Bionic Design And Performance Research Of Broadband Absorbing Composite

With the vigorous development of radio communication technology,the demand for electromagnetic wave absorbing materials in the fields of stealth technology,electromagnetic compatibility and improving equipment efficiency is increasing.In order to meet the application ability in harsh environments,the performance requirements of multi-band broadband absorption and high mechanical load bearing become the core issues that need to be solved urgently.Based on this,this research takes bionics as a breakthrough,extracts the perfect antireflection structure model that nature helps biology evolve,and applies it to the absorbing composite with certain electromagnetic properties and good mechanical properties,carries out the size optimization,reflectivity simulation and test of bionic structure at the sub-wavelength scale,and explores the absorbing mechanism of bionic structure to achieve broadband absorption.The specific research results are as follows:Firstly,based on the intrinsic microwave absorbing composites of carbon black/basalt fiber/epoxy and carbon black/epoxy,this study established the optimal material system with different carbon black content to meet the impedance matching and absorption characteristics of the microwave absorbing composites through coaxial electromagnetic parameter testing and theoretical calculation of the plate absorbing performance.Through tensile and three-point flexural tests,it was found that the average tensile strength(210.83 MPa)and flexural strength(512.99 MPa)of the microwave absorbing composite material using carbon black/basalt fiber/epoxy as the material system were 69.8% and 316.1% higher than those of the carbon black/epoxy with brittle fracture characteristics,respectively.When used as the surface skin of the microwave absorbing composite,it has the overall ability to enhance the material’s ability to withstand mechanical loads.In order to solve the narrow band absorption characteristics of traditional single layer microwave absorbing composite,the hexagonal convex array surface structure evolved from the moth compound eye was optimized and designed at sub wavelength scale.Using carbon black/basalt fiber/epoxy microwave absorbing composite,a sample of moth like compound eye fiber reinforced single layer microwave absorbing composite was fabricated using hot pressing molding and mechanical processing technology.Its sample reflectivity has an effective absorption of less than-10 d B in the range of 6-18 GHz,and achieves more than 85% oblique incidence absorption of electromagnetic waves within an incidence angle of 0°-40°.Through electromagnetic energy simulation analysis,it was concluded that the structural design of the hexagonal boss effectively enhances the impedance matching characteristics of the material within the resonant frequency band.The strong edge scattering between the structural surfaces increases the transmission path of electromagnetic waves within the material,causing electromagnetic energy to be absorbed and lost within the electrical loss material.In order to further improve the multi-band broadband absorption performance,based on the principle of multi-layer impedance matching,using the electromagnetic parameters of the intrinsic wave absorbing composite,a double-layer impedance matching composite with uniform and complete interlayer microstructure and fewer defects was designed and fabricated.Using the quasi grid structure and quasi honeycomb structure of the butterfly wing scales for reference,a bionic structural design was carried out to produce a sample of a coupled bionic double-layer wave absorbing composite,Its sample reflectivity has an effective absorption of less than-10 d B in the 2.8-40.0 GHz multi band range,and achieves more than 85% oblique incidence wide-angle absorption of electromagnetic waves at 0°-60°.Through electromagnetic energy simulation analysis,it is concluded that the ridges and ribs of the matching layer quasi grid structure have full frequency impedance tuning effects,and the absorbing layer quasi honeycomb structure has mid and low frequency interlayer impedance tuning and enhanced interface reflection effects.In addition,the bionic structure of the matching layer of the coupled bionic double layer microwave absorbing composite can withstand large flexural loads.The maximum flexural strength generated by its rib structure is 561.8 MPa,which is 14.9% higher than that of the carbon black/basalt fiber/epoxy plate,and significantly higher than that of the carbon black/epoxy resin plate where brittle fracture occurs.The bionic structure used in this study has a significant mapping relationship with broadband wave absorption performance,while inheriting material properties and excellent mechanical properties of the structure,providing a new reference scheme for the development of new broadband wave absorption composite in the future.