Influence of cooling on the performance of the drilling process of glass fibre reinforced epoxy composites

Non-laminate composites find their paramountcy in large structures, ballistic applications, etc. However, literature about the hole making process in thick composites, non-laminate composites and that under different cooling methods (dry, external and internal) is scarce. Hence the present study examines how the different methods of cooling influence the quality characteristics (drill flank temperature and damage factor) during drilling 20 mm thick Glass Fibre Reinforced Epoxy (GFRE) pultruded composite rods having 80% fibre weight fraction and 0° fibre orientations with reverence to the feed direction. Response Surface Methodology (RSM) was used to design the drilling experiments and the latter was executed utilizing 10 mm diameter twist drills made of cemented carbide. Response surface models utilizing Design-Expert software were developed, which empirically relates the process parameters with the obtained experimental values of quality characteristics. The effects caused by process parameters on quality characteristics were analyzed by utilizing response surface graphs. The process parameters (spindle speed, feed per revolution and coolant pressure) have been optimized within the selected range. The optimal parameter levels are attested by validation test. The contribution of this investigation is to make understand that the use of twist drill with internal cooling is critical to get damage tolerance holes.