低维碳基取向材料束/层网络结构的力学建模及优化设计

High-strength, lightweight materials based on carbon nanostructures hold great promise in the applications for military and civilian industry. However, some key mechanical properties of these materials are far lower than these of their building blocks. The reason is that carbon nanostructures exhibit ultrahigh specific surface area, extremely large slenderness ratio and remarkable long-range interaction, making them be apt to form networked structures of bundles/layers in fabrication and service. Mechanical modelling embedding the characteristic parameters of actual microstructures therein is the reliable foundation for material design. Therefore, this project intends to explore the correlation between networked structures and their mechanical properties in nanocarbon-based oriented materials. First, we will conduct microstructure analysis combining experimental characterization and statistical methods, and then reconstruct a multiscale numerical model of the networked structures in these materials. Second, we will develop multiscale methods covering multilevel structures therein to investigate the quantitative relationship between networked structures and their mechanical properties, and then clarify the mechanism of load transfer in multi-level networked structures. Then, a mechanical model embedding characteristic parameters of networked structures will be constructed. Finally, sensitivity analysis of mechanical model responses will be assessed to find the critical parameters for strengthening and toughening design of these materials. The outcomes of this project are expected to provide solid theoretical principles for the performance prediction and optimal design of nanocarbon-based oriented materials, and then advance efficient development of these emerging high-strength, lightweight materials.

基于碳纳米结构制备高强轻质取向材料，在军事及民用领域具有广阔的应用前景。然而，此类材料若干关键力学性能与其构筑单元相比还存在着巨大差距。这是由于碳纳米结构具有超高比表面积、超大长细比和显著的长程作用，在取向材料制备、使役过程中易于形成束/层网络结构。基于实际微结构建立力学模型是开展材料设计的基础。因此，本项目拟开展束/层网络结构与性质的关联研究。首先结合实验表征和统计方法，构建束/层网络结构的数值模型；然后开展多尺度计算模拟，获得束/层网络结构与力学性能之间的定量关系，揭示载荷在多级结构中的传递机制，进而建立嵌入微结构特征参数的力学模型；最后对模型参数开展敏感性分析，筛选对力学性能敏感的微结构参数，用于开展面向材料强韧化需求的微结构设计，以期最大限度利用碳纳米结构的优异力学特性。预期成果将为低维碳基取向材料的力学性能预测与优化设计提供坚实的理论基础，进而推动新兴高强轻质材料的高效发展。

碳纳米结构在取向材料制备过程中易于形成多级结构，亟需厘清力学性能在多级结构中的传递规律，从而最大限度利用碳纳米结构的优异力学特性。在本项目的资助下，我们结合实验表征和理论分析，研究了低维碳基取向材料多级结构的力学性能及其载荷传递机制；提出了拓扑折叠组装策略，建立了嵌入折叠结构特征参数的力学模型，发现可以通过调节折叠结构特征参数以调控材料性能；受高性能材料的结构组分特征启发，设计了高模量、高强度轻质碳管封装碳链纤维；设计筛选出多种具有优异力学性能的材料。本项目在执行过程中进展顺利，按时完成计划任务书中所规定的研究内容并达到预期目标。预期研究成果可推动低维碳基取向材料应用化和产业化发展。项目执行期间，在Journal of the Mechanics and Physics of Solids、ACS Nano等期刊共发表本项目资助号标注的SCI论文14篇 (项目负责人均为第一作者或通讯作者)。项目负责人获批主持国家自然科学基金面上项目1项。