Thomas Bayerl

• Thermoplastic polymer-polymer composites consist of a polymeric matrix and a polymeric reinforcement. The combination of these materials offers outstanding mechanical properties at lower weight than standard fiber reinforced materials. Furthermore, when both polymeric components originate from the same family or, ideally, from the same polymer, their sustainability degree is higher than standard fiber reinforced composites. A challenge of polymer-polymer composites is the subsequent processing of their semi-finished materials by heating techniques. Since the fibers are made of meltable thermoplastic, the reinforcing fiber structure might be lost during the heating process. Hence, the mechanical properties of an overheated polymer-polymer composite would decline, and finally, they would be even lower than the neat matrix. A decrease of process temperature to manage the heating challenge is not reasonable since the cycle time would be increased at the same time. Therefore, this work pursues the adaption of a fast and selective heating method on the use with polymer-polymer composites. Inductively activatable particles, so-called susceptors, were distributed in the matrix to evoke a local heating in the matrix when being exposed to an alternating magnetic field. In this way, the energy input to the fibers is limited. The experimental series revealed the induction particle heating effect to be mainly related to susceptor material, susceptor fraction, susceptor distribution as well as magnetic field strength, coupling distance, and heating time. A proper heating was achieved with ferromagnetic particles at a filler content of only 5 wt-% in HDPE as well as with its respective polymer fiber reinforced composites. The study included the analysis of susceptor impact on mechanical and thermal matrix properties as well as a degradation evaluation. The susceptors were identified to have only a marginal impact on matrix properties. Furthermore, a semi-empiric simulation of the particle induction heating was applied, which served for the investigation of intrinsic melting processes. The achieved results, the experimental as well as the analytic study, were successfully adapted to a thermoforming process with a polymer-polymer material, which had been preheated by means of particle induction.