碳纳米管热固性复合材料长期应力原位检测技术研究

There exist many advantages regarding carbon nanotube composite materials in the aspect of in situ detection. But as envisaged, the matrix often consists of macromolecule polymer whose conductive performance is under the influence of carbon nanotube conductive network creep, resulting in poor long-term in situ detection accuracy in terms of piezo-resistive characteristics. In this proposal, through the creep experiment of carbon nanotubes thermosetting composites under different stress, strain and strain rate, the impact of stress, strain and other parameters on the fracture and reorganization of conductive network will be analyzed, upon which creep models regarding fracture dominant and reorganization dominant will be established respectively. Further analysis will be directed to material creep resistance mechanism by Raman spectroscopy and scanning electron microscopy. The effect of stress on long-term stable resistance mechanisms will be investigated through time temperature equivalence principle and Boltzmann superposition principle, so as to establish a long-term stable resistance-stress model, able to realize long-term accurate testing of their stress, which will be validated in carbon nanotube composites in situ detection device. Eventually, carbon nanotubes composites resistance creep theory upon the consideration of the conductive network fracture and reorganization will be set up, able to realize long-term in-situ testing of their stress, accordingly to build a solid foundation for the design and use of carbon nanotubes composites intelligent components. Novel methods will be developed and provided for new generation of intelligent components with the ability of in situ detection, thus to bring significant change to the detecting system for large passenger aircraft, high-speed railway, aerospace and new generation of intelligent manufacturing equipment.

碳纳米管复合材料在原位检测方面具有突出的优势，但因其基体多采用高分子聚合物，导电性能受碳纳米管导电网络蠕变的影响，导致利用其压阻特性实现应力长期原位检测的精度较差。本项目通过研究不同应力、应变与应变率下碳纳米管热固性复合材料的蠕变实验，分析应力应变等多参数对导电网络断裂与重建的影响规律，构建碳纳米管导电网络断裂电阻蠕变模型与重建电阻蠕变模型；通过拉曼光谱与扫描电镜微观检测方法，分析材料电阻蠕变微观机理；利用时温等效原理与玻尔兹曼叠加原理研究应力对长期稳定电阻的影响机制，建立长期稳定电阻-应力模型，实现应力的长期准确检测，并在碳纳米管复合材料压阻原位检测装置上进行验证，最终建立考虑导电网络断裂重组的碳纳米管复合材料电阻蠕变理论，实现碳纳米管复合材料对自身应力的长期原位检测，为具备原位诊断能力的新型零部件研制提供新方法，有望为大飞机、高铁、航空航天及新一代智能制造装备的检测系统带来重大改变。

碳纳米管复合材料的性能尚远未达到理论预期，尤其是由于基体多采用高分子聚合物，导电性能受碳纳米管导电网络电阻蠕变的影响，利用其压阻特性实现应力长期原位检测的精度较差。本项目着重对碳纳米管/环氧树脂复合材料长期应力下电阻蠕变机理、基于长期电阻预测的应力检测蠕变补偿理论与算法、碳纳米管/环氧树脂复合材料应力长期原位检测方法以及碳纳米管/环氧树脂复合材料故障诊断与健康监测应用等进行了研究。通过拉曼光谱、电镜以及一系列的电阻蠕变实验，提出了复合材料内部导电网络是一个处于不断破坏和重建的动态平衡过程，高温下导电团聚体破坏和重组的共生效应是碳纳米管复合材料电阻率蠕变行为的主导作用机制等创新性结论；同时基于玻璃态转变温度等将复合材料热阻特性划分为三个阶段，结合各阶段电阻特性变化分析，构建了电阻蠕变的主要机理；并通过实验构建了不同工况条件下（温度、载荷）复合材料垫片长期电阻变化率预测模型。在机理研究的基础上，课题组先后开发了基于碳纳米管复合材料的智能垫片、单点柔性温度传感器、温度传感器阵列以及排针式动态应变传感器，并开展了铣削监测实验。同时基于第三阶段碳纳米管导电网络高温二次重组理论，研发了复合材料的热处理工艺，有效提升了传感器的稳定性。通过资助，项目较全面的对热固性碳纳米管复合材料长期原位监测相关问题进行了研究，在低电阻特性的材料工艺开发、温敏传感特性、动态激振力信号的原位电阻响应以及多工况下的电阻蠕变行为等方面取得了丰富的研究成果, 进一步明晰了碳纳米管复合材料电阻松弛机理与碳纳米管复合材料损伤导致的电阻变化机理，提升了复合材料原位信号检测的抗干扰能力，验证了碳纳米管复合材料原位监测与故障诊断的可行性。相关研究成果尤其是电阻蠕变机理与碳纳米管导电网络高温二次重组理论，能有效促进碳纳米管复合材料智能零件开发与原位监测技术的应用, 具有重要的社会影响和广泛的应用价值。