ABSTRACT
This chapter presents a model for studying dispersion of elastic waves in an infinite medium composed of periodic layers of orthotropic material. Equations governing the phase and group velocities were derived. Since the medium is homogeneous, phase and group velocities are independent of frequency, that is, waves are nondispersive. If the medium is nonhomogeneous, for example a composite medium made up of a distribution of fibers or particles of different material properties embedded in a matrix of some other material properties, an incident plane wave propagating in the medium will be scattered, and constructive and destructive interferences will take place. If the medium has a periodic layered structure, Floquet wave theory leads to a dispersion equation governing various modes of propagation of harmonic waves. The dispersion equation defines a surface in the frequency-wave-number space that has the characteristic feature of exhibiting passing and stopping bands found in wave propagation in periodic media.
