Indentability of Conventional and Negative Poisson's Ratio Foams

The indentation resistance of foams, both of conventional structure and of a novel re-entrant structure giving rise to negative Poisson's ratio, was studied using holo graphic interferometry. In holographic indentation tests, re-entrant foams had higher yield strengths σ y and lower stiffness E than conventional foams of the same original relative density. Damage in both kinds of foam occurred primarily directly under the indenter. Calculated energy absorption for dynamic impact is considerably higher for re-entrant foam than conventional foam