Metal-composite hybrid joint adhesion and testing optimization for electric vehicle applications

Lightweight is a critical feature in automotive applications, especially in electric vehicle applications due to the heavyweight of batteries, thus contributing to improve vehicle efficiency. Multi-material solutions were studied in this paper as a strategy for lightweighting, focusing on the improvement of metal-composite joints obtained by overmolding through the comparison of different laser treated textures and processing parameters. In addition, testing methods to assess the adhesion of these joints were analysed. Firstly, steel surface treatment was carried out by pulsed laser radiation producing different patterns. Secondly, over injection of the composite material based on polyamide 6.6 with 40% recycled carbon fiber was carried out with different processing parameters. The mechanical performance of the joints was assessed through shear-strength analysis, and the morphological analysis was carried out. As outcome, the optimal combination of surface treatment and processing parameters was selected. Finally, a finite element analysis was carried out to evaluate comparatively the suitability of a testing method proposed as an alternative to the standard single lap shear tests, with a configuration that facilitates the specimens manufacturing and test execution. As a result, the adequacy of the method for the assessment of the shear strength of this type of joints was demonstrated.