Induction Heating of UD C/PAEK: What Thermography Can Teach Us about Eddy Currents

Induction welding is an attractive technology for fusion bonding of carbon fibre reinforced thermoplastic composites. In this process, eddy currents are induced in the conductive carbon fibre network by an alternating electromagnetic field, heating up the parts. In unidirectional ply-based composites, formation of eddy currents relies on the ply interfaces where changes in the fibre orientation facilitate closed-loop conductive paths. Improved control of the welding process therefore requires a deeper understanding of how the fibrous architecture relates to the physical mechanisms governing heat generation, which is the focus of this work. It comprises induction heating experiments on thin laminates and a series of tests performed on ply-scale specimens subjected to a strong electric current. Resultant heating has been monitored using an infrared camera. Combined, the recorded thermograms highlight that eddy currents are dominantly induced along the different fibre directions present in the lay-up and that the varying quality of fibre contacts at the ply interfaces affects the homogeneity of the current density within the plies