A composite material including an arrangement of approximately aligned nanofilaments overlying at least another arrangement of approximately aligned nanofilaments, the longitudinal axis of the nanotubes of the first arrangement being approximately perpendicular to the longitudinal axis of the nanotubes of the other arrangement, and the arrangements forming at least one array. A resin material having nanoparticles dispersed throughout is disposed among the array(s) of nanofilaments, and cured, and openings may be formed into or through the composite material corresponding to spaces provided in the array of nanofilaments. A composite material according to embodiments forms a microelectronic substrate or some portion thereof, such as a substrate core.