The effect of porosity on elastic moduli of polymer foams

Constitutive equations are reported for the effect of porosity on the elastic moduli and longitudinal sound speed of polymer foams. These relations are grounded on the asymptotic homogenization method combined with the integration embedding scheme. Observations are analyzed on open-cell and closed-cell porous polymers manufactured by (1) foaming with chemical blowing agents, (2) foaming with inert gases, and (3) emulsion-templating foaming. Numerical analysis of experimental data shows that changes in the elastic moduli with porosity are correctly predicted by the governing relations for foams with spherical voids. Porous polydimethylsiloxane (PDMS) elastomers prepared by the emulsion-templating method provide an exception from this rule. The difference between these materials and the other cellular polymers is caused by production of hydrogen gas under curing, which induces severe deformation of pores. Simulation reveals that experimental data on cellular PDMS elastomers are described by the differential equations for foams with spheroidal voids whose aspect ratio depends on porosity. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48449.