Initiation of structural defects in carbon fiber reinforced polymer composites under hygrothermal environments

Abstract

Exposure to hygrothermal environments affects mechanical properties of laminated composites through two principle mechanisms, namely, moisture absorption and the structural deterioration due to it. Previous studies have indicated that moisture plays a positive role in carbon fiber reinforced polymer composites by alleviating their damage under impact. In this study, carbon fiber reinforced polymer composites were exposed to long-term hygrothermal ageing to investigate the possibility of the initiation of structural defects due to it and their influences on the various behaviors of the laminated composites. A major type of observable structural defects was identified and the related initiation mechanism was proposed. It was found for the first time that the structural defects formed during hygrothermal ageing in turn changed the moisture uptake profile of the laminated composites. The effects of structural defects on the impact resistance of carbon fiber reinforced polymer composites were exclusively evaluated after removing the absorbed moisture. Tensile testing on vacuum-oven-dried laminates was conducted to assist the understanding of the mechanical strength of the carbon fiber reinforced polymer composites exposed to the hygrothermal environments.