Development of nondestructive evaluation methods and prediction of effects of flaws on the fracture behavior of structural ceramics
- Argonne National Lab., IL (United States)
The purpose of the work reported here is to develop nondestructive evaluation (NDE) methods for intelligent processing of advanced ceramic matrix composite materials to examine fracture behavior of the composites and correlate the NDE data with fracture behavior as an aid to understand processing. Work in this program has emphasized continuous-fiber ceramic matrix composites (CFCCs) with two-dimensional (2-D) lay-ups composed of chemical-vapor-infiltrated (CVI) SiC/SiC materials, primarily those made of Nicalon plain weave with 16 x 16 tows/in. To establish detection capability for mapping fiber tow orientation, images from 3-D X-ray CT data with a special 2-D fast-Fourier transform (FFT) image processing analysis have shown that fiber orientations can be measured to {plus_minus}2-1/2{degrees}. Fracture mechanics work to correlate with NDE data focused on strength distribution studies of as-fabricated Nicalon fibers in composites was assessed by measuring fracture mirror radii. Scanning electron microscopy was conducted to determine the distribution of fiber pullout length distribution for fibers in composites, in order to accurately estimate their strength distribution. From the strength distribution plots, scale parameters were determined to be 3.45 GPa for as-fabricated fibers and 1.31 GPa for fibers in processed composites. However, the Weibull moduli for the two distributions were similar. The above-mentioned reduction in strength of the fibers in processed composites is believed to be due to surface flaws and defects, probably introduced during high-temperature processing and handling, as confirmed by a detailed fractographic evaluation. Effects of fiber misorientation on mechanical properties of NDE-tested CVI continuous-fiber composites are currently being investigated in an effort to correlate NDE results (fiber orientation and density distribution) with fracture properties for continuous-fiber-reinforced ceramic matrix composites.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 140120
- Report Number(s):
- ORNL/FMP-93/1; CONF-9305135-; ON: DE94001091; TRN: 93:003927-0014
- Resource Relation:
- Conference: 7. annual conference on fossil energy materials, Oak Ridge, TN (United States), 11-13 May 1993; Other Information: PBD: Jul 1993; Related Information: Is Part Of Proceedings of the Seventh Annual Conference on Fossil Energy Materials; Fossil Energy AR and TD Materials Program; Cole, N.C.; Judkins, R.R. [comps.]; PB: 402 p.
- Country of Publication:
- United States
- Language:
- English
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Development of nondestructive evaluation methods and prediction of effects of flaws on the fracture behavior of structural ceramics
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