Mechanical degradation of proton exchange membrane along the MEA frame in proton exchange membrane fuel cells

Mechanical degradation, caused by local stress concentration and variation, significantly affects the lifetime of proton exchange membrane fuel cells. This study constitutes the first numerical investigation of stress evolution in the membrane between the frame of the membrane exchange assembly (MEA) and gas diffusion layer (GDL) throughout the processes of assembly, operation and gas filling in fuel cells. A finite element model is outlined to determine mechanical deformation of the membrane by exerting assembly displacement, hygrothermal conditions and gas pressure in turn. It is observed that severe stress concentration and bending deformations occur in the joint-area membrane. The results show that a plastic deformation occurs after the temperature and water content are increased, and would be substantially enhanced by the gas pressure difference between the anode and cathode. The in-plane stress may throw some light on the rapid degradation of the membrane between the frame and GDL. The gas pressure difference, which exceeds 10 kPa, leads to a rapid increase in the in-plane stress and plastic deformation. Decreasing the joint width may not be a good approach for reducing the stress/strain concentration. It is suggested that additional gasket seals or adhesive protection layers are helpful in joining frame and GDL.