Dynamic Mechanical Analysis of the Effect of Water on E-glass-Vinylester Composites

Abstract

Dynamic mechanical thermal analysis (DMTA) is used to investigate the degradation response of unidirectional pultruded E-glass-vinylester due to immersion in deionized water over a range of temperatures below its glass transition. It is found that moisture uptake which is overall Fickian in nature results in initial plasticization of the bulk matrix followed by matrix cracking, crack coalescence, fiber-matrix debonding, and irreversible matrix degradation. Post-cure, due to interaction with water and temperature, is noted to take place in the first 10-15 weeks, and competes with degradation mechanisms. Post-cure can be noted through large increases in storage modulus as well as in the loss tangent peak. A link can be drawn between storage modulus in the rubbery region, and the inter-crosslink molecular weight to further elucidate relative effects of post-cure and chain scission, which is seen on longer periods of immersion, but accelerated by higher temperatures.