Machinability analysis in drilling woven GFR/epoxy composites: Part II – Effect of drill wear

The current paper is a continuation of the author’s work on machinability analysis in drilling woven glass fiber reinforced epoxy (GFRE) composites. The present paper deals the effect of drill pre-wear on the machinability parameters in drilling GFRE composites, at different cutting conditions. Machinability parameters were characterized by thrust force, torque, peel-up and push-out delaminations, and surface roughness of drilled holes. The results showed that, the behavior of thrust force during drilling process was greatly affected by the drill pre-wear. This effect becomes extreme at high cutting speed and feed, which in turn increases delaminations and surface roughness. The scanning electron photographs demonstrate that, peaks and valleys in surface roughness profile were due to burning the matrix. The multi-variable linear regression models were fair to fit the experimental data. Therefore, considerable attention should be paid to record different models that improve the correlation between the machinability parameters and machining conditions.