Analysis of delamination in drilling of circular plate composite materials with a multi-facet drill bit

Abstract

Delamination is recognized as one of the most critical defects that can result from the machining of composites. Delamination has been a major form of failure in drilled composite materials due to the composite’s lack of strength in the direction of drilling, which results in poor surface finish, reduction in bearing strength, reduction in structural integrity, and ultimately poor performance of the composite. Delamination due to drilling has been a major research interest for many years, and a considerable amount of work has been done to reduce it. This thesis work involved deriving a formula to determine what applied thrust force would cause delamination in a particular drill bit, the multi-facet drill bit. To achieve that goal, a formula was developed. The conditions and the drill bit used were altered. The thrust force at which delamination occurred was dependent on the thickness and the composition of the material being used. Experimental validation of the physical model involved calculating the thrust force that would cause delamination, using the formula, and drilling at the calculated thrust force. The thrust force was applied as a correlation of feed rate and spindle speed.