Microstructural design and experimental validation of elastic metamaterial plates with anisotropic mass density

A microstructure design of anisotropic resonant inclusions is investigated for the elastic metamaterial plate with the aid of the numerically based effective medium model. Experimental validation is then conducted in the anisotropic metamaterial plate through both harmonic and transient wave testing, from which the anisotropic effective dynamic mass density, group, and phase velocities are determined as functions of frequency. The strongly anisotropic mass density along two principal orientations is observed experimentally and the prediction from the experimental measurements agrees well with that from the numerical simulation. Finally, based on the numerically obtained effective dynamic properties, a continuum theory is developed to simulate different guided wave modes in the elastic metamaterial plate. Particularly, high-order guided wave coupling and repulsion as well as the preferential energy flow in the anisotropic elastic metamaterial plate are discussed.