Ultra-wideband outward-hierarchical metamaterials with graded design

The narrow band gap width caused by local resonance is the shackle for the further development of conventional metamaterials. In this paper, a novel type of hierarchical metamaterial containing parallel multiple resonators is presented, whose ultra-broadband vibration suppression property originates from a rational gradient design. Characterization of dispersion relations and bandgap characteristics of the one-dimensional outward-hierarchical...