Hygrothermal aging effects on fatigue of glass fiber/polydicyclopentadiene composites

We investigated the effects of hygrothermal aging on the tension-tension fatigue behavior of unidirectional (UD) glass/polydicyclopentadiene (pDCPD) composites. Samples were immersed in deionized (DI) water and salt water, and glass/epoxy composites were used as a benchmark for comparison. Composites of pDCPD showed less water uptake and superior fatigue performance compared to similarly aged epoxy composites, a distinction attributed to the intrinsic hydrophobicity of the pDCPD resin. Superior fiber-matrix interface adhesion in pDCPD composites accounted for the greater strength retention after aging. Degradation of fiber and interface were coupled but not synchronous: glass fiber degradation was determined by aging time, while interface degradation depended primarily on moisture level. Salt water influenced the amount of water absorption, but no salt water corrosion was observed for either composite.