Durability of 3-D Woven Si-Ti-C-O Fiber/Si-Ti-C-O Matrix Composite Evaluated by Arc Jet Test.

Abstract

Durability of 3-D woven Si-Ti-C-O fiber/Si-Ti-C-O matrix composites with and without glass sealant was evaluated by an arc jet facility (arc wind tunnel). The surface temperature of the composite during arc jet test was far lower than the temperature predicted by a numerical calculation. This was due to high temperature gas flow through large pores arising from the 3-D fabric configuration. Rapid temperature rise was observed around large pores in the composite without glass sealant under high heat flux condition. On the other hand, the phenomenon was not observed in the glass sealed composite. Thus, the glass sealant was effective for the stable aerodynamic heating on the composite surface. The surface of glass sealed composite was uniformly covered by a silica layer formed by crystallization of the glass sealant material during arc jet test. The silica layer might prevent the composite surface from oxidation. Surface recession was hardly recognized bellow 1450°C at surface temperature and above 5kPa in oxygen partial pressure at the stagnation point, because passive oxidation was dominant under the heating condition. Passive/active oxidation boundary of the composite agreed with the Balat's theory for silicon carbide under the present experimental condition. Mass loss was observed just above 1500°C, which was due to decomposition of Si-Ti-C-O fiber and matrix.