Mechanism And Experimental Study On Drilling And Milling Of Carbon Fiber Reinforced Composite Screw Hole Making

Carbon fiber-reinforced Plastic(CFRP)composites are widely used in high-tech fields such as national defense science and technology,aviation and aerospace for their excellent properties such as light weight,high strength and high specific modulus.Burr,delamination and tear are easy to occur in CFRP hole making process.In this paper,aiming at the disadvantages of existing system of CFRP hole process,to improve the machining efficiency,inhibition of hole defect,put forward the system of drilling and milling composite screw hole of the new process methods,and combining the new type drilling CFRP special hole cutting tool and the structure of positive and negative spiral milling cutter and system integration of suppression principle of design of the drill hole defects-milling composite new cutter.On this basis,the drilling-milling compound screw hole machining mechanism and drilling-milling new tool hole-making effect are explored.Firstly,in order to study the mechanism of CFRP cutting surface formation,a single fiber cutting mechanical model and a theoretical model of cutting surface formation were established based on elastic foundation beam theory and Hertz contact theory.The cutting models of CFRP with different fiber orientations(θ=0°,45°,90°,110°,135°,160°)were simulated by using the there-dimensional microcutting model of CFRP established by Abaqus.Combined with mechanical model and simulation model,the continuous variable cutting mechanism and sub-surface damage were studied in depth,and the theoretical model and simulation model were verified by CFRP groove milling test.The results show that the mechanical model and finite element model established can reflect the evolution law of CFRP machined surface effectively.Secondly,in order to explore the formation mechanism of the cutting surface of drilling and milling composite machining,a finite element model of CFRP secondary cutting was established based on the formation theory of CFRP cutting surface and the depth of machining surface damage.The cutting simulation was carried out for four typical fiber orientationsθ(θ=0°,45°,90° and 135°).Drilling and expanding hole cutting experiments were designed to verify the cutting model,and the formation process and characteristics of the secondary cutting surface in open drilling and milling were revealed.Then,kinematics analysis of helical milling,at the drill-new milling cutter blade point(point)set up the key points of the kinematics equation and the theory of screw in the hole machining of cutting layer model,analyses the spiral cutting edge in the hole machining of trajectory characteristics,illustrates the screw in the hole machining of the variation regularity of residual processing area and the change rule of cutting layer area;Finally,in order to explore the hole-making effect of drilling and milling compound spiral hole-making process,a new drilling and milling tool was designed and manufactured.Through drilling and drilling and milling compound hole-making experiment,the hole making defects,hole making accuracy and cutting force of the new tool were studied emphatically.The formation and evolution law and change law of hole making defects are clarified.The variation law of hole-making precision is analyzed.The time-varying characteristics and changing rules of cutting force,and the mapping relationship between "cutting force" and "hole making defect".The results show that the hole-making effect of the new drilling and milling composite tool is highly consistent with the design concept,which provides a theoretical basis for the development of the new CFRP hole-making tool.The cutting mechanics model and the finite element theoretical conclusion are in good agreement with the experimental observation,which can effectively reflect the stroke mechanism of CFRP cutting surface and the formation mechanism of drilling and milling composite machining.The new process of drilling and milling combined screw hole making can effectively completely remove burr and significantly inhibit or reduce delamination,which provides practical guidance for CFRP hole making with high efficiency and low loss.