Improved Pseudo excitation method for damage localization in lattice sandwich structures via periodic interference suppression

Lattice sandwich structures are increasingly utilized in aerospace, automotive, and civil engineering applications owing to their high specific strength, stiffness, and exceptional multifunctional capabilities. However, their enclosed architecture and heterogeneous cores pose significant challenges for damage detection, as conventional vibration-based or ultrasonic-based methods fail to cope with the structural complexity. While Pseudo Excitation (PE) method enables localized damage detection by analyzing local dynamic equilibrium conditions and shows promise for complex structures, its application to lattice sandwich structures is hindered by periodic discontinuities at the joints between the face sheets and sandwich core, significantly impairing detection accuracy. To overcome this limitation, this study proposes an improved PE approach that incorporates a periodic interference suppression method based on Fourier filtering. Theoretical analyses first reveal that the interference from connecting joints exhibits predictable periodic patterns linked to the unit cell configurations. By mathematically modeling these periodic perturbations, the method effectively separates actual damage-induced signals from noises due to the periodic lattices. Numerical simulations demonstrate that periodic interference can be explicitly modeled and effectively suppressed using Fourier filtering, leading to successful damage detection across different excitation frequencies, unit cell sizes, and boundary conditions. Experimental verification is further conducted using a laser doppler vibrometer (LDV), which scans the vibration field of a damaged lattice structure and successfully pinpoints the damage location. The proposed method not only maintains the inherent advantages of the PE method, but also extends its applicability to complex lattice sandwich structures, paving the way for its real engineering applications.