Toward physically consistent fatigue life predictions for proton exchange membranes

Accurate evaluation of proton exchange membrane (PEM) fatigue life is essential for predicting durability in polymer electrolyte fuel cells. This study establishes a physically consistent fatigue-life prediction framework by combining stress-strain characterization of the membrane with analytical modeling based on the Smith-Watson-Topper (SWT) parameter and finite element simulations. Fatigue life is evaluated across a range of stress levels and environmental conditions, including different temperatures and relative humidity. The effect of spatial humidity gradients, often overlooked in earlier studies, is incorporated into the in-situ simulations, revealing localized regions of elevated stress and reduced fatigue life. The analytical and numerical approaches show strong agreement and eliminate the non-realistic long lifetimes reported in previous studies under stresses exceeding the membrane yield strength, while also showing close agreement with recent blister-test measurements. Overall, the framework enables more realistic in-situ durability assessment and provides a reliable basis for evaluating membrane performance under practical operating conditions. • Physically consistent fatigue-life model for PEM membranes is developed. • SWT-based predictions agree with finite element and blister-test results. • High stresses above yield give very short, physically realistic fatigue lives. • Humidity gradients control in-situ stress and minimum fatigue life location.