Environmental Effects on the Mechanical Properties of Glass Fiber/Epoxy Resin Composites. Part 1. Effect of Static Immersion in Water on the Tensile Strength of Cross-Ply Laminates

This report describes studies to determine the effect of water absorption on the tensile strength of 90090 deg laminates. The ultimate strength was found to decrease continuously with increasing amounts of water absorption. Yield stress first increased and then decreased to form a broad maximum. Assuming perfect bonding between the laminae, the change of yield stress could be predicted by overlapping the decrease of interlaminar residual stress as a prestress and the change of failure stress of 90 deg lamina. Anisotropic volume expansion of the laminae by water absorption is considered to be responsible for the relaxation of interlaminar residual stress.