Complete band gaps in sandwich phononic crystal plates

By using the finite element method, the propagation of Lamb waves in sandwich phononic crystal plates is investigated. This structure is composed of a two-dimensional phononic crystal plate coated with two homogeneous substrates on both surfaces. The phononic crystal plate is constituted by a square array of elastic cylinder embedded in a solid matrix. It is shown that some complete band gaps are opened by changing the thickness of the phononic crystal plate, and that the width of the first band gap becomes larger as the thickness increased. The influence of the thickness and material properties of the substrates on the width of the complete band gap is discussed as well. It is noted that the thickness of either phononic crystal plate or substrates plays a key role in tuning the band gaps of the sandwich phononic crystal plates.