Bond durability of fatigued CFRP-steel double-lap joints pre-exposed to marine environment

Carbon fibre reinforced polymers (CFRPs) provide new age possibilities in structural restoration. However, limited research is available on the combined effect of marine environment and fatigue loading on the bond behaviour between CFRP and steel. This paper outlines an experimental investigation into the durability of CFRP laminate and sheeting patched double-lap joints under elevated temperature marine submergence. CFRP-steel double-lap joints were submerged in a 5% by weight NaCl solution for different durations up to 6 months at 20, 40 and 50 °C, while under a static tensile load. After pre-immersion, specimens were fatigue loaded for a pre-set number of cycles, and then statically tensile loaded to failure, for determination of the effect that aggressive environmental exposure introduces to the integrity of CFRP-steel double-lap joints. The rate of strength degradation was most rapid for samples pre-immersed for 1 month. Overall more than half of the specimens witnessed at least a 10% reduction in strength; with sheeting and laminate specimens respectively suffering up to a 28% and 20% loss in strength. The results show that even in short term exposures, the protection and maintenance of such rehabilitated structures is paramount in ensuring their strength and resilience over time.