Guided wavefield curvature imaging of invisible damage in composite structures

•Guided wavefield curvature is proposed for the detection of structural damage.•The guided wavefield curvature can highlight the damage-related wavefield anomalies .•Damage maps are constructed by fusing wavefield curvature energy images.•The damage maps are successfully applied for the imaging of invisible damage. Guided wavefields in composite structures carry a wealth of information about wavefield anomalies from damage–wave interactions. Although such anomalies can be used for damage detection, they are easily masked by incident waves from actuators and reflected waves from structural boundaries. This research presents a concept of guided wavefield curvature for the detection of structural damage. Wavefield curvature analysis is able to highlight the amplitudes of local anomalies in the wavefield signals associated with damage. A wavefield curvature imaging algorithm is developed for visualizing invisible damage in composite structures. The algorithm is first verified by detecting delamination in a carbon fiber reinforced polymer (CFRP) plate and then applied for detection of debonding in a honeycomb sandwich panel. In the experiments, wavefields are generated by a PZT transducer and are then registered by a scanning laser Doppler vibrometer. The experimental results accord well with the actual locations, sizes, and shapes of the delamination and debonding, confirming the effectiveness of the proposed algorithm for the detection of invisible damage in composite structures.