Civil Aircraft Composite Structure Based On Laser Surface Treatment

Composite material structure has been widely used in the field of aviation, and it will inevitably suffer from various types of damage throughout the life process. In order to maintain the structural integrity of civil aircraft, it is economically feasible method to maintain damaged composite material structure in scope of repair course and guarantee its continuous airworthiness requirements, combined with the specific size and type of injury. The maintenance manner of composite material is mainly adhesion bond. Before the adhesion bond repair, remove damage, then dispose and maintain parent surface, in order to improve adhesion bond maintenance effect. In the engineering, handwork and pneumatic polishing are widely used to handle surface of maintenance parent, and there are inefficiency, high energy consumption, unfriendly environment and unstable surface properties and other shortcomings. Therefore, exploring new surface pretreatment technology not only can obtain a stable, controllable and reproducible surface microstructure physical chemistry property which is beneficial for adhesion bond maintenance effect, but also can significantly reduce the impact of human factors in the maintenance process and the impact of health of serviceman.Laser is a light amplification of stimulated radiation, which is widely used in cutting, welding, etching, positioning, surface treatment and other fields.In the field of maintenance field of composite materials of civil aircraft, Boeing, Airbus and several research institutions in Germany and Austria have launched theoretical research and practical application exploration of laser surface treatment technology applying to composite material repair in recent years. This paper regards carbon fiber/epoxy resin composite material used by a type of civil aircraft as research object, uses ultraviolet laser micro and nano fabrication device with a wave length of 355nm to do laser surface treatment of different parameters for adhesion bond maintenance parent. This paper does representation analysis for microcosmic physical chemistry features of parent surface after laser surface treatment, uses single lap sample mechanical properties testing to do contrast test and verification for effects of adhesion bond maintenance, and builds internal relation of microcosmic physical chemistry features of parent surface and effect of adhesion bond maintenance from micro perspective. The main research contents of this paper are as the following:(1) Research on surface micro physical and chemical properties of parent body of composite material after laser surface treatmentResearch the variation and stability of surface micro structure (micro morphology, roughness), physical characteristics (contact angle and surface free energy), chemical characteristics (chemical elements and concentration of functional group) of parent body, and contrast with mechanical roughening method.(2) Research on internal relations between surface micro physical and chemical properties of service parent body and cementing strengthAccording to mechanical interlocking theory, electrostatic adsorption theory, chemical bond theory and other interface adhesion theories of interfacial cementation, qualitatively analyze the inner mechanism of surface micro characteristics improving adhesion effect of cementation service interface after laser surface treatment, build the internal relation between surface micro characteristics and service interface cementing strength, and contrast with traditional mechanical roughening method.(3) Mechanics performance test on single lap samples and maintenance effect verificationProceed laser surface treatment on the surface of lap joint part of single lap samples, use vacuum bag to solidify and shape, proceed mechanics performance test on single lap samples and maintenance effect verification.The research result shows that after proceeding laser surface treatment on composite materials, comparing with the original surface and mechanical roughening surface, the surface roughness of parent body Ra is markedly increased, the micro morphology becomes more uniform, and more stable and controllable; the double liquid contact angle test shows that after laser treatment, the surface free energy increases to 78.01 mJ/m2; surfaceO1s/C1s increases to 31%, proportion of active and functionalized group is obviously higher than original surface and mechanical roughening surface. According to interface adhesion theory, all variation of surface micro physical and chemical characteristics above are helpful to cement maintenance interface adhesion and improve maintenance effect. The single lap mechanics test result shows that comparing with mechanical roughening method, the mechanical property of single lap samples treated by laser is obviously increased, and the coefficient of dispersion becomes smaller.The research result of this paper shows that the feasibility of laser surface treatment technology applying to the field of civil aircraft composite material maintenance, and it supplies theoretical basis and technical support to engineering application of laser surface treatment technology.