STP569: Microcrack Growth in Graphite Fiber-Epoxy Resin Systems During Compressive Fatigue

    Kunz, SC
    Postgraduate research student and lecturer, Cambridge University, Cambridge,

    Beaumont, PWR
    Postgraduate research student and lecturer, Cambridge University, Cambridge,

    Pages: 21    Published: Jan 1975


    Transfibrile crack extension in graphite fiber-epoxy resin composites was investigated in notched beams under cyclic compressive loading. Compressive fatigue crack growth was evaluated using selected linear elastic fracture mechanics parameters. A model was used to correlate observed micro-fracture processes with compressive crack extension behavior. Crack propagation underwent periods of deceleration and acceleration, and the crack growth rate dependence on material and environmental variables was determined. Transfibrile fatigue crack extension in unidirectional composites is a result of axial cracking and frequently resulted in crack arrest. Comparison of unidirectional composites with different epoxy resins showed the composite with the higher bond strength to be less susceptible to axial cracking along the fiber-matrix interface than the one with the lower bond strength. Crossplied (0°/90°) composites had lower compressive strengths, and through-specimen fractures resulted from axial cracking in the 0° plies, splitting in the 90° transverse plies, and splitting between plies. Exposure to a saline solution greatly increased axial cracking in all the composites and enhanced transverse ply splitting in the cross-plied material. Crack tip blunting and crack arrest due to solution-induced interfacial degradation was frequent.


    composite materials, graphite fibers, epoxy resins, failure mechanisms, environment, fatigue (materials)

    Paper ID: STP33166S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP33166S

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