a) Field of the Invention
The present invention relates to material and methods of using a composite stock material structurally defined sheet, with a continuous and non-uniform surface embedded with and enveloping low signature particulate material which conforms to the contour of a non-planar surface. More particularly, the present invention relates to a thermo-mechanically-worked composite polymeric matrix sheet embedded with and enveloping low signature functional material and transfer coated with adhesive for the permanent retrofitting attachment onto vehicles.
b) Description of the Prior Art
It is advantageous for modern military vehicles to be afforded a facile method and means for reducing and eliminating both radar and optical signatures to avoid detection. A low signature response, for purposes of this invention, is defined as a contrary indication of and the minimum possible spectral signature of vehicle presence when subjected to radio-frequency signals and optical detection. Radio-frequency signals (RF), for the purpose of this invention, includes signals in the range between the UHF band (30 to 300 MHz) and Ku band (26 to 40 Ghz) inclusive.
The problem with utilizing paint on military vehicles to minimize visual detection is that it is too thin to contain an effective quantity of low signature RF material.
The prior art on vehicle coating teaches about polymeric films with pigment. Dobashi, et. al., U.S. Pat. No. 5,643,676, disclose a coating of a colored polyolefin film and a pressure sensitive adhesive layer. This non-shrink film is but a temporary coating for protection during vehicle transit.
The prior art on vehicle coating teaches about thermally deformable and thermoforming polymeric films with paint/pigment. Hartman, U.S. Pat. Nos. 5,030,513, 5,030,514, and 5,242,751, discloses paint composite articles comprising thermally and vacuum deformable carrier films having an adhesive layer on one surface and a paint layer on the other surface. Knop, et. al., U.S. Pat. No. 5,538,576, disclose a paint carrier film with an adhesion enhancer applied during original equipment manufacturing of the vehicle body part. Berner, et. al., U.S. Pat. No. 5,387,304, disclose a carrier film, coated on one side with paint and on the other with an adhesive, applied by thermoforming to the automotive body part. Pata, U.S. Pat. No. 5,034,077, and Benson, et. al., U.S. Pat. No. 4,913,760, disclose paint-coated polymeric films which are applied by vacuum thermoforming the films to the vehicle body part. The problem with this prior art is that the polymeric film must be applied to the vehicle body part using molds and under vacuum at the factory.
In the prior low signature art a paint additive and component was disclosed by Hubbard, U.S. Pat. No. 5,506,053. Hubbard is only a component of paint, and paint is too thin to contain an effective quantity of low signature RF material.
The RF coatings disclosed in the prior art do not all function to reduce the RF signature. Munro, et. al., U.S. Pat. No. 5,215,824, disclose an RF-transparent blanket. Amore, et. al., U.S. Pat. No. 5,373,306, Bogorad, et. al., U.S. Pat. No. 5,283,592, and Lepore, et. al., U.S. Pat. No. 5,373,305, disclose RF-transparent sunshield films. The polyimide film being utilized is not a shrink-film.