ACOUSTIC DIFFRACTION SPECTRUM OF A SIC FIBER IN A SOLID ELASTIC MEDIUM

An analytical model has been developed to compute the diffraction spectrum and phase of a plane compression wave incident on a long fiber embedded in a solid elastic matrix. The spectrum is computed as an expansion of normal modes, thereby permitting insight into the resonant conditions set up in the fiber. The technique was used to model a reinforcing fiber, consisting of a graphite core surrounded by a vapor-deposited SiC layer, all consolidated within a titanium alloy matrix. Reasonable agreement was noted between experiment and theoretical prediction of the resonant frequencies, although bandwidth limitations of the experiments severely restricted the number of resonance lines that could be included in the comparison. A series of numerical studies was conducted to assess the characteristics of each observed resonance. The technique has potential application to characterization of the interfacial layer that links reinforcing fibers to their matrix.