Experimental and simulative investigation of the effects of laser-structured metal surface on metal-polymer direct joining

Abstract

Direct joining of metal and polymer consists of surface treatment and injection molding techniques. This study employed a laser machining as the surface treatment to form periodic dimples on a joining surface. We experimentally investigated the effect of surface structures on joining strength under a constant molding condition; we focused on the diameter, aspect ratio and periodicity of the dimple, and the surface texture on its inner wall. Furthermore, we analyzed the effect of the surface texture on the inner wall of the dimple on the joining strength with finite element method. We found that the joining strength became higher with increasing number of dimples when total machined area was same. Another finding was that the joining strength increased with increasing aspect ratio and was saturated above the aspect ratio of 0.6. Furthermore, the experimental and simulated results strongly suggested that roughness on the inner wall of the dimple played an important role to enhance the joining strength. The findings of this study will promote the optimization of the metal surface structure for the metal-polymer direct joining.