Elastodynamic response of particulate composites /
The elastodynamic behavior of particulate composites, ranging from one-dimensional chains to a three-dimensional stack of layers of spherical particles, is examined by means of ultrasonic testing. Chains reflect ultrasonic longitudinal waves at frequencies corresponding to the condition that the wav...
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
2000.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731980781&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The elastodynamic behavior of particulate composites, ranging from one-dimensional chains to a three-dimensional stack of layers of spherical particles, is examined by means of ultrasonic testing. Chains reflect ultrasonic longitudinal waves at frequencies corresponding to the condition that the waves scattered by the spheres interfere constructively. Transmission and reflection spectra for two-dimensional layers of spherical particles in random, square periodic, and hexagonal periodic arrangements are measured and trends are noted. The periodic layer exhibits near-zero minima in the reflection spectrum and near-unity maxima in the corresponding transmission spectrum at frequencies corresponding to the condition, called "lattice resonance,'' that the distance between two parallel lines of particles is equal to an integer number of shear wavelengths in the matrix. Below such frequencies, a peak is observed in the reflection spectrum with a corresponding dip in the transmission spectrum. This phenomenon, called "synergistic resonance,'' is strengthened if the rigid body (dipole) resonance of the particles is nearby, its frequency and magnitude determined by particle and matrix constituency. A self-consistent theory for predicting the transmission and reflection spectra of a single periodic layer is discussed, which predicts two measurable elastodynamic phenomena. The first is that the spheres are nearly motionless at lattice resonance and that standing shear waves exist in the lattice. This is confirmed by the measurement of shear waves escaping at the edge boundary of a layer. The second prediction of theory is that particle motion is amplified at synergistic resonance due to the dipole/dipole shear wave interaction between particles. This is confirmed by measuring surface motion above a shallowly embedded layer of spheres by the use of laser vibrometry. Finally, the behavior of a three-dimensional stack of periodic layers is examined by a conventional ultrasonic technique as well as with a novel elasto-optic technique. The composite exhibits elastodynamic behaviors that correlate to both inter-layer intra-layer conditions. |
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| Item Description: | Vita. "Major Subject: Aerospace Engineering". |
| Physical Description: | x, 88 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 85-87). |