ACOUSTIC BAND-GAPS IN FIBER-COMPOSITE MATERIALS OF BORON-NITRIDE STRUCTURE

We present elastic band-structure results for a new geometry of two-di mensional phononic crystals: the boron nitride-(BN-) like structure. T his array is constituted of two kinds of infinite elastic parallel cyl inder located at the vertices of a regular hexagon and surrounded by a n elastic background. This geometry includes both the triangular and g raphite structures as particular cases. The inclusions and matrix are either both fluids or both solids, the constituent materials being wat er and mercury, and carbon (or tungsten) and epoxy. We discuss the evo lution of the band structure, and especially the existence of absolute band gaps, as a function of the ratio between the radii of the two cy linders in the BN geometry. We also discuss the existence of these gap s in relation to the physical parameters of the materials involved, an d compare the results with those for square and triangular structures.