Elastodyanmic Properties of Architected Metamaterials

While architected metamaterials have been well studied for their quasi-static properties, their elastodynamic properties have been largely unexplored. In this talk, I will give an overview of our recent theoretical and experimental works pertaining to how architected metamaterials interact with vibration. I will first introduce a class of metamaterials that achieve low-frequency band gaps with a volume fraction as low as 3% (mass density as low as 0.034 g/cm³). The working of the proposed design hinges on a 3D trampoline-like mode behavior that gives rise to wide, omnidirectional, and low-frequency band gaps for elastic waves despite very low-mass densities. Such a 3D trampoline effect is derived from a network of overhanging nodal microarchitectures that act as locally resonating elements, which give rise to band gaps at low frequencies. I will then present results on architected metamaterials made of a periodic arrangement of octet truss units with alternating circular strut diameters. The octet truss endows the meta-structure with a high effective stiffness and a low effective density, while alternating the units with different struts radii enables the opening of a band gap for elastic waves. For both types of metamaterials, samples were 3D printed and experimentally validated using a shaker and accelerometer. Unidirectional compression test was also performed to characterize the mechanical properties of the octet truss lattice.