Geometric Dispersion of Acoustic Waves by a Fibrous Composite

Abstract

This study was initiated to examine the transmission of acoustic waves through a fibrous composite whose only dispersive mechanism was geometric. The elastic-elastic composite chosen for study was composed of tungsten wires embedded in an aluminum matrix. This unidirectional com posite was manufactured in two constituent ratios, 2.2 and 22.1 percent by volume of tungsten. The dispersive characteristics of these composites were determined for harmonic waves propagating normal to the axes of the fibers by using standard water-bath techniques with wide-band transducers. The dispersion data obtained demonstrate that fibrous composites be have as wave filters which selectively transmit or reflect periodic waves. Further, this wave filtering is shown to be a boundary layer phenomenon which can and must be eliminated from dispersion data if it is to be meaningful.