Development of a new joining technology for hybrid joints of sheet metal and continuous fiber-reinforced thermoplastics

Abstract

Punctiform mechanical joining technologies, such as riveting, clinching, or screwing, which are widely used in sheet metal processing, are frequently applied because they have been established for many years. Depending on the process, they offer a variety of advantages such as one-sided accessibility, re-detachability, and no need for pre-punching operations or auxiliary joining elements. In addition, the processes often guarantee a high process reliability and extensive process monitoring. However, with thermoplastic composites, they lead to considerable stress concentrations at the joint due to the fibers. Undesirable fiber and inter-fiber breaks then result. With the development of the novel joining technology of joint stamp riveting, an improvement is achieved in this situation that has been described for hybrid joints on components made of thermoplastic composites and metal sheets. The joining principle is based on the formation of a form lock between the joining partners. The thermoplastic composite is thermomechanically formed by means of a joint stamp without using an auxiliary joining element. Within the scope of a research project, the joining process was characterized with regard to the structure of the joining spot, the geometry of the forming tools, and also the mechanical properties for purposes of analyzing and designing the joining process.