The use of metal-plastic composites (MPCs) plays an important role for lightweight products. MPCs provide an innovative substitute for solid metal sheets due to their low weight, excellent stiffness, and due to their thermal and acoustical insulation. A challenge that links all the different applications is the need to efficiently process the MPCs with high quality and join them with other materials, using suitable joining techniques. Due to their special features (layer structure, material mix, etc.), conventional manufacturing processes are therefor only of limited or of no use at all. In particular, the polymer core layer is a barrier for the application of conventional joining methods. This contribution presents a novel joining approach for MPCs, a hybrid spot welding process, using a specially developed hybrid spot welding gun. In its main characteristic the sonotrode of an ultrasonic unit also functions as an electrode of a resistance spot welding (RSW) unit. This allows the local melting and displacement of the polymer core of the MPC by the energy of ultrasonic waves and subsequently joining the metal sheets of the MPC with another metal sheet by RSW in a single process step.
As part of the investigation with the hybrid spot welding gun different energy directors for a fast displacement of the polymer were determined by means of FE simulation and experimental examinations. Furthermore, destructive, and non-destructive tests of joints were processed. The result is a short time of the overall welding and forming process and a good shear strength of the joints.