Study On Absorption Properties Of Carbon Fiber In GHz Band

With the development of technology and the continuous renewal and application of electronic products,electromagnetic pollution is becoming more and more serious.It is an effective method to reduce or eliminate electromagnetic wave pollution by using absorbing materials,in which carbon fiber composites are an important part of absorbing materials.The carbon fiber composite material not only has the characteristics of light weight,high strength,good shock resistance,high temperature resistance,corrosion resistance,easy integral forming and the like,but also can attenuate electromagnetic waves through electric loss and scattering effect,and has a wide application prospect.In this paper,the factors affecting the absorbing properties of carbon fiber composites in the 2~18GHz band and the absorbing mechanism are mainly studied.At the same time,a muti-layer carbon fiber resistive film absorber for broadband absorption in the microwave band is designed.The main research work has the following aspects:(1)The theoretical basis of carbon fiber used in metamaterial wave absorption is analyzed,which fully verifies the feasibility of carbon fiber used in metamaterial wave absorption and provides a new idea for the development of carbon fiber wave absorption materials.It provides a theoretical basis for the following simulation analysis of the application of carbon fiber in absorbing waves of super materials.(2)The factors affecting the microwave absorbing properties of carbon fiber composites are studied,and the microwave absorbing mechanism of carbon fiber composites is discussed.The simulation results show that the carbon fiber has strong wave-absorbing performance in the range of proper length-diameter ratio,and the changes of electrical conductivity and axial direction of the carbon fiber have an important influence on its wave-absorbing performance.It is verified by simulation that the strong absorption of electromagnetic wave by the carbon fiber absorbing material is not only due to the electrical effect of the carbon fiber absorbing material itself,but also due to the magnetic effect of the carbon fiber absorbing material due to the structure of the carbon fiber and the bottom metal plate.Therefore,the carbon fiber absorbing material is not generally believed to have only a simple electrical effect,but has both an electrical effect and a magnetic effect,resulting in a strong absorption phenomenon of the carbon fiber absorbing material.It has important reference significance for designing carbon fiber composite materials with strong wave absorbing properties.(3)A metamaterial absorber is designed to achieve broadband absorption in the microwave band.By combining carbon fiber resistive film/dielectric laminated structures with different widths,electromagnetic waves with different wavelengths can be captured,so that multilayer impedance is gradually matched,and broadband wave absorption is realized.The simulation results show that in the frequency range of 8.6GHz to 14.9GHz,the reflectivity of multilayer carbon fiber resistive film/dielectric layer absorber is less than-10 dB,the working bandwidth reaches 6.3GHz,and the relative absorption bandwidth reaches 53.6%.By observing the electric field and magnetic field distribution of multi-layer carbon fiber resistive film/dielectric layer absorber at different frequencies,its resonance mode is coexistence of electric resonance and magnetic resonance.The resonance frequency is almost inversely proportional to the width of resistive film layer.Due to the pyramid structure with different widths,this resonance mode is supported in a very wide frequency,resulting in strong broadband absorption.The simulation results have important reference significance for the future preparation of specific multilayer carbon fiber resistive film/dielectric layer absorbing materials.