Two-steps clinching of aluminum and Carbon Fiber Reinforced Polymer sheets

The present paper investigates the effectiveness of two-steps clinching for joining aluminum and Carbon Fiber Reinforced Polymer (CFRP). To this end, different reshaping tools were involved after joining by clinching with split dies. The reshaping force was also varied. Single lap shear tests of simple clinched and reshaped specimens were performed to determine the influence of the process conditions on the mechanical behavior of the joints. The morphology and geometry of joints were analyzed to understand how the reshaping step influences the main quality criteria of the joints and the damage produced on the CFRP sheet. According to the experimental results, simple clinched connection failed by pullout; thus, the critical parameter was the undercut. The reshaping method, using optimized tools enabled to increase the strength of the joints by 32%. Such an improvement was due to an increase in the undercut that resulted from a higher and improved material flow. The main defects that may appear in these joints have been identified as well as their causes.