Design of Honeycomb-Inspired Metamaterial Skeleton for Constructing Highly Thermally Conductive Epoxy Composite

Engineering applications such as high-power electronic converters, high-voltage transmission, and aerospace are significantly attracted by high thermal conductivity electrical epoxy resin. Adding inorganic high-thermal-conductivity fillers is a traditional method to improve thermal conductivity (TC). However, excessive addition increases raw material viscosity excessively, complicates processing, and introduces defects, revealing the limitation that material properties become overly dependent on composition control. Metamaterials, with their artificially designed structural characteristics, can break through the performance limitations of traditional materials that rely on component control. Therefore, to address the aforementioned limitations, this study applies metamaterials to composite material design. With inspiration from honeycomb, we architect a 3D honeycomb metamaterial skeleton via 3D printing, enabling oriented arrangement of boron nitride (hBN) flakes within the metamaterial skeleton to yield a composite resin featuring an oriented metamaterial structure. Thus, a macroscopic skeleton network and a microscopic filler orientation are constructed to form a cross-dimensional continuous heat conduction path at a low filler content, significantly enhancing the TC at a low filler amount.Characterisation confirms that hBN exhibits highly oriented alignment within the framework. Benefiting from the oriented metamaterial structure, the composites exhibit excellent thermal conductivity and stability at low filler loadings. At the loading of 20 wt% hBN within the skeleton, the in-plane TC of the structured composites is 1.628 W m-1K-1, substantially exceeding both pure resin and control specimens (20 wt% loading, full coverage 3D printing on every layer， no skeletal structure). The surface temperature measurement demonstrates that structured materials have superior thermal management applications with high heat absorption and dissipation rates compared to pure resin and the control specimens. Thermogravimetric analysis and dynamic thermal mechanical analysis indicate that the composites have excellent heat resistance and thermal stability. This study demonstrates that the strategy of constructing oriented metamaterial skeleton composite structures via 3D printing to enhance thermal conductivity under low filler loading offers a highly promising approach for developing high-performance thermally conductive materials.