The coupling effects of seawater aging and fatigue micro-crack on mechanical degradation of carbon fiber/epoxy plain woven composites

Carbon fiber reinforced plastics applied in the marine industry are often exposed to conditions of seawater and alternating loads for extended periods, which can cause the complex degradation process of the composites. In this work, the coupling effects of micro-cracks and the seawater aging on the carbon fiber/epoxy resin-based plain woven composites were experimentally investigated. The micro-cracks were introduced into the composites through the three-point bending fatigue load. The results indicate that the residual stress generated by different expansions between carbon fiber and epoxy resin that reduces the interfacial properties of the composite is the primary reason for seawater aging. Besides, seawater aging causes the bending strength of the specimens with fatigue damage to decrease more seriously than that of the undamaged specimens. This is because micro-cracks increase the specific surface area of the composites in contact with seawater to provide channels for seawater diffusion. The coupling effects suggest the maintenance cycle of the composite parts should be gradually reduced if micro-cracks occur in some composites.