Three-dimensional (3D) interpenetrating network structure epoxy composites were fabricated based on the modified carbon nanotube (CNT) reinforced flexible polyurethane (PU) sponge. CNTs were first functionalized with polydopamine (PDA) as revealed by TEM imaging, which is formed via the oxidative self-polymerization of dopamine. Then the functionalized CNTs (CNT-PDA) were successfully anchored on the skeleton surfaces of sponge, forming a continuous 3D carbon network. The interfacial interaction between modified PU sponge and epoxy (EP) matrix was significantly enhanced due to the covalent linkage of PDA. Improvement in the thermal stability of CNT-PDA/PU3DIEP composites was observed by TG analysis and related to the CNTs anchored on the skeleton of sponge. The tribological properties of pure EP, PU3DIEP and CNT-PDA/PU3DIEP composites were comparatively investigated in terms of different loads and velocities. Results demonstrated that CNT-PDA/PU3DIEP composites exhibited the best tribological performance owing to the strong interfacial interaction and the 3D carbon network structure. In particular, the wear resistance of CNT-PDA/PU3DIEP composites was 6.2 times and 3 times higher than those of pure EP and PU3DIEP composites under the applied load of 1.6 MPa, respectively. (C) 2015 Elsevier B.V. All rights reserved.