Ablation behavior and mechanism of MoSi2/mica/HSM modified CF/BPR composites during prolonged ablation of oxyacetylene flame

Ablative thermal protection materials are widely used in entry and re-entry vehicles which benefit from their strong adaptability. However, long-term ablation has been a limitation due to the consumption of the matrix of the ablative materials. In this work, the microstructure evolution and ablation properties of the MoSi₂/mica-modified CF/BPR composites with and without hollow silicate glass microspheres (HSMs) under protracted ablation have been investigated. The mass ablation rates decreased while the linear ablation rates increased when the ablation times were prolonged. The composites with 30 vol.% HSMs have good insulation properties, shown by a lower backside temperature of 240.9 °C after 100 s of ablation. The decrease in thermal conductivity limited heat transfer in both the axial and horizontal directions. This led to heat concentration and severe ablation at the central surface. The three-dimensional porous and the ladder structure formed in the transfer region, and the features gradually disappeared while extending the ablation times because of the flame erosion and formed liquid phases. The heat diffusion and concentration within the matrix established a gradient temperature field, which determined the ablation behavior and mechanism, providing valuable insights for the development of advanced ablative thermal protection materials.