AUXETIC FOAMS - MODELING NEGATIVE POISSONS RATIOS

A finite element model for three-dimensional, open-celled foams is dev eloped. A reentrant cell shape is defined that has the unusual propert y of exhibiting a negative Poisson's ratio. By altering the cell shape it is possible to achieve different values for the elastic constants and different degrees of anisotropy. It is shown that simple two-dimen sional approximations fail to model the properties of the three-dimens ional network accurately and a full three-dimensional analysis is requ ired. The reentrant cell used is fully auxetic, with negative Poisson' s ratios exhibited when loaded in all three orthogonal directions.