Forming Process And Properties Of Aluminum Matrix Composites Reinforced By Carbon Fiber With Helical Structure

Because of its light weight,high strength,small thermal deformation,good electrical conductivity,corrosion resistance and electromagnetic wave shielding function,carbon fiber reinforced composite materials are widely used in the manufacture of space shuttle cargo doors and arms,high gain antennas for spacecraft,transmission system components for automobiles,secondary structural materials for offshore platforms,high speed train components and robot parts,etc.Since the elongation of long continuous straight carbon fibers is less than 2%,it is almost impossible for the current straight carbon fiber reinforced aluminum matrix composites to carry out subsequent large plastic deformation,and the application range is somewhat limited.Compared with the traditional linear structural composites,the curve-reinforced composites,especially the helical structures,have considerable advantages.The helical fibers can usually tolerate large elongation while still retaining low strain,due to their geometrical shapes.The helical structure has better toughening ability than the straight carbon fiber structure in guiding crack propagation and stress dispersion.For high performance composite materials of high strength,low toughness match the problem of insufficient,this paper puts forward a kind of helical carbon fiber reinforced aluminum matrix composites preparation and forming process,solved because of the low carbon fiber elongation and impact overall toughness of the composite material,is a kind of new method of carbon fiber composite materials forming secondary processing.The key is to introduce the three-dimensional helical carbon fiber into the aluminum matrix composite.With the increase of pitch and the decrease of helical Angle,the helical carbon fiber successfully realizes the effect of synchronous elongation deformation with the aluminum matrix,improving the overall toughness and impact resistance of the composite material.The preparation and forming process and equipment of helical carbon fiber reinforced aluminum matrix composite with independent intellectual property rights are designed and developed.The forming law of the composite is analyzed,which provided experimental and theoretical basis for the forming process of carbon fiber composite.The main research contents and results are as follows:(1)Based on the thermodynamics of interfacial reaction of composite materials,the possibility of interfacial reaction was predicted,and the interfacial migration kinetics of Cu coating was used to describe the interfacial layer formation kinetics.According to the formation mechanism,the interfacial migration process of Cu coating was divided into two parts:before and after the solidification of aluminum matrix.The solution thickness of Cu coating was calculated by mathematical analysis,and the minimum thickness of Cu coating was calculated to be 0.35μm.In addition,the optimal helix Angle β is 54.73°by theoretical calculation.The results show that the helical Angle can help the helical carbon fiber and aluminum matrix deformation and elongation synchronously,reduce the internal stress between the helical carbon fiber and aluminum matrix,and the force acting on the helical carbon fiber is minimal.(2)In order to protect the reinforced carbon fiber during the high temperature preparation of composite materials,Al4C3 brittle phase was prevented from forming at the interface.In this paper,a scheme of electroless copper plating for the surface modification of helical carbon fiber is developed.According to the theoretical calculation results of the thickness of the coating,it can protect the helical carbon fiber enough while the thickness of the coating does not affect the subsequent plastic drawing deformation.In view of the large specific surface area of helical carbon fiber,the fibers tend to agglomerate due to intertwine.In order to completely remove the adhesive layer on the surface of helical carbon fiber,this study adopted the process of high temperature burning and ultrasonic acetone.By comparing the four groups of 15min,30min,45min and 60min,the best sintering process was determined to hold at 440℃ for 45 minutes.The addition of ultrasonic wave can promote the growth and rupture of microbubbles in acetone solution,thus causing local high pressure and high temperature,and accelerate the decomposition of rubber layer on the surface of spiral carbon fiber.(3)The preparation process of helical carbon fiber reinforced aluminum matrix composite material is designed,and the carbon fiber reinforced aluminum matrix composite bar with directional helical structure is prepared successfully,which can be used directly or can be used after plastic deformation according to the dimensions required by the final parts.A special mold is designed for the preparation of the composite,which can control the prefabricated parts well in the center.The preparation process is as follows:the graphite mold is preheated to 550℃ and kept warm,pure aluminum(1060,99.6%)is heated to 800℃ and kept warm for 30 minutes,the surface slag is removed and poured,the pouring temperature is 750℃.interfacial structure of Al/Cf composite.Based on the dynamics analysis of the interfacial structure of Al matrix and reinforced carbon fiber composites,the dynamics model of Al/Cf interfacial structure of Al/Cf composites is established.(4)According to the characteristics of helical carbon fiber,the plastic drawing deformation process matching with it was designed.And the numerical simulation method is used to simulate a reasonable die Angle of α=7°,and on this basis the mold design and sample preparation.After 5 times of drawing,the total deformation of the composite material reaches 58%.Under the premise of not exceeding the theoretical elongation limit of helical carbon fiber,the maximum extension of the composite material is increased,and the total elongation reaches 203.3%.The tensile strength of helical carbon fiber reinforced aluminum matrix composite is 69.61MPa,and the tensile strength of industrial pure aluminum matrix can be increased by 16.02%,and the bending strength is 189MPa,and the lifting effect of aluminum matrix can be increased by 37%.Compared with the helical carbon fiber composites with helical angles of 40°,50° and 60°,the larger the helical Angle is,the lower the strain energy is,the greater the deformation ability is,and the higher the external load tolerance is.As a kind of advanced structural material with high modulus and impact resistance,helical carbon fiber reinforced aluminum matrix composite has a broad application prospect in spacecraft structure and automotive lightweight fields.