Conformally Graded Metamaterials for Elastic Wave Guidance
arXiv:2306.16240 · doi:10.1016/j.eml.2023.102091
Abstract
Although metamaterials have been widely used for controlling elastic waves through bandgap engineering, the directed guidance of stress waves in non-periodic structures has remained a challenge. This work demonstrates that spatially graded metamaterials based on conformal mappings present a rich design space for controlling and attenuating wave motion - without the need for bandgaps. Conformal mappings transform an elementary unit cell by scaling and rotation into graded lattices with approximately geometrically similar unit cells. This self-similarity allows for control over the local wave dispersion throughout the metamaterial. As a key mechanism, it is shown that elastic waves cannot propagate through graded unit cells with significant size differences, except at low frequencies. This is exploited to create low-pass elastic wave guides, extending beyond classical bandgap engineering, since bandgaps are not required to achieve wave guiding and attenuation. Experiments confirm the low-pass elastic wave filtering capability of a planar truss metamaterial with conformal grading. Finally, a systematic design of curved metamaterial surfaces is presented, providing a flexible framework for programming low-pass attenuation and wave guiding in three dimensions.
References in corpus (7)
- Ultrawide phononic band gap for combined in-plane and out-of-plane waves
- Experimental verification of the "rainbow" trapping effect in plasmonic graded gratings
- A Graded Metamaterial for Broadband and High-capability Piezoelectric Energy Harvesting
- Quasi isotropic underwater acoustic carpet cloak based on latticed pentamode metafuid
- Polar metamaterials: A new outlook on resonance for cloaking applications
- Optimised graded metamaterials for mechanical energy confinement and amplification via reinforcement learning
- Optical evaluation of the wave filtering properties of graded undulated lattices