ELASTIC WAVES IN PERIODIC COMPOSITE MATERIALS
M. KAFESAKI and E. N. ECONOMOU
Research Center of Crete-FORTH, P.O. Box 1527, 711 10 Heraklion Crete,
Greece and
Department of Physics, University of Crete, 714 09, Crete, Greece
and M. M. SIGALAS
Ames Laboratory and Department of Physics and Astronomy
Iowa State University, Ames IA 50011
Abstract
The study of the elastic and acoustic wave scattering by a single
sphere is used to analyze and to predict band structure results
in composites consisting of periodically placed spheres in a host material.
It was found that classical wave
propagation in a composite can be understood by considering two
idealized channels: the first is using the host and the
second is by hopping
coherently from sphere to sphere using the resonances of the single
scattering cross-section - in analogy with the LCAO in solids and molecules.
Thus, widely separated strong resonances with a strong background
in between (attributed to a rigid or soft sphere) in the single
sphere scattering cross-section implies a wide gap in the periodic
composite. It was found that a high density sphere embedded in a plastic
produces cross-sections favorable for gaps.
Detailed band structure results
confirm this prediction.