Design and study of novel Nested auxetic lattices with tunable and enhanced in-plane elastic properties

Abstract

Auxetic lattices are interesting engineering materials due to Negative Poisson’s Ratio (NPR). However, auxetic lattices usually have extremely low stiffness and exhibit high anisotropy (E1/E2 >>1), severely limiting their application in high-loading environments. Attempts at increasing the stiffness of lattices typically lead to a decrease in auxeticity and an increase in anisotropy. In the current study, using novel nesting strategies, modified Sinusoidal Re-entrant Honeycomb (SRH) microstructures are developed to enhance stiffness, retain the auxeticity and introduce nearly isotropic characteristics (E1/E2 ∼ 1). Different Nested n-type (n = 0, 1,2, 3 and 4) microstructures have been studied. Translation studies involving 90° and 0° oriented lattices are undertaken to find the effect of these nesting along different lengths and combinations leading to enhanced stiffness with minor loss in auxeticity. The possibility of attaining a stiffness at least 1500 % greater than the empty lattices, while retaining significant auxeticity (Poisson’s ratio < -1) has been showcased. The proposed approach can also lead to the development of lattices that exhibit nearly isotropic characteristics. The proposed approach can be realized using the state-of-art capabilities of modern 3D printers. The proposed methods and modifications are simple yet very substantial in terms of property enhancement and can be extended to almost all types of lattices.