Abstract The gradient modulus intermediate layer between CF and epoxy by designing double “rigid-flexible” structure using CNTs and polyamide (PA) on the CF surface was firstly established, and the effects of modulus intermediate layer on interfacial and mechanical properties of CF composites were investigated. The constructing of double “rigid-flexible” structure on the CF surface can greatly increase the polar functional groups, roughness and wettability of the CF surface as well as the thickness of intermediate layer, which could balance the modulus of fiber and resin to achieve the best matching. The interfacial shear strength (IFSS), interlaminar shear strength (ILSS), flexural strength, and impact strength of CF composites increased by 75.6%, 44.1%, 41.3%, and 34.6%, respectively. In addition, the interfacial failure behaviors and strengthening mechanisms of composites have been studied. This novel design and method built a multistage gradient modulus intermediate layer of composite with strong physicochemical interaction and good wettability, which has greatly potential for high-performance composite.

中文翻译：

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通过设计双“刚柔”结构在纤维与基体之间建立多级梯度模量中间层以改善碳纤维/树脂复合材料的界面和力学性能

摘要 通过在碳纤维表面设计碳纳米管和聚酰胺（PA）双重“刚柔”结构，首次建立了碳纤维与环氧树脂之间的梯度模量中间层，研究了模量中间层对碳纤维复合材料界面性能和力学性能的影响。调查。在CF表面构建双“刚柔”结构可以大大增加CF表面的极性官能团、粗糙度和润湿性以及中间层的厚度，可以平衡纤维和树脂的模量，实现最佳匹配。CF复合材料的界面剪切强度（IFSS）、层间剪切强度（ILSS）、弯曲强度和冲击强度分别提高了75.6%、44.1%、41.3%和34.6%。此外，研究了复合材料的界面破坏行为和强化机制。这种新颖的设计和方法构建了具有强物理化学相互作用和良好润湿性的多级梯度模量复合材料中间层，具有巨大的高性能复合材料潜力。