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Carbon Fibers Loaded Composites for Microwave Absorbing Application: Effect of Fiber Length and Dispersion Process on Dielectric Properties

Abstract : In this work, a new composite for microwave absorption applications, especially for anechoic chambers, is studied. We propose to substitute carbon black loaded polyurethane foam, currently used in commercial absorbers, by epoxy foam filled with carbon fibers. The purpose of the present paper is to study the influence of three dispersion methods (spatula, shear mixer and ultrasound probe) and four fiber lengths (1 mm, 3 mm, 6 mm and 12 mm) on the homogeneity and dielectric properties (permittivity epsilon ' and dielectric losses tan delta) of achieved composites. Long fibers dispersed with spatula have shown higher dielectric properties than short fibers. However, such a soft dispersion method was revealed to be inefficient to disperse properly the long fibers. Although a homogenous dispersion was obtained with the shear mixer (mechanical dispersion), we noticed an important degradation of the fibers which lead to a decrease of the dielectric properties. Dispersion with ultrasounds appears to be a good compromise between homogeneity and dielectric properties of composites. Finally, electromagnetic simulation predicted a high absorption performance for pyramidal absorber made with the 12 mm-carbon fibers loaded composite with reflection loss lower than - 50 dB for frequencies ranging between 8 GHz and 18 GHz.
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https://hal-univ-rennes1.archives-ouvertes.fr/hal-02530972
Contributor : Laurent Jonchère <>
Submitted on : Friday, April 3, 2020 - 12:27:01 PM
Last modification on : Wednesday, April 8, 2020 - 4:09:55 PM

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R. Benzerga, M. Badard, C. Mejean, A. El Assal, C. Le Paven, et al.. Carbon Fibers Loaded Composites for Microwave Absorbing Application: Effect of Fiber Length and Dispersion Process on Dielectric Properties. Journal of Electronic Materials, Institute of Electrical and Electronics Engineers, 2020, ⟨10.1007/s11664-020-07998-y⟩. ⟨hal-02530972⟩

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