This work focuses on the mechanical modeling of open-cell foams, treated as advanced multifunctional materials characterized by large deformations, pore collapse, and densification. Such materials cannot be adequately described by standard solid models, since their macroscopic response arises from the interaction between a deformable solid skeleton and the pore space.\\ A finite-strain elasto-plastic constitutive model is developed within a porous-media framework, in which the foam is represented as a homogenized continuum accounting for a solid skeleton and a void space. The macroscopic description is obtained through a volume fraction approach, allowing porosity effects and evolution to be incorporated into the mechanical response. For open-cell foams, the overall behavior is governed by the deformation of the solid skeleton, while the role of the pore phase is implicitly captured through the evolving microstructure.\\ The macroscopic compressive behaviour typically exhibits an initial quasi-elastic regime, followed by a stress plateau associated with progressive pore collapse and a final densification stage. To capture this nonlinear and pressure-sensitive response, the solid skeleton is modeled using a single-surface elasto-plastic formulation of Ehlers type, expressed in terms of stress invariants. The yield function combines deviatoric, pressure-dependent, and third-invariant effects, while a non-associative flow rule controls volumetric plastic deformation. Structural hardening is introduced through porosity-dependent parameters, enabling a unified description of collapse and densification.\\ The model is formulated at finite strains and implemented in a finite element framework. The formulation is applied to porous transport layers used in proton exchange membrane electrolytic cells, where open-cell porous materials are employed to provide both mechanical support and transport functionality. Assembly-induced compressive loads can lead to localized stresses, partial pore collapse, and permanent deformation, with direct implications for transport properties and durability. Numerical simulations under representative compression conditions reveal localized deformation and plastic strain beneath the bipolar plate ribs, highlighting the relevance of pressure-sensitive plasticity for design and analysis.