Abstract
Structural health monitoring (SHM) technology is a reliable, efficient and economical approach to increase the safety and reduce the maintenance cost of high performance structures. Among the existing SHM methods, piezoelectric transducers (PZTs) array and Lamb wave based SHM methods are sensitive to small damage and studied by many researchers. In this paper, aiming at developing a practical method for on-line localization of damage and impact on aircraft composite structure which can take advantage of time reversal focusing and does not rely on the transfer function, a phase synthesis based time reversal focusing method is proposed and a twin-PZTs array arrangement based damage imaging method is discussed first. In this method, damage and impact images are given out directly through time reversal focusing and the other imaging processes such as the delay-and-sum imaging method adopted in many researches of time reversal focusing are not needed. And then, a kind of PZTs smart layer (PSL) with electromagnetic shielding is developed. For real application of SHM, an integrated multi-channel scanning system (ISS) with impact and damage monitoring function is developed thirdly. The ISS can scan large numbers of actuator-sensor channels and estimate impact and damage automatically. Finally, A SHM demonstration system is built on a carbon fiber composite panel with many bolt holes and stiffeners of an aircraft wing box based on the damage and impact imaging method, the PSL and the ISS. The demonstrating results show good performance of the whole SHM system.