A method for designing continuous fiber 3D printing paths based on force flow tube load paths

Abstract

This invention relates to a continuous fiber 3D printing path design method based on a fluidic tube load path, comprising: constructing a fluidic tube load path generation model based on finite element analysis results under actual working conditions of the part; dividing the part into stress regions based on the characteristics and distribution of the fluidic tube load path curve; determining the printing path and required materials based on the fluidic tube characteristics of each stress region and the principal stress trajectory line; and optimizing the initially planned printing path for manufacturing purposes by combining extrusion printing technology. Compared with existing technologies, this invention lays continuous fibers with excellent axial tensile properties in the principal tensile region according to the fluidic tube load path, densely fills stress concentration areas with thermoplastic matrix materials, and optimizes the matrix material distribution in light-load and shear-force regions, which can effectively improve the overall strength and stiffness of the part and achieve lightweighting of the part while meeting application geometry requirements.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology, and in particular to a continuous fiber 3D printing path design method based on a force-fluid tube load path. Background Technology

[0002] Traditional 3D printing technology uses thermoplastic or thermosetting resins, gypsum, inorganic powders, etc., as printing materials. The strength and stiffness of the printed parts are not high, which cannot meet the requirements for industrial applications. High-performance fiber-reinforced polymer composites are highly favored in current research and industrial fields. Among them, continuous fiber composites, as reinforcements, mainly play a role in load-bearing in thermoplastic polymer structural components, and the fiber path in 3D printing has excellent designability.

[0003] However, current 3D printing methods often employ "unidirectional filling" and "spiral filling" for internal reinforcing fibers in parts, or arrange them along directions parallel to the contour curve based on topology-optimized structures. This approach makes it difficult to achieve lightweighting of parts while meeting application geometry requirements, and it fails to ensure that the fiber reinforcement effectively transmits loads in the main load direction, leading to a high risk of breakage at the point of load application. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology by providing a continuous fiber 3D printing path design method based on the force flow tube load path, which can realize the integrated design of structural lightweighting and mechanical performance enhancement, improve the overall strength and stiffness of the parts, and achieve lightweighting of the parts while meeting the application geometry requirements.

[0005] The objective of this invention can be achieved through the following technical solution: a continuous fiber 3D printing path design method based on a fluidic tube load path, comprising the following steps:

[0006] S1. Based on the finite element analysis results under the actual working conditions of the parts, construct a load path generation model for the force flow pipe;

[0007] S2. Based on the characteristics and distribution of the load path curve of the force flow tube, divide the stress region of the part;

[0008] S3. Based on the characteristics of the flow tube in each stress region and the principal stress trajectory line, determine the printing path and the materials required for printing.

[0009] S4. Based on the printing path obtained in step S3, perform manufacturing-oriented path optimization in conjunction with the extrusion printing process.

[0010] Furthermore, step S1 specifically includes the following steps:

[0011] S11. Establish the two-dimensional plane geometry corresponding to the part, set the load direction and constraint boundary of the force application point of the part, and obtain the stress distribution state through finite element analysis.

[0012] S12. Calculate the direction of the force flow tube at each node and draw a visual graphic of the force flow tube.

[0013] Furthermore, in step S11, after finite element analysis, the nodal coordinates (x, y) and the corresponding normal stress σ at each point are obtained. x and shear stress τ xy .

[0014] Further, step S12 specifically calculates the direction of the force flow tube at each node using the following formula:

[0015] tanθ=τ xy / σ x .

[0016] Furthermore, the stress regions of the part divided in step S2 include the main tension region, shear force region, closed-loop region, light load region, and stress concentration region.

[0017] Furthermore, the main tensile region is used to bear the tensile force from the load application point on the right to the fixed constraint boundary on the left, and it basically coincides with the main tensile stress trajectory line drawn based on the first principal stress;

[0018] The lower part of the shear region is a semi-elliptical region connected to the fixed constraint boundary, and the internal stress transitions from tensile stress to shear stress and then to compressive stress.

[0019] The closed-loop region includes four local small ring-shaped regions, which serve to bear the transition from tensile stress to compressive stress around the hole;

[0020] The upper annular region of the lightly loaded region only contacts the free boundary;

[0021] In the stress concentration region, the densely packed flow tubes are consistent with the stress concentration region.

[0022] Furthermore, step S3 specifically includes the following steps:

[0023] S31. Based on the principal stress trajectory lines, further divide the printing design area;

[0024] S32. In the main tension area, select a continuous fiber path according to the flow tube;

[0025] S33. Draw a dense fill of the stress concentration area in the main tension region;

[0026] S34. Draw auxiliary trajectory lines in the main tension region based on shear force;

[0027] S35. Draw the orthogonal principal stress trajectory lines of the shear force region and extend them to the model outline;

[0028] S36. Reduce the light load area to obtain the final part design style.

[0029] Furthermore, step S32 specifically involves selecting force flow tubes from the loading point to the constraint boundary in the main tension region for continuous fiber material 3D printing. These tubes are responsible for bearing the main load from the applied load to the constraint boundary. It is necessary to ensure that the fiber spacing at the aggregation point does not cause mutual stacking. Meanwhile, the force flow tubes in other main tension regions and the corresponding orthogonal principal compressive stress trajectory lines are printed according to the thermoplastic matrix material.

[0030] Furthermore, step S33 specifically involves selecting a matrix material to densely fill the stress concentration area. In the part involving fiber printing, the remaining part needs to be densely filled to enhance the bonding effect between the fiber and the matrix material.

[0031] Furthermore, step S4 specifically involves replacing the curved short rods with straight long rods for each grid boundary under a single-layer path. This is beneficial for further mechanical simulation verification and printing experimental code generation, while ensuring the fiber path design scheme is restored.

[0032] In terms of printing sequence, the matrix material is printed first within the same layer to provide a support and adhesion wall for fiber printing and improve printing results.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] I. This invention applies the theoretical system of fluidic tubes and continuous fiber composite materials to 3D printed parts. The continuous fibers, which play a major role in tensile strength, change the design and manufacturing methods of parts, providing possibilities for lightweighting and improved mechanical properties. This invention proposes a continuous fiber filling path design method determined by the fluidic tube load path, which can optimize the material distribution of the part while ensuring that the fiber reinforcement effectively bears the load in the main load direction. Based on the principle of dividing different regions, continuous fibers with excellent axial tensile properties are laid in the main tensile region according to the fluidic tube load path, and the stress concentration areas are densely filled with thermoplastic matrix materials. At the same time, the matrix material distribution in the light load region and the shear force region is optimized, which can ultimately improve the overall strength and stiffness of the part and achieve lightweighting of the part while meeting the application geometry requirements.

[0035] Second, this invention controls the density of fiber starting points at stress concentration points by adjusting the continuous fiber printing process, and the dense filling can enhance the bonding effect of the continuous fiber flow tube, thus preventing accidental breakage of parts at the applied load point.

[0036] Third, arranging continuous carbon fibers according to the design method of this invention can effectively improve the stress distribution of the structure. Furthermore, prioritizing the printing of matrix material intersecting with the continuous fibers within the same layer can enhance the bonding effect between the fiber composite material and the matrix material. Arranging carbon fibers according to the design path proposed in this invention can strengthen the structure, not only improving the computational efficiency of the entire process but also effectively optimizing the space required for the storage medium of the code file.

[0037] Fourth, traditional "through-type" force flow tubes printed with continuous fibers for the main load direction and "vortex-type" force flow tube structures for local loads are shear-bearing or light-load areas, which are not suitable for connecting with surrounding areas to enhance the stability of the structure. However, this invention uses orthogonal principal stress trajectory lines as auxiliary lines, which can effectively improve the printing stability of local force flow tubes and fully optimize the overall microstructure of the part. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0039] Figure 2 This is a schematic diagram illustrating the application process of an example.

[0040] Figure 3a This is a schematic diagram of the load constraints in the embodiment.

[0041] Figure 3b This is a schematic diagram of the finite element simulation results in the example;

[0042] Figure 4a This is a schematic diagram of the load path region division of the force flow tube in the embodiment;

[0043] Figure 4b This is a schematic diagram of the principal stress trajectory in the embodiment;

[0044] Figure 5 This is a schematic diagram of the continuous fiber printing path design process in the embodiment;

[0045] Figure 6a This is a schematic diagram of the curved short rod before the printing path details were optimized in the embodiment.

[0046] Figure 6b This is a schematic diagram of a straight long rod after the printing path details have been optimized in the embodiment. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0048] Example

[0049] like Figure 1 As shown, a continuous fiber 3D printing path design method based on a force-fluid tube load path includes the following steps:

[0050] S1. Based on the finite element analysis results under the actual working conditions of the parts, construct a load path generation model for the force flow pipe;

[0051] S2. Based on the characteristics and distribution of the load path curve of the force flow tube, divide the stress region of the part;

[0052] S3. Based on the characteristics of the flow tube in each stress region and the principal stress trajectory line, determine the printing path and the materials required for printing.

[0053] S4. Based on the printing path obtained in step S3, perform manufacturing-oriented path optimization in conjunction with the extrusion printing process.

[0054] This embodiment applies the above-described technical solution, such as Figure 2 As shown, it mainly includes:

[0055] (1) Using finite element analysis under actual working conditions of the part, the nodal coordinates (x, y) and the corresponding normal stress σ at each point are obtained. x and shear stress τ xy The force flow pipe load path generation model is constructed, and its generation process is as follows:

[0056] 1) This embodiment takes a perforated square plate as an example, establishes a two-dimensional planar geometry, and sets the force application point, load direction, and constraint boundaries of the part as follows: Figure 3a As shown, the stress distribution state is obtained by performing finite element analysis (e.g. Figure 3b (as shown);

[0057] 2) According to the formula tanθ=τ xy / σ x Calculate the direction of force flow in each node And draw a visual diagram of the force flow tube;

[0058] (2) Based on the characteristics and distribution of the load path curve of the flow tube, the stress region of the component is delineated as follows: Figure 4a As shown, the stress distribution is divided into the main tension region, shear force region, closed-loop region, light load region, and stress concentration region. The characteristics of each region are as follows:

[0059] 1) Main tension region: mainly bears the tensile force from the load application point on the right to the fixed constraint boundary on the left, and basically coincides with the main tensile stress trajectory line drawn based on the first principal stress;

[0060] 2) Shear region: A semi-elliptical region connected to the fixed constraint boundary at the bottom, where the internal stress transitions from tensile stress to shear stress and then to compressive stress.

[0061] 3) Closed-loop region: The four local small ring-shaped regions are similar to shear regions, which play a role in bearing the transition from tensile stress to compressive stress around the hole;

[0062] 4) Lightly loaded region: The upper annular region only contacts the free boundary, and the stress value in this region can be observed from the stress diagram.

[0063] 5) Stress concentration areas: The densely packed areas of the flow tubes largely coincide with the stress concentration areas, such as the load application point, the periphery of the hole, and the upper left boundary.

[0064] (3) Based on the characteristics of the flow tubes in each region, compare Figure 4b The main tensile / compressive stress trajectory line is analyzed, and path design rules and printing materials are determined to improve the mechanical properties of the parts and achieve efficient material utilization. The main planning process is detailed in [link to main planning process]. Figure 5 The specific process is as follows:

[0065] 1) Select the force flow tubes from the loading point to the constraint boundary in the main tension region and 3D print them with continuous fiber material. These tubes are responsible for bearing the main load from the applied load to the constraint boundary. It is necessary to ensure that the fiber spacing at the aggregation point does not cause mutual stacking. At the same time, the force flow tubes in other main tension regions and the corresponding orthogonal principal compressive stress trajectory lines are printed according to the thermoplastic matrix material.

[0066] 2) Areas of stress concentration need to be densely filled with matrix material. In particular, the remaining parts of the fiber-printed parts (such as the load application point area) need to be densely filled to enhance the bonding effect between the fiber and the matrix material.

[0067] 3) The shear force flow tube is equivalent to a part of the principal tensile stress trajectory and the principal compressive stress trajectory respectively. Shear force also exists in the closed loop region, so orthogonal principal stress trajectory lines can be planned.

[0068] 4) Although the principal compressive stress trajectory lines converge in the lightly loaded area, the stress is relatively small, and the free boundary of the associated part is generally not required to be preserved. Therefore, it is possible to remove the printing in this area to reduce unnecessary material waste.

[0069] (4) For the initially planned printing path, manufacturing-oriented path optimization is performed in conjunction with the extrusion printing process. For each mesh boundary under a single-layer path, such as... Figure 6a and Figure 6b As shown, replacing the curved short rods with straight long rods, while ensuring the fibrillation of the fiber path design, facilitates further mechanical simulation verification and printing experiment code generation. Furthermore, prioritizing the printing of the matrix material within the same layer provides a supporting adhesion wall for fiber printing, improving the printing effect.

[0070] In summary, this technical solution, based on load path design for continuous fiber composite 3D printing, achieves integrated design of lightweight and enhanced mechanical properties, improving specific strength, specific stiffness, and fatigue resistance. According to the principle of dividing different regions, this solution lays continuous fibers with excellent axial tensile properties in the main tension region according to the load path of the force flow tube, densely fills stress concentration areas with thermoplastic matrix material, and optimizes the matrix material distribution in light-load and shear-force regions. This effectively improves the overall strength and stiffness of the part, achieving lightweighting while meeting application geometric requirements.

Claims

1. A method for designing continuous fiber 3D printing paths based on force-fluid pipe load paths, characterized in that, Includes the following steps: S1. Based on the finite element analysis results under the actual working conditions of the parts, construct a load path generation model for the force flow pipe; S2. Based on the characteristics and distribution of the load path curve of the force flow tube, divide the stress region of the part; S3. Based on the characteristics of the flow tube in each stress region and the principal stress trajectory line, determine the printing path and the materials required for printing. S4. Based on the printing path obtained in step S3, perform manufacturing-oriented path optimization in conjunction with the extrusion printing process. The stress regions of the part divided in step S2 include the main tension region, shear force region, closed loop region, light load region and stress concentration region. The main tension region is used to bear the tensile force from the load application point on the right to the fixed constraint boundary on the left, and it basically coincides with the main tensile stress trajectory line drawn based on the first principal stress. The lower part of the shear region is a semi-elliptical region connected to the fixed constraint boundary, and the internal stress transitions from tensile stress to shear stress and then to compressive stress. The closed-loop region includes four local small ring-shaped regions, which serve to bear the transition from tensile stress to compressive stress around the hole; The upper annular region of the lightly loaded region only contacts the free boundary; In the stress concentration region, the densely packed part of the force flow tubes is consistent with the stress concentration region; Step S3 specifically includes the following steps: S31. Based on the principal stress trajectory lines, further divide the printing design area; S32. In the main tension area, select a continuous fiber path according to the flow tube; S33. Draw a dense fill of the stress concentration area in the main tension region; S34. Draw auxiliary trajectory lines in the main tension region based on shear force; S35. Draw the orthogonal principal stress trajectory lines of the shear force region and extend them to the model outline; S36. Reduce the light load area to obtain the final part design style.

2. The method for designing a continuous fiber 3D printing path based on a force-fluid tube load path according to claim 1, characterized in that, Step S1 specifically includes the following steps: S11. Establish the two-dimensional plane geometry corresponding to the part, set the load direction and constraint boundary of the force application point of the part, and obtain the stress distribution state through finite element analysis. S12. Calculate the direction of the force flow tube at each node and draw a visual graphic of the force flow tube.

3. The method for designing a continuous fiber 3D printing path based on a force-fluid tube load path according to claim 2, characterized in that, In step S11, after finite element analysis, the nodal coordinates (x, y) and the corresponding normal stress σ at each point are obtained. x and shear stress τ xy .

4. The method for designing a continuous fiber 3D printing path based on a force-fluid tube load path according to claim 3, characterized in that, Step S12 specifically calculates the direction of the force flow tube at each node using the following formula: tanθ=τ xy / s x 。 5. The method for designing a continuous fiber 3D printing path based on a force-fluid tube load path according to claim 1, characterized in that, Specifically, step S32 involves selecting force flow tubes from the loading point to the constraint boundary in the main tension region for continuous fiber material 3D printing. These tubes are responsible for bearing the main load from the applied load to the constraint boundary. It is necessary to ensure that the fiber spacing at the aggregation point does not cause mutual stacking. Meanwhile, the force flow tubes in other main tension regions and the corresponding orthogonal principal compressive stress trajectory lines are printed according to the thermoplastic matrix material.

6. The method for designing a continuous fiber 3D printing path based on a force-fluid tube load path according to claim 1, characterized in that, Specifically, step S33 involves selecting a matrix material to densely fill the stress concentration area. In the part involving fiber printing, the remaining part needs to be densely filled to enhance the bonding effect between the fiber and the matrix material.

7. The method for designing a continuous fiber 3D printing path based on a force-fluid tube load path according to claim 1, characterized in that, Specifically, step S4 involves replacing the curved short rods with straight long rods for each grid boundary under a single-layer path. This ensures the fiber path design scheme is accurately reproduced and facilitates further mechanical simulation verification and the generation of printed experimental code. In terms of printing sequence, the matrix material is printed first within the same layer to provide a support and adhesion wall for fiber printing and improve printing results.

Images