Experimental evaluation of the clamping pressure distribution in a PEM fuel cell using matrix-based piezoresistive thin-film sensors

The achievement of a proper and uniform pressure distribution between the membrane electrode assembly (MEA) and the bipolar plates of a proton exchange membrane fuel cell (PEMFC) is a key factor of stack design and assembly. Contact pressure levels are usually controlled by selecting an appropriate external clamping pressure on the endplates. Very few studies have been focused on the measurement of the contact pressure distribution within the fuel cell and its correlation with the applied external clamping torque. This study explores the possibility of using matrix-based piezoresistive thin-film sensors, to be placed between the MEA and the monopolar plate of a PEMFC, to investigate this correlation. Before embedding the sensor array into the fuel cell, it was validated for accuracy and repeatability by designing a pneumatic calibration device which allows to apply uniform static pressure levels over the whole sensor area. Preliminary results reported in this study showed that, as the clamping torque on the endplates is increased, the average pressure on the MEA remains almost constant but its distribution changes. The core area of the electrode becomes progressively more unloaded while average stresses on the gasket rise up, with significant stress concentration around the edge corners.