Ultrasonic NDE of composite material structures using wavelet coefficients

A wavelet-based method is proposed to perform the analysis of NDE ultrasoni c signals received during the inspection of reinforced composite materials. The non-homogenous nature of such materials induces a very high level of s tructural noise which greatly complicates the interpretation of the NDE sig nals. By combining the time domain and the classical Fourier analysis, the wavelet transform provides simultaneously spectral representation and tempo ral order of the signal decomposition components. To construct a C-scan ima ge from the wavelet transform of the A-scan signals, we propose a selection process of the wavelet coefficients, followed by an interpretation procedu re based on a windowing process in the time-frequency domain. The proposed NDE method is tested on cryogenic glass/epoxy hydrogen reservoir samples. ( C) 2001 Elsevier Science Ltd. All rights reserved.