CALCULATION OF THE THERMAL-CONDUCTIVITY AND GAS-PERMEABILITY IN A UNIAXIAL BUNDLE OF FIBERS

A model of the local microstructure of a bundle of fibers is simulated and used as the basis for calculations of transport properties. This, in turn, can be used in a macroscopic model of the chemical vapor inf iltration process. An expanding/overlapping circle representation of t he microstructure simulates the deposition of matrix in a uniaxial bun dle of fibers. An iterative heat conduction algorithm is used to calcu late the transverse thermal conductivity based on the thermal conducti vities of the solid and gas phases. The permeability of gas through th e microstructure is calculated for flow both parallel and transverse t o overlapping cylinders using a Stokes equation and assuming a Darcy's law behavior. Both the simulations of the microstructure and associat ed calculations of the transport properties compare favorably with exp erimental data. Darcy's law for the behavior of gas in a bundle of fib ers is shown to be valid for gas pressures of 5-13 kPa.