The Research Of High-temperature Resistant Absorbing Structure With Flexibility

Intelligent high-speed aircraft can change their shape flexibly according to different combat missions,and their surface temperature increase rapidly with the rapid rise of flight altitude and speed.Thus,the absorbing must have excellent flexibility and high-temperature resistance at the same time,which is loaded on the surface.Metamaterial absorbing structure plays an important role in radar stealth technology because it has the advantages of high efficiency,flexibility,easy design,and convenient application.At the present stage,the absorbing often has a single function and fails to combine the flexibility and high-temperature resistance,so it is difficult to apply to the stealth needs of intelligent high-speed aircraft at the present stage.In this paper,the high-temperature flexible absorbing structure is taken as the research object.The main research methods are simulation optimization,formula adjustment,performance testing,preparation process improvement and so on.The main purpose is to summarize the rule and reason of properties change of the structural absorbing materials in high temperature environment,and to solve the problem that the structural absorbing materials cannot be flexible,light weight,broadband and high-temperature resistant at the same time.The specific research contents and results are as follows:1.To solve the problem of narrow absorbing band about flexible absorbing materials,a periodic broadband radar absorbing material is optimized with the help of simulation software.The absorbing material uses graphene impedance film as electromagnetic control functional layer with thickness less than 3 mm and radar absorption rate of more than 90%between 7.92 and 18.66 GHz.The absorbing performance of this material under bending state was also calculated.For the problem that the absorbing property cannot be dynamically adjusted after the structure of absorbing material is fixed,Al₂O₃ bias layer and applied bias are introduced to adjust the conductivity of graphene.Finally,the dynamic regulation of absorbing performance in GHz-band is realized.2.The mechanical properties,electrical properties,and temperature resistance of flexible substrates which commonly used in industrial and experimental design were compared,and the substrates needed for preparing high-temperature flexible absorbing were screened out.The influence of the substrate electromagnetic parameters on absorbing properties of absorbing material under high temperature environment was analyzed.Under high temperature environment,the equivalent impedance of the absorbing material changes with the change of the electromagnetic parameters of substrate,which results in the change of the matching degree between the absorbing material and the free space.However,due to the small variation range of the electromagnetic parameters,the influence on the absorbing performance is also small.3.To solve the problem of poor flexibility of traditional graphene conductive pastes,the FKM-246 mixture was added to make the graphene conductive paste have both flexibility and temperature resistance.Then,the change rule of electrical properties of conductive paste with temperature is studied,and the method to keep the electrical properties stable at high temperature is proposed.Finally,the conductive paste with optimized electrical properties was combined with the flexible substrate to prepare the high-temperature resistant flexible absorbing material with thickness less than 4 mm.