Advances in fusion bonding techniques for joining thermoplastic matrix composites: a review

Joining composite materials is an issue because traditional joining technologies are not directly transferable to composite structures. Fusion bonding and the use of thermoplastic ®lms as hot melt adhesives offer an alternative to mechanical fastening and thermosetting adhesive bonding. Fusion bonding technology which originated from the thermoplastic polymer industry has gain a new interest with the introduction of thermoplastic matrix composites (TPC)which are currently regarded as candidates for primary structures. The improvement of thermoplastic polymer matrices, with the introduction of recent chemistries such as PEEK, PEI and PEKEKK. exhibiting increased mechanical performance, service temperature and solvent resistance (for the semi-crystalline systems)also supported the growth of interest for fusion bonding. This review looks at the state of the art of fusion bonding technology and focuses particularly on the three most promising fusion bonding techniques: ultrasonic welding, induction welding and resistance welding. Physical mechanisms involved in the fusion bonding process for modelling purposes are discussed including heat transfer, consolidation and crystallinity aspects. Finally, the application of fusion bonding to joining dissimilar materials, namely thermosetting composites (TSC)/TPC and metal/TPC joints, is reviewed.