Experimental evaluations for the characterization of a new tool for fibrous composite materials drilling

The drilling of composite material laminates is a widely used process and is critical from a structural point of view. It requires particular attention, due to the various types of damage that can be caused if the process is incorrect. The delamination of the outer plies of the laminate at the exit edge of the hole is a typical defect detected after drilling composite materials. This is related to the thrust force required for drilling, which is connected, other cutting parameters being equal, to the feed rate. High feed rates are associated with high thrust force and, accordingly, the probability that delamination will occur, increases with feed rate and force. In this work a study for developing a new step multifacet drill bit, named SEE, Step Elliptical Elliptical, is presented. Experimental tests showed that the new tool allows a decrease of about 50% in the maximum thrust force, compared with the one shot drill bit, which is still widely used in the aeronautical field.