The effect of drill geometrical properties on delamination and diameter error of holes in a thin sheet of Kevlar/epoxy composite

The use of composites in the aerospace industries is widespread due to their unique properties, as in some planes, more than half the weight of the aircraft is composed of composite materials. Drilling is one of the most widely used machining operations to assemble composite parts and connect them to each other. Delamination and hole diameter errors are the most important defects that occur during drilling of fiber-reinforced composites which reduce the efficiency of composite structures. The purpose of this research is to investigate the effect of twist drill point angle and size of chisel edge on delamination and diameter error of the hole in drilling of a thin sheet of Kevlar/epoxy composite with a supporter plate. The experiments were designed and implemented with full factorial design and in 3 levels for feed rate and 3 levels for cutting speed. The obtained results showed that the lowest mean diameter error of the hole is obtained in drilling with a 135-degree point angle drill with chisel edge and the lowest mean delamination factor in drilling is obtained with a 135-degree point angle drill without the chisel edge.