Study On Preparation And Property Of Infrared Stealth Composite

With the continuous improvement of the intelligence and accuracy of infrared detectors,the requirements for infrared stealth materials in military warfare are getting higher and higher.At present,most infrared stealth materials realize infrared stealth by reducing the infrared emissivity of the target surface,such as coating low emissivity coatings,and using low emissivity materials to cover camouflage.When the target temperature is close to the ambient temperature,these infrared stealth materials are used to camouflage the target object to have a certain infrared stealth effect,but as the target temperature rises,the temperature of the camouflage material will also increase,and the infrared stealth effect gradually becomes worse.Therefore,when the target temperature is much higher than the ambient temperature,in order to achieve a good infrared stealth effect,the infrared stealth material must not only have low infrared emissivity,but also have a certain heat insulation performance,so the development of a new type of thermal infrared stealth material Become one of the current hot spots.In this project,an infrared stealth composite material with low emissivity and heat insulation function was prepared based on the mechanism of infrared stealth.The low emissivity part is plain weave woven fabric,and the heat insulation part is SiO₂aerogel coating.Firstly,the properties of silver-plated nylon,copper-plated nylon yarn and zinc oxide polyester yarn were tested.After comparative analysis,FDY polyester yarn and silver-plated nylon yarn were selected as warp and weft yarns.Kind of woven fabric and tested its infrared emissivity;then the surface morphology,thermal stability and thermal conductivity of SiO₂aerogel were analyzed,and then KH560 surface modified SiO₂aerogel was selected as the functional filler and E51epoxy resin A thermal insulation coating was prepared for the film-forming agent,and the thermal conductivity and thermal stability of the SiO₂aerogel coating film were tested and analyzed;then the low emissivity woven fabric was used as the upper and lower layers,and the SiO₂ aerogel coating The layer is used as the core layer to prepare a sandwich structure composite material using a hot press molding process,and the mechanical properties and infrared stealth effect of the woven fabric-SiO₂aerogel coating composite material are characterized and analyzed.Finally,in order to strengthen the woven fabric-The mechanical properties of the SiO₂aerogel coating composite material,0.5%multi-walled carbon nanotubes were added as a reinforcement in the aerogel thermal insulation coating to prepare a woven fabric-CNTs/SiO₂aerogel coating composite material,and Its performance is further tested and analyzed.The main conclusions are as follows:(1)Comparing the infrared emissivity of three kinds of yarns,it is found that the emissivity of silver-plated nylon yarn is the smallest 0.654;polyester and silver-plated nylon yarns are selected as warp and weft yarns to prepare a low emissivity woven fabric,in which the weave is plain weave The weave,warp and weft density are set to 110·cm^-1and 30·cm^-1,and the measured emissivity of the fabric is 0.749,which is about 9.5%lower than that of pure polyester fabric.(2)Comparing the thermal conductivity of 3 kinds of SiO₂aerogels with different particle sizes,it is found that the thermal conductivity of 3 kinds of SiO₂aerogel powders are all between0.030?0.031W/(m·K);The TG test results show that the thermal stability of SiO₂aerogel is good,the thermal weight loss at 305?is 1.35%,and the thermal weight loss at 800?is about 18%;compare three different particle size SiO₂aerogel coatings The thermal insulation performance of the layer film found that when the SiO₂aerogel content is 9%,the thermal conductivity of the SiO₂aerogel thermal insulation coating film with particle size of 15,50?m and 100?m is0.07271W/(m·K),respectively,0.07871W/(m·K)and 0.07997W/(m·K),that is,as the particle size increases,the thermal conductivity increases slightly;compare the thermal insulation performance of five coating films with different SiO₂aerogel content It is found that with the increase of the aerogel addition,the thermal conductivity of the SiO₂ aerogel coating film gradually decreases.When the mass fraction of aerogel in the coating is 12%,the thermal conductivity of the coating is the smallest,as low as 0.05835 W/(m·K);Compared with the pure epoxy coating film,after adding 12%aerogel,the initial decomposition temperature of the composite coating film increased from 300.6?to 312.4?,and the maximum thermal decomposition temperature increased from 390.5?When the temperature is increased to400.3?,the maximum thermal decomposition rate is reduced from 23.4%/min to 19.0%/min,and the thermal stability of the coating film is improved.(3)With low emissivity woven fabric as the upper and lower layers,and SiO₂aerogel thermal insulation coating as the middle layer,a sandwich structure composite material was prepared by hot pressing.The temperature is set to 120°C,the hot pressing pressure is 1 MPa,and the hot pressing time is 10 min.In order to explore the influence of thermal conductivity on the infrared stealth performance of woven fabric-SiO₂aerogel coating composites,two sets of comparative experiments were designed.The results show that as the particle size of SiO₂aerogel increases,woven fabric-SiO₂aerogel The infrared stealth performance of the glue-coated composite material gradually deteriorates,and the temperature difference between the infrared radiation temperature between the surface of the composite material and the surrounding environment gradually increases,respectively 3.0?,3.3?and 3.7?;with the SiO₂aerogel in the thermal insulation coating With the increase of the amount of addition,the temperature difference of infrared radiation between the surface of the woven fabric-SiO₂aerogel coating composite material and the surrounding environment will gradually decrease,and the infrared stealth performance will gradually become better.When the woven fabric-SiO₂aerogel coating composite material is used When the aerogel content of the composite material is 12%,the temperature difference of infrared radiation between the surface of the composite material and the surrounding environment is about 2.0?,and the infrared stealth effect is the best.Through two sets of comparative experiments,it is found that the smaller the thermal conductivity of the woven fabric-SiO₂aerogel coating composite material,the greater the heat transfer barrier to the heat source target,and the better the infrared stealth effect of the composite material.(4)In order to explore the relationship between the amount of SiO₂aerogel added and the mechanical properties of the woven fabric-SiO₂aerogel coating composite,the mechanical properties of the composite were tested.The results show that with the increase of the amount of SiO₂aerogel,the tensile strength and flexural strength of the woven fabric-SiO₂aerogel coating composite first increase and then decrease.Compared with the woven fabric-pure epoxy coating composite material,when the SiO₂aerogel is added at 3%,the tensile strength is increased by7%and the bending strength is increased by 9.6%;but with the addition of SiO₂aerogel The amount continues to increase,and the mechanical properties of the woven fabric-SiO₂aerogel coating composite material gradually become worse.When the aerogel addition amount is 12%,the mechanical properties of the composite material are the worst,which is comparable to the woven fabric-pure epoxy coating Compared with composite materials,the tensile strength decreased by 44.2%and the bending strength decreased by 35.1%.(5)Compared with the SiO₂aerogel coating film,after adding 0.5%modified carbon nanotubes to the coating,the thermal conductivity of the CNTs/SiO₂aerogel composite coating film is slightly increased,but the change is not significant.As the amount of SiO₂aerogel increases,the thermal conductivity of the CNTs/SiO₂aerogel composite coating film gradually decreases.When the addition amount of SiO₂aerogel in the CNTs/SiO₂aerogel composite coating is 12%,the thermal conductivity of the CNTs/SiO₂aerogel composite coating film is the smallest,as low as 0.05921W/(m·K).(6)Compared with the woven fabric-SiO₂aerogel coating composite material,after adding0.5%carbon nanotubes,the mechanical properties of the woven fabric-CNTs/SiO₂aerogel coating composite material have been improved to a certain extent.When the aerogel content is12%and the addition of carbon nanotubes is 0.5%,the tensile strength of the woven fabric-CNTs/SiO₂aerogel coating composite material is 20.48MPa and the bending strength is82.18MPa,respectively.The fabric-SiO₂aerogel coating composite material has increased by9.8%and 8%;the infrared stealth performance of the two composite materials is relatively close.When the addition amount of SiO₂aerogel is 12%,the woven fabric-CNTs/SiO₂aerogel is used The glue-coated composite material camouflages the heat source target.The temperature difference between the surface of the composite material and the ambient infrared radiation is about 2.1?,which is 0.1?different from that of the woven fabric-SiO₂aerogel coating composite material,which has a good infrared stealth effect.