Modeling the creep of open-cell polymer foams

The high-strain creep of open-cell low-density polymer foams is analysed using linearviscoelasticity theory. The microstructure is represented by the Kelvin foam, a regular lattice oftetrakaidecahedral cells. Compressive creep curves are predicted from the measured stressrelaxation modulus of a polyurethane (PU) and the foam density. Geometric non-linearitydevelops as some cell edges become S-shaped, causing the creep rate to increase. The low-straincreep response can be predicted accurately. The response for strains between 10 and 50% isqualitatively correct, but the Kelvin foam, if it maintains its initial symmetry when compressedin the [001] lattice direction, has less geometric non-linearity than the irregular PU foam. Abuckling mode is proposed which would cause increased geometric non-linearity. Polymernon-linearity also contributes to the medium strain creep response of some low-density PUfoams