Investigation of the variation in drilling force and tool diameter in micro drilling of thermoplastic and thermoset based carbon fiber laminated composites

Nowadays, composite materials are widely used in various industries includingautomotive, defense and aerospace. In this thesis, the drillability of Polyether ether ketone (PEEK), a thermoplastic (TP), and a thermoset (TS) composite reinforced with carbon fibers was experimentally investigated and the findings were supported by Taguchi analysis. In this study, micro drilling was performed on two different composite types using four different feed rates (0.5, 1, 2, 4 µm/rev) and four different cutting speeds (10, 20, 30, 40 m/min). In the results obtained, the drilling force calculated for TS composites was higher than that calculated for TP composites. There is a significant effect of material type, feed rate and cutting speed on the drilling force, and increases in both feed rate and cutting speed result in a decrease in the drilling force. The most significant effect on drilling force was found to be feed rate (50.81%), followed by material type (19.65%) and cutting speed (17.64%). On the other hand, in the general analyses, higher drill amount reduction rates were observed in TP material compared to TS, but it suggests that TP may cause more damage to the micro drill. However, there was no significant effect on the reduction in the amount of material in the established regression model. The factors affecting the reduction in drill diameter in the micro drillability of TP and TS composites were determined as feed rate and cutting speed. It was determined that the effect of feed rate on the reduction in drill diameter (61.72%) was greater than the effect of cutting speed (24.83%).