Numerical simulation and experimental analysis of ablation response behavior of silicone rubber based flexible ablative material

Abstract

SR-FAMs play a critical role in the aerospace and fire protection sectors for thermal protection purpose. Nevertheless, the ablation mechanism and internal response behavior of SR-FAMs remain unclear because complex thermochemical reactions occur when they face with high temperature ablation conditions. In this work, a PDMS/CF/SiO₂ composite containing 6 phr CF and 10 phr SiO₂ was selected as the model system, and the pyrolysis mechanism of PDMS/CF/SiO₂ composite was studied through a holistic analysis of the type of gaseous products, the composition of solid residue, and the evolution of microstructure at high temperatures. A multi-stage pyrolysis kinetic analysis was conducted to determine the kinetic parameters associating with each pyrolysis stage, which enabled accurate description of the thermal decomposition characteristics. Moreover, an ablation model was constructed to capture the ablation deformation and simulate ablation process of PDMS/CF/SiO₂. The proposed model successfully predicted the time-dependent evolution of three-dimensional temperature fields, conversion of pyrolysis products, gas-phase flow, and pressure distribution. The simulation results indicated that the transition of horizontal-to-vertical gas flow promoted the formation of columnar barrier structures in the char layer of PDMS/CF/SiO₂. The results of the numerical model agreed well with experimental data in terms of LAR, MAR, surface and back-face temperature, with a prediction error less than 5%. This work provided new insights into the ablation behavior of SR-FAMs and offered reference to the design and optimization of flexible thermal protection materials.