Preparation And Properties Of Glass Fiber Cloth/Epoxy Structural-Functional Integrated Stealth Composites

With the rapid development of electronic information technology,especially the emergence of the fifth generation（5G）communication technology,high-power electronic devices such as satellite communications,wireless networks,and portable digital hardware are increasingly used in human health,information security,and national defense security.However,the following problems,such as electromagnetic interference,radiation pollution and information leakage,have become a major concern of contemporary society.At the same time,the survivability of weapons and equipment on the battlefield is also greatly challenged by the progress of radar detection technology.In response to these problems and challenges,the development of high-performance electromagnetic wave absorption materials has become the key.At present,the research on microwave absorption materials is mainly divided into two aspects.One is to develop light,efficient and low filling microwave absorption functional particles.Although a lot of achievements and breakthroughs have been made in the research of high-efficient microwave absorption particles,there are still many difficulties in the practical products of large-scale production and application of these functional materials.Another aspect is to develop structural microwave absorption materials.In the preparation process of structural microwave absorption materials,it is often necessary to introduce some complex structures such as frequency selective surfaces,patterned resistors,and periodic array structures,which increase the difficulty of the composites molding process and are not convenient for quantitative production.In addition,the introduction of these structures will undoubtedly cause the decline of the bearing capacity of the composites.To solve these problems,this study uses glass fiber cloth（GFC）reinforced epoxy resin（EP）as the matrix material,and uses reduced graphene oxide（RGO）,carbonyl iron and other raw materials that are widely sourced and easy to prepare electrical and magnetic functional particles.Through the combination of experimental and computer simulation research methods and the use of simple,easy and green processes,such as sizing agent modification and repeated impregnation,the glass fiber cloth/epoxy resin was designed from the micro to the macro multi-scale structure,and a structural microwave absorption material with good microwave absorption performance and mechanical properties was obtained.The research contents and main conclusions are as follows:（1）A kind of electromagnetic dual functional glass fiber fabric reinforced material similar to cable structure is designed.Using electric loss absorption material reduced graphene oxide and magnetic loss absorption material flaky carbonyl iron as functional filler,functional filler is successively coated on the surface of glass fiber cloth with water-based epoxy resin sizing agent to prepare electromagnetic dual functional glass fiber cloth.The magnetic loss ability of the flaky carbonyl iron,the dielectric loss ability of the reduced graphene oxide,and the polarization loss generated on the heterogeneous interface work together to improve the microwave absorption performance.After being subjected to 200 W power ultrasonic for 15min,the Zeta potential of graphene dispersion can reach–44.95 m V,with good stability.Ascorbic acid can effectively reduce graphite oxide and increase its C/O from 2.31 to 5.35.The microwave absorption performance of flake carbonyl iron（FCIP）and spherical carbonyl iron（SCIP）were compared.Because of its shape anisotropy,the magnetic properties and microwave absorption performance of flake carbonyl iron were better than that of spherical carbonyl iron.The influence of the coating amount of reduced graphene oxide and flake carbonyl iron on the microwave absorption performance of the electromagnetic dual functional glass fiber cloth/epoxy resin composite The results show that when the coating amount is 1.5 and 30 wt%respectively,the composite has the best microwave absorbing performance,the effective bandwidth is 4.34 GHz（4.04～4.82 GHz,13.44～16.98 GHz）,and the minimum reflection loss is-24.2 d B.At the same time,the bending strength can be increased from 274.38 MPa to 338.44 MPa.（2）The two-dimensional nanomaterial graphene oxide was deposited layer by layer on the surface of the glass fiber fabric by a simple and feasible repeated impregnation process.The graphene was tightly coated on the surface of the glass fiber fabric by using the shear force generated by the evaporation of water in the graphene oxide dispersion.After repeated impregnation,the graphene oxide sheets loaded on the surface of the glass fiber cloth can overlap with each other and form a dense graphene oxide layer on the surface of the glass fiber cloth.After effective chemical reduction of graphene oxide by ascorbic acid,a layer of reduced graphene oxide with good conductivity can be formed on the surface of glass fiber cloth.The glass fibers in the glass fiber fabric are interwoven with each other.This interwoven structural feature can make reduced graphene oxide form a three-dimensional network distribution structure in the composite.Therefore,the conductivity of the composite material is improved accordingly,which provides more paths for charge migration and jump while increasing the propagation path of electromagnetic waves and multiple scattering.The amount of graphene on the surface of glass fiber cloth increases with the increase of repeated impregnation times.When repeated impregnation is 10 times,a dense graphene layer can be formed on the surface.On the surface of the glass fiber cloth loaded with graphene,there are only C,O,and a small amount of Si elements,but no Al and Ca elements can be observed.The conductivity of the composites can reach 0.0547 S/m.Prepared composite（RGO）₁₀@GFC/EP can achieve effective absorption bandwidth of 7.54 GHz and strong absorption of-46.02 d B.The radar cross section（RCS）simulation results show that the PEC board is covered with 2.7 mm（RGO）₁₀@GF/After EP composite material,RCS attenuation value can reach 28.69 d B.Due to the improvement of the interface effect and the deflection effect of graphene on the surface of glass fiber cloth on crack propagation,the mechanical properties of the composites are significantly improved.Compared with GF/EP composites,the flexural strength and modulus of（RGO）₁₀@GF/EP composites increased from 274.38MPa and 10.19 GPa to 381.49 MPa and 14.73 GPa,respectively,and the fracture energy increased by 23.4%to 1.82 J.（3）The design of electromagnetic independent dual network absorbing structure is based on CST microwave studio software,in which（RGO）_n@GF/EP composites are used as electrical network and three kinds of magnetic particals（Fe3O4,FeCo alloy and FCIP）are used as magnetic network.The effects of the distribution positions of the magnetic network layer and the electrical network layer on the impedance matching characteristics,attenuation behavior,field distribution state and microwave absorption performance of the composite microwave absorption structure are studied.The optimal structure is obtained and compared with the measured results.Among the three kinds of magnetic particles,FCIP has the highest saturation magnetization,the best quasi-static magnetic properties,and more significant electromagnetic response characteristics.The complex permittivity,complex permeability,and the ability to lose electromagnetic wave energy are the highest among the three.The distribution of magnetic field in the electromagnetic dual network structure is increasing from top to bottom.Therefore,when the magnetic layer is located at the lower part of the electrical network layer,it will be more conducive for the magnetic network layer to play the role of magnetic loss.If the magnetic network layer just has strong magnetic loss capacity at this time,it can improve the microwave absorption performance of the overall structure to a greater extent.When a 0.2 mm thick magnetic network layer composed of FCIP/EP is introduced at the lower part of the 2.7 mm thick electrical network layer composed of（RGO）_n@GF/EP,the electromagnetic dual network structure composites can obtain an effective absorption bandwidth of 7.95 GHz,which is wider than the effective absorption bandwidth of the simple electrical network structure composites（RGO）_n@GF/EP,and moves to lower frequency.In addition,the actual test results are in good agreement with the simulation results.