Projects

Load-adapted multi-materials combining the material-specific advantages of metal and thermoplastics are becoming more and more important for applications in industry, above all in lightweight construction. For this purpose, it is necessary to find efficient process chains that use - aligned with the specific load - an optimized pre-processing and joining technology, as well as modified tools for process simulation and feature characterization.

Post- and in-mould assembly processes, mechanical joining methods, such as screwing and riveting, and adhesive bonding are techniques that actually  have been commercially available to reliably manufacture joints consisting of heterogeneous materials. Specific limitations of these technologies mainly arise from:

• Limitations in geometry complexity
• Local cross section thinning and impaired force flow in fiber reinforced polymers  (FRP)
• The necessity of using additional materials
•  Longer process times.

Consequently, new joining techniques that work quickly without the above mentioned limitations were sought.

Research on surface pre-processing and adhesive bonding technologies, as well as thermally induced joining methods, was done at the Fraunhofer IWS Dresden, based on their extensive materials knowledge and process expertise in laser- and plasma-based production technologies. The thermal direct joining technologies are characterized by short bonding times and the substitution of additional material (e.g. adhesive).

When joining mixed compounds consisting of metal and thermoplastic, the IWS makes use of load-adapted surface structuring, layers to improve adhesion and various heating strategies. Application-appropriate heating is generated by laser beam, heating elements or induction.

The required heat input is adapted to the specific materials combination and the joining part’s geometry as a function of the technology based on numerical simulations in order to provide a sufficient melting volume without damaging the base materials.