Auxeticity of Concentric Auxetic-Conventional Foam Rods with High Modulus Interface Adhesive

Abstract

While the rule of mixture is applicable for addressing the overall Poisson’s ratio of a concentrically aligned bi-layered rod under longitudinal loading, the same cannot be said for this rod under torsional loading due to the higher extent of deformation in the rod material further away from the torsional axis. In addition, the use of adhesives for attaching the solid inner rod to the hollow outer rod introduces an intermediate layer, thereby resulting in a tri-layered concentric rod if the adhesive layer is uniformly distributed. This paper investigates the effect of the adhesive properties on the overall auxeticity of a rod consisting of two concentrically aligned cylindrical isotropic foams with Poisson’s ratio of opposite signs under torsional loads. An indirect way for obtaining Poisson’s ratio of a concentrically tri-layered rod was obtained using a mechanics of materials approach. Results show that the auxeticity of such rods is influenced by the adhesive’s stiffness, Poisson’s ratio, thickness, and radius from the torsional axis.

An Anisotropic Auxetic 2D Metamaterial Based on Sliding Microstructural Mechanism

“…The extent of anisotropy increases when the array goes to the extremes, thereby leading to extreme negative Poisson’s ratios. The results from this paper, in conjunction with earlier works on auxetic beams [40,41], auxetic rods [42,43,44], auxetic plates [45,46,47,48,49,50,51,52], auxetic shells [53,54], auxetic composites [55,56,57,58,59,60,61,62] and 2D metamaterial structures [63,64], would avail more design options for the engineer in developing novel load bearing materials and structures.…”

Controllable Hierarchical Mechanical Metamaterials Guided by the Hinge Design

“…Mechanical metamaterials [ 1 , 2 , 3 ] are a class of rationally-designed systems that can exhibit counter-intuitive mechanical properties based on their design rather than material’s composition. Over the years, these systems have been thoroughly analysed from the point of view of their potential to exhibit unusual mechanical properties such as auxetic behaviour [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ], negative compressibility [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ] and negative stiffness [ 21 , 22 , 23 , 24 , 25 , 26 ]. This large and continuously growing interest of the research community in the mechanical metamaterials stems from the fact that their unusual mechanical properties can be utilised in numerous applications ranging from biomedical [ 27 ] to soundproofing [ 28 , 29 ] and protective devices [ 30 , 31 , 32 , 33 ].…”

The Multidirectional Auxeticity and Negative Linear Compressibility of a 3D Mechanical Metamaterial

“…This versatility of mechanical metamaterials is possible due to a number of different counter-intuitive mechanical properties that they can exhibit depending on the manner in which they are designed. It seems that the most pursued of such mechanical properties is the negative Poisson's ratio (auxetic behaviour) [7,[14][15][16][17][18][19][20][21][22][23] which characterises bodies that can expand laterally when uniaxially stretched and conversely contract laterally when uniaxially compressed. Some of the other highly-desired, unusual mechanical properties are negative stiffness [24][25][26][27][28], negative compressibility [29][30][31][32][33][34][35] and negative thermal expansion [36,37].…”