THEORATICAL AND EXPERIMENTAL INVESTIGATION OF ULTRA HIGH-STRENGTH JOINING IN METAL COMPOSITES

For the automotive industry specifically, advanced joining methods present an opportunity to reduce vehicle weight without sacrificing structural performance, thereby achieving significant reductions in fuel consumption for internal combustion engines and enhancing energy efficiency in electric vehicles. However, the primary obstacle in adopting these joining methods at scale lies in the lack of strong, robust, and reliable techniques. Traditional joining processes, such as mechanical fastening and adhesive bonding, often fall short due to limitations in manufacturing cost, robustness and overall weight when applied to hybrid materials. In response to these challenges, innovative joining technologies such as thermomechanical joining have been developed, to meet the strength requirements of hybrid materials. However, the primary obstacle in adopting these joining methods in industry lies in the lack of strength in cross-tensional loading conditions. There is a need to discover the effect of laser structured joints on cross-tensional loading conditions. No previous study examined the impact of microstructure parameters on the mechanical behavior of injection molded joints in cross-tensional loading conditions.

In this research, a novel laser structured injection molded cross-tensional joint (LICJ) is proposed using a laser scanner, pitch stage, precision stage, and injection molding. By applying angular and variable laser beam width, LCIJ achieves extra interlocking structures compared to conventional laser-based methods. The proposed joining method can join metal and polymer with a simple, cost-effective process achieving ultra-high cross-tensional strength. The process is initiated by laser machining a metal surface with microscale grooves or patterns. Then the composite material is injection molded, or heat pressed on the metal plate. The microscopic laser machining conditions are analyzed and optimized for stronger joint strength. By using this approach, two dissimilar metals and composite materials can be joined without using any adhesives or bolts. Cross-tensional joint strength of 13.8 MPa is observed using LCIJ, which is stronger than conventional epoxy-based adhesives.