Process monitoring in milling unidirectional composite laminates through wavelet analysis of force signals

Abstract

The extensive application of composite materials in the aerospace and automobile industry and significant machining challenges warrant the need of process monitoring techniques. These techniques help in detecting dynamical instabilities, monitoring machining induced damage and surface quality within a given tolerance. This study discusses the application of continuous wavelet transform analysis in trimming of unidirectional graphite epoxy laminates. The suggested approach is used to obtain time-frequency scalograms and windowed Shannon entropy to characterize the process for different machining conditions and fiber orientation angles. The relative wavelet entropy (RWE) proved to be an efficient classifier in characterizing and developing optimum values at different experimental conditions. A deviation from these optimum values indicated severe damage. In addition, a positive correlation was found between RWE and surface quality.