Study On Infrared/Radar Compatible Stealth Coatings Of Heterocyclic Poly (Ether Nitrile Ketone)

The continuous development of modern detection technology has made our weapons and combat personnel face serious threats.Hence,it is of great practical significance to improve infrared stealth technology as a means of anti-detection.The multispectral property of the detection system determines that the infrared stealth material must meet certain requirements of multispectral stealth compatibility.In addition,the material also needs to have good heat resistance to withstand harsh operating conditions.Resin/metal composite coating occupies an important position in the field of infrared stealth because of the advantages of its simple process,low cost,and low emissivity,but in view of the long-term use environment of temperature higher than 300 ℃,most of the resin is difficult to meet the application conditions,and the high filling rate of metal also affects the compatibility of resin/metal composite coating with radar stealth.According to the above problems,in this paper,a infrared stealth coating with high temperature resistant and low infrared emissivity was prepared by using poly(aryl ether nitrile ketone)(PPENK)resin.On this basis,the periodic element structure was introduced into the surface of the coating by pattern design and size adjustment,and a two-layer ir/radar compatible stealth coating with a honeycomb surface structure has been developed.The main research contents of this paper are as follows:(1)PPENK/Al composite coating was prepared by using PPENK as matrix resin and flake aluminum powder as low emissivity filler.Firstly,the influences of different technological conditions on the preparation and emissivity of the coating were explored,and the relationship between the emissivity and the amount of aluminum powder was investigated.The results showed that the emissivity of the composite coating showed a “v”-shaped trend with the increase of aluminum powder content.When the mass ratio of PPENK to aluminum powder is1:0.4,the emissivity of the composite coating is 0.14 at 8～14 μm.At this point,the coating had grade 0 adhesion and could withstand a drop hammer impact of 50 cm.In addition,the heat resistance of the composite coating was systematically investigated.After heating at 400℃ for1 h,the emissivity of the composite coating was 0.20,the adhesion grade was 0,and the composite coating could withstand the drop hammer impact of 50 cm.The coating has excellent heat resistance.Based on the results of various characterization tests,it was found that the change of the surface morphology and the deepening of the oxidation degree of aluminum powder were the reasons for the change of the emissivity of the coating after heating at higher temperature.Finally,the thermal imaging test proved that PPENK/Al composite coating had excellent infrared stealth effect and could still maintain good performance at 400℃.(2)Radar absorbing coating(RAL)was prepared by using carbonyl iron as absorbing agent.Through theoretical calculation and experimental comparison,the optimum thickness of RAL and the optimum ratio of resin to absorbing agent were determined as 1.5 mm and 1:2.5,respectively.The PPENK/Al infrared reflector(IRSL)with honeycomb periodic structure was fabricated by template method.On the one hand,IRSL with a high metal filling rate ensured that the material had a low emissivity;on the other hand,the gap between the adjacent hexagons of IRSL reserved a wider channel for electromagnetic waves to pass through.At the same time,the electromagnetic wave was reflected between the infrared layer and the substrate for many times,which prolongs the loss path.This successfully broadened the effective absorption bandwidth(EAB)of the material and achieves the cooperative optimization effect of infrared layer and radar layer.In addition,HFSS software was used to verify the above analysis.Performance test results show that the lowest emissivity value of the double-layer coating with honeycomb surface structure was 0.32,and its EAB was 6.8 GHz(10.5～17.3 GHz).The coating shows excellent infrared/radar compatible stealth performance.