A Multiphysics Equivalent Stiffness Model for PEMFC Stacks: Design of Experiments Screening of Assembly and Operating Factors

The performance of a Proton Exchange Membrane Fuel Cell (PEMFC) stack is largely determined during assembly, where component materials, sealant selection, and clamping force jointly influence both sealing effectiveness and interfacial losses. These factors interact through coupled mechanical, thermal, and electrical phenomena. Although detailed multiphysics models can accurately capture these effects, their high computational cost limits their application in parametric analyses and optimisation studies. The Equivalent Stiffness Model (ESM) provides an efficient alternative, representing each stack component as a simplified stiffness formulation. Starting from an earlier ESM that reproduces the nonlinear compression of the Membrane Electrode Assembly (MEA) and sealants, this work adds the calculation of the electrical contact resistance at the Gas Diffusion Layer (GDL)–Bipolar Plate (BPP) interface and the resulting GDL porosity. Given the large number of input parameters, a Design of Experiments (DoE) approach systematically explores a wide range of stack configurations and operating conditions. The analysis shows that GDL type, sealant properties, and clamping force are the main drivers of assembly-related performance, whereas BPP material and thermo-hygrometric conditions become more influential during operation. These results provide quantitative guidance on which design and operating choices most strongly affect stack behaviour and under which conditions.