STP1110: Mixed-Mode Fracture in Fiber-Polymer Composite Laminates

    Hashemi, S
    Research fellow, professor, and professor, Imperial College of Science, Technology, and Medicine, University of London,

    Kinloch, AJ
    Research fellow, professor, and professor, Imperial College of Science, Technology, and Medicine, University of London,

    Williams, G
    Research fellow, professor, and professor, Imperial College of Science, Technology, and Medicine, University of London,

    Pages: 26    Published: Jan 1991


    Abstract

    Mode I, Mode II, and Mixed-Mode I/II interlaminar tests on unidirectional carbon-fiber composites have been conducted using beam specimens. Both a thermosetting-based (an epoxy resin) matrix and a thermoplastic-based (poly(ether-ether ketone)) matrix have been employed. The fracture energy, Gc, has been ascertained and the various correction factors that need to be applied if accurate results are to be obtained are described. Where Mixed-Mode I/II loadings may have been present, the measured value of Gc has been partitioned into the separate GI and GII components. The experimental results all suggest that the partitioning of G on a global energy basis, as opposed to using local stress-field solutions, is the most appropriate for the laminates. Thus, the differences in energy absorption are a consequence of opening as opposed to sliding, and the symmetry, or otherwise, of these motions is not important. It is thus apparent that a global energy analysis is entirely satisfactory and appropriate for these types of systems. Finally, it is also shown that when the failure locus is plotted in the form of GI versus GII then it may be theoretically described by a simple interaction parameter model, where the interaction parameter, Ii, has a linear dependence upon the value of GI/G.

    Keywords:

    composite materials, failure criterion, fracture mechanics, interlaminar failure, local stress-field, mixed-mode tests, fracture, fatigue (materials)


    Paper ID: STP17717S

    Committee/Subcommittee: D30.06

    DOI: 10.1520/STP17717S


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