Fabrication and Characterization of C/C-SiC Material made with Pitch-Based Carbon Fibers

Abstract

During atmospheric re-entry high thermal loads are generated on the surface of the entry vehicle with peak loads in the stagnation area. Typical entry vehicles have a blunt shape avoiding sharp tips or leading edges because the heat load increases with a decreasing curvature radius of the surface structure. Recent developments for vehicles in the hypersonic flight regime have concentrated on sharp designs to reduce drag and increase lift. This creates challenges with regard to the materials used for the tip or leading edge of the vehicle. Ceramic matrix composites are materials with good high-temperature properties, however, the thermal loads on sharp structures can exceed even their capabilities. One way to relieve the problem could be to use a material at the structure tip with a very high thermal conductivity to distribute the heat load over a wider area and thereby reducing the temperature to an acceptable level. In this work a C/C-SiC ceramic matrix composite made with pitch carbon fibers was fabricated and characterized. Different types of pitch carbon fibers were procured and sample plates were manufactured. The thermally relevant properties were measured as there are thermal diffusivity, density and specific heat capacity and with that the thermal conductivity was calculated. In addition basic mechanical properties were measured to evaluate the material from a structural point of view.