Folded variant lightweight structures and pleated sandwich structures using the same

Abstract

The present application relates to the technical field of composite materials, in particular to a folded variant lightweight structure and a pleated sandwich structure using the same, the folded variant lightweight structure comprising a flexible layer and a rigid layer fixed on the upper surface of the flexible layer; the rigid layer comprises a plurality of rigid units arranged in an interval array, each rigid unit comprising two parallelogram blocks symmetrically arranged in an interval, and the two parallelogram blocks are arranged in an inverted V shape. The pleated sandwich structure comprises the folded variant lightweight structure, and the upper surface and the lower surface of the folded variant lightweight structure are both fixedly connected with a skin layer. The present application folds the laminated structure composed of the flexible layer and the parallelogram blocks to form a three-dimensional structure with rigid and flexible parts, which has the advantages of high strength and lightweight, and the folding process is simple, the size can be adjusted according to actual needs, and the application flexibility and convenience of the structure are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to folded variant lightweight structures and pleated sandwich structures using these structures. Background Technology

[0002] Chinese patent document CN102653133B discloses a folding structure of prepreg fabric and its forming method. This patent involves first manually or mechanically pressing creases into a thermosetting resin-based prepreg, then folding and pre-curing and stretching it to ultimately form a folding structure with variable structural parameters. However, this patent only addresses the prepreg material, thus significantly limiting its material selection. Furthermore, prepregs possess a certain bending strength, making manual or mechanical folding challenging, further restricting the application of this technology. Summary of the Invention

[0003] The purpose of this invention is to provide a lightweight folded variant structure and a pleated sandwich structure using the structure, in order to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a folded variant lightweight structure, also known as a pleated sandwich structure, includes a flexible layer and a rigid layer fixed to the upper surface of the flexible layer; the rigid layer includes a plurality of rigid units arranged in a spaced array, each rigid unit including two parallelogram blocks symmetrically distributed at left and right intervals, the two parallelogram blocks being arranged in an inverted V-shape; the flexible layer is folded in an alternating upward and downward folding sequence at the portion located between two adjacent parallelogram blocks to obtain the folded variant lightweight structure.

[0005] Optionally, the flexible layer can be made of any one of fabric, paper, flexible polymer film, and rubber.

[0006] Optionally, the flexible layer is bonded to the parallelogram block by an adhesive, which is a polymeric adhesive or an inorganic adhesive.

[0007] Optionally, the material of the parallelogram block is any one or more of the following: ceramic, glass, metal, wood, plastic, inorganic materials such as gypsum board, cardboard, etc., and fiber-reinforced composite materials with relative rigidity, such as polymer fibers, plant fibers (hemp fibers), carbon fibers, glass fibers, ceramic fibers such as alumina fibers, etc., reinforced with resin-based, metal-based or ceramic matrix materials.

[0008] Optionally, the flexible layer and the parallelogram block are made of the same material, and the thickness of the flexible layer is less than the thickness of the parallelogram block.

[0009] Optionally, one set of parallel sides of the parallelogram block (202) has an angle of 1-89° with the X-axis direction, and the other set of parallel sides of the parallelogram block (202) has an angle of 90° with the X-axis direction.

[0010] Optionally, one set of parallel sides of the parallelogram block makes an angle of 15° with the X-axis direction, and the other set of parallel sides of the parallelogram block makes an angle of 90° with the X-axis direction.

[0011] On the other hand, the present invention also provides the following technical solution: a pleated sandwich structure, including the above-mentioned folded variant lightweight structure, namely a pleated sandwich, wherein a skin layer is fixedly connected to both the upper and lower surfaces of the folded variant lightweight structure, and polymer foam particles are filled in the gap between the folded variant lightweight structure and the skin layer.

[0012] Optionally, the skin layer can be any one of wood veneer, paper veneer, metal veneer, plastic veneer, composite material board, or inorganic material board.

[0013] Optionally, the steps for preparing the polymer foamed particles are as follows:

[0014] S1: First, add 11.5-19.5g of 2-methylimidazole to a beaker containing 150-250mL of methanol and stir for 18-30min. Then, add 4-6g of Co(NO3)2·6H2O and 3-5g of Cu(NO3)2·6H2O to a beaker containing 180-200mL of methanol and stir for 15-25min. Then, pour all the methanol solution containing Co(NO3)2·6H2O and Cu(NO3)2·6H2O into the methanol solution containing 2-methylimidazole and stir for 8-10h. Next, add 2-3g of triblock copolymer p123 and 0.03-0.05g of dopamine and continue stirring for 5-8h. Finally, wash the mixture five times by centrifugation with methanol to obtain the cubic precursor.

[0015] S2: The cubic precursor was calcined in a vacuum at 650℃ for 3-5 hours to obtain wrinkled Co-Cu cubic particles.

[0016] S3: Take 8-10g of polyacrylamide, 0.1g of SiO2 and 0.8-2.3g of wrinkled Co-Cu cubic particles and add them to 100-150ml of water. Stir continuously at 55℃ for 40-60min to obtain flame-retardant gel.

[0017] S3: First, put the propylene butene copolymer (PPB) into a mixer preheated to 150-170℃ and mix for 5 minutes. Then, add the terpolymer of ethylene, propylene and non-conjugated diene (EPDM) and mix together. The ratio of PPB / EPDM is 65 phr / 35 phr. Then add 18 phr of paraffin oil, 3 phr of flame retardant gel and 1.5 phr of tetramethylthiuram disulfide (TMTD). Mix for 15-20 minutes. Then, cool the mixer to 100-115℃ and add 1.5 phr of sulfur. Continue mixing for 5-8 minutes. Finally, put the mixed PPB / EPDM into an open mill, press it into a mold, and put the mold into a flat vulcanizing machine at 150℃. Press for 10 minutes to obtain the sheet.

[0018] S4: First, put the board into the foaming kettle and saturate it at 130-150℃, 15-20MPa for 3-5 hours, then quickly depressurize to obtain foamed material. Then, the foamed material is subjected to secondary vulcanization at 130-150℃ to obtain the polymer foamed particles.

[0019] Compared to existing technologies, traditional honeycomb sandwich structures feature closed individual honeycomb cells that are not interconnected. Water trapped inside a single cell is difficult to evaporate due to the skin on the upper and lower surfaces and the lack of communication between cells. This new structure, using a specific folding angle, can replace the honeycomb sandwich structure, creating a lightweight, folded variant – essentially a sandwich structure – with ventilation channels. These channels can be filled with various functional materials, such as heat insulation, sound absorption, and damping agents, and the filling material is easy to replace. This invention folds a layered structure composed of flexible layers and parallelogram blocks to form a rigid-flexible three-dimensional structure with high strength and lightweight properties. The folding process is simple, and the dimensions can be adjusted according to actual needs, greatly improving the flexibility and convenience of the structure. By selecting appropriate flexible materials, the structure can be deformable and adaptable.

[0020] The pleated sandwich structure consists of a pleated thin-walled structure between two panels. This structure can provide excellent strength and stiffness while maintaining a light weight, and is widely used in aerospace, automotive, shipbuilding, construction and other fields.

[0021] A pleated thin-walled structure is a thin-walled structure composed of many small parallelogram units, resembling a pleat. This structure is characterized by its high strength and lightweight properties, providing good compressive and bending resistance.

[0022] Specifically, the present invention has the following beneficial effects:

[0023] 1. The foldable variant lightweight structure of the present invention can replace the honeycomb sandwich by using a specific folding angle. The foldable variant lightweight structure has passages, which is conducive to air permeability. Various functional materials such as heat insulation, sound absorption, and damping can be filled in the passages, and the filling materials are easy to replace.

[0024] 2. This invention folds a layered structure consisting of flexible layers and parallelogram blocks to form a rigid-flexible three-dimensional structure, which has the advantages of high strength and lightweight. The folding process is simple, and the size can be adjusted according to actual needs, which greatly improves the application flexibility and convenience of the structure. By selecting appropriate flexible materials, the structure can be deformable and variable.

[0025] In addition to the aforementioned beneficial effects, the pleated sandwich structure with a folded variant lightweight structure provided by this invention has a wide range of applications, including:

[0026] Applicable to the aerospace field:

[0027] The folded sandwich structure has become an important material due to its lightweight and high strength properties. It can not only reduce the weight of aircraft and spacecraft and improve flight performance and fuel efficiency, but the passage of the folded variant lightweight structure has both heat dissipation and air permeability, making it an ideal material for heat dissipation in aerospace equipment.

[0028] It can be applied in the construction field. The lightweight and high strength of the folded sandwich structure makes it an ideal building exterior wall panel. The passage of the folded variant lightweight structure can effectively block the transfer of heat, making it an ideal roof insulation panel.

[0029] Applicable to the automotive field, the pleated sandwich structure, with its lightweight and high-strength characteristics, can reduce the weight of automobiles, improve their fuel efficiency and driving performance. In addition, the channels of the folded variant lightweight structure can be filled with damping materials to block the transmission of sound, making it an ideal material for automotive sound insulation and vibration reduction. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the lightweight folding variant structure in this invention before folding;

[0031] Figure 2 This is a schematic diagram of the folded variant lightweight structure of the present invention after folding;

[0032] Figure 3 This is a schematic diagram of the pleated sandwich structure in this invention;

[0033] Figure 4 Scanning electron microscope image of the Co-Cu cubic precursor pair prepared in Example 1;

[0034] Figure 5Scanning electron microscope image of the wrinkled Co-Cu cubic particles prepared in Example 1;

[0035] Figure 6 Transmission electron microscope image of the wrinkled Co-Cu cubic particles prepared in Example 1;

[0036] Figure 7 Scanning electron microscope image of the Co-Cu cubic precursor pair prepared in Example 3;

[0037] Figure 8 Scanning electron microscope image of the polymer foamed particles prepared in Example 2;

[0038] Figure 9 Scanning electron microscope image of the polymer foamed particles prepared in Example 4;

[0039] Figure 10 This is a schematic diagram of the prior art aluminum corrugated strip in Example 5, which illustrates the convenient manufacturing process.

[0040] In the diagram: 100, flexible layer; 200, rigid layer; 201, rigid unit; 202, parallelogram block; 300, skin layer. Detailed Implementation

[0041] 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.

[0042] Please see Figure 1 The present invention provides the following technical solution: a foldable variant lightweight structure, comprising a flexible layer 100 and a rigid layer 200 fixedly disposed on the upper surface of the flexible layer 100. The rigid layer 200 includes a plurality of rigid units 201 arranged in a spaced array. Each rigid unit 201 includes two parallelogram blocks 202 symmetrically distributed at left and right intervals, arranged in an inverted V-shape. Specifically, one set of parallel sides of the parallelogram block 202 forms an angle of 15° with the X-axis direction, and the other set of parallel sides of the parallelogram block 202 forms an angle of 90° with the X-axis direction.

[0043] Folding is performed in an alternating upward and downward sequence on the flexible layer 100 at the intervals between two adjacent parallelogram blocks 202, resulting in a folded variant lightweight structure, such as... Figure 2 As shown.

[0044] The flexible layer 100 and the parallelogram block 202 can be made of the same or different materials. When the flexible layer 100 and the parallelogram block 202 are made of different materials, the flexible layer 100 can be made of fabric or paper. The fabric can be woven from polymer fibers, plant fibers, carbon fibers, glass fibers, and ceramic fibers, while the paper can be cotton paper, wood fiber paper, wood fiber paper, aramid paper, etc. The parallelogram block 202 can be made of ceramics, glass, metal, wood, plastics, inorganic materials such as gypsum board and cardboard, or relatively rigid fiber-reinforced composite materials, such as polymer fibers, plant fibers (hemp fibers), carbon fibers, glass fibers, ceramic fibers such as alumina fibers, etc., reinforced with resin-based, metal-based, or ceramic matrix materials. This invention also requires the selection of a suitable adhesive to bond the flexible layer 100 and the parallelogram block 202 together. Obviously, the choice of adhesive is related to the material properties of the flexible layer 100 and the parallelogram block 202. Depending on the actual needs, the adhesive can be a polymer adhesive or an inorganic adhesive.

[0045] When the flexible layer 100 and the parallelogram block 202 are made of the same material, the thickness of the flexible layer 100 is designed to be less than the thickness of the parallelogram block 202, so that the flexible layer 100 and the parallelogram block 202 have a relative difference in rigidity and flexibility, which facilitates folding.

[0046] After the flexible layer 100 and the rigid layer 200 are bonded and fixed, by simply pushing and pulling adjacent parallelogram blocks 202 alternately up and down, folding them along the flexible layer 100 and at the gap between two adjacent parallelogram blocks 202, a continuous planar-to-three-dimensional transformation can be achieved, ultimately resulting in a folded structure with hollow triangular structures as units. This invention, by folding the layered structure composed of the flexible layer 100 and parallelogram blocks 202, forms a rigid-flexible three-dimensional structure with the advantages of high strength and lightweight. The folding process is simple, and the dimensions can be adjusted according to actual needs, greatly improving the flexibility and convenience of the structure's application.

[0047] Please see Figure 3 The present invention also provides the following technical solution: a folded sandwich structure, including the above-mentioned folded variant lightweight structure, wherein a skin layer 300 is fixedly connected to both the upper and lower surfaces of the folded variant lightweight structure. The skin layer 300 is any one of wood veneer, paper veneer, metal veneer, plastic veneer, composite material board, and inorganic material board. The gap between the folded variant lightweight structure and the skin layer 300 is filled with granular encapsulation, wherein the granular encapsulation is any one of polymer foam material, hollow glass microspheres, and fly ash hollow spheres.

[0048] Example 1: Flexible layer 100, 70 g / m 2The ramie fiber plain weave fabric is made by taking a 5mm thick hardwood oblique piece as parallelogram block 202 and a 1mm thick hardwood board as skin layer 300. The flexible layer 100 and parallelogram block 202 are then bonded together with wood glue. The fabric is folded to obtain a folded variant lightweight structure. Foam is then used to bond the folded variant lightweight structure and the two skin layers 300 together to obtain a pleated sandwich structure. The gap between the folded variant lightweight structure and the skin layer is filled with polymer foam particles.

[0049] The steps for preparing the polymer foamed particles are as follows:

[0050] S1: First, add 11.5g of 2-methylimidazole to a beaker containing 150mL of methanol and stir for 18min. Then, add 4g of Co(NO3)2·6H2O and 3g of Cu(NO3)2·6H2O to a beaker containing 180mL of methanol and stir for 15min. Then, pour all the methanol solution containing Co(NO3)2·6H2O and Cu(NO3)2·6H2O into the methanol solution containing 2-methylimidazole and stir for 8h. Next, add 2g of triblock copolymer p123 and 0.03g of dopamine and continue stirring for 5h. Finally, wash the mixture 5 times by centrifugation with methanol to obtain the cubic precursor.

[0051] S2: The cubic precursor was calcined in a vacuum at 650℃ for 3 hours to obtain wrinkled Co-Cu cubic particles.

[0052] S3: Add 8g of polyacrylamide, 0.1g of SiO2 and 0.8g of wrinkled Co-Cu cubic particles to 100ml of water and stir continuously at 55℃ for 40min to obtain flame-retardant gel.

[0053] S3: First, put the propylene butene copolymer (PPB) into a mixer preheated to 150°C and mix for 5 minutes. Then, add the terpolymer of ethylene, propylene and non-conjugated diene (EPDM) and mix together. The ratio of PPB / EPDM is 65 phr / 35 phr. Then add 18 phr of paraffin oil, 3 phr of flame retardant gel and 1.5 phr of tetramethylthiuram disulfide (TMTD). After mixing for 15 minutes, cool the mixer to 100°C and add 1.5 phr of sulfur and continue mixing for 5 minutes. Finally, add the mixed PPB / EPDM to the open mill, press it into a mold, and put the mold into a flat vulcanizing machine at 150°C. Press for 10 minutes to obtain the sheet.

[0054] S4: First, the board is placed in the foaming kettle and saturated at 130℃, 15MPa for 3 hours, and then the pressure is quickly released to obtain foamed material. Then, the foamed material is subjected to secondary vulcanization at 130℃ to obtain polymer foamed particles. The secondary vulcanization time is 20 minutes, and sulfur powder is used as the sulfur source for the secondary vulcanization.

[0055] Example 2: Flexible layer 100, 80 g / m 2 The aramid fiber plain weave fabric, the parallelogram block 202 is made of carbon fiber reinforced resin sheet with a thickness of 5mm, the skin layer 300 is made of hardwood board with a thickness of 1mm, the flexible layer 100 and the parallelogram block 202 are bonded together with wood glue, and folded to obtain a folded variant lightweight structure, and foam glue is used to bond the folded variant lightweight structure and the two skin layers 300 to form a pleated sandwich structure, and the gap between the folded variant lightweight structure and the skin layer is filled with polymer foam particles.

[0056] The steps for preparing the polymer foamed particles are as follows:

[0057] S1: First, add 19.5g of 2-methylimidazole to a beaker containing 250mL of methanol and stir for 30min. Then, add 6g of Co(NO3)2·6H2O and 5g of Cu(NO3)2·6H2O to a beaker containing 200mL of methanol and stir for 25min. Then, pour all the methanol solution containing Co(NO3)2·6H2O and Cu(NO3)2·6H2O into the methanol solution containing 2-methylimidazole and stir for 10h. Next, add 3g of triblock copolymer p123 and 0.05g of dopamine and continue stirring for 8h. Finally, centrifuge and wash 5 times with methanol to obtain the cubic precursor.

[0058] S2: The cubic precursor was calcined under vacuum at 650℃ for 5 hours to obtain wrinkled Co-Cu cubic particles.

[0059] S3: Add 10g of polyacrylamide, 0.1g of SiO2 and 2.3g of wrinkled Co-Cu cubic particles to 150ml of water and stir continuously at 55℃ for 60min to obtain flame-retardant gel.

[0060] S3: First, put the propylene butene copolymer (PPB) into a mixer preheated to 170°C and mix for 5 minutes. Then, add the terpolymer of ethylene, propylene and non-conjugated diene (EPDM) and mix together. The ratio of PPB / EPDM is 65 phr / 35 phr. Then add 18 phr of paraffin oil, 3 phr of flame retardant gel and 1.5 phr of tetramethylthiuram disulfide (TMTD). After mixing for 20 minutes, cool the mixer to 115°C and add 1.5 phr of sulfur and continue mixing for 8 minutes. Finally, add the mixed PPB / EPDM to the open mill, press it into a sheet, put it into a mold, and put the mold into a flat vulcanizing machine at 150°C. Press for 10 minutes to obtain the sheet.

[0061] S4: First, the board is placed in the foaming kettle and saturated at 150℃, 20MPa for 5 hours. Then, the pressure is quickly released to obtain foamed material. Then, the foamed material is subjected to secondary vulcanization at 150℃ to obtain polymer foamed particles. The secondary vulcanization time is 60 minutes, and sulfur powder is used as the sulfur source for the secondary vulcanization.

[0062] Comparative Example 1: 5mm thick solid wood.

[0063] Comparative Example 2: 5mm thick honeycomb aluminum panel.

[0064] Experimental Example 1: The pleated sandwich structures prepared in Examples 1 and 2 were subjected to flexural strength, compressive strength, tensile strength, and plane shear strength tests compared with Comparative Example 1 and Comparative Example 2. The following results were obtained:

[0065] Example 1 Example 2 Comparative Example 1 Comparative Example 2 <![CDATA[Areal density g / m 2 > 45 50 / 72 <![CDATA[Density g / m 3 > / / 0.75 / weight (kg) 0.8 3 3.7 5.8 Flexural strength (MPa) 120.1 150.4 88.5 102.2 compressive strength (MPa) 53.2 7.2 21.6 2.4 Tensile strength (MPa) 64.0 6.5 13.2 1.5 Planar shear strength (MPa) 34.2 8.7 9.6 1.3

[0066] As can be seen from the table above, the pleated sandwich structures prepared in Examples 1 and 2 have excellent bending strength, compressive strength, tensile strength and planar shear strength, and are lightweight with a high structural weight ratio.

[0067] Example 3: Except for the absence of Co(NO3)2·6H2O in the preparation of polymer foamed particles, all other steps are the same as in Example 1.

[0068] Example 4: Except for replacing the wrinkled Co-Cu cubic particles with Co-Cu cubic precursors when preparing the flame-retardant gel, all other steps are the same as in Example 2.

[0069] Figure 4 The image shows a scanning electron microscope image of the Co-Cu cubic precursor pair prepared in Example 1. As can be seen from the image, the Co-Cu precursor prepared in this invention consists of nanoscale cubic particles with a small size.

[0070] Figure 5 This is a scanning electron microscope image of the wrinkled Co-Cu cubic particles prepared in Example 1. Due to the addition of P123 and dopamine during the preparation process, the cubic structure becomes wrinkled after calcination. However, the particle size remains at the nanoscale. The wrinkled nanoparticles can be more evenly mixed when dissolved in the foaming material later, and after solidification, they resemble tiny rivets, enhancing the material's mechanical properties.

[0071] Figure 6 Transmission electron microscopy image of the wrinkled Co-Cu cubic particles prepared in Example 1, and... Figure 5 Correspondingly, the generation of the folded cubic structure can be fully demonstrated.

[0072] Figure 7The image shows a scanning electron microscope (SEM) image of the Co-Cu cubic precursor prepared in Example 3. It can be seen that the particles prepared in Comparative Example 3, lacking Co, have irregular shapes, unlike the regular Co-Cu cubic precursor prepared in Example 1. This indicates a localized electronic synergy between Cu and Co, which ensures a uniform charge distribution around the Co-Co structure, guaranteeing the formation of a regular cubic structure. The irregular morphology is detrimental to the subsequent calcination process to prepare a wrinkled cubic structure. The wrinkled structure facilitates better and more uniform mixing with the polyacrylamide adhesive, thereby improving the material's mechanical properties and providing flame retardancy.

[0073] In order to study the morphology of the polymer foaming agent material, the polymer foaming agent material prepared in this application was taken out, freeze-dried using a freeze dryer, crushed and then its morphology was tested.

[0074] Figure 8 The image shows a scanning electron microscope (SEM) image of the polymer foamed particles prepared in Example 2. The image shows that the wrinkled particles are uniformly coated together by the polyacrylamide sol, and a cubic structure can also be observed.

[0075] Figure 9 The image shows a scanning electron microscope image of the polymer foamed particles prepared in Example 4. Analysis reveals that after replacing the wrinkled Co-Cu cubic particles with a Co-Cu cubic precursor in Example 4, the cubic structure was barely visible during gel preparation; the particles completely crumbled during the mixing process. This indicates that without the protection of the outer wrinkled layer, the Co-Cu cubic particles were easily broken during mixing, causing the polymer to aggregate directly and thus losing its anchoring effect.

[0076] Example 2: The polymer foam particles prepared in Examples 1-4 were subjected to compression set tests according to ASTM D 395-2003, "Test Method for Compression Set Properties of Rubber". The deformation was measured after compression at room temperature for 24 hours, and the following results were obtained:

[0077] Example 1 Example 2 Example 3 Example 4 Permanent Deformation 15.2±0.5％ 13.7±0.5％ 35.6±0.4％ 48.6±0.7％

[0078] The formula for calculating the compressive permanent deformation rate is:

[0079] C=(t0-t i ) / (t0-t n )×100%

[0080] Where C represents permanent pressure deformation, t0 is the original thickness, and t i t represents the thickness after compression. n This refers to the thickness of the gasket.

[0081] As shown in the table above, the polymer foam particles of the Co-Cu cubic particle flame retardant gel with wrinkles have increased steric hindrance due to the wrinkled Co-Cu cubic particles, which improves their mechanical properties.

[0082] Example 5: Convenient manufacturing process:

[0083] Alternatives to aluminum honeycomb: Common existing aluminum honeycomb forming methods: For thicker aluminum foil, special instruments such as presses are used to roll the aluminum foil strips to form corrugated strips, such as... Figure 10 As shown, the corrugated strip is then glued together to form an aluminum honeycomb core block. This method has low production efficiency and high energy consumption costs. Using the folding method of this patent, it is only necessary to lay the aluminum foil flat on a general-purpose laser engraving machine, set the parameters of the laser engraving machine, and engrave the pattern as shown on one side of the aluminum foil. Figure 1 The parallelogram shape creates a difference in rigidity between the engraved area (gap) and the parallelogram structure. By using any mechanical method to push and press adjacent aluminum sheets up and down, it can be folded along the thinner section (gap), forming a three-dimensional, folded, lightweight structure. This structure is highly efficient to manufacture, has a convenient manufacturing process, and requires no adhesives.

[0084] The technical solution provided by this invention: Manufacturing of a lightweight structure of folded variant of carbon fiber composite material (carbon fiber composite pleated sandwich):

[0085] Manufacturing hexagonal honeycomb core blocks using carbon fiber composites is a very labor-intensive process, typically requiring manual installation and curing according to the shape of a hexagonal mold, resulting in extremely low production efficiency. However, the folded variant lightweight structure of this patent offers a convenient process and allows for continuous production.

[0086] Take any commercially available carbon fiber prepreg (unidirectional or woven prepreg is acceptable) and pre-bond it together with any flexible fabric, such as nonwoven fabric (point-to-point bonding is sufficient). Lay it flat on a general prepreg cutting machine or laser engraving machine.

[0087] By controlling the parameters of the cutting machine, the carbon fiber prepreg bonded to the upper layer of the flexible fabric is cut into... Figure 1 A planar folded prefabricated structure is prepared using a parallelogram shape, and then cured according to the requirements of the commercial carbon fiber prepreg.

[0088] Once cured, the adjacent cured carbon fiber composite oblique sheets can be pushed up and down using any machinery or manual labor to fold them along the flexible seam in the middle, forming a three-dimensional folded variant lightweight structure.

[0089] The manufacturing process is simple, allowing for continuous mass production while also enabling the creation of unique sandwich structures made of carbon fiber composite materials. The advantage of this carbon fiber composite folded variant structure lies in placing the carbon fibers vertically along the force axis of the rigid inclined plates. The staggered, periodically interlocking triangular structure provides maximum stiffness and strength to the overall structure, thus maximizing the lightweight reinforcing and supporting performance of the carbon fiber.

[0090] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A foldable, lightweight structure, characterized by: The structure includes a flexible layer (100) and a rigid layer (200) fixedly disposed on the upper surface of the flexible layer (100). The rigid layer (200) includes a plurality of rigid units (201) arranged in a spaced array. Each rigid unit (201) includes two parallelogram blocks (202) symmetrically distributed at left and right intervals, and the two parallelogram blocks (202) are arranged in an inverted V-shape. The flexible layer (100) is folded in an alternating upward and downward folding sequence at the gap between two adjacent parallelogram blocks (202) to obtain the folded variant lightweight structure. A skin layer (300) is fixedly connected to both the upper and lower surfaces of the folded variant lightweight structure. Polymer foam particles are filled in the gap between the folded variant lightweight structure and the skin layer (300). The preparation steps of the polymer foam particles are as follows: S1: First, add 11.5-19.5 g of 2-methylimidazole to a beaker containing 150-250 mL of methanol and stir for 18-30 min. Then, add 4-6 g of Co(NO3)2∙6H2O and 3-5 g of Cu(NO3)2∙6H2O to a beaker containing 180-200 mL of methanol and stir for 15-25 min. Then, pour all the methanol solution containing Co(NO3)2∙6H2O and Cu(NO3)2∙6H2O into the methanol solution containing 2-methylimidazole and stir for 8-10 h. Next, add 2-3 g of triblock copolymer p123 and 0.03-0.05 g of dopamine and continue stirring for 5-8 h. Finally, wash the mixture five times by centrifugation with methanol to obtain the cubic precursor. S2: The cubic precursor was calcined in vacuum at 650℃ for 3-5 h to obtain wrinkled Co-Cu cubic particles. S3: Take 8-10 g of polyacrylamide, 0.1 g of SiO2 and 0.8-2.3 g of wrinkled Co-Cu cubic particles and add them to 100-150 ml of water. Stir continuously at 55℃ for 40-60 min to obtain flame-retardant gel. S4: First, put the propylene butene copolymer (PPB) into a mixer preheated to 150-170℃ and mix for 5 min. Then, add the terpolymer of ethylene, propylene and non-conjugated diene (EPDM) and mix together. The ratio of PPB / EPDM is 65 phr / 35 phr. Then add 18 phr of paraffin oil, 3 phr of flame retardant gel and 1.5 phr of tetramethylthiuram disulfide (TMTD). Mix for 15-20 min. After cooling the mixer to 100-115℃, add 1.5 phr of sulfur and continue mixing for 5-8 min. Finally, put the mixed PPB / EPDM into an open mill, press it into a mold, and put the mold into a flat vulcanizing machine at 150℃. Press for 10 min to obtain the sheet. S5: First, the board is placed in a foaming kettle and saturated at 130-150℃, 15-20 MPa for 3-5 hours, and then the pressure is quickly released to obtain foamed material. Then, the foamed material is subjected to secondary vulcanization at 130-150℃ to obtain the polymer foamed particles.

2. The foldable variant lightweight structure according to claim 1, characterized in that: The flexible layer (100) is made of any one of fabric, paper, flexible polymer film and rubber.

3. The foldable variant lightweight structure according to claim 1, characterized in that: The flexible layer (100) is bonded to the parallelogram block (202) by an adhesive, which is a polymer adhesive or an inorganic adhesive.

4. The folding variant lightweight structure according to claim 1, characterized in that: The rigid material of the parallelogram block (202) is any one or more of ceramics, glass, metal, wood, plastic, and fiber-reinforced composite materials with relative rigidity.

5. The foldable variant lightweight structure according to claim 1, characterized in that: The flexible layer (100) and the parallelogram block (202) are made of the same material, and the flexible layer (100) The thickness is less than the thickness of the parallelogram block (202).

6. The folding variant lightweight structure according to claim 1, characterized in that: The angle between one set of parallel sides of the parallelogram block (202) and the X-axis direction is 1-89°, and the angle between the other set of parallel sides of the parallelogram block (202) and the X-axis direction is 90°.

7. The folding variant lightweight structure according to claim 1, characterized in that: The angle between one set of parallel sides of the parallelogram block (202) and the X-axis direction is 15°, and the angle between the other set of parallel sides of the parallelogram block (202) and the X-axis direction is 90°.

8. The folding variant lightweight structure according to claim 1, characterized in that: The skin layer (300) is any one of wood veneer, paper veneer, metal veneer, plastic veneer, composite material board, or inorganic material board.

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