Modeling and optimization of process parameters for defect toleranced drilling of GFRP composites

Drilling is a frequently practiced machining process for fiber-reinforced plastics (FRP) in industry owing to the need for component assembly in mechanical structures. Drilling experiments are performed on a (0/ +/- 45/ 90)(2s) 3-mm-thick glass fiber-reinforced laminate using 4-, 6- and 8-mm-diameter HSS drills. The machining response of the quasi-isotropic laminate was studied by monitoring the thrust and torque. The performance of the HSS drills for different cutting conditions was studied by measuring the tool wear. Delamination due to drilling is a major concern in machining a composite laminate and is analyzed by using linear elastic fracture mechanics, classical plate bending theory, and the mechanics of composites. A mechanical model for evaluating the critical thrust at which delamination is initiated at different ply locations has been used, and the critical thrust force at the onset of delamination has been found to be 70 N. The present work analyzes data on the thrust force, torque, and tool life by using a group method data handling (GMDH) algorithm. An optimization algorithm using simulated annealing with a performance index is then applied to search for the optimal process parameters for delaminatien constrained drilling.