Developing a Piezoelectric Active Sensor SHM System for Satellites

Structural Health Monitoring (SHM) is a valuable tool for in-service assessment of structural condition. Despite a broad use in many engineering fields, SHM has seen limited application to space systems. The paper explores specifics of SHM applied to space systems and satellites in particular. It is suggested that SHM may be considered for aiding rapid assembly of satellite components, monitoring system dynamics during launch and assessing in-service variation of structural properties suitable for model updating. In this paper, we present a discussion of factors affecting realization of the SHM system for satellites and provide recommendations for the system configuration and its practical use. The SHM system design based on a network of piezoelectric active sensors is considered. Piezoelectric sensors were selected due to availability of both active and passive operation modes. The passive SHM mode may find applications related to spaceship launch process and on-orbit structural monitoring. It is anticipated that the active structural assessment may be exercised during satellite pre-launch qualification and possible on-orbit characterization. Hence, the present contribution focuses on SHM of improperly tightened bolts as one of major satellite integrity concerns and embedded material characterization techniques. The developed SHM method utilizes the acousto-elastic effect manifested through the elastic wave phase shift caused by stress-induced localized changes in the sound speed. Experiments aimed at improving fundamental understanding of this technique are discussed and applicability of the technique to realistic structures is investigated. The methodology for in-situ material characterization is tested on structural elements of simple geometry and extension to complex structural systems is suggested. Synergistic use of the same hardware for acoustoelastic and material characterization methods is recommended and further system integration options are proposed.