Compression‐Induced Mechanical Pore Opening in Microcellular Polyurethane Elastomers: Decoupling Open Porosity Effects From Matrix Contributions

ABSTRACT This study presents a stress‐induced pore rupture strategy for decoupling cellular architecture from matrix properties in microcellular polyurethane elastomers. Controlled mechanical compression was applied to a single formulation to tune open porosity (14%–67%) while preserving matrix chemistry and nanoscale morphology, as verified by FTIR, XRD, and SAXS analysis. In situ CT imaging revealed distinct deformation mechanisms: closed‐cell structures deformed through gradual pore compression dominated by gas‐spring effects, whereas open‐cell networks exhibited immediate strut reorientation and extensive compaction governed by solid matrix deformation. Quantitative analysis showed that cellular deformation accounted for 81.2%–86.8% of total strain in open‐cell foams, compared with 69.2%–74.1% in closed‐cell systems. Increasing open porosity reduced stiffness by 27% but enhanced energy dissipation by 63%. Digital image correlation further demonstrated localized strain in closed‐cell foams and uniform stress redistribution in open‐cell architectures. Vibration testing revealed complementary performance, with high‐porosity foams suppressing resonance through viscous damping and low‐porosity foams providing superior high‐frequency isolation. This work establishes microstructure‐guided design principles for programming dynamic mechanical properties in polymer foams, offering a pathway toward lightweight material for vibration control and impact protection.