Observation of three-dimensional trampoline-like behavior in an ultra-light elastic metamaterial
Résumé
Elastic metamaterials possess bandgaps, 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 bandgaps 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 trampoline-like mode behavior that gives rise to wide, omnidirectional, and low frequency bandgaps 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 bandgaps at low frequencies.
The dynamic effective properties of the metamaterial are numerically examined, which reveal that the bandgap 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 micro-architectures with overhanging micro-features. This design strategy could be useful to applications where simultaneous light weight and vibration control is desired.
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