Mechanical behavior of fuel cell membranes under humidity cycles and effect of swelling anisotropy on the fatigue stresses

Kusoglu, Ahmet; Karlsson, Anette M.; Santare, Michael H.; Cleghorn, Simon; Johnson, W.B.

doi:10.1016/j.jpowsour.2007.03.063

Cited by 242 publications

(246 citation statements)

References 12 publications

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“…Finally, the finite element simulation results for various configurations of the composite membrane are presented in Section 4. The in-plane stresses in the membrane, which have been shown to be related to crack initiation [24,35] and further degradation of the membrane, are reported for selected conditions. The effects of symmetric RH cycling (equal application from the cathode and the anode sides), asymmetric RH cycling, membrane thickness and clamping pressure are discussed for various layering config urations of the composite membrane.…”

Section: Introductionmentioning

confidence: 99%

“…Assuming a NeoeHookean hypere lastic formulation for the constitutive response of the spring in this EV2 network [37], the Cauchy stress, s , is given by [25] Assumed not to swell Neglected dimensional form of the flow rate for the dashpot in this network constructed a model for a representative repeating element is given by adapted from our previous work [25,32,35,40] consisting of a half of a land and a half of a groove with the dimensions given in Fig. 8.…”

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confidence: 99%

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Time-dependent mechanical response of a composite PFSA membrane

Khattra

Karlsson

et al. 2013

Journal of Power Sources

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Time-dependent mechanical response of a composite PFSA membrane

Khattra

Karlsson

et al. 2013

Journal of Power Sources

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“…2 PFSA membranes typically swell with exposure to humid air or water due to their hydrophilic nature. Our previous numerical simulations have shown that swelling is the predominant driving force in the development of mechanical stresses in the PEM during fuel cell operation [18]. However, since the tensile and relaxation tests were conducted in an environmental chamber, it is difficult to continuously measure the dimensions of the specimen at the time of testing.…”

Section: Introductionmentioning

confidence: 99%

An experimental investigation of strain rate, temperature and humidity effects on the mechanical behavior of a perfluorosulfonic acid membrane

Lugo

Santare

et al. 2012

Journal of Power Sources

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“…We speculate that the yield stress is related to crossover of the chain slip rate from equation (5) to equation (6).…”

Section: Famentioning

confidence: 94%

A mathematical model for predicting the life of polymer electrolyte fuel cell membranes subjected to hydration cycling

Burlatsky¹,

Gummalla²,

O'Neill³

et al. 2012

Journal of Power Sources

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Under typical PEM fuel cell operating conditions, part of membrane electrode assembly is subjected to humidity cycling due to variation of inlet gas RH and/or flow rate. Cyclic membrane hydration/dehydration would cause cyclic swelling/shrinking of the unconstrained membrane. In a constrained membrane, it causes cyclic stress resulting in mechanical failure in the area adjacent to the gas inlet. A mathematical modeling framework for prediction of the lifetime of a PEM FC membrane subjected to hydration cycling is developed in this paper. The model predicts membrane lifetime as a function of RH cycling amplitude and membrane mechanical properties. The modeling framework consists of three model components: a fuel cell RH distribution model, a 2 hydration/dehydration induced stress model that predicts stress distribution in the membrane, and a damage accrual model that predicts membrane life-time. Short descriptions of the model components along with overall framework are presented in the paper. The model was used for lifetime prediction of a GORE-SELECT membrane. I: Introduction:Mechanical degradation of PEM membrane can limit stack lifetime. Operation of a fuel cell under realistic load cycles results in both chemical and mechanical degradation of the polymer electrolyte membrane. Degradation of the membrane causes opening up of pinholes or crazing of polymer [1,2,7] increasing gas-crossover and subsequently resulting in catastrophic failures of the fuel cell stack.Understanding and modeling the mechanical degradation mechanism and kinetics enables prediction of membrane lifetime as a function of PEM operational conditions and optimization of membrane structure through the choice of reinforcement [4], the membrane processing methods and the operating conditions. The physics based model of membrane mechanical degradation could guide the synthesis of new membranes with tuned mechanical properties and enhanced life in a fuel cell.Hydration cycling is a primary cause of the mechanical degradation of a geometrically constrained polymer, which exhibits dimensional changes with varied water content. A simple way to impose mechanical damage to a geometrically constrained PEM membrane is to subject it to humidity cycling. At high RH, the membrane absorbs water, and at low RH, the membrane desorbs water. Such RH cycling would result in swelling 3 and shrinking of an unconstrained polymer. RH cycling of a constrained polymer causes cyclic stress. In PEM, such geometrical constraints are imposed by bipolar plate ribs through the gas diffusion layers (GDLs), catalyst layers adjacent to the membrane and at the seals. Moreover, we hypothesize that internal stress in the membrane can be caused by the difference in gas RH at the anode and cathode membrane surfaces that routinely occurs at fuel cell operational conditions. Cyclic stress in the membrane causes irreversible elongation of the membrane [7] and subsequent formation of crazes and cracks that causes gas crossover through the membrane and stack failure.The goal of...

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Mechanical behavior of fuel cell membranes under humidity cycles and effect of swelling anisotropy on the fatigue stresses

Cited by 242 publications

References 12 publications

Time-dependent mechanical response of a composite PFSA membrane

Time-dependent mechanical response of a composite PFSA membrane

An experimental investigation of strain rate, temperature and humidity effects on the mechanical behavior of a perfluorosulfonic acid membrane

A mathematical model for predicting the life of polymer electrolyte fuel cell membranes subjected to hydration cycling

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