Integrating metals and plastics is essential for lightweight structures and efficient assembly in industries such as automotive and IT device manufacturing. This study investigated how laser micro-patterning enhances the interfacial bonding strength between these dissimilar materials in metal insert injection molding. Galvanized high-strength steel and polyphenylene sulfide (PPS) reinforced with 40% glass fiber were used as the metal and plastic materials, respectively. Four micro-patterns—circular, square, diamond, and hexagonal—were machined by laser on the bonding area at the end of the steel sheet. The effect of pattern spacing on bonding strength was evaluated by tensile shear tests on injection-molded specimens. The combined effect of laser processing and plasma surface treatment was also examined. For the square pattern, wider pattern spacing increased the bonding strength 2.2-fold, and for the hexagonal pattern the increase was 1.4- fold. Combining laser micro-patterning with plasma treatment enhanced the bonding strength by factors of 1.4 to 2.3. The effect of plasma treatment was greater for the square and diamond patterns than for the circular geometry.

In this study, a new method of bonding CFRP and Al6061-T6 with epoxy adhesive after shot-peening treatment on the surface of Al6061-T6 specimens was proposed to improve bonding strength of a single lap joint between CFRP and Al6061-T6. More specifically, correlation between shot peening coverage on the Al6061-T6 surface and bonding strength with CFRP was experimentally analyzed. Experimental results showed that the surface roughness and the bonding strength increased as the peening time on the surface of Al6061-T6 increased up to a specific peening time (or coverage). However, the surface roughness and bonding strength decreased again under an over-peening condition of 480 seconds (300% coverage) or more. Therefore, it is necessary to search for the optimal peening time that can maximize bonding strength as well as the fatigue life of parts at a peening time between 320 (200%) and 480 s (300%) through additional experiments in future studies.