Design of hole-clinching process for joining CFRP and aluminum alloy sheet

For the successful multi-material design of an automotive body, joining methods for dissimilar materials such as high-strength steel, aluminum alloy, and carbon fiber reinforced plastic (CFRP) are required for assembling automotive components comprising various materials. There are many methods for joining dissimilar materials, such as the use of self-piercing rivet, mechanical clinching, and friction stir welding. However, it is impossible to join a CFRP sheet and a metal sheet using conventional joining methods because of the former’s low ductility. This study proposes a hole-clinching process for joining CFRP with an AA6061 alloy sheet. In the holeclinching process, the AA6061 alloy sheet is indented into a hole in the CFRP and interlocked via deformation of the AA6061 alloy only. Thus, the CFRP-AA6061 joint is not restricted by the low ductility of CFRP. Initial hole-clinching tool shapes were determined based on the geometrical relationship between the hole-clinching tools and the interlocking shapes of the hole-clinched joint. The effect of process variables on the joinability of the hole-clinching process was investigated by FE-analysis. Based on the result of FE-analysis, the hole-clinched joint was designed with more than the required strength of 2.5 kN, as evaluated by performing a single lap shear test.