钛合金石墨烯纳米复合材料界面效应与强化机理研究

Developing Light-weight and high-strength structure materials can reduce space vehicle weight and expand its mission capability, which is a significant approach supporting the development of aerospace technologies. The major challenges and bottlenecks in developing the typical next-generation light-weight material, graphene reinforced titanium (Ti) alloy nanocomposites, are that the actual strengthening mechanisms of graphene and underlying relationship between interface effect and bulk mechanical performance remain unclear. This program proposes a combination of complementary experimental and multi-scale computational methods. The research team will perform pull-out tests on individual graphene sheets embedded within titanium alloy matrixes using an unique in situ electron microscopy nanomechanical characterization technique. The nanomechanical pull-out tests will provide direct and quantitative measurements of the interfacial load transfer capability of the graphene-titanium alloy interface. This program supports the investigation of the key mechanisms and factors influencing the efficiency of load transfer of the graphene - Ti alloy matrix and contributes towards establishing the relationship between interface properties and bulk material performance. In parallel, multi-scale computational simulations of the pull-out tests will be conducted at size-scales relevant to the experiments. The proposed simulations are composed of molecular dynamics calculations at the atomistic level, and crystal plasticity finite element simulations at the meso-scale level. The former will provide insights into the fine graphene-Ti alloy interfacial details not accessible by experiments, while the latter will be conducted at size-scales relevant to the experiments, which facilitates direct comparison of the predictions from simulations and results from experiments and will guide further experiments. The strengthening and interfacial energy transfer mechanism will also be investigated by the multi-scale computational methods. This research will contribute towards providing fundamental physical basis and establishing the technique for fabricating light-weight and high-strength graphene reinforced titanium alloy composites and promoting the development of aerospace technology in our country.

开发轻质高强结构材料，能降低飞行器重量和提升运载能力，是支撑航天技术发展的重要途径。本项目针对新型轻质结构材料钛合金石墨烯增强纳米复合材料发展的关键瓶颈和研究难点：增强机理不明确和界面特性与宏观性能的关系不清的问题，提出发展一种基于原子力显微镜探针的纳米力学测量技术和分子动力学与晶体塑性力学有限元相结合的跨尺度数值模拟方法。在实验上，通过界面纳米力学系统测量石墨烯/钛合金基体界面载荷传递能力，探索界面力学特性的影响规律，建立界面特性与宏观性能的联系；在理论上，通过建立与实验尺度相对等的多尺度计算模型（分子动力学和晶体塑性力学有限元），模拟、对比和指导实验，优化计算模型，探索复合材料的界面能量传输机制和增强机理。本研究将为制造轻质石墨烯增强钛合金复合材料提供理论支撑和技术支持，乃至支撑我国航天技术相关领域发展。

本项目针对石墨烯增强钛基纳米复合材料的界面增强机理不明确的难题，开展了基于分子动力学的界面特性以及整体性能的数值仿真与实验研究，提出了一种新型的二维材料转移技术，解决了传统石墨烯转移技术中存在的聚合物污染、转移动力不足等诸多问题；揭示了界面特性、增强机理以及界面和整体性能之间的联系，为制造轻质高强石墨烯增强钛基复合材料提供了技术支持和理论指导。.首先，提出了电场辅助液桥转移石墨烯的方法，从有限元仿真和实验的角度验证了该方法的可行性，探索了复杂电场条件下液桥转移技术过程中的工艺参数和控制方法，成功实现了单层石墨烯向金、特氟龙等基底的转移。该方法为石墨等二维材料的转移提供了新思路，为复合材料的制备提供了技术支持。.其次，建立了钛-石墨烯界面分子动力学模型，研究了不同初始界面间距、温度、不同界面结构以及不同约束对界面的影响规律，揭示了界面的粘附功和稳定性等相关特性，阐明了高温、外加载荷以及单空位缺陷等因素对界面稳定性的影响规律，为理解钛-石墨烯界面性质打下了坚实的基础。.再者，建立了单晶钛基石墨烯复合材料分子动力学模型，研究了单晶钛和石墨烯的取向对单晶钛基石墨烯复合材料的性能的影响，探究了钛层厚度、模拟温度、加载速度以及模拟尺寸等因素的影响规律，发现了拉伸过程中的石墨烯层起皱行为，阐明了单晶钛基石墨烯复合材料界面增强机理。.最后，建立了多晶钛基石墨烯复合材料分子动力学模型，探索了石墨烯位置以及石墨烯两侧的钛晶粒的取向对复合材料性能的影响规律，设计了增强型复合材料模型，探究了不同晶粒尺寸的影响规律，并揭示了多晶钛基石墨烯复合材料界面增强机理。这为多晶钛基石墨烯复合材料的设计以及实验分析提供了理论指导。