Durability of the liquid rubber-modified CFRP-steel interface under freeze-thaw cycles

An experimental investigation was carried out to evaluate the feasibility of using a liquid rubber-modified epoxy resin to improve the bonding durability between steel and carbon fiber-reinforced polymer (CFRP) plates in a freeze-thaw environment. Forty-eight CFRP-steel double strap joints were prepared, with a focus on two key factors: the number of freeze-thaw cycles (0, 50, 100, and 200 cycles) and the amount of liquid rubber in the adhesive (0%, 5%, 10%, and 15% by mass). The bond properties encompassing the damage mode, the ultimate capacity, and the bond-slip response of the CFRP-steel joints were examined, respectively. The study revealed that the ultimate capacity of the joints decreased as the freeze-thaw cycles increased. The ultimate capacity retention rate for unmodified joints, after undergoing 200 freeze-thaw cycles, was approximately 84.9%, while for the modified joints, it ranged from 90.5% to 96.4%. Furthermore, the impact of the freeze-thaw cycles and liquid rubber content on the key bond indicators in terms of the maximum shear stress tau max, initial slip S1, maximum slip Sf, and fracture energy Gf were ascertained, leading to the establishment of the bond-slip degradation relationship of the liquid rubber modified CFRP-steel interface under freeze-thaw environment.