PLANE-WAVE PROPAGATION IN FINITE 2-2-COMPOSITES

A common practice in the study of wave propagation in stratified struc tures is to use the Floquet (or Bloch) condition to derive the dispers ion relation, leading to the passband and stopband structures. However , the Floquet condition is valid only for an infinite system while a r eal system always has finite dimensions. We report a study on wave pro pagation in a finite 2-2 composite by using the transfer (T) matrix te chnique. Through introducing a new definition for the dispersion relat ion using the T matrix, the passbands and stopbands are calculated for a finite system without the Floquet condition. The formation of stopb ands and passbands with the increase of composite size can now be clea rly seen. The spatial profile of the vibration pattern inside a finite composite can also be calculated using this technique, which reveals strong edge effects. The effects of randomization on the wave localiza tion in a 2-2 composite are also studied. (C) 1995 American Institute of Physics.