Preform separators are operative to separate porous preforms that undergo chemical vapor integration and deposition (CVI/CVD) to form components such as carbon-carbon composite disc brake rotors. The exemplary preform separators are comprised of thin sheets of organic fibers separated by layers containing adhesives and other materials. Bodies comprised of the plurality of thin sheets and layers undergo carbonization at a controlled rate in a non-oxidizing atmosphere. The preform separators have flat planar opposed side faces which abut porous preforms during the CVI/CVD process. Exemplary separators include channels that facilitate the infiltration of carbon carrying gas into the preforms to aid in densification. The preform separators are reusable in a plurality of densification cycles and have non-stick properties.