Fatigue and creep to leak tests of proton exchange membranes using pressure-loaded blisters

Aspects of fatigue failure mechanisms in polymer fuel cell membranes

“…4,12,15 For example, Liu et al 12 investigated the lifetime of various fuel cell membranes by measuring the H 2 cross over rate and found that mechanical reinforcement with ePTFE provides an effective blunting mechanism that helps to slow the propagation of cracks. Li et al 23 also found that the reinforcement phase could delay the formation of life prediction model is beyond the scope of this article.…”

“…9 Also, the in-plane stress components are the ones most directly associated with the through-the-thickness cracks, which are of primary concern in the mechanical failure of fuel cell membranes. 9,23 The overall mechanical response of the MEA is shown in Figure 6 as in-plane stress for the three RH cycles considered: (i) 0-150% RH, (ii) 50-150% RH, and (iii) 80-150% RH at the cell operating temperature of 80 °C . The results suggest that stress amplitude, or ''fatigue stress,'' Dr, in the plane, increases with increasing amplitude of water content, Dk.…”

“…4,6,17,22 A similar trend was also observed in an ex situ fatigue test where the density of cracks was found to increase with an increase in the applied tensile stress. 17 Cracks at the fractured surface can propagate through the membrane eventually resulting in 3,7,23 gas leakage or crossover.…”

“…Ex situ characterization of the fracture behav ior of PFSA membranes has been reported in a series of pub lications by Dillard and coworkers. 22,33,34 For example, in a recent study by Li et al, 23 the ex situ fatigue response of polymer fuel cell membranes under biaxial loading was investigated using pressure-loaded blisters. They obtained typical fatigue lifetime curves that consist of a crack forma tion-dominated zone at high stress levels and a crack propa gation-dominated zone at low stress levels.…”

“…In the crack for mation-dominated zone, cyclic stresses have been found to decrease faster than in the propagation-dominated zone, which is attributed to the crack/craze formation. 23 Tang et al 17 also studied the ex situ fatigue behavior of PFSA membranes by conducting a cyclic tensile stress test. Cross over of gasses was found to increase with increasing RH am plitude, which can be attributed to the larger swellingshrinkage stresses.…”