STP658: Moisture-Altered Viscoelastic Response of Graphite/Epoxy Composites

    Crossman, FW
    Research scientists and senior scientist, Lockheed Palo Alto Research Laboratory, Palo Alto, Calif.

    Mauri, RE
    Research scientists and senior scientist, Lockheed Palo Alto Research Laboratory, Palo Alto, Calif.

    Warren, WJ
    Research scientists and senior scientist, Lockheed Palo Alto Research Laboratory, Palo Alto, Calif.

    Pages: 16    Published: Jan 1978


    Abstract

    Results of experiments to evaluate the degree of moisture-induced swelling and plasticization in T300/934, T300/5209, GY70/339 composites are described. Swelling was found to be a nonlinear reversible function of equilibrium moisture content. Out-of-plane swelling was several times larger than in-plane transverse swelling in the unidirectional composites. Equilibrium moisture content was found to vary with exposure temperature as well as humidity in the 339 and 5209 matrix systems. The in-plane shear properties were determined as a function of time, temperature, and equilibrium moisture content, and master curves of temperature and moisture-compensated modulus versus time were constructed for each material. Nonsymmetric (04/904)T cross-plied laminates were employed to study the alteration of residual stresses in T300/5209 and GY70/339 as a function of temperature and moisture content. The level of residual stresses measured for a given equilibrium moisture content was found to be a function of the temperature at which the moisture was absorbed.

    Keywords:

    graphite/epoxy composites, viscoelasticity, residual stresses, stress relaxation, hygrothermal effects, moisture absorption, swelling, composite materials


    Paper ID: STP34865S

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP34865S


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