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.%被动热防护是高速飞行器动力装置目前普遍采用的热防护技术,典型的被动热防护系统由金属外层、隔热材料和结构内层组成.动力装置在高温下工作时,由于各层材料的热膨胀系数存在较大差异,在隔热材料和金属外层之间往往会形成较大的间隙.形成的间隙是热量的传输通道,严重影响热防护系统的隔热性能.为了填堵该间隙,本文设计制备了一种由氧化铝纤维、可膨胀石墨、磷酸铝粘结剂组成的新型隔热材料.该材料在高温下具有膨胀特性,能够自适应填充上述间隙;同时利用膨胀源膨胀过程与粘结剂结晶过程的时效差异,使得制备的隔热材料在膨胀后不但未损失强度,反而强度有所增加.本文对该材料的制备工艺、隔热性能和力学性能进行了研究,并分析阐述了该材料经高温膨胀后强度增加的原因.
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