A broadband wave-absorbing composite material laminate and a preparation method thereof

Abstract

The application belongs to the technical field of functional composite materials, and relates to a broadband wave-absorbing composite material layer plate and a preparation method thereof. The broadband wave-absorbing composite material layer plate is arranged from top to bottom as an FR4 wave-transparent plate, a high-frequency wave-absorbing layer, a medium-frequency wave-absorbing layer, a polarization conversion gradient metasurface, a low-frequency wave-absorbing layer and a reflective back plate. The polarization conversion gradient metasurface is loaded between the low-frequency and medium-frequency wave-absorbing layers of the wave-absorbing composite material layer plate, the polarization conversion gradient metasurface is used to generate abnormal reflection and abnormal refraction, the propagation path of electromagnetic waves in the layer plate is prolonged, loss is increased, the low-frequency absorption effect is improved, and the effective wave-absorbing bandwidth is widened. Compared with a conventional wave-absorbing composite material layer plate, the broadband wave-absorbing composite material layer plate has relatively high wave-absorbing efficiency under a certain design thickness. In particular, for decimeter radar waves with long wavelengths, the broadband wave-absorbing composite material layer plate can effectively reduce the matching design thickness of the layer plate electric structure, and has obvious low-frequency technical advantages.

Claims

1. A method for preparing a broadband microwave absorbing composite material laminate, characterized in that, include: Determine the thickness requirements of the high-frequency absorbing layer (2) and prepare the high-frequency absorbing layer (2); According to the thickness requirements of the intermediate frequency absorbing layer (3), the intermediate frequency absorbing layer (3) is prepared; According to the thickness requirements of the low-frequency absorbing layer (5), the low-frequency absorbing layer (5) is prepared; A polarization conversion gradient metasurface layer (4) was prepared by using a single-sided copper clad laminate, and indentations were engraved on the polarization conversion gradient metasurface layer (4). To assemble the laminate, first fix the polarization conversion gradient metasurface layer (4) onto the low-frequency absorbing layer (5), then fill the indentation on the polarization conversion gradient metasurface layer (4) with a solution, then bond the mid-frequency absorbing layer (3) onto the polarization conversion gradient metasurface layer (4), then bond the high-frequency absorbing layer (2) onto the mid-frequency absorbing layer (3), and then attach the FR4 wave-transparent plate (1) onto the high-frequency absorbing layer (2) to form a laminate. Place a weight on the laminate and leave it for a certain period of time to complete the preparation. The high-frequency absorbing layer (2) is prepared by: Carbonyl iron powder was stirred in a mixer for 4 hours and then ball-milled in a ball mill for 1 hour to obtain a high-frequency absorbent. Mix the epoxy resin and curing agent evenly according to the proportion, and add the absorbent to the room temperature curing epoxy resin containing the curing agent at a volume ratio of 1:5 and stir evenly to form a high-frequency absorbing coating with certain fluidity and viscosity. Apply a layer of high-frequency absorbing coating to the FR4 transparent plate (1) and cover it with a layer of glass fiber mesh cloth so that the glass fiber mesh cloth is completely adhered to the high-frequency absorbing coating. Wait for the epoxy resin to cure at room temperature. After the epoxy resin has cured, it is applied again by manual scraping and fiberglass mesh is laid on top, and then left to cure at room temperature. Determine the current thickness of the high-frequency absorbing layer (2). If the set thickness requirement is not met, repeat the operation of scraping the high-frequency absorbing coating and laying the glass fiber mesh until the set thickness is reached, and leave it for a certain period of time to wait for room temperature curing. The method for preparing the mid-frequency absorbing layer (3) includes: Carbonyl iron powder was stirred in a mixer for 6 hours and then ball-milled for 0.5 hours to obtain a medium-frequency absorber with relatively high flaky properties. Mix the epoxy resin and curing agent evenly according to the ratio, and dilute the epoxy resin with xylene-n-butanol at a ratio of 10%; mix the intermediate frequency absorber and the room temperature curing epoxy resin containing the curing agent evenly at a volume ratio of 1:4 to form a medium frequency absorbing coating with certain fluidity and viscosity. Apply a layer of medium-frequency absorbing coating to the cured high-frequency absorbing layer (2) and cover it with a layer of glass fiber mesh cloth so that the glass fiber mesh cloth is completely adhered to the medium-frequency absorbing coating. Wait for the epoxy resin to cure at room temperature. After the epoxy resin has cured, it is applied again by manual scraping and fiberglass mesh is laid on top, and then left to cure at room temperature. Determine the current thickness of the intermediate frequency absorbing layer (3). If the set thickness requirement is not met, repeat the operation of scraping the intermediate frequency absorbing coating and laying the glass fiber mesh until the set thickness is reached, and leave it for a certain period of time to wait for room temperature curing.

2. The method for preparing a broadband absorbing composite material layer as described in claim 1, characterized in that, The polarization conversion gradient metasurface layer (4) is prepared as follows: the thickness of the commercially available single-sided copper clad laminate FR4 is 0.5 mm, and the thickness of the copper film covering it is 35 μm; the dimensions of the polarization conversion gradient metasurface layer (4) are as follows: period 10 mm, bottom FR4 thickness 0.5 mm, outer diameter of the ring 9.2 mm, inner diameter 8.4 mm, ring notch width 0.82 mm, tangent width 0.4 mm, and length 8.4 mm; Then, the outer shape of the ring-tangent unit is first carved with a 1.5mm diameter carving tool, and then the internal structure of the ring-tangent unit is carved with a 0.8mm carving tool.

3. The method for preparing a broadband absorbing composite material laminate as described in claim 1, characterized in that, The method for preparing the low-frequency absorbing layer (5) includes: After grinding iron-silicon-aluminum powder with a mixer for 9 hours, a flake-shaped low-frequency absorbent was obtained. Mix the epoxy resin and curing agent evenly according to the ratio, and dilute the epoxy resin with xylene-n-butanol at a ratio of 15%; mix the low-frequency absorber with the room-temperature curing epoxy resin containing the curing agent at a volume ratio of 1:3 to form a low-frequency absorbing coating with a certain fluidity and viscosity. A layer of low-frequency absorbing coating is applied to a carbon fiber composite board and covered with a layer of fiberglass mesh, so that the fiberglass mesh is completely adhered to the medium-frequency absorbing coating. The epoxy resin is then allowed to cure at room temperature. After the epoxy resin has cured, it is applied again by manual scraping and fiberglass mesh is laid on top, and then left to cure at room temperature. Determine the current thickness of the low-frequency absorbing layer (5). If the set thickness requirement is not met, repeat the operation of scraping the low-frequency absorbing coating and laying the glass fiber mesh until the set thickness is reached, and leave it for a certain period of time to wait for room temperature curing.

4. The method for preparing a broadband absorbing composite material laminate as described in claim 1, characterized in that, The specific assembly method of the laminate includes: A layer of epoxy resin containing curing agent is manually scraped onto the cured low-frequency absorbing layer (5) plate. The polarization conversion gradient metasurface layer (4) is then covered onto the top of the low-frequency absorbing layer (5) plate and left to cure. The degree of curing is determined by the polarization conversion gradient metasurface layer (4) being fixed on the low-frequency absorbing layer (5). Pour the epoxy resin-curing agent-acetone solution onto the patterned polarization conversion gradient metasurface layer (4). Use the casting method and slight manual scraping to cover all the metamaterial patterns with epoxy resin solution, filling the engraved grooves. After the acetone evaporates, the next step of bonding can be carried out. A solvent-free epoxy resin was manually coated onto the polarization conversion gradient metasurface layer (4) whose grooves had been filled, and the mid-frequency absorbing layer (3), the high-frequency absorbing layer (2) and the wave-transparent panel were placed on the polarization conversion gradient metasurface layer (4). After applying the adhesive, place appropriate weights on the laminate to ensure a strong bond. The epoxy resin layer will cure in 1-2 days at room temperature.

5. A broadband absorbing composite material laminate, comprising the method described in any one of claims 1-4, characterized in that: It includes a high-frequency absorbing layer (2), a mid-frequency absorbing layer (3), a low-frequency absorbing layer (5), a polarization conversion gradient metasurface layer (4), and an FR4 transparent plate (1); the low-frequency absorbing layer (5) is bonded to the bottom of the polarization conversion gradient metasurface layer (4), the mid-frequency absorbing layer (3) is bonded to the top of the polarization conversion gradient metasurface layer (4), the high-frequency absorbing layer (2) is bonded to the mid-frequency absorbing layer (3), the FR4 transparent plate (1) is bonded to the high-frequency absorbing layer (2), and glass fiber mesh is laid on the high-frequency absorbing layer (2), the mid-frequency absorbing layer (3), the low-frequency absorbing layer (5), and the FR4 transparent plate (1). The bottom of the low-frequency absorbing layer (5) is bonded to a reflective backplate (6).

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