Research On Prediction And Control Of Thrust Force In Drilling CFRP Laminates

Carbon fiber reinforced resin matrix composites(CFRP)are widely used in manufacturing industry due to their high specific strength,high specific modulus,corrosion resistance,fatigue resistance and other advantages.However,due to the anisotropy of mechanical properties and heterogeneity of the structure,they are prone to delamination,burr,spalling and other processing defects during processing.Drilling force is one of the most important physical quantities in CFRP processing,and its value is closely related to tool wear condition and hole-making quality.The dynamic cutting force in CFRP drilling can be accurately predicted and rationally controlled by advanced intelligent technology,which can effectively alleviate various machining damage caused by excessive fluctuation of drilling force in CFRP drilling process.In order to predict and control the dynamic thrust force in CFRP drilling process,a new CFRP drilling thrust force prediction model was established by combining experiment and theory,mechanism and data-driven method.Based on the critical thrust force and combined with fuzzy control intelligent technology,the simulation and experimental research on adaptive control of CFRP drilling thrust force were carried out,aiming at improving the quality of hole-making and promoting the intelligent development of CFRP cutting.The specific research contents of this paper are as follows:(1)The effects of drilling parameters on thrust force and hole-making quality(delamination defect,hole wall surface roughness,outlet surface damage area and burr length)were studied by drilling experiments of CFRP laminates,and the mechanism interaction between thrust force and hole-making quality in CFRP drilling process was revealed.(2)The thrust force prediction model of CFRP drilling was established based on mechanism and data-driven mode,in order to solve the dual problems such as the current mechanism model has many parameters and large error,and the data model cannot reveal the drilling mechanism.Firstly,the thrust force model of CFRP drilling with twist drill was modified,and the mechanism model prediction error compensator was constructed by using various data information and neural network.Secondly,a CFRP joint thrust force model was established by using drilling mechanism and data-driven method,and the accuracy of the model was tested in sample data set and random data set.(3)The mechanism of delamination defect and the loading condition during delamination were analyzed.The force on the twist drill was simplified as concentrated force and uniform force on the disk,and then the critical thrust force model of delamination defect was analyzed by plate and shell theory,fracture mechanics and elasticity mechanics.Secondly,a calibration experiment of the critical thrust force of CFRP drilling stratification was carried out.The variation of the critical thrust force of drilling stratification with undrilled thickness was discussed and compared with the critical thrust force model.(4)The simulation and experimental study of adaptive control of thrust force in CFRP hole making process was carried out based on fuzzy logic intelligent control technology.A three-stage thrust force model was established to characterize the hole-making process of CFRP.An thrust force controller was designed by using fuzzy logic,and the simulation and experimental study of adaptive control of drilling force were carried out based on the model.The results show that it is feasible to control the thrust force of hole making intelligently by using the fuzzy logic control algorithm combined with the machining characteristics of CFRP;In addition,adjusting the thrust force according to the simulation information can effectively reduce the hole making defects and improve the hole wall quality.Finally,according to the established mechanism model and critical force,the method of drilling CFRP based on critical feed was adopted,and the hole quality is good.