Thermal distortion in surface pretreatment of metal-polymer hybrids using continuous wave laser radiation

摘要

Due to the increasing electrification in the automotive industry, materials with a high mass-specific strength are in greatdemand. In this context, direct thermal joining is an innovative approach to join metals with plastics in the sense oflightweight construction. In order to increase the joint strength, a laser-based surface pretreatment is expedient. Theprocessing with laser radiation generates an inhomogeneous temperature field in the metal, which causes thermaldistortion. The deformation can significantly influence the process stability of the subsequent joining process or evenprevent its successful execution. Therefore, the thermal distortion in pretreatment was analyzed in order to understandthe process behavior and to guarantee excellent joining conditions.For the pretreatment of metal surfaces, infrared continuous wave laser radiation was used. In order to understand theimpact of thermal distortion, the metal surface was structured varying the process parameters such as the laser power, thevelocity of the laser focal spot, or the applied area energy. Additionally, the structured area size was analyzed. Thedeformation was analyzed comparing the shape of the metal sheets before and after the processing. Based on theinvestigations, strategies to reduce distortion were derived and experimentally investigated. Upon the results, it waspossible to extract design recommendations for surface structuring using remote ablation cutting. One approach is anoscillating beam guidance which shows significant potential especially in the combination with a high processingvelocity.