超长碳纳米管及管束力学性能的实验研究

Single ultra-long carbon nanotubes have low defect densities and can be up to centimeters or even decimeters in length, thus, they have great advantages in terms of basic materials in advanced fields such as super-fiber, ballistic armor, and aerospace (lightweight, high temperature). Therefore, it is important to study the room temperature and high temperature mechanical properties of ultra-long carbon nanotubes/tube bundles. However, due to the limited measurement ranges and simple functionality, conventional micro- and nanoscale devices are difficult to realize the mechanical characterization of such ultra-high aspect ratio materials. Accordingly, this paper proposes an optical microscope (OM) based material testing system, which is suitable for ultra-long one-dimensional materials, with the characteristics of real-time observation, controllable environment, real-time acquisition of temperature and load signals. The high temperature mechanical properties of ultra-long carbon nanotubes/tube bundles were measured for the first time, revealing the weakening mechanism and fatigue failure mechanism. Moreover, the direct measurement of the interwall interaction force of ultra-long carbon nanotubes was realized, and combined with numerical simulations, the mechanism of load transfer and interaction between walls and tube bundles was revealed. This project is of great significance for the use of ultra-long carbon nanotubes as a macroscopic ultra-low friction and interaction research platform, as well as the design and manufacture of carbon nanotube fibers and composite materials. At the same time, it provides an important guide for the application of ultra-long carbon nanotubes as engineering materials.

超长碳纳米管由于具有较低缺陷密度，长度可达厘米甚至分米级，在超强纤维、弹道装甲、航天航空（轻量化、耐高温）等尖端领域基础材料方面具有巨大的优势。因此，研究超长碳纳米管/管束的室温与高温力学性能具有重要意义。然而，以往的微纳米测量装置由于有限的测量范围和单一功能，难以实现这一超高长细比材料的力学表征。基于此，本项目发展了适用于超长一维材料的力学性能测量系统，使其具有可实时观测、可控环境、实时采集温度与载荷信号等特点。首次实现了超长碳纳米管/管束的高温力学性能测量，揭示其高温力学性能的弱化机制、疲劳失效机理。首次实现了超长碳纳米管壁间/管间相互作用力的直接测量，并结合数值计算，揭示壁间和管束管间的载荷传递与相互作用机理。本项目研究对于将超长碳纳米管作为宏观超低摩擦与相互作用研究平台，以及对碳纳米管纤维、复合材料的设计与制造具有重要意义，同时对于将超长碳纳米管作为工程材料应用提供重要指导。

超长碳纳米管由于单根长度可达厘米量级且具有缺陷密度低、轻量高强等特点，在超强纤维、弹道装甲等尖端材料方面具有巨大的优势，研究超长碳纳米管/管束的力学性能具有重要意义。本项目建立了适用于超长一维材料的力学性能测量系统，研究了适用于单根超长碳纳米管及管束的力学性能测量方法；实现了超长碳纳米管及管束的原位拉伸测量，以及超长碳纳米管/管束的壁间/管间相互作用力测量，获得了不同长度超长碳纳米管与管束的相关力学性能参数，以及管壁间和管束中碳管间的相互作用力；建立了管壁间相互作用多尺度计算模型和超长碳纳米管在横向载荷下拔出力的理论模型，开展了超长碳纳米管管壁间相互作用的多尺度分析，发现拔出力由边界相互作用、动摩擦、接触区构型力三部分组成，较短碳纳米管的拔出力仅与边界相互作用相关，而超长碳纳米管在拔出速度较高时，其动摩擦作用与边界相互作用相当。本项目研究结果对超长碳纳米管管壁间相互作用机理、纳米界面相互作用机制有新的理解，可为超低摩擦器件的设计提供参考。