Resistance welding of thermoplastics & Joining of hybrid structures

Abstract

Adhesive bonding or metal fastening are state-of-the-art joining technologies for the design of continuous fibre reinforced composites (CFRP) structures. On the other hand, adhesive bonding is difficult to process and to monitor, metal fasteners introduce local weakening spots, local delaminations may occur and an optimized load transfer into the laminate is not reachable. Compared to thermoset matrix systems, the molecular constitutions of thermoplas¬tics enable these materials to offer an additional joining method: thermal joining or welding. This is one of the best suitable joining technologies for CFRP, as no fibres are damaged and the matrix systems are linked by first and second order molecular interactions. The experiences gained with the resistance welding, with the focus on using carbon fibre reinforced PolyEtherEtherKetone (CF-PEEK), within the last years will be shown. Another main objective is the realization of hybrid structures, which means the combination of thermoset materials with thermoplastics. Target of the examinations at DLR, Institute of Structures and Design, is the combination of thermoplastic and thermoset parts, using standard manufacturing techniques to generate hybrid components for primary aircraft structures.