Experimental and numerical analysis on the thermal degradation of reinforced silicone-based composites: Effect of carbon fibres and silicon carbide powder contents

Abstract

Silicone-based composites material as Thermal Protection System (TPS) found a large use in the aerospace industry to protect wall structures from severe heating (airframe or propulsion parts, including ramjet type). The matrix of the composite material is often reinforced with fillers, such as Carbon Fibres (CFs) and Silicon Carbide Powder (SCP). This formulation aims to improve the thermomechanical properties which leads to significant impact on the thermophysical parameters (λ, ρ, cp). The present work consists of studying the effect of the CFs and SCP contents on the thermophysical properties evolution. For this purpose, three samples of silicone-based composites, referenced as M1, M2 and M3, are prepared by MBDA–France. The difference among the three samples is in the CFs and SCP contents in each sample. Firstly, some experimental studies were conducted to determine the thermophysical properties (λ, ρ, cp) in a temperature range from room temperature to 1000 °C. Dedicated experimental apparatus are used: dilatometry for density measurement, Calvet calorimeter combined with Differential Scanning Calorimetry (DSC) experiments for specific heat capacity determination, and finally laser flash analysis for thermal diffusivity measurement leading to the thermal conductivity calculation. Secondly, the measured thermophysical properties are used in a 1D numerical procedure using Amaryllis modulus of the SAMCEF™ finite element code in order to investigate the thermal efficiency of the materials as TPS. The comparison of the results confirms that the three silicone-based composites, M1, M2, M3, behave as efficient thermal barriers when exposed to severe heat fluxes. The lower the amount of CF, the higher the thermal efficiency. To a lesser extent, an increase in the amount of SCP tends to improve the insulation efficiency.