Abstract: The development of automobile lightweight requires more lightweight materials in vehicles replacing metallic materials and the structural adhesion technique provides a good option for joining dissimilar materials. The influence of environmental degradation on steel/aluminum and steel/CFRP adhesive joints is studied through simulating the variation of environmental temperature and relative humidity during automobile coating process and adopting both ductile and brittle adhesives. Experimental results reveal that adhesive joint behavior is greatly affected due to the automobile coating environment. Based on the comparison of different shear strength and the cohesive zone numerical modeling of the adhesive joints, the variation trend of different adhesives is obtained and the matching issues of CFRP and adhesive material parameters is analyzed. Through the analysis of scanning electron microscope on the fracture surface, the microscopic manifestation of the adhesive layer is analyzed to explain the macroscopic experimental results.

Key words: Automobile lightweight, Coating process, Cohesive zone model, Environmental degradation, Unbalanced adhesion