THERMOCLINCHING - A NOVEL JOINING PROCESS FOR LIGHTWEIGHT STRUCTURES IN MULTI-MATERIAL DESIGN

In the scope of reduced resource consumption and CO2 emissions, lightweight structures in multi-material-design offer a high potential for use in aviation or automotive applications. Though, to take advantage of the specific structural and functional properties of the different materials of hybrid structures, it is necessary to provide adapted manufacturing and joining technologies. This article presents the development of a new thermoclinching joining process to produce hybrid structures with continuous fiber reinforced thermoplastic composites and metallic components. Based on the principles of staking and the classical clinching process, thermoclinching technology ensures element free and form-closed joints by plastic deformation of the reinforced thermoplastic component. To approve the technological concept of the thermoclinching process, prototypic joints with both reinforced and non-reinforced thermoplastics were produced and experimentally tested, revealing up to 50% higher failure loads of the reinforced joints. In order to understand the generated fiber reorientation during the thermoclinching process and its optimization, the produced joints were analyzed using non-destructive and destructive testing methods such as computed tomography scans and micrograph analysis. It was shown that parts of the textile reinforcement were purposefully relocated into the neck and head area of the joint and thus considerably contribute to the load carrying capacity of the joint. Process simulations are performed to predict the plastic deformation and the resulting fiber orientation during the joining process. Even now, it can be stated that without the necessity to apply any additional joining elements, the developed thermoclinching technology projects a high lightweight potential for future composite structures.