Effects of oxide layer on adhesion and durability of titanium and transparent polyamide joint by laser joining

A joint of titanium and transparent polyamide with desirable strength was achieved by laser joining. A maximum load capacity of 3400 N was obtained from a lap joining area of 25 × 25 mm2 at a laser power of 350 W and a travel speed of 4 mm/s. The effects of surface oxide layers with different thicknesses and stability were investigated. A joint with a thick oxide layer exhibited lower load capacity due to excessive thermal degradation of polyamide caused by heat buildup inside the thick thermal insulating oxide layer. With UV exposure, more pronounced reduction in joint strength was observed in the joint with the thick oxide layer. Cracking of the oxide layers was responsible for lower strength and expected to be a result of stress from polyamide contraction combining with internal stress of the oxide layer.