Real-time ultrasonic monitoring of fiber-matrix debonding in ceramic-matrix composite

Real-time ultrasonic techniques were developed for monitoring damage in a unidirectional ceramic-matrix composite under longitudinal tensile loading. Specifically, shear-wave transducers producing waves polarized in the transverse to the fiber direction were used in contact with the specimen to detect the initiation and propagation of fiber-matrix debonding, and to determine the transverse shear modulus and its degradation. The ultrasonically measured transverse shear modulus and its degradation was in reasonably good agreement with a prediction based on a modified shear lag model and interpolation between available solutions for fully bonded and fully unbonded fibers.