Investigation on forming methods in rubber pad forming process used for fabricating Cu/Ni clad foil microchannel

Rubber pad forming is a promising stamping process to prepare bipolar plates for proton exchange membrane fuel cells. And it is necessary to discuss whether rubber pad forming process with a rigid convex die (RVD) or a rigid concave die (RCD) is used to prepare bipolar plates. This paper investigates the forming process of bipolar plates by the rubber pad forming experiments and simulations with RVD and RCD method. Cu/Ni clad foils with a 100 μm thickness were used as the experimental material. The effects of stacking order and size effects on product quality were analyzed in detail. The results show that the two forming methods exhibit opposite forming process. The RCD method follows a “top-bottom” sequence and the RVD method follows a “bottom-to-top” sequence. Greater forming loads and strokes occur in the RCD method due to the large deformation of the rubber. The microchannel in the RCD method is subjected to higher stress and exhibits greater strain. Strain concentrations are located at the junction of top fillets and sidewall in the RCD method and the junction of bottom fillet and sidewall in the RVD method. Stacking order affects microchannel quality for Cu/Ni clad foils. Cu-Ni order in the RCD method and Ni-Cu order in the RVD method were employed to avoid severe local thickness thinning. As the grain size increases, the surface roughness and the thickness thinning in the major deformation area increase significantly. This findings point out the differences in the forming process and product quality of the rubber pad forming process with a rigid convex and concave die and promote the application of clad foils to fuel cell bipolar plates.