<title>Determining thermal diffusivity and defect attributes in ceramic matrix composites by infrared imaging</title>

Abstract

Ceramic matrix composites are being developed for numerous high temperature applications, including rotors ad combustors for advanced turbine engines, heat exchanger and hot-gas filters for coal gasification plants. Among the materials of interest are silicon-carbide-fiber-reinforced-silicon-carbide (SiC@SiC), silicon-carbide-fiber-reinforced-silicon-nitride (SiC@Si3N4), rduminum-oxide-reinforced-ahtmina (A1203(f)/A1203), etC.In the manufacturing of these ceramic composites, the conditions of the fiber/matrix interface are critical to the mechanical and thermal behavior of the component. Defects such as dehtrninations and non-uniform porosity can directly effect the performance. A nondestructive evaluation (NDE) method, developed at Argonne National Laboratory has proved beneficial in analyzing as-processed conditions and defect detection created during manufacturing. This NDE method uses infrmd thermal imaging for fill-field quantitative measurement of the distribution of thermal diffusivity in large components. Intensity transform algorithms have been used for contrast enhancement of the output image. Nonuniformity correction and automatic gain control are used to dynamically optimize video contrast and brightness, providing additional resolution in the acquired images. Digital filtering, interpolation, and least-squares-estimation techniques have been incorporated for noise reduction and &ta acquisition. The Argonne NDE system has been utilized to determine thermal shock damage, density variations, and variations in fiber coating in a full array of test specimens.

Detection of Ceramic Material Crack Defect Based on the Ultrasonic Infrared Thermal Wave Technique

“…Zeng [6][7] et al has applied the infrared thermal wave method into the ceramic body firing, by monitoring the distribution of the temperature field during the firing, the deformation and temperature variation of the ceramic body was obtained, which has introduced the infrared thermal imaging method into the detection of ceramic materials in China. The infrared thermal imaging technology also was used to determine the ceramic matrix composite thermal diffusion coefficient by the Argonne National Laboratory in the United States, for the same principle, the method can also be used for defect detection of specimen of ceramics [8]. However, by the limitation of the thermal imager temperature resolution, the detection sensitivity of conventional infrared detection technology for ceramic micro defects is low.…”

Measurement of in-plane diffusivity in non-homogeneous slabs by applying flash thermography

“…A pulsed source of radiation, i.e., a laser or a flash lamp, is used to heat one side of the sample, while the temperature response of either front or rear surface is measured by a thermocouple or, without any contact, by an infrared detector. If an extended source is used to provide a uniform heat input and a thermographic camera is used to follow the temperature distribution evolution, a map of the through-thickness thermal diffusivity can be obtained for the tested slab in a single experiment [1][2][3][4][5].…”