Precise laser structures as a tool to understand metal-polymer joints

Direct joining of metals and polymers is a promising approach for today's challenges in joining technology due to fast cycling time, its robustness, and the absence of duroplastic adhesives. Laser pretreatment of the metallic surface has been proven to enhance joint strength and has become a popular method for joining hybrid components. However, the versatility of the laser process allows the generation of endless variations in structure geometry. Such structures possess various geometric characteristics like depth, width, density, and orientation, which all influence joint strength. Precise laser structuring of aluminum by nanosecond-pulsed laser radiation was utilized to gain a deep understanding of the correlation between structure geometry characteristics and joint strength. After laser pretreating the metallic surface, the parts were subsequently joined with a thermoplastic polymer by injection molding. The authors were able to distinguish between the effect of surface enlargement and structure geometry effects, as well as directionality and arrangement of the structures on the specimen. Although the authors did not focus on producing joints with high shear strength, some specimens exceeded 12 MPa during lap shear testing. The results are a step further toward advanced joint design for thermal direct joining and its application.