Fundamental Research On Drilling Carbon Fiber Reinforced Plastics With Brazed Diamond Tool

With the advantages like superior strength-to-weight, specific modulus, stiffness-to-weight ratios,carbon/epoxy is widely applied in aeronautics and aerospace domain, automobile and energy area, etc.Epoxy is used extensively for the super mechanical properties, so carbon fiber reinforced plastics(CFRP) usually represent carbon/epoxy. Drilling process is required frequently in fastening partinstallation in CFRP parts, while the drilling quality is hard to guarantee and the drill life is quite shortfor the high stiffness and hardness, anisotropy of CFRP. The main works have been done as follows:(1) Based on the CFRP drilling experiments with twist drill, the drilling process has beenanalyzed, and the formation mechanism analysis on chips and machined surface has been studied. Theinfluences of drilling parameters on quality, such as delamination and cracking, have been studied. Asthe machinability of CFRP has been understood, the existed problems during the drilling process withtwist drill and corresponding solutions have been illustrated.(2)Referring to the development trends of tools in CFRP drilling, the brazed diamond core drillwas applied. After experimental comparison, the thickness of brazed matrix, the grit size and gritsdistribution of brazed diamond core drill were decided. By drilling CFRP with brazed diamond coredrill under the common parameters, the drilling accuracy was proved to satisfy the requirements.(3)The undeformed chip thickness changes when using core drills with different grits distributionunder the same drilling parameters. When drilling the CFRP laminate using core drills with differentgrits distribution, the grinding force and temperature were measured. Since only the exit temperatureof holes can be measured with the infrared temperature sensor, the simulation of temperature field hasbeen carried out to analyze the temperature change in drilling. Comparing the formation mechanismof chips and machined surface, the effects of undeformed chip thickness on chips and machinedsurface formation has been studied.(4)Based on the influence of drilling parameters on quality, the causes of damages in drillingwith brazed diamond core drills have been studied. The wear test of brazed diamond core drills wascarried out under the usual parameters to make sure that the life of core drills was much longer thancemented carbide twist drills. From the drilling mechanism of brazed diamond core drills, thecontrolling measures of damages, especially the recommendation of drilling parameters have been putforward.