Influence of water absorption on Mode I delamination in carbon/epoxy composite laminates

Abstract

This paper discusses the effects of demineralised water immersion on Mode I delamination behaviour of a carbon/epoxy composite. Tests were carried out at moisture contents of M = 0%,3%,5% and6%using double cantilever beam specimens. Results showed that compared to the dry condition, Mode I fracture toughness, G,C was slightly increased by 9% at M = 3%, bot dropped at M = 5% and 6%, with 6% and 17% reduction, respectively, Back calculated modulus showed that the values were varied within 20% compared to the tensile modulus except for M = 5% and 6% calculated by compliance based beam method. The normalised G,C was then fitted using a proposed residual toughness model. Furthermore, R-curve was observed after ageing, with the plateau value independent on the moisture content. Finally, scanning e1ectron micrographs revealed that matrix plasticisation,fibre debonding and microcracking were observed in aged specimens.