Low-frequency surface-acoustic-wave considerations for ceramic-matrix composite-material characterization
Various traditional surface-acoustic-wave techniques are explored along with an innovative line-focus-beam acoustic-lens system for measurement of anisotropic characteristics of Ceramic Matrix Composite (CMC) materials. A systematic and unified approach to material characterization is effectuated by studying the influence of fiber fraction, anisotropy, and inhomogeneities such as porosity, micro-cracking, and delamination on the propagation characteristics and attenuation of surface acoustic waves from various CMC specimens, whose fiber fraction varied between 30 and 50%. This is corroborated by various experiments using a line-source technique in contact mode, oblique-incidence technique in immersion mode, and high-aperture spherically and cylindrically focused transducer techniques. A low-frequency acoustic-microscopy technique is developed by measuring the local perturbation of the Rayleigh surface-wave velocities for imaging small variations in the near-surface characteristics of CMC specimen. A novel approach to material characterization is demonstrated, by using the directional acoustic microscopy in the low-frequency range. This proved to be more sensitive to anisotropic measurements than the traditional high-frequency acoustic microscope.
- Research Organization:
- Drexel Univ., Philadelphia, PA (United States)
- OSTI ID:
- 5457937
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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