Detection and characterization of porosity in ceramic/ceramic composites. [SiC]

Technical Report · Mon Jul 25 00:00:00 EDT 1988

OSTI ID:6975937

Walter, J B; Lott, L A

Ceramic composites are an important new type of material being developed for applications requiring high strength at high temperatures. This report focuses on composites of a SiC fabric reinforced SiC matrix formed by chemical vapor infiltration. This material is characterized by extensive porosity, which is known to limit its strength. Effective methods of nondestructively detecting and characterizing porosity in the material are needed. This is a challenging task for ultrasonics because of the high levels of porosity (>10%) found in the material and because of the intrinsic heterogeneity and anisotropy of the material, all of which strongly affect ultrasonic propagation. Techniques are described for measuring ultrasonic attenuation, transmitted energy, and propagation velocity using through transmission. Measurements are included which show correlation with the material porosity. A mathematical model was successfully developed to help understand the measurements and to permit extrapolation of the results to other sample sets. A comparison of the model to the measurements is reported. Implications of the model on the detection and resolution of individual voids and on distinguishing them from variations in the general porosity of the material are considered. 6 refs., 12 figs.

• Research Organization: EG and G Idaho, Inc., Idaho Falls (USA)
• DOE Contract Number: AC07-76ID01570
• OSTI ID: 6975937
• Report Number(s): EGG-MS-8179; ON: DE88016965
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360203 -- Ceramics
Cermets
& Refractories-- Mechanical Properties
360602 -- Other Materials-- Structure & Phase Studies
42 ENGINEERING
420500 -- Engineering-- Materials Testing
ACOUSTIC TESTING
ATTENUATION
CARBIDES
CARBON COMPOUNDS
CERAMICS
COMPOSITE MATERIALS
EQUATIONS
MATERIALS
MATERIALS TESTING
MATHEMATICAL MODELS
MONTE CARLO METHOD
NONDESTRUCTIVE TESTING
POROSITY
SILICON CARBIDES
SILICON COMPOUNDS
TESTING
ULTRASONIC TESTING
VELOCITY