Effects of Gradient Density on Thermal Protection Performance of AVCOAT Composites Under Varied Heat Flux

Effective heat capacity is a key index to estimate the performance of the thermal protection system of reentry vehicles subjected to aerodynamic heating. To explore the effect of gradient density on the effective heat capacity in this paper, considering variable density we develop the one-dimensional pyrolysis interface model with surface ablation, and design two kinds of the gradient density of AVCOAT composites. The computer codes are written to simulate the thermal behavior of a homogeneous AVCOAT composites and that of two types of gradient AVCOAT composites under aerodynamic heat flux during Apollo capsule reentry. Numerical results indicate that gradient density can improve the thermal protection performance of homogeneous AVCOAT composites, e.g. the piecewise linear and the parabola designs have larger effective heat capacity than homogeneous AVCOAT composites, which owe to exceptional thermal response of gradient density. This study will be helpful for the design of the thermal protection system in re-entry vehicles. (C) 2014 Society of Plastics Engineers