In-situ pressure differential-accelerated mechanical fatigue testing and modeling of a reinforced fuel cell membrane

Modern polymer electrolyte fuel cells typically use reinforced membranes for improved mechanical durability. Due to costly experimentation, however, the fatigue properties of these membranes remain poorly understood. In this work, we employ the G ' Sell-Jonas constitutive material model to investigate the mechanical fatigue response of a reinforced membrane under various environmental conditions in accelerated in-situ test settings. For fatigue evaluation, we utilize a novel pressure differential-accelerated mechanical stress test (Delta P-AMST) of shorter duration (<1 week) than previous AMSTs. The S-N curves constructed from experimental results at variable Delta P and temperature demonstrate inverse linear relationship between logarithmic fatigue lifetime and nominal stress, with greatly enhanced (similar to 10x) lifetime at reduced temperature. According to the results, a finite element-based fatigue model is developed and validated, which considers the impacts of hygrothermal fluctuations and strain rates. The model shows peak tensile stress during the dry phase at the center of the test section, which is consistent with the expected scenario for in-situ fuel cell membrane fatigue. Through this novel accelerated test and its modeling, it becomes possible to assess the fatigue lifetime of reinforced membranes under variable temperatures, humidity swings, pressure differentials, and swelling properties, in much shorter time than with standard protocols.