碳纳米组元复合构筑碳纤维复合材料界面层及其界面强化机制

Extensive research and development were focused on the carbon fiber surface modification in recent years. Introducing nanomaterials into the interphase of composites was particularly designed for preparing high performance composite. But lacking of control methods for the size distribution and spatial arranged of nano-components in the interphase was resulted in limits enhancement effect and further play of reinforcement effects. In the project, based on the carbon fiber/epoxy composites, the GO and the Aligned-CNTs ,which has the same composition and similar structure with the carbon fiber, was adopted for improving and enhancing the interfacial strength of the composites simultaneously. The new hierarchical reinforcement CF-GO-CNTs were prepared through chemical modification and grafting carbon nanotubes onto the carbon fiber surface using graphene oxide as the linkage. The influence of the grafting density and length and functional groups on the surface appearance and properties of the carbon fiber was researched. The reinforcing mechanisms were also discussed by studying the wettability between fibers and matrix, the interfacial chemical reactions of the functional groups of fiber surface and resin matrix, interfacial mechanical interlocking. It is of great significance to maximize the performance of the composite by determining the interface region of the optimization criterion and research of the project will provide new ideas of ultimately improving the performance of advanced polymer matrix composites.

将纳米组元引入到复合材料界面以调控界面层是近年来制备高性能复合材料的研究热点和有力手段，但由于纳米组元在界面中尺寸分布、空间排列缺乏有力的控制，使得其对界面增强效果有限，难以充分发挥纳米组元的强化效应。本项目将采用与碳纤维具有相同的成分和相似的结构氧化石墨烯GO和特定碳纳米管Aligned-CNTs，通过化学修饰和接枝技术在纤维表面进行调控，构建CF-GO-CNTs复合纳米结构。通过对GO的尺寸控制、空间取向、官能团调控，制备出Aligned-CNTs分布可控、反应可控的多尺度复合增强体，研究多尺度接枝形成的模量梯度对纤维表面状态和性能的影响规律。进而从纤维与树脂的浸润性、纤维与树脂的界面化学反应、纤维与树脂的界面机械啮合等方面研究不用纳米结构对界面性能的影响规律，探讨界面相结构对复合材料性能的作用机理，为制备新型高性能碳纤维复合材料及建立高效的复合材料界面控制技术奠定实验和理论基础。

碳纤维（CF）表面状态（形貌、结构、反应性）影响着复合材料界面相结构，是提高复合材料性能的关键因素之一。氧化石墨烯（GO）和碳纳米管（CNTs）具有独特的结构和优越的性能，是近年来用于增强增韧碳纤维复合材料的主要纳米材料。通过在碳纤维表面同时接枝氧化石墨烯和碳纳米管,得到新型CF-GO-CNTs改性体，借此将GO和CNTs引入到复合材料界面微区。.(1) 对碳纤维表面进行预处理，调整碳纤维表面的活化官能团，增加反应活性点。碳纤维表面元素C1s, O1s, N1s, Cl2p和 Si1s的含量分别是76.38 %, 15.38 %, 3.89 %, 0.41 %, 3.54 %。抽提处理后碳纤维表面的元素C1s,的含量提高到90.56 %，氧元素的含量仅仅为4.79 %。氧化处理的碳纤维表面的氧元素含量得以大幅度的提高，为21.49 %，碳元素的含量降低为74.33 %。原丝的单丝强度为3.20 GPa，抽提处理的碳纤维的单丝强度有所下降（3.15 GPa）。氧化处理的碳纤维CF-COOH的单丝强度为 2.98 GPa，酰氯化处理的碳纤维CF-COCl的单丝强度仅为 2.94 GPa。.(2) 引入GO和CNTs的碳纤维表面变得粗糙，除浆碳纤维比表面的1.92 m2/g，CF-GO为30.44 m2/g，CF-GO-CNTs为64.93m2/g。3420 cm−1 (O-H)、1570 cm-1 (C=O)、1180 cm-1 (环氧基)等特征峰证实了GO接枝到碳纤维表面。特征峰3430 cm-1、1540 cm-1(-NH2)，1650 cm-1(-N-C=O)和2950 cm-1(CH2)表明CF-GO接枝了CNTs。CF-GO表面的碳元素含量降低到81.82%，氧、氮、氯的含量从原丝的8.76%, 1.46%, 0.21%分别增加到11.94%, 2.55%, 1.35%。CF-GO-CNTs表面的氧、氮含量分别为14.83% 和4.76%。相比除浆碳纤维的复合材料，CF-GO复合材料、CF-GO-CNTs复合材料的界面结合性能分别提高了28.29%，48.12%。CNTs及GO同时引入到纤维表面，增大了纤维与基体相的接触面积并且CNTs及GO表面的官能团与树脂反应，增加了与基体树脂的机械锚钉和化学键结合作用，提高了碳纤维复合材料整体的力学性能。