Structural components fabricated by use of fibre reinforced plastics (FRP) exhibit a high lightweight potential due to the high strength and low density. For serial applications like in automotive sector, thermoplastic matrices are highly demanded, because already existing forming technologies enable economical processing and short clock cycles. Many concept cars of OEMs show the strategy to substitute single metallic components or subassemblies by FRPs in areas with the highest lightweight- and cost potential. The advantage of this multi material design (MMD) is to use the locally optimized materials with the required properties and low costs.
A vital challenge of the MMD is the requirement of suitable technologies for joining different types of materials like metal and FRP with regard to the performance and large-scale production. Conventional joining techniques like rivets, FDS-screws or adhesives may harm the FRP component or require a high manufacturing effort and quality assurance. Furthermore, modifications of the installed state of the art spot welding production lines are necessary.
The aim of the project is to avoid such investments in new production lines by using spot welding as joining technology between FRP and metals. Therefore, the FRP need to be enabled for spot welding by application of so called welding patches. These welding patches consist of a metal component and a FRP component, which are combined and consolidated during the thermoforming process.
This lecture describes the processing, mechanical design and numerical simulation of components equipped with such welding patches of specimen on coupon level. In a first step, different geometries are developed, compared and evaluated to each other. For the surface engineering, long-term durability, coatings and surface treatments are considered. With special regard to the interfaces between the welding patch and FRP / metallic car body representative load cases are simulated. To estimate the failure behaviour, material related failure criterions are taken into account. The results of the simulation are validated on the basis of experimental data generated by simultaneous testing of specimens on coupon level.