  Boundary Singularity Method (BSM) was used to model Chemical Vapor
Infiltration (CVI) in a fibrous preform. Straight, long fibers of varying
cross-sectional geometry, representing fibers of a preform, were placed within
a domain of a pre-determined size. The preparation of dense fiber-reinforced
Silicon-Carbon (SiC) composites was considered as a representative of CVI
methodology, where methyl-trichlorosilane (MTS) was used as both the silicon
and carbon donor for the silicon carbide matrix. Concentrations of MTS were
then set at the domain boundaries, and the domain was gradually infiltrated
with MTS as time progressed. The concentration of MTS at the surface of the
preform fibers was calculated using the adopted BSM. For quasi-equilibrium
considered, the reaction rate at solid surface is equal to the diffusion rate
towards the surface. The Robin or third type boundary condition, which is a
linear combination of the values of a function and the values of its derivative
on the boundary of the domain, are developed and implemented to BSM. From the
fibers surface concentrations obtained by BSM, deposition rates were
calculated, and the geometry was updated to reflect the fiber growth during the
time step, therefore, the fiber size growth and pore filling was modeled over
time. The BSM analysis was verified by comparisons to a known analytical
solution of concentric cylinders with a concentration set at the outer cylinder
and a reaction at the inner. BSM solutions were also compared to experimental
data as well as computational results obtained by a Level-Set Method (LSM).
Obtained dynamics of pore size and location will help to evaluate quality of
material manufactured by CVI. Porosity transients were obtained to show the
relation between initial and current porosities as time progresses.
