Metal-to-thermoplastic Adhesion Improvement in a Resistance Welded Composite Joint (abstract only)

Abstract

Thermoplastic composites can be resistance welded. This method requires the inclusion of a porous electrically conductive element between the two composites to be joined. By applying a current to it, it will heat by joule effect and melt the composites matrix. By maintaining pressure on the joint it will consolidate during cooling. These joints are very resistant to fatigue and shear. However it has been observed that the rupture of these joints is mainly between the conductive element made of stainless steel and the thermoplastic matrix with a composite of poly(phenylene sulfide) (PPS) reinforced with carbon fibers. In order to improve these welded joints, the silane is used as a coupling agent between the two materials. It is a bivalent molecule with a silanol part (-Si-OH) that can be grafted to the oxides of the steel and an amine part. Grafting silanes onto the steel increases its adhesion with organic materials. The application of silane layer on the steel has already made it possible to increase the apparent shear strength of welded joints by more than 30%. The optimization of the steel treatment and the modification of the PPS matrix could then significantly improve the mechanical performance of such joints.