Carbon nanomaterials (e.g., carbon nanotubes and graphene) have been deemed as versatile building blocks to create a novel generation of nanocomposites desired for a variety of commercial applications. Different from that of the conventional fiber-based composites, the enormous interfacial areas, van der Waals forces dominated interface interactions as well as multiple scale load transfer mechanism would greatly impact the mechanical behaviors of carbon nanomaterials-based composites. Besides the widely concerned nanofiller-matrix interface, the filler-filler interface has to be considered in nanocomposites. The main challenge is how to monitor the load transfer process and evaluate load-bearing capability of fillers in composites. Here, we summarize the recent progress in experimental characterization of atomic-scale interface mechanics, and clarify its importance on the reinforcement of nanocomposites. We also highlight the significance of competed mechanism between intrinsic mechanical strength of nanofillers and interfacial shear effect, allowing the delicate design of nanocomposites that deliver desired properties.

碳纳米材料（例如，碳纳米管和石墨烯）已被认为是通用的基础材料，可以创造出新一代的纳米复合材料，可满足各种商业应用的需求。与常规的纤维基复合材料不同，巨大的界面面积，范德华力主导的界面相互作用以及多尺度载荷传递机制将极大地影响碳纳米材料基复合材料的机械性能。除了广泛关注的纳米填料-基质界面之外，还必须在纳米复合材料中考虑填料-填料界面。主要的挑战是如何监控载荷传递过程并评估复合材料中填料的承载能力。在这里，我们总结了原子级界面力学实验表征的最新进展，并阐明其对增强纳米复合材料的重要性。我们还强调了纳米填料的固有机械强度与界面剪切效应之间竞争机制的重要性，从而使纳米复合材料能够提供所需特性的精细设计。