Research On Laser Precision Cutting Technology Of Carbon Fiber Reinforced Plastics

Carbon fiber reinforced plastics(CFRP),an advanced composite material,is widely used in aerospace,automotive and sport equipment due to its high specific strength and specific modulus.However,the method of machining CFRP still uses the traditional mechanical processing method,which are prone to generate various machining defects such as delamination,cracks,mechanical thermal damage,and tools wear.The laser processing method has the characteristics of non-contact and no tool consumption,which provides unique advantages for overcoming the problems of mechanical processing CFRP at present.However,laser processing CFRP is easy to produce HAZ,which has an impact on engineering application,and the relevant basic theory research is not sufficient.This paper,focusing on laser precision machining CFRP,has conducted the theoretical analysis,numerical simulation and experimental research of laser processing CFRP.The main work and conclusions are as follows:(1)Research on temperature field evolution of laser processing CFRP.Based on COMSOL Multiphysics,the temperature field model of pulsed laser processing on CFRP was established,then analyzed anisotropy characteristic of CFRP and the influence of pulsed laser parameters on the temperature field.The results show that CFRP temperature field have obvious anisotropy characteristics.Additionally,laser parameters have significant effect on CFRP temperature field.In order to further study the formation of HAZ,the process of CFRP material removal was conducted.The unequal velocity transfer process of heat between resin and carbon fiber was observed in the established model,and it could be divided into three stages,and the results have been experimentally verified.(2)Process experimental investigation on pulsed lasers cutting CFRP materials.The millisecond laser and picosecond laser were used for drilling CFRP plates.Based on these,we have studied the influence of key parameters such as pulse width,scanning speed,laser power,repetition frequency,auxiliary gas pressure,etc.on HAZ.The results show that the higher the scanning speed,the smaller the HAZ,but too high scanning speed will also cause the processing efficiency to decrease.And the higher the laser power,the larger the HAZ,but the processing efficiency will also increase.And reducing repetition frequency,the HAZ will also decrease.In addition,using Ar gas as auxiliary gas during processing effectively,the thermal damage will reduce,and its pressure has little effect on HAZ.Under high-energy laser processing,the CFRP specimens were cut by laser with water contacting lower surface,its HAZ can significantly reduce,while its efficiency was not diminished.Finally,comparing the processing quality of lasers with different pulse widths,the millisecond laser has poor processing and high processing efficiency,while the picosecond laser has good processing quality but low efficiency.(3)Influence of HAZ on tensile strength of CFRP.According to the influence of laser cutting CFRP,the HAZ of different widths can be obtained by selecting the laser parameters,and then the tensile strength tests were performed.The results show that the tensile strength decreases linearly with the increasing of the HAZ width.The tensile strength of 1mm samples decrease by about 122 MPa/mm HAZ,and the 2.5mm samples decrease by about 33.9 MPa/mm HAZ.As the thickness of the CFRP laminate increases,the influence of HAZ on the tensile strength would be weakened.Finally,the mechanism of HAZ-induced tensile strength reduction was explained by numerical simulation: due to the resin damage within the HAZ,the tensile load cannot be effectively transferred through the fibers within the HAZ,which reduces the overall loads-bearing capacity of the CFRP sample,causing its strength decreased.