An Isotropic Auxetic Structural Network With Limited Shear Stiffness

Abstract

The chiral lattice is a unique structural network not symmetric to its mirror image, and with a negative Poisson's ratio. Previous investigations have considered this structural network for the design of superior structural components with sandwich construction, but these were limited by the in-plane Poisson's ratio predicted to be exactly −1. This paper presents estimates of the mechanical properties of the chiral lattice obtained from a multi-cell finite-element model. It is shown that the chiral lattice has a shear stiffness bound by that of the triangular lattice and it is very compliant to direct stresses. The minimum in-plane poisson's ratio is estimated to be ≈ −0.94. INTRODUCTIONCellular solids possess superior mechanical properties [1] that can be exploited for the development of novel structured materials. Their wide-spread employment in the aerospace, automotive, and naval industries, among others, is to be attributed primarily to unique physical properties: low relative density, low electrical conductivity, low Young's modulus and strength [1]. Low density facilitates the design components with high specific (mass-normalized) stiffness, and provides effective thermal insulation [1,2]. The latter is to be attributed to the low conductivity of the second phase, most often a gas. Low density is also ideal for naval applications where buoyancy and specific stiffness are required [1]. Low strength is very advantageous in applications where mechanical-energy absorption is paramount. This may be

Auxetic Lattice Structures for Turbomachinery Application – a Simulative Parameter Study

“…Spadoni [15] describes the ratio of the length of the struts "𝐿" to the distance between the node centres "𝑅" as the determining geometry parameter for the auxetic effect. This relationship is shown in Figure 5.…”

“…For a ratio of 𝐿 / 𝑅 = 0.985 the Poisson's ratio reaches a minimum of 𝜈 = −0.94. [15] Figure 5. Chiral auxetic structures: [15]…”