Multi-parameter Coupled Optimization Of Infrared Laser Surface Treatment For CFRP Structure

In order to improve the bonding repair effect and interface bonding strength,the basic requirements for the bonding interface are cleaning,activity and uniform micro-roughness.Due to the grinding method used in practical engineering applications has the disadvantages of low surface treatment precision,poor controllability,unfriendly environment and endangers personal health.Therefore,it is especially necessary to explore a new treatment technology with stable surface quality,reproducible process and environmentally friendly.The laser processing of the CFRP surface involves a series of important process parameters(laser energy density,scanning speed,number of scans,amount of defocus,etc.).The laser parameters themselves have a specific mechanism and single factor law for the surface treatment effect and quality of laser CFRP,and the relationship between the parameters and the coupling effect on the surface treatment of CFRP materials is more complicated.In this paper,the laser surface pretreatment of civil aircraft CFRP structure is repaired.Based on the energy density and material damage threshold angle,the laser process parameters primary selection and laser surface treatment scheme design method are used.The infrared fiber laser is applied to the CFRP surface from the perspective of laser single factor test.The micro-morphology and roughness,micro-physical/chemical properties were characterized and analyzed.Based on the mechanical properties of CFRP bonding repair,the multi-parameter coupling optimization of laser process was carried out by orthogonal test method.The results show that the primary selection results in the determination of the surface of the CFRP structure by defocusing,and the defocusing amount f=4 mm;The range of laser energy density and scanning speed is selected;the microscopic characterization results show that the laser treated CFRP structure sample has the highest fiber integrity and resin clearance,the surface roughness increases to Sa=39.481,and the surface free energy increases to gamma=71.26 mN/m,which is superior to the traditional treatment method.After micro-chemical testing,the resin removal of laser-treated surface is relatively complete;the parameter coupling optimization is based on the orthogonal test method,taking the shear strength of CFRP single lap specimen as the evaluation criterion,the optimum parameter group is selected:E_D=1.43 J/cm2,v=800 mm/s,t=3 times;the mechanical test and verification results show that CFRP obtained by laser parameters is more suitable than that obtained by sandpaper polishing sample.The surface bonding performance of structural bonding is obviously improved and more stable.The research results of this paper provide an important technical basis and basis for the application of laser in the field of composite repair of civil aircraft.And it has practical engineering application value for the intelligent and automatic maintenance of CFRP composite materials.