In this study, electrospun glass (structurally amorphous SiO2) nanofibers (EGNFs) with diameters of similar to 400 nm were incorporated into epoxy resin for reinforcement and/or toughening purposes; the effects of silanization treatment (including different functional groups in silane molecules) and mass fraction of EGNFs on strength, stiffness, and toughness of the resulting nano-epoxy composite resins were investigated. The experimental results revealed that EGNFs substantially outperformed conventional glass fibers (CGFs, with diameters of similar to 10 mu m) in both tension and impact tests, and led to the same trend of improvements in strength, stiffness, and toughness at small mass fractions of 0.5 and 1%. The tensile strength, Young's modulus, work of fracture, and impact strength of the nano-epoxy composite resins with EGNFs were improved by up to 40, 201, 67, and 363%, respectively. In general, the silanized EGNFs with epoxy end groups (G-EGNFs) showed a higher degree of toughening effect, while the silanized EGNFs with amine end groups (A-EGNFs) showed a higher degree of reinforcement effect. The study suggested that electrospun glass nanofibers could be used as reinforcement and/or toughening agent for making innovative nano-epoxy composite resins, which would be further used for the development of high-performance polymer composites. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012