Obtenção e caracterização de estruturas absorvedoras de micro-ondas baseadas em laminado de fibra de vidro/resina epóxi/véu de C/Ni
Carregando...
Data
2016-07-29
Autores
Silveira, Daniel Consoli [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Materiais compósitos multifuncionais estão em plenos desenvolvimentos científico e tecnológico, com utilização crescente nos setores espacial, aeronáutico, de telecomunicações e médico. Dentre esses, destacam-se as estruturas absorvedoras de micro-ondas (em inglês – radar absorbing structures – RAS). Essas estruturas multifuncionais combinam características de elevada resistência específica e atenuação de micro-ondas. O objetivo deste trabalho é preparar compósitos laminados de tecido de fibras de vidro/resina epóxi (FV/resina epóxi), adequadamente combinados com véu de fibras de carbono metalizado com níquel (C/Ni), avaliando os seus comportamentos eletromagnéticos na faixa de frequências de 8,2 a 12,4 GHz, por meio de medidas dos parâmetros de espalhamento (Par_S). Os materiais precursores foram avaliados por análises térmicas de calorimetria exploratória diferencial (DSC) e termogravimétricas (TGA), de modo a estabelecer o ciclo de cura apropriado a ser utilizado no processo de moldagem por compressão a quente, análises microscópicas e medidas dos Par_S (Sii - refletividade e Sij - transmissão). Para diminuir o caráter refletor identificado no véu de C/Ni foram realizados ataques em soluções de ácido nítrico em distintos tempos de ataque e concentrações. A remoção da camada de níquel foi monitorada via espectroscopia por energia dispersiva (EDS). Apesar da remoção do Ni do véu de C, o seu caráter refletor, como também dos seus laminados, continuou elevado. Esse comportamento mostra potencial de aplicação desses laminados em blindagem eletromagnética. Buscando adequar as características do véu, com a proposta de se obter RAS, esse foi cuidadosamente perfurado com figuras circulares e quadráticas e, em seguida laminado. A caracterização desses novos laminados obtidos mostra valores de atenuação (Sii) de -22,4 dB (> 99% de absorção) em 12,4 GHz (50 Ω). A conversão deste gráfico para 377 Ω, simulando propagação da onda no espaço livre, apresenta uma banda ressonante em 9,3 GHz de aproximadamente -29 dB (~99,9% de absorção). Este resultado mostra a obtenção de RAS, com característica de superfície seletiva de frequência (FSS), graças à periodicidade das figuras vazadas inseridas no véu de C/Ni.
Multifunctional composite materials are in full scientific and technological development, with increasing application in the space, aeronautical, telecommunications and medical fields. Among these stand out the radar absorbing structures (RAS). These multifunctional structures combine high specific strength properties with microwaves attenuation. The aim of this work is to process glass fiber fabric/epoxy resin (GF/epoxy resin) laminates properly combined with carbon fiber veil metalized with nickel (C/Ni), evaluating their electromagnetic behaviors in the frequency range from 8.2 to 12.4 GHz, by measurements of their scattering parameters (Par_S). The starting materials were evaluated by thermal analysis, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), in order to establish the appropriate cure cycle to be used in the hot compression molding process, the materials were also assessed by microscopy and measurements of Par_S (Sii – reflectivity and Sij transmission). To decrease the reflector behavior identified for the C/Ni veil, its surface was treated in nitric acid solutions, with attacks conducted at several attack times and concentrations. The removal of the nickel layer was monitored and confirmed via energy dispersive spectroscopy (EDS). Even though, the C veil as well as its laminates remained with high reflector behavior. This behavior shows potential for the application of these laminates in electromagnetic shielding. Aiming to adequate the veil characteristics for obtaining RAS, the veil was carefully perforated with circular and square figures, and at sequence laminated. The characterization of the novel laminates shows attenuation values (Sii) of -22.4 dB (> 99% absorption) at 12.4 GHz (50 Ω). The conversion of this chart to 377 Ω, simulating wave propagation in free space, has a resonant band at 9.3 GHz with approximately -29 dB (~ 99.9% absorption). This result shows the obtaining of RAS, with characteristics of frequency selective surface (FSS), due to the periodicity of the inserted void figures in the C/Ni veil.
Multifunctional composite materials are in full scientific and technological development, with increasing application in the space, aeronautical, telecommunications and medical fields. Among these stand out the radar absorbing structures (RAS). These multifunctional structures combine high specific strength properties with microwaves attenuation. The aim of this work is to process glass fiber fabric/epoxy resin (GF/epoxy resin) laminates properly combined with carbon fiber veil metalized with nickel (C/Ni), evaluating their electromagnetic behaviors in the frequency range from 8.2 to 12.4 GHz, by measurements of their scattering parameters (Par_S). The starting materials were evaluated by thermal analysis, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), in order to establish the appropriate cure cycle to be used in the hot compression molding process, the materials were also assessed by microscopy and measurements of Par_S (Sii – reflectivity and Sij transmission). To decrease the reflector behavior identified for the C/Ni veil, its surface was treated in nitric acid solutions, with attacks conducted at several attack times and concentrations. The removal of the nickel layer was monitored and confirmed via energy dispersive spectroscopy (EDS). Even though, the C veil as well as its laminates remained with high reflector behavior. This behavior shows potential for the application of these laminates in electromagnetic shielding. Aiming to adequate the veil characteristics for obtaining RAS, the veil was carefully perforated with circular and square figures, and at sequence laminated. The characterization of the novel laminates shows attenuation values (Sii) of -22.4 dB (> 99% absorption) at 12.4 GHz (50 Ω). The conversion of this chart to 377 Ω, simulating wave propagation in free space, has a resonant band at 9.3 GHz with approximately -29 dB (~ 99.9% absorption). This result shows the obtaining of RAS, with characteristics of frequency selective surface (FSS), due to the periodicity of the inserted void figures in the C/Ni veil.
Descrição
Palavras-chave
Compósitos multifuncionais, Estruturas absorvedoras de micro-ondas, RAS, Compósitos de fibras de vidro/resina epóxi, Véu de C/Ni, Multifunctional composites, Radar absorbing structures, Glass fiber/epoxy resin composites, C/Ni veil