Understanding Resilience to Contamination in the Joint Interface for a Resistive Welded Joint in Fiber Reinforced Thermoplastics 2019-01-1273

The continuous evolution to improve both the efficiency and lower the emissions of passenger vehicles now means that the need for light weighting is indisputable. New material systems such as fiber reinforced thermoplastic composites offer just such a very high lightweighting potential.

Although most of these parts are currently joined using adhesives, resistive welding provides a promising alternative. Indeed, the faster cycle times, recyclability, design flexibility and resilience to contamination indicate the superiority of resistive welding over adhesive bonding. Although resilience to contamination is widely accepted, it is yet to be validated as very little scientific data is available concerning these characteristics. To ensure the scalability of these joints in automotive applications, they should exhibit tolerances to specific contaminations that are present in the body shop. While it is possible to minimize contaminations in the body shop, it often comes with requiring additional cleaning steps and maintaining large, clean rooms which are very expensive.

In this paper, the effect of contaminations, particularly water and oil residues on joint strength were studied to determine their effect upon both resistive welded and adhesive bonded joints. Defined quantities of these contaminants were introduced at the joint interface, and the effect on lap shear strength was measured. While the greater sensitivity of adhesives to contamination is known, quantifying the resilience of resistive welded joint remains undone. Such information data is critical in the design of the joint geometries and manufacturing lines for fiber-reinforced thermoplastic parts. A less stringent set of requirements for minimizing contamination will also increase flexibility and decrease the capital cost of manufacturing plants.