Journal
JOURNAL OF POWER SOURCES
Volume 316, Issue -, Pages 114-123Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jpowsour.2016.03.031
Keywords
Polymer electrolyte membrane (PEM); Durability; Fatigue; Cyclic crack growth; Plastically dissipated energy; Numerical simulation
Funding
- Energy Efficiency and Renewable Energy, Office of Fuel Cell Technologies, of the U.S. Department of Energy through Lawrence Berkeley National Laboratory (LBNL) [DE-AC02-05CH11231]
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Understanding the mechanisms of growth of defects in polymer electrolyte membrane (PEM) fuel cells is essential for improving cell longevity. Characterizing the crack growth in PEM fuel cell membrane under relative humidity (RH) cycling is an important step towards establishing strategies essential for developing more durable membrane electrode assemblies (MEA). In this study, a crack propagation criterion based on plastically dissipated energy is investigated numerically. The accumulation of plastically dissipated energy under cyclical RH loading ahead of the crack tip is calculated and compared to a critical value, presumed to be a material parameter. Once the accumulation reaches the critical value, the crack propagates via a node release algorithm. From the literature, it is well established experimentally that membranes reinforced with expanded polytetrafluoroethylene (ePTFE) reinforced perfluorosulfonic acid (PFSA) have better durability than unreinforced membranes, and through-thickness cracks are generally found under the flow channel regions but not land regions in unreinforced PFSA membranes. We show that the proposed plastically dissipated energy criterion captures these experimental observations and provides a framework for investigating failure mechanisms in ionomer membranes subjected to similar environmental loads. (C) 2016 Elsevier B.V. All rights reserved.
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