Finite element model for micro-stamping titanium bipolar plate

Abstract. Bipolar plates are the essential components of a Proton Exchange Membrane Fuel Cell. Lightweight bipolar plates can be micro-stamped from an ultrathin metallic foil. A major concern is the manufacturability of the foil in the micro-stamping process. The typical stamped micro-channels have end cavities or corners where the deformation mode can be different from the two-dimensional plane strain conditions that occur at the straight sections of the micro-channels. The thin foil has a large ratio of length (or width) to thickness, and shell elements were often used for three-dimensional models. Currently, it is unknown if the shell elements available in commercial software packages are able to predict the ultrathin material behaviour correctly. In addition, the deformation behaviour and forming limits of titanium foil in the micro-stamping process are not well understood. The current study uses a micro-stamping tool to produce straight micro-channels from commercially pure titanium foil. The experimental data are used to validate a two-dimensional and a three-dimensional finite element model of the process. It is shown that there are deviations between the experimental and the numerical thinning results. Material thinning is different between the straight and the cavity end sections suggesting that three-dimensional process models are required to accurately analyze forming.