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.

Extraordinary acoustic shielding by a monolayer of periodical polymethyl methacrylate cylinders immersed in water Impedance spectroscopy and optical characterization of polymethyl methacrylate/indium tin oxide nanocomposites with three-dimensional Voronoi microstructures Acoustical determination of the shear relaxation functions for polymethyl methacrylate and Epon 828Z This paper presents the results of an experimental study conducted to obtain an acoustic characterization of polymethyl methacrylate (PMMA) and three Epon 828 formulations in their glassy state. By using a pulse-transmission technique, ultrasonic dispersion data were obtained for these polymeric materials as a function of frequency and temperature, and then the principle of time-temperature superposition was used to transform the dispersion data for each material into a linear-viscoelastic "master-curve" representation. The master curve for each material contains sufficient information to determine the propagation characteristics of a low-amplitude wave as a function of its frequency (or frequency spectrum) and the temperature of the polymer. This representation is equivalent to the more common stress-relaxation-modulus and complex-moduli representations of linear-viscoelastic behavior and is valid over an extensive frequency range.

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.

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The lack of reservoir material property data has been identified as a major obstacle to geothermal development and commercialization. To meet this need a h i g h pressure/high temperature test facility was designed and constructed a t Terra Tek under Department o f Energy funding. Testing capabilities include confining and pore fluid pressures to 200 MPa and temperatures to 535°C. Rock samples to 10.2 cm diameter can be accommodated. The program summarized herein i s the second year (October 1977-September 1978) effort (DOE Contract DE-AC07-77ET28301). Test techniques were developed to'meet the geothermal community needs and tests were conducted to determine: mechanical properties , thermal conductivity, thermal diffusivity, thermal expansion, permeability, electrical resistivi ty and ultrasonic velocities. basalts, from KGRA's i n Baca, New Mexico; Milford, Utah; Geysers, Sandstones, graywackes , granites, and Cal ifornia and Northern Nevada, respectively were characterized.