Fatigue crack growth behavior of proton exchange membrane in fuel cells under humidity cycling

Improving the mechanical durability of proton exchange membrane is important to ensure the longevity of fuel cells. Therefore, the mechanisms of fatigue crack growth of the membrane in fuel cells during humidity cycles are critical issues. In this paper, a cyclic cohesive finite element method is used to predict the fatigue crack growth of the membrane. It is found that humidity amplitude has significant effects on the durability and that the crack under the channel is more prone to grow. Furthermore, both clamping conditions and channel geometry can also greatly affect the durability of the membrane. The squeezing effect in the direction perpendicular to the pre-crack and the bulging effect in the direction parallel to the pre-crack also compete with each other. As a result, the clamping displacement can be favorable to the durability of the membrane when its squeezing effect is stronger than its bulging effect. The results also suggest that deviating the channel or having triangular and semi-elliptical channels can improve the durability of the membrane.