Mechanical model for predicting thrust force with tool wear effects in drilling of unidirectional CFRP

Abstract Thrust force is the most influential factor to the frequent-occurred drill-exit damages in the drilling of carbon fiber reinforced polymer/plastic (CFRP). The accurate prediction of this thrust force is of great importance for drilling process optimization to suppress these damages. However, the thrust force in drilling CFRP is strongly coupled with rapid tool wear which brings significant challenges to its accurate prediction. This paper proposed a novel mechanical model for predicting thrust force with the consideration of tool wear effects in drilling unidirectional CFRP. Firstly, tool wear geometrical characteristics of a twist drill, including rake face, cutting edge and flank face are identified as a line, elliptical arc and line profiles, respectively. The contact conditions and cutting mechanism between CFRP and drill bit are further analyzed based on the identified wear profiles and contact mechanics. Then the thrust forces of the main cutting edge and the chisel edge are modelled based on these analyses. Integrating these forces along the main cutting edges and the chisel edge, the total thrust force in drilling CFRP is predicted considering the tool wear effects. Drilling experiments are carried out to validate the prediction model, and the predicted and experimental results are in good agreement.