THE EFFECTS OF A WATER ENVIRONMENT ON ANOMALOUS ABSORPTION BEHAVIOR IN GRAPHITE-EPOXY COMPOSITES

The effects of a water environment on moisture (H2O) absorption characteristics of a unidirectional T300/934 graphite/epoxy composite material have been investigated by the measurement and analysis of weight change, hygrothermal induced expansion, surface crack formation, and surface mass loss. Specimens were immersed in distilled water at 45, 60, 75, and 90 degrees C for more than 8000h. Weight-change profiles for the composite exhibited divergence from the theoretical Fickian diffusion law. Scanning electron microscopy (SEM) and dimension measurements revealed clear evidence of surface peeling and dissolution of the specimen. A crack/mass-loss model has been used in order to explain the behavior of the composite material during the water absorption process. The general characteristics of water-induced weight gain in graphite/epoxy composites are discussed with respect to the moisture diffusion phenomenon and deviations in the weight-change profiles.