Modelling the creep of open-cell polymer foams

摘要

The high-strain creep of open-cell low-density polymer foams is analysed using linear vis- coelasticity theory. The microstructure is represented by the Kelvin foam, a regular lattice of tetrakaidecahedral cells. Compressive creep curves are predicted from the measured stress relaxation modulus of a polyurethane (PU) and the foam density. Geometric non-linearity develops as some cell edges become S-shaped, causing the creep rate to increase. The low-strain creep response can be predicted accurately. The response for strains between l0 and 50/100 is qualitatively correct, but the Kelvin foam, if it maintains its initial symmetry when compressed in the [00l] lattice direction, has less geometric non-linearity than the irregular PU foam. A buckling mode is proposed which would cause increased geometric non-linearity. Polymer non- linearity also contributes to the medium strain creep response of some low-density PU foams.