GAZI UNIVERSITY JOURNAL OF SCIENCE, cilt.30, ss.39-50, 2017 (ESCI İndekslerine Giren Dergi)
The selection of drill geometry and drilling parameters has high importance due to thermo-mechanical formations in drilling of carbon fiber reinforced polymer (CFRP) which has anisotropic structure. This study focused on the effects of drilling parameters on thrust force and hole quality in drilling of CFRP composites by applying constant and varying feed rate with uncoated WC drills having different point angles. Surface roughness, delamination factor and diameter plays a crucial role in the production of close-tolerance holes in hole quality. The quality of the hole surface was examined via surface roughness measurements and surface damage by scanning electron microscopy (SEM). Machinability experiments were performed with three different levels of drilling parameters that are point angle, cutting speed and feed rate. It was determined that thrust force (Fz), delamination factor (Fd) and surface roughness (Ra) values obtained in drilling processes by varying feed rate in hole exit are lower than that of constant feed rate with average of 21%, 14% and 36%, respectively. On the other hand, hole diameter (d) values obtained with varying feed rate in hole exit were higher than that of constant feed rate. The effects of drilling parameters on Fz, Fd and Ra were determined by analysis of variance with 95% confidence level and feed rate was found as the most significant parameter on them.