Joining of intrinsically manufactured frp/metal components to metallic structural elements by resistance spot welding

• Applicant: Professor Dr.-Ing. Jürgen Fleischer
• Subject Area: Production Automation and Assembly Technology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 418238897

In the course of the ever-increasing demands of the environmental and climate protection pose to the transportation sector, lightweight construction is increasingly gaining in importance when it comes to developing future vehicles. The greatest lightweight potential is often found in composite construction where metal components are combined with fiber-reinforced plastic components. The thus resulting material mix is particularly demanding for joining methods. When joining conventional steel/steel connections in vehicle body construction, adhesive processes and component-penetrating supplementary elements, as for example screws and rivets, are primarily used or the fusibility of the components during welding is harnessed. Because of its high degree of automation and its achievable cycle times, resistance spot welding is still considered the preferred and most prominent joining technique in vehicle body construction. However, fiber reinforced plastics with a duroplastic matrix cannot be melted. Furthermore, a supplementary element which is subsequently introduced destroys the component’s fiber architecture, resulting in a reduction of the strength of the overall compound.A promising approach of making resistance spot welding compatible with FRP/metal components consists in intrinsically integrating weldable load-introducing elements into the fiber composite. In contrast to supplementary elements introduced subsequently, the so-called inserts may be integrated without damaging any fibers thereby allowing to exploit the full lightweight potential of the fiber structure.This project shall examine fundamental correlations between the manufacture of composite components, the accompanying fiber flow and the subsequent welding process in order to be able to install weldable inserts. A method shall be developed, using simulation models and the systematization of process and component design to facilitate the composition of the joining area under consideration of heat introduction during resistance spot welding.The planned investigations shall make a significant contribution to understanding the manufacturing process and the individual design of weldable FRP/metal compounds, in order to enable good mechanical properties of the joint as well as high reproducibility.

• DFG Programme: Research Grants