Research on guided wave propagation characteristics of C/C thermal protection structures

Abstract

Thermal protection structures (TPS) are the key component in the design and manufacture of the reusable launch vehicle. The probability of failure of TPS in an aerodynamic thermal environment during reentry is much higher than that of ordinary structures. There is an urgent need to develop a structural health monitoring (SHM) method that can achieve rapid diagnostic for TPS to realize the high reliability and maintainability of the reusable launch vehicle. Hence, this paper aims at the typical TPS made of C/C composite material, the feasibility of SHM methods based on the active piezoelectric guided wave was studied and verified. And the propagation characteristics of guided wave in the TPS such as the multi-mode, the signal frequencies of monitoring and the effects of material anisotropy on the propagation characteristics of the guided wave were analyzed. Then, a guided wave monitoring experiment of C/C TPS with simulation damage was carried out, and the variation of a guided wave under different damage levels was analyzed from the aspects of amplitude, phase, damage scattering and damage index. The results show that the SHM methods based on active piezoelectric guided wave can effectively monitor the damage and damage expansion on the surface of C/C TPS.