STP580: Prediction of Transverse Strength and Scatter in Test Data for Unidirectional Composites

    Greszczuk, LB
    McDonnell Douglas Astronautics Company, Huntington Beach, Calif.

    Pages: 16    Published: Jan 1975


    Abstract

    An approximate theory is presented for predicting the transverse tensile strength of composites from the properties of constituents and composite microstructure. The theory takes into account internal triaxial stress concentrations caused by fibers, triaxial stress concentrations caused by voids, and the interaction of stress concentrations from fibers and voids. The theoretically predicted transverse tensile strength is compared with test data for glass-epoxy and graphite-epoxy composites made with various resin systems. To establish the causes for test data scatter, systematic studies are conducted on the influence, on the predicted transverse strength, of fiber content, void content, specific gravity, and resin strength variations within the various groups of test specimens. The results of these studies are used to predict the scatter in transverse strength of composites. These scatter predictions are useful in identifying the major causes and variables which need closer control in order to minimize the scatter in test data and thereby improve the reliability of composites.

    Keywords:

    composite materials, fibers, transverse strength, failure, criteria, mechanical properties, voids, porosity, stress concentration, brittle fracturing, nonbrittle fracturing, graphite, glass, scatter predictions, reliability, epoxy resins


    Paper ID: STP32316S

    Committee/Subcommittee: D30.05

    DOI: 10.1520/STP32316S


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