Method of Evaluating Shear Strengths in Contour Laser Transmission Welding 2007-01-0571

Laser transmission welding is a relatively new technique for joining thermoplastic components in the automotive industry. Laser energy is passed through a laser-transparent part and dissipated as heat in a laser-absorbent component. There is currently no standardized test to assess the strength of laser transmission welds made using thermoplastic materials. A properly-designed test allows the weld strength of the joint to be measured accurately and rapidly. This paper reports on a technique for measuring overlap shear strength. This study compares two weld orientations (weld line parallel and perpendicular to assembly loading) using polycarbonate, polypropylene, polyamide 6, polyamide 6 reinforced with 30% glass fibres and polyamide mXD6 reinforced with 50% glass fibres. Assemblies were made using a range of laser powers. In order to simulate industrial conditions, artificial gaps were also introduced between the transparent and absorbent parts.

Both weld orientations provided similar results when no gap was present between the transparent and absorbent parts. Weld orientations parallel to the direction of loading were observed to give more reliable results once a gap is placed between the parts. The importance of test specimen dimensions to prevent assembly failure in the bulk material during testing and the effect of other geometric parameters are also discussed.