The extremely low thickness-to-length ratio (aspect ratio) of graphene nanofillers has long been considered beneficial to the overall thermal conductivity of graphene-polymer nanocomposites as it creates large surface area and extra channels for phonon transport. From time to time, however, a lower aspect ratio of the nanofillers did not yield a higher thermal conductivity as expected. To explain such phenomena, we explored the dual role played by the aspect ratio of graphene nanofillers in the effective thermal conductivity via an effective-medium approximation based on Maxwell's far-field matching with consideration of imperfect graphene interfaces. On one hand, we found that the initiation of the graphene thermal networks relies solely on the aspect ratio. A lower aspect ratio tends to boost the establishment of the thermal channels. On the other, we discovered a persistent exponential law that relates the graphene interfacial thermal coefficient to the aspect ratio regardless of the matrix material. A lower aspect ratio causes a higher interfacial thermal resistance, thus a possible lower effective thermal conductivity. These two effects are competing against each other in the framework of this theory. The origin of the second effect was discussed and the effect cannot be neglected with an aspect ratio below 0.01. This dual-role theory was confirmed by a large number of experimental observations.

长期以来，石墨烯纳米填料的极低的厚度与长度之比（长宽比）一直被认为有利于石墨烯-聚合物纳米复合材料的整体热导率，因为它会产生较大的表面积和额外的声子传输通道。然而，不时地，较低的纳米填料的长径比没有产生预期的较高的热导率。为了解释这种现象，我们通过考虑不完全石墨烯界面的麦克斯韦远场匹配，通过有效介质近似，探索了石墨烯纳米填料的纵横比在有效导热率中的双重作用。一方面，我们发现石墨烯热网络的引发仅取决于长宽比。较低的宽高比倾向于促进热通道的建立。另一方面，我们发现了一种持久的指数规律，该规律将石墨烯界面热系数与纵横比相关，而与基质材料无关。较低的纵横比会导致较高的界面热阻，因此可能会导致较低的有效导热率。在此理论的框架内，这两种效应相互竞争。讨论了第二种效果的起源，并且在宽高比低于0.01时不能忽略该效果。大量实验观察证实了这种双重角色理论。在此理论的框架内，这两种效应相互竞争。讨论了第二种效果的起源，并且在宽高比小于0.01时不能忽略该效果。大量的实验观察证实了这种双重角色理论。在此理论的框架内，这两种效应相互竞争。讨论了第二种效果的起源，并且在宽高比小于0.01时不能忽略该效果。大量实验观察证实了这种双重角色理论。