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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.

The effect of laser welding parameters such as laser power, laser speed, working distance and weld pressure on the weld strength, microstructure and meltdown of modified T-joints were studied using a diode laser and a contour welding technique. Specimens made of 30% glass reinforced nylon 6 were used in this study. A regression model was fitted to the data based on a central composite experimental design. The model showed that low levels of laser power at lower laser speed gave the maximum weld strength. It was observed that increases in weld pressure had a negative effect on weld strength. Meltdown was found to increase proportionally to the line energy and weld pressure.