Influence of Climatic Changes on the Joint Strength of Laser Joined Plastic-Metal-Hybrids

Multi-material lightweight construction enables reducing dead weight while maintaining and preferably boosting the components' performance. The combination of different materials such as fiber-reinforced plastics (FRP) and metals require reliable joining techniques. A promising approach for joining is a two-staged laser-based joining process, which consists of micro structuring the metal surface, followed by thermal joining. In the first step, spongy microstructures with nano-substructures are generated on the metal surface. In the subsequent joining process polymer and metal are joined via thermal direct joining. Therefor both joining partners are clamped together, the metal surface is heated up with a diode laser and through heat conduction the thermoplastic polymer matrix melts and flows into the structures to harden there. For automotive and aeronautical applications, the faultless use of the connection must also be ensured at varying temperatures. However, plastics and metals have very different coefficients of thermal expansion. In this contribution the influence of climate changes on laser-based FRP-metal hybrid joints is investigated and evaluated. Therefor tensile shear samples, made of stainless steel and glass fiber-reinforced Polypropylene, are stored in a climate chamber for temperature cycles between -40[degrees]C up to 80[degrees]C. The joint strength is tested before and after climate change and the joining interface is analyzed with cross-sections. Keywords: lightweight, hybrid joining, laser joining, plastic-metal-joining, surface texturing, conelike protrusions, climatic changes