Effects of elevated temperature on epoxy bonded CFRP-to-steel joints in Mode I fracture

This study was undertaken to further knowledge in relation to the effect of elevated temperature on performance of adhesively bonded CFRP-to-steel joints subjected to peel loading. Two epoxy adhesives, Adhesive A and Adhesive B, were assessed with regard to their aging behaviour at two elevated temperatures and for two exposure periods. Adhesive coupon specimens and a modified Mode I fracture test arrangement for use with dissimilar materials was used in the test programme. In total, thirty CFRP-to-steel bonded specimens and thirty adhesive coupons were evaluated. Exposure of coupons of both adhesives to elevated temperatures resulted in a considerable reduction in elastic moduli. Maximum strain of adhesive coupons fabricated with Adhesive A and B experienced an overall average increase of 30% and 39%, respectively, after exposure to elevated temperatures. The maximum failure load of fracture specimens manufactured with Adhesive A and B reduced up to 9% and 12%, respectively, after exposure to elevated temperature. Despite possessing higher strain energy release rate and higher load carrying capacity of fracture specimens manufactured with Adhesive B compared to Adhesive A, the bonding performance of Adhesive B is more affected by elevated temperature and this needs to be noted when using Adhesive B in areas with hot climates.