A Two‐Dimensional Model of Chemical Vapor Infiltration With Radio Frequency Heating

Abstract

A comprehensive, two-dimensional, self-consistent model was developed and used to simulate chemical vapor infiltration of fiber-reinforced composite materials with radio frequency heating. The model included equations for energy transport, multicomponent mass transport, and pore structure evolution, coupled to Maxwell's equations to determine self-consistently the power absorbed by the preform from a radio frequency induction coil. The model equations were solved by a finite element method to study carbon chemical vapor infiltration in a cylindrical carbon preform. Simulations for a constant absorbed power showed that densification of the preform proceeds in an "inside out" manner, first in the radial direction and subsequently in the axial direction, for the aspect ratio studied. The power density distribution in the preform evolves in a complex manner as densified regions absorb more energy with increased densification. This may result in thermal runaway during the infiltration process and entrapment of porosity in the interior of the preform. Comparison of simulated results with reported experimental data showed semiquantitative agreement of important trends. A more accurate description of material properties is required for a quantitative match with the data.

Pulsed-power plasma reactors: two-dimensional electropositive discharge simulation in a GEC reference cell

“…At low frequencies, the current in the coil is nearly constant and the above equation may be solved to determine E θ in the reactor. However, at higher frequencies, a circuit model is required to account for capacitive coupling between the coil and the plasma (the current changes from loop to loop) [18,19]. The power deposited in the plasma was computed by…”

A Two‐Dimensional Model of Chemical Vapor Infiltration with Radio‐Frequency Heating: II. Strategies to Achieve Complete Densification

“…Subsequent densification occurs axially as the reactant concentration front retreats toward the axial ends of the preform. 10 with the capillary pore model for pore structure. lOd).…”

Modelling chemical vapour infiltration of pyrolytic carbon as moving boundary problem

“…CVI is a very slow and thus expensive technique; consequently, there is a huge need in process optimisation based on detailed mathematical modelling and precise and efficient numerical simulations. Many different variants of CVI exist: isothermal (Reuge and Vignoles, 2005;Sotirchos, 1991;Zhang and Hüttinger, 2001;Jin and Wang, 2000, 2003McAllister and Wolf, 1991;Chung et al, 1991), thermal gradient CVI (Tago et al, 2001) forced flow CVI (Probst et al, 1999;Roman et al, 1995;microwave heating, Morell et al, 1993;Midha and Economou, 1998), etc. In this work we concentrate on the isothermal isobaric CVI of pyrolytic carbon since experimental data are available for this process.…”

“…Many of the published works dealing with CVI are based on a simplified reaction kinetics and consist of only one overall reaction (Sotirchos, 1991;McAllister and Wolf, 1991;Chung et al, 1991;Tago et al, 2001;Roman et al, 1995;Morell et al, 1993;Midha and Economou, 1998;Hou et al, 1999). The processes in the gas phase are often assumed steady-state (Middleman, 1989;Reuge and Vignoles, 2005;Zhang and Hüttinger, 2001;McAllister and Wolf, 1991;Chung et al, 1991;Tago et al, 2001;Hou et al, 1999) which is critical since the temporal evolution of the geometry due to deposition influences the transport mechanisms within this phase.…”

“…The question of complete infiltration of the given porous substrate is thus of significant importance. In many studies, porosities are calculated (Reuge and Vignoles, 2005;McAllister and Wolf, 1991;Tago et al, 2001;Morell et al, 1993;Midha and Economou, 1998;Hou et al, 1999;Kulik et al, 2004), but the position of the interface is not tracked. Consequently, the question whether the given substrate is completely infiltrated or not remains open.…”