Abstract
Porous carbon fiber papers, which are formed by randomly distributed carbon fibers, are commonly used as gas diffusion layers of proton exchange membrane fuel cells. Several key properties of the gas diffusion layers, for example, air permeability, thermal conductivity, and electrical resistance, are inevitably controlled by the strain it experienced, which is always a nonlinear function of the applied compressive stress. In the present study, a logarithmic-type constitutive model is proposed to characterize the nonlinear stress–strain relation of carbon fiber papers under compressive loading. A hexahedral configuration of carbon fibers is adopted as a typical microstructure of carbon fiber papers. Contact and bending deformation of carbon fibers are accounted for with use of Hertz’s contact model and beam bending model, respectively. The logarithmic-type constitutive model is eventually obtained by solving a differential equation considering the variation of structural porosity. The stress–strain curves of the present model and experimental data are compared for a number of commercial gas diffusion layer samples. The comparisons indicate that the present model is capable of predicting the mechanical performance of carbon fiber papers, and may be useful for analytical and numerical analysis of gas diffusion layers and fuel cells.
Highlights
Proton exchange membrane fuel cells (PEMFCs) are considered as promising power sources for motor vehicle, stationary and portable equipment due to their high power density and environmentally friendly properties.[1]
By ignoring the contact component, the differential strain–stress relation of Gas diffusion layer (GDL) unit cell can be formulated as dε = 1+ ε dσ Solving equation (16), the simplified constitutive model of carbon fiber papers can be expressed in the form of σ ε = eηEb −1 (17)
A hexahedral configuration is used as a typical microstructure of carbon fiber papers
Summary
Proton exchange membrane fuel cells (PEMFCs) are considered as promising power sources for motor vehicle, stationary and portable equipment due to their high power density and environmentally friendly properties.[1]. 16l3 Apore εb where εb is the average compressive strain induced by bending deformation, l denotes the average edge length of unit cell, μ is the porosity of carbon fiber papers, and Cl and CD are the coefficient of variation of l and D, respectively.
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