In order to improve the thermal shock and ablation resistance of high thermal conductivity carbon/carbon composites, carbon nanotubes (CNTs) were introduced by electrophoretic deposition. After modification, the flexural strength of the composites increases by 53.0% due to the greatly strengthened interfaces. During thermal shock between 1100 °C and room temperature for 30 times, the strength continues to increase, attributed to the weakened interfaces in favor of fiber and CNT pull-out. By introducing CNTs at interfaces, thermal conductivity of the composites along the fiber axial direction decreases and that along the fiber radial direction increases. As the thermal shock process prolongs, since the carbon structure integrity of CNT and matrix in the modified composites is improved, the conductivity increases whatever the orientation is, until the thermal stress causes too many defects. As for the anti-ablation performance, the mass ablation rates of the CNT-modified composites with fibers parallel to and vertical to the flame decrease by 69.6% and 43.9% respectively, and the difference in the mass ablation rate related with fiber orientations becomes much less. Such performance improvement could be ascribed to the reduced oxidative damage and the enhanced interfaces.

    Abstract
    1 Introduction
    2 Experimental
        2.1 Preparation of the CNT-modified HTC-CC composites
        2.2 Tensile test of the fiber bundles
        2.3 Thermal shock test
    3 Test of the mechanical and thermal conductive properties
        3.1 Internal friction measurement
        3.2 Micron-indentation test
        3.3 Ablation test
        3.4 Thermogravimetric (TG) test
        3.5 Characterization
    4 Results and discussion
        4.1 Optimizing the CNT content on fiber
        4.2 Effects of CNTs on the thermal shock resistance of HTC-CC composites
        4.3 Effects of CNTs on the ablation resistance of HTC-CC composites
    5 Conclusions
    Acknowledgements 
    References

• Xue‑Song Liu(State Key Laboratory of Solidification Processing, Shaanxi Province Key Laboratory of Fiber Reinforced Light Composite Materials, Northwestern Polytechnical University)
• Qian‑Gang Fu(State Key Laboratory of Solidification Processing, Shaanxi Province Key Laboratory of Fiber Reinforced Light Composite Materials, Northwestern Polytechnical University)
• Han‑Hui Wang(State Key Laboratory of Solidification Processing, Shaanxi Province Key Laboratory of Fiber Reinforced Light Composite Materials, Northwestern Polytechnical University)
• Ming‑De Tong(State Key Laboratory of Solidification Processing, Shaanxi Province Key Laboratory of Fiber Reinforced Light Composite Materials, Northwestern Polytechnical University)
• Jia‑Ping Zhang(State Key Laboratory of Solidification Processing, Shaanxi Province Key Laboratory of Fiber Reinforced Light Composite Materials, Northwestern Polytechnical University)
• Jia‑Ping Zhang(State Key Laboratory of Solidification Processing, Shaanxi Province Key Laboratory of Fiber Reinforced Light Composite Materials, Northwestern Polytechnical University)
• Qiang Song(State Key Laboratory of Solidification Processing, Shaanxi Province Key Laboratory of Fiber Reinforced Light Composite Materials, Northwestern Polytechnical University)