Star truss and three-period minimal surface composite cell, lattice structure and design method

Abstract

The application discloses a composite unit cell based on a star truss and a three-period minimal surface, and belongs to the technical field of material structures. A TPMS thin shell is introduced at a stress concentration node of the star truss to realize uniform stress distribution while maintaining the negative Poisson's ratio response characteristics of the structure. Specifically, on the one hand, the node stress concentration is effectively eliminated: the stress concentration node of the star truss is wrapped with the TPMS thin shell, the inherent characteristic that the average curvature of the TPMS surface is zero is utilized, one-dimensional force flow transmitted by the rod is diffused into two-dimensional membrane stress uniformly distributed along the surface, and the fatigue failure risk of the traditional star truss caused by geometric mutation is effectively solved. On the other hand, the negative Poisson's ratio effect is completely retained: the TPMS thin shell cooperates with the rod node area, only changes the geometric shape of the node area, ensures that the rod axis direction, length and intersection angle of the star truss remain unchanged before and after the compounding, and makes the structure eliminate the stress concentration while still maintaining its unique dilatancy deformation mechanism.

Description

Technical Field

[0001] This application relates to the field of materials and structural technology, and in particular to a star-shaped truss and a three-period minimal curved surface composite unit cell, lattice structure and design method. Background Technology

[0002] Lightweight, high-strength materials are the cornerstone of strategic industries such as aerospace, defense equipment, biomedicine, and new energy vehicles. As these fields pursue extreme structural efficiency, traditional materials are struggling to meet increasingly stringent performance requirements.

[0003] Negative Poisson's ratio structures (also known as tensile structures) contract laterally under compression and expand laterally under tension. This anomalous deformation mechanism gives them unique advantages in fields such as impact resistance, energy absorption, and biomedical implants. Three-dimensional star trusses are a typical topological configuration for realizing the negative Poisson's ratio effect, achieving tensile response through the concave arrangement of the members.

[0004] On the other hand, the three-period minimum surface (TPMS) is a smooth continuous surface with zero average curvature, which has excellent properties such as uniform stress distribution, no sharp nodes, and high specific strength.

[0005] Traditional star trusses have inherent drawbacks: multiple members converge at nodes, creating sharp geometric abrupt changes (only G0 is continuous), leading to a rapid increase in local stress and the formation of stress concentration points. These stress concentration points are the main weak points of the structure, severely limiting its fatigue life and ultimate bearing capacity. While using TPMS structures alone offers the advantage of uniform stress distribution, it is difficult to achieve a negative Poisson's ratio effect; its deformation mechanism mainly relies on the bending and stretching of the curved surface and cannot generate a tensile response.

[0006] While there are studies on combining different topological configurations, most are homogeneous mixtures with a lack of targeted reinforcement designs for local weak points. A few node reinforcement schemes use simple cylindrical reinforcing rods, which not only increase the structural weight but also introduce new stress concentration risks at the joints. Summary of the Invention

[0007] This application provides a composite unit cell and lattice structure of a star truss and a three-period minimal curved surface, as well as a design method therefor, providing a lightweight, high-strength, and fatigue-resistant support structure. The technical solution is as follows: On the one hand, a composite unit cell of a star truss and a three-period minimal surface is provided, wherein the composite unit cell of the star truss and the three-period minimal surface includes: a star truss unit cell and a plurality of three-period minimal surface TPMS thin shells; The star-shaped truss unit cell has multiple members and multiple node regions, and at each node region there are at least two intersecting members whose ends meet and connect. The TPMS thin shell is a solid shell formed by applying a preset thickness to the TPMS curved surface. The multiple TPMS thin shells correspond one-to-one with the multiple node regions. Each TPMS thin shell wraps around the corresponding node region of the star-shaped truss unit cell and is smoothly connected to the rods at the corresponding node region to form an integral structure.

[0008] Optionally, the connection between each TPMS shell and the rod is made by setting a rounded corner transition.

[0009] Optionally, the TPMS shell used to enclose each of the node regions is shaped like a sphere, an ellipsoid, or a rounded polyhedron.

[0010] Optionally, the TPMS surface includes one of the following: Gyroid, I-WP, Diamond, Neovius, and Schwarz.

[0011] Optionally, the thickness T of the TPMS shell is in the range of 0.1~0.5 mm, or the thickness T of the TPMS shell is 0.1~0.3 times the outer diameter D of the rod.

[0012] Optionally, the radius R1 of the fillet at the connection between the rod and the TPMS thin shell is in the range of 0.2~0.8mm.

[0013] Optionally, the composite unit cell based on the star truss and the three-period minimal surface is a monolithic structure formed using additive manufacturing processes.

[0014] On the other hand, a design method for a composite unit cell consisting of a star-shaped truss and a three-period minimal surface is provided for designing any of the composite unit cells described above. This method includes: S1: Establish a parametric star truss unit cell model. The star truss unit cell has multiple members and multiple node regions. The outer diameter D and length L of the members are set as adjustable parameters. S2: Extract the node regions of the star truss unit cell and generate a virtual node sphere that encloses each node region; S3: Generate a TPMS surface covering the node region of the entire star truss unit cell, wherein the single cell size of the TPMS surface is set to be smaller than the diameter of a single virtual node sphere; S4: Perform Boolean intersection operation between the virtual node spheres generated in step S2 and the TPMS surface to obtain TPMS surface segments that exist only inside each virtual node sphere. S5: Thicken the TPMS surface segment obtained in step S4 to obtain the TPMS solid shell, i.e., the TPMS thin shell; S6: Perform a Boolean merge between the TPMS solid shell obtained in step S5 and the star-shaped truss unit cell obtained in step S1.

[0015] Optionally, after the TPMS solid shell and the star truss unit cell of step S1 are Boolean merged, the method further includes: setting rounded corners at the connection between the TPMS solid shell and the rod to achieve a smooth connection.

[0016] Optionally, in step S2, the radius of the virtual node sphere is R2 = D×k, and the node wrapping coefficient is k = 1.2~2.0.

[0017] On another front, a lattice structure based on a star truss and a three-period minimal surface composite unit cell is provided, comprising: a plurality of composite unit cells based on any of the above-mentioned star trusses and three-period minimal surfaces, wherein the plurality of composite unit cells based on star trusses and three-period minimal surfaces are periodically arranged to form an integral structure.

[0018] The beneficial effects of the technical solutions provided in this application include at least the following: (1) A TPMS thin shell is introduced at the stress concentration nodes of the star truss to achieve uniform stress distribution while maintaining the negative Poisson's ratio response characteristics of the structure. Specifically, on the one hand, it effectively eliminates stress concentration at the nodes: by wrapping the stress concentration nodes of the star truss with a TPMS thin shell, the inherent characteristic of the TPMS surface with zero average curvature is used to diffuse the one-dimensional force flow transmitted by the members into a two-dimensional membrane stress that is uniformly distributed along the surface, effectively solving the risk of fatigue failure caused by geometrical abrupt changes in traditional star trusses. On the other hand, it fully preserves the negative Poisson's ratio effect: the TPMS thin shell is combined with the member node area, only changing the geometry of the node area, ensuring that the axial direction, length and intersection angle of the members of the star truss remain unchanged before and after the combination, so that the structure can eliminate stress concentration while still maintaining its unique tensile deformation mechanism.

[0019] (2) A rounded corner is set at the connection between the rod and the TPMS thin shell to achieve a smooth transition, which can achieve continuous G1 curvature or continuous G2 curvature, ensure smooth transmission of stress flow lines, and eliminate secondary stress concentration sources at the connection.

[0020] (3) The TPMS shells used to wrap the node areas of each star truss adopt different shapes, which can better adapt to different member angles and better eliminate stress concentration. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1This is a three-dimensional view of a star-shaped truss and a three-period minimal surface composite unit cell structure provided in an embodiment of this application; Figure 2 yes Figure 1 The front view of the star truss and the three-period minimal surface composite unit cell structure is shown. Figure 3 yes Figure 1 The top view of the star-shaped truss and the three-period minimal surface composite unit cell structure is shown. Figure 4 yes Figure 1 The left view of the star-shaped truss and the three-period minimal surface composite unit cell structure is shown. Figure 5 This is a three-dimensional diagram of a lattice structure based on a star truss and a three-period minimal surface composite unit cell structure provided in an embodiment of this application; Figure 6 yes Figure 5 The top view shown is of a lattice structure based on a star truss and a three-period minimal surface composite unit cell structure. Figure 7 This is a comparison diagram of the stress-strain performance of two sets of samples provided in the embodiments of this application: a pure star-shaped truss structure sample and a star-shaped truss and a three-period minimal surface composite unit cell structure sample.

[0023] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of the invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification do not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0026] Please refer to Figures 1 to 7 , Figure 1This is a three-dimensional view of a star-shaped truss and a three-period minimal surface composite unit cell structure provided in an embodiment of this application. Figure 2 yes Figure 1 The diagram shows a front view of a star-shaped truss and a three-period minimal surface composite unit cell structure. Figure 3 yes Figure 1 The top view shown is of a star-shaped truss and a three-period minimal surface composite unit cell structure. Figure 4 yes Figure 1 The left view shown is of a star-shaped truss and a three-period minimal surface composite unit cell structure. Figure 5 This is a three-dimensional diagram of a lattice structure based on a star-shaped truss and a three-period minimal surface composite unit cell structure provided in an embodiment of this application. Figure 6 yes Figure 5 The diagram shows a top view of a lattice structure based on a star-shaped truss and a three-period minimal surface composite unit cell structure. Figure 7 This is a comparison diagram of the stress-strain properties of two sets of samples provided in this application: a pure star-shaped truss structure sample and a star-shaped truss and three-period minimal curved surface composite unit cell structure sample. This application provides a star-shaped truss and three-period minimal curved surface composite unit cell structure, which may include: a star-shaped truss unit cell 100 and a TPMS thin shell 200.

[0027] The star-shaped truss unit cell 100 has multiple members 101 and multiple node regions J, at each node region J having at least two intersecting members 101 whose ends meet and connect.

[0028] The TPMS thin shell 200 is a solid shell formed by giving the TPMS curved surface a preset thickness. The plurality of TPMS thin shells 200 correspond one-to-one with the plurality of node regions J. Each TPMS thin shell 200 wraps the corresponding node region J of the star truss unit cell 100 and is smoothly connected to the rod 101 at the corresponding node region J to form an integral structure.

[0029] Among them, TPMS is a type of porous structure that is periodically arranged in three-dimensional space, with an average curvature of zero, and is smoothly connected and interconnected. It is widely used in mechanical, thermal, optical and biomedical fields. The advantages of TPMS structure are: (1) smooth and continuous: the surface has no sharp turns and the overall structure is interconnected; (2) high specific surface area; (3) excellent mechanical properties: it has high strength-to-weight ratio, energy absorption capacity and vibration isolation characteristics.

[0030] For example, the TPMS shell 200 is a solid shell formed by a predetermined thickness of a Triply Periodic Minimal Surface (TPMS). In this application, the TPMS surface may include one of Gyroid, I-WP, Diamond, Neovius, and Schwarz.

[0031] In this embodiment, a TPMS thin shell 200 is introduced at the stress concentration nodes of the star truss to achieve uniform stress distribution while maintaining the structure's negative Poisson's ratio response characteristics. Specifically, on the one hand, it effectively eliminates nodal stress concentration: by wrapping the stress concentration nodes of the star truss with the TPMS thin shell 200, the inherent characteristic of the TPMS surface having a zero average curvature is utilized to diffuse the one-dimensional force flow transmitted by the member 101 into a two-dimensional membrane stress uniformly distributed along the surface, effectively solving the fatigue failure risk caused by geometrical abrupt changes in traditional star trusses. On the other hand, it fully preserves the negative Poisson's ratio effect: the TPMS thin shell 200 works in conjunction with the nodal region J of the member 101, only changing the geometry of the nodal region J, ensuring that the axial direction, length, and intersection angle of the member 101 of the star truss remain unchanged before and after the composite, so that the structure maintains its unique tensile deformation mechanism while eliminating stress concentration.

[0032] In summary, this application provides a composite unit cell of a star truss and a three-period minimal curved surface, which may include: a star truss unit cell 100 and multiple TPMS shells 200. The TPMS shells 200 are introduced at the stress concentration nodes of the star truss to achieve uniform stress distribution while maintaining the structure's negative Poisson's ratio response characteristics. Specifically, on the one hand, it effectively eliminates nodal stress concentration: by wrapping the stress concentration nodes of the star truss with TPMS shells 200, the inherent characteristic of the TPMS surface having zero average curvature is utilized to diffuse the one-dimensional force flow transmitted by the members 101 into a two-dimensional membrane stress uniformly distributed along the surface, effectively solving the fatigue failure risk caused by geometrical abrupt changes in traditional star trusses. On the other hand, it fully preserves the negative Poisson's ratio effect: the TPMS shells 200 cooperate with the nodal region J of the members 101, only changing the geometry of the nodal region J, ensuring that the axial direction, length, and intersection angle of the members 101 of the star truss remain unchanged before and after the composite, so that the structure maintains its unique tensile deformation mechanism while eliminating stress concentration.

[0033] Optional, such as Figures 1 to 4As shown, the connection between the TPMS shell 200 and the rod 101 in the composite unit cell based on the star truss and the three-period minimal surface is achieved by setting a fillet R for a smooth transition. In this case, setting a fillet at the connection between the rod 101 and the TPMS shell 200 achieves a smooth transition, that is, it can achieve continuous G1 curvature or continuous G2 curvature, ensuring smooth transmission of stress flow lines and eliminating secondary stress concentration sources at the connection.

[0034] For example, the fillet radius R1 at the connection between rod 101 and TPMS shell 200 ranges from 0.2 to 0.8 mm. For example, the fillet radius R1 at the connection between rod 101 and TPMS shell 200 can be 0.2 mm, 0.5 mm, or 0.8 mm.

[0035] In this application, as Figures 1 to 4 As shown, the TPMS shell 200 used to enclose the nodal regions J of each star-shaped truss unit cell 100 is shaped like a sphere, an ellipsoid, or a rounded polyhedron. Thus, by using different shapes for the TPMS shell 200 to enclose the nodal regions J of each star-shaped truss, it can better adapt to different angles of the members 101, thereby better eliminating stress concentration.

[0036] Here, the thickness of the TPMS shell 200 can range from 0.1 to 0.5 mm. For example, the thickness of the TPMS shell 200 can be 0.1 mm, 0.3 mm, or 0.5 mm. Alternatively, the thickness of the TPMS shell 200 can be 0.1 to 0.3 times the outer diameter D of the rod 101. For example, the thickness of the TPMS shell 200 can be 0.1, 0.2, or 0.3 times the outer diameter D of the rod 101. It should be noted that when the rod 101 is a cylindrical rod, the outer diameter of the rod 101 can be the diameter of the cylindrical rod.

[0037] In the embodiments of this application, the star-shaped truss and the three-period minimal surface composite unit cell are an integral structure formed using an additive manufacturing process. For example, the star-shaped truss and the three-period minimal surface composite unit cell can be a structure made of nylon.

[0038] Here, pure star-shaped truss structure samples and star-shaped truss combined with three-period minimal curved surface composite unit cell samples were used. Quasi-static compression tests were conducted on the mechanical properties of the samples using an electronic materials testing machine. To ensure data reliability and repeatability, each set of samples underwent three repeated tests. Stress and strain data were collected simultaneously during the tests, and stress-strain performance comparison charts of the two sets of samples were plotted after the tests were completed.

[0039] (1) Structural strengthening and stiffness enhancement; Within the strain range of 0-12%, the stress growth rate of the composite structure with strain is significantly higher than that of the pure star truss, proving that the combination of the three-period minimum surface and the star truss can significantly improve the overall stiffness and deformation resistance of the structure.

[0040] (2) The load-bearing capacity has been significantly improved; Under the same strain, the composite structure has a higher stress value, indicating that it can withstand a greater compressive load under the same deformation, and the structural bearing capacity is substantially improved.

[0041] (3) It has more outstanding energy absorption performance; A larger area under the stress-strain curve indicates a stronger energy absorption capacity per unit volume, making it more advantageous in buffering and shock-resistant scenarios.

[0042] This application also provides a lattice structure 00 based on a star-shaped truss and a three-period minimal surface composite unit cell. This lattice structure may include multiple star-shaped trusses and three-period minimal surface composite unit cells 000, and the multiple star-shaped trusses and three-period minimal surface composite unit cells are periodically arranged to form an integral structure. It should be noted that the lattice structure of the star-shaped trusses and three-period minimal surface composite unit cells can also be an integral structure formed using additive manufacturing processes.

[0043] This application also provides a design method for a composite unit cell of a star truss and a three-period minimal surface, used to design any of the star truss and three-period minimal surface composite unit cells given above. The method may include: Step S1: Establish a parameterized star truss unit cell model. The star truss unit cell has multiple members and multiple node regions. The outer diameter D and length L of the members are set as adjustable parameters. The length L of the members is the extension length along the axial direction of the members. Here, we can first define global parameters: rod outer diameter D, rod length, node wrap factor k, TPMS cell size, and TPMS shell thickness. For example, taking a typical star-shaped unit cell: first create 17 key points, including the center point (0,0,0), eight vertices (±L / 2, ±L / 2, ±L / 2), and concave nodes (±L / 4, ±L / 4, ±L / 4) in a 3D coordinate system. Then, connect the center point to the eight concave nodes, and connect each of the eight concave nodes to the three adjacent octaves of the octave containing that concave node, as well as the vertex of that octave, generating 40 rods.

[0044] S2: Extract the node regions of the star truss unit cell and generate a virtual node sphere that encloses each node region; Here, the radius of the virtual node sphere is R2 = D×k, and the node wrapping system is k=1.2~2.0.

[0045] S3: Generate a TPMS surface covering the node region of the entire star truss unit cell, wherein the single cell size of the TPMS surface is set to be smaller than the diameter of a single virtual node sphere; S4: Perform Boolean intersection operation between the virtual node spheres generated in step S2 and the TPMS surface to obtain TPMS surface segments that exist only inside each virtual node sphere. S5: Thicken the TPMS surface segment obtained in step S4 to obtain the TPMS solid shell, i.e., the TPMS thin shell; S6: Perform a Boolean merge between the TPMS solid shell obtained in step S5 and the star-shaped truss unit cell obtained in step S1.

[0046] In this application, after the TPMS solid shell described in step S6 and the star truss unit cell described in step S1 are Boolean merged, the method further includes: setting rounded corners at the connection between the TPMS solid shell and the rod to achieve a smooth connection.

[0047] Here, a specific embodiment of the lattice structure based on a star-shaped truss and a three-period minimal surface composite unit cell, based on nTopology, is described below. The three-period minimal surface used here is Gyroid. Step 1: Establish a parameterized star truss unit cell and define the following global parameters: member diameter D_strut = 1.0 mm, member length L_cell = 10 mm, node wrap factor k = 1 (node ​​sphere radius R_core = 1 mm), TPMS cell size cell_size = 1.5 mm, TPMS shell thickness T_shell = 0.2 mm, and transition fillet radius R_fillet = 0.3 mm; In nTopology, 8 vertices, 8 concave points and 1 center point are defined using Point blocks, 40 rod axes are generated by connecting them using Line blocks, and star truss entities are generated using Lattice from Graph blocks.

[0048] Step 2: Generate the spheres that wrap around the nodes. Extract all vertices of the star truss to obtain 17 node positions. Generate 17 spheres using Sphere blocks, with a radius R_core = D_strut × k = 1 mm. Merge all spheres using a Boolean Union to obtain a set of spheres that wrap around all nodes.

[0049] Step 3: Generate a dense TPMS surface using a Rectangular Volume Lattice block. The Volume input should be a Box that encloses all spheres (the Box size can be freely chosen, but it must cover the star truss and node spheres). Select TPMS Unit Cell with Offset for Unit Cell, Gyroid for TPMS Type, and set the Unit Cell Size to 1.5 mm (X, Y, Z directions). Set the Midsurface Offset to 0 mm (generating a zero-thickness surface). This will generate a dense Gyroid surface covering the entire node region.

[0050] Step 4: Trim the TPMS fragment inside the node, and use the Boolean Intersect block to intersect the Gyroid surface from Step 3 with the merged sphere from Step 2 to obtain the Gyroid surface fragment that exists only inside the sphere.

[0051] Step 5: Thicken the solid shell. Use the Offset Body block, input the output of Step 4, OffsetDistance = T_shell = 0.2 mm, Offset Type = Thickness, to obtain the thickened Gyroid solid shell.

[0052] Step 6: Merge the truss and the shell. Use a Boolean Union block to merge the star truss from Step 1 with the Gyroid shell from Step 5. Set Blend Type = Rounded and Blend Radius = R_fillet = 0.3 mm to achieve a smooth transition.

[0053] Step 7: Arraying. Use Array Body blocks to periodically array the composite unit cells to obtain the final composite lattice structure.

[0054] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0055] The above description is merely an optional embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A composite unit cell of a star-shaped truss and a three-period minimal surface, characterized in that, include: Star-shaped truss unit cell and multiple three-period minimal surface TPMS thin shell; The star-shaped truss unit cell has multiple members and multiple node regions, and at each node region there are at least two intersecting members whose ends meet and connect. The TPMS thin shell is a solid shell formed by applying a preset thickness to the TPMS curved surface. The multiple TPMS thin shells correspond one-to-one with the multiple node regions. Each TPMS thin shell wraps around the corresponding node region of the star-shaped truss unit cell and is smoothly connected to the rods at the corresponding node region to form an integral structure.

2. The star-shaped truss and three-period minimal surface composite unit cell according to claim 1, characterized in that, The connection between each TPMS thin shell and the rod is achieved by setting a rounded corner transition.

3. The star-shaped truss and three-period minimal surface composite unit cell according to claim 2, characterized in that, The radius R1 of the fillet at the connection between the rod and the TPMS thin shell ranges from 0.2 to 0.8 mm.

4. The star-shaped truss and three-period minimal surface composite unit cell according to claim 1, characterized in that, The TPMS shell used to enclose each of the node regions is shaped like a sphere, an ellipsoid, or a rounded polyhedron.

5. The star-shaped truss and three-period minimal surface composite unit cell according to claim 1, wherein the TPMS surface comprises: One of the following: Gyroid, I-WP, Diamond, Neovius, and Schwarz.

6. The star-shaped truss and three-period minimal surface composite unit cell according to claim 1, characterized in that, The thickness T of the TPMS shell is in the range of 0.1~0.5 mm, or the thickness T of the TPMS shell is 0.1~0.3 times the outer diameter D of the rod.

7. The star-shaped truss and three-period minimal surface composite unit cell according to claim 1, characterized in that, The star-shaped truss and the three-period minimal surface composite unit cell are integral structures formed using additive manufacturing processes.

8. A design method for a composite unit cell of a star-shaped truss and a three-period minimal surface, characterized in that, A method for designing the composite unit cell according to any one of claims 1-7 comprises: S1: Establish a parametric star truss unit cell model. The star truss unit cell has multiple members and multiple node regions. The outer diameter D and length L of the members are set as adjustable parameters. S2: Extract the node regions of the star truss unit cell and generate a virtual node sphere that encloses each node region; S3: Generate a TPMS surface covering the node region of the entire star truss unit cell, wherein the single cell size of the TPMS surface is set to be smaller than the diameter of a single virtual node sphere; S4: Perform Boolean intersection operation between the virtual node spheres generated in step S2 and the TPMS surface to obtain TPMS surface segments that exist only inside each virtual node sphere. S5: Thicken the TPMS surface segment obtained in step S4 to obtain the TPMS solid shell, i.e., the TPMS thin shell; S6: Perform a Boolean merge between the TPMS solid shell obtained in step S5 and the star-shaped truss unit cell obtained in step S1.

9. The design method for a composite unit cell of a star-shaped truss and a three-period minimal surface according to claim 8, characterized in that, After the TPMS solid shell described in step S6 is Boolean merged with the star truss unit cell in step S1, the method further includes: setting a rounded smooth connection at the connection between the TPMS solid shell and the rod.

10. The design method for a composite unit cell of a star-shaped truss and a three-period minimal surface according to claim 8, characterized in that, In step S2, the radius of the virtual node sphere is R2 = D×k, and the node wrapping coefficient is k = 1.2~2.

0.

11. A lattice structure based on a star-shaped truss and a three-period minimal surface composite unit cell, characterized in that, include: Multiple star-shaped trusses as described in any one of claims 1-7 and three-period minimal surface composite units are arranged periodically to form an integrated structure.

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