Mixed auxeticity of auxetic sandwich structures

Abstract

Previously, a sandwich structure in which the Poisson ratios of the core and facesheets possess opposite signs has been shown to exhibit overall conventional and auxetic behavior depending on the loading mode – axial loading or bending – for an intermediate range of relative core thickness. In addition to these two loading modes, sandwich structures in aerospace applications encounter torsional loads. In this paper, the effective Poisson's ratio for torsional loading is proposed. Results show that, depending on the loading mode and the relative core thickness, there can be up to four levels of overall auxeticity, namely (i) full auxeticity (FA) if the structure behaves as an auxetic structure under all three modes of loading, (ii) high auxeticity (HA) if the structure behaves as an auxetic structure in two of the loading modes, (iii) low auxeticity (LA) if the structure behaves as an auxetic structure in only one of the loading modes, and (iv) no auxeticity (NA) if the structure behaves as a conventional structure under all of the three loading modes. These results indicate that by selecting the Poisson's ratios and the thickness of the cores and facesheets, the sandwich structure can be made to respond differently under different external loading conditions.

Effect of longitudinal stress on wave propagation in width‐constrained elastic plates with arbitrary Poisson's ratio

“…The study of auxetic materials is of interest due to their unique properties in comparison to conventional ones [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45], especially for auxetic plates under both static and dynamic conditions [3,10,[12][13][14][46][47][48][49][50][51][52][53][54][55][56][57][58]. In this paper, we investigate the wave velocity of low-amplitude, i.e., harmonic, longitudinal waves in a plate made of an isotropic ideally elastic material under a static uniaxial stress applied so that its axis is parallel to the propagation vector.…”

Composite chiral shear vibration damper

“…Chiral structures are a subset of auxetics (negative Poisson's ratio materials and structures) [11][12][13][14]. Chiral structures provide non-affine deformations coupling in-plane rotations with uniaxial loading, and therefore generate the negative Poisson's ratio behaviour [15,16].…”

Torsion of a Two‐Phased Composite Bar With Helical Distribution of Constituents

“…Recent works concerning the torsional behavior of auxetic composites were presented by Lim and Strek . Chen and Lakes investigated the dynamical behavior of conventional and negative Poisson's ratio foamed materials in torsional vibration. Lazarus and Reis presented the work concerning bending, torsion and axial compression of auxetic cylinders.…”