Research On Technology And Performance Of CFRP-AA5052 Electromagnetic Self-Piercing Riveted-Bonded Joint

Carbon fiber composite material(CFRP)is used as a lightweight material for automotive.Due to the high manufacturing cost of CFRP,it is now commonly used in combination with low-cost aluminium alloy(Al)to reduce the manufacturing cost of the vehicle.In this paper a reliable connection between CFRP and Al was realized by using electromagnetic self-piercing riveting-bonding hybrid connection technology.After that,CFRP-Al electromagnetic self-piercing riveted-bonded joints were taken as the research object.Firstly,the influence of process parameters on joints were explored.Secondly,the connection process of joints was simulated by finite element method.Finally,the performances of joints under multiple working conditions were studied.(1)The mechanical properties of electromagnetic self-piercing riveted-bonded joints with different discharge energies and lap lengths under quasi-static tensile shear were investigated.The results showed that the discharge energy affected the quality of the composite joints structure,and the joints with discharge energy of 7.7 k J had better quasi-static shear mechanical properties.In addition,the increase of the lap area length of composite joints in a certain range could obviously increase the shear strength,but when the lap area length reaches a certain length,increasing the lap area length could no longer increase the shear strength greatly.Moreover,by comparing the quasi-static tensile shear mechanical properties of electromagnetic self-piercing riveted-bonded joints with electromagnetic self-piercing riveted joints and adhesive bonded joints,it was shown that the composite joints had better mechanical properties.(2)Through the finite element simulation of the connection process of composite joints,the forming process of the joints and the stress changes of sheets and adhesive layer were analyzed.The results showed that the stress of non-rivet area of sheets away from rivet was small,while the stress of adhesive layer was mainly concentrated in the middle of joints overlap area near rivet,and the stress of adhesive layer decreased with the increase of distance from rivet.(3)The tensile shear test of composite joints under high speed loading(4 m/s 8 m/s 12m/s),mechanical properties of composite joints after salt spray corrosion and fatigue properties of hybrid joints under different stress levels were studied.The results showed that the shear load peak value and the energy absorbed during shear of composite joints increasing with the increase of loading speed.In addition,salt spray corrosion could affect the strength of the adhesive structure of the composite joints,and the effect of salt spray corrosion on the strength of the riveted structure was small because of the isolation effect of the adhesive structure on the corrosive solution,which made it difficult for the corrosive solution to penetrate into riveted structure inside the composite joints.Moreover,the fatigue performance of composite joints decreased with the increase of corrosion time.