Simulation And Experimental Study On Drilling Delamination Of Carbon Fiber Reinforced Polymer Composites

Carbon Reinforced Plastics Fiber(CFRP)is widely used in mechanical engineering due to its excellent overall performance.However,the carbon fiber composite material is difficult to machine because the delamination defects are likely to occur in drilling process,which significantly reduces the material performance and service life.Therefore,in order to have a better application in engineering,it is essential to study the influencing factors and mechanisms on CFRP delamination in the drilling process.The main tasks that have been completed as follows:(1)Aiming at the delamination problem occurring in drilling CFRP laminates,a finite element model of drilling CFRP laminates was established considering that the friction generated at the interface of two layers when the material is damaged and failed will weaken the delamination extension.Furthermore,the finite element model is verified by comparing the cutting force curve and the stratified position of the laminate with the same cutting parameters.Then the stress variation,distribution laws and the delamination distribution of the drilling process are analyzed.(2)The drilling experiments were carried out with different drilling parameters to investigate the effects of drilling parameters on delamination degree.Through the regression analysis of the experimental data,the relationship between axial force and drilling parameters is obtained which can be utilized to predict the axial force.Furthermore,the effect of rotation speed and feed speed on the axial force is analyzed,and the results show that the axial force can be reduced effectively by adopting high rotation speed and low feed speed.(3)The delamination degree of the workpiece was tested experimentally,and it was found that there were delamination defects at both the entrance and exit of drilling.The delamination degree at the drilling exit was much greater than that at the drilling entrance,which was significantly affected by the drilling parameters.A small number of delamination or no delamination occurred at the drilling entrance,which was not affected by the drilling parameters.By extracting the two-dimensional contour feature map of thedelamination defect at the drill exit of the laminate,the maximum aperture surrounding the delamination damage area was obtained,and the corresponding delamination factor is calculated.Then,with the help of regression analysis,the relationship between the delamination factor and drilling parameters was established to predict the delamination degree at the drilling exit.Finally,taking the maximum material removal rate as the optimization objective,the optimization of drilling parameters was carried out which can provide a useful reference for the craft parameters selection in CFRP applications.