碳纳米管和碳纤维增强的多级/多尺度复合材料力学性能研究

Carbon fiber (CF) reinforced composites are important structural materials in aerospace industries. Modifying CF composites by carbon nanotubes (CNTs) is a recent new method to improve mechanical and physical properties of CF composites, and thus represents the development direction of future light, strong and multifunctional composites with combined structural and functional performance. However, due to the complicated microstructure and multiple scale of CNT and CF reinforced hierarchical/multiscale composites, so far most studies are focused on preparation methods, without theoretical guidance or systematic experiments on their macromechanical properties. In order to fully utilize the excellent properties of CNTs in CNT/CF hierarchical composites through the meso-micro structure design, this project will develop a multiscale mesomechanics theory and multi-level/multi-scale simulation method for four types of CNT/CF hierarchical composites, i.e. carbon fiber reinforced composites with CNTs (1) modifying the fiber, (2) modifying the matrix, (3) modifying the fiber and matrix simultaneously and (4) modifying the interface between laminates, to investigate the mechanical properties and behaviors of the composites under the influences of different microscopic characteristic parameters quantitatively. Moreover, systematic experiments will also be carried out to study the influence factors on the macromechanical properties of the the CNT/CF hierarchical composites. Through feedbacks between the theories, simulations and experiments, the optimal microstructure design of the CNT/CF hierarchical composites will be made, and the guiding advice on design and preparation of CNT/CF hierarchical composite laminates can be provided, which will have significant meanings for the development and application of light, strong and multifunctional composites.

碳纤维复合材料是重要的航空航天结构材料，采用碳纳米管对其进行改性是提高其性能的新思路，代表了未来轻质、高强、多功能的结构功能一体化复合材料的发展方向。然而，由于碳纳米管/碳纤维多级复合材料具有复杂微观结构和多级尺度跨度，研究大多集中在材料制备方面的尝试，尚缺乏理论的指导和系统的宏观性能实验研究。为了通过细微观多级结构设计使碳纳米管在与纤维的协同作用中最大限度地发挥其优异力学性能，本项目将针对碳纳米管改性基体、碳纳米管改性纤维、碳纳米管同时改性基体和纤维、碳纳米管层间增韧四型多级复合材料，发展多尺度细观力学模型、建立有效的多级/多尺度计算方法定量研究各种微观特征影响下该材料的力学行为，并开展实验系统地研究各因素对其宏观力学性能的影响。通过理论、计算和实验之间的不断反馈，实现该材料的微观结构优化，从而给出对宏观碳纳米管/碳纤维复合材料设计和制备的指导性建议，加速我国功能结构复合材料的研发进程。

碳纤维复合材料是重要的航空航天结构材料，采用碳纳米管对其进行改性是提高其性能的新思路，代表了未来轻质、高强、多功能的结构功能一体化复合材料的发展方向。然而，由于碳纳米管/碳纤维多级复合材料具有复杂微观结构和多级尺度跨度，研究大多集中在材料制备方面的尝试，尚缺乏理论的指导和系统的宏观性能实验研究。为了通过细微观多级结构设计使碳纳米管在与纤维的协同作用中最大限度地发挥其优异力学性能，本项目针对碳纳米管和碳纤维增强的树脂基多级复合材料，通过细微观力学分析和原子模拟建立了理论预测模型和多级/多尺度计算方法，系统地研究了各种几何和力学参数等微观特征对复合材料宏观性能的影响规律。主要研究成果包括：1）建立了多级多尺度失效分析模型，得到了增韧效果与碳纳米管长度、碳纳米管密度、碳纳米管-碳纤维结合强度等微观参数的关系；2）首次提出了碳纳米管网络“刚度阈值”的概念，揭示了刚度阈值现象的机理，并给出了预测网络刚度的解析表达式；3）发展了一种半解析的无需假设失稳构型的二维纳米材料临界屈曲分析方法，建立了适用于不同基底材料、不同载荷情况的统一失稳准则。本项目的研究为多层级复合材料设计和优化提供了理论基础，部分研究成果已用于新型复合材料研发。本项目所发展的多级失效分析模型亦可拓展用于其他多层级材料的研究。