Prearation And Properties Of Ku Band Wave-transparent Marine Environment Composites

With the proposal of the maritime power strategy,the update speed of various new weapons and equipment is accelerating,and the radar antenna system is an indispensable part of maritime military operations.Long-term exposured to high salt fog,radar antenna system will cause huge damage to its accuracy because of high humidity and heat in the marine environment.Therefore,it is of practical significance to design a radome that has excellent wave-transmitting performance,marine corrosion resistance and mechanical properties.1)Taking ultra high molecular weight polyethylene fiber(UHMWPE)as the research object,KH550 functionalized PDA particles are used to modify UHMWPE fiber to improve the problem of poor interface between UHMWPE and resin matrix.The UHMWPE before and after modification was characterized and analyzed by SEM,FT-IR,XPS and TGA.The results show that KH550 functionalized PDA particles have been successfully deposited on the surface of UHMWPE fiber.Compared with UHMWPE,the monofilament tensile strength retention rates of UHMWPE-PDA and UHMWPE-PDA-KH550 are 98.9%and 92.9%,respectively.Three composite materials of UHMWPE/EP,UHMWPE-PDA/EP and UHMWPE-PDA-KH550/EP were prepared,and their dielectric properties were characterized by a vector network analyzer.The results showed that the dielectric performance of UHMWPE-PDA-KH550/EP is the best.The dielectric constant reduces to around 2.3,and the dielectric loss is less than 0.02.The modified UHMWPE-PDA-KH550 has the best salt spray corrosion resistance by the salt spray experiments.The flexural strength,flexural modulus and impact strength of UHMWPE-PDA-KH550/EP are 107.99MPa,9.43GPa and 236.97k J/m~2,which are increased by 29.84%,7.94%and 24.34%compared with UHMWPE/EP,respectively.The optimal transmission thickness of the UHMWPE-PDA-KH550/EP composite system in the Ku-band has been theoretically calculated,and the optimal transmission thickness of the K-QFs/G-EP system is between 6.202 mm and 7.071 mm.The influence of the incident angle of electromagnetic wave on the wave transmission performance of UHMWPE-PDA-KH550/EP composite radome was conducted.The results show that when the incident angle is below than 30°,the whole Ku band can meet the requirement of transmission rate with greater than 75%.When the electromagnetic wave incident angle of the radome is greater than 35°,it only meets the requirements in the high frequency band.Finally,the horn antenna is designed and the influence of the radome on the antenna gain is simulated and analyzed.The antenna gain is reduced by 0.22d B after the radome being installed,which is basically no impact on the antenna gain.2)The influence of the synergistic effect of matrix modification and surface modification of epoxy resin(EP)and quartz fiber(QFs)on the wave transmission,marine corrosion resistance and mechanical properties of composite materials was studied.The influence of G-POSS on the dielectric properties of the resin matrix and composite materials was studied.The results show that G-EP modified by 5wt%G-POSS has the most excellent dielectric properties.The curing behavior and rheological properties were characterized and analyzed,and the best molding process suitable for this system was obtained.The QFs being modified by KH550 was characterized by SEM,FT-IR and water contact angle,and the results indicated that KH550was successfully grafted onto the fiber surface.Three composite materials QFs/EP,QFs/G-EP and K-QFs/G-EP were prepared,and related properties were tested.Compared with the other two composite materials,the performance of K-QFs/G-EP is excellent,with the dielectric constant around 3.2,and the dielectric loss tangent is between 0.005 and 0.02.The initial decomposition temperature is increased to 369.59 ~0C by TG results,as well as the increasing of the residual mass.The water absorption rate of decreases,and the water absorption rate of the interface decreases by the salt spray experiments.Thus,the corrosion resistance of K-QFs/G-EP composite is the best.The bending strength,flexural modulus and the impact strength of K-QFs/G-EP are respectively 373.42MPa,21.73GPa and 458.88k J/m~2,which are 33.13%,14.7%and 22.1%higher than those of QFs/EP.K-QFs/G-EP is selected as the composite material for the design of the radome.Wavelength theory calculates its minimum transmission loss thickness in Ku-band.The results show that the optimal thickness is between 5.774 mm and 5.270 mm.It is designed according to the thickness corresponding to the center frequency of the Ku-band and the transmission at different angles of incidence.The transmission loss and the influence of the cover on the antenna gain were simulated.The results show that as the incident angle increases,the transmission loss gradually increases.When the incident angle is less than 20°,the transmission rate in the entire Ku band is greater than 75%.The antenna gain after adding the cover drops by 0.02d B,which basically does not affect the antenna gain.