Study On Preparation And Shielding Of Ultra-Thin Carbon Fiber Composite Materials

Carbon fiber composite materials have been widely used in the aerospace field because of their advantages such as light weight and high strength.In recent years,with the rise of artificial intelligence,big data,and 5G communications,the manufacturing industry is rapidly developing towards information and intelligence.This requires composite materials not only to have excellent mechanical properties,but also to have good electromagnetic shielding properties.Therefore,how to improve the electromagnetic shielding effectiveness of composite materials has gradually become a hot topic for scholars in recent years.At present,scholars at home and abroad have done a lot of research on improving the electromagnetic shielding effectiveness of composite materials and achieved certain results.Now an effective way to improve the electromagnetic shielding effectiveness of composite materials is to add conductive fillers to the resin matrix,and improve the conductivity and electromagnetic shielding effectiveness of composite materials by increasing the content of conductive fillers.Although these methods effectively improve the electromagnetic shielding effectiveness of composite materials,they lead to a large loss of mechanical properties of composite materials.In order to find a new way to improve the electromagnetic shielding effectiveness of composite materials to achieve the purpose of synergistically enhancing the mechanical properties and electromagnetic shielding effectiveness of composite materials.This article starts from the mesoscopic scale of the composite material,controls the microstructure inside the composite material by reducing the thickness of the prepreg,reduces the scale and proportion of defects such as the resin-enriched area and pores between the composite layers,and improves the conductive mesh inside the composite Quality,and ultimately achieve the purpose of synergistically enhancing the mechanical properties,electrical conductivity,and electromagnetic shielding effectiveness of carbon fiber composites.The main contents and conclusions of this article are as follows:(1)A combined pneumatic-mechanical process,simulation analysis and experimental verification was used to build a carbon fiber widening-pre-soaking experimental platform.Carbon fiber prepregs of four thicknesses were prepared by optimizing process parameterssuch as fiber tension,pressure,velocity of airflow inside the pneumatic chamber,and the diameter of the metal convex and concave rolls and their coordinate positions.Observation and comparison of its microstructure found that the distribution of fibers and resin in the thin prepreg was more uniform,and there was almost no fiber deflection.(2)Composite unidirectional laminates with a thickness of 1 mm were prepared from four different thickness prepregs.Observation and comparison of the internal microstructure of the laminated board found that the thinning of the prepreg can significantly reduce the scale and proportion of defects such as resin rich areas and voids in the composite material,which makes the interlayer resin layer thinner or even disappears,which significantly improves Uniformity of fiber and resin distribution in composites.(3)The test results of the mechanical properties of the laminated board samples show that as the thickness of the prepreg is reduced from 0.10 mm to 0.02 mm,the tensile strength of the laminated board is increased by about 15%;the acoustic emission system monitors the preparation of the thin prepreg Acoustic waves caused by fiber breakage and interlayer cracking appear later in the tensile test of the laminated laminate samples;brittle fractures are the main failures of laminates prepared from thin prepregs,while laminates prepared from thick prepregs break.Explosive failure at this time indicates that the thinning of the prepreg can significantly improve the ability of the composite material to resist crack initiation and propagation.(4)Through the comparison of the static resistivity and the dynamic resistivity of the four kinds of laminate samples under tensile load and temperature load,it is found that as the thickness of the prepreg decreases,the resistivity decreases significantly in the thickness direction of the laminate,but the fiber The resistivity in the direction is basically unchanged.The static electromagnetic shielding effectiveness and dynamic electromagnetic shielding effectiveness of the laminate under temperature and tensile loads are calculated using the resistivity and electromagnetic shielding theoretical formulas of the laminate.Through comparison,it is found that the thinning of the prepreg can significantly improve the electromagnetic shielding effectiveness of the laminated board;the electromagnetic shieldingeffectiveness of the four laminated board samples increases linearly with increasing temperature,and their electromagnetic shielding effectiveness increases with tensile load.Daxian slowly and linearly decreases and reaches a certain critical point and then decreases rapidly in a non-linear manner.When subjected to external loads,laminates made of thin prepreg have more stable electromagnetic shielding effectiveness.The test results of the shielding effectiveness of the laminated board confirmed that the thinning of the prepreg improves its shielding effectiveness,but there are some differences between the measured and calculated values,indicating that the electromagnetic shielding effectiveness of composite materials is not only related to the test frequency and resistivity.It is also affected by other intrinsic parameters.