The Effect of High-Temperature Degradation on the Mode I Critical Strain Energy Release Rate of a Graphite/Epoxy Composite

    Volume 17, Issue 3 (July 1995)

    ISSN: 0884-6804

    CODEN: CTROAD

    Page Count: 7


    Bakis, CE
    Graduate research assistant and associate professor, The Pennsylvania State University, University Park, PA

    Walsh, TF
    Graduate research assistant and associate professor, The Pennsylvania State University, University Park, PA

    Abstract

    The double cantilever beam (DCB) test was used to determine the effects of high-temperature degradation on the Mode I critical strain energy release rate (GIC) of a continuous fiber-reinforced polymer-matrix composite material. The composite material investigated was IM7/8551-7A graphite/rubber-toughened epoxy system. Delamination starter films of two different thicknesses were used: 25.4 µm and 12.7 µm. High-temperature degradation was accomplished by placing the specimens on a wire rack in a forced-air convection oven held at 177°C. A continuous flow of fresh laboratory air existed at all times. GIC decreased with increased exposure, showing a 40% reduction after 8000 h. The specimens with thicker inserts showed a higher GIC. Weight loss of the material occurred throughout the aging cycle, indicating that thermo-oxidation was occurring. GIC was not affected by the wedging open of the precrack during exposure. Crack propagation in the unexposed specimens occurred in the matrix material, whereas for the exposed specimens, it occurred along the fiber-matrix interface. This indicated possible exposure-induced interfacial degradation.


    Paper ID: CTR10487J

    DOI: 10.1520/CTR10487J

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    Author
    Title The Effect of High-Temperature Degradation on the Mode I Critical Strain Energy Release Rate of a Graphite/Epoxy Composite
    Symposium , 0000-00-00
    Committee D30