Innovative joining technology for the production of hybrid components from FRP and metals

Abstract

Abstract The joining of fiber-reinforced plastics (FRP) currently poses particular process engineering challenges. Adhesive bonding or mechanical joining is normally used for such joints. However, bonding processes require complex measures for surface pre-treatment, fixing concepts and usually requires long curing times. On the other hand, mechanical joining processes such as screws or semi-hollow punch rivets lead to significant damage to the reinforcing fibers. Although different approaches for the production of plastic/metal hybrids are being pursued, there is still a need for a joining process that adequately meets the technical and economic challenges of joining metal and FRP. An innovative joining concept bypasses the problems of conventional joining techniques by using small-scale form-fitting elements in combination with established resistance welding processes. The investigations presented here include temperature measurements of the welds by means of contact thermocouples and analysis of the matrix material after welding by IR spectroscopy. The mechanical properties of the joint were verified in static shear tensile tests on coupon samples and in 3-point bending tests on geometries close to the component. The investigations carried out so far show high static bond strengths, which can be increased by coordinated welding parameters and component geometries. The joining process offers many possibilities with regard to the design freedom of the joining zone, since the pin structures can be flexibly adapted with regard to their arrangement, number and geometry, so that different requirements can be met. The Multi-Spot-Joint generates a quasi-ductile post-break characteristic. Thermal damage to the plastic matrix can be avoided by the targeted use of particularly short resistance welding processes. No damage to the plastic matrix could be detected during the IR spectroscopy.