石墨烯/聚合物纳米复合材料微纳界面力学性能测量与增强机理研究

Polymer nanocomposites show substantial property enhancements at much lower filler component weight as compared to conventional polymer composites. Graphene has been considered an ideal candidate for reinforcing additives in polymers due to its high stiffness and strength. The strength characteristics of graphene-polymer interfaces play critical roles in the bulk mechanical response of graphene-based nanocomposites. However, there is a lack of fundamental understanding of strength properties of graphene-polymer interfaces. Yet, the complex nanoscale phenomena occurring during shear deformation associated with the pull-out of graphene from the polymer matrix are not well understood. This research award supports investigations of deformation, load transfer and failure of graphene-polymer interfaces at the nanoscale. A combination of complementary experimental and computational methods is employed. The research team will perform pull-out tests on individual graphene sheets embedded within polymer matrixes using an unique in-situ nanomechanical characterization technique. The nanomechanical pull-out experiments will provide direct and quantitative measurements of the interfacial strength properties. In parallel, molecular dynamics simulations of the pull-out tests will be conducted at size-scales relevant to the experiments. This complementary approach facilitates comparison between the results of experiments and simulations. The simulations will provide insights into the fine graphene-polymer interfacial details not accessible by experiments, and will guide further experiments. This complementary experimental and computational effort will provide mechanistic understanding of the nanoscale interfacial strengthening processes, and decipher the roles of the size and morphology of the embedded graphene on the mechanical strength of graphene-polymer interfaces. This research will contribute towards achieving light, strong, and tough polymer nanocomposite materials.

石墨烯由于其独特的材料性能被认为是聚合物复合材料中理想的填充材料。石墨烯与聚合物之间的界面力学特性决定了石墨烯/聚合物纳米复合材料的宏观性能。如何构筑高强度界面是制约石墨烯/聚合物纳米复合材料发展的关键瓶颈。然而，其界面力学特性和增强机理的探索还刚刚起步，有待于深入研究。为此，本项目提出运用纳米力学测量系统与计算模拟相结合的研究方法，深入探索在纳米尺度下的界面变形、载荷传递和破坏等力学特性与内在机理。本项目提出发展一种纳米尺度的界面力学特性原位测量技术，通过实施拉拔方法，直观、定量的实现界面力学特性的动态测量和表征问题。针对界面增强机理不明的难题，本项目提出建立相等尺度的分子动力学模型，通过模拟拉拔方法，从更深层次揭示聚合物分子与石墨烯界面增强的内在机理，同时交叉对比模拟和实验数据，验证分子模型并指导实验。本研究将为制造更轻、更强的纳米复合材料提供理论支撑和技术支持。

本项目针对目前出现的石墨烯/聚合物纳米复合材料界面性能影响因素研究不够系统全面，整体力学性能微观增强机理不明确等问题，基于分子动力学方法，在全原子体系中系统研究石墨烯化学改性以及石墨烯二维几何形状对石墨烯/聚甲基丙烯酸甲酯复合材料界面性能的影响；采用粗粒化技术研究石墨烯/聚合物珍珠层仿生结构中石墨烯形状、重叠距离、层数、层间厚度等因素对复合材料界面及整体性能的影响，解决了高性能纳米复合材料增强机理不明的难题，形成独立自主的知识产权。.首先，研究了石墨烯化学改性对界面力学性能的影响规律。发现羧基对界面的增强效果最强，甲基最弱；官能团浓度越大增强效果越明显，但存在临界浓度；缺陷直径大于10.6Å时对界面有增强效果。其次，研究了石墨烯几何形状对界面力学性能的影响规律。建立了不同几何形状石墨烯/聚合物界面载荷传递模型, 阐释了不同几何形状石墨烯的界面增强机理。研究发现梯形和锯齿形石墨烯对界面的增强效果强于矩形石墨烯。然后，采用粗粒化技术，研究了石墨烯形状及排布方式对复合材料界面及整体力学性能的影响规律。研究发现改变石墨烯排布方式（如增加石墨烯间重叠距离等）可以提升复合材料整体力学性能，改变石墨烯形状对于复合材料的抗拉伸性能、抗冲击、抗弯曲性能产生不同的影响效果，为仿珍珠层石墨烯复合材料的设计提供理论支持。.本项目提出了一种电场驱动微流填充的纤维/聚合物界面增强技术，该技术通过外加电场驱动纤维表面树脂流动，填充碳纤维表面的微沟槽，从而改变其浸润状态，使得树脂能够在流动过程中实现对纤维粗糙表面的随形贴合，提高界面接触面积，形成有效的机械啮合，有效提高复合材料界面剪切强度。该技术有效改变碳纤维复合材料的界面性能，可广泛应用于两相界面的增强，为制造高性能复合材料提供了可行的制造方法。