Membrane electrode assembly (MEA) serves as a central component in proton exchange membrane fuel cells. Reliability of the MEA is critical to ensure a proper functioning of the fuel cell. The objective of the present study is to develop a numerical model to predict the onset of MEA crack formation. Tensile tests have been conducted at different humidities and temperatures to determine the mechanical properties of MEA. The results of these experiments were combined to a finite element model to establish a failure criterion of MEA, both for direct and fatigue crack. The proposed criterion, based on dissipated energy, was shown to successfully predict the failure of the MEA in various environmental conditions.
The essential work of fracture (EWF) is a key property in understanding the fracture resistance in polymer membranes. As such, it is a promising approach when investigating the fracture resistance of proton exchange membrane in fuel cells. The longevity of these membranes is crucial to the good function of the cell: the membranes have to sustain important variations in the surrounding temperature and humidity, possibly affecting their fracture resistance. This study investigated the essential work of fracture of such proton exchange membranes using a double-edge notch tensile test (DENT test). The tests were performed for different environmental conditions that were relevant to the conditions met by proton exchange membrane fuel cells. The results of the DENT tests strongly depend on the temperature and humidity; in particular the high temperature cases show a large increase of dissipated energy. Based on experimental results, a numerical model was developed and the numerical simulations of DENT tests were performed. The obtained results suggest that the shape factor of plastic zone, β, should be a function of the ligament length and the quadratic regression is appropriate to the calculation of EWFs when the temperature is near the glass transition temperature. The EWFs under ambient temperature (30 °C) conditions were found to be 18.
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