Researchers tested how carbon black formulation, polymer chemistry, and knitted fabric structure shape radar attenuation in a lightweight textile designed with multispectral camouflage in mind.
Paper: Flexible carbon black-coated fabrics for electromagnetic camouflage: Design and characterization. AI-generated abstract conceptual image created using ChatGPT/OpenAI
A recent study published in the journal Defence Technology introduced a lightweight camouflage fabric for military applications. Researchers developed flexible warp-knitted polyester fabrics coated with polymer composites containing carbon black-based pigments for electromagnetic concealment. They applied water-dispersible polymer-carbon black composite coatings to polyester mesh textiles, producing attenuation well above the 12 dB minimum cited by the Polish Defence Standard, but only within the 8-12 GHz X-band tested in the study. The resulting approach could provide a lightweight, flexible, and readily manufacturable platform for camouflage systems designed to integrate electromagnetic attenuation with visual and thermal camouflage requirements.
Challenges in Radar-Attenuating Camouflage
Modern radar technologies operate across approximately 1-94 GHz, with key reconnaissance bands at 5, 10, 35, and 94 GHz, increasing the demand for materials that can effectively attenuate electromagnetic signals. Conventional shielding often relies on rigid materials like metal oxides and ferrites, which can be heavy and limit flexibility. For military use, designers require lightweight, flexible absorbers capable of broadband attenuation while preserving the mechanical adaptability needed for camouflage materials. Carbon-based materials, particularly carbon black, are suitable for these applications due to their chemical stability and strong microwave absorption.
Design and Fabrication of Camouflage Material
Researchers evaluated water-dispersible polymers used in textiles, including an acrylic copolymer, an aliphatic polyurethane, and a polyvinyl chloride-ethylene copolymer. The conductive phase used three commercial carbon black-based pigments containing 30%, 45%, or 50% carbon black, with pigment concentrations of 10%, 20%, 50%, and 70% in the coating formulations to assess their effects on the coatings' properties.
The electromagnetic coatings were applied to two polyester warp-knitted mesh fabrics, designated D1 and D2. These substrates were chosen for their open-mesh structural design, which was intended to preserve partial visual translucency and thermal transmission. Polymer-carbon black composite pastes were then deposited onto the textile substrates using screen printing, enabling control over coating thickness while maintaining fabric flexibility.
Characterization of Coated Fabrics
The coated fabrics were characterized for electromagnetic, structural, and thermal properties. Microwave attenuation was measured in an anechoic chamber using linearly polarized horn antennas and a vector network analyzer. A direct reflection method was used to determine two-way attenuation across the X-band frequency range of 8-12 GHz.
Scanning electron microscopy (SEM) was used to examine coating morphology and uniformity, while thermogravimetric analysis was used to assess thermal stability. Thermal imaging was also used to quantify thermal transmission in the MWIR 3-5 μm and LWIR 8-12 μm spectral ranges.
Findings on Radar Attenuation and Durability
The outcomes demonstrated a clear relationship between pigment concentration, surface resistance, and electromagnetic attenuation. Coatings with approximately 10% pigment loading produced negligible attenuation and high surface electrical resistance. Increasing pigment loading to 20% substantially reduced surface resistance, indicating the formation of a continuous conductive network within the polymer matrix.
The highest radar attenuation was achieved with the acrylic copolymer combined with P3, a pigment containing 45% carbon black, at a pigment concentration of 70%. Under these conditions, fabric D1 demonstrated an attenuation of -27.1 dB, while fabric D2 reached -37.8 dB. The 45% carbon black P3 pigment outperformed the 50% carbon black P2 pigment, showing that carbon black content alone did not determine attenuation. The stronger attenuation of D2 was attributed to its textured fibers and more complex geometry, which promoted greater pickup of conductive paste under the same processing conditions.
The coated fabrics also showed modest reductions in thermal transmission, which the researchers attributed to coating-related decreases in textile porosity. Thermogravimetric analysis showed negligible mass loss from room temperature to approximately 300 °C, after which polymer degradation began; carbon black also affected degradation behavior at higher temperatures. Mechanical testing of selected coated samples involved 20,000 bending cycles, and SEM showed no visible degradation of either the coating layer or the textile fibers.
Applications in Military Camouflage Systems
The lightweight radar-absorbing textiles could be employed in multispectral camouflage coverings for military assets and equipment, with electromagnetic attenuation designed to work alongside visual and thermal camouflage requirements. Their flexibility and low weight make them suitable for camouflage nets and coverings deployed in various environments. The open-mesh design preserves partial visual translucency and allows thermal radiation to pass through the structure, while the coatings produced modest reductions in measured thermal transmission.
Because the coatings use commercially available components and can be applied via screen printing, this fabrication approach enables the production of camouflage materials in continuous lengths. Because radar attenuation was measured under controlled anechoic-chamber conditions only in the 8-12 GHz X-band, performance at other radar frequencies, angles of incidence, and under field conditions remains to be established. The thermal results also reflect controlled transmission measurements rather than direct tests of operational infrared detectability.
Conclusion and Future Directions
The study shows that flexible carbon black-coated knitted fabrics can provide significant radar attenuation while retaining low weight and mechanical flexibility. The electromagnetic performance depended on pigment loading, carbon black pigment formulation, the chemical composition of the water-dispersible polymer binder, and textile structure, indicating that material formulation and textile structure are crucial for refining signal attenuation.
The best-performing fabric achieved -37.8 dB of two-way attenuation in the tested 8- 12 GHz X-band at a thickness of approximately 1 mm. The results also showed that coating formulation and textile architecture influenced performance, while thermal and bending tests indicated that the material retained properties relevant to camouflage use. However, the laboratory measurements do not establish performance across the wider radar spectrum or under operational conditions.
These findings support the development of lightweight, flexible materials for multispectral camouflage and provide a basis for testing the fabrics under a wider range of detection and environmental conditions.
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