Abstract: Methods of making a carbon-carbon composite structure with internal microchannels include (i) assembling a dry carbon fiber composite preform with a sacrificial template woven or placed within to form a primary assembly; (ii) placing the primary assembly under a sealed enclosure; (iii) applying a vacuum to the sealed enclosure to evacuate air from the dry carbon fiber composite preform; (iv) infusing a polymer resin into the dry carbon fiber composite preform to generate a resin infused preform; (v) heating the resin infused preform under vacuum to cure the polymer resin in the resin infused preform to form a cured composite; (vi) demolding the cured composite; and (vii) heating the cured composite to an elevated temperature of at least 800° C. under a flow of an inert gas to decompose the sacrificial template to form the internal microchannels and carbonize the cured composite to form the carbon-carbon composite structure.