碳纳米管网络力学性能的理论计算研究及优化

Researhcers have been seeking a way to transfer the excellent properties of CNTs in nanoscale to macro-materials. Recent studies show that Carbon nanotube (CNT) constructed network is probably an effective material structure form, so it has drawn the attention of many researchers. However, so far the CNT networks are usually studied by trial and error in numerous experiments, without theoretical guidance. In order to make the networks better inherit the excellent properties of CNTs through the network microstructure design, this project will develop a mesomechanics theory suitable for the CNT networks with and without matrix, which are two usual forms in the engineering applications of the CNT networks. This theoretical model will take into account the influences of inter-tube effects, matrix, interface and CNT geometrical characteristics comprehensively, and predict the optimal design of the CNT networks for their mechanical properties. This project will also develop a multi-level/multi-scale simulation method to investigate the mechanical properties and behaviors of the networks under the influences of different microscopic characteristic parameters quantitatively. Furthermore, some experiments will also be carried out in this project to validate and support the theoretical analysis and numerical simulation. Through feedbacks between the theories, simulations and experiments, the optimal microstructure design of the CNT networks will be made, and the guiding advice on design and preparation of macro-materials of CNTs can be provided, which will have significant meanings for the development and application of CNT materials. The theoretical and numerical methods developed in this project are expected to extend to the structure optimization of other fiber constructed networks as well.

研究者一直在探寻如何将碳纳米管在纳米尺度的优良性能传递到宏观材料，最近的研究显示碳纳米管网络很可能是一种有效的组织形式，因此备受关注。然而，目前对这种网络结构的研究大多集中在实验尝试，尚缺乏理论的指导。为了通过网络结构设计使碳纳米管网络更好地继承碳纳米管的优异性能，本项目将针对工程实际中常见的有基体和无基体两种碳纳米管网络，综合考虑管间作用、基体、界面、碳纳米管的几何特征等因素对网络结构宏观性能的影响，发展适合于碳纳米管网络的细观力学模型对其力学性能进行优化；并建立有效的多级/多尺度计算平台定量研究各种微观特征参量影响下的碳纳米管网络的性能和行为。此外，还将进行部分实验来检验和支持理论和计算方法，通过相互之间的不断反馈，实现碳纳米管网络的结构优化，从而给出对宏观碳纳米管材料设计和制备的指导性建议，加速碳纳米管材料的应用开发。本项目所得到的理论和计算方法亦可拓展用于其它纤维网络的结构优化。

研究者一直在探寻如何将碳纳米管在纳米尺度的优良性能传递到宏观材料，最近的研究显示碳纳米管网络很可能是一种有效的组织形式，因此备受关注。然而，目前对这种网络结构的研究大多集中在实验尝试，尚缺乏理论的指导。为了通过网络结构设计使碳纳米管网络更好地继承碳纳米管的优异性能，本项目针对工程实际中常见的有基体和无基体两种碳纳米管网络，综合考虑管间作用、基体、界面、碳纳米管的几何特征等因素对网络结构宏观性能的影响，发展了适合于碳纳米管网络的细观力学模型对其力学性能进行优化；并建立了有效的多级/多尺度计算平台定量研究各种微观特征参量影响下的碳纳米管网络的性能和行为。对于无基体的随机分布碳纳米管网络，揭示了其刚度阈值和弯-拉转变阈值的存在，并通过稳定率和缺陷率揭示了上述阈值的机理，进而建立了预测整体网络刚度的解析表达式，该表达式表明，碳纳米管网络的相对刚度仅与其相对密度及碳纳米管的长细比有关。对于有基体的碳纳米管网络，即碳纳米管复合材料，研究了碳纳米管本身的几何参数对整体复合材料力学性能的影响，发现对于直径为纳米尺度的纤维类复合材料，并不一定越细越好。最优的碳纳米管直径可由碳纳米管、基体和界面的参数解析地给出。本项目的研究提供了对宏观碳纳米管材料设计和制备的指导性建议，有助于加速碳纳米管材料的应用开发。本项目所得到的理论和计算方法亦可拓展用于其它纤维网络的结构优化。