Title: NONDESTRUCTIVE EALUATION OF WOVEN FABRIC REINFORCED CERAMIC COMPOSITES

Abstract:
Monolithic ceramics are highly sensitive to process and service-related flaws, making them inherently brittle. Due to their low toughness, these materials fail catastrophically. Continues fibre reinforced ceramics (CFCCs) or whisker reinforced CMCs, however, can provide a significant amount of toughness as well as avoid catastrophical failure.

Up to the present time, relatively little work has been performed on the nondestructive evaluation of continuos woven fabric reinforced CMCs. In this investigation, the ultrasonic scan and X-ray computed tomography were used for nondestructive evaluation of woven Nicalon fabric reinforced silicon caroide (SiC) composites, which were fabricated by the chemical yapor infiltration technique. Both the ultrasonic scan and the X-ray computed tomography were used to characterize the type of and the location of flaw in the composites.

An ultrasonic c-scan was used to detect variations of porosity and to characterize the defect distribution in the composites. The relationship between the ultrasonic C-scan amplitude and porosity was quantitative established through the result of X-ray computed tomography. Moreover, moduli of the Nicalon/SiC composites were measured using an ultrasonic technique, and a theoretical model was formulated to predict the moduli of woven fabric composites.

This work is supported by the National Science Foundation, under contract No. EEC-9527527 with Mrs. May Poats as a contract monitor, and under contract 11X-ST270V with the Oak Ridge National Laboratory, Marnn Marietta Energy Systems Inc.
(Ref. SXVIII-028-97)

Source: NDE of Ceramics '97 May 4-7, Symposium on Nondestructive Evaluation of Ceramics at the American Ceramic Society 99th Annual Meeting, Cincinnati, Ohio.
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