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Low diffusivity 1 - High diffusivity

20 cm

Low diffusivity 1 - High diffusivity

FIGURE 13.35 Detection of delamination in large 75-cm diameter, CVI SiC/SiC combustor liner: (a) initial thermal diffusivity, (b) X-ray CT volume image of one layer, and (c) diagram of (b).

FIGURE 13.35 Detection of delamination in large 75-cm diameter, CVI SiC/SiC combustor liner: (a) initial thermal diffusivity, (b) X-ray CT volume image of one layer, and (c) diagram of (b).

primary methods used to date have been air-coupled ultrasonic methods, thermal imaging methods, and XCT. Figure 13.31 demonstrated correlations between density and thermal diffusivity and transmitted ultrasound signal strength for a PIP SiC/SiC. In a recent example [58], a melt-infiltrated SiC/SiC cylinder for a gas turbine combustor shell experienced an "upset" during processing. NDE data—see Fig. 13.36—suggested that there was a clear detectable difference at the process-upset position. Subsequent destructive analysis as noted in Fig. 13.36c, detected a difference in porosity.

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