Proton exchange membrane (PEM) fuel cells are electrochemical devices that convert the chemical energy of a fuel directly to electrical energy. They are receiving much attention recently due to their environmentally friendly characteristics, high efficiency, high power density, fast start-up and low noise. Indeed, they are one of the most promising power sources for transportation and portable applications. However, factors such as high cost and low durability remain the greatest barriers to their widespread commercialization and utilization by the automotive companies. In fact, the fuel cell power is currently around 2 times more expensive than the internal combustion engines systems.
Bipolar plates are one of the critical components of PEM fuel cells, comprising the major part of weight, volume and cost. Therefore, their durability and fabrication cost must be optimized to allow fuel cells to penetrate the commercial market and compete with other energy sources. Among the various manufacturing methods currently used to produce bipolar plates, the rubber forming process presents several advantages for thin metallic sheet bipolar plates. The high surface quality and the dimensional accuracy of the formed parts are key features of this technological process, which are indispensable for the considered application. Besides, the metal forming processes are well-known for their high productivity rates, thus adequate for mass production. Nevertheless, the complex geometry of the metallic bipolar plates (multi-array flow channels on surface) requires a careful optimization of the forming process conditions, which is a time-consuming and expensive task using the trial-and-error method.
Nowadays, finite element modelling is an indispensable tool to understand the mechanics involved in the forming process, allowing to improve the formability of metal alloys. The numerical simulation intends to predict the occurrence of forming defects and optimize the shape of rigid tools and process parameters in the design stage. However, the performance of these computer systems is strongly dependent from the numerical models adopted to describe the mechanical behaviour (elastic–plastic for metallic sheets and hyper-viscoelastic for rubbers) and frictional contact conditions. The research team presents a large experience of on traditional sheet metal forming processes, both from the numerical and experimental point of view. Regarding the numerical simulation, the in-house finite element code DD3IMP has been continuous development and optimized by the team to simulate sheet metal forming processes.
The purpose of this project is to develop an accurate numerical model able to successfully simulate the rubber forming process of metallic bipolar plates. Several experimental results will be used to validate the developed numerical model. Simple experimental tests of rubber forming will be carried out to study the formability of the thin sheet using different forming tools (channel design). The comparison between experimental and numerical results will be used to improve the numerical models, namely the parameters of the material constitutive models and the friction law. Additionally, it is expected to define some guidelines for selecting the most appropriate process parameters and the design of the flow channels in order to produce defect-free metallic bipolar plates.