Use of mechanical tests to predict durability of polymer fuel cell membranes under humidity cycling

A mechanical fatigue life analysis of the type used for lifetime predictions in structural materials has been adapted to characterize PEM fuel cell membranes. It is shown that a stress vs. cycles-to-failure (S–N) curve analysis is capable of: (1) predicting the mechanical durability of PEM membranes under humidity cycling, and (2) assessing the fraction of membrane life remaining in degraded MEAs. Mechanical fatigue testing was performed in a dynamic mechanical analyzer (DMA) at 60 °C and 90% relative humidity (RH) under different values of stress amplitude, and the results were used to plot the S–N curve. The stress amplitude for the S–N curve was then mapped to the equivalent change in RH as a methodology for characterizing membrane mechanical resistance to humidity cycling.

Research highlights▶ Mechanical fatigue testing mimics membrane stresses during humidity cycling. ▶ Cycles to failure in fatigue can be used to predict new membrane life. ▶ Fatigue testing of degraded membranes gives predictions of remaining life.