A novel mechanism for generating auxetic behaviour in reticulated foams: missing rib foam model Original Research Article

Foams have previously been fabricated with a negative Poissonʹs ratio (termed auxetic foams). A novel model is proposed to explain this and to describe the strain-dependent Poissonʹs function behaviour of honeycomb and foam materials. The model is two-dimensional and is based upon the observation of broken cell ribs in foams processed via the compression and heating technique usually employed to convert conventional foams to auxetic behaviour. The model has two forms: the “intact” form is a network of ribs with biaxial symmetry, and the “auxetic” form is a similar network but with a proportion of cell ribs removed. The model output is compared with that of an existing two-dimensional model and experimental data, and is found to be superior in predicting the Poissonʹs function and marginally better at predicting the stress–strain behaviour of the experimental data than the existing model, using realistic values for geometric parameters.