDE for laminates, the role of matrix cracking in the continuum constitutive behavior of a damaged composite ply, and the energy release rates of various microcracks in short fiber composites.
    Schlagwort(e): COMPOSITE MATERIALS
    Format: text
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  • 94
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    Tensile stress-strain behavior of hybrid composite laminates (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2018-12-01
    Beschreibung: A study was made of the stress-strain response of several hybrid laminates, and the damage was correlated with nonlinear stress-strain response and ultimate strength. The fibers used in the laminates were graphite, S-glass, and Kevlar. Some laminates with graphite fibers had perforated Mylar film between plies, which lowered the interlaminar bond strength. The laminate configurations were chosen to be like those of buffer strips in large panels and fracture coupons. Longitudinal and transverse specimens were loaded in tension to failure. Some specimens were radiographed to reveal damage due to edge effects. Stress-strain response is discussed in terms of damage shown by the radiographs. Ultimate strengths are compared with simple failure criteria, one of which account for damage.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 95
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    Study of utilization of advanced composites in fuselage structures of large transports (1984)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA-CR-172404 , NAS 1.26:172404 , LR-30786
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    ACEE composite structures technology (1984)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA-CR-172360 , NAS 1.26:172360
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    ACEE composite structures technology (1984)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA-CR-172359 , NAS 1.26:172359
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  • 98
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    ACEE composite structures technology (1984)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA-CR-172358 , NAS 1.26:172358
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  • 99
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    Advanced composite combustor structural concepts program (1984)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA-CR-174733 , NAS 1.26:174733 , PWA-5890-24
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    Durability and damage tolerance of Large Composite Primary Aircraft Structure (LCPAS) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: 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.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: NASA-CR-3767 , NAS 1.26:3767 , D6-49579
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