Different contents of carbon nanotubes (CNTs) were in situ grown on the surface of carbon fiber bundles by injection chemical vapor deposition. The fibers were then stacked into unidirectional preforms and densified by pyrocarbon (PyC) via chemical vapor infiltration. The effects of CNT on the strength and toughness of carbon/carbon composites (C/Cs) before and after heat treatment at 2100 ℃ were investigated. Results show that both the tensile strength and work of fracture achieves the optimum performance when the CNT content is 1.5 wt%. After heat treatment, the tensile strength increases by 25.68% for CNT reinforced C/Cs (CNTs-C/Cs), while only 4.36% for pure C/Cs. The refinement effect of CNT promotes the resistance of PyC matrix against destruction and makes it maintain the structural integrity and continuity even after heat treatment. Before heat treatment, the presence of CNT results in a decreased in-plane lattice size (La) compared with pure C/Cs. while interestingly, after heat treatment, La becomes larger due to the stress graphitization of CNT. The stress graphitization induced by CNT gives the carbon matrix a stronger ability to resist crack propagation, thereby enhancing the strength of the C/Cs. In addition, the existence of CNT changes the fracture mode of the C/Cs and increases the way of energy consumption during the tensile test. Thus, both fibers and the interface of the composites are fully utilized.

通过注入化学气相沉积在碳纤维束的表面上原位生长不同含量的碳纳米管（CNT）。然后将纤维堆叠成单向预成型坯，并通过化学气相渗透法通过热解碳（PyC）进行致密化。研究了碳纳米管对2100℃热处理前后碳/碳复合材料（C / Cs）强度和韧性的影响。结果表明，当CNT含量为1.5 wt％时，拉伸强度和断裂功均达到最佳性能。热处理后，CNT增强C / Cs（CNTs-C / Cs）的抗拉强度提高了25.68％，而纯C / Cs的抗拉强度仅提高了4.36％。CNT的细化效果提高了PyC基质的抗破坏性，即使在热处理后也能保持结构完整性和连续性。La）与纯C / C进行比较。有趣的是，热处理后，由于CNT的应力石墨化，La变大。CNT引起的应力石墨化赋予碳基质更强的抵抗裂纹扩展的能力，从而增强了C / Cs的强度。另外，CNT的存在改变了C / Cs的断裂模式，并增加了拉伸试验过程中的能量消耗方式。因此，纤维和复合材料的界面都得到了充分利用。