طراحي، بهينه‌سازي و ساخت يك نانوكامپوزيت چندلايه جاذب امواج رادار در محدوده فركانسي X

The purpose of this research is to design, optimize and manufacture a multilayer nanocomposite to absorb radar waves in the X frequency range (8-12 GHz). The design of the radar absorber structure depends on a wide range of parameters and has complexities and requires optimization. In this treatise, these parameters are categorized into the following and have been studied experimentally: 1) Reinforcing materials: including the preparation, synthesis and experimental study of various types of wave absorbing particles and the creation of a data library of electrical permitivity and magnetic permeability properties of glass fibers, carbon fiber, parabeam 3D fiber and different types of fillers like carbon black, carbonyl iron, polyaniline and polyaniline-carbonyl iron (PANI+CI) core-shell structure. 2) Geometrical parameters, including the thickness and arrangement of absorbent structure layers. 3) Suitable process for producing designed layering including hand lay-up with and without vacuum bag. Extensive researches show that the effect of all these parameters has not been investigated and optimized simultaneously on the absorption characteristics in X band frequency. For this purpose, a specific and comprehensive algorithm has been designed, which takes into account all the effective parameters, in order to design with the maximum average reflection loss in the entire bandwidth, minimum weight and structural limitations. In fact, an integrated electromagnetic wave absorption calculation model for multilayer structure is coupled with a new multi-objective optimization algorithm based on the Non-dominated Sorting Genetic Algorithm II method in Matlab numerical calculation software. Finally, the proposed algorithm is eva‎luated and validated by using the magnetic data library of the absorbent particles, by producing samples and electromagnetic waveguide tests in the X frequency range. In the following, due to the importance of structural mechanical properties, the effect of adding absorbent particles inside the structure has been investigated by producing samples and conducting mechanical tests in the optimized structure by the proposed model. In this study, using a comprehensive design algorithm, a three-layer composite structure reinforced with glass fibers andthe total thickness of 3 mm is proposed, each layer reinforced by absorbent particles including polyaniline, carbonyl iron and nanostructure (PANI+CI). Due to the simultaneous use of dielectric and magnetic absorbent particles, this structure shows a suitable impedance matching with the environment and absorbs up to 80% of X-band electromagnetic waves. The maximum reflection loss in this structure is reported as -14dB. The experimental results showed that the tensile modulus and strength decrease by 21.5% and 20.6%, respectively, and the bending modulus and strength decrease by 21.7% and 19.7% respectively, which is due to the high volume of absorbent particles added inside the structure. Of course, due to the significant reduction in weight due to the use of absorbent particles inside the structure instead of covering the entire structure, this loss can be compensated by applying a 25% reliability factor in the mechanical design.

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