Factors Affecting Machinability Of Frp Composites

Drilling is an essential operation In the assembly of the structural frames ofautomobiles and aircrafts. The life of the joint can be critically affected by the quality of the drilled holes. The main objective of the present paper is to investigate the influence of some parameters on the thrust force, torque and hole quality in drilling processes of fiber-reinforced composite aterials. These parameters include cutting speed, feed, drill size, drill material (HSS twist drill, HSS-CO twist drill, carbide twist drill and carbide tip) and fib er volume fraction.The influence of number of drilled holes on the drill wear, torque, thrust force and hole quality has been studied. The quasi-isotropic composite materials were manufactured from randomly oriented glass fiber-reinforced epoxy (GFRE), withvarious values of fiber volume fractions (V f), using hand-lay-up technique. Two components drill dynamometer has been designed and manufactured to measurethe thrust and torque during the drilling process. The dynarnorneter was connected with a data acquisition, which installed in a PC computer. This set-up enable to monitore and record the thrust force and torque with the aid of a computer programthat designed using Lab View utilities.The results show that the start point of torque cycle is delayed by few seconds(depending on the value of feed) than the thrust force. This time is consumed topenetrate the specimen by chiseling edge. After the thrust force reached itsmaximum value it is gradually decreased during the full engagement of the drilland goes to zero when both the chisel edge and the cutting lips have exit of the laminate. In contrast the torque was gradually increased up to the end of the cycle and sudden jump to a value about 10 times the peak value. Cutting speed hasinsignificant effect on the thrust force and surface roughness of epoxy resin. For GFRE composites with Vr = 9.8 to 23.7% the thrust force and torque were