3D-printed composite energy-absorbing curb based on gradient poisson ratio metamaterial and preparation method thereof

Abstract

The present application relates to a kind of 3D printing composite energy-absorbing curb based on gradient poisson ratio metamaterial and its preparation method, belong to curb preparation field, including shell, gradient poisson ratio metamaterial core structure being arranged in shell interior and rubber filling body being filled in the pore of core structure;Core structure is formed by the arrangement of multiple basic cells along predetermined direction three-dimensional lattice structure, and basic cell is concave hexagonal structure unit, and multiple basic cells are arranged in space by the way of common node and form three-dimensional lattice structure that is interconnected, and by changing the geometric parameters of basic cell, the structure presents controllable poisson ratio gradient distribution in space.The present application sets up the metamaterial core with poisson ratio gradient distribution in curb, and combines elastomer filling and fiber reinforced composite shell constraint, realizes stable controllable progressive crushing energy-absorbing, to significantly improve the buffering and protection performance of curb under the action of vehicle lateral impact.

Description

Technical Field

[0001] This invention relates to a 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterial and its preparation method, belonging to the field of curbstone preparation technology. Background Technology

[0002] With the increasing traffic density on urban roads, collisions between vehicles and road infrastructure are becoming more frequent. As a crucial component of road boundaries, curb stones are often the first structures to come into contact with vehicles when they veer off course or experience lateral impacts. Traditional curb stones are typically cast monolithically from concrete. While this type of structure possesses high strength and durability, the material itself is brittle and has limited impact resistance. Under vehicle collisions, it is prone to cracking or complete failure, and the impact load is difficult to dissipate effectively, easily causing significant secondary injuries to vehicles and occupants. Therefore, developing new curb stone structures with good energy absorption and impact resistance is of great importance.

[0003] To improve the impact resistance of curb stones, existing technologies have proposed several composite structural forms, such as using metal or fiber-reinforced composite material shells filled with foam materials, honeycomb structures, or lightweight concrete, to achieve a certain degree of buffering and energy absorption. However, these structures still suffer from limited energy absorption efficiency, uncontrollable structural crushing modes, and susceptibility to local instability under impact loads. Furthermore, the mechanical properties of traditional honeycomb or foam structures are generally consistent throughout the entire structure, making it difficult to optimize spatial distribution according to the impact propagation path. This limits the overall energy absorption capacity and peak load control capability of the structure.

[0004] In recent years, with the development of mechanical metamaterials research, negative Poisson's ratio structures with special geometric configurations have gradually attracted attention. Negative Poisson's ratio structures undergo lateral contraction under compression, thus exhibiting excellent penetration resistance and energy absorption performance. However, uniform structures with a single Poisson's ratio still struggle to simultaneously achieve impact resistance and load diffusion in actual impact environments. To address this, researchers have proposed gradient metamaterial structures that achieve a spatial gradient distribution of Poisson's ratio by changing the structural geometric parameters. This allows the structure to exhibit different mechanical responses in different regions, thereby achieving more stable progressive crushing energy absorption behavior. However, most existing research remains at the experimental or theoretical stage, with limited applications in engineering components, especially in road protection components such as curbs, where mature structural forms are yet to be seen.

[0005] On the other hand, gradient metamaterial structures typically possess complex three-dimensional lattice configurations, making high-precision molding difficult to achieve with traditional manufacturing processes, thus limiting their engineering applications. With the development of additive manufacturing technology, 3D printing technology enables the integrated manufacturing of complex spatial structures, providing a new feasible approach for the application of metamaterial structures in engineering components. Therefore, how to design an energy-absorbing curbstone with a gradient Poisson's ratio metamaterial core structure using additive manufacturing technology, and further improve its structural stability and energy absorption capacity through methods such as elastomer filling, has become an urgent technical problem to be solved. Summary of the Invention

[0006] To address the problems of insufficient impact resistance, low energy absorption efficiency, and difficulty in achieving complex energy-absorbing structures using traditional manufacturing processes, this invention provides a 3D-printed composite energy-absorbing curb based on gradient Poisson's ratio metamaterials and its preparation method. By setting a metamaterial core with a Poisson's ratio gradient distribution inside the curb and combining it with an elastomer-filled and fiber-reinforced composite shell for constraint, stable and controllable progressive crushing energy absorption is achieved, thereby significantly improving the cushioning and protective performance of the curb under lateral impact from vehicles.

[0007] The technical solution of the present invention is as follows:

[0008] A 3D-printed composite energy-absorbing curbstone based on a gradient Poisson's ratio metamaterial includes an outer shell, a gradient Poisson's ratio metamaterial core structure disposed inside the outer shell, and a rubber filler filling the pores of the core structure. In actual fabrication, the rubber filler is filled into the interpenetrating pores of the gradient Poisson's ratio core through an infusion process. During impact, the rubber filler dissipates energy through viscoelastic deformation and provides lateral support to the metamaterial skeleton to suppress buckling.

[0009] The gradient Poisson's ratio metamaterial core structure consists of multiple basic cells arranged along a predetermined direction to form a three-dimensional lattice structure. The basic cells are concave hexagonal structural units. Multiple basic cells are arranged in space through a common node to form an interconnected three-dimensional lattice structure. By changing the geometric parameters of the basic cells, the structure can exhibit a controllable Poisson's ratio gradient distribution in space.

[0010] Preferably, the geometric parameters include the tilt angle α and the cell link wall thickness t;

[0011] The tilt angle α refers to the angle between the inclined rods constituting the cell structure and the horizontal direction. The tilt angle α varies gradually along the thickness direction of the curbstone, realizing the overall structural performance transition from negative Poisson's ratio to positive Poisson's ratio. In the impact side region near the roadway, the tilt angle α of the basic cells is configured to exhibit negative Poisson's ratio characteristics, causing the structure to undergo lateral contraction under compression, thereby improving its resistance to intrusion and local load-bearing capacity. From the impact side region to the region away from the roadway, the tilt angle α of the basic cells gradually changes, causing the equivalent Poisson's ratio of the structure to gradually transition to positive Poisson's ratio characteristics, promoting the diffusion and distribution of loads within the structure. Through the above gradient transition, the entire structure exhibits a stable layer-by-layer crushing mode under impact, thereby achieving efficient energy absorption and peak load control. Layer-by-layer crushing refers to the fact that when the structure is subjected to impact load, due to the Poisson's ratio gradient set along the thickness direction, the negative Poisson's ratio cell layers near the impact side have relatively low stiffness and exhibit the characteristic of contracting towards the center under compression, thus preferentially becoming unstable and compacting to dissipate the initial impact energy. Only after the current cell layer is fully compacted (densified) can the load be effectively transferred to the subsequent positive Poisson's ratio gradient layers. This mechanism avoids instantaneous instability of the entire structure, ensures the smoothness of load transfer, and thus effectively reduces the peak impact force. In other words, under impact load, deformation first occurs in the low-stiffness negative Poisson's ratio cell layer near the impact side. This layer of cells absorbs energy through lateral contraction and bending deformation until it is fully compacted. Subsequently, the shock wave continues to propagate inward, triggering the instability deformation of the cells in the next gradient layer. Through the sequential "instability-compaction" cycle of each gradient layer, an ordered crushing sequence is formed in time and space, thereby achieving the gradual distribution of impact energy and smooth control of peak load.

[0012] Since the main impact loads generated by vehicles on the curb usually come from the direction of the road lane, that is, propagating along the thickness of the curb, the Poisson's ratio gradient is designed in this direction so that the structure can be optimized for the impact propagation path.

[0013] Preferably, the tilt angle α varies along the gradient direction according to a preset functional relationship, which allows the cell equivalent Poisson's ratio to gradually transition from a negative value to a positive value. Tilt angle The following functional relationship must be satisfied:

[0014]

[0015] in, For the minimum tilt angle, For the maximum tilt angle, The coordinates along the gradient direction represent the specific coordinates from the impact surface inwards. (Variable) Established along the thickness direction of the curbstone (i.e., the gradient direction), it represents the specific position coordinates from the impact surface inwards, as shown in the function formula. This determines the evolution of the basic cell tilt angle α at different depths in the thickness direction.

[0016] This represents the total length along the gradient direction. , For gradient exponent, This is the gradient adjustment coefficient, used to adjust the rate of change of the cell tilt angle along the gradient direction. Its physical meaning can be interpreted as: adjusting the rate of change of the cell tilt angle along the structural gradient direction, controlling the crushing propagation sequence of the structure under impact load, and optimizing the energy absorption distribution. When = 0, the gradient function is a standard power function gradient, and the structure absorbs energy uniformly. When the gradient is greater than 0, the initial gradient change is relatively gradual, which can reduce the peak impact force. When the gradient is less than 0, the gradient changes rapidly in the early stage, which can improve the structure's resistance to intrusion; over-adjusting the gradient exponent... The crush propagation mode of the control structure during the impact process.

[0017] Preferably, the cell link wall thickness *t* is a crucial geometric parameter affecting the mechanical properties of metamaterial structures. By rationally selecting the link wall thickness, the local bending stiffness and buckling deformation characteristics of the cell structure can be adjusted, thereby matching it with gradient Poisson's ratio structures. Specifically, cell links primarily undergo bending deformation under compression, and their bending stiffness is closely related to the link wall thickness. When the link wall thickness is small, the structure is more prone to local bending or buckling deformation under impact loads, which is beneficial for absorbing impact energy; when the link wall thickness is large, it can improve the overall stability of the structure.

[0018] In this invention, the wall thickness of the cell link is usually designed in conjunction with the cell geometry and Poisson's ratio gradient structure, so that the structure can form a stable layer-by-layer crushing deformation mode under impact load, thereby realizing the gradual dissipation of impact energy.

[0019] The projection length of the basic cell in the gradient direction (i.e. the curb thickness direction) is defined as the cell characteristic size; when the cell characteristic size is 10 to 20 mm, the cell link wall thickness t is 2 to 3 mm to achieve a balance between structural strength and energy absorption performance.

[0020] exist Figure 1The single cell structure shown corresponds to the total span of a single cell junction in the thickness direction. The characteristic size determines the hierarchical distribution density of the gradient structure within the curbstone. For example, when the characteristic size is preferably 15 mm, approximately 13 cell layers can be arranged in a 200 mm thick curbstone, thus ensuring sufficient evolution space for the Poisson's ratio gradient and achieving stable progressive crushing. Matching the connecting rod wall thickness t with the characteristic size (e.g., 2-3 mm corresponds to 10-20 mm) is to control the cell slenderness ratio of the metamaterial, ensuring that the support column undergoes primarily bending deformation rather than simple brittle fracture under pressure, thereby optimizing the energy absorption distribution.

[0021] In order to ensure the energy absorption performance of the structure while taking into account the manufacturing accuracy of 3D printing, the feature size of the basic cell in the gradient direction is preferably 10mm to 30mm, and more preferably about 15mm.

[0022] With a curb thickness of 200 mm, the metamaterial core contains at least 8 basic cell layers along the gradient direction, preferably 10 to 20 basic cell layers. A sufficient number of cell layers ensures a continuous Poisson's ratio gradient distribution, thus forming a stable progressive crushing energy absorption mode. Here, "layer" refers to the number of physical units continuously arranged along the thickness direction. Setting at least 8 layers (preferably 10 to 20 layers) ensures sufficient discrete sampling accuracy of the Poisson's ratio gradient. A sufficient number of layers allows each cell layer to undergo a "instability-compaction" cycle sequentially according to a preset gradient order as the shock wave propagates into the structure, thereby forming a stable, progressive, layer-by-layer crushing on a macroscopic scale and effectively controlling the peak load.

[0023] Preferably, the interior of the three-dimensional lattice structure consists of interconnected porous spaces, into which rubber fillers are injected, forming a composite interpenetrating structure between the gradient Poisson's ratio metamaterial core structure framework and the rubber fillers. The rubber fillers can undergo viscoelastic deformation under impact loads, thereby dissipating energy and providing lateral support to the metamaterial cells to suppress local buckling and improve structural crush stability.

[0024] Preferably, both the outer shell and the gradient Poisson's ratio metamaterial core structure are printed from glass fiber reinforced thermoplastic resin composite material, which can be manufactured by additive manufacturing technology; the glass fiber reinforced thermoplastic resin composite material includes a resin matrix and glass fibers, the resin matrix is ​​PLA or PETG, the mass content of glass fibers is 10% to 35%, and the length of glass fibers is 0.2 mm to 1 mm.

[0025] The outer shell and the gradient Poisson's ratio metamaterial core structure have the same material composition. The difference lies in the printing parameters. The outer shell uses a 100% infill rate to ensure density and impermeability; the core structure is printed as a porous skeleton according to a gradient function to accommodate the injection of elastomer. During the printing process, the preferred layer thickness is 0.2mm to 1.0mm, and the printing path is optimized according to the stress direction of the structure. The outer shell uses a higher infill rate to improve overall stiffness and structural stability.

[0026] Preferably, the glass fiber reinforced thermoplastic resin composite material also includes an anti-ultraviolet additive, which is a benzotriazole or benzophenone-based ultraviolet absorber, and the amount added is 0.5% to 2.0% of the resin matrix mass. Considering the harsh service environment of curb stones (such as impact abrasion and salt frost erosion), the overall incorporation of an anti-ultraviolet agent can ensure that even if the outer shell is partially damaged, the internal metamaterial core still has excellent anti-aging capabilities, thereby ensuring the safety of the curb stone throughout its entire service life from both physical and chemical dimensions.

[0027] Preferably, the outer shell has a thin-walled structure with a wall thickness of 3 to 8 mm.

[0028] A method for preparing the above-mentioned 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterials includes:

[0029] S1, Raw material preparation:

[0030] PLA resin was selected as the resin matrix, and glass fiber was added to the resin matrix as a reinforcing material and UV-resistant additive. PLA resin particles, glass fiber and UV-resistant additive were added to a high-speed mixer and mixed for 10 to 20 minutes to ensure uniform dispersion of the components, thereby improving the UV aging resistance and long service life of the curbstone. Subsequently, composite material particles for 3D printing were prepared by extrusion granulation equipment.

[0031] S2, Structural Modeling and Printing Parameter Settings:

[0032] A three-dimensional model was established based on the dimensions of the curbstone structure, and a gradient Poisson's ratio metamaterial core structure was constructed inside the shell. The core structure consists of multiple basic cells arranged along a predetermined direction to form a three-dimensional lattice structure. The basic cells are concave hexagonal structural units, and the basic cells are arranged along the thickness direction of the curbstone to form a gradient structure.

[0033] Set printing parameters, including nozzle temperature, printing platform temperature, printing layer thickness, infill rate and printing speed, and perform overall printing through fused deposition modeling (FDM) 3D printing equipment to integrate the outer shell with the internal core structural skeleton.

[0034] S3, Elastomer Filler:

[0035] After printing, the core structure of the metamaterial is filled with an elastomer material, which is rubber, to fully fill the entire three-dimensional lattice structure.

[0036] S4, Curing process:

[0037] After the injection is completed, allow it to stand at room temperature for 24 hours to cure.

[0038] For any details not covered in this invention, please refer to the prior art.

[0039] The beneficial effects of this invention are as follows:

[0040] This invention utilizes a metamaterial core structure with a Poisson's ratio gradient distribution within the curbstone, enabling the structure to form a stable progressive crushing mode under impact. Compared to traditional uniform structures, this gradient design effectively regulates the deformation pattern in different regions, allowing impact energy to dissipate layer by layer along the thickness of the structure, thereby significantly improving the overall energy absorption efficiency and achieving effective control over peak impact loads.

[0041] This invention involves infusing an elastomeric material into the pores of a gradient metamaterial core, creating a composite interpenetrating structure between the metamaterial framework and the elastomeric material. Under impact loads, the elastomeric material can generate damping energy dissipation through viscoelastic deformation, while simultaneously providing lateral support to the metamaterial cells. This suppresses local buckling and sudden structural instability, making the crushing process more stable and improving the overall energy absorption capacity of the structure.

[0042] This invention uses a glass fiber reinforced composite material shell to encapsulate the metamaterial core. This shell not only provides the necessary overall stiffness and structural constraints, but also bears part of the load in the initial impact phase, thereby improving the initial load-bearing capacity and resistance to damage of the structure.

[0043] Furthermore, this invention utilizes additive manufacturing technology to integrally fabricate the curbstone structure, enabling the high-precision molding of complex gradient metamaterial structures. This method allows for continuous variation of cell geometric parameters, thereby increasing the degree of freedom in structural design and giving the curbstone's energy absorption performance strong designability and controllability.

[0044] This invention improves the weather resistance and anti-aging properties of glass fiber reinforced resin composite materials by adding UV-resistant additives, thereby extending the service life of curb stones.

[0045] In summary, this invention not only significantly improves the energy absorption performance of curb stones under vehicle impact, but also enables lightweight structure and designable mechanical properties, which is of great significance for improving the safety performance of road protection components. Attached Figure Description

[0046] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0047] Figure 1 The diagram shows the structure of a single basic cell in different states in this invention, where (a) is state one and (b) is state two.

[0048] Figure 2 This is a schematic diagram of the gradient Poisson's ratio;

[0049] Figure 3 The diagram shows a multilayer basic cell along the thickness direction, where (a) is a schematic cross-section and (b) is a three-dimensional view.

[0050] Figure 4 A three-dimensional schematic diagram of the core structure of a gradient Poisson's ratio metamaterial;

[0051] Figure 5 This is a cross-sectional view of the curbstone.

[0052] Figure 6 This is a schematic diagram of the overall structure of the curbstone;

[0053] Among them, 1-shell, 2-gradient Poisson's ratio metamaterial core structure, 3-rubber filler. Detailed Implementation

[0054] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. However, this is not the only description; all aspects not described in detail herein are based on conventional techniques in the art.

[0055] Example 1

[0056] A 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterials, such as Figure 6 As shown, it includes an outer shell 1, a gradient Poisson's ratio metamaterial core structure 2 disposed inside the outer shell, and a rubber filler 3 filling the pores of the core structure. In actual fabrication, the rubber filler 3 is filled into the interpenetrating pores of the gradient Poisson's ratio core through an injection process. The outer shell is used to provide overall structural stiffness and initial load-bearing capacity. The gradient Poisson's ratio metamaterial core structure is used to achieve the stepwise absorption of impact energy. The rubber filler 3 further dissipates impact energy through viscoelastic deformation, thereby forming a multi-level energy-absorbing structural system.

[0057] In this embodiment, the overall dimensions of the curbstone are: length 750 mm, thickness 200 mm, and height 350 mm.

[0058] The outer shell is a thin-walled structure, preferably with a wall thickness of about 5 mm, which is used to provide overall constraint and initial load-bearing capacity for the internal structure.

[0059] The gradient Poisson's ratio metamaterial core structure 2 consists of multiple basic cells arranged along a predetermined direction to form a three-dimensional lattice structure. The basic cells are concave hexagonal structural units, such as... Figure 1 As shown, multiple basic cells are arranged in space through a shared node method to form an interconnected three-dimensional lattice structure. By changing the geometric parameters of the basic cells, the structure can exhibit a controllable Poisson's ratio gradient distribution in space.

[0060] Geometric parameters include tilt angle α and cell link wall thickness t;

[0061] like Figure 1 As shown, the basic cell is a concave hexagonal structure. l represents the length of the inclined connecting rod that constitutes the cell, that is, the length of the center line of the inclined connecting rod between adjacent nodes. h represents the characteristic dimension of the cell in the vertical direction, which is the vertical distance between the upper and lower adjacent nodes of the cell, reflecting the structural scale of a single cell in this direction.

[0062] The tilt angle α refers to the angle between the inclined rods constituting the cell structure and the horizontal direction. The tilt angle α varies gradually along the thickness direction of the curbstone, realizing the overall structural performance transition from negative Poisson's ratio to positive Poisson's ratio. In the impact side region near the roadway, the tilt angle α of the basic cells is configured to exhibit negative Poisson's ratio characteristics, causing the structure to undergo lateral contraction under compression, thereby improving its resistance to intrusion and local load-bearing capacity. From the impact side region to the region away from the roadway, the tilt angle α of the basic cells gradually changes, causing the equivalent Poisson's ratio of the structure to gradually transition to positive Poisson's ratio characteristics, promoting the diffusion and distribution of loads within the structure. Through the above gradient transition, the entire structure exhibits a stable layer-by-layer crushing mode under impact, thereby achieving efficient energy absorption and peak load control. Layer-by-layer crushing refers to the fact that when the structure is subjected to impact load, due to the Poisson's ratio gradient set along the thickness direction, the negative Poisson's ratio cell layers near the impact side have relatively low stiffness and exhibit the characteristic of contracting towards the center under compression, thus preferentially becoming unstable and compacting to dissipate the initial impact energy. Only after the current cell layer is fully compacted (densified) can the load be effectively transferred to the subsequent positive Poisson's ratio gradient layers. This mechanism avoids instantaneous instability of the entire structure, ensures the smoothness of load transfer, and thus effectively reduces the peak impact force. In other words, under impact load, deformation first occurs in the low-stiffness negative Poisson's ratio cell layer near the impact side. This layer of cells absorbs energy through lateral contraction and bending deformation until it is fully compacted. Subsequently, the shock wave continues to propagate inward, triggering the instability deformation of the cells in the next gradient layer. Through the sequential "instability-compaction" cycle of each gradient layer, an ordered crushing sequence is formed in time and space, thereby achieving the gradual distribution of impact energy and smooth control of peak load.

[0063] Since the main impact loads generated by vehicles on the curb usually come from the direction of the road lane, that is, propagating along the thickness of the curb, the Poisson's ratio gradient is designed in this direction so that the structure can be optimized for the impact propagation path.

[0064] like Figure 3 , 4 As shown, the gradient Poisson's ratio metamaterial core structure employs a shared-node fusion connection method. The basic cells of adjacent layers in the longitudinal direction (thickness / gradient direction) are completely overlapped and fused together through their respective horizontal connecting segments. This connection method ensures that impact loads can be transmitted along the... The axial direction is smoothly transmitted, forming a continuous skeletal path along the thickness direction. Multiple concave hexagonal basic cells in the lateral / vertical (in-plane direction) directions overlap and share nodes through horizontal support segments at their apexes, constructing a three-dimensional spatial network. Because the concave hexagonal cells are open geometric units, and the internal spaces of each cell are not closed when arranged, the injected rubber material can freely permeate into every cell pore of the entire core structure under the drive of gravity or pressure. This design ensures that the elastomer, after filling, can form an interpenetrating structure with the material skeleton, thereby providing uniform viscoelastic damping support on a macroscopic scale and effectively suppressing local instability of the skeleton under impact loads.

[0065] Preferably, the tilt angle α varies along the gradient direction according to a preset functional relationship, which can gradually transition the cell equivalent Poisson's ratio from a negative value to a positive value. In this embodiment, the tilt angle... The following functional relationship must be satisfied:

[0066]

[0067] in, For the minimum tilt angle, For the maximum tilt angle, The coordinates along the gradient direction represent the specific coordinates from the impact surface inwards, with a value range of 0 to 200 mm. = 0 corresponds to the impact side closer to the road lane; = 200 mm corresponds to the internal region far from the impact side. Since the metamaterial core structure is composed of a finite number of cellular layers, therefore The actual values ​​of are discrete, and The number of values ​​should be the same as the number of layers set along the thickness direction of the basic cell (13 layers in this embodiment).

[0068] This represents the total length along the gradient direction. , For gradient exponent, This is the gradient adjustment coefficient. =0.2, used to adjust the rate of change of cell tilt angle in the gradient direction. Its physical meaning can be interpreted as: adjusting the rate of change of cell tilt angle in the structural gradient direction, controlling the crushing propagation sequence of the structure under impact load, and optimizing energy absorption distribution. When = 0, the gradient function is a standard power function gradient, and the structure absorbs energy uniformly. When the gradient is greater than 0, the initial gradient change is relatively gradual, which can reduce the peak impact force. When the gradient is less than 0, the gradient changes rapidly in the early stage, which can improve the structure's resistance to intrusion; over-adjusting the gradient exponent... The crush propagation mode of the control structure during the impact process.

[0069] α > 0 (positive Poisson's ratio): The cell element exhibits a standard convex hexagonal shape; under compression, the structure expands outwards. α < 0: The cell element exhibits a distinctly concave hexagonal shape; under compression, the structure contracts towards the center. =-20°.

[0070] Through the above functional relationship, the cell tilt angle is gradually changed from -20° to 20°, thereby causing the structural equivalent Poisson's ratio to gradually transition from a negative value to a positive value.

[0071] In the region near the impact side, the negative Poisson's ratio structure will generate lateral contraction under compression, thereby improving the structure's resistance to intrusion; in the internal region away from the impact side, the positive Poisson's ratio structure can promote the diffusion of load within the structure, enabling the structure to form a stable layer-by-layer crushing energy absorption mode during impact.

[0072] The projection length of the basic cell in the gradient direction (i.e., the curb thickness direction) is defined as the cell feature size; the cell feature size in the gradient direction is preferably 10 mm to 20 mm, more preferably about 15 mm. In this embodiment, a total of 13 cell structures are provided along the 200 mm thickness direction of the curb.

[0073] With a curb thickness of 200 mm, the metamaterial core contains at least 8 basic cell layers along the gradient direction, preferably 10 to 20 basic cell layers. A sufficient number of cell layers ensures a continuous Poisson's ratio gradient distribution, thus forming a stable progressive crushing energy absorption mode. Here, "layer" refers to the number of physical units continuously arranged along the thickness direction. Setting at least 8 layers (preferably 10 to 20 layers) ensures sufficient discrete sampling accuracy of the Poisson's ratio gradient. A sufficient number of layers allows each cell layer to undergo a "instability-compaction" cycle sequentially according to a preset gradient order as the shock wave propagates into the structure, thereby forming a stable, progressive, layer-by-layer crushing on a macroscopic scale and effectively controlling the peak load.

[0074] The three-dimensional lattice structure contains interconnected porous spaces. Rubber fillers are injected into these porous spaces, creating a composite interpenetrating structure between the gradient Poisson's ratio metamaterial core framework and the rubber fillers. The rubber fillers can undergo viscoelastic deformation under impact loads, thereby dissipating energy and providing lateral support to the metamaterial cells to suppress local buckling and improve structural crush stability.

[0075] Both the outer shell and the gradient Poisson's ratio metamaterial core structure are printed from glass fiber reinforced thermoplastic resin composite material, which can be manufactured using additive manufacturing technology. The glass fiber reinforced thermoplastic resin composite material includes a resin matrix and glass fibers. The resin matrix is ​​PLA or PETG, and the glass fiber content is 20% by mass, with a fiber length of 0.2 mm to 0.8 mm. The glass fiber reinforced thermoplastic resin composite material also includes UV absorbers, which are benzotriazole or benzophenone UV absorbers, added at 1.5% of the resin matrix mass.

[0076] A method for preparing the above-mentioned 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterials includes:

[0077] S1, Raw material preparation:

[0078] PLA resin was selected as the resin matrix, and glass fiber was added to the resin matrix as a reinforcing material and UV-resistant additive. PLA resin particles, glass fiber and UV-resistant additive were added to a high-speed mixer and mixed for 10 to 20 minutes to ensure uniform dispersion of the components, thereby improving the UV aging resistance and long service life of the curbstone. Subsequently, composite material particles for 3D printing were prepared by extrusion granulation equipment.

[0079] S2, Structural Modeling and Printing Parameter Settings:

[0080] A three-dimensional model was established based on the dimensions of the curbstone structure, and a gradient Poisson's ratio metamaterial core structure was constructed inside the shell. The core structure consists of multiple basic cells arranged along a predetermined direction to form a three-dimensional lattice structure. The basic cells are concave hexagonal structural units, and the basic cells are arranged along the thickness direction of the curbstone to form a gradient structure.

[0081] Set the printing parameters as follows:

[0082] Nozzle temperature: 210 ℃, printing platform temperature: 60 ℃, print layer thickness: 0.3 mm, fill rate: 100%, printing speed: 40 mm / s;

[0083] The outer shell and the internal core structural skeleton are integrated and printed as a whole using fused deposition modeling (FDM) 3D printing equipment.

[0084] The outer shell and the metamaterial core structure are integrally printed, with their connection interface being an integrated interface in the molten state of the material, requiring no auxiliary connectors or adhesive layers. The curbstone shell and internal metamaterial skeleton of this invention are not fabricated separately and then joined together; instead, they are integrally and continuously printed using fused deposition modeling (FDM) technology. Because the shell and core use the same glass fiber reinforced composite material, and the nozzle continuously extrudes along a computer-defined slicing path during printing, the two are bonded at their interface through a high-temperature molten state.

[0085] S3, Elastomer Filler:

[0086] Elastomer material was injected into the pores of the printed metamaterial core structure. The elastomer material was a two-component polyurethane rubber with a Shore hardness of A70.

[0087] like Figure 5 As shown, the outer shell 1 has an injection opening at its bottom that communicates with the internal gradient Poisson's ratio metamaterial core structure 2, used to inject elastomeric material into the pore space of the three-dimensional lattice structure. During the injection process, the elastomeric material can enter through the injection opening under the action of gravity or external pressure, and gradually fill the entire metamaterial core structure along the connected pores, thereby achieving full filling. After the elastomeric filling is completed, the injection opening can be sealed by additive manufacturing or by setting a sealing plate, so that the outer shell forms an integral closed structure; or in some embodiments, the injection opening can also be retained as a functional opening for structural venting or regulating internal stress.

[0088] Component A and component B are mixed at a mass ratio of 1:1 and then subjected to vacuum degassing.

[0089] Component A is an isocyanate component, and component B is a polyol component. Component A mainly consists of polyisocyanate monomers, whose primary function is to provide active isocyanate groups that react with the hydroxyl groups in component B to form crosslinking groups. Component B mainly consists of polyether polyols or polyester polyols, and contains appropriate amounts of chain extenders, catalysts, and defoamers. This component determines the flexibility, Shore hardness, and viscoelastic energy dissipation characteristics of the cured rubber.

[0090] S4, Curing process:

[0091] After infusion, allow it to stand at room temperature for 24 hours to cure. If necessary, it can be post-cured at 60 °C for 2 hours to improve the interfacial bonding strength between the elastomer material and the metamaterial framework.

[0092] The final result was a composite energy-absorbing curbstone structure with a gradient Poisson's ratio metamaterial core.

[0093] To verify the performance advantages of the structure of the present invention, a quasi-static compression test was conducted to compare the curbstone structure of this embodiment with traditional concrete curbstone and ordinary FRP hollow beam structure. The typical performance indicators are shown in Table 1.

[0094] Table 1. Comparison of performance of curb stones with different structures

[0095] Example 2

[0096] A 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterial differs from Example 1 in that the gradient Poisson's ratio structure has a variation function.

[0097] In this embodiment, the cell tilt angle varies along the thickness direction according to the following relationship:

[0098]

[0099] Compared with Example 1, this example adopts a quadratic function gradient structure, where k=0.1.

[0100] This structure makes the change in Poisson's ratio more gradual, resulting in a more uniform deformation propagation process under impact.

[0101] The remaining structural parameters are consistent with those in Example 1, including: curbstone size, number of cells, shell material, elastomer material, and printing process parameters. By changing the gradient function, the crushing propagation speed and energy absorption mode of the structure can be controlled.

[0102] Example 3

[0103] A 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterial differs from Example 1 in that the rubber filler 3 filling the pores of the core structure is a silicone rubber elastomer with a Shore hardness of A50.

[0104] Silicone rubber materials have good temperature resistance, aging resistance and high viscoelastic damping properties.

[0105] Under impact loads, this material can generate a significant energy dissipation effect through viscoelastic deformation.

[0106] The remaining structural parameters are consistent with those of Example 1.

[0107] By changing the type of elastomer material, the energy absorption performance of the structure can be optimized under different environmental conditions.

[0108] Embodiment 1 of the present invention employs a cubic function gradient structure, which can form a strong structural constraint in the early stage of impact, thereby improving the structure's resistance to intrusion.

[0109] Example 2 uses a quadratic function gradient structure, which makes the cell structure change more gradually and can form a more uniform deformation propagation mode under impact.

[0110] Example 3 modifies the elastomer filling material based on the structure of Example 1, so that the structure can further dissipate impact energy through the viscoelastic deformation of the elastomer during the impact process.

[0111] Among them, Example 2, which uses a quadratic function gradient, has a lower peak impact force but a larger deformation, indicating that it has a softer buffering characteristic; Example 3, which uses high-damping silicone rubber, achieves a larger deformation under similar peak forces, indicating that its viscoelastic energy dissipation effect is more significant.

[0112] Typical mechanical properties of each embodiment are shown in Table 2.

[0113] Table 2 Performance Comparison of Examples

[0114] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A 3D-printed composite energy-absorbing curbstone based on a gradient Poisson's ratio metamaterial, characterized in that, It includes an outer shell, a gradient Poisson's ratio metamaterial core structure disposed inside the outer shell, and a rubber filler filling the pores of the core structure; The gradient Poisson's ratio metamaterial core structure consists of multiple basic cells arranged along a predetermined direction to form a three-dimensional lattice structure. The basic cells are concave hexagonal structural units. Multiple basic cells are arranged in space through a common node to form an interconnected three-dimensional lattice structure. By changing the geometric parameters of the basic cells, the structure can exhibit a controllable Poisson's ratio gradient distribution in space.

2. The 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterial according to claim 1, characterized in that, Geometric parameters include tilt angle α and cell link wall thickness t; The tilt angle α refers to the angle between the inclined rods constituting the cell structure and the horizontal direction. The tilt angle α varies gradually along the thickness direction of the curbstone, realizing the overall structural performance transition from negative Poisson's ratio to positive Poisson's ratio. In the impact side region close to the roadway, the tilt angle α of the basic cell is configured to exhibit negative Poisson's ratio characteristics, causing the structure to undergo lateral contraction under compression. From the impact side region to the region away from the roadway, the tilt angle α of the basic cell gradually changes, causing the equivalent Poisson's ratio of the structure to gradually transition to positive Poisson's ratio characteristics, thereby promoting the diffusion and distribution of loads within the structure.

3. The 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterial according to claim 2, characterized in that, The tilt angle α varies along the gradient direction according to a preset functional relationship. The following functional relationship must be satisfied: in, For the minimum tilt angle, For the maximum tilt angle, The coordinates are along the gradient direction, representing the specific coordinates from the impact surface inwards. This represents the total length along the gradient direction. , For gradient exponent, This is the gradient adjustment coefficient, used to adjust the rate of change of the cell tilt angle along the gradient direction. When = 0, the gradient function is a standard power function gradient, and the structure absorbs energy uniformly. When the gradient is greater than 0, the initial gradient change is relatively gradual, which can reduce the peak impact force. When the gradient is less than 0, the gradient changes rapidly in the early stage, which can improve the structure's resistance to intrusion; over-adjusting the gradient exponent... The crush propagation mode of the control structure during the impact process.

4. The 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterial according to claim 3, characterized in that, The projection length of the basic cell in the gradient direction is defined as the cell characteristic size; when the cell characteristic size is 10 to 20 mm, the cell link wall thickness t is 2 to 3 mm to achieve a balance between structural strength and energy absorption performance.

5. The 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterial according to claim 4, characterized in that, With a curb thickness of 200 mm, the metamaterial core contains no less than 8 basic cell layers in the gradient direction, preferably 10 to 20 basic cell layers.

6. The 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterial according to claim 5, characterized in that, The interior of the three-dimensional lattice structure consists of interconnected porous spaces. Rubber fillers are injected into these porous spaces, creating a composite interpenetrating structure between the gradient Poisson's ratio metamaterial core structure framework and the rubber fillers.

7. The 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterial according to claim 6, characterized in that, The outer shell and the gradient Poisson's ratio metamaterial core structure are both printed from glass fiber reinforced thermoplastic resin composite material; the glass fiber reinforced thermoplastic resin composite material includes a resin matrix and glass fibers, the resin matrix is ​​PLA or PETG, the mass content of glass fibers is 10% to 35%, and the length of glass fibers is 0.2 mm to 1 mm.

8. The 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterial according to claim 7, characterized in that, Glass fiber reinforced thermoplastic resin composites also include UV-resistant additives, which are benzotriazole or benzophenone UV absorbers, and the amount added is 0.5% to 2.0% of the resin matrix mass.

9. The 3D-printed composite energy-absorbing curbstone based on gradient Poisson's ratio metamaterial according to claim 8, characterized in that, The outer shell has a thin-walled structure with a wall thickness of 3 to 8 mm.

10. A method for preparing a 3D-printed composite energy-absorbing curbstone based on a gradient Poisson's ratio metamaterial as described in claim 9, characterized in that, include: S1, Raw material preparation: PLA resin was selected as the resin matrix, and glass fiber was added to the resin matrix as a reinforcing material and UV-resistant additive. PLA resin particles, glass fiber and UV-resistant additive were added to a high-speed mixer and mixed for 10 to 20 minutes to ensure uniform dispersion of the components. Then, composite material particles for 3D printing were prepared by extrusion granulation equipment. S2, Structural Modeling and Printing Parameter Settings: A three-dimensional model was established based on the dimensions of the curbstone structure, and a gradient Poisson's ratio metamaterial core structure was constructed inside the shell. The core structure consists of multiple basic cells arranged along a predetermined direction to form a three-dimensional lattice structure. The basic cells are concave hexagonal structural units, and the basic cells are arranged along the thickness direction of the curbstone to form a gradient structure. Set printing parameters, including nozzle temperature, printing platform temperature, printing layer thickness, infill rate and printing speed, and perform overall printing through fused deposition modeling 3D printing equipment to integrate the outer shell with the internal core structural skeleton. S3, Elastomer Filler: After printing, the core structure of the metamaterial is filled with an elastomer material, which is rubber, to fully fill the entire three-dimensional lattice structure. S4, Curing process: After the injection is completed, allow it to stand at room temperature for 24 hours to cure.

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