Foams as 3D perforated systems: An analysis of their Poisson's ratios under compression

Abstract

Using experimental data, it is shown that the Poisson's ratios of standard (untreated) open cell polyurethane foam vary when loading in different loading directions, since foam is inherently asymmetric and anisotropic. The loading direction which is in plane orthogonal to the rise direction of the foam constantly exhibited the most negative Poisson's ratio across foam samples of different types, even at moderate compressive strains. It was also shown that although the foam may become auxetic at very high values of compressive strain, it shows an incremental negative Poisson's ratio at moderate compressive strains. The results obtained are discussed in light of the deformation mechanisms, which have been proposed in literature to explain negative Poisson's ratios in foams. The effects of changing loading direction on the mechanical response of the foam are highlighted. An image of the symmetrical face of a foam cube, taken using a confocal microscope at 4× magnification.

On the Use of Auxetics in Footwear: Investigating the Effect of Padding and Padding Material on Forefoot Pressure in High Heels

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Composite patch with negative Poisson's ratio mimicking cardiac mechanical properties: Design, experiment and simulation

“…It is worth noting that while the structure could be conceptualized as consisting of ribs, the shear deformation of these ribs was relatively minor and could be disregarded. Therefore, the analysis primarily considered the axial and bending deformations of the ribs during the structural stress assessment [ 57 ].…”

Mechanics of Advanced Materials

“…According to this equation, the material is expected to become extremely tough, when its Poisson's ratio approaches −1. Consequently, many efforts have been made to analyse toughness of various artificial NPR materials, such as re-entrant foams and composite laminates [91,92,102,108,109], since they can be fabricated using different methods. For foams, the behaviour was studied by subjecting them to volumetric compression ratios under both compressive and tensile loadings [91,92].…”