Use of plate waves for predicting remaining useful life of ceramic matrix composites

Ceramic matrix composite (CMC) materials are being developed for use in high temperature environments where structural integrity is critical. As part of the development, methods that can predict remaining useful life of CMC components become increasingly important. The extent of matrix cracking plays a key role in the remaining useful life of a CMC component. Therefore, as part of the effort to estimate the useful life of CMC materials, the quantification of matrix crack accumulation is critical. The objective of this work is to develop a method to estimate the amount of cracking of in-service ceramic matrix components from data acquired nondestructively. In this work, elastic properties of a CMC material system are calculated from the velocity of the first extensional mode of ultrasonic plate waves. The velocities of the extensional mode of the plate wave are used in conjunction with an elastic modulus based damage parameter to quantify matrix cracking accumulation caused by two loading conditions. The examined loading conditions are: tensile loading and tension-tension cyclic fatigue tests. The approach is demonstrated on four ceramic matrix composite material systems. These include: silicon carbide/barium-magnesium aluminosilicate (SiC/BMAS) with the BMAS matrix deposited using a slurry cast infiltration process, carbon/silicon carbide (C/SiC) material with the SiC deposited using chemical vapor infiltration, C/SiC with the SiC deposited using melt infiltration and a silicon carbide/silicon carbide (SiC/SiC) with the SiC matrix deposited using melt infiltration. As part of the work, a theoretical model based on a shear lag analysis technique is utilized which is capable of estimating the accumulation of transverse matrix cracks induced by monotonic tensile and tension-tension cyclic fatigue loading from the calculated damage parameter. As part of this work, a method is described to estimate the remaining useful life of CMC materials from the measured plate wave velocities using the shear lag model.