Lightweight mechanical metamaterials designed using hierarchical truss elements

Luke Mizzi,Andrea Spaggiari

doi:10.1088/1361-665x/aba53c

Abstract

Rotating unit systems constitute one of the main classes of auxetic metamaterials. In this work, a new design procedure for lightweight auxetic systems based on this deformation mechanism is proposed through the implementation of a hierarchical triangular truss network in place of a full block of material for the rotating component of the system. Using numerical simulations in conjunction with experimental tests on 3D printed prototypes, the mechanical properties of six types of auxetic structures, which include a range of rotating polygons and chiral honeycombs, were analysed under the application of small tensile loads. The results obtained show that there is almost no difference in the Poisson’s ratios obtained from the regular, full structures and the ones made from triangular truss systems despite the latter, in some cases, being 80% lighter than the former. This indicates that these systems could be ideal candidates for implementation in applications requiring lightweight auxetic metamaterial systems such as in the aerospace industry.

Highlights

Mechanical metamaterials are systems whose mechanical properties are derived primarily from their structural framework and geometric design
The results obtained for the linear Finite Element simulations of each geometry as constructed with the four types of internal geometry shown in Figure 1 are presented followed by the experimental results
Four rotating unit systems corresponding to each of the four structure types investigated in the linear numerical study where fabricated using 3D stereolithography printing and subjected to a small tensile load in the y-direction

Summary

Introduction

Mechanical metamaterials are systems whose mechanical properties are derived primarily from their structural framework and geometric design. These systems have attracted a great deal of interest in the fields of material science and engineering due to their capability to exhibit a wide range of mechanical properties including unusual properties such as a negative Poisson’s ratio Ac. AUTHOR SUBMITTED MANUSCRIPT - SMS-110139.R1. One of the main classes of auxetic mechanical metamaterials is that of rotating unit systems. These metamaterials are typically made up of rigid or semi-rigid blocks of material which rotate relative to each other when the system is loaded. In its ideal form, the rotating square system has an isotropic

Results

Discussion

Conclusion