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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.

Discontinuously reinforced thermoplastic composites are used in a wide variety of automotive applications due to their excellent mechanical properties and low processing cost. The mechanical properties of these short/long fiber reinforced materials can be improved by using continuous fibers. However, processing these continuously reinforced composites is more difficult due to the inextensible nature of the fibers. It is possible to combine the ease of processing of discontinuously reinforced thermoplastics with the superior mechanical properties of continuously reinforced materials by creating a hybrid part. The two different materials can be married using a number of technologies such as overmoulding and joining. In this research, vibration welding is used to join polypropylene reinforced with continuous glass fibers to other polypropylene compounds. Lap and T-style joints have been made using an instrumented linear vibration welder.