Vibration-based damage localization in 3D sandwich panels using an irregularity detection index (IDI) based on signal processing

•The non-symmetry of the ρi,j matrix with diagonal values other than 1 indicates damage.•If the angle matrix θi,j is non-symmetric, it shows the existence of damage.•The elevated irregularity peaks in the IDI diagram indicate damaged locations.•With an increase in damage severity at a damaged location,IDImax escalates at that point, and the coordinates of irregularity peaks remain unchanged in the damaged region.•An increase in damage severity leads to a rise in IDImax only at that particular location and that of other locations remains unchanged. As 3D sandwich panels have become prevalent in construction projects, developing structural damage detection approaches is of great significance to ensure their integrity. This study aims to introduce a damage identification method to diagnose damaged regions in 3D sandwich panels using modal dynamic data. To accomplish this, an Irregularity Detection Index (IDI) is defined based on the horizontal, vertical, and diagonal detail coefficients of the wavelet analysis of an input signal consisting of primary and secondary mode shapes. The relative maximum values of irregularities on the plotted IDI signal indicate damaged locations. It is also shown that with an increase in the damage severity at a damaged location, its corresponding IDImax increases, while changes in IDImax for other undamaged locations are negligible. In fact, the detection or non-detection of a damaged location does not affect the damage localization process in other locations.