Effect of Water Sorption on Performance of Pultruded E-Glass/Vinylester Composites

The degradation response of pultruded E-glass vinylester composites immersed in deionized water at 23, 40, 60, and 80°C is characterized through mechanical testing (tension and short-beam-shear), moisture uptake, and dynamic mechanical thermal analysis (DMTA). Tests are conducted after periods of immersion and subsequently after a period of drying out to assess regain of performance due to reduction in sorbed moisture content. It is seen that, although the initial effect of immersion is just matrix plasticization, increased periods of immersion and/or use of elevated temperatures results in hydrolysis, interfacial debonding, microcracking, and even degradation of the fiber itself. Not only do these mechanisms of irreversible degradation result in significant drops in performance, but further, these decreases are increasingly irreversible. Both inductively coupled plasma and Fourier transform infrared studies indicate leaching of composite constituents.