A study on the effects of machining variables in surface grinding of CFRP composites using rotary ultrasonic machining

Due to their excellent properties, carbon fiber-reinforced plastic (CFRP) composites are attractive in many industries, including aerospace, automobile, sports, etc. The structure of anisotropy and heterogeneity and the high abrasive resistance of carbon fibers make CFRPs difficult to cut in surface grinding processes. Many problems, including high cutting force, high tool wear, severe delamination, and high cutting temperature, are associated with conventional surface grinding processes. To reduce or eliminate these problems, surface grinding of CFRP composites using rotary ultrasonic machining (RUM) has been conducted. Machining variables play dominant roles in such a process. However, no investigations on effects of machining variables on output variables were reported. This paper, for the first time, reports effects of machining variables (ultrasonic power, tool rotation speed, feed rate, and depth of cut) on output variables (cutting force, torque, and surface roughness). The results revealed that the cutting force could be decreased by using higher level of ultrasonic power, higher level of tool rotation speed, lower level of feed rate, or lower level of depth of cut. Lower surface roughness could be achieved by a decrease of ultrasonic power, an increase of tool rotation speed, a decrease of feed rate, or a decrease of depth of cut. The machined CFRP surfaces’ morphology and the characteristics of damaged carbon fibers were, for the first time, analyzed and reported in such a process.