Optimization Studies on Thrust Force and Torque during Drilling of Natural Fiber Reinforced Sandwich Composites

摘要

This research is carried out to investigate thrust force and torque during drilling on the developed bio-degradable sandwich composites. Two natural fibers, namely vetiveria zizaniodes (vetiver) and jute, and one synthetic fiber, namely Eglass, are used as reinforcements with vinyl ester resin to form three composite specimens. The fiber compositions in each specimen are varied while the resin composition is kept as a constant. The vetiver fibers are pre-treated with alkali and followed by furnace heating in order to improve its surface properties. The specimens are subjected to a set of 28 drilling operations during which the machining parameters, like speed, feed rate, tool point angle and work sample, are varied between four levels to form a four-factor mixed level D-optimal factorial design. During each drilling operation, the thrust force and torque are measured as responses by using a kistler make drill dynamometer with an accuracy level of 0.01N. The responses are analyzed by using response surface method, and non-linear regression equations are developed. Optimization on the experimental data resulted in selection of a high level of speed of 2000 rpm, low level feed of 0.1 mm/rev, tool angle between 600 to 900 and selection of sample level I as optimized values with a thrust force of 82.47 N and torque of 4.4 Nm. Confirmatory runs are conducted and the responses are again measured. The average error between the developed model and the confirmatory runs is found to be minimal and hence the optimization is highly satisfactory.