Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41H—ARMOUR; ARMOURED TURRETS; ARMOURED OR ARMED VEHICLES; MEANS OF ATTACK OR DEFENCE, e.g. CAMOUFLAGE, IN GENERAL
  • F41H3/00—Camouflage, i.e. means or methods for concealment or disguise
  • F41H3/02—Flexible, e.g. fabric covers, e.g. screens, nets characterised by their material or structure
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
  • H01Q17/005—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems using woven or wound filaments; impregnated nets or clothes

Definitions

• the present invention relates to anti-radar nets.
• Anti-radar nets are known since many years. In general those nets consist of several layers of materials which partially absorb and partially reflect radar signals, at least one layer of which is a heterogeneous electricity conducting film which reflects part of the arriving radar waves. The reflected image should correspond to the surroundings where the concerned anti-radar nets are located.
• the purpose of the present invention is to provide anti- radar nets with a high attenuation, above 10 dB, at high frequency waves ( from 8 to 94 GHz ) , measured according to the known method of a monostatic setting, in which a radar wave from a source is emitted through a chamber or tunnel which is completely covered with absorbing material, except one plate at the extremety of said tunnel, situated in the so called window, by which the radar wave is reflected to the source of which the antenna is now used as receiver.
• a piece of the material is provided between de source/receiver and the reference plate, and the reflected signal is compared with the reflected signal without the radar net. The ratio of these two signals is called attenuation and is expressed in dB.
• the anti-radar nets according to the invention consist of a fabric and a coating layer on both sides, characterised in that the weft threads of the fabric are provided with metal fibers and at least one of the coating layers is provided with carbon fibers.
• the invention also relates to a manufacturing method for anti-radar nets.
• the first anti-radar panels were obtained from expanded metal grids. After that one has adopted various foils with dispersed metal fibers mixed therein, and/or with a punched metal foil between a support fabric and an external coating layer of synthetic material.
• the manufacturing method of the anti-radar nets of the invention is characterised in that the support fabric comprises weft threads with metal fibres whereas the coating layers, eg. made of synthetic material, are provided with carbon fibres which are distributed and mixed through the coating layer matrix by a foaming technique and then applied as coating layer onto the support fabric, and then calendered.
• the coating layers eg. made of synthetic material
• a fabric is woven, the warp threads of which are preferably spun exclusively from so called High Tenacity polyamide (HT pa ) and the weft threads of which consist partly of HT pa and partly of mixed yarn of polyamide - metal, in which the metal consists of rust-resistant fibers.
• HT pa High Tenacity polyamide
• the warp is made of 235 dtex HT polyamide, at 11,7 fibres/cm - whereas for the weft one uses one shot of 235 dtex HT polyamide at 8 fibres/cm, followed by two shots of mixed yarn of 20 dtex polyamide with rust-resistant fibres in a ratio of 94 % polyamide and 6 % rust-resistant fibres, at 17 fibres/cm.
• the content of metal can range from 0,5 to 10 g/m2. In the preferred embodiment of the invention the fabric contains approximately 2 g of metal per m2.
• composition of the fabric depends however to a large extent of the requirements set, eg. by user specifications, in respect of weight, tensile strenghth, tear resistance, etc...
• the use of metal in the weft allows to maintain a maximal tensile strength in the warp as well as a maximal processability of the fabric in the warp direction, whereas the carbon fibres ensure attenuation over a wide wave-band.
• the content of carbon fibres can range from 1 to 15 g/m2, with a preferred embodiment at around 5 g/m2.
• the diameter of the carbon fibres can range from 4 to 10 micron, with a preferred embodiment of around 7 micron and a specific electrical resistivity of around 18.106 ohm-meter, whereas the used fibre length can range from 0,4 to 8 mm, with a preferrence of around 3mm.
• a mix is used in which 50 % of the fibres have an average length of 3mm and 50% of the fibres have an average length of 0,5 mm.
• the overall content of carbon fibre is around 5g/m2.
• the carbon fibres are oriented in such way as to follow the warp direction.
• this coating matrix is foamed by means of a foaming device to a maximal homogeneity, and applied onto the fabric and then calendered.
• said layer will have a density of around 190 g/m2.
• the coated fabric is, according to a preferred embodiment of the invention, punched with a so called leaf pattern, ie. cut through with specific geometric figures looking like leaves or stylised leaves, in such a manner that when applying a tension to the fabric, said fabric deploys into a three dimensinal structure which is comparable to the leaves of a tree.
• the incident radar waves are thus reflected around in all directions.
• camouflaging anti-radar nets according to the invention executed with the characterizing features as described above, offer 20 to 100% better results than previous anti-radar nets with only metal fibres, or with a metal film or foil.
• the specular reflection is expressed in dB as the difference ( PI - P2 ) of the measured energy of the reflected signal of the camouflaging net ( P2 ) with respect to the energy reflected by a metal plate (PI) .

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
• Woven Fabrics (AREA)
• Laminated Bodies (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=3887045

Family Applications (1)

Country Status (3)

Family Cites Families (5)

• 1993
  • 1993-05-13 BE BE9300497A patent/BE1008923A5/nl not_active IP Right Cessation
• 1994
  • 1994-05-11 EP EP94917658A patent/EP0650577A1/de not_active Withdrawn
  • 1994-05-11 WO PCT/EP1994/001635 patent/WO1994027109A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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