Rake Angle Effect on a Machined Surface in Orthogonal Cutting of Graphite/Polymer Composites

Abstract

Graphite and its composites have been widely used in various industrial fields. It has been generally accepted that, for positive rake angles, there is a significant increase in tension stress at the cutting zone during the machining of brittle materials, and cracks occur and spread easily, degrading the quality of the machined surface quality. However, it is found in this study that positive rake angles can improve the machined surface finish during the orthogonal cutting of graphite/polymer composites. Better machined surface finish is obtained for a larger rake angle. A finite element model is developed to reveal the mechanism of influence of the positive rake angle on the machined surface. Based on the effective stress field obtained from finite element analysis, it can be predicted that the crack initiates at the tool tip, subsequently propagates downward and forward, and later spreads gradually toward the free surface of the workpiece. A larger rake angle can promote crack propagation far from the machined surface. e crack initiation and propagation laws are validated by the edge-indentation experiments. In addition, the cutting force at various rake angles is investigated.

Rake angle effects on ultrasonic-assisted edge trimming of multidirectional CFRP laminates

“…On the contrary, the rake angle of 0 o was responsible for the deterioration in surface quality at the tool disengagement when the ultrasonic vibration is applied. A similar observation was reported during the orthogonal cutting of graphite/polymer composites [32]. This is mostly because either compression stress imposed by a negative rake angle tool or tensile stresses imposed by a positive rake angle can reduce the surface roughness, and either case will depend on fiber orientation.…”