This work employed an inductively coupled plasma wind tunnel to study the dynamic oxidation mechanisms of carbon fiber reinforced SiC matrix composite (Cf/SiC) in high-enthalpy and high-speed plasmas. The results highlighted a transition of passive/active oxidations of SiC at 800–1600 °C and 1–5 kPa. Specially, the active oxidation led to the corrosion of the SiC coating and interruption of the SiO2 growth. The transition borders of active/passive oxidations were thus defined with respect to oxidation temperature and partial pressure of atomic O in the high-enthalpy and high-speed plasmas. In the transition and passive domains, the SiC dissipation was negligible. By multiple dynamic oxidations of Cf/SiC in the domains, the SiO2 thickness was not monotonously increased due to the competing mechanisms of passive oxidation of SiC and dissipation of SiO2. In addition, the mechanical properties of the SiC coating/matrix and the Cf/SiC were maintained after long-term dynamic oxidations, which suggested an excellent thermal stability of Cf/SiC serving in thermal protection systems (TPSs) of reusable hypersonic vehicles.

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Evaluation of object 3D shape change during ablation in wind tunnel test is critical for optimization of thermal protection system. However, strong thermal radiation and harsh environment bring challenges to the traditional measurement methods. A single camera DMD-projector structured laser light system is proposed for in-situ 3D shape measurement in wind tunnel test. A customized Digital Micro-Mirror Device (DMD) combined with laser source is devised for projecting concentrated full-field high-power structured light stripes. To filter laser speckle noise in projected chessboard images for model calibration, an auto-window Kuwahara adaptive filter is put forward. 3D shape of a blunt-head cylinder was in-situ measured in a plasma wind tunnel which maximum temperature reached 1950℃. Diameter reconstruction error was within 0.85% (0.17/20.03mm). With projected laser light and multi-step filters, ablation process of front face of a dome-top cylinder at 1950℃ was clearly observed at a long working distance over 1.5m.

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