Diamond substrate lattice metamaterial and additive manufacturing method thereof

Abstract

The invention belongs to the technical field of metamaterials, and particularly relates to a diamond substrate lattice metamaterial and an additive manufacturing method thereof. The structure is designed based on the geometric configuration of a diamond lattice, and has excellent high specific absorption mechanical properties. The design process comprises the following steps: firstly, carrying out spatial registration positioning on the basis of a unit cell structure with a preset wall thickness t and a unit cell width a; then, through a multi-unit-cell splicing design, the unit cells are spliced repeatedly for 12 times to form three-dimensional periodic stacking; then, the stacked structure is cut along the six datum planes; then cross plates are inserted into the six cutting faces respectively to enhance the integrity and strength of the structure; and finally, a complete DM plate lattice metamaterial structure is formed. The structure is provided with a plate-plate cross supporting framework, a complex three-dimensional inner cavity and highly symmetrical space distribution, the energy absorption capacity under unit mass is greatly improved, the mechanical properties are basically consistent in multiple directions, and the structure is suitable for the engineering fields of impact protection, energy absorption buffering and the like.

Description

Technical Field

[0001] This invention belongs to the field of metamaterials technology, and more specifically, relates to a diamond substrate lattice metamaterial and its additive manufacturing method. Background Technology

[0002] Mechanical metamaterials (MMs) are novel materials that exhibit exceptional mechanical properties through the ingenious design of their microstructural units, including ultralight weight, high strength, and high energy absorption characteristics. They hold significant promise for applications in impact protection, energy absorption, and cushioning. However, these metamaterials typically possess extremely complex microstructures, making it difficult to manufacture them as a whole using traditional material processing techniques, thus limiting their practical applications.

[0003] The emergence of additive manufacturing (AM) technology has provided a feasible approach for the integrated fabrication of complex metamaterial structures. AM allows for the layer-by-layer construction of complex microstructures based on a three-dimensional model. Fused deposition modeling (FDM), as a typical process, can utilize thermoplastic filaments to deposit complex three-dimensional components layer by layer, overcoming the limitations of traditional processes in manufacturing such structures. Furthermore, FDM eliminates the need to clean powder or provide supports within closed cavities during the manufacturing process, thus removing additional restrictions on metamaterial structures with closed cell interiors, enabling the fabrication of closed-cell structures and providing feasibility for designing efficient and compact closed-cell lattice structures.

[0004] Compared to traditional lightweight energy-absorbing materials such as honeycomb structures and foam structures, as well as conventional truss lattice metamaterials, plate lattice metamaterials (PLMs) offer significant advantages in mechanical properties. PLMs utilize plate elements instead of rod elements for support, allowing their specific strength and specific stiffness to approach the theoretical upper limits (Hashin-Shtrikman limit) of isotropic materials, while also exhibiting higher specific energy absorption (SEA) performance. Therefore, PLMs demonstrate immense potential in applications requiring lightweight and efficient energy absorption.

[0005] Diamond lattice structures, due to their geometric symmetry and multifaceted cross-support, are considered to have significant advantages in terms of lightweight, high strength, and isotropy. If closed-cell plate-lattice metamaterials can be formed based on this lattice and fabricated integrally using the fractional-dissolved metallographic process (FDM), it is expected to simultaneously achieve high specific strength, high specific energy absorption, and good manufacturability. Therefore, there is an urgent need to propose a diamond-substrate lattice metamaterial (DM) and its additive manufacturing method, enabling the efficient fabrication of closed-cell structures using the FDM process, for applications in impact protection, energy absorption buffers, and other fields requiring high lightweight and high strength performance. The diamond-substrate lattice metamaterial is referred to as DM plate-lattice metamaterial. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a diamond-substrate lattice metamaterial and its additive manufacturing method. The objective of this invention is to design a closed-cell lattice metamaterial based on a diamond unit cell topology and to shape it using an appropriate additive manufacturing process. The diamond-substrate lattice metamaterial has a closed-cell structure, composed of a three-dimensional lattice of multiple unit cell structures. It can be manufactured without introducing internal openings, maintaining the complete closed structure and excellent mechanical properties.

[0007] According to one aspect of the present invention, a diamond-based lattice metamaterial is provided, the metamaterial being composed of a plurality of periodically arranged unit cell structures. Each unit cell structure is enclosed by a cube, with an octahedron embedded inside. A triangular pyramid is connected to each of the four triangular faces of the octahedron facing diagonally opposite the unit cell structure, thereby forming a closed spatial structure corresponding to the atomic positions of the diamond unit cell. All plates constituting the structure have the same thickness t.

[0008] The unit cell of the diamond substrate metamaterial is a cube with side length *a*. Inside the cube is a regular octahedral structure, where all triangular faces of the octahedron are composed of plates of thickness *t*, and the side length of each triangular face is...

[0009] Each of the four anti-symmetrical triangular faces of the regular octahedron facing the unit cell cube is connected to a triangular pyramid. The pyramid is composed of several plates of thickness t, with its base connected to the corresponding triangular face of the regular octahedron. Its vertices extend along the diagonal directions of the cube, and the height of the pyramid is [missing information].

[0010] In the unit cell structure, the thickness of all plates (including the face plates of the regular octahedron and the face plates of the triangular pyramid) is t. The plate thickness t is an adjustable parameter of the structure, independent of the dimensional parameters of the regular octahedron, and can be freely selected without changing the above geometric dimensional relationships to control the structural performance.

[0011] Preferably, the metamaterial structure obtained by splicing multiple unit cells is subjected to reference plane cutting to form a regular integral shape with six flat outer surfaces. A cross-shaped plate structure is added to each of the outer surfaces to close the openings and enhance the overall strength and stability of the structure.

[0012] Preferably, multiple unit cell structures are arranged in an array along the x, y, and z coordinate axes, and spliced ​​together to form the overall three-dimensional structure of the diamond substrate metamaterial. By adjusting the number and arrangement of the unit cells, metamaterial structures with different array layer numbers n can be obtained.

[0013] According to another aspect of the present invention, an additive manufacturing method for the aforementioned diamond substrate lattice metamaterial is provided. The method includes the following steps:

[0014] Step 1: Using Python, set the unit cell size parameters (cube side length a and plate thickness t) in 3D modeling or finite element software to generate a 3D model of the unit cell structure;

[0015] Step 2: Arrange the single-cell model according to the panel positions of the triangular pyramid to obtain a multi-cell model containing multiple single cells;

[0016] Step 3: Cut the multicellular model along six predetermined reference planes to obtain a structure with six flat outer surfaces;

[0017] Step 4: Add a cross-shaped plate structure to each of the outer surfaces to obtain the complete metamaterial model;

[0018] Step 5: Convert the complete model into STEP / STL format and import it into a fused deposition modeling (FDM) device to form the diamond substrate metamaterial layer by layer.

[0019] Preferably, in the above method, the stiffness, strength, and energy absorption properties of the diamond substrate lattice metamaterial can be changed by adjusting the plate thickness t to meet different application requirements.

[0020] Preferably, after designing and modeling the unit cell structure, the method further includes the step of assigning material properties to the unit cell model and performing stress simulation using finite element analysis software. By applying periodic boundary conditions and loads, the mechanical response of the unit cell structure is calculated, and the mechanical properties of the entire diamond substrate lattice metamaterial can be predicted, thereby guiding the optimized design of structural parameters.

[0021] In summary, through the above technical solutions, the present invention can achieve the following beneficial effects:

[0022] 1. Compared with traditional truss lattice structures, the diamond substrate lattice metamaterial proposed in this invention has advantages such as higher specific stiffness, specific strength, and specific energy absorption. Because it uses plate units to construct the spatial lattice, the plates have a larger contact area than the truss rods, thus exhibiting better self-supporting capabilities during additive manufacturing, resulting in more stable and reliable forming.

[0023] 2. The plate-grid metamaterial provided by this invention is a closed cell structure, which does not require the design of openings in the structure to remove internal residual materials. This overcomes the process limitation of difficult powder removal in closed cavities in powder bed fusion additive manufacturing, and greatly improves the integrity of the structure and the adaptability of the manufacturing process.

[0024] 3. This invention can control the mechanical properties of the structure, such as stiffness, strength and energy absorption characteristics, by adjusting parameters such as plate thickness, thereby giving the metamaterial structure different properties and realizing an adjustable design within a certain range to meet the performance requirements of different applications such as impact protection and buffer energy absorption.

[0025] 4. This invention clearly defines the geometric dimensional relationships such as the side length of a single-cell cube, the side length of a regular octahedron, and the height of a triangular pyramid, enabling the structural parameters to be defined intuitively and accurately during actual design and production, facilitating subsequent mass design and manufacturing of the structure.

[0026] 5. Although the diamond substrate lattice metamaterial of the present invention has an extremely complex microstructure, solid components can be rapidly and accurately formed using additive manufacturing technology. In particular, the closed lattice metamaterial structure of the present invention can be easily manufactured using additive manufacturing processes such as fused deposition modeling (FDM) that do not require the removal of internal supports or powder. Attached Figure Description

[0027] Figure 1 Here is a flowchart of the design process of the diamond substrate lattice metamaterial unit cell structure provided by the present invention. (a) is a dimension diagram of the unit cell model of the present invention and a schematic diagram of the cube envelope. (b) is a schematic diagram of the unit cell splicing. (c) is a schematic diagram of the reference plane cutting and cross structure filling. (d) is a schematic diagram of the DM lattice metamaterial.

[0028] Figure 2 (a), (b), and (c) in the figure are schematic diagrams of the unit cell shown from different perspectives.

[0029] Figure 3 The figures in the middle are schematic diagrams of the diamond substrate lattice metamaterial from different perspectives.

[0030] Figure 4 This is a schematic diagram of an n-layer array of a diamond substrate lattice metamaterial (DM) provided by the present invention along a three-dimensional coordinate system. Detailed Implementation

[0031] Please see Figures 1 to 4 The diamond-based lattice metamaterial of this invention is a closed-cell lattice structure, exhibiting superior mechanical properties compared to traditional open-cell or truss-type metamaterials. For example, the DM lattice metamaterial achieves high stiffness, strength, and energy absorption performance per unit weight. Furthermore, because this invention employs a closed structural unit and eliminates the need for open-cell designs, there are no residual material cleanup issues even during powder bed manufacturing processes, making it more suitable for additive manufacturing technologies such as fused deposition modeling (FDM) that do not require internal support removal. The mechanical properties of the structure can also be controlled within a certain range by adjusting the lattice thickness t. The structural features and manufacturing method of this invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0032] like Figure 1 As shown, the basic unit of the DM lattice metamaterial of this invention is a cubic unit cell. The cubic unit cell has a side length of a, and a regular octahedron (2) is embedded inside the cubic structure. The regular octahedron consists of 6 vertices and 8 triangular faces, and the side length of each triangular face is 1. Each triangular face of the regular octahedron is formed by a thin plate with a thickness of t.

[0033] On the four triangular faces of the regular octahedron (2) facing the four body diagonals of the unit cell cube, a triangular pyramid (3) is connected to each face. The base of each pyramid coincides with the corresponding triangular face of the regular octahedron, and the vertices of the pyramids point towards one of the vertices of the cube. The height of the pyramids is... This ensures that triangular pyramids in different directions do not interfere with each other when splicing multiple cells. Figure 1 The diagram shows the spatial arrangement of the regular octahedron and triangular pyramid inside a unit cell, where the center of the cube is the center of the regular octahedron.

[0034] The unit cell structure of the present invention is a closed cavity formed by the above-mentioned regular octahedron and the triangular pyramids connected to its faces. All plates (1) used to enclose the regular octahedron and triangular pyramids have a thickness of t. The plate thickness t can be freely set during the design process according to requirements without affecting the dimensions of the regular octahedron. Therefore, while keeping the geometric configuration unchanged, the relative density and mechanical properties of the unit cell can be adjusted by changing the plate thickness.

[0035] like Figure 3 As shown, by arranging the above-mentioned unit cell structure along the atomic plane of a diamond unit cell, i.e., using the faces of a triangular pyramid as the array base, and repeatedly splicing them together, a large-scale DM lattice metamaterial structure can be constructed. In this embodiment, 12 unit cells were selected for splicing, resulting in the structure shown below. Figure 1 (b) shows the three-dimensional periodic structure model.

[0036] Because the triangular pyramidal portion of the unit cell extends beyond the overall outline during the assembly process, in order to ensure a regular shape of the resulting structure, [the following is necessary:] Figure 1 (b) The multicellular structure model was subjected to reference plane cutting, i.e., the protruding portion was removed along six planes aligned with the faces of the cubic unit cell. After six reference plane cuts, the resulting metamaterial structure has six flat outer surfaces. Figure 1 As shown in (c), a cross-shaped plate structure is added to each of the outer surfaces. The cross-shaped plate consists of two mutually perpendicular thin plates, arranged perpendicularly to each other along the center of the outer surface and collinear with the outer surface's edge. By setting the cross-shaped plates, the cell wall thickness at the cut boundary is repaired, the stiffness and strength of the structural boundary are improved, and the local stress concentration caused by large openings is effectively avoided, making the overall structure more robust. After the cross-shaped plates are filled, the final result is as shown... Figure 1 (d) shows the solid model of the DM lattice metamaterial. In this case, all the unit cavities of the entire structure are enclosed in the space enclosed by the thin plates.

[0037] The diamond-substrate metamaterial described in this invention is suitable for manufacturing using processes such as fused deposition modeling (FDM). The manufacturing steps are described below with reference to an embodiment. First, a three-dimensional model of the unit cell structure is generated using computer-aided design or finite element modeling software. Specifically, in this embodiment, a three-dimensional model of the unit cell structure is established in ABAQUS finite element software by writing a Python script. Figure 1 The shown unit cell model allows setting parameters such as the unit cell side length *a* and plate thickness *t*. The volume fraction and mechanical properties of the structure are calculated using finite element simulation software such as ABAQUS. Furthermore, for closed-pore plate-lattice metamaterials, mesh generation is relatively convenient and exhibits periodicity in the x, y, and z directions, such as... Figure 4 As shown, the structures exhibit the same mechanical properties in all three directions. Therefore, during the simulation calculation, selecting a single unit cell structure for analysis is sufficient to obtain the overall mechanical properties of the structure, thus shortening the calculation time and improving analysis efficiency.

[0038] The present invention also provides an additive manufacturing method for a closed-pore lattice metamaterial, the method being used to manufacture the aforementioned semi-open-pore lattice metamaterial, wherein the additive manufacturing method employed can be fused deposition modeling (FDM).

[0039] The specific design steps of the semi-perforated lattice metamaterial described in this embodiment are as follows:

[0040] Additive manufacturing process:

[0041] Based on the structural dimensions of the DM lattice metamaterial described in this embodiment, fused deposition modeling (FDM) is selected for manufacturing. This process is suitable for forming polymer material components with complex structures and offers high forming precision.

[0042] Based on the fused deposition modeling (FDM) printing process, PLA is selected as the raw material in this embodiment. Its elastic modulus is 1200 MPa, Poisson's ratio is 0.3, and density is 1.24 g / cm3. PLA has good printing performance and environmental performance, and meets the requirements of various working conditions such as lightweighting.

[0043] The fused deposition modeling (FDM) metamaterial requires no filler support during printing, and because each cavity is completely sealed, no uncured material remains, making the manufacturing process smooth and rapid. The resulting DM metamaterial part matches the dimensions of the design model, with a complete structure and no residual impurities. It should be noted that, depending on specific application requirements, the metamaterial can also be manufactured using other materials and processes. For example, when using metallic materials, processes such as fused wire metal deposition, which do not produce sealing residues, can be selected. Those skilled in the art should select an appropriate additive manufacturing solution based on material and equipment conditions.

[0044] The structure was generated in the finite element analysis software ABAQUS using a scripting language written in Python. The main purpose of this design is to shorten the calculation time, improve the analysis efficiency, and prepare for the later generation of large-size component models using arrays.

[0045] In summary, the above embodiments have provided a detailed description of the structure and manufacturing process of the diamond substrate lattice metamaterial of the present invention. However, the present invention is not limited to the specific embodiments described above. Any modifications, equivalent substitutions, or improvements made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A diamond-substrate metamaterial, characterized in that: The metamaterial is composed of multiple periodically arranged unit cell structures. The outer envelope of each unit cell is a cube with a side length of a. Inside the cube is a regular octahedron, and a triangular pyramid is connected to each of the triangular faces of the regular octahedron facing the four body diagonal directions of the cube. The unit cell structure is composed of a closed plate structure.

2. The diamond substrate lattice metamaterial according to claim 1, characterized in that, Multiple unit cell structures are arrayed and spliced ​​along three orthogonal coordinate axes to form the three-dimensional periodic structure of the diamond substrate metamaterial.

3. The diamond substrate lattice metamaterial according to claim 1 or 2, characterized in that, The side length of the triangular face of the regular octahedron is The height of the triangular pyramid is 4. The diamond substrate lattice metamaterial according to claim 1, characterized in that, The thickness of the plate that makes up the regular octahedron and the triangular pyramid is t, and the plate thickness t is an independent structural control parameter.

5. The diamond substrate lattice metamaterial according to claim 2, characterized in that, The diamond substrate lattice metamaterial is cut through six reference planes to form six external planes, and each external plane is provided with a cross-shaped plate structure to enhance the structural strength.

6. An additive manufacturing method for a diamond substrate lattice metamaterial, characterized in that, The method for manufacturing the diamond substrate lattice metamaterial according to any one of claims 1-5, comprising: Step 1: Determine the side length 'a' and plate thickness 't' of the unit cell, and generate a model of the unit cell structure in 3D modeling or finite element software; Step 2: The single-cell model is copied in an array along the x, y, and z axes to generate a multi-cell structure model containing multiple single cells; Step 3: Cut the multicellular structure model along six reference planes, remove the excess parts, so that the multicellular structure has six flat outer surfaces, and add a cross plate structure to each outer surface to obtain a complete diamond substrate lattice metamaterial model, and export the STEP / STL file of the complete model. Step 4: Import the STEP / STL file into the fused deposition modeling (FDM) equipment for layer-by-layer forming to obtain the diamond substrate metamaterial part.

7. The additive manufacturing method according to claim 6, characterized in that: In finite element analysis software, the unit cell model is assigned corresponding material parameters, meshed, and boundary conditions and loads are applied. The mechanical properties of the unit cell structure are simulated and tested to predict the overall mechanical properties of the diamond substrate lattice metamaterial.

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