STP743: Fracture Behavior of a Thick-Section Graphite/Epoxy Composite

    Shih, TT
    Senior engineers, Structural Behavior of Materials Department, Westinghouse R&D Center, Pittsburgh, Pa.

    Logsdon, WA
    Senior engineers, Structural Behavior of Materials Department, Westinghouse R&D Center, Pittsburgh, Pa.

    Pages: 22    Published: Jan 1981


    Abstract

    In order to explore the possibility of utilizing composites as structural materials for generator retaining rings, the fracture behavior of an experimental thick-section [54 mm (2.125 in.)] graphite/epoxy composite was examined. Rectangular bend bar specimens of various cross-sectional dimensions were tested in three-point bending to determine the shear strength of the composite. Edge-notch-bend and center-notched-tension specimens with various notch depths were used to determine the fracture toughness of the composite. These tests served to permit an evaluation of the applicability of linear elastic fracture mechanics (LEFM) to composite materials in general and thick-section composites in particular. Results show that (1) LEFM is not directly applicable to thick-section composites with cracks perpendicular to the fiber orientation; (2) the test composite is insensitive to cracks in a plane perpendicular to the fibers, and the load-carrying capability can be calculated based on net section considerations; and (3) the failure mode of the test composite under three-point bending is interply shear failure. The interply shear strength equaled 24.6 MPa (3.5 ksi).

    Keywords:

    graphite, epoxy, composites, shear strength, fracture toughness


    Paper ID: STP28805S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP28805S


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