Adjustable and controllable paper shearing and folding electromagnetic wave absorbing structure

Abstract

The invention discloses an adjustable and controllable paper cutting and folding electromagnetic wave absorbing structure. The wave absorbing structure comprises an upper-layer impedance type fractal paper cutting structure, an impedance type paper folding structure, a lower-layer impedance type fractal paper cutting structure and a reflecting back plate which are sequentially connected from top to bottom. The upper layer impedance type fractal paper-cut structure and the lower layer impedance type fractal paper-cut structure are the same; the upper-layer impedance type fractal paper-cut structure comprises an upper-layer fractal paper-cut structure and a first impedance layer attached to the top surface of the upper-layer fractal paper-cut structure; the bottom surface of the lower-layer fractal paper-cut structure is connected with the top surface of the reflecting back plate; the impedance type paper folding structures are periodically arranged in the transverse direction and the longitudinal direction, and each impedance type paper folding structure comprises a paper folding structure and a second impedance layer attached to the inner side wall face of the paper folding structure; the paper folding structure is driven to be unfolded or folded through antisymmetric cooperative movement of the upper-layer impedance type fractal paper-cut structure and the lower-layer impedance type fractal paper-cut structure. According to the electromagnetic wave-absorbing structure, flexible curved surface conformal, three-dimensional negative Poisson's ratio deformation and bistable effects can be realized, and the electromagnetic wave-absorbing frequency band is expanded.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorption technology, specifically relating to an adjustable electromagnetic wave absorption structure for paper cutting and folding. Background Technology

[0002] As information warfare continues to evolve and the electromagnetic environment on the battlefield becomes increasingly complex, higher demands are being placed on the radar stealth capabilities of high-end defense equipment. As an important technological means to enhance the survivability of weapons and equipment, electromagnetic stealth technology has become one of the key development directions.

[0003] Currently, common electromagnetic absorbing materials and structures have significant shortcomings in meeting broadband stealth requirements, and mostly operate under specific morphological conditions. Their performance response is limited by the physical properties of the materials themselves, making it difficult to adapt to complex and variable electromagnetic environments and equipment with different shape requirements. To overcome the performance bottleneck of traditional absorbing structures, some research has introduced reconfigurable paper-cut or origami structures as driving devices, developing superstructures with adjustable stealth performance and variable configurations. Although such solutions have achieved initial applications, most suffer from limited frequency coverage, reliance on external drives to maintain stability, and limited mechanical properties, which greatly restricts their practical application in complex electromagnetic environments. Currently, commonly used control methods are usually based on fractal paper-cut structures, Mirua origami structures, and Kresling origami structures. However, single-configuration control has a narrow absorption bandwidth and cannot simultaneously meet the requirements of in-plane extension and out-of-plane load-bearing.

[0004] Therefore, there is an urgent need to design an adjustable electromagnetic absorbing structure that can achieve multi-band electromagnetic absorbing performance while also possessing excellent mechanical properties such as flexible conformal surface, bistable characteristics, and adjustable load-bearing capacity, thereby expanding the application scenarios of the structure and meeting the radar stealth requirements of different equipment. Summary of the Invention

[0005] This invention provides an adjustable electromagnetic wave absorbing structure for paper cutting and folding. This electromagnetic wave absorbing structure can achieve flexible curved surface conformal, three-dimensional negative Poisson's ratio deformation and bistable effect, and expand the electromagnetic wave absorbing frequency band.

[0006] To achieve the above objectives, the present invention adopts the following specific technical solution:

[0007] An adjustable paper-cutting and origami electromagnetic wave-absorbing structure, comprising, from top to bottom, an upper impedance-type fractal paper-cutting structure, an impedance-type origami structure, a lower impedance-type fractal paper-cutting structure, and a reflective backplate connected in sequence.

[0008] The upper impedance-type fractal paper-cutting structure is periodically arranged in the horizontal and vertical directions, and includes an upper fractal paper-cutting structure and a first impedance layer attached to the top surface of the upper fractal paper-cutting structure.

[0009] The lower impedance-type fractal paper-cutting structure adopts the same structure as the upper impedance-type fractal paper-cutting structure, and includes a lower fractal paper-cutting structure and a third impedance layer attached to the top surface of the lower fractal paper-cutting structure; the bottom surface of the lower fractal paper-cutting structure is connected to the top surface of the reflective back plate.

[0010] The impedance-type origami structure is arranged periodically in the horizontal and vertical directions, and includes an origami structure and a second impedance layer attached to the inner sidewall of the origami structure; the top surface of the origami structure is connected to the bottom surface of the upper fractal paper-cutting structure, and the bottom surface of the origami structure is connected to the top surface of the lower fractal paper-cutting structure.

[0011] The wave-absorbing structure drives the unfolding or folding of the origami structure through the anti-symmetrical coordinated motion of the upper impedance-type fractal paper-cutting structure and the lower impedance-type fractal paper-cutting structure.

[0012] Furthermore, the upper fractal paper-cutting structure is a kirigami paper-cutting structure;

[0013] The upper fractal paper-cutting structure has square paper-cutting structural units, and adjacent paper-cutting structural units are connected by flexible hinges.

[0014] The first impedance layer is a square impedance control sheet, which is centrally attached to the top surface of each paper-cutting structural unit.

[0015] Furthermore, the paper-cutting structural unit has a side length of 15-25mm and is made of polyurethane elastic colloid through a lamination process. The paper-cutting structural unit is obtained by curing the polyurethane elastic colloid in a lamination mold.

[0016] Furthermore, the lamination mold is made using 3D printing.

[0017] Furthermore, the first impedance layer is prepared by printing conductive graphite, carbon nanotubes, silver or copper materials onto the first impedance layer substrate using inkjet printing, screen printing, dip-dip or electroplating processes.

[0018] The first impedance layer substrate is one or more of PI film, PEN film, FR4 plate or F4B plate, and the thickness of the first impedance layer substrate is 0.025 to 0.1 mm.

[0019] The surface resistivity of the first impedance layer is 460–540 Ω / sq; the ratio of the side length of the first impedance layer to the side length of the paper-cutting structural unit is 0.5–0.7.

[0020] Furthermore, adjacent origami structures are chirally arranged; the origami structure includes origami structure units that correspond one-to-one with the paper-cutting structure units along the vertical direction; the origami structure unit consists of an upper panel, four side panels, and a lower panel; the upper panel and the lower panel are both square in shape; the four side panels are distributed circumferentially, and each side panel is formed by two equilateral right-angled triangle plates joined together; adjacent side panels are separated from each other.

[0021] Furthermore, the second impedance layer is a triangular impedance control sheet, in which conductive graphite, carbon nanotubes, silver or copper materials are centered on the inner surface of each equilateral right-angled triangle plate by inkjet printing, screen printing, dip-dip or electroplating processes.

[0022] Furthermore, the upper panel, the equilateral right-angled triangular plate, and the lower panel are all prepared from a PET-PP-PET three-layer composite film through a double-sided laser cutting process, with the cut portion retaining only the connection state of a single PET layer; the PET-PP-PET three-layer composite film is prepared using a cold lamination process; the PET film layer is attached with an adhesive layer.

[0023] Furthermore, the thickness of the PET film layer is 0.03–0.07 mm; the thickness of the PP film layer is 0.1–0.2 mm.

[0024] The ratio of the length of the right-angled side of the second impedance layer to the length of the right-angled side of the equilateral right-angled triangle plate is 0.8 to 0.95; the surface resistivity of the second impedance layer is 150 to 250 Ω / sq.

[0025] Furthermore, the reflective backplate is made of metal or carbon fiber reinforced composite material, and its thickness is much greater than the skin depth of the material.

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0027] 1. By using a flexible fractal paper-cutting structure as the driving component, the electromagnetic wave absorbing structure can achieve large-scale deformation in the in-plane direction and a certain degree of surface conformal capability. Compared with traditional wave absorbing structures, it has a wider range of application scenarios.

[0028] 2. By introducing a paper-cutting coupling design, the structure possesses bistable and adjustable load-bearing characteristics. Under external load excitation, the structure can achieve negative Poisson's ratio deformation from two-dimensional plane to three-dimensional space, and does not require continuous external excitation to maintain the configuration. By switching the configuration, the out-of-plane load-bearing capacity can be adjusted, enhancing the multi-functional integrated characteristics of the structure.

[0029] 3. By utilizing the electromagnetic absorption characteristics of multi-layer frequency selective surface and impedance-type grid structure, and optimizing the electromagnetic absorption characteristics of the structure under different states, the effect of switching between low-width and high-width absorption frequency bands can be achieved, effectively enhancing the adjustable electromagnetic absorption performance of the structure.

[0030] In summary, the adjustable electromagnetic absorbing structure based on paper cutting and folding coupling design provided by this invention has high multifunctionality and integration, strong designability, and adjustable ultra-wideband electromagnetic absorbing frequency band; it has broad application prospects in the field of radar stealth. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the adjustable electromagnetic wave absorption structure for paper cutting and folding according to the present invention;

[0032] Figure 2 This is a schematic diagram of the impedance layer distribution of the adjustable paper-cutting and folding electromagnetic wave-absorbing structure of the present invention;

[0033] Figure 3 The structural parameters of the adjustable paper-cutting and origami electromagnetic wave absorbing structure of the present invention are as follows: (a) is an impedance-type fractal paper-cutting structure, (b) is an impedance-type origami structure unit, and (c) is a Kresling origami structure side panel.

[0034] Figure 4 This is a schematic diagram of the simulation optimization design results of the adjustable paper-cutting and folding electromagnetic wave absorbing structure of the present invention;

[0035] Figure 5 This is a schematic diagram of the experimental test results of the adjustable paper-cutting and folding electromagnetic wave absorption structure of the present invention;

[0036] Figure 6 The energy loss distribution diagrams for the impedance control plate of the adjustable paper-cutting electromagnetic wave absorption structure of this invention are shown in two steady states and one self-locking state, respectively, at electromagnetic wave frequencies of 4GHz, 9GHz, and 13GHz. (a) Electromagnetic wave frequency is 4GHz, (b) Electromagnetic wave frequency is 9GHz, and (c) Electromagnetic wave frequency is 13GHz.

[0037] Among them, 10-upper layer impedance-type paper-cutting structure, 11-first impedance layer, 12-upper layer fractal paper-cutting structure, 20-impedance-type folding structure, 21-upper end panel, 22-side panel, 23-lower end panel, 24-second impedance layer, 30-lower layer impedance-type paper-cutting structure, 31-third impedance layer, 32-lower layer fractal paper-cutting structure, 40-reflective back plate. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This invention provides an adjustable paper-cutting and origami electromagnetic absorbing structure. This adjustable electromagnetic absorbing structure achieves changes in electromagnetic performance by altering its own structural form. It couples a high-extensibility fractal paper-cutting structure and a bistable Kresling origami structure as a driving component. Through parameter design, the driving component achieves bistable switching from a two-dimensional plane to a three-dimensional space. It possesses high in-plane extensibility and adjustable out-of-plane load-bearing capacity, and broadens the electromagnetic absorbing frequency band, thus expanding the practical application scenarios of the adjustable absorbing structure.

[0040] Figure 1 This is a schematic diagram of an adjustable paper-cutting and folding electromagnetic wave absorbing structure provided in an embodiment of the present invention. The adjustable paper-cutting and folding electromagnetic wave absorbing structure specifically includes, from top to bottom, an upper impedance-type fractal paper-cutting structure 10, an impedance-type folding structure 20, a lower impedance-type fractal paper-cutting structure 30, and a reflective backplate 40, all connected sequentially. The impedance-type folding structure 20 is located between the upper impedance-type fractal paper-cutting structure 10 and the lower impedance-type fractal paper-cutting structure 30, and is used to achieve lifting and lowering motion. The upper impedance-type fractal paper-cutting structure 10 and the lower impedance-type fractal paper-cutting structure 30 are arranged in an anti-symmetrical manner. This wave absorbing structure drives the folding structure to unfold or fold through the anti-symmetrical coordinated motion of the upper and lower impedance-type fractal paper-cutting structures.

[0041] refer to Figure 2 The upper impedance-type fractal paper-cutting structure 10 is periodically arranged in the horizontal and vertical directions, and includes a first impedance layer 11 and an upper fractal paper-cutting structure 12. The first impedance layer is centrally attached to the top surface of the upper fractal paper-cutting structure 12. The upper fractal paper-cutting structure can be a kirigami paper-cutting structure, made of soft material, and has in-plane negative Poisson's ratio deformation characteristics; the origami structure is a Kresling origami configuration, made of multi-layer thin film double-sided laser cutting, and has bistable characteristics. The lower impedance-type fractal paper-cutting structure 30 adopts the same structure as the upper impedance-type fractal paper-cutting structure 10, and is arranged anti-symmetrically with the upper impedance-type fractal paper-cutting structure 10, and includes a third impedance layer 31 and a lower fractal paper-cutting structure 32; the third impedance layer is centrally attached to the top surface of the lower fractal paper-cutting structure 32. The bottom surface of the lower fractal paper-cutting structure 32 is connected to the top surface of the reflective backplate 40. The fractal paper-cutting structure is made of lossless material; the first impedance layer and the third impedance layer are impedance-type electromagnetic loss materials, which are uniformly and centrally attached to the top surface of each corresponding paper-cutting structural unit.

[0042] refer to Figure 2 The impedance-type origami structures are arranged periodically along the horizontal and vertical directions, with adjacent origami structures arranged chirally. Each impedance-type origami structure includes a Kresling origami structure 21 and a second impedance layer 24. The origami structure 21 can be a Kresling origami structure. The second impedance layer is centrally attached to the inner sidewall of the origami structure. The top surface of the origami structure 21 is connected to the bottom surface of the upper fractal paper-cutting structure 12, and the bottom surface of the origami structure 21 is connected to the top surface of the lower fractal paper-cutting structure 32. The origami structure includes origami structure units that correspond one-to-one with the paper-cutting structure units along the vertical direction. The origami structure unit consists of an upper panel 21, four side panels 22, and a lower panel 23. The upper and lower panels 21 and 23 are square and arranged opposite each other. The four side panels 22 are distributed circumferentially, forming the four sides of a square. Adjacent side panels are not connected and are separated from each other. Each side panel 22 is formed by two equilateral right-angled triangles joined together and connected to both the upper and lower panels 21 and 23 respectively. The two equilateral right-angled triangles forming the same side panel 22 are connected by valley folds, while the equilateral right-angled triangles of different side panels 22 are separated. The origami structure is made of a thin-walled material, and the upper, side, and lower surfaces are all lossless materials. Adjacent origami structures follow a chiral arrangement. The second impedance layer is an impedance-type electromagnetic loss material, specifically a triangular impedance control plate, uniformly and centrally attached to the inner wall of each origami structure.

[0043] refer to Figure 1 As shown, the in-plane dimensions of the reflective backplate 40 are consistent with the in-plane dimensions of the upper impedance-type fractal paper-cutting structure 10 and the lower impedance-type fractal paper-cutting structure 30.

[0044] Both the upper fractal paper-cutting structure 12 and the lower fractal paper-cutting structure 32 are made of thermoplastic polyurethane elastomer (TPU) material with a relative permittivity ranging from 4.16 to 4.24. Both structures consist of four square paper-cutting structural units. Adjacent units are connected by flexible hinges, the size of which is much smaller than the size of the unit. The side length p of each unit can be 15–25 mm, and the length a of the flexible hinge can be 0.8–1.2 mm. The units are made from polyurethane elastomer through a lamination process, where the polyurethane elastomer is cured in a lamination mold to obtain the paper-cutting structural unit. The lamination mold used in the fabrication process can be manufactured using 3D printing.

[0045] In the origami structure 30, the upper panel 21, side panel 22, and lower panel 23 are all made of a PET-PP-PET three-layer composite film through a double-sided laser cutting process. The cut portion retains only the connection state of a single PET layer, with a relative permittivity range of 3.2 to 3.7. The thickness of the PET film layer can be 0.03 mm to 0.07 mm; the thickness of the PP film layer can be 0.1 mm to 0.2 mm. The PET-PP-PET three-layer composite film is prepared by a cold lamination process. The PET film layer has an adhesive layer attached, which is prepared by cold lamination of the PET adhesive film and the PP film on both sides, with a thickness of 0.2 mm. A single PET film layer is retained as a connecting crease through double-sided laser cutting. The upper panel 21 and the side panel 22 are bonded together with instant adhesive, and the instant adhesive type can be Loctite 415.

[0046] The first impedance layer is a square impedance control sheet, and the second impedance layer is a triangular impedance control sheet. Both are fabricated by printing conductive graphite, carbon nanotubes, silver, or copper materials onto the impedance layer substrate using inkjet printing, screen printing, dip-coating, or electroplating processes. The reflective backplate is made of a high-conductivity material and can be made of metal or carbon fiber reinforced composite materials. Its thickness is much greater than the skin depth of the material, and its in-plane dimensions are consistent with the in-plane dimensions of the paper-cutting electromagnetic wave absorbing structure. The first impedance layer substrate can be one or more of PI film, PEN film, FR4 board, or F4B board. The thickness of the first impedance layer substrate is 0.025–0.1 mm; the surface resistivity of the first impedance layer is 460–540 Ω / sq; the ratio of the side length d of the first impedance layer to the side length p of the paper-cutting structural unit is 0.5–0.7. The ratio of the right-angled side length p of the second impedance layer to the right-angled side length b of the equilateral right-angled triangle is 0.8–0.95; the surface resistivity of the second impedance layer is 150–250 Ω / sq.

[0047] In this embodiment, the first impedance layer 11, the second impedance layer 22, and the third impedance layer 31 are prepared by screen printing, using conductive graphite as the impedance material. The first impedance layer 11 and the third impedance layer 31 have the same surface resistivity. The substrate used is a PI thin film with a thickness of 0.025 mm. The second impedance layer 24 is directly printed onto the side panel 22. The reflective backplate is an aluminum panel with a thickness of 2.5 mm.

[0048] A genetic algorithm was used to design the structural parameters of the tunable paper-cutting electromagnetic absorbing structure. The design goal was to achieve broadband electromagnetic absorption characteristics after the absorption bandwidths of the structure were superimposed in two steady-state and self-locking states. Specifically, the optimized structural parameters included: the period of the fractal paper-cutting structure unit, the resistance of the first and third impedance layers, the period of the first impedance layer, the resistance of the second impedance layer, and the side length of the right-angled side of the second impedance layer. Other structural parameters included the thickness of the fractal paper-cutting structure, the length of the flexible hinge, and the width of the flexible hinge. Figure 3 As shown.

[0049] In this embodiment, based on the optimization results of the genetic algorithm, the fractal paper-cutting structure unit has a period of 20mm and a thickness t of 2mm. The flexible hinge used in the fractal paper-cutting structure has a length of 1mm and a width of 1mm. The first and third impedance layers are square with a period of 13mm and a surface resistance of 495Ω / sq. The end face of the folded structure is square with a period of 20mm. The fully unfolded height of the structure is 20mm, and the folded height is 0mm. The second impedance layer is an equilateral right-angled triangle with a right-angled side length of 17.4mm and a surface resistance of 218Ω / sq.

[0050] The electromagnetic wave absorption structure of the adjustable paper-cutting and folding structure with the above structural parameters was analyzed using CST Microwave Studio simulation software to determine the electromagnetic wave absorption performance of this embodiment. In the numerical simulation model, the hinge modeling of the fractal paper-cutting structure was ignored because the flexible hinge of the fractal paper-cutting structure has little influence on the electromagnetic performance of the structure.

[0051] Figure 4 This diagram illustrates the reflectivity variation curves obtained from numerical simulation calculations when the electromagnetic wave is incident perpendicularly to the controllable paper-cutting electromagnetic absorbing structure, which operates in two steady-state states and one self-locking state. (Reference) Figure 4 When the fractal paper-cutting structure is in a contracted state and the origami structure is in a folded state, the structure is in a steady state, possessing a -10dB broadband absorption band of 3.1–13.1 GHz. When both the fractal paper-cutting and origami structures are in an unfolded state, the structure is in a steady state, possessing a -10dB absorption band of 5.5–14.5 GHz. When the fractal paper-cutting structure is in a contracted state and the origami structure is in an unfolded state, the structure is in a self-locking state, possessing -10dB absorption bands of 5.3–8.8 GHz and 11.9–13.9 GHz, with an absorption peak of -31.6dB. This embodiment exhibits broadband electromagnetic absorption in both steady states and one self-locking state. After switching from the first steady state to the second steady state, the structure's absorption frequency band shifts from low frequency to high frequency. By changing the structural configuration, active control of electromagnetic stealth performance can be achieved.

[0052] Figure 5The experimental test results for this embodiment are shown, and the test method is the bow-shaped frame method. (Reference) Figure 5 When the fractal paper-cutting structure is in a contracted state and the origami structure is in a folded state, it possesses a -10dB broadband absorption band of 2.7–13.5 GHz; when both the fractal paper-cutting and origami structures are in an unfolded state, it possesses a -10dB absorption band of 6.2–15.6 GHz. When the fractal paper-cutting structure is in a contracted state and the origami structure is in an unfolded state, it possesses -10dB absorption bands of 5.3–8.9 GHz and 11.5–13.9 GHz, with an absorption peak of -35dB. The absorption performance of the structure in the first steady state is slightly better than the simulation results, and the absorption frequency band in the second steady state is slightly shifted to a higher frequency compared to the simulation prediction results, which basically verifies the rationality of the structural design and the adjustable broadband electromagnetic absorption characteristics.

[0053] Figure 6 This diagram illustrates the electromagnetic energy loss distribution of the adjustable paper-cutting electromagnetic absorbing structure in this embodiment, under two steady-state conditions and one self-locking state, at electromagnetic wave frequencies of 4GHz, 9GHz, and 13GHz. The first, second, and third impedance layers are the main components responsible for the electromagnetic absorption effect. (Reference) Figure 6 In (a), when the incident electromagnetic wave frequency is 4 GHz, the structure experiences higher electromagnetic energy loss in the first steady state. This energy loss is mainly concentrated in certain regions of the first and second impedance layers. At this point, the electromagnetic performance of the adjustable paper-cutting electromagnetic absorbing structure is equivalent to that of a multi-layer frequency-selective surface structure, exhibiting good low-frequency electromagnetic absorption. In the second steady state and the self-locking state, the energy loss is relatively small. (Reference) Figure 6 In (b), when the incident electromagnetic wave frequency is 9 GHz, the structure exhibits energy loss in all three states. The energy loss is higher in the self-locking state, mainly concentrated in the central regions of the first and second impedance layers. Energy loss in both steady-state states is primarily concentrated in the first impedance layer. (Reference) Figure 6 In (c), when the incident electromagnetic wave frequency is 13 GHz, the energy loss is significantly greater in the second steady state and self-locking state of the embodiment, and is mainly concentrated in the second impedance layer. At this time, the electromagnetic performance of the adjustable paper-cutting electromagnetic absorbing structure is mainly provided by the triangular impedance control plate, and the structure can be equivalent to a grid structure with good high-frequency electromagnetic wave absorption effect. (Reference) Figure 6 Regarding the changes in energy loss, the electromagnetic control process of this invention essentially regulates electromagnetic energy loss by adjusting the distribution of the impedance layer in three-dimensional space. Based on this control mechanism, this invention achieves an adjustable broadband electromagnetic wave absorption effect.

[0054] The working principle of this invention is as follows: Fractal paper-cutting and origami structures are used as structural driving components, providing out-of-plane mechanical load-bearing capacity and three-dimensional spatial deformation capability. By applying loads, the paper-cutting structural units are guided to rotate, thereby driving the origami structure to fold or unfold, thus achieving electromagnetic performance control. Square and triangular impedance control plates are structural performance control components, respectively attached to the top surface of the fractal paper-cutting structure and the side wall of the origami structure, allowing for real-time adjustment of electromagnetic wave absorption performance according to structural deformation. The reflective backplate serves as the total reflection layer of the entire absorption structure, blocking electromagnetic waves from penetrating the structure and entering other areas.

[0055] The working process of this invention is as follows: When the upper fractal paper-cutting structure and the lower fractal paper-cutting structure are in a contracted state and the folding structure is in a fully folded state, the entire wave-absorbing structure is in a first stable state. At this time, the square impedance control plates of the first impedance layer and the third impedance layer are arranged periodically without rotation angle, and the triangular impedance control plates of the second impedance layer are stacked with the side wall of the folding structure to form a multi-layer planar state. Electromagnetic waves are reflected and transmitted multiple times between the two impedance control plates, forming a strong electromagnetic resonance, inducing surface current generation and dissipating energy. At this time, the overall function of the wave-absorbing structure is equivalent to a multi-layer frequency-selective surface structure. The controllable paper-cutting electromagnetic wave-absorbing structure has good low-frequency broadband absorption performance through parameter design.

[0056] Under in-plane tensile load excitation, the upper and lower fractal paper-cutting structure units rotate, driving the origami structure to unfold from its folded state. The fractal paper-cutting and origami structures are now in their unfolded state, and the entire absorbing structure is in its second stable state. Triangular impedance control plates are assembled to form a periodically arranged impedance-type grid structure. After the incident electromagnetic wave generates its first electromagnetic resonance at the square impedance control plate, part of it is transmitted and forms a second resonance on the triangular impedance control plate. Finally, a small amount of electromagnetic wave is transmitted to the lower square impedance control plate. At this point, due to the excellent high-frequency electromagnetic absorption capability of the impedance-type grid structure, the adjustable paper-cutting electromagnetic absorbing structure exhibits high-frequency broadband absorption capability, and the surface current is mainly concentrated on the surface of the impedance-type grid structure. In this state, when an in-plane compressive load is applied, one layer of the fractal paper-cutting structure returns to its contracted state, while the hinge of the other layer of the fractal paper-cutting structure continues to bend until there is no relative rotation angle between adjacent paper-cutting units. This drives the folding structure to rotate as a whole but remains in an unfolded state. At this time, the entire absorbing structure is in a self-locking state and cannot directly switch to the first stable state. The impedance-type grid structure composed of triangular impedance control plates forms a periodic arrangement, which can adjust the absorption frequency band of the paper-cutting electromagnetic absorbing structure to shift to a lower frequency, and the structure exhibits mid-frequency broadband absorption capability.

[0057] Therefore, the adjustable paper-cutting / folding electromagnetic wave absorption structure of the present invention can achieve bistable switching by adjusting the spatial configuration of the paper-cutting / folding structure. The impedance layer layout inside the structure changes in each state, thereby affecting the surface current distribution and electromagnetic wave resonance mode. This structure possesses excellent mechanical response capabilities and can achieve adjustable switching of low, medium, and high frequency absorption characteristics under applied external loads, demonstrating broad application prospects.

[0058] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. An adjustable electromagnetic wave absorption structure for paper cutting and folding, characterized in that, It includes an upper impedance-type fractal paper-cutting structure, an impedance-type origami structure, a lower impedance-type fractal paper-cutting structure, and a reflective backplate, which are connected sequentially from top to bottom; The upper impedance-type fractal paper-cutting structure is periodically arranged in the horizontal and vertical directions, and includes an upper fractal paper-cutting structure and a first impedance layer attached to the top surface of the upper fractal paper-cutting structure. The lower impedance-type fractal paper-cutting structure adopts the same structure as the upper impedance-type fractal paper-cutting structure, and includes a lower fractal paper-cutting structure and a third impedance layer attached to the top surface of the lower fractal paper-cutting structure; the bottom surface of the lower fractal paper-cutting structure is connected to the top surface of the reflective back plate. The impedance-type origami structure is arranged periodically in the horizontal and vertical directions, and includes an origami structure and a second impedance layer attached to the inner sidewall of the origami structure; the top surface of the origami structure is connected to the bottom surface of the upper fractal paper-cutting structure, and the bottom surface of the origami structure is connected to the top surface of the lower fractal paper-cutting structure. The wave-absorbing structure drives the unfolding or folding of the origami structure through the anti-symmetrical coordinated motion of the upper impedance-type fractal paper-cutting structure and the lower impedance-type fractal paper-cutting structure.

2. The adjustable paper-cutting and folding electromagnetic wave-absorbing structure as described in claim 1, characterized in that, The upper fractal paper-cutting structure is a kirigami paper-cutting structure; The upper fractal paper-cutting structure has square paper-cutting structural units, and adjacent paper-cutting structural units are connected by flexible hinges. The first impedance layer is a square impedance control sheet, which is centrally attached to the top surface of each paper-cutting structural unit.

3. The adjustable paper-cutting and folding electromagnetic wave-absorbing structure as described in claim 2, characterized in that, The paper-cutting structural unit has a side length of 15-25mm and is made of polyurethane elastic colloid through a lamination process. The paper-cutting structural unit is obtained by curing the polyurethane elastic colloid in a lamination mold.

4. The adjustable paper-cutting and folding electromagnetic wave-absorbing structure as described in claim 3, characterized in that, The lamination mold is made by 3D printing.

5. The adjustable paper-cutting and folding electromagnetic wave-absorbing structure as described in claim 1, characterized in that, The first impedance layer is prepared by printing conductive graphite, carbon nanotubes, silver or copper materials onto the first impedance layer substrate using inkjet printing, screen printing, dip-dip or electroplating processes. The first impedance layer substrate is one or more of PI film, PEN film, FR4 plate or F4B plate, and the thickness of the first impedance layer substrate is 0.025 to 0.1 mm. The surface resistivity of the first impedance layer is 460–540 Ω / sq; the ratio of the side length of the first impedance layer to the side length of the paper-cutting structural unit is 0.5–0.

7.

6. The adjustable paper-cutting and folding electromagnetic wave-absorbing structure as described in claim 1, characterized in that, Adjacent origami structures are arranged chirally; the origami structure includes origami structure units that correspond one-to-one with the paper-cutting structure units in the vertical direction; the origami structure unit consists of an upper panel, four side panels and a lower panel; the upper panel and the lower panel are both square in shape; the four side panels are distributed circumferentially, and each side panel is formed by two equilateral right-angled triangle plates joined together.

7. The adjustable paper-cutting and folding electromagnetic wave-absorbing structure as described in claim 6, characterized in that, The second impedance layer is a triangular impedance control sheet, which is formed by printing conductive graphite, carbon nanotubes, silver or copper materials onto the inner surface of each equilateral right-angled triangle plate using inkjet printing, screen printing, dip-dip or electroplating processes.

8. The adjustable paper-cutting and folding electromagnetic wave-absorbing structure as described in claim 7, characterized in that, The upper panel, the equilateral right-angled triangular plate, and the lower panel are all prepared by double-sided laser cutting of a PET-PP-PET three-layer composite film; the PET-PP-PET three-layer composite film is prepared by cold lamination; the PET film layer is attached with an adhesive layer.

9. The adjustable paper-cutting and folding electromagnetic wave-absorbing structure as described in claim 8, characterized in that, The thickness of the PET film layer is 0.03–0.07 mm; the thickness of the PP film layer is 0.1–0.2 mm. The ratio of the length of the right-angled side of the second impedance layer to the length of the right-angled side of the equilateral right-angled triangle plate is 0.8 to 0.95; the surface resistivity of the second impedance layer is 150 to 250 Ω / sq.

10. The adjustable paper-cutting and folding electromagnetic wave-absorbing structure as described in any one of claims 1-9, characterized in that, The reflective backplate is made of the metal or carbon fiber reinforced composite material, and its thickness is much greater than the skin depth of the material.

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