Theoretical and experimental study of tool wear using active backup force for drilling composite materials

Abstract

The advent of composite materials has allowed for the state-of-the-art fabrication of structural parts with delamination-free holes. These are widely used polymers in aerospace, military and biomedical devices. Fabricating a delamination-free hole using a traditional twist drill is fast and cost-effective but the surface roughness depends on the drilling parameters, the tool geometry and the tool material. However, tool wear is inevitable when machining composite materials. It reduces the service life of the tool and affects the surface quality and the dimensional accuracy of structural parts. A mechanical and energy analysis is used to develop a mathematical model for the critical thrust force to correlate tool wear and the associated active backup force for drilling composite materials. The theoretical analysis and experimental results show that delamination due to worn twist drills is mitigated by using an active backup force. The developed model is extended to determine the effect of tool wear and an active backup force on the thrust force for future drill bits.