Experimental Investigations on Drilling GFRP Epoxy Composite Laminates Using Specialized and Conventional Uncoated Cemented Carbide Drills

The growing demand of the fiber reinforced plastics (FRPs) in lightweight engineering has led to a need for assessing and quantifying the workpiece material defects, like hole exit delamination, during their drilling process. This article presents the experimental investigations on in-process drilling load profiles and a quantitative analysis of the induced hole exit delamination in drilling glass fiber reinforced plastic (GFRP) epoxy composite laminates, using various uncoated carbide drill bits (two specialized and a conventional one). The aim of studying and analyzing the in-process load profiles, in this work, is necessary in better comprehending the interaction between the tool and the workpiece material, with respect to the induced peak loads. It may further be helpful for determining and assessing the root cause of the induced delamination damage. Moreover, it is shown that the design and geometry of a particular drill bit also plays a vital role regarding its cutting loads and delamination results. The specialized tools were found to be much better than their conventional counterpart. Furthermore, subsequent drilling was conducted onto some predrilled pilot-holes using the same specialized drills, to test the chisel edge effect. The research emphasizes a need to pay attention to the quality and design of a drill bit (cutting edge corner).