Simulation Study And Experimental Verification On Laser Surface Removal Of Carbon Fiber Composites

Carbon fiber composites have been widely used in the field of aeronautics and astronautics because of their high specific strength,excellent specific modulus,good fatigue resistance,and excellent designability.In the process of composite material maintenance of civil aircraft,in order to improve the bonding effect of carbon fiber composite structure,the original surface paint layer needs to be removed to obtain a bonding interface with good cleanliness and stability.The traditional surface paint removal methods have some disadvantages,such as low precision,poor controllability,and unfriendly environment.As a new non-contact paint removal technology,laser surface removal technology has the advantages of economical,high efficiency and controllability,and has been gradually applied to aircraft paint removal.Firstly,in this thesis,the changes of temperature and stress of paint layer and carbon fiber composite during laser surface removal of two model paint layers are studied by simulation.The removal effect of paint layer under this Law and whether there is damage to carbon fiber composites are tested by experiments.The finite element model of laser paint removal is established by using COMSOL Multiphysics.The effects of different laser parameters(laser power,spot diameter and scanning speed)on the temperature and stress of paint layer and carbon fiber composites are simulated.The simulation results are shown as follows: with the increase of laser power,the shorter the time for the paint layer to reach the gasification temperature,the greater the stress,and the shorter the time required to remove the paint layer;the smaller the spot diameter,the shorter the time for the paint layer to reach the gasification temperature,the greater the stress,and the shorter the time required to remove the paint layer;the slower the scanning speed,the shorter the time for the paint layer to reach the gasification temperature,the greater the stress,and the shorter the time required to remove the paint layer.In this thesis,the laser paint removal equipment is used to complete the paint removal experiment corresponding to the laser power,spot diameter,and scanning speed set in the simulation.The removal effect of the surface paint layer and the damage of the carbon fiber composite are judged through the scanning diagram of the electron microscope.The influence of different laser parameters on the static properties of the carbon fiber composite after removing the paint layer is analyzed through the tensile experiment,so as to verify whether the carbon fiber composite is damaged.The experimental results show that when the laser power is 12 W,the spot diameter is 0.4 mm and the scanning speed is 400 mm/s,the removal effect of the surface paint layer is better,and the fracture trace of the carbon fiber strip is not found in the SEM image.The tensile test results of carbon fiber composites before and after paint removal were analyzed,maximum relative error of tensile strength,maximum relative error of maximum load and maximum relative error of tensile elastic modulus in test results,the above three kind of relative error within the error range of 5% of the experimental data,which shows that the static properties of the carbon fiber composite before and after the paint layer is removed are intact and there is no damage to the carbon fiber composite.The results of this thesis can provide a certain reference basis for laser surface paint removal of carbon fiber composites.