Abstract The local mechanical properties of hierarchically reinforced laminates of graphene-isotactic polypropylene (iPP) and carbon fibres are investigated by nanoindentation. Carbon fibre fabrics are alternated with films of iPP reinforced with different graphene contents and types (pristine and modified with iPP brushes). The distribution of the mechanical data obtained around one isolated carbon fibre at the boundary with the polymer layer is compared with a similar analysis far away from any fibre. In the case of neat iPP, a high E′ tail can be identified with a micrometre-sized interphase showing distinct properties from those of the polymer matrix. With increasing amount of graphene, the E′ distribution including the high E′ tail progressively shifts to higher values. It is suggested that graphene platelets accumulate at the front of the ply due to the filtering effect of the carbon fibres giving rise to a transition region, superimposed on the interphase, with enhanced properties. Nanoindentation studies reveal that the chemical modification of graphene by short-chain iPP lowers the reinforcement of the nanofiller, both near and far away from the fibres front. On the other hand, indentation push-in tests suggest that modified graphene increases the resistance of the laminate under shear stress conditions. However, from the point of view of overall performance, it lowers the electrical conductivity across the laminate. The work offers a discussion of the role of graphene type and content on the properties of the multiscale composite.

中文翻译：

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石墨烯增强聚丙烯和碳纤维多尺度复合材料的纳米压痕映射

摘要 通过纳米压痕研究了石墨烯-全同立构聚丙烯 (iPP) 和碳纤维的分级增强层压板的局部机械性能。碳纤维织物与用不同石墨烯含量和类型（原始和用 iPP 刷改性）增强的 iPP 薄膜交替使用。将在聚合物层边界处的一根孤立碳纤维周围获得的机械数据分布与远离任何纤维的类似分析进行比较。在纯 iPP 的情况下，可以通过微米大小的中间相识别高 E' 尾，显示出与聚合物基质不同的特性。随着石墨烯量的增加，包括高 E' 尾的 E' 分布逐渐转移到更高的值。有人提出，由于碳纤维的过滤作用，石墨烯片层积聚在层板的前部，从而产生一个过渡区域，叠加在界面上，具有增强的性能。纳米压痕研究表明，短链 iPP 对石墨烯的化学改性降低了纳米填料的增强，无论是靠近纤维前沿还是远离纤维前沿。另一方面，压痕推入测试表明改性石墨烯增加了层压板在剪切应力条件下的电阻。然而，从整体性能的角度来看，它降低了整个层压板的导电性。这项工作讨论了石墨烯类型和含量对多尺度复合材料性能的影响。