Thermal shock resistance and failure mechanism of SiC/SiC composite braided tubes
The two-dimensional two-axis braided SiC/SiC composite braided tubes are taken as the re-search object,and their thermal shock resistance and failure mechanism are studied.A thermal shock test platform based on quartz lamp irradiation heating was built,on which the thermal shock test of SiC/SiC composite braided tubes was carried out,and then the diametral compression test of the braided tubes after thermal shock was also performed.The mechanical properties and failure mechanism of the braided tube were investigated,and the empirical formula of thermal shock strength degradation was obtained by fitting.The results showed that the thermal shock test platform can simulate the service environment with rapid temperature rise and drop,and the maximum heating and cooling rates can reach about 40 and 60 ℃/s,respectively,during the thermal shock test.With the increase of thermal shock cycle number,the circum-ferential tensile strength of SiC/SiC composite braided tubes decreases quickly at an increasing rate.The thermal stress caused by thermal shock leads to the appearance of microcracks in the matrix around the fi-ber and weakens the adhesion between the fiber bundle and matrix,which is one of the main causes of the strength degradation of braided tube.The fitting algorithm can well describe the strength degradation caused by cyclic thermal shock and has the value of engineering applications.
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