Systems and methods for the preparation of reinforcements for composite materials, whereby single- and/or multi-walled carbon nanotubes (CNTs) may be electrophoretically deposited on fibrous substrates for the production of hybrid CNT/fibers. The fibers may include carbon fibers and woven carbon fabrics. The length, as well as the density and orientation of the deposited nanotubes on the fiber surfaces may also be tailored. The strength of the CNT/fiber-matrix interface formed in composites fabricated from the hybrid CNT/fibers may be adjusted by introduction of functional groups on the CNT/fiber surfaces, such as aminophenyl and carboxyphenyl groups.