Analysis of damage mechanisms in drilling of composite materials by acoustic emission

Conventional methods for analysis of drilling of composite materials usually study the amount of damaged area and effective parameters. However, these methods do not provide investigators with sufficient information regarding drilling-induced damage. In this paper, a procedure for discrimination and identification of different damage mechanisms based on the analysis of acoustical signals emitted during the process is presented. Using principle component analysis for data reduction and unsupervised pattern recognition analysis, the drilling process was divided into three main stages, i.e. entry stage, cutting stage and exit stage. Different methods of signal processing were then used to identify and discriminate the most active damage mechanisms in each stage. As a result, matrix cracking, delamination, fiber pull out and friction were discriminated and the frequency distribution of each one was identified.