The structural health monitoring of a mechanically attached thermal protection system

Research and development efforts are underway to provide structural health monitoring systems for future high-speed aerospace vehicles. A critical element of these vehicles is the thermal protection system (TPS). This article presents analytical and empirical results to demonstrate the feasibility of detecting loose fasteners in a TPS consisting of a carbon-carbon panel and a metallic backing structure. Analytical results show that mode shapes and resonant frequencies of the panel are functions of the fastener torque values. Empirical results from the TPS show that measured vibrational responses are useful for determining fastener failures.