Ablation Mechanism and Process of Low-Density Needled Quartz Felt/Phenolic Resin Thermal Protection Materials Under Long-Term Low–Medium Heat Flow

In the aerospace industry, low-density quartz fiber/phenolic resin composites offer advantages such as low cost, low density, high thermal insulation, and excellent thermal resistance, making them a promising candidate when exposed to a long-term low–medium heat flow environment. However, there is currently a lack of understanding regarding the ablation evolution and mechanisms of these materials under this environment, which hampers the enhancement of material performance. Additionally, there is insufficient quantification of their pyrolysis processes, which is detrimental to the development of subsequent mathematical models for ablation thermal response. Therefore, this work focuses on the study of the ablation process of low-density needled quartz felt/phenolic resin (PR/NQF) under long-term low–medium heat flow. Ablation samples of PR/NQF with varying densities were obtained by treating them with a quartz lamp at different temperatures. The differences in the carbonization of the PR/NQF ablation surface were analyzed through SEM, microCT, FTIR, XRD, and XPS experiments, revealing the influence of ablation temperature and composite density. Subsequently, the pyrolysis mechanism of PR/NQF was analyzed using Py-GC-MS, resulting in insights into the evolution and component ratio of pyrolysis gases and their temperature correlations. To further describe the pyrolysis process of low-density PR/NQF, a pyrolysis kinetics model was developed based on the TGA experimental results, and the consistency between the fitted results and theoretical values was validated. The conclusions of this study provide support for analyzing the ablation mechanisms and evolution processes of low-density PR/NQF under long-term low–medium heat flow. Furthermore, the conclusions offered a certain degree of basic data support of mathematical models for ablation processes and the development of new thermal protection materials.