Novel process for butt-joined plastic-metal hybrid compounds

Particularly in the automotive industry, there is a persistent problem arising from the need to reliably and permanently bond dissimilar materials such as plastics and metals. To solve this problem, experts at the Fraunhofer ILT in Aachen have come up with a solution that is suitable for industrial applications. Unlike adhesive bonding, the process works without additives or additional intervals for hardening or surface cleaning. Starting from the state-of-the-art process used today, the chain can be optimized for butt connections to a novel process using the thermal energy applied by the microstructuring process of the metal component. A new joining device is introduced, which allows the microstructuring of the metal component with an angle of incidence. After heating the component by the microstructuring process, it is pressed into the plastic component in the same joining device. The liquid plastic flows inside the inclined microstructures, which have a big undercut groove and a barb-like effect in the tensile shear load direction. After curing, the connection is based on a mechanical interlocking between the two components. At first suitable microstructuring parameters are evaluated to achieve a homogeneous melt flow of the plastic inside the cavities, which enables a high structure filling-rate and a good mechanical performance of the joint in tensile shear tests. Furthermore, the resulting temperature distribution is evaluated by thermocouples. Different influencing factors on the strength are evaluated like various penetration depths, different structure distances, or different clamping offsets of the plastic component.