Time-Frequency analyzing of acoustic emission signals in drilling of glass/epoxy composites

Drilling is a dynamic process which causes some defects in composite materials such as delamination, fiber pull out and matrix cracking. Because of non-stationary behavior of drilling process, using online method to monitor these damage mechanisms is inevitable. In this paper, acoustic emission signals and wavelet analysis are applied to monitor drilling action from entry to exit. The results show that the selected monitoring indices from the time domain parameters and wavelet packet coefficients are capable of detecting the drilling stages and damage mechanisms during the process effectively.