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  1. Free, publicly-accessible full text available April 1, 2023
  2. Abstract A new class of electromechanically coupled metamaterial is presented which relies on magnetic field interactions between the host structure and a local resonator circuit to realize novel vibration control capabilities. The metamaterial chain exhibits a highly tunable vibration band gap which can be easily placed at a desired frequency using the resonant circuit parameters, providing a robust mechanism to independently alter the band gap width, depth, and frequency of maximum attenuation. In its dissipative form, the electromechanical metamaterial is shown to exhibit electrical metadamping as a function of the local resonance circuit resistance. The impact of the damping ratio as a function of the electrical resistance is characterized in frequency and time domains, and related to the infinite system dynamics. A robust experimental realization of the system is constructed which achieves electromechanical coupling through a moving coil and magnet system. The apparatus is used to show that the band gap location and depth can be readily tuned with the circuit elements. The presented metamaterial has potential for meaningful vibroacoustic practical applications in addition to revealing fundamentally new properties of damped electrically-resonant structures.
  3. Abstract Energy dissipation in polymeric composite metamaterials requires special mathematical models owing to the viscoelastic nature of their constituents, namely, the polymeric matrix, bonding agent, and local resonators. Unlike traditional composites, viscoelastic metamaterials possess a unique ability to exhibit strong wave attenuation while retaining high stiffness as a result of the “metadamping” phenomenon attributed to local resonances. The objective of this work is to investigate viscoelastic metadamping in one-dimensional multibandgap metamaterials by combining the linear hereditary theory of viscoelasticity with the Floquet-Bloch theory of wave propagation in infinite elastic media. Important distinctions between metamaterial and phononic unit cell models are explained based on the free wave approach with wavenumber-eliminated damping-frequency band structures. The developed model enables viscoelastic metadamping to be investigated by varying two independent relaxation parameters describing the viscoelasticity level in the host structure and the integrated resonators. The dispersion mechanics within high damping regimes and the effects of boundary conditions on the damped response are detailed. The results reveal that in a multiresonator cell, strategic damping placement in the individual resonators plays a profound role in shaping intermediate dispersion branches and dictating the primary and secondary frequency regions of interest, within which attenuation is most required.