Durability of glass-fibre reinforced polymer composites in aqueous and high temperature environments

In this investigation glass-fibre/epoxy-resin laminates with [+/-45, 90(3)](S) lay-ups were immersed in distilled water at different temperatures. In particular, three sets of coupon specimens were exposed for about 2 years to varying histories consisting of dry conditions or immersion-dry-out-and-re-immersion treatments, while keeping the temperature constant for each set. Moisture absorption behaviour and the effect of the environment and temperature on the mechanical properties were determined. It was found that there was a strong synergy between temperature and environment. Immersion in distilled water at ambient temperature did not affect the mechanical properties, on the contrary, it increased the threshold strain to crack initiation. However, specimens immersed at T>50degreesC showed deterioration in all respects. Exposure to cycles of wet and dry conditions at high temperatures were the most damaging environment. The underlying damage mechanisms and microscopic causes leading to the deterioration of the mechanical properties are discussed.