Continuous fiber reinforced composite topology lattice structure design and 3D printing method

Abstract

A continuous fiber reinforced composite topological lattice structure design and 3D printing method comprises the steps that firstly, the elastic tensor of a unit cell structure of a 3D printing continuous fiber reinforced composite is represented, then a topological optimization model of the unit cell structure of the continuous fiber reinforced composite is constructed and divided into sub-regions, fiber tracks are generated for the sub-regions, and finally the topological lattice structure of the continuous fiber reinforced composite is obtained. The arrangement angle of the unit cell structures is calculated, the unit cell structures are periodically filled, and fiber tracks in the sub-regions are obtained; secondly, extracting fiber tracks of the sub-regions, obtaining minimum printing paths of the fiber tracks in each sub-region in combination with a periodic unit cell structure printing form, and connecting to obtain 3D printing sub-paths; then the 3D printing sub-paths are connected to obtain a 3D printing path of the continuous fiber reinforced composite topological lattice structure, and G-codes are generated in combination with the printing speed and the material feeding rate and used for sample piece manufacturing of a 3D printer; the manufacturing requirements of continuous fiber 3D printing are met.

Description

Technical Field

[0001] The present invention belongs to the cross - technical field of structural optimization, composite materials and additive manufacturing, and specifically relates to a design and 3D printing method for a continuous fiber - reinforced composite material topological lattice structure. Background Art

[0002] The continuous fiber - reinforced composite material lattice structure has significant advantages such as light weight, high specific strength, high specific stiffness, and adjustable geometric characteristics, and 3D printing technology provides key support for its realization. 3D printing is based on the principle of layer - by - layer stacking of materials. By precisely controlling the deposition position of the materials, complex lattice structures can be gradually constructed, thereby optimizing and regulating the structural performance. This manufacturing method breaks through the limitations of traditional lattice structures in design and processing. It can not only flexibly design lattice unit cells with complex geometric shapes but also improve the mechanical properties of the structure by optimizing the fiber arrangement to meet the requirements of lightweight and high performance.

[0003] Topological optimization provides new possibilities for the design of lattice structures. By optimizing the distribution of materials, it can not only significantly improve mechanical properties but also increase manufacturing efficiency. Due to the strong operability of lattice structures in 3D printing, combined with topological optimization methods, design schemes with both manufacturability and complex geometric shapes can be generated, thus minimizing weight while ensuring structural performance. This method can simultaneously optimize the geometric characteristics and material distribution of lattice unit cells within the design space, ultimately forming a lightweight and efficient structural form. Especially in the field of lightweight design, topological optimization of lattice structures can still effectively maintain excellent mechanical properties by reducing the amount of material used, thereby demonstrating unique application advantages.

[0004] However, the current design and manufacturing methods for lattice structures of continuous fiber reinforced composites are still limited to simple configurations of regular filling of periodic unit cells (A novel single-stroke path planning algorithm for 3D printers using continuous carbon fiber reinforced thermoplastics, Additive Manufacturing 55(2022)). When filling the unit cells, only the adaptability of 3D printing under fixed geometric features is considered, thus failing to fully exploit the potential of lattice structure design and 3D printing manufacturing. Compared with traditional methods, topology optimization (Recent Advances on Topology Optimization of Multiscale Nonlinear Structures, Archives of Computational Methods in Engineering 24(2)(2016)227-249) enables lattice structures to simultaneously optimize the macroscopic topological configuration and the microscopic unit cell structure, realizing the multiscale design of macro-micro structures and greatly expanding the design freedom of lattice structures. However, limited by the manufacturing constraints of 3D printing of continuous fiber reinforced composites, there is a gap between the complex geometric features of topological lattice structures and manufacturing requirements, making it difficult to effectively combine theoretical design and actual manufacturing, thus hindering the further development of high-performance composite lattice structures. Summary of the Invention

[0005] To overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a design and 3D printing method for topological lattice structures of continuous fiber reinforced composites, which simultaneously optimizes the macroscopic topological configuration and the microscopic unit cell structure within the design space, and finally forms a lightweight and efficient structural form to meet the manufacturing requirements of continuous fiber 3D printing.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A design and 3D printing method for topological lattice structures of continuous fiber reinforced composites, comprising the following steps:

[0008] 1) Characterize the elastic tensor of the unit cell structure of 3D printed continuous fiber reinforced composites: Determine the fiber direction within the unit cell structure according to the 3D printing angle of the continuous fibers in the unit cell structure; Based on the material stiffness models in different fiber directions and combined with homogenization numerical calculations, obtain the macroscopic equivalent properties of the unit cell structure, i.e., the elastic tensor E c ; At this time, regard the unit cell structure as a kind of material for constructing the lattice structure, and its material density ρ and rotation angle α are used as design variables;

[0009] 2) Construct a topology optimization model for the unit cell structure of continuous fiber-reinforced composites: According to the optimization objective, determine the load, boundary conditions, and design domain, and divide the design domain into n finite element cells; Take the elastic tensor E of the unit cell structure obtained in step 1) c as the stiffness matrix of the material, perform finite element modeling and optimization solution, and iteratively update its material density ρ and rotation angle α, where 0 < ρ ≤ 1 and -2π ≤ α ≤ 2π, to obtain the optimal material density ρ i and the optimal rotation angle α i , i = 1, 2, …, n, that is, the topological lattice structure model;

[0010] 3) Divide the topological lattice structure model obtained in step 2) into m sub-regions, and combine the optimal material density ρ i and the optimal rotation angle α i in each sub-region to generate the fiber trajectories for the sub-regions; At this time, take the optimal material density ρ i as the weight factor of the optimal rotation angle α i , calculate the average angle φ within the neighborhood of the finite element cell as the arrangement angle of the unit cell structure; Then, periodically fill the unit cell structure within the sub-region according to the arrangement angle φ to obtain the fiber trajectories within the sub-region;

[0011] 4) Extract the fiber trajectories of the sub-regions obtained in step 3), and combine them with the form of periodic unit cell structure printing to obtain the minimum number of printing paths k for the fiber trajectories within each sub-region, where k ≥ 1. At this time, the topological lattice structure can be printed through at most m × k independent paths; Then, connect these independent paths according to their positional relationships in the sub-regions to merge adjacent multiple paths into a single sub-path, thereby obtaining K 3D printing sub-paths;

[0012] 5) Connect the 3D printing sub-paths obtained in step 4). When the sub-paths are adjacent, directly connect their ends; When the sub-paths are not adjacent, arrange additional paths outside the design domain for connection, and finally obtain the 3D printing path of the continuous fiber-reinforced composite topological lattice structure;

[0013] 6) Based on the 3D printing path of the continuous fiber-reinforced composite topological lattice structure obtained in step 5), combine the printing speed and material feeding rate, and use this path to generate G-code for manufacturing samples on a 3D printer.

[0014] In step 1), the unit cell structure of the continuous fiber reinforced composite material adopts a structural form that can realize periodic 3D printing, including unit cell structures such as lattice, honeycomb, and triangle; the numerical calculation software for the elastic modulus of the unit cell structure is ANSYS, ABAQUS, or MATLAB.

[0015] In step 3), the sub-regions of the topological lattice structure should be completely covered by the periodic unit cell structure to maintain the integrity of the topological geometric configuration; if the sub-region cannot be completely filled, the range of the sub-region is reduced until it is covered by the periodic unit cell structure.

[0016] When connecting the paths in adjacent sub-regions in step 4), it is necessary to ensure both the connectivity of the overall path and the printability of the connecting path, and connect them by extending outside the design domain to improve the smoothness of the generated sub-paths.

[0017] For the 3D printer used in step 6), if it has a fiber cutting function, the paths outside the design domain generated in steps 4) and 5) are regarded as jump points during the printing process for wire cutting; if it does not have a fiber cutting function, the redundant structures outside the design domain are removed after printing.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] The present invention combines the lattice structure of continuous fiber reinforced composite materials, topology optimization, and 3D printing technology to realize the integrated design and manufacturing of the macroscopic topological morphology and microscopic unit cell orientation of the lattice structure. Compared with the prior art, the present invention breaks through the limitations of the regular filling configuration of periodic unit cells in traditional continuous fiber reinforced composite material lattice structures, enabling the distribution and orientation of the unit cells of the lattice structure to be optimized according to specific working conditions, greatly enhancing the adaptability of the lattice structure under diverse load conditions, thereby significantly improving the mechanical properties of the lattice structure and the utilization efficiency of continuous fibers; at the same time, fully considering the 3D printing manufacturing constraints of continuous fibers, generating 3D printing paths with high connectivity based on the topological morphology and unit cell structure characteristics, thus realizing the unity of structural performance optimization and manufacturing feasibility and meeting the manufacturing requirements of complex topological lattice structures.

[0020] The present invention has good applicability, effectively solves the problems of single design configuration and poor manufacturability of current continuous fiber reinforced composite material lattice structures, provides a practical solution for the design and manufacturing of high-performance and lightweight structures, and further expands its application potential in high-end engineering fields such as aerospace and automotive manufacturing. Brief Description of the Drawings

[0021] Figure 1 is a flowchart of an embodiment of the present invention.

[0022] Figure 2 It is a schematic diagram of the unit cell of the continuous fiber lattice structure in the embodiment of the present invention.

[0023] Figure 3 It is a schematic diagram of the theoretical model of the topological lattice structure in the embodiment of the present invention.

[0024] Figure 4 It is a schematic diagram of generating fiber trajectories for sub-regions of the topological lattice structure in the embodiment of the present invention.

[0025] Figure 5 It is a schematic diagram of the sub-path of the topological lattice structure of the continuous fiber reinforced composite material in the embodiment of the present invention.

[0026] Figure 6 It is a schematic diagram of the 3D printing path of the topological lattice structure of the continuous fiber reinforced composite material in the embodiment of the present invention.

[0027] Figure 7 It is a 3D printed sample of the topological lattice structure of the continuous fiber reinforced composite material in the embodiment of the present invention.

[0028] Figure 8 It is a graph of the performance test results of the 3D printed sample in the embodiment of the present invention. Detailed implementation manners

[0029] The present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings. In this embodiment, a continuous fiber reinforced composite material 3D printer without a cutting function is used, and MATLAB is used as the numerical calculation software for calculating the elastic tensor of the unit cell, structural topology optimization, and generating the printing path.

[0030] Refer to Figure 1 , a method for designing and 3D printing a topological lattice structure of a continuous fiber reinforced composite material, comprising the following steps:

[0031] 1) Characterize the elastic tensor of the unit cell structure of the 3D printed continuous fiber reinforced composite material: In this embodiment, a cross lattice is used as the unit cell structure, as shown in Figure 2 ; According to the 3D printing angles of the continuous fibers in the cross lattice unit cell structure, determine the fiber directions within the unit cell structure. The fiber directions of 0°, 90°, and the cross position [0 / 90] are respectively marked in Figure 2 ; According to the material stiffness models of these fiber directions, perform microstructure homogenization numerical calculations to obtain the macroscopic equivalent properties of the cross lattice unit cell structure, that is, the elastic tensor E c ; At this time, regard the cross lattice unit cell structure as a kind of material for constructing the lattice structure, and its material density ρ and rotation angle α are used as design variables;

[0032] 2) Construct a topology optimization model for the unit cell structure of continuous fiber reinforced composites: In this embodiment, the minimum structural compliance is taken as the optimization objective, a concentrated load is added to the upper left corner, fixed constraints are added to the bottoms of the left and right ends, and the design domain is divided into 15×60 finite element cells; the elastic tensor E c of the unit cell structure obtained in step 1) Figure 3 is used as the stiffness matrix of the material, finite element modeling and optimization solution are carried out, and its material density ρ (0 < ρ ≤ 1) and rotation angle α (-2π ≤ α ≤ 2π) are iteratively updated. The optimization results are as i shown, and the optimal material density ρ i and optimal rotation angle α

[0033] of each finite element cell are shown in the figure (i = 1, 2, …, 900), that is, the topological lattice structure model; i and optimal rotation angle α i of each sub-region, generate the fiber trajectories of the sub-region; at this time, use the optimal material density ρ i as the weight factor of the optimal rotation angle α i , calculate the average angle φ in the neighborhood of the finite element cell. As Figure 4 shown in the left figure, the connection angle between the dots of the fiber trajectory is the calculated average angle φ, which is used as the arrangement angle of the unit cell structure; then the unit cell structure is periodically filled in the sub-region according to the arrangement angle φ to obtain the fiber trajectory in the sub-region, as Figure 4 shown in the right figure, and the structure of the sub-region is completely covered by the generated fiber trajectory;

[0034] 4) Extract the fiber trajectories of the sub-regions obtained in step 3). Considering the printing form of the periodic cross-lattice unit cell structure, the number of printing paths of the fiber trajectories in each sub-region is 2, that is, the lattice structure formed by the cross-lattice requires 2 paths to intersect each other; then, connect these paths according to the positional relationship of the sub-regions where they are located. As Figure 5 shown, 4 3D printing sub-paths are obtained. Figure 5 In the figure, path 1 and path 2 are longitudinal printing paths, and path 3 and path 4 are transverse printing paths. The longitudinal printing paths and the transverse printing paths intersect each other to form a cross-lattice unit cell path;

[0035] 5) Connect the sub-paths obtained in step 4). When the sub-paths are adjacent, directly connect their ends; when the sub-paths are not adjacent, arrange additional paths outside the design domain for connection, such as Figure 5 the dotted path in the figure, to obtain the 3D printing path of the continuous fiber reinforced composite topological lattice structure, asFigure 6 as shown

[0036] 6) Based on the 3D printing path of the continuous fiber reinforced composite topological lattice structure obtained in step 5), combining the printing speed and the material feeding rate, this path is used to generate G-code for sample manufacturing by a 3D printer and to remove the connection structures outside the design domain, and finally a 3D printed sample made of continuous carbon fiber reinforced composite is obtained as Figure 7 shown

[0037] The performance of the 3D printed sample in this embodiment is tested by the three-point bending experiment method. The load displacement rate is set at 2 mm / min, and the traditional lattice structure is used as a comparison. Three groups of experimental tests are carried out for each structure. As Figure 8 shown, the experimental results show that the stiffness of the topological lattice structure is 757.95 ± 77.77 N / mm, which is much higher than that of the traditional lattice structure, which is 267.88 ± 21.60 N / mm; in terms of the peak load, the peak load borne by the topological lattice structure is 1130.89 ± 48.75 N, which is also much higher than that of the traditional lattice structure, whose load is 715.95 ± 79.86 N. Specifically, the structural stiffness and peak load are increased by 182.94% and 57.96% respectively, demonstrating the positive effect of the present invention on improving the mechanical properties of the 3D printed lattice structure of continuous fiber reinforced composites.

Claims

1. A design method and 3D printing method for a continuous fiber-reinforced composite material topological lattice structure, characterized in that Including the following steps: 1) Characterize the elastic tensor of the unit cell structure of 3D printed continuous fiber reinforced composites: Determine the fiber direction within the unit cell structure according to the 3D printing angle of the continuous fibers in the unit cell structure; Based on the material stiffness models in different fiber directions and combined with homogenization numerical calculations, obtain the macroscopic equivalent properties of the unit cell structure, that is, the elastic tensor E c ; At this time, regard the unit cell structure as a kind of material for constructing the lattice structure, and its material density ρ and rotation angle α are used as design variables; 2) Construct a topological optimization model for the unit cell structure of continuous fiber-reinforced composites: According to the optimization objective, determine the load, boundary conditions, and design domain, and divide the design domain into n finite element cells; Use the elastic tensor E of the unit cell structure obtained in step 1) c as the stiffness matrix of the material, perform finite element modeling and optimization solution, and iteratively update its material density ρ and rotation angle α, where 0 < ρ ≤ 1 and -2π ≤ α ≤ 2π, to obtain the optimal material density ρ i and the optimal rotation angle α i for each finite element cell, i = 1, 2, …, n, that is, the topological lattice structure model; 3) Divide the topological lattice structure model obtained in step 2) into m sub-regions, and combine the optimal material density ρ i and the optimal rotation angle α i in each sub-region to generate fiber trajectories for the sub-regions; at this time, use the optimal material density ρ i as the weight factor of the optimal rotation angle α i to calculate the average angle φ in the neighborhood of the finite element cells as the arrangement angle of the unit cell structure; then periodically fill the unit cell structure in the sub-region according to the arrangement angle φ to obtain the fiber trajectories in the sub-region; 4) Extract the fiber trajectories of the sub-regions obtained in step 3), and combine with the form of periodic unit cell structure printing to obtain the minimum number of printing paths k of the fiber trajectories in each sub-region, where k≥1. At this time, the topological lattice structure can be printed through at most m×k independent paths; Then, connect these independent paths according to the positional relationship of the sub-regions where they are located, so that multiple adjacent paths are merged into a single sub-path, thereby obtaining K 3D printing sub-paths; 5) Connect the 3D printing sub-paths obtained in step 4). When the sub-paths are adjacent, directly connect their heads and tails; when the sub-paths are not adjacent, arrange additional paths outside the design domain for connection, and finally obtain the 3D printing path of the continuous fiber reinforced composite material topological lattice structure; 6) Based on the 3D printing path of the continuous fiber reinforced composite material topological lattice structure obtained in step 5), combine the printing speed and the material feeding rate, and use this path to generate G-code for manufacturing samples by a 3D printer.

2. The method according to claim 1, wherein: In step 1), the unit cell structure of the continuous fiber reinforced composite material adopts a structural form that can realize periodic 3D printing, including lattice, honeycomb, and triangular unit cell structures; the numerical calculation software for the elastic modulus of the unit cell structure is ANSYS, ABAQUS, or MATLAB.

3. The method according to claim 1, characterized in that: In step 3), the sub-regions of the topological lattice structure are completely covered by the periodic unit cell structure to maintain the integrity of the topological geometric configuration; if a sub-region cannot be completely filled, reduce the range of this sub-region until it is covered by the periodic unit cell structure.

4. The method according to claim 1, wherein: In step 4), when connecting the paths in adjacent sub-regions, it is necessary to ensure both the connectivity of the overall path and the printability of the connecting path, and connect by extending outside the design domain to improve the smoothness of the generated sub-path.

5. The method according to claim 1, wherein: For the 3D printer used in step 6), if it has a fiber cutting function, during the printing process, regard the paths outside the design domain generated in steps 4) and 5) as jump points and perform wire cutting; If it does not have a fiber cutting function, cut off the redundant structure outside the design domain after printing.

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