A time reversal focusing based impact imaging method and its evaluation on complex composite structures

The growing use of composite structures in aerospace structures has attracted much interest in structural health monitoring (SHM) for the localization of impact positions due to their poor impact resistance properties. The propagation mechanism and the frequency dispersion features of signals on complex composite structures are more complicated than those on simple composite plates. In this paper, a time reversal focusing based impact imaging method for impact localization of complex composite structures is proposed. A complex Shannon wavelet transform is adopted to extract frequency narrow-band signals of impact response signals of a PZT sensors array at a special time–frequency scale and to measure the phase velocity of the signals. The frequency narrow-band signals are synthesized using software, depending on the time reversal focusing principle, to generate an impact image to estimate the impact position. A demonstration system is built on a composite panel with many bolt holes and stiffeners on an aircraft wing box to validate this method. The validating results show that the method can estimate the position of impact efficiently.