Robert Kießling

On the development of an intrinsic hybrid composite

Hybrid parts, which combine low weight with high strength, are moving into the focus of the automotive industry, due to their high potential for usage in the field of crash-relevant structures. In this contribution, the development of an intrinsic hybrid composite is presented, with a focus on the manufacturing process, complex simulations of the material behaviour and material testing. The hybrid composite is made up of a continuous fibre- reinforced plastic (FRP), in which a metallic insert is integrated. The mechanical behaviour of the individual components is characterised. For material modelling, an approach is pointed out that enables modelling at large strains by directly connected rheological elements. The connection between the FRP and the metallic insert is realised by a combination of form fit and adhesive bonds. On the one hand, adhesive bonds are generated within a sol gel process. On the other hand, local form elements of the metallic insert are pressed into the FRP. We show how these form elements are generated during the macroscopic forming process. In addition, the applied sol gel process is explained. Finally, we consider design concepts for a specimen type for high strain testing of the resulting interfaces.

On the Design, Characterization and Simulation of Hybrid Metal-Composite Interfaces

Multi-material lightweight designs are a key feature for the development of innovative and resource-efficient products. In the development of a hybrid composite, the interface between the joined components has to be considered in detail as it represents a typical location of the initialization of failure. This contribution gives an overview of the simulative engineering of metal-composite interfaces. To this end, several design aspects on the microscale and macroscale are explained and methods to model the mechanical behavior of the interface within finite element simulations. This comprises the utilization of cohesive elements with a continuum description of the interface. Likewise, traction-separation based cohesive elements, i.e. a zero-thickness idealization of the interface, are outlined and applied to a demonstration example. Within these finite element simulations, the constitutive behavior of the connected components has to be described by suitable material models. Therefore, inelastic material models at large strains are formulated based on rheological models.

Production and modelling of an intrinsic hybrid metal composite for automotive parts

Hybrid parts, which combine low weight with high strength, are moving in the focus of the automotive industry. This contribution deals with the development of an intrinsic hybrid composite made up of a continuous fibre-reinforced plastic, in which a metallic insert is integrated. The connection between these components is realised by a combination of adhesive bonding and a geometrical form fit. To this end, a metallic insert with form fit elements is developed. The form fit elements are generated by out-of-plane deformations induced by a global in-plane load. This in-plane load is applied within the global forming process. Consequently, the intrinsic hybrid composite is produced in an one-step process, which is presented as well. The mechanical properties of the resulting composite are analysed with the help of a finite element simulation of a representative volume element. In this context, inelastic material models at large strains, which are formulated based on directly connected rheological elements, are applied to take account of the mechanical behaviour of the individual components.

A process and load adjusted coating system for metallic inserts in hybrid composites

According to the concept of an intrinsic hybrid composite, adhesive bonding is designed for generating the connection between the applied fiber reinforced polymer and a metallic insert. To induce adhesive bonding, a metallic insert, made of aluminum, is coated. This contribution focusses on the development of a suitable coating system. To this end, the coating system must meet certain requirements. On one hand, demands on the coating like ductility can be deduced from analyzing the manufacturing process. On the other hand, requirements like corrosion protection as well as high static and dynamic strength arise from specific applications under considerations. The utilized coating system is based on organically modified silicate layers (Ormosil) applied using a sol–gel process. To prove that this coating system fulfils the requirements, the corrosion protection is analysed by impedance spectroscopy. Furthermore, different mechanical experimental investigations are performed to verify the ductility of the coating as well as the strength of the resulting interface. Hence, it is shown that the considered coating system can be applied for the analysed intrinsic hybrid composite manufactured in series.