COMPLETE ACOUSTIC BAND-GAPS IN PERIODIC FIBER-REINFORCED COMPOSITE-MATERIALS - THE CARBON-EPOXY COMPOSITE AND SOME METALLIC SYSTEMS

We present results of elastic band structure for two-dimensional compo site materials, composed of periodical square arrays of parallel cylin ders in a background. We reveal, for the first time, the existence of several very large complete band gaps in the band structure of a mater ial of practical interest such as a C fibre reinforced epoxy composite . Within these gaps the propagation of acoustic waves is forbidden. Th e influence of the geometry of the cylinders and the effect of the com position of the composite material on the band structure are studied. We also compare these results with those obtained for metallic composi tes such as W (Al) cylinders in an Al (W) matrix. The complete band ga ps are observed in the cases of C cylinders in epoxy or W cylinders in Al, but not in the opposite situations. We discuss the existence of t hese gaps in relation to the physical parameters of the materials invo lved.