Research On Dynamic Force Model And Its Mechanism Application Of High-Speed Dry Milling Of CF/PEEK

Carbon fiber reinforced polyether ether ketone(CF/PEEK)composite was a highend carbon fiber reinforced thermoplastic polymer(CFRTP)material.It has outstanding advantages such as light weight,high strength,wide peak absorption,high thermal temperature stability,wide processing window,recyclability and weld ability.It has gradually been widely used in aerospace,precision instruments,defense military and other high-end equipment fields.With the increasing requirements of high-end equipment for surface quality and equipment accuracy,high-speed dry milling of CF/PEEK structural parts had attracted the attention of academia and industry.However,the heterogeneity and anisotropy of CF/PEEK have made the traditional homogeneous material removal mechanism no longer applicable.At the same time,due to the complex surface morphology of CF/PEEK workpiece,the surface was liable to produce processing defects,which seriously reduced the service life,service performance and safety reliability of CF/PEEK structural parts.And it was urgent to clarify the high-speed dry milling mechanism of CF/PEEK.For this,under the support of the National Key R&D Program and the National Natural Science Foundation of China and other projects,this paper focused on the high-speed dry milling of CF/PEEK,and systematically carried out researches on dynamic milling force,surface roughness,cutting specific energy,surface quality and other aspects.The main research contents were as follows:Firstly,the two-dimensional statistical distribution of carbon fiber and its influence on cutting force were analyzed,and the dynamic force statistical model of CF/PEEK high speed dry milling was established.The distribution of carbon fiber on the surface of CF/PEEK was observed and analyzed by scanning electron microscopy,and a twodimensional statistical distribution model of carbon fiber in CF/PEEK was established.A dynamic force statistical model for CF/PEEK milling,which could separate the cutting force of carbon fiber and PEEK matrix,was proposed based on the motion relationship of the milling space forming.The coupling law between CF/PEEK high-speed dry milling force and fiber distribution was revealed by processing experiments,and the process feasibility of high-speed dry milling of CF/PEEK structural parts was verified.Secondly,the influence of carbon fiber distribution anisotropy and its size effect on the cutting force were analyzed,and the dynamic force mechanism models of CF/PEEK high speed dry milling based on size effect were established.Based on the characteristics of carbon fiber distribution anisotropy and size effect,the cutting mechanisms of CF/PEEK in 90° and 0° fiber directions were clarified.The cutting mechanisms of 90°fiber direction were mainly manifested as shearing,impressing,impacting,bouncing and delamination under high frequency impact.The cutting mechanisms of 0° fiber direction were mainly manifested as bending,stretching and delamination,impressing and bouncing under the workpiece self-action.On this basis,the dynamic force mechanism models of CF/PEEK high-speed dry milling in 90° and 0° fiber directions were established respectively,and the influence mechanisms of milling process parameters on CF/PEEK high-speed dry milling force were thus clarified.Then,the formation mechanisms of surface roughness in CF/PEEK high-speed dry milling were clarified based on the impact effect of cutting tool on fibers and the workpiece self-acting mechanism.Combined with the analysis of CF/PEEK high-speed dry milling mechanisms,the impact effect and light rope model were used to clarify the fracture mechanism of carbon fibers.The surface roughness caused by milling cutter motion,spindle vibration,workpiece springback and carbon fiber distribution was mathematically characterized,and the three-dimensional surface roughness formation mechanism of CF/PEEK high-speed dry milling was revealed.The influence of milling parameters(cutting speed,feed per tooth,cutting depth)on surface roughness and the mechanism of impact strength on surface roughness were analyzed by nonlinear regression method.Finally,the specific cutting energy(SCE)distribution characteristics of CF/PEEK high speed dry milling were analyzed,and the surface quality optimization method of CF/PEEK high speed dry milling based on SCE was proposed.According to the mechanisms of CF/PEEK high speed dry milling,the SCE mechanism models of CF/PEEK in 90° and 0° fiber directions were established respectively,and the SCE distributions of CF/PEEK high speed dry milling were clarified.Combined with the mapping relationship between SCE and surface quality,the comprehensive evaluation indexes of SCE for surface quality were established.On this basis,the surface quality optimization of CF/PEEK high speed dry milling based on SCE was realized.