Discrete wavelet decomposition of acoustic emission signals from carbon-fiber-reinforced composites

The wavelet transform is applied to the analysis of acoustic emission (AE) signals collected during static lending of unidirectional and cross-ply carbon-fiber-reinforced plastic (CFRP) composite specimens. With this technique, the AE signals ave resolved both in the time and in the frequency domains and are then decomposed into various wavelet levels (11 in all). Each level is examined for its specific frequency range, energy change rate, and percentage of total energy. A general trend is observed by investigating the energy distribution of decomposed AE signals. This trend indicates that the energy in the AE signals is essentially concentrated in three levels (levels 7, 8, and 9) representing frequency ranges of 50-150 kHz, 150-250 kHz, and 250-310 kHz, respectively. Furthermore, the energy percentages in levels 7, 8, and 9 are determined to be 8, 15, and 75%, respectively. The analysis indicates that the information in the three dominant wavelet levels may be related to different failure modes associated with fracture of CFRP composites. In this paper, the results of the wavelet-transform-based decomposition of AE signals are presented. The results indicate that wavelets-based signal processing may be a useful tool in the analysis of acoustic emissions. (C) 1997 Elsevier Science Limited.