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Lightweight materials, such as aluminum die castings, are used more and more for automotive applications. Due to the limited weldability, joining these materials by self-pierce riveting has been established. The challenge in this regard is that these materials, especially new high strength aluminum die castings, have a limited ductility, while the joining processes locally induce large plastic deformations. Consequently, joining by forming of these materials can be accompanied by cracks, which develop during the forming operation. This paper shows the experimental and numerical investigation of a new die concept for self-pierce riveting materials with limited ductility. At the new tool concept the riveting die is separated and a movable die element is used. This element allows that the parts are superimposed with compressive stresses during the self-pierce riveting process. In the paper it can be shown, that in contrast to the conventional process crack-free joints can be generated by using the new tool concept. Determination of the joining parameters and the die design was supported by simulative investigations. Additionally, the new and the conventional self-pierce riveting process are compared on the basis of results from the experimental investigations.

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Sandwich structures consist of one light core layer and two top layers, which form the load-bearing structure. These layers have to be stiff and strong and have to protect the structure against indentations. The main task of the core layer is to keep the top layers in place and to generate a high shear stiffness. In order to obtain the required space between the top layers, the core layer has to have a high specific volume. Different sandwich materials with aluminium or steel top layers and cores of aluminium combs, corrugated aluminium sheets or aluminium foams are already known. In order to obtain better properties in terms of strength fibre-reinforced plastics (FRP) are utilised as top layers; this is the focus of numerous of the current research studies. The sole use of these materials leads to negative effects regarding the damage and impact behaviour. New top layers with high strength and high stiffness characteristics as well as good damage tolerances are to be expected by utilising metal layers in combination with endless fibre-reinforced plastics, so called hybrid laminates. These hybrid laminates combine the positive properties of metals (e.g. ductility) and fibre-reinforced plastics (e.g. tensile strength). The focus of this investigation lies on the production and characterisation of sandwich structures with aluminium foam core layers and hybrid laminate top layers. The foam cores consist of closed pore aluminium foams produced by utilising ingot and powder metallurgical techniques. The top layers consist of glass fibre-reinforced thermoplastics and aluminium layers. The production of the sandwich materials is realised by means of thermal pressing.