Dynamic response of auxetic structures

Matthieu Proffit,John Kennedy

doi:10.21595/vp.2020.21440

Abstract

Auxetic materials have been investigated since the 1990’s, they are defined by a negative Poisson’s ratio which gives them interesting capabilities in energy and shock absorption. They are usually lattice structures (2D or 3D array of unit cells), which gives them high stiffness to weight properties and their properties can be tuned to suit a given application. Several papers have been published on new auxetic designs, their static equivalent mechanical properties, shock absorption properties and their manufacturing. Their dynamic behavior has not been studied to date and this is the main purpose of this paper. We will present a novel design that facilitates 3D printing with SLA printers and then examine the dynamic behavior of an auxetic structure between 0 and 1 kHz. In order to explain the unusual behavior of the structure, an initial theoretical model of non-linear spring has been developed with partial success.

Highlights

Auxetic materials are materials that have a negative Poisson’s ratio, they almost not be found in nature and their behavior emerges from their macro-structure
A novel structure has been developed with success, it enables 3D printing with SLA printers and has mechanical properties comparable to previously developed structures
When we vary the mass attached to the free end of the sample, the change in resonance frequency is not explained by a linear spring model

Summary

Introduction

Auxetic materials are materials that have a negative Poisson’s ratio (they contract or expand in any spatial direction when exposed to a stress), they almost not be found in nature and their behavior emerges from their macro-structure. On a microscopic point of view, they are made from a bulk material of positive Poisson’s ratio. They have been studied since the late 1980s [1] for their good properties in shock absorption, fracture toughness, indentation resistance and energy dissipation. The geometry presented in this paper is the hexagonal re-entrant structure, one of the most commonly studied [2,3,4,5,6,7] as it can be defined with very few parameters unlike other more complex structures. The advantage of powder bed fusion methods is that the powder supports the structure as it is printed

Results

Discussion

Conclusion