PEM fuel cell nowadays is expensive for widespread commercialization, though it has obvious advantages, such as high efficiency, high power density, fast startup and high system robustness. As one of the most important and costliest components in the PEM fuel cell stack, bipolar plates (BPPs) account for more than 80% of the weight and 30% of the cost of the whole stack. By replacing the conventional graphitic or machined thick metal plates with the lightweight and low-cost thin metallic sheet BPP with sustainable coating, PEM fuel cell will become an attractive choice for manufacturers. In this study, the fabrication of micro-channel features by flexible forming process (FFP) are studied first, which demonstrates the feasibility of using FFP to manufacture thin metallic BPPs. Then, the obtained knowledge is applied onto the fabrication of real thin metallic BPPs with some process amendment. The first investigation of this study focuses on the forming of micro-channel features with 100 μm thickness stainless steel sheet. A finite element analysis (FEA) model is built and key process parameters (hardness of soft tools used in FFP, friction coefficients between contact surfaces) associated with the formability of BPPs are studied. The FEA is partly validated by the experiments. In the second investigation, finite element analysis method is adopted in the design of the BPP forming process. Based on the numerical simulation results, the die setup is prepared and some process amendments are made to improve the formability of BPPs. As a result, high quality metallic BPPs are obtained in the latter experiments, which demonstrates the feasibility to manufacture the metallic bipolar plate by FFP.
Numerical and Experimental Study for Improvement of Formability in Flexible Forming Process
