Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Scrim – Woven scrim
Patent
1995-05-24
1998-10-06
Bell, James J.
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Scrim
Woven scrim
428919, 442 58, 442133, 442288, 442294, B32B 700
Patent
active
058175830
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to radar attenuating materials, particularly to radar attenuating textiles. A particular preferred application of the materials of the present invention in the provision of camouflage netting is also provided.
Radio detection and ranging (RADAR) techniques are widely used to track and identify objects as well as to provide ground mapping. Objects are detected because they interfere with radiowaves directed at them in a different way to their surroundings. Because these techniques are highly developed and provide accurate detection, even in poor weather conditions, there is a military need to provide camouflage against them.
A known method of doing this is to shape the object so as to greatly reduce the amount of radar reflecting off its surface in the direction of the receiver. The usefulness of this technique is limited by the need to know the exact direction of the incident radar. More effective methods of decreasing radar signals are those which seek to absorb and/or scatter the radiowaves. Such methods include `Dual Absorbers` as described in WO 91/12173 and methods using a `Gradient Of Electrical Properties` as described in U.S. Pat. No. 4,162.426.
One of the main problems in providing camouflage against radar is the need for the signals which reflect off a potential target to match those caused by the surrounding terrain. Another main problem in producing and using radar attenuating materials is the fact that they are heavy and difficult to fabricate. It is therefore desirable to provide a textile which is relatively lightweight, easy to manufacture, use and store, yet provides good attenuation. Typical attenuation achieved with known camouflage is of the order of 3 dB. It is a further aim of the present invention to provide a novel approach for increasing attenuation of known camouflage formats in a relatively simple fashion.
The present invention provides a textile material having radar attenuating properties comprising a polymer enclosed scrim formed of fibre bundles characterised in that the material comprises hollows between the bundles of the scrim which are at least partially filled with radar attenuating material.
In a preferred embodiment of the invention the scrim is sandwiched between two or more polymeric layers, wherein the hollows comprise the interstices of the scrim. In a further preferred embodiment of the invention the scrim is coated with a polymer and the spaces are formed in the polymer within the interstices of the scrim.
Conveniently the scrim is sandwiched between two polymeric layers and the sandwiched scrim is subjected to conditions under which the polymeric layers fuse and coat the scrim fibres. For example, suitable heat and/or pressure may be applied to the polymer such that it softens or melts. Alternatively adhesive may be used to cause the scrim and polymer to bind together.
The material of the scrim should be selected to match the end use of the radar attenuating material to be produced. Particularly preferred materials for military use will be durable and strong fabrics such as those made from man-made fibres such as nylon and/or other polymeric materials eg. polyesters.
The material of the enclosing polymer material will also be selected to match the end use. Particularly preferred materials will be those which provide good coating properties and which can be used to carry visual and/or infrared pigmentation, for example polyvinyl chloride.
In a still further embodiment of the invention there is provided a material as described above characterised in that it comprises a polymeric material containing a conductive fibre wherein the fibres are arranged to provide further radar attenuating effect. These fibres are arranged within a polymeric matrix and may comprise such materials as stainless steel or carbon; such arrangement being known to be capable of, inter alia, scattering radar signals. The fibres may be provided in the same polymeric material as that which encloses the scrim or may be within a further polymeric material in one or mo
Alderson John
Vickers Alan F.
Bell James J.
The Secretary of State for Defence in her Britannic Majesty's Go
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