A full composite, foam hybrid lattice honeycomb structure formed by paper cutting and paper folding and a method of making the same

Abstract

The application discloses a full composite material formed by paper-cutting and paper-folding and a preparation method of a foam hybrid lattice honeycomb structure, and belongs to the field of composite material structure design and manufacturing. The structure comprises a lattice framework and a PMI foam core layer. The lattice framework is formed by folding carbon fiber prepreg into continuous wall plates. The continuous wall plates enclose a plurality of periodically arranged lattice cells. The PMI foam core layer is attached to the inner wall of the cells and is solidified into an integral whole with the wall plates. During preparation, the carbon fiber prepreg is cut into a two-dimensional unfolded pattern with a central platform area and two folded wing parts. The PMI foam is attached to the central platform area. The folded wing parts are folded along the edges to the direction of the foam to cover the side walls of the foam to form a three-dimensional lattice preform. After filling the silica gel inner mold, the three-dimensional lattice preform is cured in a hot press. The application realizes the integrated forming of the lattice honeycomb structure, avoids the bonding interface and fiber damage, eliminates stress concentration, simplifies the process, improves the bearing efficiency and reliability, and has good consistency and strong designability.

Description

Technical Field

[0001] This invention relates to the field of all-composite material honeycomb structure design and preparation technology, specifically to an all-composite material, foam hybrid grid honeycomb structure formed by paper cutting and folding, and its preparation method. Background Technology

[0002] Composite lattice honeycomb structures, formed by the periodic arrangement of longitudinal, transverse, and diagonal lattice bars, possess tensile-dominant mechanical advantages and excellent structural stability, making them promising candidates for applications in aerospace, deep space exploration, and high-speed rail transportation. Carbon fiber reinforced polymer (CFRP), with its high specific strength, high specific modulus, and excellent fatigue and corrosion resistance, has become an ideal substrate for fabricating high-performance lattice honeycomb structures. However, due to the discontinuous shape of the lattice structure, its manufacturing process is more complex than that of continuous-shape structures, and manufacturing technology remains a key bottleneck for engineering applications.

[0003] Traditional manufacturing methods mainly include cutting and assembly and interlocking assembly. The cutting and assembly method requires cutting composite material sheets into strips and then gluing them together. This process is cumbersome, costly, and relies on adhesives to transfer loads between discrete components. The bonding interface is the inherently weak point of the structure, and its reliability is easily affected by the uniformity of the adhesive layer, curing stress, and environmental aging. There is a risk of catastrophic failure due to interface debonding, making it difficult to meet the stringent reliability requirements of advanced industries.

[0004] The interlocking assembly method uses slotted grid bars to form a grid through assembly and bonding. This method also has significant drawbacks: the slotting process can easily damage the continuous fibers and compromise the integrity of the reinforcing phase; the slotted area is a dual concentration zone of geometry and stress, constituting the weakest link in the structure; in addition, if the thermal expansion coefficients of the panel and the core board do not match, it can easily lead to structural warping.

[0005] In summary, existing fabrication methods all rely on multi-step cutting, processing, and assembly, resulting in common drawbacks such as lengthy processes, fiber damage, and insufficient interface reliability. Therefore, developing a fabrication method that enables one-time integral molding of grid honeycomb structures is of great significance for simplifying the process, improving structural load-bearing efficiency and service reliability, and promoting its engineering applications. Summary of the Invention

[0006] Traditional grid honeycomb structure fabrication processes are cumbersome, requiring the preparation of composite material panels, cutting of these panels, and final assembly. During the interlocking of different core layers, the inability to guarantee perfectly consistent cut groove dimensions leads to stress concentration at contact points, resulting in reduced structural load-bearing capacity. To address these shortcomings, this invention provides a fully composite material, foam-hybrid grid honeycomb structure formed using paper cutting and folding techniques, along with its fabrication method. This solves the problems of complex molding processes and assembly errors affecting structural performance inherent in traditional grid structures.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A fully composite material, foam-hybrid grid honeycomb structure formed by paper cutting and folding includes a core, wherein the core comprises an integral continuous grid wall panel formed by folding carbon fiber prepreg, the grid wall panel forming a plurality of periodically arranged grid cells, and a PMI foam core layer attached to the inner side of the grid wall panel; the grid wall panel is an integrally folded continuous fiber reinforced composite material structure, and the PMI foam core layer is bonded to the grid wall panel by hot pressing and curing.

[0008] Preferably, the core has a length of 30mm, a height of 10mm, and a wall thickness of 1.5mm.

[0009] The above-mentioned method for preparing a fully composite material and foam hybrid grid honeycomb structure using paper cutting and folding includes the following steps: S1: Select carbon fiber prepreg and cut multiple two-dimensional unfolded patterns arranged in an array on the prepreg according to the number of rows and columns of the target grid honeycomb structure. Each two-dimensional unfolded pattern corresponds to a cell and is composed of a central platform area and folded wings connected to both sides of the central platform area. Adjacent two-dimensional unfolded patterns are connected to each other at the wall panel position and share the same grid wall panel, so that the whole prepreg forms a continuous paper-cut planar structure. S2: On the cut prepreg, PMI foam blocks are attached to one side surface of the central platform area of ​​each of the two-dimensional unfolded patterns; the PMI foam blocks on adjacent central platform areas are independent of each other and not connected to each other, and the height of each PMI foam block corresponds to the cell height of the target grid honeycomb structure, so that the folding wings completely cover the side wall of the PMI foam block after folding. S3: Fold the folded wings of each of the two-dimensional unfolded patterns along the edge of the corresponding central platform area toward the direction of the PMI foam block, so that each folded wing covers the sidewall of the corresponding PMI foam block, forming a three-dimensional grid prefabricated body with multiple periodic cells. S4: Fill the cell voids of the three-dimensional grid preform with a silicone inner mold, which provides lateral support to the prepreg wall panel; S5: The three-dimensional grid preform filled with silicone inner mold is cured in an autoclave to solidify the prepreg core and obtain a full composite material, foam hybrid grid honeycomb core. S6: The panel uses the same carbon fiber prepreg and layup method as the core wall panel, and is cured using the same autoclave curing process parameters as S5; S7: The cured grid honeycomb core is bonded to the composite material panel with an adhesive film and vacuum-assisted molding is used to obtain the final all-composite material, foam hybrid grid honeycomb structure.

[0010] Preferably, in step S1, each of the two-dimensional unfolded patterns is a cross-shaped planar configuration; the lateral dimension of the central platform area in the plane is equal to the thickness of the corresponding grid wall panel after folding; the lateral dimension of the folded wing in the plane is equal to the height of the corresponding grid wall panel after folding.

[0011] Preferably, in step S2, the height of the PMI foam block is equal to the height of the grid wall panel of the corresponding cell, so that the folding wings completely cover the side wall of the PMI foam block after folding; the PMI foam block is retained inside the grid wall panel after curing as the permanent core layer of each cell.

[0012] Preferably, in step S3, each of the folding wings folds along the edge of the corresponding central platform area toward the direction of the PMI foam block, with a folding angle of 90°.

[0013] Preferably, the geometric shape of the cell is rectangular.

[0014] Preferably, in step S5, the autoclave curing adopts a stepped heating and pressurization process, including: heating to 80°C at a rate of 5°C / min, applying a pressure of 0.1MPa, and holding for 30 minutes; continuing to heat to 130°C at the same rate, applying a pressure of 0.3MPa, and holding for 90 minutes; and cooling to 60°C at a rate of 10°C / min while maintaining the pressure.

[0015] Preferably, in step S5, the silicone inner mold is demolded by flexible deformation after curing, and the silicone inner mold can be reused.

[0016] Beneficial effects: Compared with existing technologies, this invention presents a fully composite material, foam hybrid grid honeycomb structure formed by paper cutting and folding, and its preparation method. Through the combined design of a PMI foam permanent core layer and a silicone inner mold curing mold, it avoids the difficulty of core mold removal in traditional assembly methods. This allows for flexible design, as cell height and thickness are not limited by demolding, further broadening the application prospects of grid honeycomb structures in lightweight load-bearing structures. It has the following advantages: (1) This invention achieves integrated molding of all-composite materials and foam-hybrid grid honeycomb structures, significantly simplifying the manufacturing process and providing advantages for rapid prototyping and mass production. The traditional grid honeycomb structure manufacturing process requires three independent steps: "composite material board molding - composite material board cutting - composite material interlocking core assembly". Each step requires multiple clamping, positioning and transfer, resulting in a lengthy process and difficulty in ensuring dimensional consistency. This invention adopts the design concept of paper cutting and folding. After the prepreg is laid up, a two-dimensional graphic is cut, and then a three-dimensional grid structure is directly obtained by folding. After being bonded to PMI foam, it is hot-pressed and cured in one go. This process reduces the traditional multi-step process to a single molding path of "lay-up-cutting-folding-curing", eliminating the need for secondary clamping and assembly. This significantly shortens the manufacturing cycle and provides a feasible process basis for mass production.

[0017] (2) Eliminating weak links in interface bonding, fiber damage, and stress concentration in traditional assembly processes, fundamentally improving structural load-bearing efficiency and service reliability. Traditional cutting and assembly methods rely on adhesives to transfer loads between discrete components. The bonding interface is an intrinsically weak link, and its reliability is easily affected by the uniformity of the adhesive layer, residual stress after curing, and environmental aging, posing a risk of sudden failure caused by interface debonding. Although traditional interlocking assembly methods improve positioning accuracy, the slotting process cuts off continuous fibers, destroys the integrity of the reinforcing phase, and the slot area is both a geometrical abrupt change and a stress concentration area, constituting the weakest part of the structure. This invention adopts an integral folding molding process, where the grid wall panel is formed by folding the same prepreg sheet. There is no need to cut the composite material into slots or glue the discrete components together, thus avoiding the destruction of fiber continuity and eliminating stress concentration in the slot area, fundamentally improving the load transfer path and service reliability of the structure.

[0018] (3) Ensure the consistency of structural forming and dimensional designability, and prevent structural deformation by using PMI foam support and silicone mold to assist curing. In this invention, the PMI foam is attached to the middle area of ​​the prepreg before folding. After folding, the folded wings on both sides of the foam cover the foam sidewalls, so that the foam can simultaneously support the core layer and maintain the wall panel configuration during the curing process. At the same time, the silicone flexible mold is filled into the gaps of the grid cells formed by folding, providing uniform lateral support to the prepreg wall panel, effectively preventing structural deformation caused by prepreg rebound or uneven pressure during the curing process, and ensuring that the grid core shape is regular after curing. Compared with the assembly error and performance dispersion introduced by the inconsistent processing accuracy of the slots in traditional interlocking assembly, this invention uses two-dimensional graphic precise cutting and folding to form. Each cell is repeatedly generated by the same cutting graphic, resulting in good forming consistency. Moreover, parameters such as core length, height and wall panel thickness can be flexibly changed by adjusting the size of the cutting graphic, showing good dimensional designability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the optimization strategy for the molding design of the all-composite material, foam hybrid grid honeycomb structure in an embodiment of the present invention; Figure 2 This describes the spatial planning and dimensions of the all-composite material grid honeycomb prepreg before cutting in this embodiment of the invention. Figure 3 This invention illustrates the folding process and corresponding dimensions of the all-composite material, foam hybrid grid honeycomb structure, which folds from a two-dimensional configuration to a three-dimensional configuration.

[0020] Figure 4 The assembly drawing shows the silicone mold and the composite core, along with a schematic diagram of the composite material inside the mold. Figure 5 The image shows the overall structure and internal details of the finished all-composite grid structure based on paper cutting and origami. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments: A method for integrating a fully composite material and a foam hybrid grid honeycomb structure using paper cutting and folding techniques includes the following steps: Step 1: Composite Material Prepreg Layup: Orthogonal layup of carbon fiber prepreg is used. Two layers of prepreg are laid up in the same direction, and the overall size of the prepreg after layup is 184.5mm × 184.5mm. In this embodiment, the layup method is [0 / 90]s orthogonal layup, that is, the fiber directions of the two layers of prepreg are 0° and 90° respectively, to ensure that the grid wall panel has high load-bearing capacity in both in-plane directions after curing.

[0022] Step 2: Cutting the composite prepreg: Cut the prepreg after layup into paper-cut patterns. For example... Figure 2 As shown, multiple continuously distributed two-dimensional unfolded patterns are cut out on a whole sheet of 184.5mm×184.5mm prepreg according to the cell array arrangement of the target grid honeycomb structure. Figure 2 The geometric dimensions of a single cell are labeled: cell length. l =30mm, cell height h =10mm (i.e., the height of the folded panel), panel thickness t =1.5mm (i.e., the lateral dimension of the central platform area in the plane). Each two-dimensional unfolded shape has a cross-shaped configuration, consisting of a central platform area in the middle and folded wings connecting its left and right sides respectively; wherein, the lateral width of the central platform area is the wall panel thickness. t The lateral width of each of the two folding wings is equal to the cell height. hAdjacent two-dimensional unfolded shapes are directly connected at the wall panel location, meaning adjacent cells share the same longitudinal or transverse wall panel. The shapes are not independently cut into blocks, but are continuously distributed across the entire prepreg sheet, thus forming a unified, paper-cut-like planar structure after cutting. After cutting, the entire prepreg sheet remains intact, without needing to be separated into multiple independent sheets. This step uses a planar paper-cutting method to cut the two-dimensional unfolded shapes into shape in one step. Before folding, the wall panels of all cells are connected in the plane through a shared wall panel design, which is a crucial prerequisite for achieving subsequent integrated folding and forming.

[0023] Step 3: PMI Foam Lamination: After cutting, while maintaining the entire prepreg sheet as a whole, laminate PMI foam blocks onto one side of the central platform area of ​​each 2D unfolded pattern. The height of each PMI foam block is equal to the cell height. h =10mm. The PMI foam blocks on adjacent central platform areas are independent and unconnected. Each PMI foam block is aligned with its corresponding central platform area, ensuring that the width of the folding wings reserved on both sides of the central platform area is equal. This guarantees that the wings can symmetrically cover the foam sidewalls during subsequent folding. In this embodiment, the height of the PMI foam block is designed to be consistent with the cell height, i.e., the foam thickness is equal to the width of the prepreg folding wings. The purpose is to ensure that the folded prepreg wings can completely cover the foam sidewalls without overlap or insufficient coverage, thereby ensuring the accurate height dimensions and regular shape of each cell wall panel after curing.

[0024] Step 4: Fold and shape: such as Figure 3 As shown, the folding wings of each two-dimensional unfolded shape are simultaneously folded 90° towards the PMI foam block along the edge of the corresponding central platform area, so that each folding wing covers the left and right side walls of the corresponding PMI foam block. After folding, the top surface of each PMI foam block is still exposed, the bottom surface is in contact with the prepreg central platform area, and the left and right side walls are completely covered by the prepreg wings, forming a three-layer sandwich structure of prepreg-PMI foam-prepreg. Adjacent folding wings naturally converge at the cell boundary, sharing the same wall panel to form a three-dimensional grid prefabricated body with multiple periodic rectangular cells, without any additional connection or splicing operations between the cells.

[0025] Step 5: Fill the silicone inner mold: (e.g.) Figure 4 As shown, silicone inner molds are filled into the cell voids of the three-dimensional grid preform. The shape and size of the silicone inner molds match the cell voids, providing uniform lateral support for the prepreg wall panel and preventing the wall panel from deforming due to prepreg rebound or uneven pressure during the curing process. This ensures that the grid cell dimensions are accurate and the wall panel is straight after curing.

[0026] Step Six: Curing of the All-Composite Grid Structure: The three-dimensional grid preform filled with a silicone inner mold is cured using an autoclave process. The specific operation is as follows: The preform covered with breathable felt and the silicone inner mold are sealed with a vacuum bag, and a vacuum valve is installed. The entire structure is placed in the autoclave, and the vacuum valve is connected to the extraction pipeline. The curing process follows a stepped heating and pressurization process: Heating is increased to 80°C at a rate of 5°C / minute, during which only a vacuum is applied, without additional pressure; after reaching 80°C, the temperature is held for 30 minutes, and a pressure of 0.1 MPa is applied; after the holding period, the temperature is increased to 130°C at the same rate, while the pressure is increased to 0.3 MPa; after reaching 130°C, the temperature is held for 90 minutes, maintaining a pressure of 0.3 MPa; after the holding period, the temperature is decreased to 60°C at a rate of 10°C / minute while maintaining a pressure of 0.3 MPa. The pressure is then released, the cured core is removed, and the silicone inner mold is removed to obtain the all-composite, foam-hybrid grid honeycomb core. After the silicone inner mold has cured, it can be demolded through flexible deformation and reused.

[0027] Step 7: Preparation of composite material panel: The composite material panel uses the same carbon fiber prepreg and layup method as the core wall panel, and is formed by autoclave curing process.

[0028] Step 8: Assemble the entire composite material and foam hybrid geogrid honeycomb structure: First, lay an adhesive film on the platform used to bond the composite material and foam hybrid geogrid honeycomb structure. Then, using vacuum-assisted molding technology, lay peelable fabric and breathable felt sequentially on the assembled composite material and foam hybrid geogrid honeycomb structure components, and seal them in vacuum bags. Next, place the sealed body into an oven and connect an external vacuum pump to evacuate the air, ensuring the sample is in a vacuum environment throughout the curing process. The curing temperature parameters are set as follows: first, heat to 80℃ at a heating rate of 3℃ / min and hold at 80℃ for 30 minutes; then heat to 130℃ at a rate of 5℃ / min and hold at 130℃ for 90 minutes. After the holding period, turn off the oven and allow it to cool naturally to below 60℃. Then, turn off the vacuum pump, open the oven, and remove the cured sample.

[0029] The design concept of this invention is as follows: Figure 1 As shown: First, the prepreg after layup is pre-cut to obtain a two-dimensional unfolded diagram of the cured core. Then, it is bonded and cured together with PMI foam through folding. The PMI foam mainly serves a supporting role, ensuring the regular shape of the cured composite prepreg. The entire design adopts a one-piece molding process, meaning that the grid structure core can be obtained with only one curing, abandoning the traditional splicing concept and greatly improving the molding speed and quality of the core.

[0030] Based on the above design concept, this embodiment provides a method for preparing a fully composite material, foam hybrid grid honeycomb structure formed by paper cutting and folding, using a resin-based composite orthogonal prepreg. The preparation method includes the following steps: Step 1: Prepreg preparation and graphic cutting.

[0031] The composite prepreg is cut to the target size, and then the cutting area is planned on the prepreg according to the cell array of the grid honeycomb structure, and a two-dimensional unfolded pattern that meets the geometric requirements of the core is cut out in one go.

[0032] The design intent of Step One: This step completes the two-dimensional unfolded pattern preparation of all cell wall panels through a single cut, ensuring that adjacent cells are connected to each other at the wall panel location and share the same wall panel, so that the entire prepreg retains a complete integrated planar structure after cutting. This is a prerequisite for subsequent "paper-cutting" style continuous folding molding, avoiding the cumbersome operation of cutting the prepreg into multiple independent sheets and processing them separately in traditional methods.

[0033] Step 2: PMI foam bonding and folding shaping.

[0034] Align and attach the central platform area of ​​the cut prepreg with the PMI foam, then fold the prepreg wings on both sides of the central platform toward the foam to make the prepreg and PMI foam in close contact, forming a three-layer sandwich structure with prepreg covering the foam.

[0035] The design intent of Step Two: In this step, PMI foam serves two functions simultaneously—first, as a "mold" for folding and molding, it provides clear folding boundaries and support surfaces for the prepreg wings, ensuring precise folding angles and straight panels; second, the folded prepreg wings completely cover the foam sidewalls, allowing the foam to remain as a permanent core layer within the cell during subsequent curing, eliminating the need for post-curing filling. The close contact established between the prepreg and foam during the folding stage is beneficial for the quality of the interfacial bonding between them after curing.

[0036] Step 3: Fill the silicone inner mold.

[0037] Silicone inner molds are inserted into all the cell voids of the folded grid honeycomb structure to provide pre-support for the prepreg wall panels.

[0038] The design intent of step three: After folding and before curing begins, the prepreg is still in an uncured, soft state. Without support, the folded panel is prone to deformation due to material springback or gravity, leading to distorted cell shape. The silicone inner mold provides lateral support to the panel before curing, constraining its position in space and preventing deformation during curing. During curing, the thermal expansion of the silicone provides internal molding pressure. Furthermore, the silicone inner mold is flexible, allowing it to be removed and reused after curing.

[0039] Step 4: Curing and shaping in an autoclave.

[0040] The assembled core and silicone inner mold are placed into a vacuum bag and sealed. The prepreg resin is then cured in an autoclave to fully crosslink and cure, resulting in a fully composite material grid honeycomb core.

[0041] The design intent of step four is as follows: During the autoclave curing process, air is removed from the interlayers of the prepreg and the interface between the silicone inner mold and the wall panel by vacuuming, preventing porosity defects after curing. Applying air pressure ensures tight compaction of the prepreg layers, guaranteeing the fiber volume fraction and interlayer bonding strength of the wall panel. The silicone inner mold undergoes thermal expansion during curing, providing uniform pressure from the inside out to the wall panel. This pressure, combined with the external air pressure applied by the autoclave, further improves the molding density and dimensional accuracy of the wall panel.

[0042] Step 5: Prepare composite material panels.

[0043] The composite panel is prepared separately using the same autoclave curing process as the core.

[0044] The design intent of step five: As the skin of the grid honeycomb structure, the curing process of the panel is consistent with that of the core. This ensures that the panel and the core have similar curing shrinkage rates and thermal expansion behaviors during subsequent assembly, reducing the risk of assembly stress and structural warping caused by thermal mismatch.

[0045] Step Six: Fabrication of Composite Panels In this step, the panel uses the same carbon fiber prepreg and layup method as the core wall panel to ensure that the panel and the core have similar mechanical properties and thermal expansion behavior during subsequent assembly. Figure 5 This image shows a physical photograph and enlarged view of the internal structure of a fully composite material, foam-mixed grid honeycomb core, after curing and removal of the silicone inner mold. From... Figure 5 It can be seen that the grid cells are regular in shape and uniformly arranged. The wall panels transition continuously at the cell boundaries without any splicing or bonding marks. The PMI foam core layer is tightly bonded to the wall panels without any delamination or detachment.

[0046] Step 7: Overall assembly of the core and panel.

[0047] The cured grid honeycomb core and composite material panel are bonded together using an adhesive film, and vacuum-assisted molding technology is used for overall curing, completing the final assembly of the all-composite grid honeycomb structure. The purpose of this step is to ensure that the bonding and assembly of the core and panel are carried out in a vacuum environment. By removing volatiles and air bubbles between the adhesive film layers through vacuuming, the adhesive layer is ensured to be continuous and dense, avoiding localized adhesive gaps or pore defects at the bonding interface, thereby ensuring a continuous and reliable load transfer path between the core and panel.

Claims

1. A fully composite material, foam-mixed grid honeycomb structure formed by paper cutting and folding, characterized in that, The device includes a core, which comprises an integral continuous grid panel formed by folding carbon fiber prepreg, the grid panel forming a plurality of periodically arranged grid cells, and a PMI foam core layer attached to the inner side of the grid panel; the grid panel is an integrally folded continuous fiber reinforced composite material structure, and the PMI foam core layer is bonded to the grid panel by hot pressing and curing.

2. The all-composite material, foam-mixed grid honeycomb structure formed by paper cutting and folding as described in claim 1, characterized in that, The core is 30mm long, 10mm high, and the wall panel is 1.5mm thick.

3. A method for preparing a fully composite material, foam hybrid grid honeycomb structure formed by paper cutting and folding as described in claim 1, characterized in that, Includes the following steps: S1: Select carbon fiber prepreg and cut multiple two-dimensional unfolded patterns arranged in an array on the prepreg according to the number of rows and columns of the target grid honeycomb structure. Each two-dimensional unfolded pattern corresponds to a cell and is composed of a central platform area and folded wings connected to both sides of the central platform area. Adjacent two-dimensional unfolded patterns are connected to each other at the wall panel position and share the same grid wall panel, so that the whole prepreg forms a continuous paper-cut planar structure. S2: On the cut prepreg, PMI foam blocks are attached to one side surface of the central platform area of ​​each of the two-dimensional unfolded patterns; the PMI foam blocks on adjacent central platform areas are independent of each other and not connected to each other, and the height of each PMI foam block corresponds to the cell height of the target grid honeycomb structure, so that the folding wings completely cover the side wall of the PMI foam block after folding. S3: Fold the folded wings of each of the two-dimensional unfolded patterns along the edge of the corresponding central platform area toward the direction of the PMI foam block, so that each folded wing covers the sidewall of the corresponding PMI foam block, forming a three-dimensional grid prefabricated body with multiple periodic cells. S4: Fill the cell voids of the three-dimensional grid preform with a silicone inner mold, which provides lateral support to the prepreg wall panel; S5: The three-dimensional grid preform filled with silicone inner mold is cured in a hot autoclave to solidify the prepreg and obtain a full composite material, foam hybrid grid honeycomb core. S6: The panel uses the same carbon fiber prepreg and layup method as the core wall panel, and is cured using the same autoclave curing process parameters as S5; S7: The cured grid honeycomb core is bonded to the composite material panel with an adhesive film and vacuum-assisted molding is used to obtain the final all-composite material, foam hybrid grid honeycomb structure.

4. The method for preparing a fully composite material, foam hybrid grid honeycomb structure formed by paper cutting and folding according to claim 3, characterized in that, In step S1, each of the two-dimensional unfolded patterns is a cross-shaped planar configuration; the lateral dimension of the central platform area in the plane is equal to the thickness of the corresponding grid wall panel after folding; the lateral dimension of the folded wing in the plane is equal to the height of the corresponding grid wall panel after folding.

5. The method for preparing a fully composite material, foam hybrid grid honeycomb structure formed by paper cutting and folding according to claim 3, characterized in that, In step S2, the height of the PMI foam block is equal to the height of the grid wall panel of the corresponding cell, so that the folded wings completely cover the side wall of the PMI foam block after folding; the PMI foam block is retained inside the grid wall panel after curing as the permanent core layer of each cell.

6. The method for preparing a fully composite material, foam hybrid grid honeycomb structure formed by paper cutting and folding according to claim 3, characterized in that, In step S3, each of the folding wings folds along the edge of the corresponding central platform area toward the direction of the PMI foam block, with a folding angle of 90°.

7. The method for preparing a fully composite material, foam hybrid grid honeycomb structure formed by paper cutting and folding according to claim 3, characterized in that, The geometric shape of the cell is rectangular.

8. The method for preparing a fully composite material, foam hybrid grid honeycomb structure formed by paper cutting and folding according to claim 3, characterized in that, In step S5, the autoclave curing process adopts a stepped heating and pressurization process, including: heating to 80°C at a rate of 5°C / min, applying a pressure of 0.1MPa, and holding for 30 minutes; continuing to heat to 130°C at the same rate, applying a pressure of 0.3MPa, and holding for 90 minutes; and cooling to 60°C at a rate of 10°C / min while maintaining the pressure.

9. The method for preparing a fully composite material, foam hybrid grid honeycomb structure formed by paper cutting and folding according to claim 3, characterized in that, In step S5, the silicone inner mold is demolded by flexible deformation after curing, and the silicone inner mold can be reused.

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