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3-D Modeling of Forced-Flow Thermal-Gradient CVI for Ceramic Composite Fabrication

Published online by Cambridge University Press:  21 February 2011

Thomas L. Starr  and
Arlynn W. Smith
Thomas L. Starr
Affiliation:
Georgia Tech Research Institute, Georgia Institute of Technology, Atlanta, GA 30332
Arlynn W. Smith
Affiliation:
Georgia Tech Research Institute, Georgia Institute of Technology, Atlanta, GA 30332
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Abstract

Forced-flow thermal-gradient chemical vapor infiltration (FCVI) has demonstrated excellent potential for fabrication of high strength, high toughness ceramic composites. Extension of this process to large and complex shapes is facilitated by use of a computer model to optimize process conditions and hardware for rapid, uniform infiltration.

A 3-D model has been developed using a “finite volume” formulation. A steady-state solution for heat conduction and Darcy's law permeation produces temperature and gas flow distributions within the fiber preform. These are used to generated matrix deposition rates within each volume element. By “marching” through time, a complete simulation of the densification process can be obtained.

The model is demonstrated for a FCVI system with cylindrical symmetry and compared to experimental results obtained at the Oak Ridge National Laboratory. The model results suggest a self-optimizing feature of the force flow/thermal gradient CVI process that produces uniform density in the final composite over a range of infiltration conditions. This matches experimental observation where good uniformity has been achieved over a wide range of gas flows, pressure and temperature.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 168 , 1989 , 55
Copyright
Copyright © Materials Research Society 1990

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