Study of the Influence of Tool Wear of Two Drill Bits Manufactured with Different Coating Processes in Drilling Carbon/Glass Fiber Hybrid Composite Bounded with Epoxy Polymer

Abstract

Fiber Reinforced Polymer (FRP) laminates have been widely used in engineering applications in recent decades. This is mainly due to their superior mechanical properties compared to single-phase materials. High strength-to-weight ratio, high stiffness, and excellent corrosion and fatigue resistance are some of the attractive properties of these materials. In large structures, drilling composite panels is a typical operation to assemble different parts with mechanical fasteners. This operation severely threatens the quality of the holes and, therefore, the joint strength. This study aims to study the wear evolution of two drill bits manufactured with different coatings processes (chemical vapor deposition and physical vapor deposition) and their influence on the quality of the holes. A carbon/glass fiber sandwich structure was selected as the workpiece, and a high-speed machine center was used to drill 1403 holes per tool in the laminates. The wear analysis of the tool was characterized in terms of flank wear and crater wear. For the delamination analysis caused by drilling, two types of delamination are identified (type I and II), and their values were quantified through the equivalent delamination factor (Fed). The results showed that, in general, the process used to apply the coating to the tool influences the wear mode and the delamination damage. The first tool, diamond coated with Chemical Vapor Deposition (CVD), showed more severe crater wear in the flank face and coating loss at the end of the cutting edges. However, with a Physical Vapor Deposition (PVD) coating process, the second tool presented flank wear more controlled but a more severe coating loss and edge rounding near the tip, producing further delamination. Using a supporting plate showed a reduction of delamination type I but not for delamination type II, which is related to edge rounding.