Water immersion aging of polydicyclopentadiene resin and glass fiber composites

We present an investigation of the effect of long-term water immersion aging on the thermal/mechanical properties of a ruthenium-catalyzed polydicyclopentadiene (pDCPD) polymer and associated composites, using an epoxy resin system as a benchmark. The pDCPD neat polymer showed low-level water absorption after one year of aging due to inherent hydrophobicity. No plasticization was observed for pDCPD, while significant plasticization occurred for the epoxy. Salt water aging and deionized water aging had identical effects on pDCPD and composites, while epoxy materials aged in salt water showed less water absorption compared to aging in deionized water. We also measured the fiber-interface strength before and after aging of composites using single-fiber push-out tests. Aging caused decreases in interface strength, and these decreases led to a decline in composite fatigue strength.