Two-dimensional locally resonant elastic metamaterials with chiral comb-like interlayers: Bandgap and simultaneously double negative properties

In this paper, bandgap and dynamic effective properties of two-dimensional elastic metamaterials with a chiral comb-like interlayer are studied by using the finite element method. The effects of the geometrical parameters of the chiral comb-like interlayer on the band edges are investigated and discussed. Combined with the analysis of the vibration modes at the band edges, equivalent spring-mass/pendulum models are developed to investigate the mechanisms of the bandgap generation. The analytically predicted results of the band edges, including the frequency where the double negative properties appear, and the numerical ones are generally in good agreement. The research findings in this paper have relevant engineering applications of the elastic metamaterials in the low frequency range. (C) 2016 Acoustical Society of America.