Development of nondestructive evaluation methods and prediction of effects of flaws on the fracture behavior of structural ceramics

Conference · Mon Mar 01 04:00:00 EST 1993

OSTI ID:6485705

Ellingson, W A; Singh, J P; Holloway, D L; Dieckman, S L; Singh, D; Sivers, E A

Work emphasized continuous-fiber ceramic matrix composites (CFCCs) with 2-D lay-ups composed of chemical-vapor-infiltrated (CVI) SiC/SiC materials, mostly made of Nicalon plain weave with 16 [times] 16 tows/in. One sample examined comprised a 3-D SiC/SiC braid made by Techniweave. Using a new 1024[times]1024[times]14 bit detector, images from 3-D X-ray CT data with pixel sizes of <140 [mu]m and 2-D fast-Fourier transform (FFT) image processing, we have shown that fiber orientations can be measured to [plus minus]2-1/2[degree]. 3-D FFT analysis was used to determine 3-D braid/weave fiber spacing. Multinuclear ([sup l]H, [sup 13]C, and [sup 29]Si) NMR spectroscopy, is being studied. Surface chemistry of fibers and chemistry of interfacial regions in composites are being studied. We are also conducting initial studies to investigate the bulk composition of matrix materials ([alpha], [beta], amorphous phase, silica, and oxynitride concentration) and surface chemistry of Si[sub 3]N[sub 4] and SiC fibers. Fracture mechanics work to correlate with NDE data focused on strength distribution of as-fabricated Nicalon fibers obtained from bundle tests. Strength distribution of fractured Nicalon fibers in composites was assessed from fracture mirror radii. SEM was used to determine distribution of fiber pullout length distribution for fibers in composites, for 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. Reduction in strength of the fibers in processed composites is believed to be due to surface flaws and defects. Effects of fiber misorientation on mechanical properties of NDE-tested CVI continuous-fiber composites are currently being investigated. 8 figs, 11 refs.

• Research Organization: Argonne National Lab., IL (United States). Materials and Components Technology Div.
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6485705
• Report Number(s): ANL/MCT/CP-79029; CONF-9305135--3; ON: DE93012942
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
42 ENGINEERING
420500 -- Engineering-- Materials Testing
CARBIDES
CARBON COMPOUNDS
CERAMICS
COMPOSITE MATERIALS
COMPUTERIZED TOMOGRAPHY
DEFECTS
DIAGNOSTIC TECHNIQUES
FIBERS
FRACTURE MECHANICS
IMAGE PROCESSING
INDUSTRIAL RADIOGRAPHY
MATERIALS
MATERIALS TESTING
MECHANICS
NITRIDES
NITROGEN COMPOUNDS
NONDESTRUCTIVE TESTING
PNICTIDES
PROCESSING
SILICON CARBIDES
SILICON COMPOUNDS
SILICON NITRIDES
TESTING
TOMOGRAPHY
X-RAY RADIOGRAPHY