Research On Radar/Infrared Compatible Stealth Performance Of Resin-Based Aluminum/Iron Carbonyl Composite Coatings

The continuous progress of modern detection technology has increased the requirement of multi-spectrum camouflage integration.However,radar stealth materials have a strong absorption effect on electromagnetic waves,while infrared stealth materials have a strong reflection effect on electromagnetic waves.It is a great challenge to achieve the ideal compatibility between the radar stealth and infrared stealth.Traditional composite compatible materials will severe impact the radar stealth performance after the introduction of infrared stealth,making it difficult to satisfy the requirements of practical compatible stealth.Therefore,structural compatible materials are the main development direction of multi-spectrum compatible materials due to their higher designability and electromagnetic adjustment ability.Based on the magnetic loss material carbonyl iron with excellent wave absorption performance in the radar band,and the low emissivity material aluminum with excellent stealth performance in the infrared band,a series of composite coatings and structural composite coatings have been carried out.Firstly,single-layer composite compatible coatings are prepared to study the influence of different shapes and compositions of carbonyl iron/flake aluminum powder fillers on the compatible stealth performance of coatings,and to reveal the electromagnetic response of the materials in radar and infrared wavelengths.Secondly,the flake aluminum powder/polyurethane@iron carbonyl/polyurethane bilayer composite coatings are prepared by spraying method,and the particle size and content of the surface aluminum powder are controlled to regulate the compatibility performance of the bilayer coatings.On this basis,the surface layer is structured using an embossing method to improve the wave absorption performance of the bilayer coatings.Finally,the filtering property of the metasurface is used to achieve a distinct response to radar waves and infrared waves.The metasurface and coatings are combined into metasurface composite structure coatings,and the filtering performance is controlled by changing the period size and pattern arrangement of the metasurface to clarify the influence of the metasurface on the absorption performance of the coatings.SEM,TSS-5X infrared emissivity tester,vector network analyzer,absorbing dark chamber,and four-probe tester are used in the study to test and analyze the performance of samples in terms of microscopic morphology,infrared emissivity,electromagnetic parameters,reflection loss,and electrical conductivity.The main conclusions are as follows.(1)Since the distribution of the filler cannot be regulated by the monolayer coating,the low infrared emissivity characteristics of the flake aluminum powder cannot be effectively utilized.Instead,the impedance matching of the coatings will be influenced by aluminum powder,weaking the magnetic coupling and leading to a drastic decline in radar wave absorption performance.It is difficult to achieve compatibility between radar and infrared stealth with single-layer coating.(2)The double-layer structure design can effectively achieve radar/infrared compatible stealth performance,and the micron-level aluminum powder in the surface layer can effectively filter electromagnetic waves.The prepared flaky aluminum powder/polyurethane-iron carbonyl/polyurethane bilayer coatings initially achieve compatibility between radar and infrared stealth.The absorption curves of the double-layer coatings are shifted to lower frequencies than those of the single-layer coatings because the surface aluminum powder coatings do not have the ability to lose electromagnetic waves and have a high real part of the dielectric constant.The maximum effective absorption bandwidth of the coatings decreases from 7.7 GHz(8.7-16.4 GHz)to 6.5 GHz(7.8-14.3 GHz).However,the structural surface can eliminate this effect by improving the impedance matching of the coating.After embossing the honeycomb structure,the absorption curves of the double-layer coatings are adjusted back to be basically the same as that of the single-layer coatings,and the maximum effective absorption bandwidth is also restored to 7.4 GHz(8.3-15.7 GHz).Thus,the infrared emissivity of the coatings is less than 0.3 while not affecting the absorption of radar waves,achieving excellent radar/infrared compatible stealth performance.(3)Metasurfaces with low-pass filtering characteristics are ideal structures for radarinfrared compatible stealth.Studies have shown that the infrared emissivity of the metasurface decreases with the increase of the conductor patch area ratio.Simultaneously,the metasurface shifts the radar wave absorption peak of the coating substantially to lower frequencies.The effect of the metasurface on the radar absorbing performance can be modulated without changing the infrared emissivity by designing the pattern period and arrangement of the metasurface.The wave absorption performance of the flaky carbonyl iron coatings with high dielectric constant tangential magnetic loss are improved using the peak modulation effect and the enhanced magnetic resonance of the metasurface.After compounding the metasurface,the emissivity of the coatings decreases from 0.733 to 0.281.The maximum effective absorption bandwidth of the flaky carbonyl iron coatings is extended from 0 GHz to 6.6 GHz(3.8-5.2GHz and 12.8-18 GHz),and the maximum reflection loss is improved from-9.5 d B to-40 d B.