Characterization of C/Enhanced SiC Composite During Creep-Rupture Tests Using an Ultrasonic Guided Wave Scan System

Acousto-ultrasonic characterization of C/SiC composites under different loading configurations

“…The results indicated that the parameters were repeatable with the automatic configuration for a single specimen. This same apparatus has demonstrated repeatability as part of a guided wave scanning system in work to be published [8]. Unfortunately, due to lack of availability of the specimens undergoing fatigue testing a more in depth study with the automated approach could not be performed.…”

Initial Attempt to Characterize Oxidation Damage in C/Sic Composite Using an Ultrasonic Guided Wave Method

“…5). Quantifying the relative amounts of oxygen at the different locations was also inconclusive using electron microprobe oxygen mapping of major portions of entire cross‐sections 13 . Another critical defect type, microcracking, was difficult to observe and investigate because of the existing porous microstructure.…”

“…The guided wave method discussed in this article utilizes the total (multi‐mode) ultrasonic response, does so in a scanning configuration, and employs specialized signal processing routines to extract parameters of the time‐ and frequency‐domain signals 8 . These parameters have proven to be sensitive to changes in microstructural conditions and to the presence of defects, 6–8 and appear promising at monitoring degradation in CMCs 9 . Ultrasonic guided waves through the material thickness are generated when the ultrasonic wavelength is on the order of the thickness of the material being interrogated.…”

“…Oxidation in C/SiC falls in the category of distributed microdamage and leads to porosity variations as the fibers essentially disappear because of the oxidation. One method showing promise for characterizing distributed microdamage is the ultrasonic guided wave technique 6–9 . In particular for CMCs, prior studies conducted at NASA GRC have shown ultrasonic guided waves to be successful for characterizing matrix cracking and stiffness degradation in SiC/SiC materials.…”

“…One method showing promise for characterizing distributed microdamage is the ultrasonic guided wave technique. [6][7][8][9] In particular for CMCs, prior studies conducted at NASA GRC have shown ultrasonic guided waves to be successful for characterizing matrix cracking and stiffness degradation in SiC/SiC materials. Advantages of the guided wave technique include (1) the sample under test does not have to be immersed in fluid (as for most conventional ultrasonic characterization), (2) the method requires access to only one side of the sample, and (3) the method is potentially applicable to components with curved surfaces.…”