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.

Multi-scale wave propagation modelling for two-dimensional periodic textile composites

“…Predicting stop-band behaviour is thus of great interest and it has been widely investigated for metamaterials such as phononic crystal [30,34,35] or composite materials [27,29,32,36]. However little research has been conducted in textile composites with strongly anisotropic structure.…”

The use of tonebursts as an alternative to broadband signals in the measurement of speed of sound in human cancellous bone

“…Direct comparisons can be made between cancellous bone and synthetic composite materials with regard to the effect of increased attenuation at higher frequencies on the distortion of toneburst waveforms (Sachse and Pao 1978). For example, in tungstenaluminium composites, tonebursts of a relatively high frequency suffer such a dramatic shift in peak amplitude frequency due to attenuation, that an accurate measurement of transit time cannot be made due to waveform distortion (Sutherland and Lingle 1972). We have observed similar behaviour with 1 MHz tonebursts in cancellous bone (figure 3(a)).…”

“…Attenuation of high frequency components of ultrasound waves will also affect the choice of centre frequency for narrowband pulses. The amplitude of a narrowband pulse will be seriously reduced by attenuation if the centre frequency is too high (Sutherland and Lingle 1972). Choosing a relatively low centre frequency would be expected to improve the amplitude response of tonebursts in cancellous bone.…”

Processing and mechanical properties of novel Al-W composites with ordered mesostructure

“…In previous research, plates of Al-W fiber composites with periodically and unidirectionally oriented W wires (Ø127 mm) at two volume ratios of W (2.2 and 22.1%) were processed using the tape lamination technique with bonding at the pressure 20.7 MPa and temperature 565 C for 5 minutes. 17,18 W fibers are ductile and the corresponding composites fail in a different mode compared to reinforcements by brittle fibers (SiC, Al 2 O 3 , and carbon). Shetty and Chou 19 conducted tension and compression tests of the composites with Al (6061) matrix reinforced with continuous W fibers oriented in one direction along the specimen axis.…”