A foam sandwich structure with broadband electromagnetic absorption and lattice mechanical reinforcement

Abstract

The application discloses a foam sandwich structure with broadband electromagnetic wave absorption and lattice mechanics enhancement, belongs to the technical field of electromagnetic wave absorbing materials, and comprises, from top to bottom, a wave-transparent panel, a resistive film composite foam core material and an electromagnetic wave reflecting back plate; the resistive film composite foam core material is wrapped with orthogonal lattice webs around; the resistive film composite foam core material comprises a plurality of resistive film composite foam core layers; each resistive film composite foam core layer comprises a foam layer and a resistive film piece which is combined on the foam layer; the resistive film piece comprises a wave-transparent composite material piece and a resistive film layer; and the resistive film layer is printed on the wave-transparent composite material piece. The glass fiber reinforced resin-based composite material is used as the panel layer and the bidirectional lattice web, the basic mechanics performance of the structure is ensured, the resistive films with different square resistance values are combined in the foam core material, and the broadband electromagnetic wave absorption performance is achieved.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to a foam sandwich structure that combines broadband electromagnetic absorption and lattice mechanical enhancement. Background Technology

[0002] Microwave absorbing materials and structures have significant application value in the field of radar stealth. High-performance stealth structures not only need to meet the requirements of broadband absorption and strong absorption, but also need to meet application requirements such as small thickness, high strength, and mechanical load-bearing capacity. Circuit-simulated absorbers, as a type of microwave absorbing material, are composed of a frequency-selective surface and a metal backplate. Frequency-selective surfaces come in many types and offer strong combination capabilities, providing high design freedom. Excellent electromagnetic absorption performance can be achieved through structural design and geometric parameter optimization. Compared to traditional Salisbury and Jaumann absorbers, circuit-simulated absorbers have the advantages of low profile and wide absorption bandwidth. Research achievements in this field have greatly promoted the development of stealth technology.

[0003] Foam sandwich composite structures are widely used in aerospace technology due to their advantages such as lightweight, high strength, high flexural stiffness, impact resistance, good energy absorption, and high design freedom. Therefore, incorporating circuit-simulated microwave absorbers with foam sandwich structures in a compatible design not only meets the mechanical requirements of lightweight, high specific strength, and high specific stiffness, but also satisfies the electrical performance requirements of broadband absorption. Thus, the design architecture of panel layer-frequency selective surface layer-foam layer-carbon fiber backing layer provides a fundamental research approach for foam sandwich microwave absorbing composite materials.

[0004] Since the thickness-direction strength and modulus of a sandwich structure are determined by the core material, the interfacial bonding between the face and core materials of foam sandwich composites is weak and the compressive strength is low. In the past decade, a series of core reinforcement measures, such as Z-pin reinforcement, fiber stitching reinforcement, and fiber web reinforcement, have been proposed, and related achievements have been widely applied in engineering fields such as bridge decks, road underlayment, and crash barriers. However, in the field of wave-absorbing materials, the impact of the reinforcement measures on the wave-absorbing performance of the material must also be considered. Therefore, the problem to be solved by this invention is to design wave-absorbing materials that are compatible with this technology and achieve broadband wave-absorbing performance while ensuring high mechanical strength in both the transverse and longitudinal directions. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a foam sandwich structure that combines broadband electromagnetic absorption and lattice mechanical enhancement. Based on a typical lattice-enhanced architecture, a resistive film composite core material is designed to ensure broadband electromagnetic absorption performance.

[0006] The present invention is specifically implemented through the following technical solutions.

[0007] A foam sandwich structure combining broadband electromagnetic absorption and lattice mechanical enhancement comprises, from top to bottom, a wave-transparent panel (serving as a skin layer on top of the core material to improve the lateral mechanical strength of the absorbing material), a resistive film composite foam core material, and an electromagnetic wave reflecting backplate (serving at the bottom of the core material). The resistive film composite foam core material includes multiple resistive film composite foam core layers. Each resistive film composite foam core layer includes a foam layer and a resistive film bonded to the foam layer by an adhesive. The resistive film includes a wave-transparent composite material sheet and a resistive film layer. The resistive film layer is printed on the wave-transparent composite material sheet. The structure also includes an orthogonal lattice web, which is formed by periodically arranging grid units. Each grid unit is assembled by arranging grids along the x-direction and y-direction using an interlocking method.

[0008] An orthogonal lattice web surrounds the resistive film composite foam core material, and the orthogonal lattice web and the resistive film composite foam core material are integrally formed using a vacuum-assisted molding method. The orthogonal lattice web, combined with the resistive film layer and the foam layer, serves as a mechanical reinforcement component of the structural core material, while having a relatively low impact on the overall wave absorption performance of the structure.

[0009] Furthermore, the grid bar is composed of a multilayer transparent fiber reinforced resin matrix composite material with a relative permittivity of 4.1 and a dielectric loss angle of 0.025.

[0010] Furthermore, the grid unit period is 10-50mm, and the grid thickness is 0.2-3.0mm.

[0011] Furthermore, the wave-transparent panel is made of wave-transparent fiber-reinforced resin matrix composite material with a relative permittivity of 4.1 and a dielectric loss angle range of 0.025.

[0012] Furthermore, each of the resistive film layers is independently selected for its sheet resistance and geometry, and the shapes are all arranged in a periodic pattern.

[0013] Furthermore, the shape can be a square ring, a porous shape, or a continuous shape. Specifically: the resistive film layer is formed by periodically arranging square ring resistive films; or: the resistive film layer contains porous structures arranged periodically; or: the resistive film layer is composed of a continuous resistive film.

[0014] Furthermore, the thickness of the wave-transparent composite material sheet is 0.05–0.2 mm, the relative permittivity is 4.1, and the dielectric loss angle is 0.025.

[0015] Furthermore, the foam layer includes PVC and PMI foam, with a relative permittivity of 1.02-1.1 and a dielectric loss angle of 0.001-0.01.

[0016] Furthermore, the electromagnetic wave reflector backplate is made of carbon fiber composite material with a thickness of 0.9-1mm.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The foam sandwich structure provided by this invention combines broadband electromagnetic absorption and lattice mechanical enhancement. By introducing orthogonal lattice webs into the foam core material, the basic mechanical properties of the absorbing material in both the transverse and longitudinal directions are guaranteed. Based on a typical lattice-reinforced architecture, a resistive film composite core material is designed to further ensure broadband electromagnetic absorption performance. Specifically:

[0019] The orthogonal lattice web is composed of periodically arranged grid units, each grid unit being arranged along the x- and y- directions and assembled using an interlocking method; the resistive film composite foam core material includes multiple resistive film composite foam core layers, each of which includes a foam layer and a resistive film composited on the foam layer. The resistive film includes a wave-transparent composite material sheet and a resistive film layer, with the resistive film layer printed on the wave-transparent composite material sheet; the orthogonal lattice web serves as a mechanical reinforcement component of the structural core material, while having a relatively low impact on the overall structure's wave absorption performance. By adjusting the number of layers of the resistive film composite foam core material, the sheet resistance of the resistive film layer, and its shape, the structure of this invention possesses broadband electromagnetic absorption performance. Attached Figure Description

[0020] To more clearly illustrate the embodiments and design schemes of the present invention, the accompanying drawings required for this embodiment will be briefly described below. The drawings described below are only some embodiments of the present invention, and other drawings can be obtained based on these drawings.

[0021] Figure 1 A schematic diagram of a unit structure of a foam sandwich structure that combines broadband electromagnetic absorption and lattice mechanical enhancement, provided in an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the resistive film composite foam core material structure in a unit structure of the foam sandwich structure that combines broadband electromagnetic absorption and lattice mechanical enhancement provided in Embodiment 1 of the present invention.

[0023] Figure 3 The diagram shows the lateral (x-direction) and longitudinal (y-direction) grid geometry of the 6×6 unit structure in the foam sandwich structure that combines broadband electromagnetic absorption and lattice mechanical enhancement provided by the present invention.

[0024] Figure 4 This is a geometrical schematic diagram of a square ring-shaped resistive film, one of the unit structures in the foam sandwich structure that combines broadband electromagnetic absorption and lattice mechanical enhancement provided by the present invention.

[0025] Figure 5This is a geometrical schematic diagram of a porous resistive film in a unit structure of a foam sandwich structure that combines broadband electromagnetic absorption and lattice mechanical enhancement provided by the present invention.

[0026] Figure 6 This is a geometrical schematic diagram of a continuous resistive film in a unit structure of a foam sandwich structure that combines broadband electromagnetic absorption and lattice mechanical enhancement, as provided in an embodiment of the present invention.

[0027] Figure 7 This is a schematic diagram of the resistive film composite foam core material structure in a unit structure of the foam sandwich structure that combines broadband electromagnetic absorption and lattice mechanical enhancement provided in Embodiment 3 of the present invention.

[0028] Figure 8 This is the reflectance curve of Embodiment 1 of the present invention.

[0029] Figure 9 This is the reflectance curve of Embodiment 2 of the present invention.

[0030] Figure 10 This is the reflectance curve of Embodiment 3 of the present invention.

[0031] Figure 11 This is the reflectance curve of Embodiment 4 of the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. Wave-transparent panel; 2. Orthogonal lattice web; 3. Electromagnetic wave reflecting backplate; 4. Resistive film composite foam core material; 40. First resistive film composite foam core layer; 41. Second resistive film composite foam core layer; 42. Third resistive film composite foam core layer; 400. First resistive film layer; 410. Second resistive film layer; 420. Third resistive film layer; 430. Fourth resistive film layer; 440. Fifth resistive film layer; 401. First foam layer; 411. Second foam layer; 421. Third foam layer; 431. Fourth foam layer; 441. Fifth foam layer. Detailed Implementation

[0034] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0035] Example 1

[0036] like Figure 1 and Figure 2As shown, the foam sandwich structure in Example 1, which combines broadband electromagnetic absorption and lattice mechanical enhancement, includes a wave-transparent panel 1 made of glass fiber reinforced epoxy resin, an orthogonal lattice web 2, an electromagnetic wave reflecting backplate 3 made of carbon fiber reinforced epoxy resin, and a resistive film composite foam core material 4.

[0037] Among them, the thickness of the wave-transparent panel 1 is 1.1 mm, the thickness of the electromagnetic wave reflecting back plate 3 is 0.9 mm, and the thickness of the orthogonal lattice web plate 2 is 0.56 mm.

[0038] The relative permittivity of the transparent panel 1 is 4.1, and the dielectric loss angle is 0.025.

[0039] The resistive film composite foam core material 4 includes a first resistive film composite foam core layer 40, a second resistive film composite foam core layer 41, and a third resistive film composite foam core layer 42. The first resistive film composite foam core layer 40 includes a first foam layer 401 and a first resistive film bonded to the first foam layer 401 by an adhesive. The first resistive film includes a first wave-transparent composite material sheet and a first resistive film layer 400, with the first resistive film layer 400 printed on the first wave-transparent composite material sheet. The second resistive film composite foam core layer 41 includes a second foam layer 411 and a second resistive film bonded to the second foam layer 411 by an adhesive. The second resistive film includes a second wave-transparent composite material sheet and a second resistive film layer 410, with the second resistive film layer 410 printed on the second wave-transparent composite material sheet. The third resistive film composite foam core layer 42 includes a third foam layer 421 and a third resistive film sheet bonded to the third foam layer 421 by an adhesive. The third resistive film sheet includes a third wave-transparent composite material sheet and a third resistive film layer 420, wherein the third resistive film layer 420 is printed on the third wave-transparent composite material sheet. The first resistive film layer 400, the second resistive film layer 410, and the third resistive film layer 420 have different sheet resistance values ​​and geometric shapes and are arranged in a periodic pattern. Specifically, in this embodiment, the foam sandwich structure with broadband electromagnetic absorption and lattice mechanical enhancement includes three carbon-based resistive films with a 3×3 period in one unit structure. The first resistive film layer 400 and the second resistive film layer 410 are in a square ring shape (e.g., Figure 4 As shown), the sheet resistance values ​​are 393 and 225 Ohm / sq, respectively; the third resistive film layer 420 has a porous shape (as shown). Figure 5 As shown in the figure, the sheet resistance is 86 Ohm / sq.

[0040] The first foam layer 401, the second foam layer 411, and the third foam layer 421 are all PMI foams, with thicknesses of 3 mm, 5.6 mm, and 5.8 mm, respectively. The relative permittivity is 1.02-1.1, and the dielectric loss angle is 0.001-0.01. It should be noted that the dielectric constant and loss angle of the foam are unstable; therefore, only basic ranges are given here.

[0041] The thickness of the first, second, and third transparent composite material sheets is 0.05–0.2 mm, the relative permittivity is 4.1, and the dielectric loss angle is 0.025°.

[0042] like Figure 3 As shown, the orthogonal lattice web 2 in the 6×6 unit structure has dimensions of 183.4mm×14.7mm×0.56mm. It is assembled from grids in the x-direction and y-direction by an interlocking method. The interlocking period corresponds to the unit period of the lattice-reinforced electromagnetic absorbing sandwich structure, with a dimension of 30mm. The slotting / interlocking depth corresponds to half the thickness of the core material of the lattice-reinforced electromagnetic absorbing composite structure, with a dimension of 7.4mm and a slot width of 0.6mm. The grids are made of multilayer transparent fiber-reinforced resin matrix composite material with a relative permittivity of 4.1 and a dielectric loss angle of 0.025°.

[0043] like Figure 8 As shown, the foam sandwich structure in Example 1, which combines broadband electromagnetic absorption and lattice mechanical enhancement, achieved broadband electromagnetic absorption performance of less than -10dB in the 2.3-18GHz frequency band.

[0044] Example 2

[0045] The foam sandwich structure, which combines broadband electromagnetic absorption and lattice mechanical enhancement, comprises a three-layer carbon-based resistive film with a 2×2 period in one unit structure.

[0046] In Example 2, the orthogonal lattice web portion 2 of the 6×6 unit structure has dimensions of 123.6mm×14.7mm×0.56mm. It is assembled by interlocking the grid bars in the x-direction and y-direction. The interlocking period corresponds to the unit period of the lattice-enhanced electromagnetic wave absorbing sandwich structure, with a size of 20mm. The slotting / interlocking depth corresponds to half the core material thickness of the lattice-enhanced electromagnetic wave absorbing composite structure, with a size of 7.4mm and a slot width of 0.6mm.

[0047] The remaining geometric parameters in Example 2 are the same as those listed in Example 1.

[0048] like Figure 9 As shown, the lattice-enhanced electromagnetic absorption composite structure in Embodiment 2 achieved broadband electromagnetic absorption performance of less than -10dB in the 2.2-17.8GHz frequency band.

[0049] Example 3

[0050] like Figure 1 and Figure 7As shown, the foam sandwich structure in Example 3, which combines broadband electromagnetic absorption and lattice mechanical enhancement, includes a wave-transparent panel 1 made of glass fiber reinforced epoxy resin, an orthogonal lattice web 2, and an electromagnetic wave reflecting backplate 3 made of carbon fiber reinforced epoxy resin and resistive film composite foam core material 4. The wave-transparent panel 1 has a thickness of 0.6 mm, the electromagnetic wave reflecting backplate 3 has a thickness of 0.9 mm, and the orthogonal lattice web 2 has a thickness of 0.6 mm. The relative permittivity of the wave-transparent panel 1 is 4.1, and the dielectric loss angle is 0.025°.

[0051] The resistive film composite foam core material 4 includes a first resistive film composite foam core layer 40, a second resistive film composite foam core layer 41, and a third resistive film composite foam core layer 42. The first resistive film composite foam core layer 40 includes a first foam layer 401 and a first resistive film laminated on the first foam layer 401. The first resistive film includes a first wave-transparent composite material sheet and a first resistive film layer 400, with the first resistive film layer 400 printed on the first wave-transparent composite material sheet. The second resistive film composite foam core layer 41 includes a second foam layer 411 and a second resistive film laminated on the second foam layer 411. The second resistive film includes a second wave-transparent composite material sheet and a second resistive film layer 410, with the second resistive film layer 410 printed on the second wave-transparent composite material sheet. The third resistive film composite foam core layer 42 includes a third foam layer 421 and a third resistive film laminated on the third foam layer 421. The third resistive film includes a third wave-transparent composite material sheet and a third resistive film layer 420, with the third resistive film layer 420 printed on the third wave-transparent composite material sheet. The fourth resistive film composite foam core layer 43 includes a fourth foam layer 431 and a fourth resistive film composited on the fourth foam layer 431. The fourth resistive film includes a fourth wave-transparent composite material sheet and a fourth resistive film layer 430, wherein the fourth resistive film layer 430 is printed on the fourth wave-transparent composite material sheet. The fifth resistive film composite foam core layer 44 includes a fifth foam layer 441 and a fifth resistive film composited on the fifth foam layer 441. The fifth resistive film includes a fifth wave-transparent composite material sheet and a fifth resistive film layer 440, wherein the fifth resistive film layer 440 is printed on the fifth wave-transparent composite material sheet.

[0052] The foam thicknesses in the first foam layer 401, the second foam layer 411, the third foam layer 421, the fourth foam layer 431, and the fifth foam layer 441 are 3.2 mm, 5.4 mm, 4.1 mm, 4.1 mm, and 5.8 mm, respectively. The relative permittivity is 1.02-1.2, and the dielectric loss angle is 0.001-0.01.

[0053] The thickness of the first, second, and third transparent composite material sheets is 0.05–0.2 mm, the relative permittivity is 4.1, and the dielectric loss angle is 0.025°.

[0054] In the 6×6 unit structure, the orthogonal lattice web 2 has dimensions of 183.4mm×22.8mm×0.56mm. It is constructed by interlocking gratings in the x- and y-directions. The interlocking period corresponds to the period of the foam sandwich structure unit, which combines broadband electromagnetic absorption and lattice mechanical reinforcement, and has a size of 30mm. The slot / interlocking depth corresponds to half the thickness of the core material of the lattice-reinforced electromagnetic absorbing sandwich structure, with a size of 11.4mm and a slot width of 0.6mm. The gratings are made of multilayer fiber-reinforced resin matrix composite material with a relative permittivity of 4.1 and a dielectric loss angle of 0.025°.

[0055] The lattice-enhanced electromagnetic absorbing sandwich structure comprises a unit structure of five carbon-based resistive films with a 3×3 period, wherein the first resistive film layer 400, the second resistive film layer 410, and the third resistive film layer 420 are in the shape of a square ring (shape as shown in the figure). Figure 4 As shown), the sheet resistance values ​​are 420, 265, and 275 Ohm / sq, respectively; the fourth resistive film layer 430 and the fifth resistive film layer 440 have continuous shapes (shape as shown). Figure 6 As shown in the figure, the sheet resistance values ​​are 321 and 184 Ohm / sq, respectively.

[0056] like Figure 10 As shown, the foam sandwich structure in Embodiment 3, which combines broadband electromagnetic absorption and lattice mechanical enhancement, achieved a broadband electromagnetic absorption performance of less than -15dB in the 2.2-17.4GHz frequency band.

[0057] Example 4

[0058] The foam sandwich structure, which combines broadband electromagnetic absorption and lattice mechanical enhancement, comprises a five-layer carbon-based resistive film with a 2×2 period in a single unit structure.

[0059] In Example 4, the orthogonal lattice web portion 2 of the 6×6 unit structure has dimensions of 123.6mm×22.8mm×0.56mm. It is assembled by interlocking the grid bars in the x-direction and y-direction. The interlocking period corresponds to the unit period of the lattice-enhanced electromagnetic wave absorbing composite structure, with a size of 20mm. The slotting / interlocking depth corresponds to half the core material thickness of the lattice-enhanced electromagnetic wave absorbing composite structure, with a size of 11.4mm and a slot width of 0.6mm.

[0060] The remaining geometric parameters in Example 4 are the same as those listed in Example 3.

[0061] like Figure 11 As shown, the foam sandwich structure in Embodiment 4, which combines broadband electromagnetic absorption and lattice mechanical enhancement, achieved a broadband electromagnetic absorption performance of less than -15dB in the 2.3-17.5GHz frequency band.

[0062] It should be understood that the material of the above-described structure is merely one embodiment of the present invention, and the specific choice should be determined according to the actual situation. The present invention does not impose any limitations on this. It should also be understood that the above-described structural dimensions are merely one embodiment, provided as an example, and the specific dimensional variations should be determined according to the actual situation. The present invention does not impose any limitations on this.

[0063] In summary, the foam sandwich structure provided by this invention, which combines broadband electromagnetic absorption and lattice mechanical reinforcement, achieves broadband electromagnetic absorption performance by incorporating a multilayer resistive film within a lightweight sandwich composite structure. Simultaneously, the structure contains a lattice-type mechanical reinforcement component, enabling the absorbing material to achieve high mechanical strength in the longitudinal direction. Therefore, by employing the integrated method of lattice reinforcement component and loss material as described in this patent, the absorbing material simultaneously possesses the multifunctionality of broadband electromagnetic absorption and high mechanical strength, making this design method promising for significant engineering applications.

[0064] The above-described embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any simple changes or equivalent substitutions of the technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention shall fall within the scope of protection of the present invention.

Claims

1. A foam sandwich structure with both broadband electromagnetic absorption and lattice mechanical reinforcement, characterized in that, From top to bottom, it includes wave-transparent panel (1), resistive film composite foam core material (4) and electromagnetic wave reflection backboard (3) in turn; the periphery of the resistive film composite foam core material (4) is covered with orthogonal lattice web (2), the orthogonal lattice web (2) is arranged by grid strip unit period, each grid strip unit is arranged along x direction and y direction and assembled by interlocking method; the orthogonal lattice web (2) and the resistive film composite foam core material (4) are integrally formed by vacuum assisted forming method; The resistance film composite foam core material (4) comprises a plurality of resistance film composite foam core layers, each of which comprises a foam layer and a resistance film sheet, the resistance film sheet comprising a wave-transparent composite material sheet and a resistance film layer, the wave-transparent composite material sheet being compounded on the foam layer, and the resistance film layer being printed on the wave-transparent composite material sheet; The square resistance value and geometric shape of each layer of the resistance film layer are independently selected; The resistance film layer is periodically arranged by square ring resistance film; Alternatively, the resistance film layer is periodically arranged by apertures; Alternatively, the resistance film layer is continuously formed by a resistance film; The grid strip is composed of a plurality of layers of wave-transparent fiber reinforced resin-based composite material, with a relative dielectric constant of 4.1 and a dielectric loss angle of 0.

025. The grid strip unit period is 10-50 mm, and the grid strip thickness is 0.2-3.0 mm. The wave-transparent panel (1) is composed of wave-transparent fiber reinforced resin-based composite material, with a relative dielectric constant of 4.1 and a dielectric loss angle of 0.

025.

2. The foam sandwich structure with broadband electromagnetic absorption and auxetic mechanical reinforcement of claim 1, wherein, The square resistance value of the resistance film layer is 86-420 Ohm / sq.

3. The foam sandwich structure with broadband electromagnetic absorption and auxetic mechanical reinforcement of claim 1, wherein, The thickness of the wave-transparent composite material sheet is 0.05-0.2 mm, the relative dielectric constant is 4.1, and the dielectric loss angle is 0.

025.

4. The foam sandwich structure with broadband electromagnetic absorption and auxetic mechanical reinforcement of claim 1, wherein, The foam layer is PVC or PMI foam, with a relative dielectric constant of 1.02-1.1 and a dielectric loss angle of 0.001-0.

01.

5. The foam sandwich structure with broadband electromagnetic absorption and auxetic mechanical reinforcement of claim 1, wherein, The electromagnetic wave reflection backboard (3) is composed of carbon fiber composite material, with a thickness of 0.9-1 mm.

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