Fatigue crack growth in the Perfluorosulfonic-acid (PFSA) ionomer membranes with mechanical reinforcement and chemical stabilizer represents a key barrier in improving the durability of the polymer electrolyte membrane (PEM) fuel cell. Both ex-situ and in-situ Paris regime fatigue crack behaviors can be evaluated numerically based on the critical plastically dissipated energy (CPDE) ahead of the crack tip. Some fairly good agreement between the finite element (FE) computational crack predictions and the ex-situ experimental crack propagation rates have been found for different polymers in previous work¹. In a similar fashion, the fatigue crack growth criteria (e.g., CPDE) of Nafion^®-based ionomer membranes can be determined numerically at various environmental conditions (RH and T). The determined fatigue crack criteria, then, will be implemented in a 2D unit fuel cell FE model following the reference work² with extensions. Thus, in-situ fatigue crack behaviors of the ionomer membranes can be evaluated in response to different operating circumstances. This numerical scheme can be used to evaluate the mechanical integrity of different ionomer membranes in the screening process by the manufacturer/buyer. Moreover, in further implementations, the results from this modeling can be used in exploring the synergy between chemical (e.g., gas-crossovers) and mechanical failures (e.g., fatigue cracks) in PEM fuel cell membranes.

REFERENCES

1. G. Ding, A. M. Karlsson, and M. H. Santare, Int. J. Fatigue, 94, 89–96 (2017) http://dx.doi.org/10.1016/j.ijfatigue.2016.09.012.
2. G. Ding, M. H. Santare, A. M. Karlsson, and A. Kusoglu, J. Power Sources, 316, 114–123 (2016) http://dx.doi.org/10.1016/j.jpowsour.2016.03.031.