Experimental research on online monitoring of high temperature and high speed airflow ablation of quartz ceramic thermal protection structure using guided wave

Thermal protection structure (TPS) plays a key role in protecting hypersonic flight vehicles from harsh service environment and has been widely used. As a common ablative thermal protection material, quartz ceramic TPS realizes thermal insulation by generating ablation during the reentry phases. The structural state of quartz ceramic TPS therefore is of great importance to the service performance and safety of hypersonic flight vehicles, and shows an urgent need for structural health monitoring (SHM). However, the monitoring of real ablation of quartz ceramic structure is barely considered in the current study, let alone online monitoring under harsh service environment, which brings a great challenge to the implementation of reliable ablation monitoring. Aiming at online ablation monitoring of quartz ceramic structure, this paper performs experimental research by taking advantage of guided wave (GW)-based monitoring method. An ablation experiment and monitoring system is built to generate real ablation under high temperature and high speed airflow and perform GW monitoring. The maximal temperature of the system can reach about 2100 °C. The feasibility of ablation monitoring is verified by analyzing ablation-induced influence on GW signals. Gaussian mixture model (GMM) is adopted to combine with GW method to suppress the high temperature variation caused by uncertainty influence on GW signals during the ablation process, so that reliable monitoring of ablation can be realized. Experimental results show that online monitoring of ablation propagation of quartz ceramic structure under high temperature variation is achieved, which can be further used for ablation quantification evaluation.