Study on dedicated drill bit design for carbon fiber reinforced polymer drilling with improved cutting mechanism

Abstract

Carbon fiber reinforced polymer (CFRP) has significant applications in the aerospace and automobile industries. However, the relatively high thermomechanical loads generated when drilling CFRP is considerably detrimental to the cutting tool. To address this issue, in this work, a step-change in the performance of CFRP drilling was conducted by switching the cutting model from crushing/compression fracture to the shear cutting of the composite workpiece to suppress the thermomechanical loads using a novel web thinning design. To evaluate the performance of the proposed drill bit, a comprehensive comparison was carried out between the dedicated and conventional drill bit designs from thermal, mechanical, and chip formation points of view. The results show that the dedicated drill bit outperformed the conventional drill bit in terms of thrust force, temperature elevation, burr, and exit-delamination. An in-depth observation revealed that the shear cutting became dominant in the drilling with the proposed drill bit while the crushing/compression was dominant with the conventional drill bit. The transition of the phenomena was induced by the properly designed rake angle. The mechanism of material removal in CFRP drilling using the dedicated drill bit design provides a new design direction to modifying the rake angle for improving the efficiency and quality of composite material drilling.