Investigation of the influence of tool geometry on sheet thinning of bipolar plates in multi-stage embossing

The mobility sector is a major contributor to greenhouse gas emissions in the European Union (EU). One approach to reduce these emissions and meet EU climate targets is the use of alternative propulsion concepts, such as hydrogen fuel cells (FC). The economic efficiency of the FC is closely tied to their performance, which depends on multiple criteria, such as the reactant distribution and water management. A key component of the FC is the bipolar plate (BPP), as its channel structure directly impacts these criteria. Today, a BPP is typically formed using multi stage embossing. However, in multi-stage embossing, the optimization of the channel structure regarding the performance of the FC is limited by the plastic deformation capacity of the material used for the Bpp During embossing the material experiences plastic deformation, resulting in sheet thinning. Once a critical thinning is reached, the channel structure tears. One way to reduce sheet thinning is by controlling the material flow during embossing. In multi-stage embossing, the material flow can be controlled by adjusting the tool geometry of each embossing step. Therefore, this paper investigates the influence of the tool geometry of the individual embossing steps on material flow and its effect on the resulting sheet thinning of BPP in multi-stage embossing.