Architectural geopolymer materials for X- and L-band radomes – MATGEORXL

The design of a radome is challenging because the performance criteria of the materials and the used technologies are generally not in accordance. That’s why the design must be optimized in order to satisfy the competing parameters. The design process is a compromise between electromagnetic transparency and mechanical strength properties. There is a large choice of dielectric materials with different intrinsic properties: electrical, mechanical, environmental aggressions resistance, and cost.
On one hand, the development of military platforms to respond to more and more demanding missions imposes new requirements on the design process of components and structures used in radomes. The evolutions in their design are accelerated by the complex requirements related to the new generations of platforms with or without pilot. These require increased transparency to electromagnetic waves, visual discretion, frequency selective surfaces, reduced weight and improved mechanical properties. On the other hand, the use of radomes for civil applications is massive. They must first and foremost provide protection from meteorological stresses and minimal impact on the functionality of the antenna. An appropriate design for a radome can globally improve the longevity of the system by simplifying maintenance operations, improve security against vandalism and increase discretion in the urban landscape. In addition, the materials used in the manufacturing process can contribute to reduce the environmental impact of the radome both in its manufacturing and in its dismantling. For military applications, airborne radomes used in airplanes and missiles are subject to high aerodynamic forces as well as a significant rise in temperature due to air friction. Their structures and materials must be chosen according to the speed of the airborne platform. For these reasons, ceramics are commonly used for the manufacture of radomes.
Geopolymers (IRCER) are mineral materials based on clay. They consolidate at low temperature (20 to 120°C) unlike traditional ceramics which require high temperature treatments. This new generation of materials, whether used pure, with fillers or reinforced, has already found numerous applications in industry (insulating foam for housing, refractory plates for fire protection, coatings on metal for corrosion protection). It is possible to synthesize materials with variable porosity, dense materials as well as geopolymer foams. This diversity of structures and properties has already led to the realization of Ultra Wide Band antennas [300 MHz - 3 GHz] and S-band absorbing loads in collaboration with XLIM.
As the knowledge and mastery in the manufacturing of geopolymer substrates progress, we could see the interest that these ceramics can represent for the defense sector (0.050 < l< 1.2 W/(m.K); 100 < s< 75 MPa; 3 = er = 5 and 2.10-2 = tand = 5.10-2). Thus, it clearly appears that the development of new material compositions and structurations will open new application fields in both the civil and defense sectors. Our ambition is therefore to develop new technological bricks that can interest both the defense for the development of radomes for communications interfaces and the telecommunications industry in the broadest sense through the design of urban and maritime protection devices, whose life cycle and carbon footprint would offer a relevant alternative solution to the petroleum-based materials usually used.