A mechanistic prediction model for thrust force and torque during drilling of CFRP/Ti stacks

Drilling holes on carbon fiber reinforced plastic/polymer (CFRP) and Ti stack structures is significantly important assembling process in aerospace manufacturing. However, it is quite a challenge that the excessive and completely different drilling loads of two materials with distinguish physical and mechanical properties will lead to frequent CFRP drilling damages and Ti burrs, as well as rapid tool failures. Therefore, understanding and controlling the drilling loads are crucial to ensure low damage and high efficiency drilling of CFRP and Ti stacks. In this paper, a novel mechanistic model was established to predict the thrust force and the torque in the drilling of CFRP and Ti stacks. The cutting loads of a twist drill were discretized along chisel edge, primary cutting edge, and minor cutting edge. An orthogonal cutting model and an oblique cutting model were proposed to represent the discretized cutting load for CFRP and Ti with the consideration of fiber cutting angles, flank face friction, and drilling parameters. Integrating the discretized cutting load, a mechanistic model for predicting thrust force and torque was developed for drilling of CFRP/Ti stack. After the coefficient calibrations, verification experiments showed that the developed model has accurately predicted the thrust force and torque under various spindle speeds/feed rates as well as the changing fiber cutting angles. © 2020, Springer-Verlag London Ltd., part of Springer Nature.