Non-uniform stress distribution characteristics and structure-related modeling approach of proton exchange membrane under durability protocol conditions

The non-uniform stress distribution and localized incompatible deformation of proton exchange membrane (PEM) in fuel cells, driven by variable temperature and humidity conditions, are significant factors contributing to its mechanical degradation and reduced durability. Current understanding is limited by ex-situ, small-scale experiments under isolated operating conditions, which fail to fully represent the stress distribution and damage characteristics experienced during fuel cell operation. In this study, the stress distributions in PEM under various durability testing protocol conditions are explored using a combination of computational fluid dynamics and a viscoelastic-plastic constitutive model of materials. The results reveal that operating conditions significantly affect the stress distribution within the PEM, with the “water flooding” phenomenon caused by hydration reaction and electroosmotic drag, especially prevalent under high humidity and current density conditions, which may significantly alter the spatial characteristics of stress distribution. Moreover, the stress distribution throughout the entire reaction zone of the PEM is non-uniform, with higher stress amplitudes observed in the middle of the channel. Specific regions, such as the inlet and outlet of the flow channel and the cathode side of the PEM, are especially prone to localized stress concentrations, increasing the risk of mechanical degradation. These findings provide deeper insight into the mechanical durability of PEM in fuel cell structures.