Multiscale modeling of chemical vapor infiltration process for manufacturing of carbon-carbon composite

Abstract

Abstract Producing large parts by chemical vapour infiltration (CVI) process is quite challenging due to non-uniform nature of temperature and gas precursor distribution. Many a times repeated experiments are required to optimize the process parameters for manufacturing composites with isotropic properties. This is not only cumbersome but also cost intensive. To address this critical issue, we develop a multiscale mathematical model for thermal gradient forced chemical vapour infiltration (TG-FCVI) process considering only heterogeneous decomposition of propylene on carbon preform. The model takes account of the flow field, mass transport, reaction kinetics and the transient nature of porosity to identify the optimum process parameters. As the time taken in deposition is very large, the flow in free channel is much faster than the pores and therefore the flow equations are solved coupling both the domains in steady state (low Mach number flow). The effect of various process parameters on composites homogeneity like temperature, temperature gradient, inlet precursor concentration and inlet gas flow rate were studied. The model was validated with the available experimental data. It has been observed that high temperature gradient and inlet concentration favours homogeneous C-C composite with high final bulk density. However, increasing temperature of reactor and reducing inlet reagent concentration causes surface pore blockage and resulting in inhomogeneity in direction of axial flow