Lightweight cylindrical lattice structure based on bionic gulfweed stalks

Abstract

The invention discloses a lightweight cylindrical lattice structure based on bionic gulfweed stalks, and belongs to the technical field of lightweight lattice structures. The problems that an existing cylindrical lattice structure is generally weak in bearing capacity and too fast in rigidity attenuation under the condition of low relative density are solved. The invention discloses a lightweight cylindrical lattice structure based on bionic gulfweed stalks. The lightweight cylindrical lattice structure is mainly a hollow cylindrical structure formed by arraying a plurality of lattice unit cells. Each lattice unit cell comprises an outer truss, an inner truss and an inclined connecting rod, the outer trusses and the inner trusses are the same in structure, the outer trusses are arranged outside the inner trusses in a sleeving mode and are arranged in the same shape, and the vertex angles of the outer trusses and the vertex angles of the inner trusses are connected into a whole through the inclined connecting rods; the outer trusses between every two adjacent lattice unit cells share one frame, so that an integrated cylindrical lattice structure is obtained. A bionic principle is adopted, and a cylindrical lattice structure with light weight and high mechanical property is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lightweight lattice structure, and particularly relates to a lightweight cylindrical lattice structure based on bionic horsetail stems. BACKGROUND

[0002] In the fields of aerospace, transportation, electronic device packaging and the like, the demand for structures with lightweight and high mechanical properties is increasing, and lattice structures have become a key research direction due to their core advantages of low density and high specific stiffness, among which the application potential of cylindrical lattice structures is remarkable. However, the design of existing cylindrical lattice structures is mostly limited to the optimization of traditional topological configurations, and the excellent mechanical mechanisms formed by long-term evolution of biological structures in nature cannot be fully tapped, resulting in the problems of weak bearing capacity and rapid stiffness decay under the condition of low relative density. SUMMARY

[0003] Therefore, the application provides a lightweight cylindrical lattice structure based on bionic horsetail stems, which adopts a bionic principle to obtain a cylindrical lattice structure with lightweight and high mechanical properties.

[0004] To solve the above technical problems, the application adopts the technical scheme of:

[0005] A lightweight cylindrical lattice structure based on bionic horsetail stems is mainly a hollow cylindrical structure formed by a plurality of lattice unit arrays; each lattice unit includes an outer truss, an inner truss and a diagonal link, the structures of the outer truss and the inner truss are the same, the outer truss is sleeved outside the inner truss and arranged in the same shape, and the top corners of the outer truss and the inner truss are connected by the diagonal link; the outer trusses between adjacent two lattice units share a frame to obtain a continuous and integrated cylindrical lattice structure.

[0006] Further, the outer truss includes two trapezoidal frames and four longitudinal links, the two trapezoidal frames are arranged opposite to each other, the four longitudinal links are arranged between the two trapezoidal frames and opposite to the four top corners of the trapezoidal frames one by one, one end of each longitudinal link is connected to the top corner of one trapezoidal frame, and the other end is connected to the top corner of the other trapezoidal frame.

[0007] Further, the trapezoidal frame includes a short arc link, a long arc link and two straight links, the short arc link and the long arc link are arranged opposite to each other, and the two straight links are respectively connected to the end portions on the two sides of the short arc link and the long arc link. Further, the cylindrical lattice structure is formed by 3D printing of a composite material.

[0008] Further, the components of the composite material include glass fibers and nylon.

[0009] Further, the cylindrical lattice structure is that the lattice cells are arrayed in the circumferential direction and the vertical direction.

[0010] Further, the lattice cells in the cylindrical lattice structure are arrayed 10-14 in the circumferential direction and 5-8 in the vertical direction.

[0011] The beneficial effects of the present application compared with the prior art are:

[0012] The cylindrical lattice structure of the present application is a three-dimensional grid structure designed based on the topological structure of the natural sargassum stem. Since the lattice cell includes the inner and outer nested trusses and the inner and outer trusses are connected by diagonal links, the inner truss can support the outer truss through the diagonal links, thereby improving the elastic modulus of the lattice cell. At the same time, the cylindrical lattice structure arrayed by the lattice cells is a three-dimensional grid structure with certain energy absorption characteristics, which can improve the impact resistance. In addition, the inner and outer trusses are both frame structures composed of links, the relative density of each lattice cell is relatively small, and the outer trusses between adjacent two lattice cells share a frame, which not only can further reduce the relative density of the cylindrical lattice structure to achieve lightweight design, but also can integrate adjacent two lattice cells to improve the elastic modulus and energy absorption characteristics of the lattice cell. That is, the cylindrical lattice structure of the present application can improve the overall resistance to deformation while achieving lightweight purpose, thereby meeting the use requirements. BRIEF DESCRIPTION OF DRAWINGS

[0013] The accompanying drawings are part of the present application and serve to provide a further understanding of the present application.

[0014] Figure 1 It is a structure schematic diagram of a lightweight cylindrical lattice structure based on bionic sargassum stem of the present application.

[0015] Figure 2 It is a top view of a lightweight cylindrical lattice structure based on bionic sargassum stem of the present application.

[0016] Figure 3 It is a structure schematic diagram of a lattice cell.

[0017] Figure 4 It is a finite element model of a cylindrical lattice structure.

[0018] Figure 5 It is a static compression test diagram of a cylindrical lattice structure.

[0019] Figure 6 It is a finite element analysis and experimental deformation diagram of a cylindrical lattice structure under quasi-static compression.

[0020] Figure 7The stress-strain curve graph when the relative density of the cylindrical lattice structure is 9.1%. The stress-strain curve graph when the relative density of the cylindrical lattice structure is 7.3%.

[0021] Figure 8 The stress-strain curve graph when the relative density of the cylindrical lattice structure is 9.1%. The stress-strain curve graph when the relative density of the cylindrical lattice structure is 7.3%.

[0022] Figure 9 The stress-strain curve graph when the relative density of the cylindrical lattice structure is 9.1%. The stress-strain curve graph when the relative density of the cylindrical lattice structure is 7.3%.

[0023] Figure 10 The stress-strain curve graph when the relative density of the cylindrical lattice structure is 9.1%.

[0024] Legend: 1-lattice cell; 11-outer truss; 111-ladder-shaped frame; 112-longitudinal connecting rod; 12-inner truss; 13-oblique connecting rod. DETAILED DESCRIPTION

[0025] The application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Referring to Figure 1 , the lightweight cylindrical lattice structure based on the bionic horsetail stem of the embodiment mainly comprises a hollow cylindrical structure formed by an array of lattice cells 1. In combination with Figure 3 , each lattice cell 1 comprises an outer truss 11, an inner truss 12 and an oblique connecting rod 13. The outer truss 11 and the inner truss 12 have the same structure, which is a ladder-shaped frame structure. Thus, the lattice cell 1 obtained is also a ladder shape. The outer truss 11 is sleeved outside the inner truss 12 and arranged in the same shape. In combination with Figure 2 , the smaller end of the cross section of the outer truss 11 and the inner truss 12 is directed towards the center of the cylindrical lattice structure. The top corners of the outer truss 11 and the inner truss 12 are opposite to each other and connected by the oblique connecting rod 13. In combination with Figure 1 and Figure 2 , since the cylindrical lattice structure is formed by an array of lattice cells 1, the outer trusses 11 of the two adjacent lattice cells 1 need to be connected. The outer trusses 11 of the two adjacent lattice cells 1 of the embodiment share a frame, thereby obtaining a continuous and integrated cylindrical lattice structure.

[0027] The cylindrical lattice structure of the embodiment is a three-dimensional grid structure designed based on the topological structure of the natural sedge stem, and since the lattice cell 1 comprises the inner and outer nested inner and outer trusses 12 and 11, and the inner and outer trusses 12 and 11 are connected as a whole by the diagonal connecting rods 13, the inner truss 12 can support the outer truss 11 through the diagonal connecting rods 13, thereby improving the elastic modulus of the lattice cell 1. At the same time, the cylindrical lattice structure formed by the array of the lattice cells 1 is a three-dimensional grid structure, has certain energy absorption characteristics, and can improve the impact resistance. In addition, the inner and outer trusses 12 and 11 are both frame structures composed of connecting rods, the relative density of each lattice cell 1 is relatively small, and the outer trusses 11 between the adjacent two lattice cells 1 share a frame, which not only can further reduce the relative density of the cylindrical lattice structure and achieve lightweight design, but also can connect the adjacent two lattice cells 1 as a whole and improve the elastic modulus of the lattice cell 1. That is, the cylindrical lattice structure of the application can improve the overall elastic modulus while achieving the purpose of lightweight, and meet the use requirements. It should be noted that the relative density of the embodiment refers to the ratio of the overall actual volume of the cylindrical lattice structure to the solid volume of all connecting rods.

[0028] Referring to Figure 1 The cylindrical lattice structure of the embodiment is formed by arraying the lattice cells in the circumferential direction and the vertical direction. The lattice cells in the cylindrical lattice structure are arrayed in 10-14 in the circumferential direction, preferably 12; and 5-8 in the vertical direction, preferably 6, that is, there are 6 layers of lattice cells, and each layer has 12 lattice cells. By adjusting the number of lattice cells in each layer and the number of layers of lattice cells, and the size of the connecting rods of each lattice cell, the relative density of the cylindrical lattice structure can be changed.

[0029] Referring to Figure 3 The outer truss 11 of the embodiment comprises two trapezoidal frames and four longitudinal connecting rods 112, the two trapezoidal frames are arranged opposite to each other in up-down direction, and the four longitudinal connecting rods 112 are arranged between the two trapezoidal frames and correspond to the four corners of the trapezoidal frames one by one, one end of each longitudinal connecting rod 112 is connected to the corner of one trapezoidal frame, and the other end is connected to the opposite corner of the other trapezoidal frame, so as to form a trapezoidal frame structure.

[0030] The trapezoidal frame is composed of a short arc connecting rod, a long arc connecting rod and two straight connecting rods, the short arc connecting rod and the long arc connecting rod are arranged opposite to each other in front-back direction, and the two straight connecting rods are connected to the end portions on the two sides of the short arc connecting rod and the long arc connecting rod, respectively.

[0031] The cylindrical lattice structure is formed by 3D printing of a composite material, the composite material uses reinforced nylon PA6 as a base material and adds 30% glass fiber. Using composite material as printing material, a lightweight integrated cylindrical lattice structure can be obtained, and the addition of glass fiber can greatly improve the strength, stiffness and heat resistance of nylon. Thus, the elastic modulus and energy absorption characteristics of the cylindrical lattice structure are improved.

[0032] In this embodiment, the performance of the cylindrical lattice structure is tested by finite element analysis and quasi-static compression test.

[0033] The first kind: finite element analysis:

[0034] A unit model of three different low-density cylindrical lattice structures is established using commercial software Abaqus to determine the elastic modulus of the unit model of the cylindrical lattice structure under different low densities. We use an isotropic elastoplastic model to represent the mechanical properties of nylon PA6 (30% glass fiber). In the finite element simulation, the dynamic display analysis step (Dynamic, Explicit) is used, and the elements of the structure and the pressure plate are all tetrahedral solid elements C3D10, as shown in Figure 4 The upper and lower pressure plates are defined as discrete rigid bodies, and their degrees of freedom and boundary conditions are defined through their corresponding reference points (Reference Point, RP). The lower pressure plate is defined as a fixed boundary condition, and the upper pressure plate is moved downward along the y direction. The contact between the pressure plate and the cylindrical lattice structure is defined by general contact: the normal direction is considered as hard contact, and the tangential direction is set as a penalty function, with a friction coefficient of 0.2. For low-density cylindrical lattice structures, tetrahedral elements (type C3D10M) are used for meshing. Through mesh convergence research, it is determined that an average element size of 1mm can obtain accurate and stable simulation results and reasonable calculation time.

[0035] Figure 7 、 Figure 8 and Figure 9 The stress-strain curves of the unit model of the cylindrical lattice structure under three different low densities are shown. As can be seen from the three figures, as the stress increases, the strain of the unit model also gradually increases, and when the strain reaches a certain level, it instantaneously decreases, i.e. the unit model of the cylindrical lattice structure fails due to buckling. And through the comparison of the three figures, it can be seen that as the relative density of the cylindrical lattice structure decreases, the strain gradually increases under the same stress, and the smaller the relative density, the faster the plastic yield. That is, the increase of the relative density can increase the elastic modulus of the cylindrical lattice structure.

[0036] The second kind: quasi-static compression test:

[0037] Using reinforced nylon PA6 as the matrix material and adding 30% glass fiber as the printing material, three cylindrical lattice structure specimens with different relative densities were printed using 3D printing methods. The relative densities of these three cylindrical lattice structure specimens are... They were 9.1%, 7.3%, and 4.8%, respectively. For example... Figure 5 and Figure 6 As shown, an Instron 5569 testing machine was used for static compression testing. This testing machine is equipped with an electronic displacement controller, load sensor, loading platform, and upper and lower metal pressure plates.

[0038] During testing, three cylindrical lattice structure specimens were placed between the upper and lower metal pressure plates of the testing machine. The upper metal pressure plate was driven by an electronic displacement controller, moving downwards at a constant speed of 1 mm / min, while the lower metal pressure plate remained stationary. During the experiment, the compressive load was automatically acquired and recorded by the testing machine, and the loading process of the cylindrical lattice structure specimens was simultaneously captured and recorded in real time using a camera. The stress and strain data during the compressive process could be calculated from the original dimensions of the cylindrical lattice structure specimens. The elastic modulus of the composite cylindrical lattice structure could be calculated from the slope of the stress-strain curve in the small elastic deformation region.

[0039] like Figure 6 The figures shown depict the finite element analysis and experimental deformation of a cylindrical lattice structure under quasi-static compression. The two figures on the left show the finite element analysis and experimental results for the cylindrical lattice structure at stress 0, while the two figures on the right show the finite element analysis and experimental results for the cylindrical lattice structure at stress 0.02. A comparison of the two figures reveals that the deformation of the cylindrical lattice structure is very small, indicating that the cylindrical lattice structure in this embodiment possesses a high elastic compressive modulus.

[0040] like Figure 7 , Figure 8 and Figure 9 As shown, this represents the relative density. The three figures show stress-strain curves for cylindrical lattice structure specimens with relative densities of 9.1%, 7.3%, and 4.8%, respectively. As can be seen from these figures, the black curve represents the experimental stress-strain curve, while the red dashed line represents the stress-strain curve obtained using the finite element method (FEM). Both the experimental and FEM curves show that as stress increases, the strain of each cylindrical lattice structure specimen gradually increases, then decreases abruptly when the strain reaches a certain level, indicating buckling failure. Furthermore, a comparison of the three figures reveals that as the relative density of the cylindrical lattice structure increases... As the relative density decreases, the strain gradually increases under the same stress, and the lower the relative density, the faster the plastic yielding. That is, increasing the relative density can increase the elastic modulus of the cylindrical lattice structure.

[0041] like Figure 10 The diagram shows a comparison of the relative compressive strength of the cylindrical lattice structure of this embodiment and conventional lattice structures. The pink stars represent the relative compressive modulus of the cylindrical lattice structure of this embodiment at a certain relative density, while the other points represent the relative compressive modulus of different conventional lattice structures at a certain relative density. It can be seen that the relative compressive modulus of the cylindrical lattice structure of this embodiment at low densities is superior to that of other conventional lattice structures. This indicates that the cylindrical lattice structure of this embodiment has a higher elastic modulus and energy absorption characteristics.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions created in this application, and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions created in this application without departing from the substance and scope of the technical solutions created in this application.

Claims

1. A lightweight cylindrical lattice structure based on biomimetic horsetail grass stem, characterized in that, It is mainly a hollow cylindrical structure composed of several lattice unit cells. Each lattice unit cell includes an outer truss, an inner truss, and diagonal connecting rods. The outer truss and the inner truss have the same structure. The outer truss is fitted outside the inner truss and arranged in the same shape. The apex of the outer truss and the apex of the inner truss are connected together by diagonal connecting rods. The outer trusses between two adjacent lattice unit cells share a frame to obtain an integrated cylindrical lattice structure.

2. The lightweight cylindrical lattice structure based on biomimetic horsetail grass stems according to claim 1, characterized in that, The external truss includes two trapezoidal frames and four longitudinal connecting rods. The two trapezoidal frames are arranged vertically opposite each other, and the four longitudinal connecting rods are arranged between the two trapezoidal frames and are aligned with the four vertices of the trapezoidal frames. One end of each longitudinal connecting rod is connected to the vertices of one trapezoidal frame, and the other end is connected to the vertices of the other trapezoidal frame.

3. The lightweight cylindrical lattice structure based on biomimetic horsetail grass stems according to claim 2, characterized in that, The trapezoidal frame includes a short arc connecting rod, a long arc connecting rod, and two straight connecting rods. The short arc connecting rod and the long arc connecting rod are arranged opposite each other, and the two straight connecting rods are respectively connected to the ends of the short arc connecting rod and the long arc connecting rod on both sides.

4. The lightweight cylindrical lattice structure based on biomimetic horsetail grass stem according to claim 1, characterized in that, The cylindrical lattice structure is 3D printed from composite materials.

5. A lightweight cylindrical lattice structure based on biomimetic horsetail grass stems according to claim 4, characterized in that, The composite material comprises glass fiber and nylon.

6. The lightweight cylindrical lattice structure based on biomimetic horsetail grass stem according to claim 1, characterized in that, The cylindrical lattice structure is formed by arranging lattice unit cells in the circumferential and vertical directions.

7. A lightweight cylindrical lattice structure based on biomimetic horsetail grass stems according to claim 6, characterized in that, The cylindrical lattice structure has 10 to 14 lattice units arranged in the circumferential direction and 5 to 8 arranged in the vertical direction.

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