Thermal direct joining of metal to fiber reinforced thermoplastic components

In the field of lightweight construction, load-capable mixing compounds with the material specific advantages of metal and thermoplastics become increasingly significant. For this efficient process, chains including adapted pretreatment and joining processes in combination with process simulation tools are required. Post- or in-mold assembly processes, mechanical joining by screws or rivets, and adhesive bonding are state-of-the-art techniques for joining dissimilar materials such as metal and thermoplastics [R. Hoffschlag, Forschungsbedarf zum Fügen von Kunststoffen im Leichtbau und im Bereich erneuerbarer Energien (DVS-Berichte Band, Düsseldorf, 2012), p. 294; M. Gude, G. Meschut, M. Zäh, H. Lieberwirth, FOREL-Studie: Chancen und Herausforderungen im ressourceneffizienten Leichtbau für die Elektromobilität (2015)]. Specific restrictions can be found with the limited geometry flexibility, the use of an additional material and comparable long joining times. Hence, new joining solutions are needed. In this presentation, the use of thermal induced joining for metal and thermoplastic parts will be shown. These processes are characterized by short joining times and the substitution of glue, screws, or rivets. The key technology to enable high joint strengths is the material adapted surface modification. As a research result, the influence of physical and chemical pretreatment will be presented. It could be shown that metal ablation by high power lasers can efficiently generate a macroscopic surface structure, which enables mechanical fastening of the polymer at the metal surface. Depending on the materials to be joined, different kinds of heat inputs can be used. In this presentation, the joining by hotplates and by lasers will be introduced. It will be shown that an optimized surface pretreatment enables joints with a lap shear strength of 20 N/mm2 and more, depending on the material configuration.