An experimental study of orthogonal cutting mechanisms for epoxies with two different crosslink densities

In this study, we investigate the machining behaviour of a Piperidine and a MDA cured DGEBA epoxy resin under low speed orthogonal micro-cutting conditions. The characteristics of chip-workpiece separation, chip formation and machined surface damage were examined in association with thermomechanical and mechanical properties of the epoxies. It is found that the separation of the chip from the workpiece takes place by fracture, according to Williams' model of machining. Further, cube-square scaling principles can be used to explain the mechanism of the observed brittle-to- ductile cutting behaviour of the epoxies. The results also show that the chip formation process is determined by both shear yielding and plastic bending behaviour of the material. In particular, chip formation involves the imposition of large strain plastic deformation. This explains the dependence of the cutting states (such as continuous chip and broken chip) on the degree of crosslink density of the epoxy, since the latter controls the post-yield deformability of epoxy chips. Based on our new findings, a modified Williams' cutting model is proposed to account for the chip formation behaviour of polymers in cutting.