Design and mechanical characterization of periodic metamaterials with interconnected spherical voids

Abstract

This work explores the benefits of a newly proposed arrangement of spherical cavities that creates a nearly isotropic, lightweight and strong metamaterial, which can be easily exploited for structural applications and can also be used as an infill for additively manufactured structures. Additive manufacturing uses lattice, plate, and minimal surface designs to enhance efficiency and reduce waste, costs, and processing time. This work systematically analyses regular arrangements of spherical interconnecting voids with the aim of finding the most suitable configuration that reduces weight retaining the stiffness and strength of the base material. Three main arrangements were considered: a simple cubic lattice (CS), a body centered cubic lattice (BCC) and a face centered cubic lattice (FCC). The sphere dimension is varied between its limits and through extensive finite element analyses the main normalized properties of the structure, such as the elastic modulus, Poisson’s ratio and shear modulus were retrieved and compared as a function of the relative density. The results are optimal in terms of stiffness and strength of the material compared to the density of the structure, mainly because of the absence of sharp corners and notches inside the lattice. Among the investigated architectures, BCC provided the best overall balance of normalized stiffness, compressive strength, and near-isotropic response. The numerical results were validated against experimental tests on 3D printed structures and the validity of the adopted approach was confirmed. In addition, experimental tests show the feasibility of these structures as possible infill for additively manufactured parts with superior properties compared to the most common isotropic infill.