Investigations into the effect of geometry of a trepanning tool on thrust and torque during drilling of GFRP composites

This paper presents the results of an experimental investigation into the effect of the geometry of a trepanning tool on thrust and torque during the drilling of uni-directional glass fibre-reinforced plastic (UD-GFRP) laminates. It is well-known that the most effective way of achieving good quality holes while drilling fibre-reinforced plastics (FRPs) is by reducing the thrust and torque. Therefore, this investigation was aimed at exploring the possibility of reducing the thrust and torque by using the concept of trepanning. The design considerations and development methodology of the trepanning tool are discussed. The appropriate tool geometry has been determined by using statistically planned experiments and analysis. Orthogonal arrays with analysis of means as well as analysis of variance have been used to assess individual factor and interaction effects and their significance levels. The investigations have revealed that the performance of the trepanning tool is superior to that of conventional twist drills in terms of thrust, torque and hole quality. Low production cost and ease of regrinding are its major additional advantages due to its simple geometry. (C) 1999 Elsevier Science S.A. All rights reserved.