Simulation-aided development and qualification of a novel Thermoclinch joining technology for multi-material design with textile-reinforced thermoplastic composites

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Aim of the proposed project is the simulation-aided development of a novel forming-based joining technology for metal-plastic hybrid structures with thermoplastic composites. Within the devised joining method thermoclinching, the locally heated and plasticised composite is moulded through an opening in the metallic part and spread to an undercut with defined fibre architecture. With the aim of raising process capabilities and reducing cycle times, the thermoclinching technology is further developed by integrating the pre-processed steps of cutting and heating into the actual joining process.Therefore, adapted joining devices, forming tools and process parameters are developed for the advanced thermo-mechanical process, which is characterised by large plastic deformations of the textile reinforced thermoplastic.The fundamental theoretical, technological and experimental investigations are performed on the example of the material configuration glass-fibre reinforcedpolypropylene (GF/PP) and steel sheet metal. Based on this, alternative material combinations with brittle carbon fibre reinforcement and low-viscous matrix systems like polyamide are evaluated for the inline-thermoclinching process.The realistic prediction of the deformation and failure behavior in thermoclinching joints is based on a numerical multiscale process simulation strategy with coupled process and structural models. The simulation tool is extended to integrate default laminate structures and material combinations for the structural analysis of the joints and the numerical prediction of joint properties.For the detailed analysis of the thermoclinching joints, selected joint configurations will be manufactured and evaluated on the macroscopic level by characterising the joint shape and on the microscopic level by evaluating the deformation-induced local fibre alignments. For the extensive structure determination of the joints, the computed tomography is applied and additionally used to validate process simulations, especially with respect to the resulting joint characteristic. Furthermore, in-situ-computed tomography is used for an in-depth understanding of the successively damage behavior under tension-shear and peel loading.The numerical and experimental evaluations of the anticipated complex interaction between process-specific influences and joint properties are performed using standardized test methods for single-lap joints (tension-shear and peel load). On that basis, quality assurance methods are derived for producing hybrid joints with reproducible joint properties. Based on a comprehensive assessment of the novel connection method, material specific design rules for a load adapted design of structural joints are deduced. In addition, constructive design guidelines for inline-thermoclinch-installations are worked out.