Investigation of failure during rubber pad forming of metallic bipolar plates

In this study, the forming of metallic bipolar plates micro-channel was investigated. Rubber pad forming process was employed to fabricate the parallel micro-channels. According to the experimental observation, the onset of failure was the main limiting factor during the deformation of micro-channels. Therefore, the fracture behavior was studied during rubber forming processes. Experimental analysis with the finite element model (FEM) simulation was adopted to investigate the fracture mechanism. Three different fracture criteria were used to predict the fracture. Critical damage values were determined through conducting the uniaxial tension test. The fracture surface was constructed using ductile fracture criteria, and the most accurate fracture prediction was obtained via normalized Cockroft-Latham fracture criterion (9.14% fracture prediction error). The effect of process parameters on stress triaxiality and normalized Lode angle parameter was analyzed by FEM simulation results. According to the results, process parameter variation did not significantly affect the stress state. Thus, the normalized Cockroft-Latham fracture criterion was employed to investigate the onset of fracture in different forming conditions and the effect of process parameters on damage evolution. Based on the findings, draft angle, corner radius, and the ratio of w/h should be set to 15 degrees, 0.2 mm, and 1.6 in order to achieve 100% filling percentage.