Determination of fiber-matrix interphase effective elastic moduli from ultrasonic phase velocity and attenuation data

This paper discusses two potential ultrasonic methods for characterization of fiber-matrix interphases in composites: measurement of phase velocity and attenuation. The characterization procedures of these two methods, including different implementations using analytical or numerical models, are reviewed with emphasis on the applicability of these methods. Examples of ultrasonic characterization of interphases in ceramic and intermetallic matrix composites are given and the relation between the measured and actual interphase moduli is discussed. Application of these techniques for interfacial damage assessment is also demonstrated, including characterization of oxidation damage in ceramic matrix composites and fatigue damage in metal matrix composites. The experimental results show that degradation of the interphasial layer significantly affects ultrasonic wave attenuation and velocity. Thus both methods are very useful for assessment of interfacial damage.