Glass Fiber-reinforced Composite Drilling Pilot Study

Glass fiber reinforced plastics(GFRP) possess light weight, high strength-to-weight and stiffness-to-weight ratios, good corrosive resistance, excellent fatigue resistance and low thermal expansion coefficient. They are, therefore, attractive for high performance applications such as in aerospace, sporting goods and special vehicles, etc. Due to their anisotropy, low thermal conductivity and low strength between two layers make the process of drilling in GFRP more difficult, it s easy to produce problems in drill such as fibre pullout, delamination, avulsion, etc. The thesis presents an intensive study on drilling technologies of GFRP, thus providing technical supports for the application of GFRP in special vehicles.The thesis analyzed the cutting force, cutting heat and the deformation of chips affected by fiber orientation in the process of cutting, studied the delamination mechanism of the material, discussed the delamination of measure method and evaluation index, and obtained the suppression method of delamination.Based on the experiment of drilling GFRP, discussed the effects of parameters on thrust force and delamination, such as exit back-up, chisel edge, coating material, and established the empirical relationships between thrust force and feed speed, spindle speed, drill diameter, etc.Drilling trials had been carried out on glass fiber reinforced plastics with twist drill which had S shaped drill tip coated by TIN and observing the ground surfaces of drilled holes by using scanning electron microscope(SEM), the fracture mechanisms of glass fiber and the microscopic characteristics of ground surfaces were analyzed. The experimental results show that twist drill with S shaped drill tip offered less drilling thrust force and delamination fracture campared with conventional twist drill.An experiment study of drilling GFRP concerning high hole quality were carried out, it was found that PCD twist drill was better than S shaped drill tip and standard twist drill in hole quality and tool life. PCD twist realized the high quality and efficiency on drilling GFRP.