THERMAL-MECHANICAL FATIGUE OF FIBER-REINFORCED CERAMICS

摘要

This paper presents the results of tensile and flexural thermal-mechanical fatigue testing of SiC/ SiC, C/SiC, and C/C composites. The work is unique in both the number of composite systems studied (seven SiC/SiC, eight C/SiC, and one C/C) and in the very high temperatures used in the experiments (1316 deg C and 1455 deg C). The temperature and loading transients used in the experiments were chosen to roughly simulate those expected during re-entry of reusable space vehicles. The partial pressure of oxygen was also varied to simulate a re-entry environment. Some of the failure modes of the composites, many of which had protective surface coatings, were examined by optical microscopy and scanning electron microscopy. Many of the C/SiC failures occurred during low temperature (260 deg C) overloads performed at the end of each TMF cycle. Failure of the SiC/SiC composites was attributed to both high temperature damage (creep and fiber degradation) and low temperature overload stresses.