Citation: Vong, C.; Chevalier, A.;
Maalouf, A.; Ville, J.; Rosnarho, J.-F.;
Laur, V. Manufacturing of a Magnetic
Composite Flexible Filament and
Optimization of a 3D Printed
Wideband Electromagnetic
Multilayer Absorber in X-Ku
Frequency Bands. Materials 2022, 15,
3320. https://doi.org/10.3390/
ma15093320
Academic Editors: Amir Mostafaei
and Ludwig Cardon
Received: 14 March 2022
Accepted: 22 April 2022
Published: 5 May 2022
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Article
Manufacturing of a Magnetic Composite Flexible Filament and
Optimization of a 3D Printed Wideband Electromagnetic
Multilayer Absorber in X-Ku Frequency Bands
Christophe Vong
1,2,3
, Alexis Chevalier
1
, Azar Maalouf
1,
* , Julien Ville
2
, Jean-François Rosnarho
3
and Vincent Laur
1
1
University Brest, Lab-STICC, UMR 6285, CNRS, 29200 Brest, France;
christophe.vong@etudiant.univ-brest.fr (C.V.); alexis.chevalier@univ-brest.fr (A.C.);
vincent.laur@univ-brest.fr (V.L.)
2
University Brest, IRDL, UMR 6027, CNRS, 29200 Brest, France; julien.ville@univ-brest.fr
3
SIEPEL Cegelec Defense, 56470 La Trinité-sur-Mer, France; jf.rosnarho@siepel.com
* Correspondence: azar.maalouf@univ-brest.fr
Abstract:
With the multiplication of electronic devices in our daily life, there is a need for tailored
wideband electromagnetic (EM) absorbers that could be conformed on any type of surface-like
antennas for interference attenuation or military vehicles for stealth applications. In this study, a
wideband flexible flat electromagnetic absorber compatible with additive manufacturing has been
studied in the X-Ku frequency bands. A multilayer structure has been optimized using a genetic
algorithm (GA), adapting the restrictions of additive manufacturing and exploiting the EM properties
of loaded and non-loaded filaments, of which the elaboration is described. After optimization, a
bi-material multilayer absorber with a thickness of 4.1 mm has been designed to provide a reflectivity
below
−
12 dB between 8 and 18 GHz. Finally, the designed multilayer structure was 3D-printed
and measured in an anechoic chamber, achieving
−
11.8 dB between 7 and 18 GHz. Thus, the
development of dedicated materials has demonstrated the strong potential of additive technologies
for the manufacturing of thin wideband flexible EM absorbers.
Keywords:
electromagnetic multilayer absorber; genetic algorithm; 3D printing; filament making;
EM characterization
1. Introduction
The electromagnetic (EM) wave’s problematics are becoming more crucial and ubiqui-
tous, due to the development of electronic circuits and the rise of the Internet of Things.
There is thus a prominent need for EM absorbers to reduce the impact of generated signals
for various applications in different domains. For instance, the radar cross section (RCS)
reductions of military aircraft and boats are vital for stealth purposes against enemy radar
systems [
1
]; antenna devices require the mitigation of parasitic interferences from external
and internal sources to operate properly [
2
], and high-frequency circuits require the use of
microwave load to dissipate energy [
3
]. Besides, the performance and constraints of the
absorbers may vary in terms of operating frequencies, reflectivity at various angles and
polarizations, thickness, and stability in harsh environments. As such, different topologies
and materials have been investigated to fabricate EM absorbers. Usually, they are designed
to limit the reflection of incident waves by impedance matching, either by working on
geometry-like dielectric pyramids [
4
], or by gradually modifying their EM properties in
the case of composite absorbers [
5
]. Moreover, the absorption has to be increased by in-
troducing a way to mitigate the waves inside the absorbers through different types of
losses, multi-reflections, and interferences with the incident waves, such as the Dallenbach
screen [
6
]. To increase the bandwidth, multilayer structures can be used by working on the
Materials 2022, 15, 3320. https://doi.org/10.3390/ma15093320 https://www.mdpi.com/journal/materials
