Infrared-based NDE methods for determining thermal properties and defects in ceramic composites

摘要

Continuous-fiber ceramic matrix composites are currently being developed for various high temperature applications, including use in advanced heat engines. In the material classes of interest for such applications, i.e., silicon carbide (SiC)-fiber-reinforced SiC (SiC(sub (f))/SiC), SiC-fiber-reinforced silicon nitride (SiC(sub (f))/Si(sub 3)N(sub 4)), Al(sub 2)O(sub 3 (f))/Al(sub 2)O(sub 3), etc., the condition of the interface between the fibers and matrix is critical to the mechanical and thermal behavior of each component. A nondestructive evaluation method developed at Argonne National Laboratory uses infrared thermal imaging to provide ''single-shot'' full-field measurement of the distribution of thermal diffusivity in large components. By applying digital filtering, interpolation, and least-squares-estimation techniques for noise reduction, the authors have achieved acquisition and analysis times of minutes or less with submillimeter spatial resolution. The system has been used to examine the effects of thermal shock, oxidation treatment, density, and variations in fiber coatings in a full array of test specimens.