A nanocomposite is provided including spherical pyrogenic silica nanoparticles dispersed in a curable resin or a curing agent. The nanocomposite contains less than 2% by weight solvent and less than 0.5% by weight dispersant based on the nanoparticle weight. A composite is also provided including from about 4 to 70 weight percent of spherical pyrogenic silica nanoparticles dispersed in a cured resin, and a filler embedded in the cured resin. Optionally, the composite further contains a curing agent. Further, a method of preparing a nanoparticle-containing curable resin system is provided including mixing from 10 to 70 weight percent of aggregated spherical pyrogenic silica nanoparticles with a curable resin to form a mixture. The mixture contains less than 2% by weight solvent and less than 0.5% by weight dispersant based on the nanoparticle weight. The method also includes milling the mixture in an immersion mill containing milling media to form a milled resin system including silica nanoparticles dispersed in the curable resin.