THE EFFECTS OF SORBED MOISTURE ON RESIN-MATRIX COMPOSITES

The effects of water absorption have been investigated on the diffusio n behavior, moisture-induced expansion, and fracture properties of the rmoset and thermoplastic resin-matrix composites. The composite materi als were submerged in distilled water at temperatures res from 45-degr ees-C to 90-degrees-C for more than 8,000 h. Moisture saturation level s were considerably higher in the thermoset composites than in the the rmoplastic composite. Moisture sorption in the graphite/epoxy composit e exhibited both classical Fickian and non-Fickian diffusion behavior. Deviant, non-Fickian behavior was related to chemical modification an d physical damage in the composite. Moisture sorption in thermoplastic resin composites follows Fickian diffusion rather closely. Anomalous moisture expansion behavior in graphite-epoxy composites was attribute d to environmental-induced damage of the laminate. Sorbed moisture red uced the delamination fracture toughness (DFT) of a thermoset composit e, whereas moisture sorption had virtually no effect on the DFT of a t hermoplastic composite.