Analysis of the composite properties of plastic/metal hybrid components through back-moulding of metallic three-dimensional Surfi-Sculpt form-fit elements, under consideration of the formation of micro weld lines (HySurf)

• Applicants: Professor Dr.-Ing. Christian Hopmann; Professor Dr.-Ing. Uwe Reisgen
• Subject Area: Joining and Separation Technology ; Plastics Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 555232518

Due to the combined usability of the material-specific properties plastic/metal hybrid components are used to reduce the weight of structural components and improve mechanical properties, for example in automotive and aerospace engineering. The joining of the dissimilar material groups can be achieved by joining processes such as welding, adhesive bonding or in an integrated back-moulding process known as in-mould assembly. A distinction is made between different joining mechanisms (friction, adhesively, form-fit). Form-fit connections provide advantages, because they are independent of the plastic material and the components can be separated after the usage duration. In many cases, micro-form-fitted elements are used, which focus on the removal of material to create undercuts. Conventional form-fit as well as material-fit joining mechanisms have in common that the connection is predominantly defined by a two-dimensional interface between the two materials. In contrast, the Surfi-Sculpt process offers the possibility of creating three-dimensional macroscopic structures on different types of metal surfaces, which are characterized by a dominant elevation and an accompanying indentation. This enables improved structure utilization for bonding between metal and plastic, but the protrusion of the metallic structure into the plastic component results in new flow and bonding effects compared to purely subtractive structures. Surfi-Sculpt structures can be produced using the laser welding process. The resulting geometry depends greatly on the process parameters and has a significant influence on the form closure created in the back-moulding process. Knowledge of these interactions enables a load case-specific adjustment of three-dimensional form-fit geometries, whereby the composite properties can be optimized. To determine the influence of the Surfi-Sculpt structural properties on the back-moulding process and the resulting composite properties, geometrically different Surfi Sculpt structures are introduced into the metal component and then bonded to the plastic component in the injection moulding process. The focus is both on the properties of the metallic Surfi-Sculpt structures produced (elevation, indentation, width, undercut, arrangement, metallurgical properties) and on the influences of the joining process (flow, filling and cooling behavior of the plastic melt, pressure and temperature conditions), which affect the overall component properties. The influence of the different structural geometries and positions on the resulting weld lines behind the individual structures will also be investigated in injection moulding simulations. The overall aim of the research project is to develop a methodology for predicting the bonding and failure behavior of back-moulded three-dimensionally bonded plastic/metal hybrid components using Surfi-Sculpt structures as a function of the process and material parameters.

• DFG Programme: Research Grants