Novel three-dimensional fabric-based composite material capable of regulating and controlling electromagnetic shielding and preparation method of novel three-dimensional fabric-based composite material

Abstract

The invention discloses a novel three-dimensional fabric-based composite material capable of regulating and controlling electromagnetic shielding and a preparation method thereof.The three-dimensional fabric-based composite material comprises a three-dimensional fabric and filling polymer foam, and the three-dimensional fabric comprises an upper surface layer, a lower surface layer and middle layer spacer yarn used for connecting the upper surface layer and the lower surface layer; the upper layer is a glass fiber and carbon fiber blended fabric, the lower layer is a carbon fiber fabric, and the spacing yarns in the middle layer are carbon fibers. By combining the carbon fibers and the glass fibers, the composite material can provide effective electromagnetic shielding in an X wave band range, reflection can be effectively reduced, and a more stable electromagnetic environment is provided.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding materials, and in particular to a novel three-dimensional fabric-based composite material with adjustable electromagnetic shielding and a preparation method thereof. Background Art

[0002] Electromagnetic waves are a type of oscillating particle waves derived from synchronously oscillating and mutually perpendicular electric and magnetic fields in space, covering a wide frequency range. Electromagnetic waves are widely used in communications, navigation, radar, medical imaging and other fields. Although electromagnetic waves have many benefits, long-term exposure to high-intensity or specific types of electromagnetic waves may also have adverse effects on human health. For example, high-frequency electromagnetic waves (such as microwaves and infrared rays) can cause tissue heating, leading to burns or other thermal injuries.

[0003] In order to solve the harm of the above electromagnetic waves to human health, the research of electromagnetic shielding materials has received more and more attention. According to their physical form and application methods, electromagnetic shielding materials mainly include films, fabrics, foams and coatings. According to the material properties, electromagnetic shielding materials mainly include metal materials, conductive composite materials, conductive polymers, magnetic materials, ceramic materials, etc. Among them, electromagnetic shielding fabrics are textiles woven by mixing conductive fibers (such as metal fibers, metal-plated fibers, carbon fibers, etc.) with other fibers. Electromagnetic shielding fabrics include two-dimensional electromagnetic shielding fabrics, three-dimensional electromagnetic shielding fabrics (such as spacer yarn fabrics), non-woven electromagnetic shielding materials, coatings and composite electromagnetic shielding fabrics, etc. Among them, spacer yarn fabrics are a special three-dimensional fabric. By introducing connecting yarns perpendicular to the plane (such as Z-direction yarns), a multilayer composite material with a stable spatial structure is formed. It has the characteristics of large spacing design, multi-functional integration, high elastic recovery, etc., and can be used in medical care, sports goods, construction and civil engineering and other fields.

[0004] Although spacer yarn fabrics have advantages such as excellent mechanical properties, good physical properties, lightweight design, and multifunctional integration, they also have the following disadvantages: (1) Uneven electromagnetic shielding effect: Although three-dimensional fabrics have good mechanical properties in multiple directions, due to the uneven fiber arrangement and structure, the electromagnetic shielding effect of the material may vary in different directions. Especially for high-frequency electromagnetic waves (such as X-band), this anisotropy is more obvious, which may lead to poor local shielding effect.

[0005] (2) Different shielding effects for low-frequency and high-frequency electromagnetic waves: Different fiber types and structural designs have different shielding effects on electromagnetic waves of different frequencies. For example, metal fibers have a good shielding effect on low-frequency electromagnetic waves, but the effect on high-frequency electromagnetic waves may not be as expected; on the contrary, magnetic materials have a good absorption effect on low-frequency electromagnetic waves, but the shielding effect on high-frequency electromagnetic waves (such as X-band) is poor.

[0006] (3) Uneven density distribution: Due to the arrangement of fibers in space, the density distribution of the spacer yarn fabric may be uneven, resulting in poor electromagnetic shielding effect in local areas. This unevenness is particularly evident in designs with large spacing.

[0007] (4) The high conductivity of carbon fiber enables it to effectively reflect electromagnetic waves, but over-reliance on reflection may lead to multiple reflections and secondary interference, especially in closed spaces or complex environments.

[0008] Therefore, there is an urgent need for a composite material that has impedance matching for electromagnetic waves and can reduce secondary reflection. Summary of the invention

[0009] The purpose of the present invention is to provide a novel three-dimensional fabric-based composite material with adjustable electromagnetic shielding and a preparation method thereof, so as to solve the problem that the above-mentioned composite material has more secondary reflections and poor electromagnetic shielding effect.

[0010] To achieve the above-mentioned objectives, the first aspect of the present invention provides a new type of adjustable electromagnetic shielding three-dimensional fabric-based composite material, the three-dimensional fabric-based composite material includes a three-dimensional fabric and filled polymer foam, the three-dimensional fabric includes an upper layer, a lower layer and an intermediate layer of spacer yarns for connecting the upper layer and the lower layer, the upper layer is a glass fiber and carbon fiber blended fabric, the lower layer is a carbon fiber fabric, and the intermediate layer of spacer yarns is carbon fiber.

[0011] In view of the problem that the electromagnetic shielding effect in the prior art is not good enough, the present invention introduces glass fiber into carbon fiber fabric to further reduce the reflectivity of electromagnetic waves of spacer yarn fabric composite material (carbon fiber spacer yarn / polyurethane foam composite material), and reduces the reflection of electromagnetic waves by the fabric by changing the overall dielectric properties of the carbon fiber fabric, so as to achieve the purpose of regulating electromagnetic waves. The glass fiber / carbon fiber spacer yarn fabric (G / C-SF) of the present invention is a three-dimensional fabric woven from the top, middle and bottom as a whole; the upper layer of G / C-SF is a glass fiber / carbon fiber mixed fabric, and the change of the fabric structure can play a role in regulating electromagnetic shielding; the lower layer of G / C-SF is full carbon fiber, which can play a final attenuation role on the electromagnetic waves that finally enter the composite material, preventing the electromagnetic waves from penetrating the composite material, and the middle is filled with polymer foam, which is composited with the fabric later.

[0012] The spacer yarn fabric designed by the present invention is a typical sandwich hollow structure, which is a typical Fabry-Pérot cavity structure. The interior is separated by upper and lower conductive fiber fabric layers and the middle spacer yarn, which can form multiple reflection surfaces and conductive cavities. Electromagnetic waves are reflected multiple times in the cavity. When they are in phase with the reflected waves, resonance peaks will be generated, resulting in interference of electromagnetic waves and achieving frequency selection. This is a simple and effective means to achieve frequency selective electromagnetic shielding composite materials.

[0013] Preferably, the weave structure of the upper layer and the lower layer is one of plain weave, twill weave and satin weave.

[0014] The weave structures of the upper layer and the lower layer in the present invention are not limited to plain weave, twill weave and satin weave, and may also be other complex weave structures.

[0015] Preferably, the filled polymer foam is one or more combinations of polyurethane foam, epoxy foam, phenolic foam, and acrylic foam. The filled polymer foam in the present invention is not limited to the above-mentioned ones, and any polymer foam material that can play a filling role can be used in the present invention. Functional materials such as carbon black, carbon nanotubes, graphene, and nickel powder can also be added to the filled polymer foam material according to actual needs.

[0016] Preferably, the height of the spacer yarn in the middle layer is greater than 0 mm and less than 20 mm.

[0017] Preferably, the texture of the upper layer is plain weave.

[0018] Preferably, the upper layer is a blend of glass fiber and carbon fiber, wherein all the warp yarns are woven with carbon fibers or each glass fiber is woven with each two carbon fibers in a cyclic arrangement, and every n glass fibers in the weft yarn are woven alternately with every m carbon fibers, m≥1, n≥1.

[0019] The present invention replaces part of the carbon fiber in the upper layer with glass fiber, and uses a specific warp and weft composition to weave the composite material. The present invention can adjust the overall conductivity and electromagnetic shielding effectiveness of the composite material by adjusting the ratio of glass fiber to carbon fiber. The presence of glass fiber reduces the conductivity of the composite material, thereby reducing the reflection of electromagnetic waves to a certain extent. Specifically, glass fiber can increase the impedance matching of the composite material to electromagnetic waves, introduce more electromagnetic waves into, and reduce reflection. This combination of glass fiber and carbon fiber enables the composite material to provide an effective shielding effect within the X-band range. The mixing of glass fiber and carbon fiber can form a more complex fiber network at a microscopic scale and optimize the multi-scale structure of the material. This structure can improve the overall performance of the composite material, including mechanical properties, electromagnetic shielding properties and thermal management properties. The interface bonding between glass fiber and polymer matrix is ​​usually good, which helps to improve the overall strength and durability of the composite material and reduce the risk of interface debonding. If the upper layer is all made of carbon fiber, the carbon fiber has a higher conductivity and mainly shields electromagnetic waves by reflection. However, excessive reliance on reflection may cause secondary reflection, increase electromagnetic pollution and electromagnetic interference. In addition, carbon fiber has limited absorption effect on high-frequency electromagnetic waves, especially for high-frequency electromagnetic waves such as the X-band (8.2~12.4 GHz). Relying solely on carbon fiber may not achieve the ideal shielding effect.

[0020] The present invention can achieve fine control of electromagnetic shielding performance by reasonably adjusting the ratio of carbon fiber and glass fiber to meet the needs of different application scenarios. For example, in some cases, a stronger reflection effect may be required; while in other cases, more emphasis may be placed on absorption effect. The combination of carbon fiber and glass fiber can be optimized according to specific needs to provide the best shielding solution.

[0021] The high conductivity of the carbon fiber in the present invention enables it to effectively reflect electromagnetic waves, but over-reliance on reflection may lead to multiple reflections and secondary interference, especially in closed spaces or complex environments. The addition of glass fiber can reintroduce some of the reflected electromagnetic waves into the middle layer of the composite material for attenuation, reducing the occurrence of multiple reflections and secondary interference. This helps to improve the electromagnetic compatibility (EMC) of the system and avoid unnecessary electromagnetic interference. Therefore, the combination of carbon fiber and glass fiber in the present invention can effectively reduce multiple reflections and secondary interference and provide a more stable electromagnetic environment, which is particularly important for applications that are sensitive to electromagnetic interference, such as radar systems and communication equipment.

[0022] A second aspect of the present invention provides a method for preparing a three-dimensional fabric-based composite material, comprising the following steps: S1: Preparation of three-dimensional fabrics: The three-dimensional fabric is woven on a loom, the lower layer and the middle layer of spacer yarn are carbon fiber, and the upper layer is a mixed weave of glass fiber and carbon fiber, which are woven alternately according to the organization structure to obtain G / C-SF; S2: Preparation of composite materials: The cut G / C-SF is placed in a mold and fixedly packaged, and then the raw materials for filling polymer foam are added through the reserved injection port of the mold. After the foaming is completed, the G / C-SF / PF composite material is demolded.

[0023] Preferably, in step S2, the filling polymer foam is polyurethane foam.

[0024] Preferably, in step S2, the polyurethane foam raw materials are mixed by: Weigh polyether polyol and isocyanate respectively, stir at 800-1500 rpm for 5-30 seconds to mix evenly, and obtain a polyurethane foam raw material.

[0025] Preferably, in step S2, the mass ratio of polyether polyol to isocyanate is (1-3): (1-3).

[0026] More preferably, in step S2, the mass ratio of polyether polyol to isocyanate is 1:1.

[0027] Preferably, in step S2, the foaming time is 10 to 60 minutes.

[0028] In the present invention, before G / C-SF is placed in the mold, a layer of resin (which may be water-based polyurethane, epoxy resin, etc. as required) may be coated on its surface, placed in an oven for curing, and the cured material is then placed in the mold.

[0029] Therefore, the present invention adopts a novel adjustable electromagnetic shielding three-dimensional fabric-based composite material and a preparation method thereof, which has the following beneficial effects: The glass fiber in the present invention regulates the organizational structure of the carbon fiber spacer yarn fabric to obtain a glass fiber / carbon fiber spacer yarn fabric (that is, a three-dimensional fabric), which can effectively enhance the impedance matching of the carbon fiber fabric composite material to electromagnetic waves, reduce secondary reflection, and achieve the purpose of regulating the electromagnetic shielding of the glass fiber / carbon fiber spacer yarn fabric composite material through changes in the organizational structure.

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The structure diagram of the three-dimensional fabric prepared in Example 1; Figure 2 This is a structural diagram of the G / C-SF / PUF composite material prepared in Example 1; Figure 3 The average power coefficient of the composite materials prepared in the embodiments and comparative examples in the X-band; In the figure: 1, upper layer; 2, middle layer; 3, lower layer; 4, filling polymer foam. DETAILED DESCRIPTION

[0032] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the present invention is not limited to this embodiment.

[0033] Example 1 A method for preparing a novel three-dimensional fabric-based composite material with adjustable electromagnetic shielding comprises the following steps: S1: Preparation of three-dimensional fabrics: The three-dimensional fabric-based composite material includes a three-dimensional fabric and a filled polymer foam, wherein the three-dimensional fabric includes an upper layer, a lower layer, and an intermediate layer of spacer yarns for connecting the upper layer and the lower layer, wherein the upper layer is a glass fiber and carbon fiber blended fabric, the lower layer is a carbon fiber fabric, and the intermediate layer of spacer yarns is carbon fiber, wherein the specifications of the carbon fiber and the glass fiber are 198 tex.

[0034] The three-dimensional fabric is woven on a loom, the bottom layer and the middle layer of spacer yarn are carbon fiber, and the top layer is a mixed weave of glass fiber and carbon fiber, which are woven alternately according to the plain weave structure to obtain G / C-SF; Specifically, during the weaving process, the warp yarns are weaved in a manner that each glass fiber is cyclically arranged with each two carbon fibers, and the weft yarn is arranged in a manner that the glass fiber and the carbon fiber are cyclically arranged with each other to adjust the weft yarn structure. The height of the spacer yarn is 10 mm, and the weft yarn in this embodiment is woven alternately with each glass fiber and each carbon fiber. The prepared three-dimensional fabric is recorded as G1C1-SF. The above process of weaving according to the weaving structure is a commonly used method in the art and will not be repeated here.

[0035] S2: Preparation of composite materials: The cut G1C1-SF (18 cm × 18 cm) was placed in a mold and fixedly packaged. 16 g of polyether polyol (A material / black material) and 16 g of isocyanate (B material / white material) were weighed respectively, and stirred at 1000 rpm for 10 s to mix them evenly to obtain a mixed solution. The mixed solution was injected from the reserved injection port of the mold. After 10 minutes of free foaming, the polyurethane foam PUF filled the entire spacer yarn fabric. After the PUF reaction was completed, the G1C1-SF / PUF composite material was obtained after demolding. The structure diagram of the G1C1-SF / PUF composite material is shown in Figure 1 and Figure 2 .

[0036] Polyether polyol, model TC-1012A, purchased from Dongguan Keshengda Trading Co., Ltd.; Isocyanate, model TC-1012B, was purchased from Dongguan Keshengda Trading Co., Ltd.

[0037] Example 2

[0038] The difference between this embodiment and embodiment 1 is: the ratio of glass fiber to carbon fiber in the weft yarn during the weaving process in step S1. In this embodiment, the weft yarn is woven alternately with every 2 glass fibers and every 2 carbon fibers. The prepared three-dimensional fabric is recorded as G2C2-SF, and the final composite material is recorded as G2C2-SF / PUF.

[0039] Example 3 The difference between this embodiment and embodiment 1 is: the ratio of glass fiber to carbon fiber in the weft yarn during the weaving process in step S1. In this embodiment, the weft yarn is woven alternately with every 3 glass fibers and every 3 carbon fibers. The prepared three-dimensional fabric is recorded as G3C3-SF, and the final composite material is recorded as G3C3-SF / PUF.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is: the ratio of glass fiber to carbon fiber in the weft yarn during the weaving process in step S1. In this comparative example, all the weft yarns are alternately woven with glass fibers. The prepared three-dimensional fabric is recorded as G-SF, and the composite material finally obtained is recorded as G-SF / PUF.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that in the weaving process of step S1, the ratio of glass fiber to carbon fiber in the weft yarn is that in this comparative example, all the weft yarns are alternately woven with carbon fibers, the prepared three-dimensional fabric is recorded as C-SF, and the composite material finally obtained is recorded as C-SF / PUF.

[0042] Test example The composite materials prepared in the examples and comparative examples were tested for X-band electromagnetic shielding effect. The test results are shown in Figure 3 .

[0043] Figure 3 is the average power coefficient of the G / C-SF / PUF composite material in the X-band, Figure 3 The reflectivity (R), transmittance (T) and absorptivity (A) are shown in the figure. R+A+T=1. The higher the A value, the higher the material's absorptivity to electromagnetic waves. The lower the R value, the lower the secondary reflection of electromagnetic waves by the material. Figure 3It can be seen that the absorption rate (A) value of the G / C-SF / PUF composite material changes significantly with the change of the organizational structure of the upper layer of G / C-SF (the range of A value: 0.06~0.37), among which the absorption rate (A) of the G3C3-SF / PUF composite material is the highest, with a value of 0.37, which indicates that it has the greatest absorption of electromagnetic waves and reduces the secondary reflection of electromagnetic waves to space, further illustrating that the organizational structure changes of the glass fiber and carbon fiber on the upper layer of G / C-SF / PUF can effectively regulate the R value (reflectivity) and A value (absorption rate) of the G / C-SF / PUF composite material. The present invention can effectively achieve the purpose of regulating the electromagnetic shielding performance of the G / C-SF / PUF composite material by changing the organizational structure of the glass fiber and carbon fiber.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A novel three-dimensional fabric-based composite material with adjustable electromagnetic shielding, characterized in that: The three-dimensional fabric-based composite material includes a three-dimensional fabric and filled polymer foam. The three-dimensional fabric includes an upper layer, a lower layer and an intermediate layer of spacer yarns for connecting the upper layer and the lower layer. The upper layer is a glass fiber and carbon fiber mixed fabric, the lower layer is a carbon fiber fabric, and the intermediate layer of spacer yarns is carbon fiber.

2. The novel adjustable electromagnetic shielding three-dimensional fabric-based composite material according to claim 1, characterized in that: The weave structure of the upper layer and the lower layer is one of plain weave, twill weave and satin weave.

3. The novel adjustable electromagnetic shielding three-dimensional fabric-based composite material according to claim 1, characterized in that: The filling polymer foam is one or more combinations of polyurethane foam, epoxy foam, phenolic foam and acrylic foam.

4. The novel adjustable electromagnetic shielding three-dimensional fabric-based composite material according to claim 1, characterized in that: The structure of the upper layer is plain weave.

5. The novel adjustable electromagnetic shielding three-dimensional fabric-based composite material according to claim 4, characterized in that: The upper layer is a blend of glass fiber and carbon fiber, wherein all the warp yarns are weaved with carbon fiber or each glass fiber is weaved with each two carbon fibers in a cyclic arrangement, and each n glass fibers in the weft yarn are woven alternately with each m carbon fibers, m≥1, n≥1.

6. The method for preparing a three-dimensional fabric-based composite material according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Preparation of three-dimensional fabrics: The three-dimensional fabric is woven on a loom, the lower layer and the middle layer of spacer yarn are carbon fiber, and the upper layer is a mixed weave of glass fiber and carbon fiber, which are woven alternately according to the organization structure to obtain G / C-SF; S2: Preparation of composite materials: The cut G / C-SF is placed in a mold and fixedly packaged, and then the raw materials for filling polymer foam are added through the reserved injection port of the mold. After the foaming is completed, the G / C-SF / PF composite material is demolded.

7. The method for preparing a three-dimensional fabric-based composite material according to claim 6, characterized in that: In step S2, the filling polymer foam is polyurethane foam.

8. The method for preparing a three-dimensional fabric-based composite material according to claim 7, characterized in that: In step S2, the polyurethane foam raw materials are mixed by: Weigh polyether polyol and isocyanate respectively, stir at 800-1500 rpm for 5-30 seconds to mix evenly, and obtain a polyurethane foam raw material.

9. The method for preparing a three-dimensional fabric-based composite material according to claim 8, characterized in that: In step S2, the mass ratio of polyether polyol to isocyanate is (1-3): (1-3).

10. The method for preparing a three-dimensional fabric-based composite material according to claim 6, characterized in that: In step S2, the foaming time is 10 to 60 minutes.

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