Improved Lap Shear Strength of Ti6Al4V/CF‐PPS Joints Through Electrical Discharge Machining Surface Texturing

This study investigates friction‐assisted spot joining (FASJ) of Ti6Al4V alloy and carbon fiber–reinforced polyphenylene sulfide (CF‐PPS) composites using electrical discharge machining (EDM) surface pretreatment combined with process parameter optimization. EDM texturing generated superficial roughness that promoted mechanical interlocking between the molten polymer and the titanium surface. A central composite design was applied to evaluate the effects of rotational speed (RS) and plunge depth (PD), identifying optimal conditions that maximized lap shear strength while minimizing polymer degradation. Results showed that intermediate RSs favored bond formation by maintaining temperatures within the PPS melting range and preventing excessive thermal damage. Posttest characterization confirmed the formation of a bonded annular region that governed joint performance. The optimized process achieved lap shear strength values comparable to and, in some cases, exceeding those reported for other metal–composite joining techniques. Specifically, the EDM texturing process reached 33.1 MPa, outperforming most laser‐welded Ti/CF‐PEEK joints (2–37.3 MPa) and approaching the strength levels typically observed in aluminum–polymer benchmarks (≈55 MPa). These results demonstrate the effectiveness of the EDM‐induced surface features in enhancing mechanical interlocking and interfacial adhesion. These findings demonstrate that combining EDM pretreatment with controlled thermal input enhances the reliability of FASJ for lightweight structural applications.