Fabrication and plasma wind tunnel testing of UHTC structures

The ultra-high-temperature ceramics (UHTCs) are currently the most studied key enabling technology for thermal protection structures (TPS) like wing leading edges, surface control components to be applied in the next generations of space vehicles flying at hypersonic speed or/and re-entering the Earth's atmosphere. They are characterized by sharp profiles to increase performances and maneuvrability. In the present contribution, technological demonstrators with a sharp profile were produced in the system ZrB2-SiC by hot-pressing and further shaping by EDM/mechanical machining. SiC was introduced in the form of particulate or short fibres.In both cases, the dynamic response to oxidation of such pointed UHTC demonstrators was studied under aero-thermal heating using a high enthalpy supersonic flow of a N2/O2 gas mixture in plasma wind tunnel. Microstructural features of the reaction scale developed upon oxidation were analyzed and correlated to test conditions through Computational Fluid Dynamics simulations. The significant heat flux and temperature gradients of the sample's surface exposed to the highly energized N2/O2 gas stream led to the formation and evolution of distinct layered oxide sub-scales. The outputs of CFD simulations, that are essential to model the test conditions of the free-stream and boundary layer, matched the in-situ determinations and material evolution during arc-jet testing