Fiber and fiber-matrix interface effects on the orthogonal cutting of fiber reinforced plastics.

摘要

Traditional machining processes had been shown to be an effective method of producing fiber reinforced plastics (FRPs) parts. However, the interaction of cutting tool and reinforcements produced surfaces that are highly dependent on both the reinforcements' properties and the relative angle between the cutting tool path and the fiber orientation. This study will address the above issues.; The effects of fiber and fiber-matrix interface on the orthogonal cutting of FRPs were examined using experimental and analytical methods. Two sparsely distributed, idealized FRP model materials were used, namely a copper fiber reinforced polyester (CuFRP) and a glass fiber reinforced polyester (GFRP). The fiber volume fraction of the FRPs used in this study were kept low to study the effects of reinforcements on the machining process. The machining process was monitored using photoelastic stress observations and dynamometry. The machining damage was examined and quantified using scanning electron microscopy and a back-light technique. Finite element analysis of the GFRP workpiece was also made to aid in understanding the machining process. Finally, specific cutting energy models were proposed based on the assumption that the cutting energy of the composite is the sum of the energies for machining each constituent and the energy needed to debond the fiber-matrix interface.; The study showed that reinforcements in the workpieces acted as stress risers during the machining process. The stress state in machining the GFRP material was similar to the machining of a heterogeneous, orthotropic material. Machining mechanism was distinctly different for the two types of reinforcements used. The ductile copper fibers were sheared across the cutting plane; while glass fibers of similar orientation fractured perpendicular to the fibers' axes. Fiber-matrix debonding was observed for the CuFRP workpiece oriented {dollar}ge{dollar}90{dollar}spcirc{dollar}; while fiber pull-out was evident for GFRP workpiece at {dollar}ge{dollar}60{dollar}spcirc{dollar}. Within the experimental conditions, a positive rake took, a low depth of cut, and a high cutting speed reduced the machining stresses and produced a better surface. The specific cutting energy models proposed were shown to be a good approximation of the measured machining forces.