Hysteresis heating based induction bonding of thermoplastic composites

The bonding of polymer matrix composites using magnetic particulate susceptor materials for hysteresis induction heating is investigated in this study. Hysteresis heating is tailored through careful design of the microstructure of magnetic particulate polymer films. The bond strength of hysteresis-welded materials is comparable to that of autoclave-welded materials while offering an order of magnitude reduction in cycle time. The relative contribution of the intimate contact and healing mechanisms to fusion bonding process indicates that it is intimate contact controlled. The macroscopic failure modes of hysteresis bonded specimens include adhesive composite/film, cohesive film and cohesive composite. Inspection of the microscopic failure at the nickel particle/polymer interface in the film indicates quasi-brittle failure mode. The XPS peaks confirm nickel oxide in the form of NiO on the failure surface indicating adhesive failure at the particle/polymer interface. The area fraction of adhesive failure is found to increase with decreasing particle size and increasing particle volume fraction.