Mechanical Nonlinearity and Microscale Deformation of Gas Diffusion Layer in Proton Exchange Membrane Fuel Cell

The gas diffusion layer (GDL) is one of the core components of the proton exchange membrane fuel cell. The complex internal structure of the GDL makes it challenging to accurately predict the mechanical response during clamping compression. In this study, the mechanical properties of the carbon paper-based GDL were investigated using a combination of experimental and numerical simulation. The explicit finite element method (FEM) was used to perform quasi-static compression simulations on the reconstructed GDL. The simulation accounted for the fiber dynamic contact, predicting the true deformation of the GDL. Validation between simulation and experiments was conducted, identifying the initiation point of fiber fracture failure during the compression. The effective range of the elastic constitutive model was determined. The changes in tortuosity, effective diffusivity, absolute permeability, and conductivity in different directions were examined. Reliable experimental results were obtained when the sample quantity was five. Initially, the stress-strain curve exhibited distinct nonlinear characteristics. The equivalent elastic modulus of the GDL continuously increased, stabilizing after a certain compression ratio. With a compression ratio of 27%, the elastic model could accurately reflect the mechanical properties of GDL. Beyond this range, the fiber began to fracture, at which point the stress was 0.064 MPa. Bending and frictional sliding were the main deformation modes of the carbon fibers. The gas diffusion capacity increased first and then decreased; for in-plane direction and through-plane direction, the maximum value appeared at 10 and 5% compression ratio, respectively. The permeability was reduced monotonously. The mass transfer capacity in the in-plane direction of the carbon paper was superior to that in the through-plane direction. The effective conductivity increases in through-plane and in-plane directions were 1354.8 and 57.9%, respectively, at a compression ratio of 35%. Combined with the macroscopic and microscopic levels, it provides a reference for an in-depth understanding of the compressive mechanical properties of fiber porous media and improving the performance of fuel cells.