Friction-assisted clinching of Aluminum and CFRP sheets

The employment of a rotating tool when joining thin aluminum sheets with Carbon Fiber Reinforced Polymer (CFRP) laminates by means of clinching is investigated. This new process, named friction-assisted clinching, was aimed at increasing the aluminum formability and at the same time reducing the joining forces. An instrumented servo-drilled machine was employed to measure the plunging force and torque during the joining process. The influence of the main process parameters (hole diameter in the CFRP sheet, die anvil depth, tool fillet radius and residual sheet thickness) on quality of the joints and strength was determined. Morphological analysis and mechanical characterization based on single lap shear tests were performed to evaluate the difference among the joints. According to the achieved results, the employment of friction clinching allowed increasing dramatically the material formability and enabled the production of joints without fractures even with sharp pin tools. The advantages of this advanced joining process can be potentially applied to conventional clinching of materials with poor ductility either friction clinching allows increasing the undercut dimension by using sharper tools, which produces higher material flow and leads to an increase in the joint strength.