Design Of Metamaterial Absorber And Its 3D Printing Preparation Technology

Microwave absorbing materials are widely used in militarv and civilian fields such as electromagnetic radiation protection,the reliability of high-precision instruments,and the stealth of weapons and equipment.The electromagnetic performance of metamaterial absorbers can be controlled through the design of micro unit structure.However,the difficulty in balancing the molding accuracy and efficiency caused by the complexity of micro unit structure is a problem that needs to be solved urgently.The feature of 3D printing layer by layer accumulation molding provides an effective scheme for the preparation of metamaterial absorbers.This paper explores the photothermal dual solid 3D printing method of microwave absorber that regulates the electromagnetic parameters of materials by driving the distribution direction of carbon fibers in the resin matrix and the change of fiber mass fraction in the magnet ic field,and conducts research around the magnetization treatment and characterization of carbon fibers,the laws of fiber direction and mass fraction affecting the wave absorption performance,and the design and CST simulation of metamaterial absorbers.The main contents are as follows:(1)The magnetic carbon fiber was prepared by chemical coprecipitation method with iron oxide coating on the surface of carbon fiber.The preparation results were tested and characterized by SEM,EDS,XRD,VSM and other means.The electromagnetic parameters of the magnetic carbon fiber were measured by the coaxial method of vector network analyzer,and its loss factor and reflection loss were calculated.The results show that the prepared magnetic carbon fiber has good structural stability.Compared with conventional carbon fiber,the magnetic carbon fiber has additional magnetic loss capacity and excellent wave absorption performance;When the thickness is 1.5mm,the minimum reflection loss is-40dB,and the effective absorption bandwidth(RL<-10dB)is 5.1GHz;The minimum reflection loss of the material within the range of 1.5mm to 5mm is lower than-20dB,and the effective absorption bandwidth can cover 14.9GHz(3.1 GHz～18.0GHz).(2)Composite materials with magnetic carbon fiber mass fractions of 5wt%,10wt%,15wt%,20wt%,25wt%,and 30wt%were prepared using magnetic carbon fiber as absorbent and photothermal dual curing resin as matrix through 3D printing pre curing and heating post curing.The electromagnetic parameters were tested and the loss factor,impedance matching,attenuation matching,and reflection loss were calculated.The results indicate that low content composite materials are beneficial for impedance matching,while the attenuation ability does not always increase with the increase of magnetic carbon fiber mass fraction.The attenuation ability of the composite material is best when the mass fraction is 15wt%;By adjusting the mass fraction and material thickness of magnetic carbon fibers in composite materials,microwave absorption can be achieved in different frequency ranges.(3)A composite material photocurable 3D printer with continuously adjustable magnetic field direction is used to prepare a composite material with magnetic carbon fiber directional arrangement.The electromagnetic parameters of the composite material are adjusted by adjusting the distribution state of magnetic carbon fibers in the resin matrix,and the absorption performance is improved by adjusting the material thickness.The results show that under different directional arrangement conditions of magnetic carbon fibers,the dielectric constant and magnetic permeability of the material exhibit anisotropy,which is closely related to the different fiber arrangement directions;Taking the directional arrangement composite material with an angle of 30 0 between the fiber axis and the direction of the electromagnetic wave incident electric field as an example,the minimum reflection loss of the composite material is-15.91dB when its thickness is 2mm.(4)Combining the traditional absorbing materials with metamaterial,a metamaterial absorber composed of periodic gradient honeycomb cells is designed by using the design idea of multilayer impedance gradient absorber.Numerical simulation is carried out through CSTMicrowaveStudio to study the laws of metamaterial unit layered material parameters and unit structure parameters affecting the absorbing performance of the absorber,and further explore the absorbing mechanism of metamaterial absorber.The results indicate that the gradient design of equivalent electromagnetic parameters for multi-layer absorbing materials is beneficial for improving the absorbing performance of the absorbing body;The designed metamaterial absorber can achieve broadband absorption in both X-band and Ku band,and is insensitive to the incident angle of electromagnetic waves.