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    STP674

    The Room Temperature Moisture Kinetics of Kevlar 49 Fabric/Epoxy Laminates

    Published: 0


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    Abstract

    Hygrothermal effects can significantly influence the failure behavior of high performance epoxy-based composites. As such, it is necessary to determine, for one, the moisture diffusion rates in the composite's principal axes so that moisture densities and distributions can be estimated for life-cycle exposures. In this study, moisture diffusion coefficients are determined for quasi-isotropic Kevlar 49 181-style fabric reinforced Narmco 5208 epoxy laminates, and for the epoxy and fabric components individually. A microbalance technique is employed to monitor continuously the percentage weight gain of specimens exposed to 76 percent relative humidity at room temperature. The anisotropy of moisture diffusivity in the composite laminates is determined by use of a slope ratio (absorption versus time) technique and specimens of appropriate geometry. Results show that moisture diffuses in the laminate plane (6.1 × 10-8 cm2/s) two orders of magnitude faster than through the thickness (1.7 × 10-10 cm2/s). These values compare to a resin diffusivity of 6.5 × 10-10 cm2/s. It is speculated that the rapid in-plane diffusion is due to the preferential diffusion of moisture in the filament along its length.

    Keywords:

    composite materials, Kevlar 49, epoxy resin, laminates, moisture, diffusion


    Author Information:

    Allred, RE
    Members of technical staff, Sandia Laboratories, Albuquerque, N. Mex.

    Lindrose, AM
    Members of technical staff, Sandia Laboratories, Albuquerque, N. Mex.


    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP36916S