A novel mechanism for generating auxetic behaviour in reticulated foams: Missing rib foam model

Foams have previously been fabricated with a negative Poisson's ratio (term ed auxetic foams). A novel model is proposed to explain this and to describ e the strain-dependent Poisson's function behaviour of honeycomb and foam m aterials. The model is two-dimensional and is based upon the observation of broken cell ribs in foams processed via the compression and heating techni que usually employed to convert conventional foams to auxetic behaviour. Th e 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 existin g two-dimensional model and experimental data, and is found to be superior in predicting the Poisson's function and marginally better at predicting th e stress-strain behaviour of the experimental data than the existing model, using realistic values for geometric parameters. (C) 2000 Acta Metallurgic a Inc. Published by Elsevier Science Ltd All rights reserved.