DETERMINATION OF FIBER-MATRIX INTERPHASE EFFECTIVE ELASTIC-MODULI FROM ULTRASONIC PHASE-VELOCITY AND ATTENUATION DATA

This paper discusses two potential ultrasonic methods for characteriza tion of fiber-matrix interphases in composites: measurement of phase v elocity and attenuation. The characterization procedures of these two methods, including different implementations using analytical or numer ical models, are reviewed with emphasis on the applicability of these methods. Examples of ultrasonic characterization of interphases in cer amic and intermetallic matrix composites are given and the relation be tween the measured and actual interphase moduli is discussed. Applicat ion of these techniques for interfacial damage assessment is also demo nstrated, including characterization of oxidation damage in ceramic ma trix composites and fatigue damage in metal matrix composites. The exp erimental results show that degradation of the interphasial layer sign ificantly affects ultrasonic wave attenuation and velocity. Thus both methods are very useful for assessment of interfacial damage.