Joint strength optimization and morphological analysis for friction stir spot welding of the dissimilar thermoplastics ABS and PC

Abstract

Abstract The present study aims to investigate the feasibility of friction stir spot welding two dissimilar polymers, acrylonitrile butadiene styrene and polycarbonate. Welding parameters are effective on lap joint shear load. This study also investigated the influences of welding parameters such as rotational speed, plunge depth, and dwell time on the joint morphology and mechanical characterization. In addition, a common problem in friction stir spot welding is the forming of characteristic keyholes in the joint,s a problem that has an important effect on mechanical test results. For this reason, a polycarbonate filler sheet was used to improve the lap joint shear load by reducing the size of the keyhole in this study. The quality of the welded specimens was examined after lap joint shear tests. Experiments were carried out according to Taguchi L9 orthogonal array using a randomized approach for arranging optimum welding parameters. Signal-to-noise ratio and the analysis of variance were used to determine the influences of each process parameter on the lap joint shear load. Results indicated that the friction stir spot welding of acrylonitrile butadiene styrene with polycarbonate is feasible and welding parameters significantly affected joint quality. From the experiments, a 57 % improvement was achieved in the lap joint shear load from the initial welding parameters to the optimal welding parameters. Furthermore, weld morphology was investigated by morphological analysis and visual comparisons. Finally, the failure modes of the fractured samples were observed and classified for highest, moderate, and lowest lap joint shear loads.