The effect of temperature on guided wave signal characteristics in presence of disbond and delamination for health monitoring of a honeycomb composite sandwich structure with built-in PZT network

Guided wave (GW) based structural health monitoring (SHM) techniques being developed by researchers frequently use amplitude and group velocity variations between healthy and damage-affected GW modes to detect and localise damage. Nonetheless, external variables such as temperature and moisture influence these features, which were not considered in previous studies, particularly in the presence of damage in honeycomb composite sandwich structures (HCSSs). Therefore, a coordinated numerical and experimental study was carried out in an effort to examine the characteristics of GW propagation in an HCSS for two damages: a disbond between the face sheet and the core, and delamination between the face sheet layers for a temperature range of 0 ^∘C–90 ^∘C. Computationally efficient two-dimensional numerical models were developed using COMSOL Multiphysics that takes into account a variety of temperature-related phenomena, such as thermal stresses and changes in the material properties of honeycomb sandwich and piezoelectric wafer transducers (PZTs). The amplitude and group velocity of the fundamental anti-symmetric (A0) mode are found to increase in the presence of a disbond and decrease in the presence of face sheet delamination. However, it is observed that there is a linear decrease in the amplitude of A0 mode for both the healthy and damaged cases with an increase in temperature. Since the A0 mode is widely employed for interrogation due to its defect sensitivity, an amplitude and group velocity adjustment equation with temperature change is proposed. Finally, considering the amplitude difference of normalised A0 mode, the two damages are localised within a network of PZTs by using a probability-based signal difference coefficient method, which is found to be efficient and reliable for SHM of HCSS under variable temperature conditions.