Figure 1: The unit cell and its eigenmodes.
From: Polarization bandgaps and fluid-like elasticity in fully solid elastic metamaterials
A photographic image of the unit cell is shown in a. A simple spring-mass model of the system is shown in the inset, wherein M1, M2 are the mass of the core (steel cylinder), and shell (epoxy), respectively; K and K′ are different spring constants, which are tunable via the thickness of the silicone coating at relevant positions. Simulated displacement profiles of the three translational modes (TMs) are shown in b. Two modes are degenerate at 1,651 Hz, denoted by TM(x) and TM(y), in which the steel and epoxy oscillate anti-phase in the xy-plane. A third mode, denoted by TM(z), is found at 2,637 Hz, in which the steel core and epoxy oscillate anti-phase in the z-direction. Three rotational modes (RMs) are shown in c, characterized by the out-of-phase rotational oscillation of the steel and epoxy along a certain axis (indicated in the parentheses). In b,c, black cones indicate the amplitude and direction of the displacement. Colours represent the displacement component perpendicular to the slicing plane, with red/blue representing positive/negative displacement, respectively. All eigenmodes were calculated using an isolated unit cell.
