A systematic study on the failure behaviors of aluminum alloy/composite bonded joints exposed to various typical aging environments for automobiles

To systematically and comprehensively analyze the effects of different aging environments on the aging failure of aluminum alloy/CFRP (Carbon Fiber Reinforced Plastics) composite bonded shear and butt joints, seven typical aging environments of room temperature (23 degrees C/20%RH, RT), high-temperature (80 degrees C/20%RH, HT), low temperature (-40 degrees C, LT), temperature cycles (-40 similar to 80 degrees C/20% RH, TC), immersed in water at room temperature (IRT), high temperature and high humidity (80 degrees C/95%RH, HTHH), and hygrothermal cycles (-40 degrees C similar to 80 degrees C/95%RH, HC) were selected to perform aging tests. The composition analysis revealed that the adhesive underwent the most significant post-curing in HT, followed by TC, while LT had almost no effect on the adhesive. It was also found that the degree of moisture absorption and hydrolysis of the adhesive in IRT, HTHH and HC decreased sequentially. A single temperature or humidity environment had small effect on the failure strength of bonded joints less than 20%, increasing temperature or humidity could further reduce the failure strength by about 30%, and periodically changing the temperature or humidity had the greatest effect on the failure strength by more than 40%. ANOVA (Analysis of Variance) shows that all the single factors of aging time, load type, or aging environment had significant effects on the failure strength, but the aging environment had the greatest effect. Multifactor coupling effects on the failure strength was not significant, except for the coupling effects of aging environment and aging time.