Study On Graphitization Uniformity Of Pan-based Carbon Fiber Irradiated By Laser

Polyacrylonitrile-based carbon fiber is a kind of microcrystalline graphite material obtained by pre-oxidation,carbonization and graphitization process of pan-based filament.It has high specific strength,high specific modulus,corrosion resistance,high temperature resistance and high processability.Based on pan carbon fiber,this paper focuses on the uniformity of temperature distribution and graphitization degree of carbon fiber under laser irradiation,and analyzes the influence of temperature uniformity on thermodynamic properties.The energy emitted by laser irradiation has the characteristics of gaussian distribution.Firstly,a gaussian moving heat source model is established based on the characteristics of laser beam energy to complete the thermodynamic parameter transfer of carbon fiber materials from the macroscopic structural scale.by using the finite element method,based on the Ansys/Workbench platform,the thermal performance parameters of carbon fiber materials are set,and the gaussian heat source and temperature boundary conditions are applied through the "thermal analysis" module to ensure the continuity of laser action.The results show that the temperature distribution in the cross section of carbon fiber bundle mainly depends on the laser power,spot diameter,wire speed and the number of lasers.Increasing the laser power,reducing the spot diameter,reducing the wire speed and increasing the number of lasers can effectively increase the fiber temperature,which is beneficial to the increase of graphitization degree.The temperature uniformity index formula was defined and the influence of different conditions on the temperature uniformity of carbon fiber was analyzed.The temperature distribution of the laser irradiated moving carbon fiber filament in the graphitization reaction system was solved to analyze the radial non-uniformity rule of the laser's effect on the graphitization of carbon fiber.The results show that decreasing the laser power,increasing the spot diameter and decreasing the wire speed can contribute to the uniformity of fiber temperature distribution to some extent.Increasing the number of lasers can greatly improve the uniformity of fiber temperature.Three lasers irradiate carbon fiber at 120° to solve the problem of uneven temperature distribution.The thermodynamic model of carbon fiber in thermal-chemical reaction was established.Based on the Workbench platform,the thermodynamic properties of carbon fiber were numerically analyzed by means of solid-flow coupling.The results show that the thermal stress,thermal strain,axial type and axial type of carbon fiber increase with the increase of temperature.The thermal stress generated by three lasers is much less than that generated by a single laser,so the higher the temperature uniformity,the smaller the thermal stress generated by the fiber.