Effects of ultraviolet radiation and associated elevated temperature on mechanical performance of steel/CFRP double strap joints

Although extensive studies of the bond between steel and CFRP under various environmental exposures have been carried out, the effects of UV have not been examined to date. This knowledge gap is addressed in this paper. Specimens (epoxy adhesive, CFRP laminates and steel/CFRP adhesively-bonded joints) were exposed to UV for various time periods and identical reference specimens were exposed to only thermal environments without UV. It was found that UV exposure does not influence the tensile strength of CFRP composites. The tensile strength of the adhesive reduced by 13.9% while modulus showed a significant increase by 105% after 744 h of exposure. The tensile modulus of adhesive exposed to only thermal environment also increased by 38%, considerably less than that induced by UV exposure. The UV exposure also led to a decrease in joint strength but an increase in stiffness, caused by the temperature effect rather than the UV rays.