A constitutive law to predict the compression of gas diffusion layers

Abstract

The mechanical behavior of gas diffusion layers (GDLs) is predicted via existing models developed for fibrous materials. For this purpose, a new representation of the behavior is required, function of the material relative density rather than the classical mechanical strain. This allows to shed light on the evolution of the GDLs mechanical properties according to the different levels of mechanical stresses encountered during its lifetime. Compression tests are performed in order to differentiate the experimental mechanical properties of two types of GDLs. Different levels of mechanical stress are applied on the samples to simulate a mechanical history similar to the one encountered in real use. Two different behaviors are observed; the compression is at first governed by the mechanical history of the samples before recovering the GDL original behavior. Accordingly, two sets of parameters are required to fit these different behaviors. The GDLs mechanical properties can be then predicted regardless of the samples state, i.e. pristine or used. Excellent correlations are found between predicted and experimental data. This model brings a better understanding of the mechanisms implied during the GDL compression which plays a major role in the performance of proton exchange membrane fuel cells.