Study On Optimization Of Spray-Assisted Laser Processing Of Carbon Fiber Reinforced Plastic

Carbon Fiber Reinforced Plastic(CFRP)has excellent properties such as light-weight,high-strength,good fatigue resistance,and a high stiffness-to-weight ratio.It has been widely used in various fields,such as aerospace,defense,and military industry.Due to the anisotropy and excellent mechanical properties of CFRP,laser processing of CFRP can easily cause severe thermal damage,which reduces the service performance and shortens the service life of components.However,the traditional cooling methods are challenging to balance machining quality and efficiency.Regulating the laser thermal effect and the cooling effect of the auxiliary medium to achieve a relative balance state between heat and cold is a vital issue in achieving low-damage and high-efficiency processing of CFRP.Based on this,the spray cooling system is optimized in this paper.Optimizing the spray jet parameters regulated the cooling effect of the auxiliary medium on the ablation area.Based on the LevelSet method,a temperature field model for the laser processing of CFRP was established.The temperature distribution characteristics and material removal process of heterogeneous materials were simulated,and the mechanism of laser processing of CFRP was analyzed.The effect of process parameters on machining quality was studied,and the process parameter combination was optimized to regulate the thermal effect of the laser,which in turn achieved the balance between heat and cold,and the machining quality was improved.Ultimately,the internal relation and prediction model between process parameters and machining quality were established by the intelligent algorithm.The main contents of this work are as follows:(1)The flow field model of water film formed by the collision of spray and wall is established.The results show that the uneven distribution of water film thickness induces variations in laser energy distribution.The laser loss rate reaches up to 14% when the offset distance is 0mm.Subsequently,the laser loss rate will gradually decrease as the increase of offset distance.When the nozzle height increases or the gas pressure decreases,the spot diameter decreases gradually.As the nozzle Angle increases,the spot diameter decreases first and then increases.With the rise of nozzle height,the laser loss rate changes little.As the nozzle Angle increases and the gas pressure decreases,the laser loss rate decreases gradually.When the nozzle angle,gas pressure,and nozzle height are 50°,0.2Mpa,and30 mm,respectively,it can achieve better cooling control and improve machining quality.At the same time,the loss rate of laser power is 1.473%.(2)The temperature field model of laser processing of CFRP is established.The results show that the temperature field distribution is wider,and HAZ is larger along the axial direction of carbon fiber.Carbon fiber without resin binding will become loose under stress erosion,and the mechanical properties will be reduced.The temperature rise of heterogeneous materials indicates that the resin is removed before the carbon fiber,and thermal damage will be caused when the removal lengths of carbon fiber and resin are inconsistent.The highest temperature at the bottom of the groove is kept above 6000 K during processing,and the minimum temperature and maximum speed of the steam plume are about2000 K and 33.24m/s,respectively.Therefore,the timely discharge of steam plumes is beneficial for reducing thermal damage.(3)The effect of process parameters on machining quality and its mechanism was studied by the single-factor method,and the optimal range of process parameters was determined.The significance and main effect of process parameters on machining quality were analyzed by orthogonal experiment.After total balance,the optimal combination of process parameters are the offset distance,pulse width,laser power,off-focus amount,and spot overlap percentage is 16 mm,0.1ms,2160 W,0.0mm,and 55%.It can achieve a relative balance state between heat and cold in the machining area and realize low-damage laser processing of CFRP.At the same time,the machining mechanism of spray-assisted laser processing of CFRP is analyzed.The mechanical erosion effect will be weakened due to excessive ablation,and the balance between heat and cold in the machining area will be destroyed,resulting in more considerable thermal damage.Ultimately,the internal relation and prediction model between process parameters and machining quality were established by an intelligent algorithm.The mean relative errors of surface HAZ,groove width,section HAZ,groove depth,and depth-to-width ratio are 4.483%,2.728%,4.392%,1.305%,and3.235%,respectively.The prediction model has high accuracy.It can provide an effective method for predicting the dimensional characteristics of kerf.