Mechanical joining without auxiliary element by cold formed pins for multi-material-systems

Abstract

In order to achieve sustainable and resource-saving products, the use of intelligent lightweight design is a current trend. One approach is the implementation of multi-material systems. However, the joining technology poses a key challenge when combining different materials like continuous fibre-reinforced thermoplastic composites (CFRTP) and metal or joining steel and aluminium. Due to different material properties and partial chemical incompatibilities, established joining techniques without auxiliary element, like welding or clinching, are reaching their limits. Joining dissimilar materials through pin structures has proven as a possible strategy to produce hybrid multi-material systems on a laboratory scale. Nevertheless, this technology is hardly used in mass production due to the currently complex, uneconomical pin manufacturing process. In this work, cold forming is presented as a promising approach for the production of such pins. In a first step, the pins are extruded from a steel sheet (DC04). In a second step, the steel sheets are joined with aluminium (EN AW-6016) or CFRTP by either pressing pins directly into the material or by caulking pins with a pre-punched joining partner. The material for the pin is extruded directly from the sheet metal thus preventing additional weight in contrast to fasteners. In addition, the direct press-fit is a suitable method to achieve a tightly sealed joint. Within this work, the extrusion of the pin, as well as the two different joining operations, are investigated showing the fundamental applicability and the potential of the new joining process. In order to analyse the applicability of the joining operation shear tensile tests are conducted.