Investigation of structural integrity of composite materials using wavelet packet transform

Carbon Fiber Reinforced Plastic (CFRP) laminates are tested using Acousto-Ultrasonic approach. The materials are subjected to out of plane impact and the Acousto-Ultrasonic approach is used to test the materials both before and after the impact event. The Waveform of the recorded signal before and after the impact is used to characterize the structural integrity of the material. Wavelet Packet Transform (WPT) analysis was used to decompose the Wavelets. The WPT analysis is preferred over the conventional Discrete Wavelet Analysis (DWT) owing to the possibility of analyzing both the approximation and details of the decomposed Wavelet. From the WPT results, the spectral energy in the time domain associated with each of the recorded wavelets are analyzed. The spectral energy is successfully used to characterize the integrity of the CFRP material before and after the impact event. The magnitude of the spectral energy in both the longitudinal and transverse direction of the specimen is observed to be lowered after the impact event. Using this technique, it is possible to characterize the integrity of the material even before it is subjected to loading.