RESISTANCE WELDING OF LOW-MELT POLYARYLETHERKETONE: PROCESS DEFINITION AND OPTIMIZATION

Within the European Clean Sky 2 Program thermoplastic composites are readied for future single aisle application and validated by the full-scale demonstration of the so-called Multifunctional Fuselage Demonstrator (MFFD). DLR together with Premium AEROTEC, AERNnova and AIRBUS will deliver the upper half shell for this 8 m long barrel made of carbon fiber-reinforced low-melt Polyaryletherketone (LM-PAEK). Resistance welding was chosen to join the C-frames with up to 19 attached flanges of variing length to the fuselage skin. For process definition, the welding parameters of LM-PAEK were investigated using a customized weld module. The main processing parameters affecting the quality of the weld, were defined as input parameters for a Design of Experiments (DoE). The DoE was conducted on the basis of a glass-insulated welding element. The bondline quality of each parameter set (design point) was assessed by water-coupled ultrasonic investigations, the fracture load values defined by single lap shear testing and microscopic fracture surface analyses. Thus, a numerical parameter optimization was performed in order to define the weld parameters for frame integration. Within a second evolution stage of the welding elements, replacing the glassfiber insulation of the welding elements to pure resin films, the potentials for a mechanical performance increase could be demonstrated