【作者】 李凯；

【导师】 丁杰； 杨伟平；

【作者基本信息】 武汉理工大学 ， 材料与化工（专业学位）， 2024， 硕士

【摘要】 酚醛气凝胶因其具有独特的微纳米孔结构被广泛应用于飞行器的热防护与高温隔热等领域。但由于酚醛树脂的本征脆性,对以酚醛树脂为基体的有机气凝胶而言,纤维增强的手段是当下扩宽其应用性的研究热点。尤其是近年来随着飞行器速度不断加快、载入环境更加恶劣的背景下。制备一种具有表面耐烧蚀且整体具有一定力学强度的酚醛气凝胶复合材料显得尤为关键。本文基于气凝胶的常压干燥工艺对气凝胶进行制备,在此基础上通过石英纤维织物以及陶瓷瓦的增强设计,完成以酚醛气凝胶为基体的防隔热一体化结构材料的制备与性能研究。首先,以普通线性酚醛树脂(PR)为基体,采用不需经溶剂替换的常压干燥工艺制备酚醛气凝胶。详细研究了不同配方和工艺条件对气凝胶干燥收缩率、密度、微观孔径及力学强度等性能的影响规律。通过以上实验参数的综合比对,探索出经常压干燥法制备酚醛气凝胶的合理工艺条件。在气凝胶密度不超过0.3g/cm~3的前提下,固化剂的含量对其的性能变化的影响是最大。常压干燥法极大程度提高了酚醛气凝胶的生产效率和经济性。按照制备酚醛气凝胶的工艺参数,将柔性石英纤维织物引入酚醛气凝胶制备出一种石英纤维增强酚醛气凝胶复合材料。以3种不同密度的石英织物为变量,制备了石英纤维增强酚醛气凝胶复合材料。研究并对比了不同织物密度对材料的基本物理性能的影响规律,研究发现的材料的比表面积、孔容孔径随着织物密度的增大而变小;压缩、弯曲等力学强度均较纯酚醛气凝胶有很大提高。材料室温导热系数随织物密度增大而提高。考虑到气凝胶在实际应用中单面加热的工况,在表面设计并制备了一种致密化陶瓷壳层。陶瓷壳层增强了材料表面的抗烧蚀性能的前提下,整个结构兼具表面耐烧蚀和隔热性能。丁烷火焰烧蚀发现,有无陶瓷壳层对于材料背温、质量烧蚀率和线烧蚀率均有影响,体现了表层陶瓷壳质量引射的作用。按照制备酚醛气凝胶的工艺参数,将刚性陶瓷隔热瓦引入酚醛气凝胶制备出一种陶瓷瓦增强酚醛气凝胶复合材料。并与石英纤维增强酚醛气凝胶复合材料进行力、热基础性能对比,通过对比可以发现,陶瓷瓦增强酚醛气凝胶复合材料压缩强度更高;导热系数相对更低但是仍比酚醛气凝胶高;中温环境(250℃)下稳态背温更低。同样考虑到气凝胶在实际应用中单面加热的工况,在其表面相同工艺制备了致密化陶瓷壳层。丁烷火焰烧蚀发现,材料结构完整、背温差距较小,但线收缩率和质量收缩率有显著下降。在高温热辐射试验下(900℃),该复合材料最终稳态背温更低。更多还原

【Abstract】 Phenolic aerogels are widely used in thermal protection and high-temperature insulation for aircraft due to their unique micro-nano-pore structure.However,due to the inherent brittleness of phenolic resin,fiber reinforcement is a hot research topic to expand the application of organic aerogels based on phenolic resin,especially in the context of increasing flight speeds and more severe loading environments in recent years.Therefore,it is particularly critical to prepare a phenolic aerogel composite material with surface resistance to erosion and overall certain mechanical strength.In this study,the aerogel preparation process based on atmospheric drying technology is used to prepare the aerogel,and the enhancement design of quartz fiber fabric and ceramic tile is used to prepare the thermal protection and insulation integrated structure material based on phenolic aerogel as the matrix.First,the phenolic aerogel was prepared using the atmospheric drying process without the need for solvent replacement using a conventional linear phenolic resin(PR)as the matrix.The influence laws of drying shrinkage rate,density,microscopic pore size,and mechanical strength on the aerogel were studied in detail.Through the comprehensive comparison of the experimental parameters,the reasonable processing conditions for the preparation of phenolic aerogel by atmospheric drying technology were explored.Under the premise that the density of the aerogel does not exceed 0.3g/cm3,the content of the curing agent has the greatest impact on its performance changes.The atmospheric drying method greatly improves the production efficiency and economy of phenolic aerogel.According to the process parameters for preparing phenolic aerogel,flexible quartz fiber fabric was introduced into the preparation of phenolic aerogel to produce a quartz fiber-reinforced phenolic aerogel composite material.Three different densities of quartz fabric were used as variables to prepare quartz fiber-reinforced phenolic aerogel composite materials.The basic physical properties of the material were studied and compared with different fabric densities,and it was found that the specific surface area and porosity of the material decreased with increasing fabric density,while the compressive and bending mechanical strength were significantly improved over pure phenolic aerogel.The room temperature thermal conductivity of the material increased with increasing fabric density.Considering the condition of one-sided heating in the actual application of the aerogel,a dense ceramic shell layer was designed and prepared on the surface.The ceramic shell layer improved the surface resistance to erosion of the material while maintaining the overall structure with surface resistance to erosion and thermal insulation properties.The flame erosion test with butane showed that the presence or absence of the ceramic shell layer had an impact on the back temperature,mass erosion rate,and line erosion rate,reflecting the quality injection effect of the surface ceramic shell.According to the preparation parameters of phenolic foam insulation,ceramic tiles were introduced into the preparation of phenolic foam insulation to produce a ceramic tile-reinforced phenolic foam insulation composite material.The basic mechanical and thermal properties of the ceramic tile-reinforced phenolic foam insulation composite material were compared with those of the quartz fiber-reinforced phenolic foam insulation composite material.Through the comparison,it was found that the compressive strength of the ceramic tile-reinforced phenolic foam insulation composite material was higher;the thermal conductivity was relatively lower but still higher than that of phenolic foam insulation;the steady-state back temperature was lower at a medium temperature of 250°C.Similarly,considering the heating condition of the phenolic foam insulation in actual applications,a dense ceramic shell layer was prepared on its surface using the same process.The butane flame erosion test showed that the material structure was intact,the back temperature difference was small,but the linear shrinkage rate and mass shrinkage rate had a significant decrease.In the high-temperature thermal radiation test(900°C),the final steady-state back temperature of the composite material was lower.更多还原