Research On The Reinforcement Technology And Joint Performance Of Carbon Fiber Laminates

Carbon fiber composite materials have excellent properties,such as light weight,high specific strength and stiffness,and good wear resistance,and have been widely used in aerospace and other fields.With the increase in the amount of composite materials used,various forms of damage can occur in the material structure in practical applications.In order to avoid economic loss and waste of material structure,many scholars began to carry out repair research.Among them,the adhesive repair technology is highly valued for its excellent performance.In this paper,the mechanical properties of the bonded joints are improved by using different methods and the influence parameters are optimized to enhance the reliability of the joints.The laminate was prepared using T300 carbon fiber prepreg as a raw material(diameter 7?m,density 1.76 g/cm~3).After the laminates have been properly cut and surface treated,they are bonded with 3M DP270 adhesive.The main research contents of this paper are as follows:(1)Ultrasonic vibration can accelerate the fluidity of the liquid adhesive,so that the adhesive and the surface of the laminate are more closely bonded,thereby improving the mechanical properties of the bonded joint.Ultrasonic vibration-assisted preprocessing of the bonded joint before the adhesive is cured can effectively enhance the uniaxial tensile properties of the joints.During the experiment,four different preprocessing times(5 min,20 min,40 min,60 min)and four different preprocessing powers(200 W,300 W,400 W,500 W)were set to study the effect of ultrasonic time and power on the tensile properties of the bonded joints.And compared with the specimen without ultrasonic vibration preprocessing,the maximum growth rate of the shear strength and stiffness of the bonded joint was obtained.The fracture morphology of the joint was further analyzed,and the percentage of the adhesive surface area of the joint on the area of the entire overlap area was calculated by software,which was consistent with the trend of the experimental results.(2)Dispersion of nanoparticles in the adhesive can reduce bubbles and voids in the adhesive while improving the tensile and shear strength of the adhesive.Three different mass fractions(1.5%,2.0%,2.5%)of carbon nanotubes(CNTs)were dispersed in 3M DP270 adhesive to study the effects on the uniaxial tensile properties and three-point bending properties of the bonded joints.Comparison with the adhesive joints in the adhesive without CNTs particles to obtain the best CNTs mass fraction and growth rate.After SEM analysis of the joint after fracture,after the CNTs particles are dispersed in the adhesive,some of the bubbles in the adhesive are filled with the nanoparticles,which can effectively improve the performance of the joint.(3)After dispersing the best mass fraction of CNTS particles in the adhesive,the ultrasonic vibration assisted preprocessing of the bonded joint was carried out to study the improvement of the mechanical properties of the bonded joint when the nanoparticles and ultrasonic assisted synergistic action.In the case of synergistic enhancement of the two effects,the ultrasonic preprocessing power was changed to200 W,300 W,400 W,500 W,respectively,and the optimal ultrasonic preprocessing power and the maximum growth rate of the mechanical properties of the bonded joint were obtained.The fracture morphology of the joint was analyzed.