  Water management is a key factor that limits PEFC's performance. We show how
insights into this problem can be gained from pore-scale simulations of water
invasion in a model fibrous medium. We explore the influence of contact angle
on the water invasion pattern and water saturation at breakthrough and show
that a dramatic change in the invasion pattern, from fractal to compact, occurs
as the system changes from hydrophobic to hydrophilic. Then, we explore the
case of a system of mixed wettability, i.e. containing both hydrophilic and
hydrophobic pores. The saturation at breakthrough is studied as a function of
the fraction of hydrophilic pores. The results are discussed in relation with
the water management problem, the optimal design of a GDL and the fuel cell
performance degradation mechanisms. We outline how the study could be extended
to 3D systems, notably from binarised images of GDLs obtained by X ray
microtomography.
