Ultra-High-Strength Cross-Tension Metal-Composite Joints via Wobble Angular-Laser-Structured, Injection-Molded Interlocking

In this paper, a novel laser structured injection molded cross-tension joint process is proposed using a pulsed laser, laser scanner, pitch stage, and injection molding. By applying angular and variable laser beam width, extra interlocking structures are generated compared to conventional laser-texturing based joining methods. The process includes laser machining a metal surface with microscale grooves and joining composite material by injection molding composite material on top of the metal. By utilizing injection molding, composite material can join during the forming process reducing cycle time. Relationship between laser machining parameters and joint strength is investigated using Design of Experiments where optimal laser machining parameters are found. Injection molding conditions are experimentally studied where mold temperature showed significant cross-tension joint strength enhancement. The microscopic laser machined grooves are analyzed using scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS) and cross-sectional image processing. The analysis indicated that by using the proposed method, grooves are fully filled with glass fiber and polymer material resulting in stronger joints. The proposed joining method can join metal and polymer with a simple and cost-effective process achieving ultra-high cross-tension strength. The greatest strength 13.8 MPa cross-tension joint strength is observed using the proposed method, which is stronger than previously reported laser based joining methods.