Manufacturing and Analysis of Loop Connections for Thermoplastic Composites

Short cycle times and a high level of automation are outstanding features of manufacturing processes with thermoplastic composites. Additionally, the repeatable formability and weldability of thermoplastics enables adapted joining techniques like warm-shaped loop connections. This paper covers studies on the manufacturing of loop connections, performed during stamp forming of the composite structure. Simple loop joints with flat welding zones are analysed both, experimentally and numerically. Based on that, improvement strategies to optimise the loading behaviour are discussed and loop connections with profiled welding zones are designed to improve the peel resistance. For validation of the design concept, numerical analyses are conducted using an enhanced material definition including failure mode dependent stiffness degradation. Additional processing studies and mechanical tests are used to evaluate the adapted joint design, demonstrating the improved load bearing behaviour.