Measurement of the clamping pressure distribution in polymer electrolyte fuel cells using piezoresistive sensor arrays and digital image correlation techniques

A combined method for the simultaneous measurement of the clamping pressure distribution and
endplates deformation in polymer electrolyte fuel cells (PEFC) is presented. The proposed approach,
which allows overcoming some important limitations associated with the use of conventional pre-scaled
pressure films, is used to investigate the correlation between the actual pressure distribution on the
membrane electrode assembly (MEA), the endplate out-of-plane deformation and the applied clamping
torque, for two single fuel cells assembled with either copper or aluminium/copper endplates. Results
proved that, in point-load design PEFCs, both pressure magnitude and distribution are affected by endplates
deformation and thickness mismatching between the sealing gasket and the MEA. Moreover, while
the average pressure on the MEA displays a slight increase (+25%) as the clamping torque is raised from
5 to 10 N m, it increases monotonically on the sealing gasket, with local peaks that exceed the saturation
level of the sensor array (20.7 MPa). A dimensionless uniformity index has been introduced to assess
the uniformity of the pressure distribution, allowing an easy comparison of different fuel cell assembly
configurations. The proposed methodology might assist the design of next-generation fuel cells or could
be used as a powerful validation tool for detailed finite element models. It can also be applied to study
other kind of fuel cells and batteries as well.