Stress-Lifetime Characterization of Proton Exchange Membrane Using 3-D Digital Image Correlation and Pressure-Loaded Blister Tests

The strength of the proton exchange membrane (PEM) and its ability to withstand cyclic, environmentally induced stresses plays an important role in membrane integrity and consequently, fuel cell durability. In this study, pressure loaded blister tests are used to characterize the biaxial strength of a model commercially available membrane, Gore-Select® series 57, at the 90°C dry condition under ramped, constant and cyclic pressure loading. Gas leakage is used as the failure criterion, making it analogous to the stresses and failures seen during fuel cell operation. Three-dimensional digital image correlation is used to measure the deformation of the bulging membrane. A quasi-static, spherical pressure vessel approximation of the central portion of the blister then allows the biaxial stress state at this location of the PEM to be tracked through time. A damage accumulation model is applied to the data taken during constant pressure loading to determine the damage parameters. The model is then used to predict the failure of blisters from ramped and cyclic fatigue test modes. The successful lifetime prediction suggests an understanding of the stress state in the blister test and the model’s ability to relate different mechanical loadings and predict failure.