Effects of Laser Surface Texturing and Injection Molding Parameters on the Direct Joining of AHSS and PA 6

With a growing interest for reducing vehicle weight to improve fuel efficiency, the automotive industry has focused on joining dissimilar materials including high-strength steel and fiber-reinforced plastics. However, differences in physical properties between metals and polymers weaken bonding strength. Laser surface texturing (LST) has emerged as a promising alternative of traditional joining methods of metal and plastic, such as mechanical fastening, adhesive bonding, ultrasonic welding, and friction stir welding. LST uses a pulsed laser to create surface patterns with microgrooves, which modifies surface properties such as roughness and morphology. In this study, LST was applied to join metal and plastic. Nanosecond pulsed laser is used to create microgrooves on advanced high-strength steel (AHSS), followed by injection molding of glass fiber-reinforced polyamide 6 (PA 6). Tensile-shear tests were conducted to examine the AHSS-PA 6 joint strength, and the effects of laser and injection molding parameters on the joint strength are investigated. The fracture mechanism of the AHSS-PA 6 joint reveals that mechanical interlock between AHSS and PA 6 at the grooves and recasts increases the joint strength.