Drilling of Carbon Fiber Reinforced Plastic Composites with Feedback Control Based on Cutting Force

For generating holes on carbon fiber reinforced plastic (CFRP) composites, drilling is one of the most commonly applied processes. However, machining defects caused by delamination occur frequently during this kind of process. To realize defect-free drilling of CFRP composites, we propose to apply feedback control based on thrust force, because the degree of thrust force is directly related to the occurrence of delamination. In this study, we have developed a machining system which can be operated at a predetermined cutting force by changing the feed rate based on cutting force signals measured by a piezoelectric cutting dynamometer, and the basic performances of the developed system have been confirmed through evaluation tests. In addition, drilling tests with the developed system were carried out, in order to consider the possibility of defect-free drilling of CFRP composites with feedback control based on cutting force. In the drilling tests, we used a conventional twist drill, and the work-piece was a quasi-isotropic laminate composite, which is a stack of unidirectional plies consisting of high-strength carbon fibers T800S and high-toughness matrix resin 3900-2b. We have confirmed, under specific conditions through drilling tests, that the feedback control process can machine through-holes without causing significant machining defects on CFRP composites.