Thermomechanical characterisation of commercial Gas Diffusion Layers of a Proton Exchange Membrane Fuel Cell for high compressive pre-loads under dynamic excitation

Abstract

A Proton Exchange Membrane Fuel Cell (PEMFC) is a mechanically constrained stack composed of several heterogeneous elements. The internal mechanical stress and the mechanical heterogeneity strongly influence the overall PEMFC performances and have to be known and mastered. One of the core components of the PEMFCs is the Gas Diffusion Layer (GDL). In general, this element is composed of non-woven carbon fibre paper or woven carbon cloth. Consequently, the mechanical properties necessary to develop an optimal fuel cell are complicated to extract. Moreover, the mechanical properties of the GDL, and in particular the compression modulus, have to be accurately characterised with respect to various excitation types related to the transportation applications. Consequently, it is essential to investigate, from experiments, the compression modulus of the GDL with respect to large static loads, dynamic loads, different excitation frequencies and temperature. The objective of this paper is to provide the results measured for three widely used commercial GDLs (SGL 24 AA, SGL 24 BA and SGL 24 BC) using an experimental characterisation method with high compressive pre-loads under dynamic excitation over a large temperature range. The experiments show that the stabilisation of the non-linear mechanical behaviour occurs after five loading/unloading cycles. The static pre-loads highly influence the dynamic compression modulus. However, the level of the excitation frequency does not appear to modify the mechanical behaviour. Temperature seems to linearly influence the dynamic compression modulus in two different temperature domains.