Positioning Research, Based On The Lamb Waves In Composite Structural Damage Of Active Monitoring Technology

Structural health monitoring system is an important research direction in the hot area of smart material and structures and Composite damage detection is an important research content of structural health monitoring.This study adopts active detection technique based on Lamb Wave to monitor damage in composite materials. PZT ceramics with the diameter of 8mm are bonded on the surface of fiberglass-reinforced composite material acting as both actuators and sensors to generate and collect Lamb waves. The waves emitted interact with discontinuities and experience a change in their propagation characteristics when damage is generated. By comparing sensor signals collected before and after damage happens, damage location can be determined.The research work of this paper are as follows:Firstly, the concept of active monitoring technique based on Lamb Wave in the paper and the propagation fundamentals of Lamb wave in structure are discussed. According to experiments, the optimal central frequency is studied in the range of selective frequency.Secondly, wavelet transform is applied to compute the arrival time of the Lamb wave group velocity Experiments results demonstrate that wavelet transform can improve the precision of damage localization.Finally, Damage Localization system for composite materials based on lamb wave methods using wavelet analysis is discussed in detail. According to fiberglass -reinforced composite material, the propagation modes of Lamb wave before and after damage's generation is analyzed. Ellipse technique is applied to determine damage location. Three time delay estimation methods are compared.This study can detect damage in two-dimensional structure, which means, damage is not necessary to locate in the beeline of detection route.