基于γ射线辐照的碳纤维表面活性与力学性能的协同改性机制

The actual strength of carbon fibers is less than 5% of the theoretical value, and their inert surface weakens the interface adhesion with resin matrix. The conventional surface modification methods improve the surface activity of carbon fibers but sacrifice their mechanical performance. The γ-ray irradiation can not only optimize the surface features and interface adhesion of carbon fibers, but also strengthen its mechanical performance. However, the synergetic mechanisms have not been revealed, which restricts the development of irradiation modification for carbon fibers. In this project, we will characterize pristine and irradiated carbon fibers by microbeam X-ray technology and modified Raman spectrum and then investigate the changes of fiber surface, subsurface and core graphite sheet via modern analysis methods, such as the defect structure, graft and crosslink between graphite layers and crystallite size. We will investigate the respective evolution rules of surface, subsurface and core microstructure of the irradiated fibers and the effects of γ-ray irradiation on surface and mechanical properties of carbon fibers and then analyze the relationship between the surface, subsurface and core microstructure and mechanical performance of carbon fibers. The synergetic mechanisms of fiber surface modification and mechanical improvement by γ-ray irradiation will be revealed. We will pay attention to the reaction mechanisms between carbon fiber surface and irradiation medium and the influence mechanisms of γ-ray irradiation on mechanical properties of carbon fibers. The project will contribute theoretical basis and experimental base to the structure modification of carbon fibers with γ-ray irradiation, and promote the application of carbon fiber modification in aerospace composite.

碳纤维复合材料已成为制造航空飞行器的关键材料。但碳纤维强度不及理论值的5%，且表面惰性强，与树脂界面粘结不理想。常规的表面改性方法在提高碳纤维表面活性的同时容易牺牲其力学性能。γ射线辐照既能优化碳纤维表面活性，又能强化力学性能，但其协同作用机制仍不清楚，制约了碳纤维辐照改性技术的发展。本项目拟借助纤维截面Raman光谱定点扫描、X射线溅射-原位光电子能谱以及X射线微聚焦等技术手段，分别表征辐照碳纤维外表面、次表层以及芯部的缺陷、层间作用、微晶尺寸等精细结构，探讨γ射线辐照下碳纤维不同结构区域的各自演化规律及其差异，分析纤维外表面微结构与表面特性的内在关联以及外表面、次表层和芯部微结构与力学性能的耦合关系，揭示γ射线辐照对碳纤维表面改性与力学强化的协同机制。项目将为基于γ辐照的碳纤维结构改性研究提供重要的理论依据和实验基础，对推动碳纤维改性技术的发展及其在航空复合材料领域的应用具有重要意义。

γ射线辐照作为一种高效、环保和低成本的改性技术，既可以增强碳纤维本体的力学性能又可以提高纤维的表面粘结性能，受到人们的高度关注。然而，γ辐照下碳纤维表面特性以及力学性能的演化机制仍不清楚。本项目通过构建外表面、次表层和芯部的分区结构模型探讨了γ射线辐照下高强T1000和通用型T700碳纤维沿径向不同微区结构的演化规律，采用X射线光电子能谱结合原位氩离子溅射和截面Raman定点扫描技术表征辐照碳纤维外表面、次表层和芯部的精细结构演化，同时结合应力分析和机械模型定量地探讨了γ辐照下碳纤维外表面、次表层以及芯部的不同微区结构演化与其表面特性和力学性能之间的关系。结果表明，辐照介质仅对碳纤维外表面(~12nm)有重要影响，含氧官能团插层接枝到纤维外表面的石墨片层，提高了外表面活性。T1000碳纤维在氩气、空气和环氧氯丙烷中辐照处理后拉伸强度分别提高了14.7%、14.4%和12.4%，杨氏模量提高了16.4%、15.6%和13.4%。通过截面Raman测试发现，辐照后T1000碳纤维次表层ID/IG值变化比芯部更为明显，次表层(1.5μm)石墨烯片层之间共价交联结构的形成可能是辐照后碳纤维力学性能提高的主要原因。