A long-standing challenge in structural material design is the simultaneous attainment of high strength and toughness, a conflicting requirement rarely met in engineering materials, with important technological applications in aerospace, defense, automobile, and marine industries. Motivated from examples in biological materials, to address this challenge, we demonstrate that strong and damage-tolerant carbon-fiber-reinforced polymers (CFRPs) can be realized via the direct growth of self-assembled radially aligned graphene nanoflakes (GNFs) on carbon fibers (CFs). Here, we report a first-of-its-kind study on the dependence of strength and toughness on the surface morphology of GNFs in CFRPs. The results indicated that fracture toughness was dependent on the density and waviness of the GNFs, whereas the tensile strength was also affected by the periodicity of the coated carbon fiber layers into the laminated structures. Notably, GNFs with reduced waviness and increased number of layers exhibited enhancement in interlaminar fracture toughness for modes I and II by 93.8% and 43.3%, respectively, whereas GNFs with increased waviness led to a marginal increase or preserved tensile strength. The highly interconnected and wavy nature of GNFs facilitated effective load transfer in both in-plane and out-of-plane directions. Moreover, the out-of-plane through-volume conductivity was remarkably enhanced by 527%. The results of this work demonstrated for the first time the unique potential of GNFs, as an excellent nanoreinforcement and electrically conducting interface, for achieving simultaneously strong, tough, and conducting multifunctional CFRP composites.

中文翻译：

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用于坚韧和坚固的碳纤维环氧复合材料的径向生长的石墨烯纳米薄片

结构材料设计的一个长期挑战是同时实现高强度和韧性，这是工程材料中很少满足的相互冲突的要求，在航空航天、国防、汽车和海洋工业中具有重要的技术应用。受生物材料示例的启发，为了应对这一挑战，我们证明了通过在碳纤维上直接生长自组装径向排列石墨烯纳米薄片 (GNF) 可以实现坚固且耐损伤的碳纤维增强聚合物 (CFRP) （CF）。在这里，我们报告了关于强度和韧性对 CFRP 中 GNF 表面形态依赖性的首次研究。结果表明断裂韧性取决于 GNF 的密度和波纹度，而拉伸强度也受涂层碳纤维层进入层压结构的周期性影响。值得注意的是，波纹度降低和层数增加的 GNF 显示，I 和 II 模式的层间断裂韧性分别提高了 93.8% 和 43.3%，而波纹度增加的 GNF 导致拉伸强度略微增加或保持不变。GNF 的高度互连和波浪性质促进了平面内和平面外方向的有效载荷转移。此外，面外体积电导率显着提高了 527%。这项工作的结果首次证明了 GNF 作为一种出色的纳米增强和导电界面的独特潜力，可以同时实现坚固、坚韧、