Partially Auxetic Properties of Face‐Centered Cubic Hard‐Sphere Crystals with Nanochannels of Different Sizes, Parallel to [001]‐Direction and Filled by Other Hard Spheres

Abstract

Results of constant pressure and temperature Monte Carlo (MC) simulations with varying shapes of the periodic box are presented for face‐centered cubic (FCC) hard‐sphere crystals with periodic inclusions––arrays of channels parallel to the [001] crystalline axis and forming a square lattice with [100] and [010] axes in the (001) plane. The channels, referred to as nanochannels because their diameters do not exceed a few lattice constants of the matrix crystal, are filled by hard spheres of slightly different diameters from the spheres forming the matrix crystal. Fourteen types of nanochannels with different sizes, formed by the spheres lying on the nanochannel axis and up to those being their thirteenth nearest neighbor, are simulated. The nanochannel axes are distanced by six lattice constants of the monoatomic FCC crystal and arranged in a square lattice with main axes parallel to one of the main axes of the FCC lattice, formed by identical spheres. It is shown that small differences in: 1) channel sizes, 2) their geometry; and 3) diameter ratios of inclusion to matrix spheres can lead to large differences in the elastic properties of the studied nanocomposite structures. This is well seen in the minimum and maximum values of Poisson's ratio.

An Auxetic Metamaterial Based on Rotating and Nonrotating Rigid Units Inspired by an Aztec Geometric Pattern

“…[22][23][24] Of late, a number of reports on new auxetic geometries have been made by inspiration from historical, cultural, and religious sources, such as Islamic geometric patterns [25][26][27] and the Maltese cross. [28,29] As an extension to auxetic systems related to rotating units, [14][15][16][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] this article introduces an auxetic metamaterial based on a combination of rotating and nonrotating rigid units. Specifically, this metamaterial consists of rotating triangles and nonrotating rhombi, by inspiration from an Aztec design.…”

Variable Dual Auxeticity of the Hierarchical Mechanical Metamaterial Composed of Re‐Entrant Structural Motifs

“…Mechanical metamaterials [1,2,3,4,5,6,7,8,9,10,11,12,13] are rationally-designed structures capable of exhibiting a plethora of atypical mechanical properties that are rarely observed in the case of naturally-occurring materials. Some of the most commonly studied of such properties are negative Poisson's ratio [14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29] (auxetic behaviour), negative stiffness [30,31,32,33,34] and negative compressibility [35,36]. Over the last thirty years, it has been demonstrated that devices utilising materials exhibiting such characteristics can be used in the case of a variety of applications including protective devices [37,38], sports equipment [39] as well as biomedical [40,41] and vibration damping devices [42,43,44].…”

Investigating the Effect of Relative Humidity on the Mechanics and Dynamics of Open‐Cell Polyurethane Auxetic Foams

“…During the past four decades, auxetics (i.e., negative Poisson's ratio (NPR)) materials and structures have been developed in different forms and scales, from molecular assemblies and nanostructures, [ 1–8 ] metals systems, [ 9–11 ] and lattices/perforations [ 12–17 ] to multiphase composites. [ 18–22 ] The reader is referred to the works of Alderson and Evans, [ 23 ] Lakes, [ 24,25 ] and Lim [ 26,27 ] for an extensive review of morphologies and performances of auxetic materials systems.…”

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During the past four decades, auxetics (i.e., negative Poisson's ratio (NPR)) materials and structures have been developed in different forms and scales, from molecular assemblies and nanostructures, [1][2][3][4][5][6][7][8] metals systems, [9][10][11] and lattices/ perforations [12][13][14][15][16][17] to multiphase composites. [18][19][20][21][22] The reader is referred to the works of Alderson and Evans, [23] Lakes, [24,25] and Lim [26,27] for an extensive review of morphologies and performances of auxetic materials systems.Foams (both open and closed cells) are arguably one of the first and most successful materials products with auxetic characteristics, being described for the first time in Lakes' seminal article of 1987.

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