Research On Laser Cleaning Mechanism And Surface Modification Of Carbon Fiber Reinforced Polymer

Carbon fiber reinforced polymer has many excellent properties,such as high specific strength,high specific modulus,lightweight and fatigue resistance,so it has a wide range of applications and development prospects in aerospace,automotive,petrochemical and other industrial fields.However,it is easy to produce various surface defects in the process of manufacture and application,which will lead to poor stress transfer between carbon fiber and resin,and greatly affect the surface properties of composites.In this paper,a method of laser cleaning and surface modification composite treatment is proposed.The interaction mechanism between laser and carbon fiber reinforced polymer is studied by finite element method and heat conduction theory.The laser-induced plasma spectroscopy(LIBS)is used to detect the laser cleaning pretreatment process on-line.The nanosecond pulse laser is used to pretreat carbon fiber reinforced polymer,and the relationship between laser parameters and surface properties,as well as the time-effect of the surface are studied.The effect of laser cleaning on bonding strength is analyzed by single lap tensile test.The effect of laser cleaning and surface modification on the interfacial bonding strength is obtained.The details are as follows:(1)The heat conduction model of carbon fiber reinforced polymer treated by pulse laser was established,and the mechanism of surface material removal was revealed.The finite element software(COMSOL)was used to simulate and obtain the temperature variation of carbon fiber reinforced polymer under pulsed laser irradiation.The ablation mechanism of epoxy resin and carbon fiber was analyzed,and the removal threshold of surface resin was obtained.The results showed that the threshold of surface resin laser removal was about 8W.It provides the mechanism basis for the experimental study of laser cleaning in the future.(2)A laser-induced plasma spectral detection method was proposed to realize the on-line detection of the process of laser cleaning carbon fiber reinforced polymer.The experimental platform of laser-induced plasma spectroscopy was set up,and the plasma spectra with different laser parameters were collected,and the relationship between the laser cleaning effect and the intensity of laser-induced plasma line was obtained.Meanwhile,the threshold value of surface resin cleaning was obtained.The results showed that the on-line detection of cleaning process is effectively,and the element spectral lines in 350nm~700nm band could be used to analyze the surface composition of carbon fiber reinforced polymer,and the threshold of laser removal of clean surface resin is about 10.68 mJ.The results provided technological basis and technical support for the intelligent integrated application of laser cleaning carbon fiber reinforced polymer.(3)The relationship between laser parameters and surface properties was established,and the optimal parameters and bonding time of carbon fiber reinforced polymer were obtained.The surface morphology is observed by scanning electron microscope(SEM)and the surface state was analyzed.The contact angle of the surface treated with different parameters by contact angle measuring instrument.The relationship between surface state and surface wettability was revealed,and the timeliness of laser pretreatment was obtained.The information of surface chemical structure was obtained by Fourier transform infrared spectroscopy(FTIR),and the effect of laser pretreatment on surface chemical activity was studied.The results showed that the surface state was divided into four stages: incomplete removal stage of surface resin,complete removal stage of resin,fracture stage of top carbon fiber and affected stage of deep carbon fiber.The analysis showed that the surface pretreated by16 W is the best surface condition.(4)The relationship between laser cleaning surface state and bonding strength was obtained.The adhesive properties and interface failure modes of different surface states were analyzed by single lap tensile test.The results showed that compared with the untreated and mechanically polished surface,the maximum bonding strength of carbon fiber reinforced polymer processed by laser cleaning is 1.6 times higher than that of the untreated surface,and he main failure mode is cohesion failure.