Testing SiC fiber-reinforced ZrB2 sharp component in supersonic regime

Ultra-high temperature ceramics are currently the most promising materials for thermal protection structures like wing leading edges in next generation space vehicles flying at hypersonic speed or/and re-entering the earth's atmosphere, which are characterized by sharp profiles to increase performances and maneuverability. In this contribution, the aero-dynamic behaviour of a very sharp ZrB2-SiC fiber composite is tested in a plasma wind tunnel in supersonic regime. A wedge with curvature radius of 0.1 mm was exposed to four runs in a temperature range 1400-1680°C for a total time of about 17 minutes. The wedge survived the test with minimal dimension change. The microstructural modifications induced by the hot stream were used as input values for computational fluid dynamics which furnished as output the temperature gradient along the wedge profile. Microstructural changes induced by oxidation are compared to those of a ZrB2-SiC particles ceramic machined in the same shape and exposed to similar aero-dynamic conditions. On the oxidised surface of the fiber-reinforced composite large deposits of carbon were observed due to active oxidation of SiC, which was hardly detected on ZrB2-SiC particles composites. The different way SiC fibers and particles oxidise could significantly affect the thermal conductivity and consequently the overall aero-thermal response of the composites.