Research On The Milling Surface Quality Of Glass Fiber Resin Matrix Composites

The glass fiber reinforced resin matrix composite material(GFRP)has high specific strength,high specific rigidity,high temperature resistance,creep resistance,good corrosion resistance and relatively cheap price,and has been widely applied in the fields of aerospace,automobile,construction and military industry.However,due to GFRP's non-uniformity,anisotropy and poor thermal conductivity,the cutting tools are easily worn out,and the defects such as poor surface finish,rough surface,and delamination tear are prone to occur during its cutting process.Therefore,GFRP is more difficult to process than normal metal materials.In this paper,the GFRP milling experiment is carried out by using cemented carbide end milling cutter.The factors affecting the machining performance and surface quality of GFRP are studied by means of theoretical analysis and experimental research.The main contents are as follows:(1)The effects of spindle speed,milling depth and feed rate on the surface roughness of GFRP are studied.The experimental results of GFRP milling show that the feed rate has a vital effect on the surface roughness,the spindle speed is the second,and the milling depth is the lowest.The regression models based on orthogonal experiment are established and the significance test is done.The error between the experimental values and the predicted values is small,which indicates that the models are well fitted.Scanning electron microscopy(SEM)is used to observe the surface morphology.It is found that matrix debonding,fiber fracture and pullout occurs on the machined surface,resulting in the formation of resin coating and plough surface morphology.The transverse fiber undergoes bending fracture and compression fracture,the fracture morphology is extremely irregular,and the surface quality is extremely poor.While the longitudinal fiber has good shear fracture surface quality,good smoothness and flatness.(2)The influence of milling parameters on GFRP three-way milling force and milling stability is studied.Through the experiment of milling force measurement and the analysis of the corresponding data,it is found that the milling force decreases continuously with the increase of spindle speed,and increases significantly with the increase of feed rate and milling depth.The feed rate has the most significant effect on the milling force,the milling depth is the second,and the spindle speed is generally remarkable.According to the spectrum analysis of the Y-direction milling force,the amplitude of the tooth passing frequency generally decreases first and then increases slightly with the increase of the spindle speed,and increases with the increase of the feed rate and the milling depth.Milling depth has the most significant effect on milling stability.(3)The types and formation mechanism of surface defects,and the influence of milling parameters on delamination factors in GFRP milling are analyzed.Surface defects mainly include delamination,burrs,and damage.The influence of milling parameters on axial force and delamination factor is basically the same,which increases with the increase of feed rate and milling depth,and decreases with the increase of spindle speed.Milling depth has the most significant influence on axial force and delamination factor.The regression model is established based on the Taguchi orthogonal experiment.The results show that the model fits well and has high accuracy,which can effectively predict the size of the delamination factor.