The effects of gas diffusion layer s (GDL s) anisotropic bending stiffness on the electro chemical performances of polymer electrolyte membrane fuel cells have been investigated for carbon fiber felt and paper GDLs The bending stiffness values of all GDLs in the machine direction are higher than those in the cross machine direction We have prepared GDL sheet samples such that the machine direction of GDL roll is aligned with the major flow field direction of a metallic bipolar plate at angles of 0 (parallel '0 GDL) and 90 (perpendicular '90 GDL) The I-V performances of all the 5 cell stacks with 90 GDLs are higher than those with 0 degrees GDLs All the 5 cell stacks with 90 degrees GDLs show lower values of high frequency resistance (HFR) than those with 0 degrees GDLs However, the gas pressure differences at both anode and cathode of 5 cell stacks with 90 degrees GDLs appear to be similar to or slightly lower than those with 0 GDLs making the lower HFR as a dominant factor for the improved I-V performances This may result from the reduced intrusion of 90 GDLs into gas channels than 0 degrees GDLs as observed by less thickness reduction under compression of 90 degrees GDLs A 45 degrees GDL (skew alignment) also shows better performances than the 0 degrees GDL (C) 2010 Professor T Nejat veziroglu Published by Elsevier Ltd All rights reserved