Effect of loading rate on the failure of BFRP-Aluminum alloy single lap joints after hygrothermal aging

With the increasing scale of the automotive industry, the mixed application of multiple materials and bonding technology have become indispensable means to achieve lightweighting. In this paper, accelerated aging experiment and tensile test were developed to study the effect of loading rate (1 mm/min–100 mm/min) on the failure of BFRP-Aluminum alloy single lap joint after hygrothermal aging (0 days–28 days). The aging mechanism of the adhesive and BFRP in the hygrothermal environment was also analyzed by Fourier transform infrared and differential scanning calorimetry. The test results showed that the joint failure strength varied with the hygrothermal aging time and loading rate, with the former showing a negative correlation and the latter a positive correlation. Combined with the joint failure surface, it was found that the joint strength decrease was mainly caused by the hydrolysis reaction of the adhesive and the interfacial failure of the joint. A regression model was developed to characterize the failure strength of the joints under different loading rates in the hygrothermal environment, and it was concluded that the aging time was more significant than the loading rate on the strength of the joints.