Research On The Mechanical And Electromagnetic Properties Of Broadband Absorbing Composite Structure

Absorbing materials are special materials capable of converting electromagnetic energy into heat or other forms of energy.These materials have significant application value in fields such as electromagnetic compatibility,microwave protection and radar stealth.Particularly,components that integrate structural load-bearing capacity and broadband absorption characteristics have been widely used in advanced weapon systems,such as stealth aircraft and ships.Despite their potential,absorbing structures still face many challenges,including absorption bandwidth,mechanical properties,fabrication processes and environmental adaptability.The development of absorbing structures with superior performance can effectively enhance the stealth performance of advanced weapon systems,improve their battlefield survivability,and increase mission success rates.This paper focuses on the design,fabrication and performance characterization of composite absorbing structures with both excellent mechanical load-bearing capacity and broadband absorption properties.To develop a lightweight composite structure with high strength and high transmission efficiency,a curved wall honeycomb based on quartz fiber reinforced composite was designed and fabricated.The out-of-plane compressive,out-of-plane shear and transmission properties of the structure were investigated through analytical predictions,numerical simulations and experimental measurements.Among them,the analytical models of the out-of-plane compressive and out-of-plane shear properties of the curved wall honeycomb were established using classical elasticity theory and the failure mechanism maps were established to predict the main failure modes.The results show that the mechanical properties of the curved wall honeycomb can be effectively improved through rational configuration design.Compressive buckling and compressive crushing can be observed when the structure was subjected to out-of-plane compressive loads.Shear buckling,fiber shear failure and face-core debonding can be observed when the structure was subjected to out-of-plane shear loads.Additionally,the structure exhibits extremely high microwave transmittance.The anisotropic effective permittivity is attributed to its unique structural configuration.However,the preparation process for the quartz fiber curved wall honeycomb structure is relatively complex.Therefore,an absorbing composite hierarchical grid structure with both excellent broadband absorption and mechanical properties was designed and fabricated through molding and interlocking technology.The out-of-plane compression performance,electromagnetic wave absorption performance and radar cross section performance of the structure were studied.The hierarchical phase not only improved the buckling resistance of the structure,but also enhanced the electromagnetic coupling response between periodic resistive sheets,which benefited to both mechanical properties and absorption performance.The structure exhibited maximum strength of 28.8 MPa with a density of 0.231 g/cm~3.The structure showed excellent electromagnetic wave absorption performance with a-10 d B absorption bandwidth of 34.8 GHz and an average reflectivity of-17.4 d B within the absorption bandwidth.Moreover,the structure showed good absorption performance for oblique incidence electromagnetic waves.Compared to metal plates,the structure significantly improved the stealth performance by effectively suppressing the specular scattering.Based on the Debye model,a theoretical model for calculating the absorption performance of the absorbing composite hierarchical grid structure was established,which greatly improves the efficiency of optimizing the absorption performance.Therefore,a collaborative design approach combining the genetic algorithm and numerical simulation was carried out to optimize the mechanical properties and the absorption performance of the composite structure.The proposed ultra-broadband absorbing composite structure shows a compression strength of 24.2 MPa and a-10 d B absorption frequency range from 2.1 GHz to120 GHz(S,C,X,Ku,Ka,Q,U,M,E bands)with bandwidth of 117.9 GHz.Based on this,a stealthy breathable grid structure was designed in combination with frequency-selective surfaces.Compared to traditional grid structures,the proposed stealthy grid effectively suppresses specular scattering and edge diffraction,which achieves excellent stealth performance at broad azimuths.In order to further enhance the load-bearing capacity and the reliability in harsh environments,a novel curved-walls composite honeycomb structure composed of quartz fiber reinforced composite and chopped carbon fiber/glass fiber composite felt was designed and fabricated through molding and interlocking technology.The out-of-plane compression performance and electromagnetic wave absorption performance of the structure were studied,as well as the impact of environmental load on its performance.The curved-walls configuration not only enhances the coupling between CCF/GFCs,but also restrains buckling and significantly improvs the load-bearing capacity of the structure at low density.Elastic buckling and compressive crushing can be observed when the structure was subjected to out-of-plane compressive loads.The structure exhibited excellent electromagnetic wave absorption performance with a-10 d B absorption bandwidth of 38 GHz(2-40 GHz,covering S,C,X,Ku,K,and Ka bands)and an average reflectivity of-16.5 d B(98%absorption rate).Moreover,the absorption performance of the structure exhibited excellent angular stability.Meanwhile,the absorption performance of the structure remains stable in harsh environments,demonstrating its strong environmental adaptability and ability to be used for long periods of time in such conditions.