The project set out to create a reliable, lightweight hybrid joining technology that combines metal and thermoplastic components for automotive use. The core scientific effort focused on developing a macro‑scale model of the joint (AP 4.4) that captures the key mechanical and thermal interactions while remaining computationally efficient. Validation of this model relied on laboratory specimens produced by Gubesch, whose material characterisation data were used to calibrate the viscoplastic behaviour of the chosen polypropylene‑glass‑fiber composite (PP GF30). The composite contains 30 % glass fibre, which is expected to raise the tensile strength relative to unreinforced polypropylene, but the material also shows pronounced strain‑rate sensitivity and a strong temperature dependence. At low temperatures (–30 °C) the glass‑transition temperature is exceeded, leading to a sharp drop in ductility and a tendency toward brittle, split‑like failure. At high temperatures (+80 °C) the modulus falls markedly, requiring additional reinforcement in stiffness‑critical designs. These material insights guided the sensitivity analysis of load cases ranging from quasi‑static functional loads to high‑rate crash scenarios, and informed the design of the joint geometry.

Building on the validated macro‑model, the team produced a process demonstrator in collaboration with Faurecia (AP 5.1 and AP 5.2). The demonstrator was first fabricated in a coarse‑scale form and later refined to a detailed prototype. Because the material data were not fully validated at the time of the first build, the simulation results carried an inherent uncertainty, which was acknowledged in the design review. Subsequent testing of the demonstrator by Faurecia provided empirical data that were compared against the simulation predictions. The test results confirmed the general trends predicted by the model, such as the load‑transfer efficiency and the distribution of stresses across the metal‑plastic interface, but also highlighted the need for tighter control of the adhesive cure cycle to minimise residual stresses.

Parallel to the physical development, a potential analysis was carried out that combined a life‑cycle assessment (LCA) and life‑cycle cost (LCC) study performed by MSE with the physical and virtual validation data from Faurecia and EDAG. This analysis quantified the environmental and economic trade‑offs of the hybrid joining approach, showing that the use of PP GF30 can reduce overall vehicle weight by up to 10 % compared with all‑metal construction, while the additional processing steps for the adhesive layer add a modest cost increase that is offset by the weight savings.

The final phase of the project (AP 6) involved drafting a normative specification to support industrial adoption of the technology. MSE led the development of a DIN SPEC draft, incorporating the technical findings and stakeholder feedback gathered through committee work with industry partners. The draft specification outlines the required test methods, material qualification criteria, and design guidelines for hybrid metal‑plastic joints, providing a clear pathway for manufacturers to implement the technology in production.

The collaboration brought together several key partners: Faurecia supplied the automotive context and performed the demonstrator fabrication and testing; EDAG contributed expertise in mechanical design and sensitivity analysis; MSE handled the normative work and the LCA/LCC studies; Gubesch produced the laboratory specimens for material calibration; and INNOVENT e.V. supplied additional industry insights and helped define realistic boundary conditions. The project was funded under the EU Horizon 2020 framework, with a reference to the earlier FlexHyJoin grant (no. 677625) that informed the initial requirements gathering. Despite a schedule delay caused by the late delivery of material samples, the project achieved its objectives of a validated macro‑model, a tested demonstrator, and a draft standard, thereby advancing the state of the art in hybrid joining for lightweight automotive structures.