Online detection of crack damage in composite plates using embedded piezoelectric actuators/sensors and wavelet analysis

The method for online detection of initial damage in composite structures proposed in this paper is based on energy variation of structural dynamic responses decomposed using wavelet analysis. It is much more sensitive than the existing methods, and it can detect extremely small cracks in composite plates. The results obtained in this study show that the smallest detectable crack may reach the dimension of width 0.1 mm and length 2.3 mm, and the area containing this crack is only 0.06% of the total area of the plate. In addition, the piezoelectric smart materials embedded in the laminated composite structures are used as both actuators and sensors. The in situ active damage detection of composite structures can be implemented using the embedded piezoelectric materials in combination with signal processing based on vibration analysis. This method is suitable for damage detection of inaccessible structures used in severe environments without using an additional excitation facility. It can make the in-service inspection of composite structures more safe, reliable and affordable. (C) 2002 Elsevier Science Ltd. All rights reserved.