Abstract
The mechanical loads that gas diffusion layers (GDLs) withstand in polymer electrolyte membrane fuel cell (PEMFC) stacks are sensitive to the assembly and working conditions. The mechanical properties of GDLs mostly depend on their composition materials, microstructural characteristics, operation conditions, etc. An accurate and comprehensive understanding of the mechanical performance of GDLs is significant for predicting the stress distribution and improving the assembly technology of PEMFC stacks. This study presented a novel 3-D nonlinear and orthotropic constitutive model of a carbon paper GDL to represent the material stiffness matrix with its compressive, tensile, and shear properties. Numerical simulations were performed based on the 3-D constitutive model, and the proposed 3-D model was validated against the experimental data reported previously. It is found that the simulation results of the 3-D constitutive model show a good agreement with the experimental results. Besides, the novel 3-D nonlinear and orthotropic model was applied in the overall stress simulation of a simplified PEMFC unit cell, compared to a conventional 3-D linear and isotropic model, and the simulation results of the two models show a significant difference.
Highlights
As one of the most promising fuel cells, polymer electrolyte membrane fuel cells (PEMFCs) have attracted increasingly more attention owing to their excellent properties, such as low emission, noiselessness, high efficiency, high specific power, etc
A PEMFC unit [1] typically consists of a polymer electrolyte membrane or proton exchange membrane (PEM) in the middle, a catalyst layer (CL), a gas diffusion layer (GDL), and a bipolar plate (BPP) in the anode and cathode regions, respectively
In Equation (5), it is found that a 3-D material matrix of an orthotropic material, including its compression, tension, and shear descriptions, is typically employed to state the overall mechanical performance
Summary
As one of the most promising fuel cells, polymer electrolyte membrane fuel cells (PEMFCs) have attracted increasingly more attention owing to their excellent properties, such as low emission, noiselessness, high efficiency, high specific power, etc. Located between a BPP and a CL, the GDL takes crucial responsibilities for PEMFCs, such as providing mechanical supports, collecting the current, reducing contact resistance, transporting gas and water, etc. Carbon paper GDLs have high porosity and permeability because their porous structures result in efficient passageways for water and gas across PEMFCs [8]. Once mechanical fractures or breakages occur, the internal carbon fiber connections change correspondingly, resulting in changes in the thermal and electrical conductivity [10,11,12], porosity and permeability [13,14], and the current density of fuel cells [15]. Mechanical failures in GDLs, such as fractures or breakages of carbon fibers in the substrate and cracks in the MPL, greatly influence the overall performance and mechanical durability of fuel cells. Studying the mechanical performance of GDLs is fundamental, which can guide the performance improvement of PEMFC stacks
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