Planar, soft, wide-band stealth fabric and preparation method thereof

Abstract

The present invention relates to a planar, lightweight, broadband stealth fabric. The fabric comprises, from top to bottom, an optical / infrared-compatible camouflage layer, an absorbing / flexible dielectric insulation layer, and a protective layer stacked sequentially. The protective layer is a lightweight, breathable fabric. The optical / infrared-compatible camouflage layer is a thin fabric substrate with a camouflage pattern printed, dyed, or coated on the substrate surface. The camouflage pattern comprises at least four different camouflage patches, with the infrared emissivity difference between at least three of the camouflage patches being no less than 0.1. The absorbing / flexible dielectric insulation layer is formed by combining a fiber-based absorbent and a flexible dielectric material. The fiber-based absorbent comprises absorbing staple fibers of varying lengths. If the absorbing / flexible dielectric insulation layer is divided into several layers along the thickness direction, the center length of the absorbing staple fibers in each layer increases from top to bottom. This stealth fabric integrates optical, infrared, and radar stealth capabilities, is planar, and offers advantages such as softness, lightness, and broadband stealth, thus broadening its application range.

Description

Technical Field

[0001] The present invention relates to the technical field of stealth materials, and in particular to a planar, soft, wide-band stealth fabric and a preparation method thereof. Background Art

[0002] In modern warfare, with the continuous advancement of infrared and radar detection technology and various reconnaissance methods, "detect and destroy" poses a serious threat to battlefield weaponry and the survival of soldiers. Currently, wide-band compatible fabrics used in camouflage nets and clothing are often constructed from a conductive fabric substrate, printed with optical and infrared-compatible camouflage patterns, and then further cut. This cut pattern serves at least two purposes: first, the cut pattern structure at a certain height scatters radar waves, achieving radar stealth; second, the cut pattern structure allows for heat exchange and thermal equilibrium between the body or weapon's thermal components and the surrounding environment, facilitating thermal infrared camouflage; and third, the combined structure allows for lightweight camouflage equipment, avoiding the drawbacks of excessive weight. However, this current equipment still has major drawbacks during use: first, when this type of structure is used as camouflage clothing, the hook structure on the surface is not conducive to combat movements, nor is it conducive to compatibility with other equipment; second, this type of clothing is still relatively heavy, weighing more than 2.0 kg per set; third, although radar waves are scattered in all directions to different directions, weakening the echo, they are still easy to identify when using aerial radar detection.

[0003] In addition, Chinese patent application CN115325886A discloses a stealth material with high visible light transparency, infrared camouflage, and broadband radar absorption. The material is composed of multiple conductive layers and transparent layers arranged at intervals, and the stealth function is achieved by etching a periodic pattern on conductive glass. The material itself is very hard and cannot be bent, which has limitations in its application. Chinese patent CN112659664 B discloses an ultra-wideband thermal insulation / stealth / load-bearing / electromagnetic shielding integrated composite material and its preparation method. The composite material has ultra-wideband stealth performance, an absorption band that can be extended to 1GHz, and excellent thermal insulation performance. However, the structural design is complex, the process steps are relatively cumbersome, and it lacks flexibility, making it unsuitable for stealth camouflage applications for portable equipment on the battlefield. Based on this, the field urgently needs to develop and design a lightweight, planar structure with broadband stealth fabric that absorbs visible light, infrared, and radar. Summary of the Invention

[0004] (1) Technical issues to be resolved

[0005] In view of the above-mentioned disadvantages and deficiencies of the prior art, the present invention provides a planar, soft and wide-band stealth fabric and a preparation method thereof. This stealth fabric integrates optical / infrared / radar stealth functions, is soft, lightweight, and has good wearability. It can be used for the camouflage of portable equipment and has a wider application scope. The surface of the stealth material is planar, which makes the material thinner and lighter, and does not cause snagging problems, which is beneficial to combat skills. It has a wide-band stealth function, and the effective absorption bandwidth less than -10 dB within the range of 2-18 GHz reaches about 10 GHz, effectively solving the deficiencies of existing stealth materials.

[0006] (II) Technical Solution

[0007] The technical solution of the present invention is as follows:

[0008] In the first aspect, the present invention provides a planar, soft and wide-band stealth fabric, which is successively stacked with an optical / infrared compatible camouflage layer, an absorbing / flexible medium heat insulation layer, and a protective layer from the upper surface to the lower surface; the protective layer is a lightweight and breathable fabric;

[0009] The optical / infrared compatible camouflage layer is based on a thin fabric, and optical / infrared camouflage is printed or coated on its upper surface. The optical / infrared camouflage includes more than 4 kinds of color camouflage patches, and the infrared emissivity difference of at least three camouflage patches is not less than 0.1;

[0010] The absorbing / flexible medium heat insulation layer is a composite functional layer formed by compounding fibrous absorbents and flexible medium materials, which has the functions of absorbing waves, bearing, and heat insulation; among them, the fibrous absorbents include absorbing short fibers with different length distributions;

[0011] If the side of the absorbing / flexible medium heat insulation layer close to the upper surface is the outer side and the side close to the protective layer is the inner side, the absorbing / flexible medium heat insulation layer is divided into several layers from the outer side to the inner side. Each layer of absorbing short fibers includes absorbing short fibers with different length distributions, and each layer of absorbing short fibers has a central length. The central length of the absorbing short fibers increases successively from the outer side to the inner side. [[ID=!19]]

[0012] ! For example, if the absorbing / flexible medium heat insulation layer is divided into n layers, the side closest to the upper surface is the 1st layer, and the side closest to the protective layer is the nth layer on the inner side. The central lengths of the absorbing short fibers from the 1st layer to the nth layer are L1, L2, L3... Ln, then L1 < L2 < L3... Ln-1 < Ln; among them, each layer is distributed with no less than 3 kinds of specifications of absorbing short fibers; the absorbing short fibers of different specifications are added in equal amounts in each layer, and the content of the absorbing short fibers in each layer is 0.5-7 g / m 2 .

[0013] According to a preferred embodiment of the present invention, the protective layer is a woven fabric made of polyester, polypropylene or viscose fiber, and its thickness is not greater than 0.5 mm.

[0014] According to a preferred embodiment of the present invention, the optical / infrared camouflage includes camouflage patches of more than five colors.

[0015] According to a preferred embodiment of the present invention, the colors of the optical / infrared camouflage include yellow-green, dark green, silver-gray, brown and black; or sand, red soil, brown soil, silver-gray, brown and black; or light gray, medium gray, silver-gray, dark gray, brown and black.

[0016] According to a preferred embodiment of the present invention, in the absorbing / flexible dielectric insulation layer, the fiber-based absorber is one or a combination of glass-coated amorphous magnetic fiber, stainless steel fiber, carbon fiber, modified carbon fiber, modified silicon carbide fiber, polycrystalline iron fiber, iron-nickel fiber and iron-cobalt-nickel fiber; preferably, the fiber-based absorber is glass-coated amorphous magnetic fiber or carbon fiber.

[0017] According to a preferred embodiment of the present invention, the microwave-absorbing short fibers include microwave-absorbing short fibers with a length distribution of 1-20 mm and a diameter of 6 μm-12 μm.

[0018] According to a preferred embodiment of the present invention, the flexible dielectric material in the absorbing / flexible dielectric insulation layer is foam / sponge, a textile, or a non-woven fabric. Preferably, the foam / sponge can be, for example, porous polyurethane foam / polyurethane sponge, and the textile can be, for example, a spacer fabric. The non-woven fabric can be a non-woven fabric produced by a wet-laid process using ordinary textile staple fibers. During the wet-laid process, a fiber-based absorbent can be mixed with the ordinary textile staple fibers, thereby incorporating the fiber-based absorbent into the non-woven fabric.

[0019] The common textile staple fibers include viscose fibers, polyester fibers, nylon fibers, cellulose fibers, polypropylene fibers, polyethylene fibers, water-soluble vinylon fibers, polyacrylic fibers, ethylene-vinyl acetate copolymer fibers, PE / PP fibers (blended spinning of PE and PP), PE / PET (blended spinning of PE and PET) fibers and other common textile fibers.

[0020] The lightweight, soft, heat-absorbing, and insulating properties of these flexible dielectric materials make them suitable for wearable stealth protection or portable equipment, particularly polyurethane sponges and spacer fabrics. However, wet-laid nonwovens allow for a more uniform distribution of absorbing staple fibers throughout the thickness of the absorbing / flexible dielectric insulation layer, preventing them from concentrating on specific sides or at specific depths.

[0021] Spacer fabrics are composed of two or more layers of yarn formed from multiple groups of yarns, each connected by another group of yarns. The yarns connecting the layers are typically sparse, and the spacing between adjacent layers is relatively large, allowing for a larger amount of filler to be injected. In this invention, the filler is a mixture of a fiber-based absorbent and a binder.

[0022] According to a preferred embodiment of the present invention, the weight per square meter of the flexible dielectric material in the wave absorbing / flexible dielectric insulation layer is not greater than 100 g / m 2 , thickness not more than 1.5mm, dielectric constant 2.1-4.7.

[0023] According to a preferred embodiment of the present invention, the preparation method of the wave absorbing / flexible dielectric insulation layer includes any one of the following methods:

[0024] Method 1: A fiber-based absorbing agent and an adhesive are mixed and coated to form an absorbing layer, which is then laminated onto a flexible dielectric material to form a single-layer flexible absorbing material. The absorbing layer has a thickness of 40-3000 μm, and the flexible dielectric material has a thickness of 0.5-3 mm. Two or more layers of the single-layer flexible absorbing material are laminated to form the absorbing / flexible dielectric insulation layer.

[0025] Method 2: A fiber-type absorbent is mixed with ordinary textile staple fibers, and a single-layer flexible absorbing material is prepared by a wet-laid web forming process; the thickness of the single-layer flexible absorbing material is not less than 0.5 mm; two or more layers of the single-layer flexible absorbing material are stacked and compounded to obtain the absorbing / flexible dielectric insulation layer;

[0026] Method 3: A fiber-based absorber and an adhesive are mixed and coated to obtain an absorbing layer, and the absorbing layer is compounded onto a flexible dielectric material to obtain a first single-layer flexible absorbing material; the fiber-based absorber is mixed with ordinary textile staple fibers, and a second single-layer flexible absorbing material is prepared by a wet-laid web forming process; the first and second single-layer flexible absorbing materials are stacked and compounded to obtain the absorbing / flexible dielectric insulation layer.

[0027] The common textile staple fibers are viscose fibers, polyester fibers, nylon fibers, cellulose fibers, polypropylene fibers, polyethylene fibers, water-soluble vinylon fibers, polyacrylic fibers, ethylene-vinyl acetate copolymer fibers, PE / PP fibers, PE / PET fibers and other common textile fibers.

[0028] According to a preferred embodiment of the present invention, the wave-absorbing / flexible dielectric heat-insulating layer is formed by laminating three flexible wave-absorbing layers. The length of the wave-absorbing short fibers in the first layer is 1-10 mm (central length L1), the fiber length in the second layer is 7-15 mm (central length L2), and the fiber length in the third layer is 10-18 mm (central length L3), with L1 < L2 < L3; there are no less than three specifications of wave-absorbing short fibers distributed in each layer.

[0029] Preferably, the wave-absorbing short fibers of different specifications and lengths in each layer are added in equal amounts, and the content of the wave-absorbing short fibers in each layer is 0.5-7 g / m 2 . For example, the length of the wave-absorbing short fibers in the first layer is 1-10 mm, including 1 part by mass of wave-absorbing short fibers with a length of 3 mm, 1 part by mass of wave-absorbing short fibers with a length of 6 mm, and 1 part by mass of wave-absorbing short fibers with a length of 9 mm, that is, the wave-absorbing short fibers of the three lengths are mixed and added in a ratio of 1:1:1, and the contents of the wave-absorbing short fibers of the three specifications are 0.6-1 g / m 2 .

[0030] Second, the present invention also provides a method for preparing a planar soft wide-band stealth fabric, which includes:

[0031] S1. Prepare an optical / infrared compatible camouflage layer:

[0032] Print or coat an optical / infrared dye or coating on the upper side of a light fabric substrate (such as polyester fabric) to obtain an optical / infrared compatible camouflage pattern, and the camouflage pattern includes camouflage patches of more than 4 colors, where the infrared emissivity difference of at least three camouflage patches is not less than 0.1;

[0033] S2. Prepare a wave-absorbing / flexible dielectric heat-insulating layer, and the preparation method is one or a combination of the following methods:

[0034] Method 1: Mix a fibrous wave-absorbing agent with an adhesive and coat to obtain a wave-absorbing layer, and compound the wave-absorbing layer onto a flexible dielectric material to obtain a single-layer flexible wave-absorbing material. The thickness of the wave-absorbing layer is 40-300 μm, and the thickness of the flexible dielectric material is 0.5-3 mm; stack and compound two or more single-layer flexible wave-absorbing materials to obtain the wave-absorbing / flexible dielectric heat-insulating layer;

[0035] Method 2: Mix a fibrous wave-absorbing agent with ordinary textile staple fibers and prepare a single-layer flexible wave-absorbing material through a wet laying process; the thickness of the single-layer flexible wave-absorbing material is not less than 0.5 mm; stack and compound two or more single-layer flexible wave-absorbing materials to obtain the wave-absorbing / flexible dielectric heat-insulating layer;

[0036] Method 3: A fiber-based absorbent and an adhesive are mixed and coated to form an absorbing layer, which is then laminated onto a flexible dielectric material to form a first single-layer flexible absorbing material; the absorbing layer has a thickness of 40-3000 μm, and the flexible dielectric material has a thickness of 0.5-3 mm; the fiber-based absorbent is mixed with ordinary textile staple fibers, and a second single-layer flexible absorbing material having a thickness of not less than 0.5 mm is prepared by a wet-laid web forming process; the first and second single-layer flexible absorbing materials are laminated and laminated to form the absorbing / flexible dielectric insulation layer;

[0037] S3, Composite

[0038] The optical / infrared compatible camouflage layer, the wave absorbing / flexible dielectric insulation layer, and the protective layer are connected and fixed by adhesive or sewing thread. The adhesive includes any one of oily polyurethane, water-based polyurethane, or polyethyl hot melt adhesive (85° C.).

[0039] The invisible fabric thus obtained generally has a grammage of 275-295g / m2. 2 The thickness is between 2.5-2.8mm.

[0040] (3) Beneficial effects

[0041] The planar, soft, wide-band stealth fabric of the present invention has the following main features:

[0042] (1) The stealth fabric of the present invention is lightweight, soft, and flexible, making it suitable for wear or use as camouflage for portable equipment. It is easy to fold and carry, and can be easily cut and sewn according to the requirements of the equipment. It has a wide range of applications and can achieve relatively lightweight camouflage equipment without the disadvantages of being too thick or heavy. A set of clothing made of this stealth fabric can be reduced to less than 1 kg in thickness. It is soft and breathable, and is very comfortable to wear.

[0043] (2) The stealth fabric of the present invention is planar and has no protruding hook points on the surface when used as camouflage clothing, which is beneficial for combat movements and compatibility with other equipment.

[0044] (3) The stealth fabric of the present invention is compatible with optical / infrared / radar stealth functions. It is provided with an optical / infrared compatible camouflage layer on the outside and an absorbing / flexible dielectric insulation layer in the middle to isolate the heat generated by the human body or equipment to achieve infrared stealth. The absorbing / flexible dielectric insulation layer is also filled with a large amount of fiber-type absorbents to absorb radar waves to achieve radar stealth. The fiber-type absorbents include absorbing short fibers of different lengths. The length, diameter, orientation, arrangement, content, etc. of the absorbing short fibers determine the electromagnetic absorption parameters and stealth frequency band width of the stealth fabric. In the stealth fabric of the present invention, the center length of the absorbing staple fibers increases successively from top to bottom in the thickness direction. Each layer is distributed with absorbing staple fibers of various lengths, and their orientation and arrangement are randomly formed (including various orientations or crossing or overlapping). This further enhances the electromagnetic loss of electromagnetic waves by the stealth fabric of the present invention, resulting in further enhanced echo weakening capability, making it more difficult to be detected by airborne radar, and enabling the stealth fabric to have wide-band stealth performance. In the range of 2-18 GHz, the effective absorption bandwidth is less than -10 dB and reaches about 10 GHz. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic structural diagram of a planar, soft, wide-band stealth fabric according to the present invention.

[0046] Figure 2 This is a schematic structural diagram of another planar, soft, wide-band stealth fabric of the present invention.

[0047] Figure 3 This is the wave frequency-reflectivity curve of the planar, soft, wide-band stealth fabric of Example 1.

[0048] Figure 4 This is the wave frequency-reflectivity curve of the planar, soft, wide-band stealth fabric of Example 2.

[0049] Figure 5 This is the wave frequency-reflectivity curve of the planar, soft, wide-band stealth fabric of Example 3.

[0050] Figure 6 This is the wave frequency-reflectivity curve of the planar, soft, wide-band stealth fabric of Comparative Example 1.

[0051] Figure 7 This is the wave frequency-reflectivity curve of the planar, soft, wide-band stealth fabric of Comparative Example 2.

[0052] Figure 8 This is the wave frequency-reflectivity curve of the planar, soft, wide-band stealth fabric of Comparative Example 3. DETAILED DESCRIPTION

[0053] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below with reference to the accompanying drawings through specific embodiments. The materials, reagents, raw materials, etc. used in the following examples were all obtained from commercial sources unless otherwise specified.

[0054] Combine Figure 1 The figure shows the structure of a planar, flexible, broadband stealth fabric according to the present invention. From top to bottom, it comprises an optical / infrared-compatible camouflage layer 1, a radar-absorbing / flexible dielectric insulation layer 2, and a protective layer 3. Protective layer 3 is a lightweight, breathable fabric, preferably a woven fabric made of polyester, polypropylene, or viscose, with a thickness of no more than 0.5 mm.

[0055] The topmost optical / infrared-compatible camouflage layer 1 is based on a lightweight fabric. Its upper surface is dyed with dyes or coated with optical / infrared paint to create a camouflage pattern. The camouflage pattern includes camouflage patches of four or more colors, with the difference in infrared emissivity of at least three of the camouflage patches being no less than 0.1. The lightweight fabric is preferably polyester. Preferably, the camouflage pattern includes camouflage patches of five or six colors, such as yellow-green, dark green, silver-gray, brown, and black; or six colors: sand, red earth, cinnamon, silver-gray, brown, and black; or light gray, medium gray, silver-gray, dark gray, brown, and black. During the camouflage production process, an appropriate amount of 20μm aluminum powder is added to the pigment to increase the infrared emissivity of the camouflage patches.

[0056] The absorbing / flexible dielectric insulation layer 2 is the functional layer in the planar, flexible, wide-band stealth fabric of the present invention that primarily serves as a radar stealth layer. The absorbing / flexible dielectric insulation layer 2 is a composite functional layer formed by combining a fiber-based absorber 21 with a flexible dielectric material, exhibiting both absorbing, load-bearing, and insulating properties. The fiber-based absorber 21 comprises short absorbing fibers of varying lengths. Specifically, the fiber-based absorber 21 can be selected from one or a combination of glass-coated amorphous magnetic fibers, stainless steel fibers, carbon fibers, modified carbon fibers, modified silicon carbide fibers, polycrystalline iron fibers, iron-nickel fibers, and iron-cobalt-nickel fibers, preferably glass-coated amorphous magnetic fibers or carbon fibers. The short absorbing fibers comprise short absorbing fibers with a length distribution of 1-20 mm and a diameter of 6 μm-12 μm.

[0057] The absorbing / flexible dielectric insulation layer 2 is prepared by mixing a fiber-based absorber 21 with a binder (water-based polyurethane) to form a slurry. The slurry is then applied to a flexible dielectric material 22 to produce a single-layer flexible absorbing material. The absorbing layer on the single-layer flexible absorbing material has a thickness of 40-3000 μm, and the thickness of the flexible dielectric material 22 is 0.5-3 mm. The absorbing / flexible dielectric insulation layer 2 is then formed by stacking and compounding two or more layers of the single-layer flexible absorbing material. The fiber-based absorber 21 is specifically short absorbing fibers.

[0058] If the side of the absorbing / flexible dielectric insulation layer 2 close to the optical / infrared compatible camouflage layer 1 is the outer side, and the side close to the protective layer is the inner side. The absorbing / flexible dielectric insulation layer is divided into several layers from the outer side to the inner side, and the absorbing staple fibers of each layer contain absorbing staple fibers with different length distributions. The absorbing staple fibers of each layer have a center length, and the center lengths of the absorbing staple fibers increase from the outer side to the inner side. For example, when preparing the absorbing / flexible dielectric insulation layer 2 according to the aforementioned method, when preparing the first layer (the layer close to the optical / infrared compatible camouflage layer 1) of a single-layer flexible absorbing material, a fiber-type absorber 21 with a shorter fiber length (center length of L1) is selected and mixed with an adhesive to prepare a pulp, and then applied to the flexible dielectric material 22 to obtain the first layer of a single-layer flexible absorbing material; when preparing the second layer (located below the first layer), a fiber-type absorber 21 with a longer fiber length (center length of L2>L1) is selected and mixed with an adhesive to prepare a pulp. Mix and pulp, and after coating, produce a single-layer flexible absorbing material for the second layer. When preparing the third layer (located below the second layer), a fiber-type absorber 21 with a longer fiber length (center length L3>L2) is selected and mixed with an adhesive to produce a pulp, and after coating, a single-layer flexible absorbing material for the third layer is produced. Similarly, the fiber length of the fiber-type absorber 21 used in the absorbing / flexible dielectric insulation layer 2 gradually increases from top to bottom. Finally, the aforementioned single-layer flexible absorbing materials are stacked together to produce the absorbing / flexible dielectric insulation layer 2. Each layer contains at least three different lengths of absorbing staple fibers. Preferably, the absorbing staple fibers of different lengths are added in equal amounts, with the total absorbing staple fiber content in each layer being 0.5-7g / m 2 .

[0059] For example, the length of the absorbing short fibers in the first layer is 1-10 mm (the center length is 5.5 mm), and the total content of the absorbing short fibers is 2.4 g / m 2 The length of the absorbing short fibers includes four specifications: 1mm, 3mm, 7mm and 9mm, and the content is 0.6g / m 2 The second layer of fiber length is 7-15mm (center length is 11mm), and the total content of absorbing short fibers is 1.5g / m 2 The length of the absorbing short fibers includes three specifications: 7mm, 9mm and 15mm, and the content is 0.5g / m 2 If a third layer is provided, the fiber length of the third layer is 10-18 mm (center length is 14 mm), and the total content of the absorbing short fibers is 2.0 g / m 2 The length of the absorbing short fibers includes four specifications: 10mm, 12mm, 15mm and 18mm, and the content is 0.5g / m 2 .

[0060] The flexible dielectric material 22 is made of foam / sponge, textile, or non-woven fabric. For example, the foam / sponge can be porous polyurethane foam / polyurethane sponge; the textile can be polyester spacer fabric. Spacer fabric is a fabric formed by forming two or more layers of fabric from a plurality of groups of yarns, with each layer of fabric connected by another group of yarns. The yarns connecting the layers of fabric are generally sparse, and the spacing between adjacent layers of fabric is relatively large, allowing for a large amount of filler (such as a slurry mixed with a fiber absorber 21 and an adhesive). The non-woven fabric can be a non-woven fabric prepared from ordinary textile staple fibers through a wet-laid web forming process. Ordinary textile staple fibers are common polymer fibers, including viscose fibers, polyester fibers, nylon fibers, cellulose fibers, polypropylene fibers, polyethylene fibers, water-soluble vinylon fibers, polyacrylic fibers, ethylene-vinyl acetate copolymer fibers, PE / PP fibers (blends of PE and PP), PE / PET fibers (blends of PE and PET), and other ordinary textile fibers. The square meter weight of the flexible dielectric material 22 is not greater than 100 g / m2. 2 , thickness not more than 1.5mm, dielectric constant 2.1-4.7.

[0061] After the optical / infrared compatible camouflage layer 1 and the absorbing / flexible dielectric insulation layer 2 are prepared, the optical / infrared compatible camouflage layer 1, the absorbing / flexible dielectric insulation layer 2, and the protective layer 3 are stacked and secured together using an adhesive or sewing thread. The adhesive may be any of oil-based polyurethane, water-based polyurethane, or a polyethyl hot melt adhesive (85°C).

[0062] In the above scheme, the preparation process of the absorbing / flexible dielectric insulation layer 2 is relatively simple and the speed is fast. The flexible dielectric material used is lightweight, soft, heat-absorbing and heat-insulating, making the stealth fabric suitable for making wearable stealth protective materials or portable equipment stealth protective materials, especially the polyurethane sponge is lightweight, soft, and has excellent thermal insulation function.

[0063] like Figure 2 The figure shows the structure of another planar, soft, wide-band stealth fabric of the present invention. Figure 1The structures shown differ only in the preparation method of the absorbing / flexible dielectric insulation layer 2, resulting in a different distribution of the absorbing staple fibers therein. Specifically, the preparation method of the absorbing / flexible dielectric insulation layer 2 comprises: mixing a fibrous absorber 21 with ordinary textile staple fibers to form a pulp, and then preparing a single layer of flexible absorbing material through a wet-laid web forming process; the thickness of the single layer of flexible absorbing material is not less than 0.5 mm; and two or more layers of the single layer of flexible absorbing material are stacked and composited to form the absorbing / flexible dielectric insulation layer 2. The ordinary textile staple fibers include viscose fibers, polyester fibers, nylon fibers, cellulose fibers, polypropylene fibers, polyethylene fibers, water-soluble vinylon fibers, polyacrylic fibers, ethylene-vinyl acetate copolymer fibers, PE / PP fibers, PE / PET fibers, and other ordinary textile fibers, with a length of 4-10 mm.

[0064] Among them, if the side of the absorbing / flexible dielectric insulation layer 2 close to the optical / infrared compatible camouflage layer 1 is the outer side, and the side close to the protective layer is the inner side. The absorbing / flexible dielectric insulation layer is divided into several layers from the outer side to the inner side, and the absorbing staple fibers of each layer contain absorbing staple fibers with different length distributions. The absorbing staple fibers of each layer have a center length, and the center lengths of the absorbing staple fibers increase from the outer side to the inner side. For example, when preparing the absorbing / flexible dielectric insulation layer 2 according to the aforementioned method, first, a fiber-type absorber 21 with a shorter fiber length (center length of L1) is mixed with ordinary textile staple fibers to make pulp, and a single-layer flexible absorbing material (with the fiber-type absorber 21 embedded therein) of the first layer is prepared by a wet-laid web process; when preparing the second layer (located below the first layer), a fiber-type absorber 21 with a longer fiber length (center length of L2>L1) is selected and mixed with ordinary textile staple fibers to make pulp, and a single-layer flexible absorbing material (fiber-type absorber 21) of the second layer is prepared by a wet-laid web process. In the preparation of the third layer (located below the second layer), a fiber-type absorber 21 with a longer fiber length (center length L3>L2) is selected and mixed with ordinary textile staple fibers to make pulp, and a single layer of flexible absorbing material (with the fiber-type absorber 21 embedded therein) of the third layer is prepared by a wet-laid web forming process... and so on, the fiber length of the fiber-type absorber 21 used in the absorbing / flexible dielectric insulation layer 2 gradually increases from top to bottom, and finally the aforementioned single layers of flexible absorbing materials are stacked together to obtain the absorbing / flexible dielectric insulation layer 2. Similarly, each layer has no less than three types of absorbing staple fibers of different lengths. Preferably, absorbing staple fibers of different lengths are added in equal amounts, and the absorbing staple fiber content of each layer is 0.5-7g / m 2 .

[0065] For example, the length of the absorbing short fibers in the first layer is 2mm, 3mm, 4mm and 5mm (center length is 3.5mm) in four specifications. Ordinary textile short fibers include 4mm cellulose fibers and 5mm PET fibers, which are mixed and pulped. The single-layer flexible absorbing material of the first layer is prepared by a wet-laid web forming process, in which the total content of the absorbing short fibers is 2.4g / m 2 Among them, the four specifications of 2mm, 3mm, 4mm and 5mm are 0.6g / m 2 The lengths of the absorbing staple fibers in the second layer are 8mm, 10mm, and 12mm (center length is 10mm). Ordinary textile staple fibers include 4mm cellulose fibers and 5mm PET fibers. They are mixed and pulped, and a single-layer flexible absorbing material for the second layer is prepared through a wet-laid web process. The total content of the absorbing staple fibers is 1.5g / m 2 The three specifications of absorbing short fibers are 0.5g / m 2 .

[0066] Similarly, after the optical / infrared compatible camouflage layer 1 and the wave-absorbing / flexible dielectric insulation layer 2 are prepared, the optical / infrared compatible camouflage layer 1, the wave-absorbing / flexible dielectric insulation layer 2 and the protective layer 3 are stacked and fixed with adhesive or sewing thread.

[0067] and Figure 1 The absorbing / flexible dielectric insulation layer 2 shown is slightly different. Figure 1 The medium absorbing short fibers are mainly laminated on the surface of a single layer of flexible absorbing material; Figure 2 The absorbing / flexible dielectric insulation layer 2 shown is prepared by a wet-laid web process for each layer, so that absorbing staple fibers of different lengths are embedded in the absorbing / flexible dielectric insulation layer and evenly distributed along the thickness direction of the entire absorbing / flexible dielectric insulation layer, avoiding aggregation on a certain side or at a certain depth. At the same time, it is also not easy for the absorbing staple fibers to peel off and be lost due to aging and delamination of the adhesive material or damage to the material.

[0068] The following describes the characteristics and technical effects of the stealth fabric of the present invention in conjunction with specific embodiments.

[0069] Example 1

[0070] The structure of the planar, soft, broadband stealth fabric of this embodiment can be found in Figure 1 As shown, the preparation method is as follows:

[0071] (1) Preparation of visible light / infrared coating camouflage cloth: First, prepare five color slurries, which are yellow-green, dark green, silver-gray, brown, and black. Add appropriate amount of 20 μm aluminum powder to the yellow-green, silver-gray, and brown slurries and coat them on a polyester fabric base (80 g / m 2The front of the 150-mesh plate screen is coated with yellow-green, dark green, silver-grey, brown and black slurries in sequence, and then dried to form a 5-color woodland camouflage pattern with a total weight of 100g / m 2 .

[0072] (2) Preparation of absorbing / flexible dielectric insulation layer: Glass-coated amorphous magnetic fibers with a fineness of 24.5 dtex (core layer diameter of 12 μm, shell thickness of 4 μm, glass-coated amorphous magnetic fiber diameter of 14 μm) were chopped into absorbing fibers with lengths of 3 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 12 mm, and 14 mm.

[0073] The absorbing short fibers with lengths of 3 mm, 5 mm, 7 mm and 9 mm, and the specifications of each length are 1 g / m 2 , dispersed on a 1.1mm polyurethane sponge by sieving, sprayed with water-based polyurethane to fix the fibers, and obtained the first layer of a single-layer flexible absorbing material.

[0074] The absorbing short fibers with lengths of 6 mm, 8 mm, 10 mm and 12 mm, each with a length specification of 0.5 g / m 2 , dispersed on a 1.1mm polyurethane sponge by sieving, sprayed with water-based polyurethane to fix the fibers, and obtained the second layer of single-layer flexible absorbing material.

[0075] The total thickness of the two layers is 2.2mm and the weight is 105g / m 2 .

[0076] (3) Multilayer composite: Use oil-based polyurethane to apply dots between layers to obtain a four-layer composite fabric.

[0077] The invisible fabric thus obtained has a grammage of 275g / m2 2 , thickness 2.8mm. Among them, the infrared emissivity of the surface fabric (8-14μm) is: silver-gray patch (low emission) 0.55, yellow-green patch (medium emission) 0.67, brown patch (medium emission) 0.70, dark green patch (high emission) 0.92, black patch (high emission) 0.93, and the difference between the infrared emissivity of different patches is greater than 0.1. Figure 3 As shown, the wave frequency-reflectivity curve of the stealth fabric of this embodiment shows that in the range of 2-18 GHz, the effective absorption bandwidth less than -10 dB is 10.1 GHz.

[0078] Example 2

[0079] The structure of the planar, soft, broadband stealth fabric of this embodiment can be found in Figure 1 As shown, the preparation method is as follows:

[0080] (1) Preparation of visible light / infrared coating camouflage cloth: First, prepare 6 color slurries, which are sand, red soil, brown soil, silver gray, brown, and black. Add appropriate amount of 20 μm particle size aluminum powder to the sand, red soil, silver gray, and brown slurries, and coat them on a polyester fabric base (70 g / m 2 The front of the 150-mesh plate screen is coated with sand, red soil, brown soil, silver gray, brown, and black slurries in sequence, and then dried to form a 6-color desert camouflage pattern with a total weight of 92g / m 2 .

[0081] (2) Preparation of absorbing / flexible dielectric insulation layer: Carbon fibers with a diameter of 8 μm were chopped into absorbing short fibers with lengths of 2 mm, 3 mm, 4 mm, 5 mm, 7.5 mm, 8.5 mm, and 9.5 mm.

[0082] The absorbing short fibers with lengths of 2 mm, 3 mm, 4 mm and 5 mm, each with a length specification of 0.6 g / m 2 , mixed with the polyurethane solution, and evenly sprayed on the 1mm polyester spacer fabric using a spray gun to obtain the first layer of single-layer flexible absorbing material.

[0083] The absorbing short fibers with lengths of 7.5 mm, 8.5 mm and 9.5 mm, and the specifications of each length are 0.3 g / m 2 , mixed with the polyurethane solution, and evenly sprayed on the 1mm polyester spacer fabric using a spray gun to obtain the second layer of single-layer flexible absorbing material.

[0084] The total thickness of the two layers is 2mm and the weight is 110g / m 2 .

[0085] (3) Multi-layer composite: Use polyethylene hot melt adhesive to bond the layers to obtain a four-layer composite fabric.

[0086] The invisible fabric thus obtained has a grammage of 286g / m2. 2 , thickness 2.6mm. Among them, the infrared emissivity of the surface fabric (8-14μm) is: sandy patches (low emission) 0.57, silver-gray patches (low emission) 0.55, red soil patches (medium emission) 0.68, brown patches (medium emission) 0.72, brown soil patches (high emission) 0.90, black patches (high emission) 0.91, and the difference between the infrared emissivity of different patches is greater than 0.1. Figure 4 As shown, the wave frequency-reflectivity curve of the stealth fabric of this embodiment shows that in the range of 2-18 GHz, the effective absorption bandwidth less than -10 dB is 9.9 GHz.

[0087] Example 3

[0088] The structure of the planar, soft, broadband stealth fabric of this embodiment can be found in Figure 2 As shown, the preparation method is as follows:

[0089] (1) Preparation of visible light / infrared coating camouflage cloth: First, prepare 6 color slurries, which are light gray, medium gray, silver gray, dark gray, brown, and black. Add appropriate amount of 20 μm aluminum powder to the light gray, medium gray, silver gray, and brown slurries and coat them on a polyester fabric base (85 g / m 2 The front of the 150-mesh plate screen is coated with light gray, medium gray, silver gray, dark gray, brown, and black slurries in sequence, and then dried to form a 6-color urban camouflage pattern with a total weight of 102g / m 2 .

[0090] (2) Preparation of wave-absorbing / flexible dielectric insulation layer: Glass-coated amorphous magnetic fibers with a fineness of 16.3 dtex (core layer diameter of 9.3 μm, shell thickness of 2 μm, glass-coated amorphous magnetic fiber diameter of 10.3 μm) were chopped into lengths of 2 mm, 3 mm, 4 mm, 5 mm, 8 mm, 9 mm, 10 mm, 13 mm, 15 mm, and 17 mm.

[0091] The absorbing short fibers with lengths of 2 mm, 3 mm, 4 mm and 5 mm were each 0.6 g / m 2 , mixed with 4mm cellulose fiber and 5mm PET fiber, the first layer of single-layer flexible absorbing material is prepared by wet-laid process; the thickness is 0.6mm and the total weight is 65g / m 2 .

[0092] The absorbing short fibers with lengths of 8 mm, 9 mm and 10 mm were made into 0.5 g / m 2 , mixed with 4mm cellulose fiber and 5mm PET fiber, and prepared by wet-laid process to form the second layer of single-layer flexible absorbing material; thickness is 0.6mm, total weight is 65g / m 2 .

[0093] The absorbing short fibers with lengths of 13 mm, 15 mm and 17 mm, each with a length of 1 g / m 2 , mixed with 4mm cellulose fiber and 5mm PET fiber, and prepared by wet-laid process to form the third layer of single-layer flexible absorbing material; thickness is 0.4mm, total weight is 45g / m 2 .

[0094] The total thickness of the three layers is 1.8mm and the weight is 202g / m 2 .

[0095] (3) Multilayer composite: Use oil-based polyurethane to apply dots between layers to obtain a five-layer composite fabric.

[0096] The invisible fabric thus obtained has a grammage of 295g / m2. 2 , thickness 2.5mm. Among them, the infrared emissivity of the surface fabric (8-14μm) is: light gray patch (low emission) 0.51, silver gray patch (low emission) 0.55, medium gray patch (medium emission) 0.66, brown patch (medium emission) 0.70, dark gray patch (high emission) 0.91, black patch (high emission) 0.90, and the difference between the infrared emissivity of different patches is greater than 0.1. Figure 5 As shown, the wave frequency-reflectivity curve of the stealth fabric of this embodiment shows that in the range of 2-18 GHz, the effective absorption bandwidth less than -10 dB is 10.5 GHz.

[0097] Comparative Example 1

[0098] This comparative example refers to Example 1, and steps (1) and (3) are the same as in Example 1. The only difference between this example and Example 1 is the method for preparing the absorbing / flexible dielectric insulation layer. In this example, glass-coated amorphous magnetic chopped fibers of the same specifications as in Example 1 were prepared, including absorbing short fibers with lengths of 3 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 12 mm, and 14 mm, but not dispersed in layers.

[0099] Among them, the absorbing short fibers with lengths of 3mm, 5mm, 7mm and 9mm (the dispersion density of each length specification is 1g / m 2 ) and short absorbing fibers with lengths of 6mm, 8mm, 10mm and 12mm (the dispersion density of each length specification is 0.5g / m 2 ) are mixed together, dispersed on a 1.1mm polyurethane sponge by sieving, and sprayed with water-based polyurethane to fix the fibers to obtain a single-layer flexible absorbing material with a thickness of 1.1mm and a gram weight of 54g / m 2 Prepare two layers of flexible absorbing material in the same manner as above. The final multi-layer composite method is as described in Example 1.

[0100] The infrared emission of the surface fabric of the stealth fabric prepared in this example is the same as that in Example 1, and its wave frequency-reflectivity curve is as follows: Figure 6 As shown, in the range of 2-18 GHz, the effective absorption bandwidth less than -10 dB is 3 GHz. Compared with the reflectivity curve of Example 1, the absorption bandwidth is narrow and the intensity is low.

[0101] Comparative Example 2

[0102] This comparative example refers to Example 1, and steps (1) and (3) are the same as those in Example 1. The only difference between this example and Example 1 is the preparation method of the wave absorbing / flexible dielectric insulation layer. Specifically, the single-layer flexible wave absorbing material of the first layer and the single-layer flexible wave absorbing material of the second layer in Example 1 are stacked in reverse order. The total thickness of the two layers is 2.2 mm, and the gram weight is 105 g / m 2 The final multi-layer composite method is shown in Example 1. The thus obtained stealth fabric has a grammage of 275 g / m2. 2 , thickness 2.8mm.

[0103] The infrared emission of the surface fabric of the stealth fabric prepared in this example is the same as that in Example 1, and its wave frequency-reflectivity curve is as follows: Figure 7 As shown, in the range of 2-18 GHz, the effective absorption bandwidth less than -10 dB is 2.56 GHz. Compared with the reflectivity curve of Example 1, the absorption bandwidth is narrow.

[0104] Comparative Example 3

[0105] This comparative example refers to Example 1, and steps (1) and (3) are the same as those in Example 1. The only difference between this example and Example 1 is the preparation method of the wave absorbing / flexible dielectric insulation layer. Specifically, the glass-coated amorphous magnetic fibers in Example 1 are chopped to obtain lengths of 24 mm and 38 mm. The wave absorbing short fibers of 24 mm in length are chopped at 4 g / m 2 The dispersion density is dispersed on a 1.1mm polyurethane sponge by sieving, and water-based polyurethane is sprayed to fix the fibers to obtain the first layer of a single-layer flexible absorbing material. Then, a 38mm long absorbing short fiber is sprayed at a density of 2g / m 2 The dispersion density is dispersed on a 1.1mm polyurethane sponge by screening, and water-based polyurethane is sprayed to fix the fibers to obtain a second layer of single-layer flexible absorbing material. The total thickness of the two layers is 2.2mm and the weight is 105g / m 2 The final multi-layer composite method is shown in Example 1. The thus obtained stealth fabric has a grammage of 275 g / m2. 2 , thickness 2.8mm.

[0106] The infrared emission of the surface fabric of the stealth fabric prepared in this example is the same as that in Example 1, and its wave frequency-reflectivity curve is as follows: Figure 8 As shown, in the range of 2-18 GHz, the effective absorption bandwidth less than -10 dB is 0 GHz. Compared with the reflectivity curve of Example 1, the absorption effect is extremely poor.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flat, soft, wide-band stealth fabric, characterized in that: An optical / infrared compatible camouflage layer, a wave absorbing / flexible dielectric insulation layer, and a protective layer are stacked in sequence from the upper surface to the lower surface; the protective layer is a lightweight and breathable fabric; The optical / infrared compatible camouflage layer is based on a thin fabric with an optical / infrared camouflage pattern printed or coated on its upper surface. The optical / infrared camouflage pattern comprises camouflage patches of four or more colors, wherein the difference in infrared emissivity of at least three of the camouflage patches is not less than 0.

1. The absorbing / flexible dielectric insulation layer is a composite functional layer formed by combining a short-cut fiber absorber and a flexible dielectric material, which has the functions of absorbing, bearing, and insulating. The fiber absorber includes short absorbing fibers of different lengths distributed based on the center length, which are closely related to the absorbing frequency band. The total thickness of the composite layer is no greater than 3 mm, and when tested in a flat state, the bandwidth with a reflectivity no greater than -10 dB is no less than 8 GHz. The side of the absorbing / flexible dielectric insulation layer close to the upper surface is defined as the outer side, and the side close to the protective layer is defined as the inner side. The absorbing / flexible dielectric insulation layer is divided into several layers from the outer side to the inner side. The absorbing staple fibers of each layer contain absorbing staple fibers of different lengths distributed based on the center length, which are closely related to the absorbing frequency band. The absorbing staple fibers of each layer have a center length, and the center length of the absorbing staple fibers increases successively from the outer side to the inner side.

2. The flat, soft, broadband stealth fabric according to claim 1, characterized in that: The protective layer is a woven fabric made of polyester, polypropylene or viscose fiber, and its thickness is not more than 0.5 mm.

3. The flat, soft, broadband stealth fabric according to claim 1, characterized in that: The optical / infrared camouflage includes camouflage patches of more than 5 colors.

4. The flat, soft, broadband stealth fabric according to claim 3, characterized in that: The colors of the optical / infrared camouflage include yellow-green, dark green, silver-gray, brown and black; or sand, red soil, brown soil, silver-gray, brown and black; or light gray, medium gray, silver-gray, dark gray, brown and black.

5. The flat, soft, broadband stealth fabric according to claim 1, characterized in that: In the absorbing / flexible dielectric insulation layer, the fiber-based absorber is one or a combination of glass-coated amorphous magnetic fiber, stainless steel fiber, carbon fiber, modified carbon fiber, modified silicon carbide fiber, polycrystalline iron fiber, iron-nickel fiber and iron-cobalt-nickel fiber; the absorbing short fibers include absorbing short fibers with a length distribution of 1-20 mm.

6. The flat, soft, broadband stealth fabric according to claim 1, characterized in that: The flexible dielectric material in the wave-absorbing / flexible dielectric heat-insulating layer is foam / sponge, textile or non-woven fabric.

7. The flat, soft, broadband stealth fabric according to claim 1, characterized in that: The weight per square meter of the flexible dielectric material in the wave absorbing / flexible dielectric insulation layer is not more than 100 g / m 2 , thickness not more than 1.5mm, dielectric constant 2.1-4.

7.

8. The planar, soft, broadband stealth fabric according to any one of claims 1 to 7, characterized in that: The preparation method of the wave absorbing / flexible dielectric insulation layer includes any one of the following methods: Method 1: A fiber-based absorbing agent and an adhesive are mixed and coated to form an absorbing layer, which is then laminated onto a flexible dielectric material to form a single-layer flexible absorbing material. The absorbing layer has a thickness of 40-3000 μm, and the flexible dielectric material has a thickness of 0.5-3 mm. Two or more layers of the single-layer flexible absorbing material are laminated to form the absorbing / flexible dielectric insulation layer. Method 2: A fiber-type absorbent is mixed with ordinary textile staple fibers, and a single-layer flexible absorbing material is prepared by a wet-laid web forming process; the thickness of the single-layer flexible absorbing material is not less than 0.5 mm; two or more layers of the single-layer flexible absorbing material are stacked and compounded to obtain the absorbing / flexible dielectric insulation layer; Method 3: A fiber-based absorber and an adhesive are mixed and coated to obtain an absorbing layer, and the absorbing layer is compounded onto a flexible dielectric material to obtain a first single-layer flexible absorbing material; the fiber-based absorber is mixed with ordinary textile staple fibers, and a second single-layer flexible absorbing material is prepared by a wet-laid web forming process; the first and second single-layer flexible absorbing materials are stacked and compounded to obtain the absorbing / flexible dielectric insulation layer.

9. The flat, soft, broadband stealth fabric according to claim 8, characterized in that: The common textile staple fibers are one or more of viscose fibers, polyester fibers, nylon fibers, cellulose fibers, polypropylene fibers, polyethylene fibers, water-soluble vinylon fibers, polyacrylic fibers, ethylene-vinyl acetate copolymer fibers, PE / PP fibers or PE / PET fibers.

10. A method for preparing the planar, soft, broadband stealth fabric according to any one of claims 1 to 9, characterized in that: include: S1. Preparation of optical / infrared compatible camouflage layer: Printing an optical / infrared dye on the upper side of a thin fabric substrate or applying an optical / infrared paint on the upper side of a thin fabric substrate to obtain an optical / infrared compatible camouflage pattern, wherein the camouflage pattern comprises camouflage patches of four or more colors, wherein the difference in infrared emissivity of at least three of the camouflage patches is not less than 0.1; S2. Prepare a wave-absorbing / flexible dielectric insulation layer by one or a combination of the following methods: Method 1: A fiber-based absorbing agent and an adhesive are mixed and coated to form an absorbing layer, which is then laminated onto a flexible dielectric material to form a single-layer flexible absorbing material. The absorbing layer has a thickness of 40-3000 μm, and the flexible dielectric material has a thickness of 0.5-3 mm. Two or more layers of the single-layer flexible absorbing material are laminated to form the absorbing / flexible dielectric insulation layer. Method 2: A fiber-type absorbent is mixed with ordinary textile staple fibers, and a single-layer flexible absorbing material is prepared by a wet-laid web forming process; the thickness of the single-layer flexible absorbing material is not less than 0.5 mm; two or more layers of the single-layer flexible absorbing material are stacked and compounded to obtain the absorbing / flexible dielectric insulation layer; Method 3: A fiber-based absorbent and an adhesive are mixed and coated to form an absorbing layer, which is then laminated onto a flexible dielectric material to form a first single-layer flexible absorbing material; the absorbing layer has a thickness of 40-3000 μm, and the flexible dielectric material has a thickness of 0.5-3 mm; the fiber-based absorbent is mixed with ordinary textile staple fibers, and a second single-layer flexible absorbing material having a thickness of not less than 0.5 mm is prepared by a wet-laid web forming process; the first and second single-layer flexible absorbing materials are laminated and laminated to form the absorbing / flexible dielectric insulation layer; S3, Composite The optical / infrared compatible camouflage layer, the wave absorbing / flexible medium heat insulation layer, and the protective layer are connected and fixed by adhesive or sewing thread.

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