Review and prospect of drilling technologies for carbon fiber reinforced polymer

Due to the superior physical and mechanical properties of carbon fiber reinforced polymer (CFRP), it has been widely applied in aviation industry. In primary load-carrying structures, the connection between CFRP and metal materials is mechanical joints usually. However, the drilling qualities are affected seriously by the anisotropy of CFRP. Drilling technology of CFRP/metal stacks has become a difficult problem in aircraft assembly process for the different properties of CFRP and metals. First, the chip formation mechanism, drilling force and drilling heat in drilling processes of CFRP and its stacks were explained. Second, the causes and influential factors of typical machining damage during drilling processes, such as burr and spalling, delamination defects and hole surface defects were analyzed. Then, the research status of optimization designs of materials and geometries of CFRP drilling tools were introduced. Various advanced process technologies of CFRP and its stacks, such as helical milling hole, varying parameter drilling, "grinding instead of drilling" and vibration assisted drilling, and simulation researches of drilling processes were reviewed. Finally, in order to realize the precise and efficient drilling processes of CFRP and its stacks, taking the unique advantages of brazed tools and ultrasonic vibration technologies, an ultrasonic vibration processing conception by brazed diamond tool with abrasive ordered arrangement was proposed.