Abstract In-situ characterization of the fiber/matrix interfacial failure behavior at microscopic scale is important to optimize the fiber surface treatment and to design high performance composites. In this study, in-situ tensile tests in scanning electron microscope (SEM) were used to investigate the interfacial adhesion strength of epoxy composites reinforced by four kinds of carbon fibers (CF)—raw CF, desized CF, carbon nanotube-grafted CF (CNT-CF) and oxidized CNT-CF. The crack initiation position and fracture failure mode were well recorded. The strains and the interfacial adhesion strength were obtained for these four kinds of composites. It was found that the interfacial strength decreased from 53 MPa to 48 MPa after removing the sizing on carbon fiber surface. However, by grafting CNTs on the CF surface, the interfacial strength reached 55 MPa and was further increased to 58 MPa after a simple thermal oxidation treatment. Moreover, energy dispersion X-ray analysis (EDX) was carried out using scanning transmission electron microscopy (STEM). The EDX mapping demonstrated that oxygen aggregated at the interfaces of raw CF/epoxy and oxidized CNT-CF/epoxy. Thus, a combination of CNT grafting with chemical functionalization should be necessary to achieve high performance carbon fiber reinforced polymer composites.

中文翻译：

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环氧树脂复合材料中用作增强剂的碳纤维的不同表面处理的比较：通过原位扫描电子显微镜拉伸试验测量界面强度

摘要 在微观尺度上原位表征纤维/基质界面失效行为对于优化纤维表面处理和设计高性能复合材料非常重要。本研究采用扫描电子显微镜 (SEM) 原位拉伸试验研究了四种碳纤维 (CF) 增强的环氧树脂复合材料的界面粘合强度——原始 CF、退浆 CF、碳纳米管接枝 CF ( CNT-CF) 和氧化的 CNT-CF。裂纹萌生位置和断裂失效模式被很好地记录下来。获得了这四种复合材料的应变和界面粘合强度。发现去除碳纤维表面上浆后界面强度从53 MPa下降到48 MPa。然而，通过在 CF 表面接枝碳纳米管，界面强度达到55 MPa，经过简单的热氧化处理后进一步提高到58 MPa。此外，使用扫描透射电子显微镜（STEM）进行能量色散 X 射线分析（EDX）。EDX 映射表明氧在原始 CF/环氧树脂和氧化的 CNT-CF/环氧树脂的界面处聚集。因此，为了获得高性能的碳纤维增强聚合物复合材料，需要将 CNT 接枝与化学功能化相结合。