Correlations Between Micromechanical Failure Processes and the Delamination Toughness of Graphite/Epoxy Systems

    Published: Jan 1987

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    A combination of macroscopic delamination fracture toughness, scanning electron microscope (SEM) real-time fracture observations, and postfracture morphology were used to study the micromechanical processes of delamination failure in several graphite/epoxy systems.

    Strain energy release rate GIc, GIIc, and mixed mode GI&IIc were obtained from unidirectional double cantilever beam specimens. Comparisons of these energy release rates with the resulting fracture surface mophology are used to clarify the relative importance of the formation of hackles and the fiber matrix interface adhesion to delamination toughness under Mode I, Mode II, and mixed Mode I & II loading conditions.

    Real-time fracture observations of composite delamination in the SEM revealed the microprocesses of microcrack formation and coalescence. These observations coupled with GIc for the neat material, determined from compact tension specimens, provide insight on how resin toughness can be translated into composite delamination toughness.

    The implications of hackle formation and their importance in the failure analysis of graphite/epoxy systems are discussed.


    graphite/epoxy composites, delamination, fracture, toughness, failure analysis

    Author Information:

    Hibbs, MF
    Graduate research assistant and professor, Texas A&M University, College Station, TX

    Bradley, WL
    Graduate research assistant and professor, Texas A&M University, College Station, TX

    Committee/Subcommittee: D30.06

    DOI: 10.1520/STP25615S

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