Modern Nondestructive Test Methods for Army Ceramic Matrix Composites

摘要

As composites have developed and matured, the nondestructive testing (NDT) methods needed to characterize and maintain them have also developed and matured. The purpose of this report is to examine the newer methods of NDT, which may be applicable to some of the new composite materials being used for U.S. Army applications. Ceramic matrix composites (CMC) are potentially good high-temperature structural materials because of their low density, high elastic moduli, high strength, and for those with weak interfaces, surprisingly good damage tolerance. Ultrasonic testing (UT) has long been one of the most widely used and most effective methods of inspecting composite materials. Some new types of UT are the ultrasonic multiple-gate C-scan technique, resonant ultrasound spectroscopy, phase UT, acousto-ultrasonics, liquid crystal display UT, and flexible transducer UT. In addition to UT, several other nondestructive test techniques have recently been found to be effective with some of these new composite materials. They include transient thermal conductivity measurements, flexural wave with holography NDT, pulsed thermography, and the dynamic characterization technique. The report will describe each of these new techniques, give the advantages and disadvantages of each one, state when and with what materials and systems each method is usable, and combine finite- element analysis with conventional analysis of nondestructive methods for examining CMCs.