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

Burlatsky, S. F.; Gummalla, Mallika; O'Neill, J.S.; Atrazhev, V.M.; Varyukhin, Anton; Дмитриев, Д. В.; Érikhman, N. S.

doi:10.1016/j.jpowsour.2012.05.005

Cited by 47 publications

(24 citation statements)

References 35 publications

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“…Mechanical stresses induced by temperature and relative humidity (hygrothermal) cycles during PEM fuel cell operation play an important role in the initiation and evolution of micro‐scale mechanical defects in the MEA 1, 4, 5, 9–12. The membrane swelling and shrinking in response to the humidity and temperature variations result in in‐plane compressive and tensile stresses in the membrane.…”

Section: Introductionmentioning

confidence: 99%

“…They provided a failure curve which predicted the membrane life as a function of relative humidity (RH) cycling amplitude. Burlatsky et al 11 developed a mathematical model for predicting the membrane life using molecular theory which included membrane non‐linear viscoelasticity. Their model showed an exponential decrease in membrane life with increasing the RH cycling amplitude.…”

Section: Introductionmentioning

confidence: 99%

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Humidity and Temperature Cycling Effects on Cracks and Delaminations in PEMFCs

Banan

Bazylak

2015

Fuel Cells

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Temperature and relative humidity (hygrothermal) cycles during PEM fuel cell operation can lead to the introduction and exacerbation of micro‐scale mechanical defects. We developed a two‐dimensional finite element model based on cohesive zone theory to describe the delamination propagation at the cathodic membrane/catalyst layer interface due to temperature and hygrothermal duty cycles. Particularly, the effects of hygrothermal cycle amplitudes, relative humidity (RH) distribution profiles, and gas flow channel position were studied. It was found that doubling the hygrothermal cycle amplitude resulted in a 6‐fold increase in fatigue stresses, and a defect length growth to 0,1 mm before reaching the end of the fuel cell life (40,000 cycles). A counter intuitive result was also observed, whereby a crack located within the membrane was found to grow faster than a delamination located at the catalyst layer/membrane interface. When introducing an anode/cathode channel offset, a 2‐fold increase in the rate of delamination propagation was found compared to the case with the aligned anode and cathode channels.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Humidity and Temperature Cycling Effects on Cracks and Delaminations in PEMFCs

Banan

Bazylak

2015

Fuel Cells

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“…109 Based on an initial model for the behavior at different relative humidities the distribution of stress in the membrane is calculated. These values serve as input for the degradation model with in turn yields a prediction of membrane lifetime, which showed good agreement with experiments.…”

Section: Degradation Modelsmentioning

confidence: 99%

Accelerated Degradation of High-Temperature Polymer Electrolyte Fuel Cells: Discussion and Empirical Modeling

Reimer

Schumacher

Lehnert

2014

J. Electrochem. Soc.

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Accelerated stress tests are commonly applied in order to obtain a prediction of fuel cell life time within a short testing period. The stress test in this work considers a fuel cell which is constantly under load with frequent periods of very high current. Four different cells were operated each with a specific load profile. As a result severe performance degradation was observed in the region of high current densities. A short overview over the phenomena which may contribute to this specific fuel cell degradation is compiled from literature. Based on this overview major degradation modes are identified and combined with a simple polarization curve model. The modeling results allow for two different interpretations. Carbon corrosion reactions can explain the observed effects if cell voltage is assumed as the driving force for degradation. A better fit was obtained by using the overall heat flux as degradation criterion. In this case an increase in local temperature could lead to redistribution and loss of phosphoric acid from the MEA. The expected lifetime of a polymer electrolyte fuel cell (PEFC) ranges from 5 000 h for mobile application to 40 000 h for stationary application.1,2 In order to gain information about time dependent degradation in advance accelerated test protocols are used.3,4 Depending on the design of these tests valuable information about the nature of the main degradation mode under the applied operation conditions can be obtained. Despite the difference in operation conditions for PEFC, HT-PEFC and PAFC the structure and material of the electrodes are almost the same. Consequently, observed degradation phenomena show strong similarities.5 A good description of these phenomena can be found in several review papers 6-13 as well as in at least four books 1,2,14,15 where recent experimental facts and interpretations are summarized. A compact description can also be found in a recent review paper on modeling transport phenomena in PEFCs. 16 The purpose of this paper is to present the results of a specific accelerated degradation test for high temperature polymer electrolyte fuel cells (HT-PEFC) with phosphoric acid doped polybenzimidazole (PBI/H 3 PO 4 ) membranes. The fuel cell is constantly under load with frequent periods of very high current. In order to accelerate degradation effects the fuel cell is operated beyond it's point of maximum power. A simple polarization curve model is used as starting point for the analysis of data. Based on this first analysis a degradation model is proposed which allows for a straightforward physical interpretation. The complexity of degradation effects which occur simultaneousy usually leads to models which either resolve a specific mechanism in depth or describe more general effects. This paper aims at general effects which requires a broader understanding of degradation. In the following it is attempted to provide an overview over the phenomena which may contribute to fuel cell degradation. Based on this overview major degradation modes are identified and ...

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“…The Gauss-Eyring model predicts logarithmical dependence of Y on deformation rate, which agrees with the most of the experimental data for the glassy polymers. The Eyring model was extended to the case of stress relaxation under constant loading in [2]. However, the microscopic interpretation of the yield stress of high-elastic polymers is still unclear.…”

Section: Engineering Stress Mpamentioning

confidence: 99%

“…In the current model, we consider a fraction of the PTFE lamella between two SCS and one of this SCS as a repeating unit. We estimate the yield stress of the polymer above the glass transition temperature as ( ) ( ) 2 1 L T f T eq YS ≈ σ (28) Here L 2 is a mean cross-sectional area per one SCS, which is used as a fitting parameter. In general, L is a function of temperature.…”

Section: ( ) T X Eqmentioning

confidence: 99%

Stalled phase transition model of high-elastic polymer

Atrazhev

Burlatsky²,

Дмитриев

et al. 2013

J. Stat. Mech.

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The microscopic model of semi-crystalline polymer in high-elastic state is proposed. The model is based on the assumption that, below the melting temperature, the semi-crystalline polymer comprises crystal nuclei connected by stretched chain segments (SCS) with random configuration of monomers. The key factor that stalls the phase transition below the melting temperature is the tension of the SCS. External stress applied to the polymer also shifts the equilibrium and causes unfolding of the nuclei, which enables large reversible deformation of the polymer without loss of integrity. The simple 1D model predicts plateau in stress-strain curve of high-elastic polymer above the yield stress, which agrees with experimental observations. The model prediction for the temperature dependence of polytetrafluoroethylene (PTFE) yield stress in high-elastic state is in satisfactory agreement with experiment. KeywordsHigh-elastic state, Polymer deformation, Polymer yield stress IntroductionThe modeling of mechanical properties of solid polymers is important for multiple industrial applications. The popularity of polymer materials is caused by a large variability of their mechanical properties. For example, elastic modulus of solid polymers varies from several MPa for rubbers to several GPa for polyamides. Design of new polymers and polymer composite materials could be accelerated by the model, which relates the polymer structure and composition to the mechanical properties. The microscopic model of polymer mechanical properties also can be helpful for prediction of polymer components durability, e.g. durability of polymer membranes [1,2]. Polymers durability under mechanical cycling conditions is governed by kinetics of chain free radical reactions [3]. The kinetics of chain reactions in polymer systems depends on the microscopic structure of the polymer and microscopic stress distribution [3].

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

Cited by 47 publications

References 35 publications

Humidity and Temperature Cycling Effects on Cracks and Delaminations in PEMFCs

Humidity and Temperature Cycling Effects on Cracks and Delaminations in PEMFCs

Accelerated Degradation of High-Temperature Polymer Electrolyte Fuel Cells: Discussion and Empirical Modeling

Stalled phase transition model of high-elastic polymer

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