Forming and Joining of Carbon-Fiber-Reinforced Thermoplastics and Sheet Metal in One Step

The processing and component properties of metals have led to their worldwide success in mechanical engineering. Their advantages are high ductility, efficient production methods, good joining ability and nearly isotropic mechanical properties. Fiber-reinforced plastics (FRP) are known for an excellent lightweight design potential, due to low density as well as high and anisotropic tensile stiffness. By using thermoplastics instead of thermoset matrices, processing times and therefore component costs have already been reduced significantly and thus have become affordable in large-scale application. If the advantages of both, metal and FRP, are intelligently combined, a part with tailored properties is created. However, suitable forming processes, which take the different forming effects of both materials into account, have to be developed yet. The scope of this research was to enable the combined forming, joining and impregnation of pre-impregnated FRP-sheets and sheet metal to steel-CFRP-steel-sandwich-parts in one process step. As forming and joining must be executed at temperatures above the melting point of the thermoplastic while the part removal must take place beneath this temperature, a heating concept for drawing tools was developed to enable short production cycles. In order to ensure an economic industrial production a fast heating and cooling of the tool is essential. Afterwards optimal impregnation and joining process parameters for short cycle times were determined with planar samplings. The influence of the process parameters on part quality was investigated microscopically. Based on this research, a forming tool was constructed and hat profiles of steel-FRP-steel sandwiches were drawn successfully. Subsequently, the impregnation quality was investigated based on the process parameter tool temperature. Furthermore, the geometrical deviation of formed hat profiles was investigated. © 2017 The Authors