Tool concepts and part characteristics of simultaneously formed sheet metal and long fiber-reinforced thermoplastic components

Abstract

This study investigates a hybrid forming process for the simultaneous manufacturing of complex parts consisting of sheet metal and long fiber-reinforced thermoplastics (LFT), specifically glass fiber-reinforced polyamide 6 (PA6 GF40). This approach integrates sheet metal forming and LFT compression molding within a single tool and process step. Adhesive bonding between the metal and LFT was achieved during the process using a bonding agent previously applied to the sheet metal. Various tool concepts were developed and experimentally evaluated to form different open-ended, complex-shaped hybrid parts in a single-step process. Special attention was given to sealing concepts to prevent the press-out of LFT during forming. The manufactured hybrid parts were analyzed with respect to sheet metal forming behavior, geometrical accuracy, and LFT filling using optical measurement and cross-sectional analysis. Finally, a longitudinal control arm for the multi-link rear axle of the current VW Golf was manufactured and evaluated. The results demonstrate that the new integrated tool design enables reliable forming of hybrid parts with complex geometries. Excellent forming results were obtained for DC04 and DP600 steels, while DP800 steel showed localized thinning and partial underforming. The developed tool concepts ensured effective sealing and prevented LFT leakage, enabling full cavity filling when appropriate process parameters were selected, thereby proving the concept for real industrial parts. Thus, this process offers significant potential for lightweight multi-material structures in automotive applications by reducing process steps.