1,720,980 research outputs found
Mimic materials electromagnetic reflection and transmission coefficient
No full textThe paper is focused on a design method to build layered materials able to mimic the reflection and transmission coefficient profile of really existing or even invented dielectric materials. The design method is based on particle swarm optimization algorithm and electromagnetic matrix formalism which allows the minimization of an objective function. Goal of the procedure is to obtain a layered materials mimicking the target reflection and transmission coefficient profile a priori established. The design algorithm is coded in Matlab and it selects the best material for each layer by accessing to a database of dielectrically characterized materials. Materials in the database are made using different species and amount of carbon nanomaterials dispersed epoxy matrix. Thickness and the number of layers of final layered structures are optimized by the iterative design procedure. In the paper some interesting example of mimic optimization are shown. The numerical finite element method analysis complete the electromagnetic discussion showing how each layer of the optimized layered structures takes part in the final goal of mimicking the target electromagnetic profile
RADAR ABSORBING MATERIALS FOR CUBE STEALTH SATELLITE
No full textABSTRACT
Cube Stealth Satellite is proposed for potential applications in defense system. Particularly face of satellite exposed to the Earth are made of nanostructured materials able to absorb radar surveillance electromagnetic wave, conferring stealth capability to the cube satellite. Microwave absorbing and shielding materials tiles are proposed using composite materials consisting in epoxy-resin and carbon nanotubes filler. In the paper, electric permittivity, of composite nanostructured materials are shown. Such data are used by the modeling algorithm to design the microwave absorbing and shielding face of cube satellite. The electromagnetic modeling takes into account for several incidence angles (0-80°), extended frequency band (2-18 GHz), and for the minimization of electromagnetic reflection coefficient. The evolutionary algorithm used for microwave layered microwave absorber modeling is recent Winning Particle Optimization. Mathematical model of absorbing structure is finally experimentally validated by comparing electromagnetic simulation and measurement of the manufactured radar absorber tile. Nanostructured composite materials manufacturing process and electromagnetic reflection measurements methods are described. At the and the finite element method analysis of the electromagnetic scattering by cube stealth satellite is performed
Synthesis and electromagnetic characterization of frequency selective radar absorbing materials using carbon nanopowders
No full textA new method for the synthesis of multilayered radar absorbing materials is analyzed by using carbon nanomaterials. With respect to the literature, a desired profile of reflection coefficient is a priori established as a function of the frequency. The goal of the synthesis is to follow this target profile by computing thickness and type of the material of each layer until the reflection coefficient of the electromagnetic-wave absorber best approximates the wanted reflection coefficient. The material available for each layer is epoxy-resin reinforced by different kind of carbon-based nano/micro powders: graphene nanoplatelets, carbon nanofibers, multi-walled carbon nanotubes and polyaniline. The dielectric characterization of the composite materials is performed in the frequency range 2÷18 GHz. The synthesis uses evolutionary computation by drawing on the electric permittivity of composite materials. Three square layered electromagnetic wave absorbers of 25 cm side are manufactured. The comparison between the target, the simulated and the measured reflection coefficients shows a good agreement thus confirming the scientific validity of the dielectric characterization and the proposed design method. Finally, a finite element analysis has been carried out to explain the mechanism of electromagnetic wave absorption by a multilayer and to simulate a low radar observable naval military gun
Low-cost low-observable satellites made of carbon nanostructured multilayers: Numerical investigation of scattering
No full textCube Stealth Satellite is proposed for potential applications in defense system. Particularly face of satellite exposed to the Earth are made of nanostructured materials able to absorb radar surveillance electromagnetic wave, conferring stealth capability to the cube satellite. Microwave absorbing and shielding materials tiles are proposed using composite materials consisting in epoxy-resin and carbon nanotubes filler. In the paper, electric permittivity, of composite nanostructured materials are shown. Such data are used by the modeling algorithm to design the microwave absorbing and shielding face of cube satellite. The electromagnetic modeling takes into account for several incidence angles (0-80°), extended frequency band (2-18 GHz), and for the minimization of electromagnetic reflection coefficient. The evolutionary algorithm used for microwave layered microwave absorber modeling is recent Winning Particle Optimization. Mathematical model of absorbing structure is finally experimentally validated by comparing electromagnetic simulation and measurement of the manufactured radar absorber tile. Nanostructured composite materials manufacturing process and electromagnetic reflection measurements methods are described. At the and the finite element method analysis of the electromagnetic scattering by cube stealth satellite is performed
Electromagnetic wave absorber composite structures for low observable unmanned air vehicle
No full textThe present research is focused on multi-layered radar absorbing structures useful in low observable unmanned aircraft systems in the frequency range 2-18 GHz. A significant enhancement of the electromagnetic absorption is obtained through the use of different kind of carbon nanomaterials uniformly dispersed within epoxy matrix and fiberglass
Matter's Electromagnetic Signature Reproduction by Graded-Dielectric Multilayer Assembly
No full textA lot of effort has been devoted in the last decades by technology research to realizing materials with a priori defined electromagnetic (EM) properties. One of the challenges at present is to configure the reflection coefficient (RC) of a structure so that any shape of a fixed microwave response is followed. A method for realizing microwave absorbers made by carbon nanocomposite layers assembly able to mimic a given reflection profile is described and experimentally validated. The multilayer design (layer sequence, material, and thickness) is pursued by means of a customized numerical optimization algorithm, which allows to get the required microwave behavior. The novelty of the research is the possibility of tuning the EM field propagation through the combination of different materials in a specific layered compound, in order to imitate the response of any “real” object (i.e., with known EM properties). For the experimental validation of the process, three multilayered structures were designed and manufactured, and their microwave RC was measured in the frequency range of 2–18 GHz. The comparison with the related targets (an ideal frequency selective pattern and the defined profiles of dry soil and salt water as retrieved from literature survey) highlights the effective simulating capability of the realized structures. The preliminary results suggest to exploit the graded-dielectric properties provided by carbon-based nanocomposites for EM mimicking purposes: this would be an ideal approach to tackle still unsolved issues in EM compatibility, remote sensing, communication, and safety fields, as well as for low-cost and time-saving metrology applications
HIGH ENERGY IMPACT TESTING OF NANO-REINFORCED LAYERED COMPOSITE MATERIALS
No full textAn advanced electromagnetic accelerator, called
railgun, has been assembled and tuned in order to
perform high energy impact test on layered structures.
Different types of layered composite materials have
been manufactured and characterized in terms of energy
absorbing capability upon impact of metallic bullets
fired at high velocity. The composite materials under
testing are manufactured by integrating several layers of
Kevlar fabric and carbon fiber ply within a polymeric
matrix reinforced by carbon nanotubes at 1% of weight
percentage. The experimental results show that the
railgun-device is a good candidate to perform impact
testing of materials in the space debris energy range, and
that carbon nanotubes may enhance, when suitably
coupled to the composite’s matrix, the excellent
antiballistic properties of the Kevlar fabrics
Microwave behavior of nanostructured composite for low observable nanosatellites
No full textMicrowave absorbing and shielding material tiles are proposed for improving the stealthness capability of nanosatellites, by using composite materials consisting in polymeric matrix filled by carbon nanotubes. The electric permittivity of the composite nanostructured materials is measured and discussed, and the data allow the modeling algorithm to design the microwave absorbing and shielding faces of the cube satellite. The electromagnetic modeling takes into account for several incidence angles (0–80°), extended frequency band (2–18 GHz), and minimization of the electromagnetic reflection coefficient. The proposed structure is experimentally validated by comparing the electromagnetic simulation to the measurement of the manufactured radar absorber tile. Finally, a finite element method analysis of the electromagnetic scattering by cube stealth satellite is performed
Carbon micro- and nano-structured multilayer composites for microwave metrological design
No full textAim of the research is the development of a procedure for the production of items with electromagnetic properties addressing any a priori defined behavior. The microwave range 2-18 GHz is analyzed, and a series of both physically real and unreal reflection coefficient profiles are proposed are target to be followed. The proposed structures are multilayers made of polymeric material enriched by carbon-based micro- and nano-powder at different weight percentages. A mathematical modelling which lays down the interaction between electromagnetic field and multilayer structure drives the optimization design by a customized numerical tool based on the particle swarm algorithm framework; this latter gives optimal solutions in terms of layering sequence (i.e., indicating composition and thickness of each layer) to replicate the specific target properties. Both numerical simulations and experimental validations testify the mimic capability provided by the designed/manufactured structures. The proposed strategy thus opens a broad spectrum of novel applications for metrological purposes, as well as for electromagnetic compatibility issues
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