Moisture-induced thermal strains in glass fibre reinforced plastic compsites☆

Abstract The linear expansion coefficients of a unidirectional glass fibre reinforced polyester laminate have been used to predict the thermal strain developed in a (0/90/0) angle-ply laminate. Agreement between predicted and experimental values, obtained from the curvature of an unbalanced (0/90) laminate, is only obtained by the use of values of the expansion coefficient for a laminate containing absorbed water. Removing the absorbed water from unbalanced (0/90) laminates by isothermal heating at 100°C reduces the level of thermal strain developed at room temperature. This supports the view that the high level of thermal strain in polyester laminates results from water retained in the laminate after post-curing. In contrast water absorbed by a polyester angle-ply laminate at room temperature acts to reduce the level of thermal strain.