STP601: Fracture Toughness of ATJ-S Graphite and CVD Carbon-Carbon Composites at Elevated Temperatures

    Hettche, LR
    Superintendent and research physicist, Engineering Materials Division, Naval Research Laboratory, Washington, D.C.,

    Tucker, TR
    Superintendent and research physicist, Engineering Materials Division, Naval Research Laboratory, Washington, D.C.,

    Pages: 16    Published: Jan 1976


    Abstract

    The fracture toughness and flexural strength of ATJ-S polycrystalline graphite and two chemical-vapor-deposited (CVD) carbon-carbon composites (CVD/felt and CVD/filament wound) are reported for temperatures between 20 and 2000°C. For both the ATJ-S and CVD/felt materials, the toughness and strength are found to rise linearly with increasing temperature. The properties of CVD/filament wound composite exhibit the greatest directional dependence of the materials examined. When the machined notch is oriented perpendicular to the reinforcing filaments, the CVD/filament wound specimens fail by delamination, precluding any fracture toughness determination.

    Results of scanning and transmission electron microscopy of the fracture surfaces are also presented. In the case of the polycrystalline graphite, a preference for interfacial separation and, to a lesser extent, cleavage separation are observed.

    Keywords:

    fractures (materials), polycrystalline, graphite, composite materials, graphite composites, high temperature tests, flexural strength, fractography, crack propagation


    Paper ID: STP28640S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP28640S


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