STP787

    Strength and Fracture Characteristics of Graphite-Glass Intraply Hybrid Composites

    Published: Jan 1982


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    Abstract

    The strength, stiffness, fracture toughness, and crack propagation characteristics of graphite-glass intraply hybrid uniwoven and biwoven composite fabric materials are evaluated. The hybrid fabric plies were designed by modifying existing all-graphite fabrics in which were added single tows of S-glass spaced 6.35 mm (0.25 in.) apart, and 12.70-mm (0.5-in.)-wide strips of graphite were replaced with S-glass spaced 10.16 cm (4.0 in.) apart. The purpose of this hybrid design was to provide better damage tolerance and damage containment capabilities than the all-graphite system.

    The test program involved unidirectional and laminated coupons for strength and fracture toughness evaluation and 30.5-cm (12.0-in.)-wide orthotropic panels for crack arrestment evaluation. The panels were designed with glass strips aligned in discrete and staggered configurations. All tests involved room temperature dry and 121°C (250°F) 1.2 percent moisture-content specimens. The test results showed that the strength and stiffness properties for the hybrid materials were within 10 percent of the comparable all-graphite materials. However, the fracture toughness was approximately 44 percent higher for the hybrid systems and was not degraded by the 121°C (250°F) wet environment. A distinct crack arrestment capability was achieved only with the discrete strip configuration, with ultimate failure strain after crack arrestment in the 0.64 to 0.76 percent strain range.

    Keywords:

    composite materials, intraply hybrid, graphite-glass hybrids, damage tolerance, fracture toughness, crack propagation, crack arrest


    Author Information:

    Bhatia, NM
    Engineering Specialist, Northrop Corporation, Aircraft Division, Hawthorne, Calif.


    Paper ID: STP28481S

    Committee/Subcommittee: D30.05

    DOI: 10.1520/STP28481S


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