Three-Dimensional Trampolinelike Behavior in an Ultralight Elastic Metamaterial

Abstract

Elastic metamaterials possess band gaps, or frequency ranges that are forbidden to wave propagation. Existing solutions for impeding three-dimensional (3D) wave propagation largely rest on high-volume fractions of mass inclusions that induce and tailor negative effective density-based local resonances. This study introduces a class of elastic metamaterials that achieve low-frequency band gaps with a volume fraction as low as 3% (mass density as low as 0.034 g/cm 3 ). The working of the proposed design hinges on a 3D trampolinelike 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. The dynamic effective properties of the metamaterial are numerically examined, which reveal that the band gap associated with the trampoline effect is resulted from a negative effective modulus coupled with a near-zero yet positive effective density. The experimental characterization is then made possible by fabricating the metamaterial via a light-based printing system that is capable of realizing microarchitectures with overhanging microfeatures. This design strategy could be useful to applications where simultaneous light weight and vibration control is desired.

Vat photopolymerization of fly-like, complex micro-architectures with dissolvable supports

“…S4), demonstrating two complete bandgaps at low frequency. A slight shift of the bandgaps in the experimental results can be attributed to minor deviations in the intrinsic material's stiffness and the measurement equipment's performance limitations, and this is consistent with the previously observed bandgaps in the case of a larger sample [43]. Furthermore, via tailoring Young's modulus and feature size of the ligament, a wide frequency range can be achieved, as shown in Fig.…”

“…Here, the outer connecting rods and the unique re-entrant structure allow for the existence of multiple omnidirectional local resonance bandgaps for elastic waves and enable complete vibration attenuation over tailorable frequency ranges (For further information, the reader is referenced to the Fig. S4 and previous work [42,43].). In contrast to metamaterial such as octet truss lattices with all nodes identical and highly connected [13,44], the unit cell topology of the star-shaped re-entrant metamaterials reveals two distinct nodal structures (node 1 and node 2), as shown in Fig.…”

Tailoring Structure‐Borne Sound through Bandgap Engineering in Phononic Crystals and Metamaterials: A Comprehensive Review

“…Reproduced with permission. [ 128 ] Copyright 2021, American Physical Society. m) A 3D resonating metamaterial.…”

“…In fact, architected materials with precise structural building based on connected rods and masses have enabled multiple 3D structures manifesting ultrawide BG for mechanical waves. [117][118][119][120][121][122][123][124][125][126][127][128][129] These efforts paved the way to a new generation of architected elastic metamaterials for omnidirectional wide BG while being lightweight with high porosity.…”

Octet lattice-based plate for elastic wave control

“…Among the fourteen types known to exist in the three-dimensional space 5 , the octet design 16 is an example of face-centered cubic (FCC) topology with promising attenuation potential. The dispersive behavior of this lattice, already renowned in statics for its high strength combined with a slender lightweight profile 17 , has been outlined by Arya et al 18 who show that the octet supports a bandgap whose existence depends upon the aspect ratio of the struts, but do not investigate the underlying physics of its generating mechanism; only briefly suggested by Gerard et al 19 . In addition, most of the state-of-the-art research on such a FCC cell resort to frequency gaps produced by attached resonators 12 or use it as a constitutive matrix of multi-phased materials 20,21 , without delving into its inherent resonant modes.…”