Debond Detection and Quantification in Honeycomb Sandwich Structure Using Low Frequency Guided Waves

Detection of debonds in honeycomb sandwich-type structures has been a subject of interest for many researchers. However, detection and quantification of debonds in sandwich structures by methods adaptable for structural health monitoring is still being pursued. Low frequency guided waves are being used for the detection, localization and quantification of the debonds, with some limitations, like quantification of the damage being dependent on the distance of the sensor from the debond, need for a reference signal from the pristine structure etc. The present work investigates the potential of the low frequency guided waves in the detection, localization and quantification of debonds in Honeycomb Sandwich Structures (HSS) and addresses some of these limitations. A unique debond quantification curve for the given HSS is generated using a 3D finite element model and validated experimentally. Unlike in earlier works, these curves are independent of the distance of the sensor from the debond. The methodology is demonstrated in pulse-echo and pitch-catch configurations, and it does not need a reference signal from the pristine structure. The developed method is effective in detecting and quantifying the debond located on both the face skins of the sandwich, with the sensor mounted only on one face skin. An efficient methodology to assess the size of the debond is proposed, based on the results obtained from this study. The guided waves are actuated and sensed by Lead Zirconium Titrate (PZT) transducers which facilitate the implementation of structural health monitoring.