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  • 1
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    Toughening of PMR composites by gradient semi-interpenetrating networks (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The toughening of the PMR-15 and LARC RP-46 high temperature thermosetting polyimides is presently attempted through the construction of a semiinterpenetrating network at ply interfaces through the use of the Matrimid 5218 thermoplastic polyimide powder, whose 315-320 glass transition temperature is compatible with the PMR matrices. The 60 vol pct fiber composites thus prepared for the two resins, with and without toughening, were comprehensively characterized in flexure, tension, intralaminar and short beam shear, compression and quasi-isotropic short-block compression, as well as modes I and II interlaminar fracture toughness and compression after impact.
    Keywords: COMPOSITE MATERIALS
    Type: In: International SAMPE Symposium and Exhibition, 37th, Anaheim, CA, Mar. 9-12, 1992, Proceedings (A93-15726 04-23); p. 690-704.
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Response of composite materials to low velocity impact (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Orthotropic and quasiisotropic laminates clamped at the edges were impacted by an instrumented falling weight. Five matrix materials, comprising a baseline epoxy, two toughened thermosets, and amorphous and crystalline thermoplastics were studied. For each material, the projected damage area and residual compression strengths and strains were determined as a function of impact energy. Principal conclusions are: (1) incipient damage associated with a prominent load drop during the impact test seems to be decisive for residual properties; (2) subtle rate effects are present with some materials; and (3) results from the small scale tests parallel those in standard tests and may be adequate for screening purposes.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-102755 , NAS 1.15:102755 , AVSCOM-TM-90-B-018
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Impact response of composite materials (1991)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Composite materials composed of carbon fibers and resin matrices offer great promise in reducing the weight of aerospace structures. However they remain extremely vulnerable to out of plane impact loads, which lead to severe losses in strength and stiffness. The results of an experimental program, undertaken to investigate the low velocity impact damage tolerance of composite materials is presented. The objectives were to identify key neat resin/composite properties that lead to enhancement of composite impact damage tolerance and to find a small scale test that predicts compression after impact properties of panels. Five materials were selected for evaluation. These systems represented different classes of material behavior such as brittle epoxy, modified epoxies, and amorphous and semicrystalling thermoplastics. The influence of fiber properties on the impact performance was also studied in one material, i.e., in polyether ether ketone (PEEK). Several 24 and 48 ply quasi-isotropic and 24 ply orthotropic laminates were examined using an instrumented drop weight impactor. Correlations with post impact compression behavior were made.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-187896 , NAS 1.26:187896
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Development of polysilsesquioxane composites (1990)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Polymer composites are increasingly being required to operate for prolonged durations at higher temperatures than in the past. Hence there have been increased efforts devoted to synthesizing and characterizing polymers capable of withstanding temperatures greater than 300 C for long periods. Several such organic polymers have been investigated in recent times. This research effort seeks to enquire if inorganic polymers can be utilized to provide the same result. Ceramics have long been recognized as providing superior thermal properties for demanding applications. However, the extremely high softening temperatures preclude their being shaped into complex shapes through melt processing techniques common to organic polymers. One approach towards solving this problem has been through the development of preceramic polymers. These are capable of being processed in the polymeric state with ease, and subsequently being pyrolyzed to ceramic structures. This experimental study is aimed at studying the feasibility of using preceramic polymers (that have not been subject to the pyrolysis step) as high performance composite matrices for high temperature applications. A preliminary study of this nature is not geared towards optimizing mechanical properties suitable for such composites. Rather, this study attempts to process such resins in composite form and suitably characterize their properties.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-180263 , NAS 1.26:180263
    Format: application/pdf
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  • 5
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    Response of composite materials to low velocity impact (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Orthotropic and quasi-isotropic laminates clamped at the edges were impacted by an instrumented falling weight. Five matrix materials, comprising a baseline epoxy, two toughened thermosets, and amorphous and crystalline thermoplastics were studied. For each material, the projected damage area and residual compression strengths and strains were determined as a function of impact energy. Principal conclusions are: (1) incipient damage associated with a prominent load drop during the impact test seems to be decisive for residual properties; (2) subtle rate effects are present with some materials; and (3) results from the small scale tests parallel those in standard tests and may be adequate for screening purposes.
    Keywords: COMPOSITE MATERIALS
    Type: International SAMPE Symposium and Exhibition; Apr 15, 1991 - Apr 18, 1991; San Diego, CA; United States
    Format: text
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    NASA TECHNICAL REPORTS
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