On damage evolution of PEM electrodes

Date
2010
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Publisher
University of Delaware
Abstract
One of the main challenges that the polymer electrolyte membrane (PEM) fuel cell industry faces is the improvement of the durability of its fuel cells. PEMFCs are required to last for long periods of time and in order to achieve this demand, it is necessary to better understand and improve the durability of the membrane electrode assembly (MEA), which is a critical component of a PEM fuel cell. To address this issue, the failure evolution and the mechanical properties of PEM electrodes are investigated through experimental and numerical work. From an experimental point of view, the failure evolution of PEM electrodes is examined by conducting strain controlled interrupted tests. The evolution of distinct defects, such as cracks, on the surface of the electrodes is then analyzed by using scanning electron microscope. It is very important to consider the evolution of cracks observed on the electrodes, in order to capture the mechanical response of the MEA. The mechanical behavior of the MEA is obtained by conducting tensile tests at various temperature and humidity conditions. After obtaining experimental data, finite element simulations are performed by using the software ABAQUS, where the mechanical properties of "membrane A" and the electrodes are used as input. Reverse analysis is used in order to establish the mechanical properties of the electrodes that lead to the experimentally measured response of the MEA. Different cases are investigated numerically including the influence of plasticity in the electrodes, crack density, crack length, and interfacial delamination. The numerical results are compared with the experimental results from the MEA. The results indicate that crack density has a profound effect on the mechanical behavior of the MEA and it dominates over other factors such as the mechanical properties of the electrodes and the length of delamination. The combination of experimental and numerical work resulted in a powerful approach to determine the mechanical properties of PEM electrodes. In addition, it contributed to better understand the different factors that affect the mechanical degradation of MEAs and PEM electrodes, and consequently the durability of PEMFCs.
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