Bionic shellfish energy absorption box based on negative poisson's ratio structure improvement and preparation method thereof

Abstract

The application discloses a kind of based on negative poisson's ratio structure improvement biomimetic shellfish energy absorption box and preparation method thereof, it is related to automobile body safety structure material and crash protection technical field, the application is first based on the topological optimization concept of negative poisson's ratio honeycomb structure, traditional energy absorption box honeycomb structure is improved design, imitates shellfish dislocation feature, and improved honeycomb structure is structured, so that the energy absorption efficiency of structure, deformation uniformity and bearing capacity can be greatly improved, then based on the idea of synergistic effect of heterogeneous composite structure, the preparation of TC4-PE biomimetic honeycomb heterogeneous structure is realized, and heterogeneous interface is closely combined, and filling effect is good, effectively realize the synergistic trade-off of lightweight and high energy absorption, high strength and high toughness.In the face of typical service conditions such as automobile frontal crash, side crash, the biomimetic honeycomb heterogeneous structure constructed by the application can exhibit more excellent energy absorption characteristics and crushable deformation controllability.

Description

Technical Field

[0001] This invention relates to the field of automotive body safety structure materials and collision protection technology, specifically to a biomimetic shell energy-absorbing box based on a negative Poisson's ratio structure and its preparation method. Background Technology

[0002] As a core component of the vehicle collision protection system, the automotive energy-absorbing box primarily undertakes the functions of energy absorption, impact buffering, and vehicle body protection during a collision. Its performance directly determines the occupant safety level during a collision. Simultaneously, to adapt to the development trend of lightweight and high safety in new energy vehicles, it must balance multiple core requirements such as lightweight design, high energy absorption, impact resistance, controllable deformation, and vibration and noise reduction. Currently, the research and development of automotive energy-absorbing boxes still faces many technical bottlenecks. Traditional energy-absorbing boxes mostly use low-carbon steel or aluminum alloys as core materials. These materials have limited specific strength and specific energy absorption, making it difficult to meet the increasingly stringent collision safety requirements while achieving lightweight design. Furthermore, traditional energy-absorbing boxes often employ thin-walled cylindrical, ordinary honeycomb, or porous structural designs, manufactured through traditional processes such as stamping and extrusion. This structural limitation makes them prone to problems such as excessively high initial peak force and stress concentration upon impact, leading to early structural failure. Additionally, their energy absorption value and efficiency are relatively low, lacking stable progressive collapse behavior during deformation, resulting in uneven energy absorption. Overall, their performance is insufficient to meet the collision protection needs of modern vehicles.

[0003] As a novel topological structure, the negative Poisson's ratio structure exhibits significant advantages in the field of automotive energy-absorbing boxes. Compared to traditional honeycomb and porous structures, it possesses unique geometric characteristics, enabling uniform energy dissipation under stress, effectively reducing the initial peak impact force, and avoiding stress concentration. It also boasts excellent deformation controllability, allowing for optimization of the energy absorption path through structural parameter adjustments, significantly improving energy absorption value and efficiency. Furthermore, its adjustable porosity results in outstanding lightweighting, supporting overall vehicle weight reduction and overcoming the shortcomings of traditional energy-absorbing box structures, such as insufficient mechanical performance and limited functionality. However, existing negative Poisson's ratio structures still have significant drawbacks. Single negative Poisson's ratio structures are often formed from a single metal material, limiting the scope for mechanical performance control. This makes it difficult to simultaneously meet the synergistic requirements of high load-bearing capacity, high toughness, and vibration and noise reduction. For example, pure metal negative Poisson's ratio structures have poor damping characteristics, insufficient energy dissipation and vibration damping capabilities, and are prone to fatigue damage during long-term service, failing to fully meet the complex collision protection requirements of automotive energy-absorbing boxes.

[0004] Over millions of years of evolution, natural biocomposite materials have developed highly efficient mechanical structural design strategies, with biomimetic structures being particularly advantageous. These strategies provide important insights for optimizing the structure of automotive energy-absorbing boxes, with the microstructure of shellfish being a prime example. Shellfish shells possess unique microscopic interlaminar dislocation characteristics. This staggered arrangement of layers avoids localized stress concentration while achieving uniform stress balance. This biomimetic design concept perfectly matches the mechanical requirements of automotive energy-absorbing boxes during collisions, providing a native biomimetic paradigm for the structural design of high-performance energy-absorbing boxes.

[0005] To address the performance limitations of single structures and materials, heterogeneous composite structures have become a crucial research direction for the high-performance development of automotive energy-absorbing boxes. Their core advantage lies in the synergistic coupling of materials with different properties, achieving complementary and synergistic performance, thus overcoming the bottleneck of single materials being unable to meet multi-dimensional requirements. TC4 titanium alloy, as a typical high-performance structural metal, has a density of only 4.51 g / cm³, combining lightweight and high strength. Its specific strength is far higher than traditional automotive aluminum alloys (such as 6061 and 7075), with tensile strength exceeding 860 MPa and yield strength exceeding 795 MPa. It also possesses excellent fatigue resistance, meeting the core requirements of high load-bearing capacity and high stiffness for automotive energy-absorbing boxes. Furthermore, it can absorb a large amount of energy during plastic deformation, laying the foundation for excellent crashworthiness. However, TC4 titanium alloy itself has low plasticity and toughness, poor damping characteristics (damping factor typically below 0.001), insufficient energy dissipation and vibration damping capabilities, and stress concentration is prone to occur during single molding, making it difficult to achieve multi-functional synergy of vibration reduction, protection, and load bearing. PE (polyethylene, such as HDPE) has a density of only 0.95 g / cm³, making it lightweight and having a damping characteristic far superior to metal materials, with a damping factor of 0.01~0.1. It has excellent impact energy dissipation and micro-vibration buffering capabilities, while also having strong plastic deformation capacity and wear resistance, which can effectively make up for the shortcomings of TC4 titanium alloy in vibration reduction and insufficient toughness. However, HDPE itself has low strength and elastic modulus, with a tensile strength of only 20~30 MPa and an elastic modulus of about 0.8~1.5 GPa. When molded alone, it cannot meet the requirements of high load-bearing capacity and high rigidity of energy-absorbing boxes, and therefore cannot be used as a core load-bearing structure.

[0006] In summary, existing automotive energy-absorbing boxes have significant limitations in material selection and structural design. Traditional materials and structures struggle to simultaneously meet multiple requirements such as lightweighting, high energy absorption, and impact resistance. The performance deficiencies of single negative Poisson's ratio structures and single materials restrict the improvement of the overall performance of energy-absorbing boxes. However, the complementary properties of TC4 and PE materials provide a foundation for the development of heterogeneous structures. By combining the improved design of negative Poisson's ratio honeycomb structures with the advantages of shellfish biomimetic structures, synergistic effects can be achieved through heterogeneous composites. This is expected to break through the technical bottlenecks of existing automotive energy-absorbing boxes and develop high-performance energy-absorbing box structures that meet the collision protection needs of modern automobiles. Therefore, conducting research on TC4-PE heterogeneous automotive energy-absorbing boxes based on the improvement of negative Poisson's ratio honeycomb structures has significant practical significance and application value. Summary of the Invention

[0007] To address the aforementioned problems in existing technologies, the present invention aims to design a biomimetic shell-like energy-absorbing box based on a negative Poisson's ratio structure and its preparation method. This invention solves the technical bottleneck of existing automotive energy-absorbing boxes, which struggle to simultaneously meet the requirements of lightweight, high load-bearing capacity, impact resistance, vibration reduction, and controllable deformation. It provides high-performance structural material support for automotive collision protection, occupant safety, and the lightweight development of new energy vehicles.

[0008] The specific plan is as follows: The first aspect of the present invention provides a biomimetic shellfish energy-absorbing box based on a modified negative Poisson's ratio structure. The structure of the energy-absorbing box is a modified honeycomb structure, which includes multiple negative Poisson's ratio honeycomb unit layers. All negative Poisson's ratio honeycomb unit layers are stacked sequentially along the thickness direction. The negative Poisson's ratio honeycomb unit layers are formed by multiple negative Poisson's ratio honeycomb cells arranged in a periodic array in the same plane. Between two adjacent negative Poisson's ratio cellular cell layers, there is a dislocation offset in the first direction in a plane parallel to the layer, causing the upper negative Poisson's ratio cell layer to be translated relative to the lower layer by a preset step size. The dislocation offset increases layer by layer along the stacking direction, forming a cumulative offset, so that the entire energy-absorbing box presents a stepped shape on the side.

[0009] Preferably, the improved honeycomb structure uses TC4 titanium alloy to form the skeleton, and the pores inside the skeleton are filled with PE material to form a biomimetic honeycomb heterostructure.

[0010] Preferably, the plurality of negative Poisson's ratio cell cells are arranged in an array parallel to and perpendicular to the first direction.

[0011] Preferably, the negative Poisson's ratio honeycomb cell includes two symmetrical and parallel bottom surfaces, the same side of the two bottom surfaces is connected by two connected inclined surfaces, and the two inclined surfaces are inclined inward, and the connection point of the two inclined surfaces on the same side is externally connected by ribs. In the direction parallel to the first direction, the ribs between two adjacent negative Poisson's ratio cells are connected; in the direction perpendicular to the first direction, the bottom surfaces between two adjacent negative Poisson's ratio cells are connected.

[0012] Preferably, the dislocation offsets of adjacent negative Poisson's ratio cellular cell layers vary along the stacking direction in an arithmetic sequence.

[0013] Preferably, all the frames of the energy-absorbing box have the same wall thickness.

[0014] The second aspect of this invention provides a method for preparing the biomimetic mollusk energy-absorbing box based on the negative Poisson's ratio structure improvement described in the first aspect of this invention, comprising the following steps: S1: Based on the dislocation characteristics of mollusks, an improved honeycomb structure is designed on the basis of the traditional negative Poisson's ratio honeycomb structure; S2: Based on additive manufacturing technology, the improved honeycomb structure from step S1 is printed and molded as a model of the energy-absorbing box.

[0015] Preferably, in step S2, a modified honeycomb structure is prepared using TC4 titanium alloy based on additive manufacturing technology, serving as a model for the energy-absorbing box.

[0016] Preferably, in step S2, based on additive manufacturing technology, a modified honeycomb structure skeleton is prepared using TC4 titanium alloy, and then PE is filled into the pores of the skeleton using a powder filling-hot melting vacuum insulation composite preparation process to form a biomimetic honeycomb heterostructure, which serves as a model for the energy-absorbing box.

[0017] Preferably, the powder particle size of the TC4 titanium alloy is 15~53 μm.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: Based on the traditional negative Poisson's ratio honeycomb structure, the improved honeycomb structure, which is designed by imitating the dislocation characteristics of shellfish, significantly improves the load-bearing performance compared with the traditional honeycomb structure and the ordinary negative Poisson's ratio honeycomb structure by suppressing the local negative Poisson's ratio effect. The energy absorption capacity and specific energy absorption are greatly optimized. At the same time, the structural deformation mode is effectively improved and the stress distribution is more uniform. It can effectively avoid the local failure of the energy absorption box during car collisions and improve the energy absorption efficiency. The biomimetic honeycomb heterostructure prepared by this invention further improves the structural load-bearing capacity and deformation stability through the beneficial effects of the interaction between soft and hard phase interfaces, avoids sudden fracture of the structure under collision load, ensures that the energy absorption process is stable and controllable, and is suitable for the actual working conditions of automotive energy absorption boxes. The introduction of HDPE phase and the synergistic effect of heterogeneous structure not only enhance the energy absorption and load-bearing performance of the structure, but also achieve a better synergistic vibration reduction effect due to its excellent damping characteristics. It improves the fatigue resistance of the structure, effectively alleviates the vibration transmission during the car collision process, avoids the complete destruction and failure of the energy absorption box structure, and provides more reliable protection for the main body protection and passenger safety. Compared with traditional metal energy absorption box structure and simple composite structure, it has more comprehensive functionality and practical value, and is suitable for the development needs of lightweight and high safety of new energy vehicles. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the improved honeycomb structure and the biomimetic mapping of the biomimetic honeycomb heterostructure of the present invention, wherein... Figure 1 (a) A schematic diagram showing the features of honeycomb + molluskaloid dislocations. Figure 1 (b) A schematic diagram showing the brick-and-mortar structure of shellfish. Figure 1 (c) shows a schematic diagram of three types of improved honeycomb structures. Figure 1 (d) shows a schematic diagram of three types of biomimetic honeycomb heterostructures; Figure 2 The flowchart shows the modeling process for a traditional negative Poisson's ratio (NPHS) honeycomb structure. Figure 2 (a) shows the flowchart for constructing the THS. Figure 2 (b) shows the flowchart for constructing NPHS based on THS; Figure 3 A flowchart illustrating the fabrication process of traditional negative Poisson's ratio (NPHS) honeycomb heterostructures (THHS) using a powder-filling-hot-melting vacuum insulation composite process. Figure 3 (a) is a schematic diagram of the NPHS structure. Figure 3 (b) shows a schematic diagram of the structure in which HDPE powder is filled into the TC4 skeleton, placed in a mold, and pressed using a counterweight. Figure 3 (c) shows a schematic diagram of the HDPE powder impregnation process. Figure 3 (d) A schematic diagram of the completed THHS structure; Figure 4 These are three types of improved cellular structures—IHSA, IHSB, and IHSC—formed by applying different dislocation offset strategies to the traditional cellular structure THS, along with their corresponding biomimetic cellular heterostructures BHHSA, BHHSB, and BHHSC. Figure 4 (a) shows a schematic diagram of the formation of IHSA and BHHSA. Figure 4 (b) shows a schematic diagram of the formation of IHSB and BHHSB. Figure 4 (c) shows a schematic diagram of the formation of IHSC and BHHSC; Figure 5The finite element model mesh rendering results are shown for NPHS, IHSA, IHSB, IHSC, and THHS, BHHSA, BHHSB, and BHHSC. Figure 5 (a) shows the finite element model mesh of NPHS. Figure 5 (b) shows the mesh diagram of the finite element model of IHSA. Figure 5 (c) shows the finite element model mesh of IHSB. Figure 5 (d) shows the mesh diagram of the finite element model of IHSC. Figure 5 (e) shows the finite element model mesh of THHS. Figure 5 (f) represents the finite element model mesh of BHHSA. Figure 5 (g) represents the finite element model mesh of BHHSB. Figure 5 (h) represents the finite element model mesh of BHHSC; Figure 6 The compression mechanical curves are for NPHS, IHSA, IHSB, IHSC and THHS, BHHSA, BHHSB, BHHSC. Figure 7 The energy absorption curves are for NPHS, IHSA, IHSB, IHSC and THHS, BHHSA, BHHSB, BHHSC. Figure 8 The specific energy absorption curves are for NPHS, IHSA, IHSB, IHSC and THHS, BHHSA, BHHSB, BHHSC. Figure 9 The image shows the deformation mode contour maps for NPHS, IHSA, IHSB, and IHSC. Figure 9 (a) shows the stress contour plot of NPHS. Figure 9 (b) shows the stress contour plot of IHSA. Figure 9 (c) shows the stress contour plot of the IHSB. Figure 9 (d) shows the stress contour plot of the IHSC; Figure 10 The following are the deformation mode cloud maps for THHS, BHHSA, BHHSB, and BHHSC, where... Figure 10 (a) shows the stress contour plot of THHS. Figure 10 (b) shows the stress contour plot of BHHSA. Figure 10 (c) shows the stress contour plot of BHHSB. Figure 10 (d) shows the stress contour plot of BHHSC; Figure 11 This is a comparison diagram showing the impact resistance of a traditional automotive energy-absorbing box and the automotive energy-absorbing box of this invention after being subjected to an impact. Figure 11 (a) shows the impact resistance of a traditional automotive energy-absorbing box. Figure 11 (b) shows the impact resistance effect of the automotive energy-absorbing box using the improved honeycomb structure of the present invention. Figure 11 (c) shows the impact resistance effect of the automotive energy-absorbing box using the biomimetic honeycomb heterostructure of the present invention.

[0020] The reference numerals in the accompanying drawings of this invention are as follows: 11. Traditional honeycomb unit; 1. Traditional honeycomb structure; 21. Traditional negative Poisson's ratio honeycomb structure; 2. Traditional honeycomb heterogeneous structure; 31. Modified honeycomb structure type A; 3. Bionic honeycomb heterogeneous structure type A; 41. Modified honeycomb structure type B; 4. Bionic honeycomb heterogeneous structure type B; 51. Modified honeycomb structure type C; 5. Bionic honeycomb heterogeneous structure type C; 100. Counterweight; 200. TC4 skeleton; 300. Mold. Detailed Implementation

[0021] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0022] Example 1: This embodiment discloses a biomimetic shellfish energy-absorbing box based on a negative Poisson's ratio structure, such as... Figure 1 As shown, the energy-absorbing box adopts a modified honeycomb structure, which is modeled after the interlayer dislocation characteristics of mollusks and is an improvement on the traditional negative Poisson's ratio honeycomb structure 21. The modified honeycomb structure includes multiple negative Poisson's ratio honeycomb unit layers, which are formed by a periodic array of multiple negative Poisson's ratio honeycomb cells in the same plane.

[0023] The negative Poisson's ratio honeycomb cell includes two symmetrical and parallel bases. The same side of the two bases is connected by two connected inclined planes, and the part where the two inclined planes are connected is inclined inward. The external connection of the connection point of the two inclined planes on the same side is a rib parallel to the base.

[0024] When subjected to axial tension, a negative Poisson's ratio structure expands laterally perpendicular to the direction of tension; when subjected to compression, it contracts laterally. This characteristic gives it unique mechanical response properties under stress; upon impact, the material tends to concentrate at the point of impact, resulting in greater compressive and shear resistance compared to a positive Poisson's ratio structure.

[0025] Multiple negative Poisson's ratio cell units are arranged in an array parallel to the first direction (i.e., the X-axis direction in the figure) and perpendicular to the first direction (i.e., the Z-axis direction in the figure).

[0026] All negative Poisson's ratio cellular cell layers are stacked sequentially along the thickness direction, which is the Y-axis direction in the attached figure. Between two adjacent negative Poisson's ratio cellular cell layers, in a plane parallel to the layer of the negative Poisson's ratio cellular cell layer, there is a dislocation offset along a first direction, causing the upper layer of negative Poisson's ratio cellular cell layer to translate relative to the lower layer by a predetermined step size. In this embodiment, the first direction is the X-axis direction. The dislocation offset increases layer by layer along the stacking direction (i.e., the Y-axis direction in the attached figure), forming a cumulative offset, so that the entire energy-absorbing box presents a stepped shape in the side, similar to the interlayer dislocation characteristics of a molluskine shell.

[0027] The dislocation offsets of adjacent negative Poisson's ratio cellular cell layers vary in an arithmetic sequence along the stacking direction. For example, the offset distance between the second negative Poisson's ratio cellular cell layer and the first negative Poisson's ratio cellular cell layer is s1, the offset distance between the third negative Poisson's ratio cellular cell layer and the first negative Poisson's ratio cellular cell layer is 2s1, the offset distance between the fourth negative Poisson's ratio cellular cell layer and the first negative Poisson's ratio cellular cell layer is 3s1, and so on.

[0028] The above-mentioned method for preparing the biomimetic shellfish energy-absorbing box based on the negative Poisson's ratio structure includes the following steps: S1: Based on the dislocation characteristics of shellfish, an improved honeycomb structure is designed on the basis of the traditional negative Poisson's ratio honeycomb structure 21. The improved honeycomb structure is constructed using CAD software and 3D modeling software Solidworks.

[0029] S2: Save the improved honeycomb structure from step S1 as an STL format file required by the additive manufacturing equipment, and then import it into the additive manufacturing equipment. Based on selective laser melting (SLM) technology, the improved honeycomb structure is prepared using TC4 titanium alloy.

[0030] The TC4 titanium alloy powder used in step S2 has a particle size of 15~53 μm, the laser power is 180 W, the scanning speed is 800 mm / s, the layer thickness is 20 μm, and the spacing is 60 μm. This printing strategy has been studied and confirmed to be able to prepare lattice structures with an accuracy of more than 0.2 mm.

[0031] See Figure 2 and Figure 4 As shown, the construction process of the improved cellular structure model is as follows: 1. First, construct negative Poisson's ratio cell cells.

[0032] The negative Poisson ratio honeycomb cell uses the traditional honeycomb unit structure (THUS), and its modeling process is as follows: First, using the 3D modeling software Solidworks, the following is drawn based on the front reference plane: Figure 2 The hexagonal blue honeycomb sketch outline is shown. Angle OAB (points O, A, and B are located at the center of the sketch) is set to α, where α equals 75°. Points C and D are obtained by extending outwards from the center points A and B, respectively. Connecting AC and BD yields the final honeycomb sketch. The overall dimension of the honeycomb sketch along the X-axis is 'a', which is 5 mm; along the Y-axis is 'b', which is 5 mm; and along the Z-axis is 'c', which is 5 mm. Based on the honeycomb sketch outline, a thin-wall extrude command is performed. The extrude feature uses symmetrical extrude, and the wall thickness is set to T, which equals 0.3 mm. The final result is a traditional honeycomb unit 11, with an overall size of 5×5×5 mm.

[0033] 2. Based on the above-mentioned traditional honeycomb cell 11, a traditional honeycomb structure 1 (abbreviated as THS) is constructed.

[0034] Based on the above-mentioned traditional cellular cell 11, multiple solid linear arrays are performed. The first array direction is the positive X-axis with 4 arrays, and the second array direction is the negative X-axis with 3 arrays (forming a row of 7 cells). After combining the solids, a second solid array is performed, with 3 solid arrays along the Z-axis and 4 solid arrays along the Y-axis. The solids obtained at this time are combined to obtain the traditional cellular structure 1. Subsequent dislocation strategies are all improved based on the traditional cellular structure 1.

[0035] 3. Based on the above traditional cellular structure 1, an improved cellular structure is constructed.

[0036] The aforementioned traditional honeycomb structure 1 is subjected to a progressive dislocation offset along the Y-axis (four rows in total, three rows after dislocation). The negative Poisson's ratio honeycomb unit layer in the first row remains stationary, while the remaining three rows are all subjected to solid displacement commands along the X-axis. Then, a stretch cut operation is performed to delete all beam entities except those in the stretch cut contour and any suspended beams, avoiding errors in subsequent printing and simulation. Specifically, as follows... Figure 2 As shown, draw the required extrusion cut profile (this sketch is drawn based on the top reference plane, and the sketch profile is fixed to avoid subsequent errors). The extrusion cut sketch profile is based on the previous C and D points, and a 15×15 mm profile is drawn using a rectangular wireframe diagram CDFE (to ensure that the subsequent cut is a 15×15×15 mm sample). Finally, perform the extrusion cut command (reverse side cut) and combine the remaining solid parts to obtain a modified honeycomb structure with a uniform wall thickness and a cube shape.

[0037] The improved honeycomb structure in this embodiment combines the advantages of interlaminar dislocations in mollusks. This interlaminar dislocation arrangement can effectively prevent the initiation and propagation of cracks during load-bearing. When the structure is subjected to impact loads, the interlaminar dislocations can disperse stress through their own slippage, disperse local stress, avoid local stress concentration, and achieve uniform stress balance. This significantly improves the toughness, impact resistance, and service stability of the structure, effectively solving the problems of easy fracture and insufficient impact resistance of single structures.

[0038] To verify the performance of the improved honeycomb structure in this embodiment, three types of improved honeycomb structures were fabricated, such as... Figure 5 As shown, they are improved honeycomb structure type A (IHSA), improved honeycomb structure type B (IHSB), and improved honeycomb structure type C (IHSC), respectively.

[0039] The three types of improved cellular structures differ in their interlayer dislocation offsets. In improved cellular structure type A 31, the dislocation offset of adjacent negative Poisson's ratio cellular unit layers is s1; in improved cellular structure type B 41, the dislocation offset of adjacent negative Poisson's ratio cellular unit layers is s2 (s2=4s1); and in improved cellular structure type C 51, the dislocation offset of adjacent negative Poisson's ratio cellular unit layers is s3 (s3=8s1).

[0040] Meanwhile, for subsequent experimental control, the traditional honeycomb structure 1 was cut into 15×15×15 mm cubes, i.e., as shown below. Figure 2 As shown, based on the traditional honeycomb structure 1, a rectangular wireframe diagram CDFE with the outline of the cut sketch is drawn, and then the stretch cut command (reverse cut) is performed and the remaining solid parts are combined to obtain the traditional negative Poisson's ratio honeycomb structure 21 (abbreviated as NPHS).

[0041] Example 2: This embodiment, based on Embodiment 1, further integrates the "brick-and-mortar" structure of shellfish shells for biomimetic design.

[0042] The shells of mollusks are composed of layers of aragonite flakes ("bricks") and an organic protein matrix ("mud"), forming a natural layered composite material. This structure effectively prevents crack propagation—when a crack penetrates the hard aragonite layer, the soft organic layer absorbs energy and deflects the crack direction, significantly improving the material's fracture toughness. In this embodiment, mimicking this structural characteristic, the modified honeycomb structure uses a TC4 titanium alloy skeleton, with PE material filling the pores inside the skeleton, forming a biomimetic honeycomb heterostructure similar to the "brick-mud" structure. The "brick"-like hard layer (TC4 titanium alloy skeleton) mainly bears the external load, resisting overall structural failure, while the "mud"-like soft layer (PE material) acts as a bond and buffer, mitigating stress abrupt changes during load transfer, achieving a synergistic improvement in structural mechanical strength, toughness, and impact resistance.

[0043] The preparation method of the biomimetic mollusks energy-absorbing box based on the negative Poisson's ratio structure in this embodiment includes the following steps: S1: Based on the dislocation characteristics of shellfish, an improved honeycomb structure is designed on the basis of the traditional negative Poisson's ratio honeycomb structure. The improved honeycomb structure is constructed using CAD software and 3D modeling software Solidworks.

[0044] S2: Save the improved honeycomb structure from step S1 as an STL format file required by the additive manufacturing equipment, and then import it into the additive manufacturing equipment. Based on selective laser melting (SLM) technology, using TC4 titanium alloy as the material, the improved honeycomb structure is prepared. The TC4 titanium alloy powder used has a particle size of 15~53 μm, the laser power is 180 W, the scanning speed is 800 mm / s, the layer thickness is 20 μm, and the spacing is 60 μm.

[0045] S3: The powder filling-hot melt vacuum insulation composite preparation process is used to fill the pores of the modified honeycomb structure skeleton with HDPE (high density polyethylene) to form a biomimetic honeycomb heterostructure, ensuring that the PE material and the TC4 skeleton 200 achieve tight interpenetration and firm bonding.

[0046] To verify the performance of the biomimetic honeycomb heterogeneous structure, three types of biomimetic honeycomb heterogeneous structures were prepared, corresponding to the three types of improved honeycomb structures in Example 1. These are biomimetic honeycomb heterogeneous structure Type A (BHHSA, corresponding to IHSA), biomimetic honeycomb heterogeneous structure Type B (BHHSB, corresponding to IHSB), and biomimetic honeycomb heterogeneous structure Type C (BHHSC, corresponding to IHSC).

[0047] Meanwhile, in order to conduct subsequent experimental comparisons, a traditional honeycomb heterogeneous structure 2 (THHS) was prepared based on the traditional negative Poisson's ratio honeycomb structure 21 in Example 1. That is, HDPE was filled into the pores of the traditional negative Poisson's ratio honeycomb structure 21 skeleton.

[0048] A schematic diagram of the process for fabricating biomimetic honeycomb heterostructures is shown below. Figure 3 As shown, the specific process is as follows: First, the modified honeycomb structure needs to be pre-treated by ultrasonic cleaning with alcohol or acetone for 15-20 minutes to ensure powder removal and avoid the truss structure causing powder adhesion and the collapse of the cantilever beams, which would affect the subsequent impregnation of HDPE. After removal, it is dried for later use. Secondly, HDPE powder is uniformly filled into the pretreated modified honeycomb structure. During the filling process, the modified honeycomb structure is gently shaken to ensure that the HDPE powder fully fills the pores of the skeleton and is evenly distributed. After filling, the modified honeycomb structure and HDPE powder are placed together into a silicone mold 300. A stainless steel counterweight block 100 with a total weight of 1.0~2.5 kg is laid on the upper surface of the mold 300, and a uniform pressure of 80~180 kPa is applied. Then, the mold 300 is placed in a box-type atmosphere furnace and heated to 205 ℃ at a rate of 5 ℃ / min and held for 3 h to completely melt the HDPE. It should be noted that the cross-sectional size of the counterweight block 100 set in the box-type atmosphere furnace should be slightly smaller than the opening of the silicone mold 300. Under the condition of effectively forming pressure impregnation, the HDPE can effectively remove air bubbles under vacuum. After melting, the pressure is evacuated to -0.095~-0.1 MPa and maintained for 20 min to remove air bubbles. The material is then kept at a vacuum for 12 h to ensure that HDPE fully penetrates into the pores of the skeleton. Finally, HDPE will slowly impregnate into the pores under its own gravity. After cooling to room temperature in the furnace, the material is demolded and cleaned to obtain the biomimetic honeycomb heterostructure.

[0049] It should be noted that, Figure 3 Taking the preparation of the traditional negative Poisson's ratio honeycomb structure 21 as an example, the preparation process of the other structures is the same.

[0050] The biomimetic honeycomb heterostructure of this embodiment combines the advantages of interlayer dislocations in shellfish and heterostructures in brick and mortar, and further combines the material performance advantages of TC4 titanium alloy and PE. It has both the special mechanical properties of negative Poisson's ratio structure and the excellent impact resistance, fracture resistance and stress dispersion ability of shellfish structure.

[0051] The performance of the structures prepared in Examples 1 and 2 above will be verified below.

[0052] Using the structures prepared in Examples 1 and 2 as research objects, including traditional negative Poisson's ratio honeycomb structure 21 (NPHS), modified honeycomb structure type A 31 (IHSA), modified honeycomb structure type B 41 (IHSB), modified honeycomb structure type C 51 (IHSC), traditional honeycomb heterostructure 2 (THHS), biomimetic honeycomb heterostructure type A 3 (BHHSA), biomimetic honeycomb heterostructure type B 4 (BHHSB), and biomimetic honeycomb heterostructure type C 5 (BHHSC), finite element simulation models were established using the finite element analysis software Hyperworks, taking into account the actual structural parameters and dimensions, material mechanical properties, and interface bonding performance of these structures. Using finite element analysis methods combining Hyperworks and LSDYNA, simulation studies were conducted on the core performance indicators such as the load-bearing capacity and structural stability of the structures, predicting the mechanical response law of the structure in actual application scenarios, and providing a reliable theoretical basis for subsequent performance test verification.

[0053] Both TC4 and HDPE materials were modeled using an elastoplastic model controlled by the MAT24 card. The specific mechanical parameters for both materials were set as follows: TC4 material had a density (Rho) of 4.43 g / cm³, an elastic modulus (E) of 21000 MPa, a Poisson's ratio (PR) of 0.30, and a yield strength (SIGY) of 1038 MPa; HDPE material had a density (Rho) of 1.20 g / cm³, an elastic modulus (E) of 1250 MPa, a Poisson's ratio (PR) of 0.44, and a yield strength (SIGY) of 22.50 MPa. The node model was constructed using tetrahedral elements with a side length of 0.4 mm. To ensure accurate stress transfer during compression and prevent interpenetration of structural components, face-to-face contact and self-contact conditions were set to accurately capture the contact behavior after sample compression, while maintaining shared nodes between adjacent meshes. During the simulated interface motion, the friction coefficient was set to 0.4. The sample was placed between two rigid plates, and a uniaxial compressive load was applied by moving the upper plate downwards at a constant speed, thus simulating the actual working conditions of a standard uniaxial compression test. Furthermore, the simulation model of the HDPE phase was obtained through Boolean operations on a solid block and a TC4 lattice structure. After quality checks confirmed its accuracy, it was re-imported into the Hypermesh module for mesh redrawing, completing the final optimization of the model.

[0054] To ensure that the dislocation strategy affects both the structural deformation mode and the structure after heterogeneous fabrication, meshes for four types of honeycomb structures and four types of honeycomb heterostructures were generated using Hypermesh software. The mesh models are shown in [reference needed]. Figure 5 As shown, the mesh accuracy is high, and the shared nodes between the two material models can be effectively guaranteed, thus avoiding the failure to effectively reflect the subsequent stress transmission trend.

[0055] A series of mechanical tests and deformation mode analyses were conducted on various structures. The mechanical test results were compared and verified with finite element simulation analysis data to ensure the accuracy and reliability of the simulation model. Simultaneously, considering the actual application requirements of automotive energy-absorbing boxes, the application adaptability of the structures was verified, confirming that they can collaboratively meet core requirements such as lightweight, high energy absorption, impact resistance, and structural stability, providing reliable support for energy absorption, vehicle body protection, and occupant safety during automotive collisions.

[0056] Specifically, after preparation, the eight structural models were subjected to static compression tests. In this embodiment, the testing equipment used was a 100KN KQL universal testing machine with a compression rate of 1 mm / min, which conformed to the range of quasi-static compression test. Each test was performed three times to avoid experimental errors.

[0057] The final performance test results are as follows Figures 6-10 As shown, where Figures 6-8 The various mechanical curves obtained during static compression testing include the actual stress-strain curve, actual energy absorption curve, and specific energy absorption curve. Figure 9 , Figure 10 This includes structural deformation modes obtained from static compression tests of various structures and stress contour plots from finite element simulations.

[0058] See Figures 6-8 The stress-strain curves, energy absorption curves, and specific energy absorption curves show that the integration of dislocation strategies can effectively improve the structural mechanical load-bearing capacity, and the strengthening effects of different dislocation strategies vary significantly, with IHSC exhibiting the best strengthening effect. In biomimetic honeycomb heterostructures, while traditional THHS shows improved load-bearing capacity compared to pure NPHS, it still suffers from a significant stress drop. The other three types of honeycomb heterostructures, modified based on dislocation strategies, effectively suppress local instability and achieve more stable mechanical responses through the buffering effect of the HDPE soft phase and the synergy of the dislocation strategies. Furthermore, the synergistic effect of dislocation strategies and the HDPE soft phase can significantly optimize the structure's energy absorption efficiency and energy absorption capacity per unit mass, with the energy absorption performance of heterostructures showing a more significant improvement compared to pure honeycomb structures.

[0059] See Figures 9-10 As shown in the deformation stress cloud diagram, the introduction of the dislocation strategy effectively hindered the original deformation mode of the traditional negative Poisson's ratio honeycomb structure 21, suppressed the local negative Poisson's ratio effect, made the stress distribution of the structure more uniform, and effectively avoided the occurrence of local instability. Traditional NPHS exhibits typical "necking" deformation, with obvious stress concentration and easy to lead to instability and collapse, while the improved structure with the dislocation strategy exhibits overall uniform shear deformation, with a more uniform stress distribution, and the deformation uniformity of different dislocation strategies is consistent with the load-bearing capacity law. In heterogeneous honeycomb structures, traditional THHS still has local buckling problems, while the dislocation-improved heterogeneous structure, through the synergy of HDPE soft phase and dislocation strategy, achieves coordinated deformation of metal skeleton and soft phase, without local damage.

[0060] The working principle of this invention can be found in [reference needed]. Figure 11As shown, considering the practical application needs of automotive energy-absorbing boxes, its core relies on the synergistic effect of dislocation modification strategies and heterogeneous composite strategies to achieve a comprehensive improvement in structural mechanical performance. This makes it suitable for the core requirements of automotive energy-absorbing boxes in efficiently absorbing energy, buffering impact, and protecting the vehicle body and occupants during collisions. As a key buffer component during automotive collisions, automotive energy-absorbing boxes need to possess excellent load-bearing stability, energy dissipation capacity, and resistance to local instability. However, when traditional NPHS (NP-Hybrid High-Speed ​​Hybrid System) is applied to energy-absorbing boxes, it is insufficient in bearing capacity under collision loads and is prone to premature instability due to stress concentration, resulting in poor safety and failing to meet the usage requirements of energy-absorbing boxes. In this invention, the dislocation modification structure, by introducing different dislocation strategies, breaks the traditional cooperative buckling path, effectively suppressing local instability and improving load-bearing capacity and deformation stability, thus preventing sudden fracture failure of the energy-absorbing box during collision. Based on this, a biomimetic honeycomb heterostructure constructed from the HDPE soft phase is introduced, forming a synergistic system of the TC4 hard phase skeleton and the HDPE soft phase. This retains the high load-bearing capacity and lightweight advantages of the hard phase, meeting the requirements of automotive lightweight design, while leveraging the excellent plastic deformation capacity of the soft phase to significantly improve the structure's toughness and energy absorption efficiency. This efficiently dissipates the impact energy generated during a car collision, reducing the impact of the collision force on the vehicle body and occupants. In summary, the dislocation strategy effectively improves load-bearing capacity and optimizes stress distribution. The synergistic effect of the HDPE soft phase and the dislocation strategy further enhances the structural mechanical stability and energy absorption efficiency, adapting to the application scenarios of automotive energy-absorbing boxes. Ultimately, it achieves comprehensive optimization of the structure's load-bearing, buffering, and energy absorption performance, making it a preferred structural solution for automotive energy-absorbing boxes.

[0061] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A biomimetic shellfish energy-absorbing box based on a negative Poisson's ratio structure, characterized in that, The energy-absorbing box has a modified honeycomb structure, which includes multiple negative Poisson's ratio honeycomb unit layers. All negative Poisson's ratio honeycomb unit layers are stacked sequentially along the thickness direction. The negative Poisson's ratio honeycomb unit layers are formed by multiple negative Poisson's ratio honeycomb cells arranged in a periodic array in the same plane. Between two adjacent negative Poisson's ratio cellular cell layers, there is a dislocation offset in the first direction in a plane parallel to the layer, causing the upper negative Poisson's ratio cell layer to be translated relative to the lower layer by a preset step size. The dislocation offset increases layer by layer along the stacking direction, forming a cumulative offset, so that the entire energy-absorbing box presents a stepped shape on the side.

2. The biomimetic shellfish energy-absorbing box based on a negative Poisson's ratio structure improvement according to claim 1, characterized in that, The improved honeycomb structure uses TC4 titanium alloy to form the skeleton, and the pores inside the skeleton are filled with PE material to form a biomimetic honeycomb heterogeneous structure.

3. The biomimetic shellfish energy-absorbing box based on a negative Poisson's ratio structure improvement according to claim 1, characterized in that, Multiple negative Poisson ratio cell cells are arranged in an array parallel to and perpendicular to the first direction.

4. The biomimetic shellfish energy-absorbing box based on a negative Poisson's ratio structure improvement according to claim 3, characterized in that, The negative Poisson's ratio honeycomb cell includes two symmetrical and parallel bottom surfaces. The same side of the two bottom surfaces is connected by two connected inclined surfaces, and the two inclined surfaces are inclined inward. Ribs are connected to the outside of the connection point of the two inclined surfaces on the same side. In the direction parallel to the first direction, the ribs between two adjacent negative Poisson's ratio cells are connected; in the direction perpendicular to the first direction, the bottom surfaces between two adjacent negative Poisson's ratio cells are connected.

5. The biomimetic shellfish energy-absorbing box based on a negative Poisson's ratio structure improvement according to claim 1, characterized in that, The dislocation offsets of adjacent negative Poisson's ratio cellular cell layers vary along the stacking direction in an arithmetic sequence.

6. The biomimetic shellfish energy-absorbing box based on a negative Poisson's ratio structure improvement according to claim 1, characterized in that, All the frames of the energy-absorbing box have the same wall thickness.

7. The method for preparing the biomimetic shellfish energy-absorbing box based on negative Poisson's ratio structure improvement according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Based on the dislocation characteristics of mollusks, an improved honeycomb structure is designed on the basis of the traditional negative Poisson's ratio honeycomb structure; S2: Based on additive manufacturing technology, the improved honeycomb structure from step S1 is printed and molded as a model of the energy-absorbing box.

8. The method for preparing the biomimetic shellfish energy-absorbing box based on the negative Poisson's ratio structure improvement according to claim 7, characterized in that, In S2, a modified honeycomb structure is prepared using TC4 titanium alloy based on additive manufacturing technology, serving as a model for the energy-absorbing box.

9. The method for preparing the biomimetic shellfish energy-absorbing box based on the negative Poisson's ratio structure improvement according to claim 7, characterized in that, In S2, based on additive manufacturing technology, a modified honeycomb structure skeleton is prepared using TC4 titanium alloy. Then, PE is filled into the pores of the skeleton using a powder filling-hot melting vacuum insulation composite preparation process to form a biomimetic honeycomb heterostructure, which serves as a model for the energy-absorbing box.

10. The method for preparing the biomimetic mollusk energy-absorbing box based on the negative Poisson's ratio structure improvement according to claim 8, characterized in that, The powder particle size of the TC4 titanium alloy is 15~53 μm.

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