High-temperature mechanical properties testing and constitutive relation of needle-punched C/C composite

In order to study the high-temperature mechanical properties of needle-punched C/C composite,the tests of tensile,compress and shear at different temperatures on C/C composites have been conducted.The failure modes of C/C samples under high-temperature and external loads have been observed, and the stress-strain curves at different temperature are also obtained.Based on the improvement of Jones-Nelson-Morgan model and the introduction of temperature coefficient,a C/C constitutive relation model was established and compared with the testing results.The results show that, at the temperature less than 1800 ℃, the needle-punched C/C material follows a linear elastic constitutive relation, and the tensile, compressive and shear strengths increase first and then decrease with increase of the temperature. The strength decreases gradually when the temperature is above 1600 ℃.The calculated results from a constitutive model are in good agreement with the experimental results.The overall performance of C/C materials is of brittle failure, and the pull-out size of tensile failure fiber is short,whereas the compression fracture presents a 45° notch.