Identification and Evaluation of Progressive Thermal Degradation Caused by Carbamate Formation in Cyanate Ester Resin-Based Composites

摘要

The effect of moisture during cure on the mechanical and thermal performance was evaluated for a series of cyanate ester composite laminates. Data presented in our investigation show that the amount of carbamate formation is inversely proportional to the glass transition temperature (T_g) of the cured composite and is typically localized on the outer surface plies adjacent the moisture source. Even though the majority of the composite may remains largely unaffected, the T_g of the localized areas will show sharp decreases which correlate with strength as verified by flatwise tensile tests. Additionally, our test data show that performing just one T_g measurement after cure will not necessarily provide a valid assessment of the state of the composite since additional degradation may occur with subsequent thermal exposure. Accordingly, a second dynamic mechanical analysis (DMA) measurement should be performed after an extended, elevated temperature, post-treatment thereby allowing direct assessment of carbamate degradation.