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

An analytical model has been developed to compute the diffraction spec trum and phase of a plane compression wave incident on a long fiber em bedded in a solid elastic matrix. The spectrum is computed as an expan sion of normal modes, thereby permitting insight into the resonant con ditions set up in the fiber. The technique was used to model a reinfor cing fiber, consisting of a graphite core surrounded by a vapor-deposi ted SiC layer, all consolidated within a titanium alloy matrix. Reason able agreement was noted between experiment and theoretical prediction of the resonant frequencies, although bandwidth limitations of the ex periments severely restricted the number of resonance lines that could be included in the comparison. A series of numerical studies was cond ucted to assess the characteristics of each observed resonance. The te chnique has potential application to characterization of the interfaci al layer that links reinforcing fibers to their matrix.