A Comprehensive Study on Detection of Hidden Delamination Damage in a Composite Plate Using Curvatures of Operating Deflection Shapes

The aim of this work is to investigate the accuracy and sensitivity of a continuously scanning laser Doppler vibrometer (CSLDV) for detection of hidden delamination damage in composite plates. Some work on using a CSLDV for detection of damage in aluminum beams and plates has been done by the authors. The current work is related to a worldwide round robin study sponsored by the Society of Experimental Mechanics. The main difference between the current work and previous work is that the damaged composite plate was provided by the organizer of the round robin study instead of being made by the authors. Hence, the authors have no information about locations of the damage, which means this is more like a blind test. The most significant advantage of using a CSLDV for vibration measurement of a structure is that a spatially dense operating deflection shape (ODS) of the structure can be obtained and further used to calculate the curvature of the ODS (CODS). A comprehensive study to detect the hidden damage in the composite plate by using the first seven CODSs from the corresponding ODSs of the plate is conducted. The study shows that different CODSs have different sensitivities to local anomaly induced by the damage and only two of the seven CODSs can be used to detect the locations of the hidden damage.