Damage detection and localization using Lamb waves in highly anisotropic structures with multiple curvatures

For the development of structural health monitoring (SHM) systems and non-destructive testing methods based on Lamb waves it is very important, to detect and visualize the entire wave field in the structure. This is currently the only way to reliably determine the source of the waves detected at SHM sensors and to trace their propagation paths in complex structures. During the past years non-contact methods using air-coupled ultrasonic sensors were successfully developed at the DLR to visualize Lamb waves [31]. However, on the way from laboratory applications towards a practical use of SHM systems using Lamb waves there are still many more obstacles to overcome. This paper addresses the special challenges, that arise for the detection and evaluation of wave fields due to the shape and the material properties of real fiber reinforced structures compared to standard flat plates used in the laboratories. An optical measurement platform and a special reconstruction algorithm for damage localization are presented. The measurement system and the algorithms are especially focused on applications for large, curved structures like airframe components and wind turbine rotor blades