Experimental method based on guided wave for ablation monitoring of C/C thermal protection structures

Abstract

Thermal Protection Structures (TPS), as a key part of the design and manufacture of reusable aircraft, are prone to damage under the coupling of high-temperature and complex aerodynamic loads, which may lead to the overall failure of structures. The Guided Wave (GW) based Structural Health Monitoring (SHM) is a promising method because it has large monitoring area and is sensitive to small damage. However, there are few relevant researches on GW monitoring methods for TPS ablation. Aiming at this problem, taking the TPS made of Carbon/Carbon (C/C) composite as the research object, an experimental method based on GW for TPS ablation monitoring of reusable aircraft is proposed. Real ablation is applied via the oxygen-acetylene airflow above 2000°C. The influence of ablation on guided waves is studied by comparing the variations of amplitude and phase velocity of the GW before and after ablation. The results show that GW is sensitive to the ablation of C/C TPS, and ablation leads to the increase of amplitude and phase delay. The ablation degrees can be characterized by damage indices, which verifies the feasibility of the ablation monitoring method for C/C TPS.