Rubber Forming
Due to their functions in the PEM fuel cells (electrical connection between adjacent cells; uniform distribution of the reactants over the membrane electrode assembly through a large array of micro-channels; removal the heat and reaction products from the cell and structural support for the whole fuel cell stack), they must exhibit high electrical and thermal conductivity, good corrosion resistance, low gas permeability, chemical stability and good mechanical performance. Graphite was initially used due to its properties but more recently other materials such as composites and metals have been receiving more attention. Metallic bipolar plates manage to fulfil practically all of these tasks with the added benefit of a reduced weight when compared to graphite being the lower corrosion resistance their downside.
The rubber forming process is a kind of stamping technique suitable for thin sheets, where the conventional rigid die is replaced by a rubber pad. The formed parts have good surface finish due to the contact with the rubber pad (no scratches), the formability of the blank is greatly improved (material thinning is reduced) through the flexible contact surface and the application of the corrosion-protective coating (required to improve the lifetime of the fuel cell) can be performed before rubber forming. Furthermore, the setup time is reduced because the rubber pad and the rigid punch do not need to be assembled precisely, reducing the overall production cost. The main drawback of this process for mass production is the short operating life of the rubber pad (average lifespan 1000–5000 pieces).
Thus, studies should focus on prolonging the life of the rubber pad by changing the structure of the container and the rigid punch. On the other hand, the incompressibility of the rubber yields almost uniform pressure on the blank sheet surface, leading to low forming pressures and consequently potential wrinkling occurrence
The main goal of this proposal is to investigate the capability of the rubber forming process to produce defect-free metallic bipolar plates. As previously mentioned, the in-house finite element code DD3IMP will be used due to its recognised efficiency. Furthermore, the laboratory facilities available in both universities are adequate to perform the required experimental tests as well as the experience and expertise of the research team to perform this kind of work. The project will address theoretical analysis, physical tests in laboratory and numerical modelling of the process, bearing in mind the practical application perspective.
The rubber forming process is a kind of stamping technique suitable for thin sheets, where the conventional rigid die is replaced by a rubber pad. The formed parts have good surface finish due to the contact with the rubber pad (no scratches), the formability of the blank is greatly improved (material thinning is reduced) through the flexible contact surface and the application of the corrosion-protective coating (required to improve the lifetime of the fuel cell) can be performed before rubber forming. Furthermore, the setup time is reduced because the rubber pad and the rigid punch do not need to be assembled precisely, reducing the overall production cost. The main drawback of this process for mass production is the short operating life of the rubber pad (average lifespan 1000–5000 pieces).
Thus, studies should focus on prolonging the life of the rubber pad by changing the structure of the container and the rigid punch. On the other hand, the incompressibility of the rubber yields almost uniform pressure on the blank sheet surface, leading to low forming pressures and consequently potential wrinkling occurrence
The main goal of this proposal is to investigate the capability of the rubber forming process to produce defect-free metallic bipolar plates. As previously mentioned, the in-house finite element code DD3IMP will be used due to its recognised efficiency. Furthermore, the laboratory facilities available in both universities are adequate to perform the required experimental tests as well as the experience and expertise of the research team to perform this kind of work. The project will address theoretical analysis, physical tests in laboratory and numerical modelling of the process, bearing in mind the practical application perspective.