E-Glass/Vinylester Composites in Aqueous Environments: Effects on Short-Beam Shear Strength

The paper present the results of extended (225 weeks) aqueous immersion of E-glass/vinylester composites, fabricated by the resin infusion process. Two different architectures (unidirectional and bidirectional) are tested to assess effects of temperature levels between 5 and 60°C on the short-beam shear strength. Tests show the competing effects of plasticization and postcuring balanced by hydrolytic degradation. The maximum reduction in performance is seen through immersion in deionized water at 60°C wherein pronounced interface and fiber level degradation is noted. Cycling between the two extremes of 5 and 60°C is also seen to cause acceleration of some interface and bulk resin related degradation phenomena. Experimental results obtained from hygrothermal aging at 23°C are compared with predictions based on an Arrhenius type model, and it is shown that good correlation can be obtained in sets where degradation mechanisms remain the same. Shortcomings of this type of model for life predictions are discussed to emphasize viability of use in design.