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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.

An exploratory study was performed to determine the feasibility of using oriented polypropylene rods as a replacement for metal in side impact beam applications. The study was divided into four phases: (i) laboratory testing of the impact and tensile properties of oriented polypropylene coupons, (ii) design of an oriented polypropylene side impact beam of comparable rigidity to that of a metal beam but with significant weight savings, (iii) development of a means of attaching the polymeric bar to the vehicle and (iv) flexural testing of a scaled down prototype. The oriented polymeric and metal beams exhibited comparable stress-strain behavior during scaled down testing. Although more research is required to validate the design of an oriented polymer side impact beam, the encouraging results suggest that oriented polymers should be considered for use in automotive components that can make use of their high specific strength and stiffness.

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.

In Laser Transmission Welding (LTW), a laser beam passes through a transparent part and is dissipated as heat in an absorbent material through the use of laser-absorbing pigments such as carbon black (CB). This energy is then conducted further into both parts. Melting and subsequent solidification occur at the interface causing a weld to form between the two parts. Gluing or welding structures to the back of automotive Class-A panels often results in the appearance of undesirable surface deformations on the Class-A side. Through control of the laser welding and material parameters, it may be possible to use contour LTW as a means of joining structures to the back of absorbent Class-A panels without creating these unwanted surface defects. A series of lap welds was made using a range of CB levels and laser powers. A profilometer was used to measure the size and shape of the defects generated on the surface of the black part. Two types of defects were observed: ribs and sink marks.