Detection of Damage in CFRP by Wavelet Packet Transform and Empirical Mode Decomposition: an Hybrid Approach

The integrity of the CFRP specimens is tested using acousto-ultrasonic testing method. To validate the acousto-ultrasonic test mode, the specimens are tested before and after a Barely Visible Impact Damage induced by an impactor. A special model is created to use both Wavelet Packet Transform and Empirical Mode Decomposition, for decomposing the recorded waveforms. This mode also enables the reconstruction of the decomposed waveforms, discarding the residual signal in the parent waveform, and calculates the energy associated with each frequency band of the reconstructed signal. By using the percentage of energy recovered by the receiver compared to the signal sent through the specimen, the integrity of the specimens is identified. Moreover, the properties of each specimen and the extent of its damage, albeit qualitatively along the longitudinal and transverse directions can also be assessed by using this technique.