Environmental effects on deformation, strength, and degradation of unidirectional glass‐fiber reinforced plastics. II. Experimental study

Abstract

Glass‐fiber reinforced epoxy (GRP) and unfilled epoxy specimens were exposed to different environmental conditions consisting of hot‐ and cold‐water absorption and subsequent drying. Effects of the environmental history on deformational and strength characteristics of the composite material were investigated.GRP specimens exposed to hot water undergo pronounced degradation, which sets in shortly after exposure and is associated with a significant irrecoverable weight loss. Degraded specimens are characterized by higher void content and lower strength compared with their cold‐water and reference counterparts. The degradation process is attributed to penetration of water into the matrix‐fiber interfaces and is followed by an attack, at high temperatures, on the glass‐fibers surface and coupling agent. As a result, glass constituents are leached out and then removed from the system by diffusion.The degradation effect was also confirmed by micro‐observation of the fractured surfaces and by infra‐red spectroscopy. A simple and effective testing method is recommended, permitting detection of degradation onset and its progress by simultaneous measurement of weight and dimensional changes with time.