WEB Influence of Continuous Wave Surface Structuring and Zinc Coating on Bond Strength of Hybrid Joints Made of Steel and TP-FRPCWednesday (29.04.2020) 10:00 - 10:20 Room 2
Hybrid structures combining fiber reinforced polymer composites with metals are becoming increasingly popular across all industries due to their lightweight construction potential. Especially thermoplastic fiber reinforced polymer composites (TP-FRPC) are of particular interest due to the short processing cycle times that can be realized e. g. by thermoforming and the accordingly high potential for mass production. For lightweight optimized hybrid structures, efficient joining is essential. Conventional joining processes, as screwing and riveting, show clear disadvantages such as the need for holes, which destroy the load-carrying fiber structure of the TP-FRPC, and weight increase. Adhesive bonding, a possible alternative, often requires long curing times and can be challenging for high-performance thermoplastics. In this context, Induction welding offers great potential, as it takes advantage of the meltability of the thermoplastics as well as of the good inductive heatability of metals, thereby allowing to bypass the disadvantages mentioned above. However, when it comes to bond strength, the full potential of welded joints is not yet fully exploited. In hybrid induction welding, the bond strength between the materials can be increased by surface pretreatment of the metals.
The aim of the presented study was to investigate the influence of different surface pretreatments of the metallic joining partner on the bond strength of welded hybrid joints with TP-FRPC. As surface pretreatments for the metal sheet (deep-drawn steel 1.0338 and 1.0330) different laser structures in line pattern were investigated. The varied parameters were the structure angles, the structuring distances an optional zinc-galvanization as well as laser-induced nonporous surfaces. As TP-FRPC continuous glass fiber reinforced polyamide 6 (GF/PA6, twill fabric, 600 g/m², 47% vol. fibers) and polypropylene (GF/PP, twill fabric, 600 g/m², 47% vol. fibers) was used. The bond strength was determined by tensile shear tests in accordance to DIN EN 1465 and the quality of the joint was evaluated using optical microscope images. It was found that the zinc-galvanization and the structuring distance of the laser structuring perpendicular to the load direction have a strong effect on the tensile shear strength of the hybrid structure.