Evaluation of strength degradation behavior and fatigue life prediction of plain-woven carbon-fiber-reinforced plastic laminates immersed in seawater

The effect of long-term seawater immersion on the mechanical properties and fatigue life of plain-woven carbon-fiber-reinforced plastic (CFRP) laminates was investigated. Under tension loading, the static strength and low-cycle fatigue strength of the CRFP laminates greatly decreased owing to the rapid growth of interface debonding and delamination. However, under compression loading, the fatigue strength of the CRFP laminates dramatically decreased in the entire fatigue region as fiber buckling was likely to occur. These findings indicate that the fatigue strength degradation differed depending on the stress ratio and deterioration of the fiber/matrix interface strength. In addition, the fatigue life after seawater immersion was predicted using Epaarachchi and Clausen's model and constant life diagrams. These models were shown to accurately reflect the decrease in fatigue strength resulting from seawater immersion and can thus be used for fatigue life prediction of CFRPs after long-term immersion in seawater.