Techniques for monitoring damage in ceramic matrix composites

This article offers a review of various nondestructive evaluation and structural health monitoring techniques that have been successfully utilized for assessing the damage state of woven ceramic matrix composites consisting of silicon carbide fibers and silicon carbide matrices. The techniques include acousto-ultrasonics, modal acoustic emissions, electrical resistance, impedance-based structural health monitoring, pulsed thermography, as well as thermoelastic stress analysis. The damage, in the form of distributed matrix cracks and delaminations, was introduced using multiple tactics. These included load/unload/reload uniaxial tensile tests, creep tests, and ballistic impact. Although other nondestructive evaluation techniques have been applied to this material system, the select nondestructive evaluation tools described here are limited to approaches that are of current research interest within programs at the NASA Glenn Research Center.