Novel unidirectional porous carbon/carbon composites prepared by a special designed space holder method

Abstract

Unidirectional porous carbon fiber reinforced carbon matrix (C/C) composites with different channel-diameters are fabricated for the first time by a special designed space holder method. This fabrication method involves wax soaking and curing of carbon felt preforms, prefabrication of channels, filling space-holders and removing wax, depositing carbon matrix and leaching out space-holders. Four requirements for space-holders for the fabrication of porous C/C composites are proposed, which are easy to remove, high melting point, no chemical reaction with carbon and low coefficient of thermal expansion (CTE). The space-holders developed in this study can effectively preserve the prefabricated channels during pyrocarbon (PyC) deposition. The compressive strengths of the unidirectional porous C/C composites with loading directions both parallel and perpendicular to the channels were examined. Under the present fabricating conditions, porous C/C composites with channel-diameters of 2 mm and 2.5 mm have a smooth laminar (SL) PyC matrix and demonstrate a catastrophic fracture behavior, whereas porous C/C composites with channel-diameter of 3 mm have a rough laminar (RL) PyC matrix and display a pseudo-plastic fracture behavior.