Effect of Coupled Long-Term Seawater Exposure and Bi-Axial Creep Loading (2:1) on Durability of Fiber-Reinforced Polymer-Matrix Composites

Abstract

Lightweight, high-strength fiber-reinforced polymer-matrix composites have attracted increasingly interests in their use for offshore operations. It is well known that long-term environmental attack and mechanical loading may cause microstructural damage and property degradation. The composite property degradation during long-term multi-axial loading in seawater has been a major concern because offshore structural systems are designed on the basis of either their stiffness or strength. Advanced composite systems must be capable of withstanding severe environments and still maintain their structural integrity in the designed life. In this paper, the effect of coupled long-term seawater exposure and bi-axialloading (2:1) on durability of advanced fiber composites is investigated. Accelerated bi-axial creep experiments have be, en conducted on carbon fiber/epoxy and glass fiber/epoxy composites in seawater. Critical material degradation and life prediction models are developed for the composite systems. With the aid of SEM observations, damage mechanisms and failure modes in the composites subject to combined long-term seawater exposure and bi-axial creep loading have also been identified. More general loading cases and their effects are reported elsewhere due to space limitation.