This work deals with the dielectric properties of carbon-based nanostructured polymeric composite materials. A commercial epoxy matrix is currently filled with multi-walled carbon nanotubes in different percentages, and final composite material characterized in terms of microwave behavior by means of the waveguide method. By following the guidelines of previous studies, the attention is focused on the changes induced by hard environmental conditions (high temperature in ultra-high vacuum system) on the above mentioned properties. The results obtained in this preliminary research have outlined the intriguing properties of carbon nanostructures, establishing themselves as very promising materials for the future aerospace composite technology.

In this paper, we propose a multilayer nanostructured composite for broadband shielding applications. Layers disposal, electrical parameters, and thicknesses are optimized through a winning particle optimization algorithm to achieve the minimization of the transmitted waves. The structures are simulated by including the forward/backward scattering matrix formalism in the optimization code. The adopted algorithm is the recently introduced winning particle optimization. Manufacturing of the composites is grounded on the optimization procedure. Thanks to the macroscopic absorption features of such nanostructured layers, very thin and lightweight composites can be produced. Several weight percentages of multiwall carbon nanotubes are considered in composite base material manufacturing, also including 6wt% and 15wt% in order to enhance the electromagnetic shielding performance. Prototypes are tested in the microwave region, showing the reliability of the optimization procedure.

This book chapter is based on the experimental activities conducted mainly at Sapienza University of Rome: Astronautic, Electric and Energetic Engineering Department in collaboration with University of Maryland, Institute for Research in Electronics and Applied Physics (IREAP). A branch of scientific research about composite materials is focused on electromagnetic characterization and subsequent application of electric conductive polymers. The use of such structures is relevant in aerospace/aeronautics, for electromagnetic (EM) protection from natural phenomena (lightning), and intentional interference with radar absorbing materials (RAM), in nuclear physics for shields adopted in particle accelerators, and for nuclear EM pulses (NEMP) protection, in electromagnetic compatibility (EMC) for equipment-level shielding, high-intensity radiated fields (HIRF) protection, anechoic chambers (for the realizations of wedges and pyramidal arrays), and human exposure mitigation. In this chapter, composite reinforced by carbon nanostructured materials are considered, mainly because of their interesting electromagnetic characteristics, such as high electrical conductivity and excellent microwave absorption. Composite materials as well their absorption capability are analyzed and numerical design of wide frequency band microwave absorbing structures is presented and discussed in details. It is crucial to highlight the need of interdisciplinary research fields to go through nanomaterials: besides nanotechnology, also electromagnetic wave propagation theory, composite materials manufacturing techniques, evolutionary computation algorithms, and use those to design the “quasi perfect absorber” are strongly required. In particular, we propose an inhomogeneous multilayer absorber made of micrometric graphite (at different wt%), and nanometric carbon particles (SWCNTs, MWCNTs, CNFs, at different wt%). At the end, an improvement of the traditional absorbers has been achieved upon optimization through an in-house winning particle optimization (WPO) algorithm, this last appositely conceived for absorbers optimization. Main goal of the presented work is to optimize the absorbers

Microwave shielding and absorbing structures are proposed using composite materials consisting in epoxy-resin and carbon nanopowders fillers up to 10% weight concentration. Characterization in terms of dielectric parameters is performed and discussed and such data are used to optimize the modeling of multilayer electromagnetic absorber by means of in-house built Winning particle optimization algorithm. Experimental validation of mathematical simulations is then performed.

In this paper, we present the design of nanostructured multilayer absorbers, carried out with the aid of a genetic algorithm (GA). Waveguide measurements are performed to recover the dielectric properties of micrographite single-walled carbon nanotube, micrographite walled carbon nanotube, carbon nanofiber, and fullerene-based composite materials. Conductive fillers are uniformly dispersed in an epoxy resin at different weight percentages (1, 3, 5 wt.%). The electromagnetic (EM) analysis is performed embedding the forward/backward propagation matrix formalism in an in-house GA, thus able to carry out optimization upon oblique incidence over a finite angular range. Developed code minimizes both the reflection and the transmission coefficients under the thickness minimization constraint. Comparison between micrographite and nanopowders absorbers is presented and discussed, when a broadband quasi-perfect absorber is achieved among the $X$ -band combining the two filler families, i.e., exhibiting a loss factor greater than 90% in most of the band, for a thickness of about 1 cm. It is demonstrated that the nanofillers with higher aspect ratio mainly contribute to the EM absorption. Findings are of interest in both radar-absorbing material and shielding structures.

In this paper the authors present their activity in the field of electromagnetic machine applications for aerospace solutions. A three stage electromagnetic accelerator is under construction to perform ballistic characterization of carbon-based nanocomposite materials for anti-debris application. Preliminary experiments as well as numerical simulation have been performed with promising results in terms of bullet's energy. Further implementation are needed in order to come closer the velocity of typical space debris (8km/s).

This work deals with the design of electromagnetic absorber of interest in radar absorbing material (RAM) and microwave shielding systems. This absorber is based on a multilayer structure and the parameters taken into account are: number of layers, absorption maximization, microwave angle of incidence and frequency band. Design and optimization of the absorber are carried out using a Genetic Algorithm (GA) and are based on actual electrical parameters values. Such stochastic method leads to the best trade off between absorption properties and structure thickness, minimizing both the reflection coefficient (RC) and the global multilayer thickness (Thick). All the (carbon based) dielectric materials adopted in GA have been characterized as a function of frequency beforehand and their characteristic impedances inserted in a data base (DB) to be available during design stage. In particular, employed materials consist of epoxy resin reinforced with three different carbon species: micro sized granular graphite, single walled carbon nanotubes (SWCNT) and carbon nanofibers (CNF). The morphology of the multilayer structures is fixed a priori, -- i.e., composite material type and its location in the multilayer structure is given -- and the stochastic optimization procedure can only decide the best thickness of each layer. Main goals have been achieved and the possibility of realizing a quasi-perfect microwave absorber through graphite and nanomaterials has been demonstrated.