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    Defining the Adhesion Characteristics in Advanced Composites

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    The object of this study was to develop testing techniques that would permit a valid measure of the in-plane shear properties of advanced filament reinforced composites. The shear properties of glass and graphite reinforced epoxy materials were measured by short-beam shear and torsion tests. The specimen geometries and testing procedures necessary to make valid measures of shear properties were established for each of the tests and were found applicable to all materials studied. The torsion tube and torsion rod tests are the best available methods to accurately measure shear modulus, G, and shear strength, τu, by a single determination. The short-beam shear test at a span-to-depth ratio of 4 is capable of giving the same shear strength value as the torsion tests on composites only if a shear failure occurs. However, short-beam shear specimens of composites possessing good adhesion often fail in tension, and no correlation can be made between the calculated shear strengths obtained from short-beam shear testing and torsion testing. Torsion specimens then are required to measure shear strength. The theory that the maximum inter-facial shear strength that can be achieved in a composite is equal to the shear strength of the matrix material was examined. Torsion tests were conducted on unreinforced epoxy resin as well as on glass and graphite reinforced composites fabricated to achieve maximum adhesion. In no instance did the composite shear strength exceed that of the matrix resin (that is, about 14 ksi).


    composite materials, fiber composites, mechanical properties, torsion shear, short-beam shear, graphite epoxy, glass-fibers, epoxy laminates, fractography, evaluation, tests

    Author Information:

    Hanna, G. L.
    Group leaderpersonal member of ASTM, Monsanto Research Corp., Dayton, Ohio.

    Steingiser, Samuel.
    Scientistpersonal member of ASTM, Monsanto Research Corp., Dayton, Ohio.

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP49816S