Fabrication of metallic bipolar plates in PEM fuel cell using semi-stamp rubber forming process

Abstract

Metal is considered to be a good material for a bipolar plate due to its good electrical conductivity, excellent mechanical properties, and low cost. In this study, fabrication of metallic bipolar plates with serpentine flow field microchannels was investigated by a novel rubber pad forming process. Stainless steel 316 with thickness of 0.1 mm was used. Polyurethane rubbers with the hardness of shore A40, A55, A65, and A90 and the thickness of 10, 20, and 30 mm were used in this study to manufacture bipolar plates. At first, convectional rubber pad forming process was used to produce bipolar plates by some experimental tests. In this step, the effect of applied force, rubber hardness, and rubber thickness on filling percentage, thickness distribution, and dimensional accuracy was investigated. The results showed that filling percentage would increase by rising applied force, but channel depth was not equal in different directions. Increases in rubber hardness led to improving uniformity in channel depth. In addition, decreases in rubber hardness and increases in rubber thickness caused higher filling volumes. However, maximum filling percentage, dimensional accuracy, and thickness distribution in convectional rubber forming process were not satisfying. Thus, a novel method was developed in this study in order to improve the quality of fabricated bipolar plates named semi-stamp rubber forming. The results indicated that using semi-stamp rubber forming instead of convectional rubber forming would lead to 11.7, 9, and 1.075% improvement in filling percentage, thinning percentage, and dimensional accuracy, respectively. According to the results, the developed model (semi-stamp rubber forming) could be a feasible technique in fabricating metallic bipolar plates.