Aerospace Research Institute of Materials and Processing Technology

Abstract Accurate elastic modulus data are crucial for mechanical design and life-cycle assessment of aerogel-based thermal insulation systems. However, direct mechanical tests are often cumbersome and costly. To address this challenge, we developed a thermal conductivity driven inversion framework that converts temperature-dependent solid thermal conductivity measurements into temperature-dependent elastic modulus values for aerogels. The framework integrates lattice-vibration thermal transport theory with the relations linking elastic modulus to sound velocity and is implemented using two lattice-vibration thermal transport models: the Minimum Thermal Conductivity (MTC) model and the Diffuson-Mediated (DM) model. Comparison with experimental data in the literature and our own silica aerogels validates that the MTC-based inversion framework provides more accurate temperature-dependent predictions, with deviations below 8% from compression-test modulus over the studied temperature range. The validated framework is then extended to alumina aerogels and fiber-reinforced aerogel composites. It is found that small fiber fractions significantly enhance mechanical stiffness with minimal impact on thermal conductivity. These findings confirm that the proposed inversion framework is suitable for a wide range of aerogel-based composites. The present inversion framework offers significant advantages for real-time assessment of thermal and mechanical performances of aerogel insulation, making it an essential tool for advanced thermal protection systems in aerospace and energy applications.

Purpose Continuous SiC fiber-reinforced SiC matrix composites (SiCf/SiC) have a wide application prospect in aerospace fields due to their excellent high-temperature performance, corrosion resistance and oxidation resistance. SiCf/SiC composites face significant challenges under extreme aerothermal environments, which will cause oxidation-induced interphase degradation, thermal stress and surface ablation damage. The paper aims to investigate the ablation behavior of SiCf/SiC composites by using the arc wind tunnel test for the application of the material. Design/methodology/approach SiCf/SiC composites are subjected to single and five cycles of ablation by using the arc wind tunnel tests. The influence of machining processes on ablation resistance is investigated via comparative analysis of mechanical properties. Microstructural evolution before and after ablation is characterized using scanning electron microscopy, and the ablation mechanism is further revealed. Findings The results reveal that after single ablation, the composites exhibit negligible changes in tensile and flexural strengths. After five-cycle ablations, the tensile strength exhibits a substantial enhancement. Microstructural analysis suggests that passive oxidation predominantly occurred during the process of ablation, resulting in low ablation rates and the formation of dense oxide layers. These oxide layers effectively seal surface pores and microcracks, leading to maintain or even improve the mechanical properties. Originality/value This research provides essential experimental data and theoretical insights for understanding the ablation mechanisms of SiCf/SiC composites in high-temperature gas flow environments, while also offering technical support for their advanced aerospace applications.