In order to comprehend the influence of different “rigid-flexible” structures on the interface strength of carbon fiber(CF)/epoxy composites, CNTs was firstly chemically grafted on CFs surface, and then polyamide (PA) was grafted onto CF-CNTs surface through varying anionic polymerization time of caprolactam [CF-CNTs-PA_n (n = 6 h, 12 h, 24 h)]. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy indicated the successful establishment of CNTs and PA. TGA demonstrated the different grafting amounts of CF-CNTs-PA_n (n = 6 h, 12 h and 24 h). SEM images revealed a compactness and uniform coverage of the CNTs/PA, with increasing polymerization time, the CF and CNTs surface was covered by a thick layer of PA. The surface energy increased and then decreased. The optimal interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the CF/epoxy composites with a polymerization time of 12 h (CF-CNTs-PA_12h) was 86.7 and 85.4 MPa, which was 77.6% and 45.7% higher than that of untreated CF/epoxy composite. As the polymerization time grew, the impact toughness and tensile strength of CF/epoxy composites enhanced and conductivity of CF/epoxy composite reduced. In addition, the mechanisms of reinforcement and toughening were also illuminated. This work would provide a certain theoretical basis for the preparation and applications of high-performance CF composites with different structures.

为了理解不同的“刚柔”结构对碳纤维/环氧树脂复合材料界面强度的影响，首先将碳纳米管化学接枝到碳纤维表面，然后将聚酰胺（PA）接枝到碳纳米管表面。通过改变己内酰胺[ CF-CNTs-PA _n（n  = 6 h，12 h，24 h）]的阴离子聚合时间。X射线光电子能谱（XPS）和拉曼光谱表明成功建立了CNT和PA。TGA表明CF-CNTs-PA _n（n = 6 h，12 h和24 h）。SEM图像显示，随着聚合时间的增加，CNTs / PA的致密性和均匀覆盖度增加，CF和CNTs表面被厚厚的PA覆盖。表面能先升高后降低。聚合时间为12 h（CF-CNTs-PA _12h）的CF /环氧树脂复合材料的最佳界面剪切强度（IFSS）和层间剪切强度（ILSS））分别为86.7和85.4 MPa，分别比未处理的CF /环氧树脂复合材料高77.6％和45.7％。随着聚合时间的增加，CF /环氧树脂复合材料的冲击韧性和拉伸强度提高，CF /环氧树脂复合材料的电导率降低。此外，还阐明了增强和增韧的机理。这项工作将为不同结构的高性能CF复合材料的制备和应用提供一定的理论基础。