Effects of different loading methods on thermal expansion behaviors of 2D cross-ply carbon/carbon composites from 850 ℃ to 2300 ℃

摘要

2D cross-ply carbon/carbon (C/C) composites were prepared by isothermal chemical vapor infiltration (ICVI) process. Thermal expansion behaviors of 2D cross-ply C/C composites and effects of static loading and fatigue loading conditions on coefficient of thermal expansion (CTE) of the C/C composites from 850 ℃ to 2300 ℃ were studied. In static test cases, different damage levels were produced inside samples by displacement-controlled three-point bending loading. Meanwhile, flexural fatigue experiments were conducted under stress level of 70%, cycling numbers (N) of 10~5 and 10~6 at a sinusoidal loading frequency of 15 Hz. Afterwards, the thermal expansion behaviors were investigated. It showed that CTE of the C/C composites after static loading and fatigue loading had a decrease compared with CTE of the as-prepared C/C composites. After static loading, there was a larger decrease in CTE for the C/C composites with more severe damage levels. Moreover, the influence of damage on CTE reached to the greatest at around 1550 ℃. The largest decline percentage of the C/C composites after static loading and fatigue loading was 30% and 85% in contrast to the as-prepared C/C composites, respectively. In addition, weakening interfacial strength of the C/C composites was the main effect on the large decrease of CTE after the fatigue loading.