FANG Kai, CHEN Yufeng, ZHANG Shichao, SUN Haoran, WANG Guanghai, SUN Xiankai
(Ceramic Research Institute, China Building Materials Academy, Beijing 100024, China)

Abstract: The passive thermal protection system has been used widely in the dynamic equipment of hypersonic vehicles at present. The typical passive thermal protection system is composed of metals on the top, insulation materials in the middle and structure materials at the bottom. When the dynamic equipment works at a high temperature, because of the tremendous differences between the thermal expansion coefficients of these components, a large gap is formed between the top and middle materials. It is a transmission channel of heat, which will seriously reduce the insulation performance of the thermal protection system. In order to fill the gap, a new kind of insulation material is designed and fabricated using expandable graphite, alumina fiber and aluminum phosphate adhesives. The material can expand the volume at high temperature in order to self-adaptively fill the gap; in the meantime, the difference in the timeliness between the expansion process of expansion sources and the crystallization process of adhesives is used so that the strength of the material do not lose but is increased instead after expansion. The preparation technology, insulation performance and mechanical property are studied in this paper, and the reasons for increasing the strength of the material after expansion are analyzed and expounded.

Key words: alumina fiber; insulation material; expansion characteristic; strength