Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network

Open Access. Powered by Scholars. Published by Universities.®

PDF

Mechanical Engineering

Selected Works

PEM Fuel Cell Membranes

Publication Year

Articles 1 - 13 of 13

Full-Text Articles in Entire DC Network

Mechanics-Based Model For Non-Affine Swelling In Perfluorosulfonic Acid (Pfsa) Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson Jan 2013

Mechanics-Based Model For Non-Affine Swelling In Perfluorosulfonic Acid (Pfsa) Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson

Anette M Karlsson

A mechanics-based model is developed to predict the swelling pressure in perfluorosulfonic acid (PFSA) ionomer membranes during water uptake. The PFSA membrane is represented as a two-phase system, where the water-filled hydrophilic domains are dispersed throughout the hydrophobic polymer matrix. Two representative volume elements (RVEs) are used to represent the nanostructure: (i) a spherical RVE with a spherical hydrophilic domain at the center, and (ii) a cylindrical RVE with a cylindrical hydrophilic domain. The model starts with the non-affine swelling behavior of the membrane and interprets this as a structural reorganization of the RVEs to characterize the microscopic deformation. Swelling ...


Micromechanics Model Based On The Nanostructure Of Pfsa Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson, William B. Johnson, Simon Cleghorn Jan 2013

Micromechanics Model Based On The Nanostructure Of Pfsa Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson, William B. Johnson, Simon Cleghorn

Anette M Karlsson

A micromechanics model is developed to predict Young’s modulus of perfluorosulfonic acid (PFSA) membranes at various temperatures and water contents. The morphology of PFSA membranes is characterized by a two-phase structure, where hydrophilic clusters expand to hold water molecules during swelling, whereas the hydrophobic polymer network maintains the structural stability. A representative volume element (RVE) is proposed based on the descriptions for the nanostructure of PFSA membranes available in the literature. On the basis of mechanics model, we estimate Young’s modulus in tension of PFSA membranes as a function of water volume fraction for various temperatures. The results ...


Stresses In Proton Exchange Membranes Due To Hygro-Thermal Loading, Yaliang Tang, Michael H. Santare, Anette M. Karlsson, Simon Cleghorn, William B. Johnson Jan 2013

Stresses In Proton Exchange Membranes Due To Hygro-Thermal Loading, Yaliang Tang, Michael H. Santare, Anette M. Karlsson, Simon Cleghorn, William B. Johnson

Anette M Karlsson

Durability of the proton exchange membrane (PEM) is a major technical barrier to the commercial viability of polymer electrolyte membrane fuel cells (PEMFC) for stationary and transportation applications. In order to reach Department of Energy objectives for automotive PEMFCs, an operating design lifetime of at least 5000 h over a broad temperature range is required. Reaching these lifetimes is an extremely difficult technical challenge. Though good progress has been made in recent years, there are still issues that need to be addressed to assure successful, economically viable, long-term operation of PEM fuel cells. Fuel cell lifetime is currently limited by ...


Aspects Of Fatigue Failure Mechanisms In Polymer Fuel Cell Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson Jan 2013

Aspects Of Fatigue Failure Mechanisms In Polymer Fuel Cell Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson

Anette M Karlsson

The swelling-driven fatigue behavior of polymer fuel cell membranes during relative humidity (RH) cycling is investigated. In particular, swelling-induced membrane stresses are obtained from a numerical model simulating fuel cell RH cycle tests, and compared to the lifetimes obtained experimentally from tests conducted in the absence of electrochemical effects. A strong correlation between the lifetimes of the membranes in the actual tests and model results is obtained. In general, higher RH (or swelling) amplitude results in larger stress amplitudes and shorter lifetime, that is, fewer cycles to failure. Tensile stresses are needed for forming local cavities in the membrane, which ...


Stress-Strain Behavior Of Perfluorosulfonic Acid Membranes At Various Temperatures And Humidities: Experiments And Phenomenological Modeling, Ahmet Kusoglu, Yaliang Tang, Michael Santare, Anette M. Karlsson, Simon Cleghorn, William B. Johnson Jan 2013

Stress-Strain Behavior Of Perfluorosulfonic Acid Membranes At Various Temperatures And Humidities: Experiments And Phenomenological Modeling, Ahmet Kusoglu, Yaliang Tang, Michael Santare, Anette M. Karlsson, Simon Cleghorn, William B. Johnson

Anette M Karlsson

The constitutive response of perfluorinated sulfonic acid (PFSA) membranes based on tensile testing is investigated, and a phenomenological constitutive model for the elastoplastic flow behavior as a function of temperature and humidity is proposed. To this end, the G'Sell–Jonas (1979, “Determination of the Plastic Behavior of Solid Polymers at Constant True Strain Rate,” J. Mater. Sci., 14, pp. 583–591) constitutive model for semicrystalline polymers is extended by incorporating, in addition to temperature, relationships between the material constants of this model and the measured relative humidity. By matching the proposed constitutive model to the experimental stress-strain data, useful ...


Structure-Property Relationship In Ionomer Membranes, Ahmet Kusoglu, Anette M. Karlsson, Michael H. Santare Jan 2013

Structure-Property Relationship In Ionomer Membranes, Ahmet Kusoglu, Anette M. Karlsson, Michael H. Santare

Anette M Karlsson

Perfluorosulfonic acid (PFSA) ionomer membranes are ion-conducting polymers with high water sorption capacity and thermo-mechanical stability. The morphology of PFSA changes during sorption affecting the mechanical and physical properties of the membrane. In this work, we investigate the structure-property relationship in swollen PFSA membranes using three proposed nanostructural descriptions and determine Young's modulus of the membrane at a wide range of temperatures (−20–85°C) and water volume fractions (0–0.5) for these configurations. Comparing the mechanics-based models with experimental data we propose that ion-rich water domains in PFSA membrane are spherical at low water content, spherical with ...


Mechanical Properties Of A Reinforced Composite Polymer Electrolyte Membrane And Its Simulated Performance In Pem Fuel Cells, Yaliang Tang, Ahmet Kusoglu, Anette M. Karlsson, Michael H. Santare, Simon Cleghorn, William B. Johnson Nov 2012

Mechanical Properties Of A Reinforced Composite Polymer Electrolyte Membrane And Its Simulated Performance In Pem Fuel Cells, Yaliang Tang, Ahmet Kusoglu, Anette M. Karlsson, Michael H. Santare, Simon Cleghorn, William B. Johnson

Anette M Karlsson

The hygro-thermo-mechanical properties and response of a class of reinforced perfluorosulfonic acid membranes (PFSA), that has potential application as an electrolyte in polymer fuel cells, are investigated through both experimental and numerical modeling means. A critical set of material properties, including Young’s modulus, proportional limit stress, break stress and break strain, is determined for a range of temperature and humidity levels in a custom-built environmental test apparatus. The swelling strains are also determined as functions of temperature and humidity level. To elucidate the mechanical response and the potential effect these properties have on the mechanical durability, mechanics-based simulations are ...


Mechanical Response Of Fuel Cell Membranes Subjected To A Hygro-Thermal Cycle, Ahmet Kusoglu, Anette M. Karlsson, Michael H. Santare, Simon Cleghorn, William B. Johnson Nov 2012

Mechanical Response Of Fuel Cell Membranes Subjected To A Hygro-Thermal Cycle, Ahmet Kusoglu, Anette M. Karlsson, Michael H. Santare, Simon Cleghorn, William B. Johnson

Anette M Karlsson

The mechanical response of fuel cell proton exchange membranes subjected to a single hygro-thermal duty cycle in a fuel cell assembly is investigated through numerical means. To this end, the behavior of the membrane with temperature and humidity dependent material properties is simulated under temperature and humidity loading and unloading conditions. The stress-evolution during a simplified operating cycle is determined using finite element analysis for two clamping methods and two alignments of the bipolar plates. It is shown that compressive, plastic deformation occurs during the hygro-thermal loading, resulting in tensile residual stresses after unloading. These residual in-plane stresses in the ...


An Experimental Investigation Of Strain Rate, Temperature And Humidity Effects On The Mechanical Behavior Of A Perfluorosulfonic Acid Membrane, Zongwen Lu, Melissa Lugo, Michael H. Santare, Anette M. Karlsson, F. Colin Busby, Peter Walsh Nov 2012

An Experimental Investigation Of Strain Rate, Temperature And Humidity Effects On The Mechanical Behavior Of A Perfluorosulfonic Acid Membrane, Zongwen Lu, Melissa Lugo, Michael H. Santare, Anette M. Karlsson, F. Colin Busby, Peter Walsh

Anette M Karlsson

The time-dependent hygro-thermal mechanical behavior of a perfluorosulfonic acid (PFSA) membrane (Nafion® 211 membrane) commonly used in Proton Exchange Membrane Fuel Cells (PEMFCs) is investigated at selected strain rates for a broad range of temperatures and humidities. Tensile tests and relaxation tests are conducted to determine Young’s modulus and proportional limit stress as functions of strain rate, temperature and humidity. The results show that Young’s modulus and proportional limit stress increase as the strain rate increases, and decrease as the temperature or humidity increases. The results also show that the mechanical response of Nafion® 211 membrane is more ...


Constitutive Response And Mechanical Properties Of Pfsa Membranes In Liquid Water, Ahmet Kusoglu, Yaliang Tang, Melissa Lugo, Anette M. Karlsson, Michael H. Santare, Simon Cleghorn, William B. Johnson Nov 2012

Constitutive Response And Mechanical Properties Of Pfsa Membranes In Liquid Water, Ahmet Kusoglu, Yaliang Tang, Melissa Lugo, Anette M. Karlsson, Michael H. Santare, Simon Cleghorn, William B. Johnson

Anette M Karlsson

The mechanical properties and swelling behavior of perfluorosulfonic acid (PFSA) membranes in liquid water have been investigated using a custom-built, temperature-controlled water bath. Interestingly, the theoretical models of Mooney-Rivlin and Ogden for rubber elasticity are shown to reproduce the major features of the experimentally obtained stress-strain relationships. In addition, stress relaxation of the membrane subjected to a fixed strain at room temperature fits time-dependent constitutive models used to describe nonlinear rubber elasticity. Thus, the experimental results suggest that even though PFSA is not an elastomer, the constitutive models developed for rubber-like behavior can be used for describing the ex situ ...


Numerical Investigation Of Mechanical Durability In Polymer Electrolyte Membrane Fuel Cells, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson, Simon Cleghorn, William B. Johnson Nov 2012

Numerical Investigation Of Mechanical Durability In Polymer Electrolyte Membrane Fuel Cells, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson, Simon Cleghorn, William B. Johnson

Anette M Karlsson

The relationship between the mechanical behavior and water transport in the membrane electrode assembly (MEA) is numerically investigated. Swelling plays a key role in the mechanical response of the MEA during fuel cell operation because swelling can be directly linked to the development of stresses. Thus, in the model introduced here, the stresses and the water distribution are coupled. Two membranes are studied: unreinforced perfluorosulfonic acid (PFSA) and an experimental reinforced composite membrane. The results suggest that open-circuit voltage operations lead to a uniform distribution of stresses and plastic deformation, whereas under current-load operation, the stresses and the plastic deformation ...


Effect Of Time-Dependent Material Properties On The Mechanical Behavior Of Pfsa Membranes Subjected To Humidity Cycling, Narinder S. Khattra, Anette M. Karlsson, Michael H. Santare, Peter Walsh, F. Colin Busby Nov 2012

Effect Of Time-Dependent Material Properties On The Mechanical Behavior Of Pfsa Membranes Subjected To Humidity Cycling, Narinder S. Khattra, Anette M. Karlsson, Michael H. Santare, Peter Walsh, F. Colin Busby

Anette M Karlsson

A viscoelastic-plastic constitutive model is developed to characterize the time-dependent mechanical response of perfluorosulphonic acid (PFSA) membranes. This model is then used in finite element simulations of a representative fuel cell unit, (consisting of electrodes, gas diffusion layer and bipolar plates) subjected to standardized relative humidity (RH) cycling test conditions. The effects of hold times at constant RH, the feed rate of humidified air and sorption rate of water into the membrane on the stress response are investigated. While the longer hold times at high and low humidity lead to considerable redistribution of the stresses, the lower feed and sorption ...


Mechanical Behavior Of Fuel Cell Membranes Under Humidity Cycles And Effect Of Swelling Anisotropy On The Fatigue Stresses, Ahmet Kusoglu, Anette M. Karlsson, Michael H. Santare, Simon Cleghorn, William B. Johnson Nov 2012

Mechanical Behavior Of Fuel Cell Membranes Under Humidity Cycles And Effect Of Swelling Anisotropy On The Fatigue Stresses, Ahmet Kusoglu, Anette M. Karlsson, Michael H. Santare, Simon Cleghorn, William B. Johnson

Anette M Karlsson

The mechanical response of proton exchange membranes in a fuel cell assembly is investigated under humidity cycles at a constant temperature (85°C). The behavior of the membrane under hydration–dehydration cycles is simulated by imposing a humidity gradient from the cathode to the anode. Linear elastic, plastic constitutive behavior with isotropic hardening and temperature and humidity dependent material properties are utilized in the simulations for the membrane. The evolution of the stresses and plastic deformation during the humidity cycles are determined using finite element analysis for two clamping methods and various levels of swelling anisotropy. The membrane response strongly ...