Achievement of high-strength Al/CFRP hybrid joint via high-speed friction stir lap joining and laser texturing pretreatment parameters variation

This paper presents the achievement of a high-strength Al/CFRP hybrid joint through a high-speed friction stir lap joining process, combined with variations in laser surface texturing pretreatment parameters. The study examined the impact of laser surface texturing parameters by varying the depth, interval distance and width of the laser texture. By adjusting laser texturing parameters, the softened PA66 was fully infused into the textured grooves on the aluminum surface, leading to a significant reduction in interfacial voids and cracks in Al/CFRP. The preliminary tensile shear test showed that the hybrid joint broke at the CFRP base material, indicating that the laser texturing exhibited excellent Al/CFRP interface strengthening ability. Further compression shear tests were applied to reveal the actual interfacial load-carrying performance for comparison. The maximum shear strength of 25.5_−1.34^+0.7 MPa was achieved at a joining speed of 3000 mm/min. Additionally, a mathematical model was proposed to assess the strengthening impact of laser texturing parameters, considering micro-texture geometry and interfacial defects. The tearing of PA66, detachment of carbon fibers, and the breakage of carbon fibers were the three primary types of fracture modes identified at the Al/CFRP interface. The joining mechanism revealed that both mechanical interlocking and the chemical bonding of Al-O-C contributed to the increase in joint shear strength. This study presents a credible method for producing high-strength Al/CFRP lightweight structures.