Characterization of the interfacial normal stress between current collector and gas diffusion layer in epoxy packaging micro fuel cells using FEM analysis

In order to improve the performance of an epoxy packaged micro fuel cell, the effects of different endplate design on the interfacial normal stress between current collector (CC) and gas diffusion layer (GDL) of the fuel cell are investigated in this paper. Firstly, endplates with different numbers of embossments are constructed, then a three-dimensional finite element model of the fuel cell package is set up to characterize the changing history of the interfacial normal stress between CC and GDL during the packaging processes. A multi-linear elastic model is used to describe the stress-strain relationship of the cured epoxy and GDL in this study. The initial clamping pressure of 1Mpa, 1.5Mpa and 2Mpa are applied to the endplates in turn. During the curing process, the epoxy resin is firstly heated at 80°C for 3.5 hours, then the temperature is decreased to 20°C before the fuel cell is demoulded. The technique of “birth and death of element” is implemented to simulate the stress history in epoxy package before and after the fuel cell is demoulded. From the simulation results, the normal stress of every contact point between CC and GDL is extracted to obtain the pressure distribution in different design of the package. Results show that the interfacial normal stress between CC and GDL increases with the increase of initial clamping pressure, and decreases by stages during the packaging process. The distribution form of the stress is also established from the results. Effects of endplates structure and initial clamping pressure on the interfacial normal stress then can be acquired. In summary, the proposed methods we used in this study can be helpful in design and optimization of the micro fuel cell packaging.