▎ 摘　　要

Small amounts of two-dimensional (2D) graphene sheets are usually added into a polymer matrix to fabricate nanocomposites with improved mechanical and functional properties. Further enhancements of these properties beyond those of ordinary nanocomposites require much higher loadings of well-dispersed fillers, preferably in the form of an interconnected network with the preferential orientation along the direction of interest. However, the assembly of 2D fillers to form such a three-dimensional (3D) network remains a formidable task. Herein, a totally new approach is developed to fabricate a high-density 3D multilayer graphene web with interconnected, in-plane oriented graphene struts based on the versatile chemical vapor deposition technique. The continuous high-quality graphene network within the epoxy composites leads to exceptional electrical and thermal conductivities of 50 S cm(-1) and 8.8 Wm(-1) K-1, respectively. The high filler loading of 8.3 wt% also gives rise to a remarkable fracture toughness of 2.18 MPa m(1/2), well over 100% enhancement over the neat epoxy. The simultaneous achievements of both remarkable transport properties and fracture toughness at these levels by an identical nanocomposite are unprecedented and have never been reported previously. The combination of unrivalled electrical and thermal conductivities with extraordinary fracture resistance offers the composites unique opportunities for multi-functional applications.