Characterization of fatigue and combined environment on durability performance of glass/vinyl ester composite for infrastructure applications

As composite materials find increased use in infrastructure applications, where design lives are typically much longer than those in aerospace, the issue of durability becomes more critical. The tolerance of composites to damage induced by cyclic loading and moisture ingress is of utmost importance. This study highlights the effects of short-term cyclic moisture aging on the strength and fatigue performance of a glass/vinyl ester pultruded composite system. In particular, it addresses the change in quasi-static properties and tension–tension (R=0.1) fatigue behavior of a commercial glass/vinyl ester system in fresh and salt water. The quasi-static tensile strength was seen to reduce by 24% at a moisture concentration of 1% by weight. This reduction in strength was not recoverable even when the material was dried, suggesting that the exposure to moisture caused permanent damage in the material system. Even though the fatigue damage process of the unaged or ‘as-delivered’, fresh-water- and salt-water-saturated material was similar, the cyclic moisture absorption–desorption experiments altered the fatigue performance of the composite system tested. Results were consistent with Mandellʹs postulate that fatigue failure in glass-fiber-reinforced polymeric composites is a fiber-dominated mechanism with a characteristic slope of 10% UTS/decade.