Manufacturing metallic bipolar plate fuel cells through rubber pad forming process

Abstract

Bipolar plates are considered one of the most important parts of fuel cells, made of different materials. Graphite bipolar cells are generally expensive, hence high machining cost. Metals are known to be suitable replacements due to their lower weight and cost. Bipolar plates can be designed and produced using either a concave or convex pattern. This study made an effort to fabricate metallic bipolar plates through two-die rubber pad forming method with both convex and concave patterns. Stainless steel sheets of 316 with the thickness of 0.1 mm were used for the fabrication. Polyurethane with the hardness of shore A 85 and the thickness of 25 mm was selected. The effect of forming forces on micro-channel filling depth, thickness distribution of channels in each of the patterns, and their appropriate states (maximum filling depth and minimum thickness reduction) were also studied. The results indicated that in similar geometry and process, the convex die would create a deeper channel compared with the concave one. Increases in forming forces would cause the filling depth of micro-channels to rise, but the thickness of critical regions to decrease due to an increase in the aspect ratio (the ratio of channel depth to channel width). Finally, the best possible version of bipolar plates in both convex and concave models was formed.