Study of Thermal and Hygrothermal Behaviors of Glass/Vinyl Ester Composites

Accelerated thermal and hygrothermal exposures were performed on S2-glass/vinyl ester composites. Effects of temperature, moisture, and exposure duration on some mechanical properties and microstructures of the composites were investigated, and thermal and hygrothermal degradation mechanisms were analyzed. It was found that the indentation resistance and compression strength of the composites showed an increase during a certain stage of the thermal exposure, which was attributed to the combined effects of thermal decission and an increase in crosslinking degree under elevated temperatures. Moisture, together with elevated temperature, had conspicuous deteriorating effects on some mechanical properties of the composites, and the property changes were more significant during the early stages of the hygrothermal exposure process. The influence of physical degradation induced by water was found to be less significant than that by chemical degradation resulting from resin decomposition. Microscopic observation showed that the matrix resin became fragmented and lost adhesion with fibers in the hygrothermally exposed composites.