Design, analysis, and experimental investigation of mid frequency bandgap in locally resonant elastic metamaterial

The study presets two designs of locally resonant metamaterial unit cells with a soft elastic matrix to develop bandgap in mid frequency range. Their dispersion relations and wave propagation behaviour are examined using Bloch theory and finite element analysis. Bandgaps and their evolution are explored through a parametric study of the unit cells, and their effect on the effective mass density is evaluated. Numerical findings are validated through experiments on fabricated specimens, showing good agreement in the identification of bandgaps. The results demonstrate that introducing an additional soft rubber layer around the resonator leads to a widening of the bandgap.