Method for rotary 3D printing forming of continuous carbon fiber reinforced composite stiffened cylindrical shell structure

Abstract

A kind of rotary 3D printing forming method of continuous carbon fiber reinforced composite stiffened cylindrical shell structure, first, the shape of grid rib is designed by software, and the height and thickness of stiffened cylindrical shell are determined by bearing capacity;Then, the path planning is carried out for the stiffened cylindrical shell, the x-axis direction of Cartesian coordinates is replaced by the rotation direction, and the 3D printing path of the stiffened cylindrical shell is generated based on the characteristics of rotary 3D printing;Then, the mass ratio of the stiffened cylindrical shell is calculated, if it meets the lightweight requirement, the next step of forming is carried out;Otherwise, the internal structure parameters are determined again until the lightweight requirement is met;Finally, the corresponding material system is selected, and the outer skin is formed based on the grid rib structure, and the forming of the stiffened cylindrical shell is realized by rotary 3D printing equipment;The present application realizes the controllable design and rapid forming of ultra-lightweight, high mass ratio, low-cost, multi-material system composite stiffened cylindrical shell structure.

Description

Technical Field

[0001] This invention belongs to the field of aerospace equipment stiffened cylindrical shell forming technology, specifically relating to a rotary 3D printing forming method for a continuous carbon fiber reinforced composite stiffened cylindrical shell structure. Background Technology

[0002] As a key load-bearing component of aerospace vehicles, the material and structural properties of stiffened cylindrical shells significantly impact vehicle performance. In recent years, the development of advanced composite materials, represented by carbon fiber, has made a significant contribution to the lightweighting of aerospace vehicles. With the advancement of composite materials and their forming technologies, their application has expanded from non-load-bearing and secondary load-bearing components to primary load-bearing components. While the application of composite stiffened cylindrical shell forming technology has effectively reduced the manufacturing cost of aircraft, the traditional composite material manufacturing processes involved, such as autoclave molding, fiber winding, and automated fiber placement, are limited in forming capabilities by the complexity of the mold, have a high dependence on molds, and result in long product development cycles, which is detrimental to the rapid iteration and low-cost manufacturing of aerospace vehicle products.

[0003] Continuous carbon fiber reinforced composite material 3D printing technology (Hou Zhanghao, Tian Xiaoyong. Research on lightweight application of continuous fiber reinforced composite material 3D printing [C] / / Special Processing Branch of Chinese Mechanical Engineering Society. Proceedings of the 18th National Special Processing Academic Conference (Abstract). [Publisher unknown], 2019:1.DOI:10.26914 / c.cnkihy.2019.068716.) differs from traditional manufacturing technologies. This technology, through the application of advanced composite materials and novel additive manufacturing processes, broadens and enhances the design freedom and manufacturability of continuous carbon fiber reinforced composite material structures, providing a new approach for the forming of composite material reinforced cylindrical shell structures. This technology uses small tow fibers as raw materials, breaking the constraints of traditional composite material molding, realizing the rapid manufacturing of composite material reinforced cylindrical shells without molds, and significantly improving the forming efficiency of composite material reinforced cylindrical shells. However, due to the imperfect continuous carbon fiber manufacturing process for complex mesh rib structures, the manufacturing process of planar printing reinforced cylindrical shells cannot print continuous carbon fibers along the axial direction, and there is a lack of targeted 3D printing forming methods.

[0004] Currently, most of the forming methods for stiffened cylindrical shell structures still utilize conventional metal subtractive manufacturing (Ye Pingyuan, Qian Dongsheng, Wang Huajun, et al. Feasibility study on spin forming process of inner wall stiffened cylindrical parts [J]. Mold Industry, 2021, 47(6):16-22.DOI:10.16787 / j.cnki.1001-2168.dmi.2021.06.003.). Forming methods for stiffened cylindrical shell structures based on 3D printing technology of continuous carbon fiber reinforced composite materials are still a technological gap. Therefore, the reinforcing properties of continuous carbon fiber and the flexible manufacturing advantages of 3D printing have not been fully utilized in the forming of composite stiffened cylindrical shell structures. For composite reinforced cylindrical shell structures, especially those with internal mesh reinforcement, it is necessary to utilize the properties of both materials and structures to achieve their lightweight and high load-bearing performance requirements. However, traditional molding methods do not take into account the forming characteristics of 3D printing technology, thus failing to achieve coordinated design of materials and structures. Furthermore, the materials may not be fully distributed in the effective areas, resulting in serious redundancy, which greatly increases the structural weight and manufacturing cost. This makes it difficult to leverage the advantages of continuous carbon fiber reinforced composite materials in terms of lightweight and high specific performance, thereby limiting the further development of advanced aerospace equipment made of composite materials. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide a rotary 3D printing method for continuous carbon fiber reinforced composite reinforced cylindrical shell structures. Targeting continuous carbon fiber reinforced composite cylindrical structures, the method utilizes the advantages of controllable forming and axial fiber printing in rotary 3D printing technology to generate lightweight reinforced cylindrical shell structures based on the shape of the mesh reinforcement and load-bearing performance requirements. Different materials are used to meet performance, strength, and temperature stability requirements according to different application needs, thereby achieving controllable design and rapid prototyping of ultra-lightweight, high load-to-mass ratio, low-cost, multi-material composite reinforced cylindrical shell structures.

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

[0007] A rotary 3D printing method for a continuous carbon fiber reinforced composite stiffened cylindrical shell structure includes the following steps:

[0008] 1) Design the shape of the mesh ribs using Solidworks software;

[0009] 2) Based on the shape of the mesh reinforcement obtained in step 1), and in combination with the load-bearing performance requirements of the reinforced cylindrical shell under working conditions, determine the height and thickness of the reinforced cylindrical shell;

[0010] 3) Based on the mesh rib shape information obtained in step 1) and the height and thickness information of the stiffened cylindrical shell obtained in step 2), the stiffened cylindrical shell is path-planned. The coordinate information of the closed contour is obtained in the Cartesian coordinate system. The x-axis direction of the Cartesian coordinate is replaced with the rotation direction. The 3D printing path of the stiffened cylindrical shell is generated based on the characteristics of rotary 3D printing.

[0011] 4) Based on the total length L of the composite material rotary 3D printing path obtained in step 3) and the weight w1 of the composite material filament per unit length, calculate the theoretical weight w of the stiffened cylindrical shell structure. all , i.e. w all =L×w1; Based on the mesh rib shape information obtained in step 1) and the height and thickness information of the stiffened cylindrical shell obtained in step 2), the theoretical axial bearing critical load F1 of the stiffened cylindrical shell is obtained through simulation analysis in finite element simulation software. The load-to-mass ratio a of the composite material stiffened cylindrical shell is calculated, i.e. If the theoretical load-to-mass ratio of the stiffened cylindrical shell structure meets the lightweight requirements, then proceed to the next step of structural forming; if the theoretical load-to-mass ratio of the stiffened cylindrical shell structure does not meet the lightweight requirements, then redetermine the internal structural design parameters through steps 1) and 2), increase the desired number of mesh rib shapes h, and reduce the thickness of the stiffened cylindrical shell until the high load-to-mass ratio lightweight requirements of the stiffened cylindrical shell structure are met.

[0012] 5) Based on the above steps, the rotary 3D printing path of the stiffened cylindrical shell is obtained. Combining the working environment and strength requirements of the stiffened cylindrical shell, the corresponding material system is selected, and the corresponding composite material feed parameters and printing nozzle moving speed are input. The outer skin is formed on the basis of the mesh rib structure. The stiffened cylindrical shell is formed by rotary 3D printing equipment, thus obtaining a lightweight structure of continuous carbon fiber reinforced composite stiffened cylindrical shell.

[0013] Step 1) uses rectangular grids, triangular grids, and diamond grids as the basis for grid structure and rib forming.

[0014] Step 2) The reinforced cylindrical shell is composed of mesh ribs fabricated using continuous carbon fiber reinforced composite material 3D printing technology. The mesh ribs include annular ribs and longitudinal (diagonal) ribs. The number of annular ribs is m, the number of mesh shape constraint points is n, the number of slice layers is δ, the desired number of layers is h, and the rib nodes are n. i,j,δ i = 1, 2, 3, ..., m; j = 1, 2, 3, ..., n; δ = 1, 2, 3, ..., h, n rib nodes i,j,δ The spatial coordinates are (x k ,y k ,z k ), where z k=0.3δ; The coordinate information of the rib node is used for the forming design of the mesh rib structure, and the outer skin is formed by different rotational 3D printing reference surfaces under the same spatial coordinate system.

[0015] In step 2), the mesh rib structure employs different mesh shapes, and the coordinates (x, y) in each layer of the plane are changed. k ,y k The grid can be adjusted by setting k = 1, 2, 3, ..., m×n. In addition, the density of the grid can be changed according to the axial load distribution of the reinforced cylindrical shell to achieve controllable design of load-bearing performance under different requirements.

[0016] Step 3) specifically involves: determining the turning radius r of the 3D printing path based on the characteristics of rotary 3D printing of continuous carbon fiber reinforced composite materials. set and scanning spacing h set , make r set ≥R, h set ≤H, where R and H are the minimum fiber turning radius and maximum scanning spacing allowed in rotary 3D printing; based on the spatial coordinates of the nodes and the process characteristics of rotary 3D printing of the outer wall, the printing path of the mesh ribs is first generated. The printing path consists of the outer contour path of the mesh shape and the rotary paths of the upper and lower widened ring ribs.

[0017] Step 5) specifically involves: adjusting the position of the mesh ribs to constrain the spacing d between adjacent ribs in the rotational printing direction of the outer skin. r , making d r ≤D, where D is the maximum allowable spacing distance for rotary 3D printing suspended forming; at this time, relying on the characteristics of rib support and continuous carbon fiber uninterrupted forming, the outer skin is directly rotary printed on the mesh ribs, realizing the rotary 3D printing forming of continuous carbon fiber reinforced composite stiffened cylindrical shell structure.

[0018] The material system in step 5) includes, but is not limited to, different types of high-performance polymer materials such as polyimide (PA), polylactic acid (PLA) and polyether ether ketone (PEEK), which are selected according to the needs of specific applications.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention proposes a rotary 3D printing method for forming stiffened cylindrical shell structures made of continuous carbon fiber reinforced composite materials. Utilizing the characteristics of lightweight composite materials and rotary 3D printing technology, it achieves rapid forming of ultra-lightweight, high-performance stiffened cylindrical shell structures. This method, specifically for continuous carbon fiber reinforced composite structures, generates an internal load-bearing structure based on the shape and performance requirements of the internal rib mesh, fully leveraging the reinforcing properties of continuous carbon fibers. This significantly improves material utilization and the load-to-mass ratio of the structure, effectively solving problems such as long manufacturing cycles and complex molds in traditional stiffened cylindrical shell structure forming processes. It also reduces the cost of the manufactured parts and fills a technological gap in the forming methods of composite stiffened cylindrical shell structures.

[0021] The method of this invention has good applicability. It utilizes the controllable forming characteristics of continuous carbon fiber reinforced composite rotary 3D printing technology to change the internal mesh rib structure according to the axial load of the stiffened cylindrical shell, thereby realizing the controllable design of the stiffened cylindrical shell and improving the load-bearing performance of aerospace vehicles. This method broadens and improves the design freedom and manufacturability of composite stiffened cylindrical shell structures, and promotes the development of advanced aerospace equipment made of composite materials.

[0022] This invention features diverse material systems, including but not limited to high-performance polymers such as polyimide (PA), polylactic acid (PLA), and polyetheretherketone (PEEK). These material systems have broad application potential in various fields and can be selected according to specific application requirements. Polyamide (PA) is utilized for its excellent heat resistance and mechanical properties, making it suitable for applications requiring high-temperature stability; polylactic acid (PLA) is utilized for its biodegradability, making it suitable for applications requiring low-temperature operation and environmental friendliness; and polyetheretherketone (PEEK) is utilized for its superior mechanical properties and chemical stability, making it suitable for applications requiring high-temperature and chemically resistant environments. This diversity of material choices allows continuous fiber-reinforced composite stiffened cylindrical shells to adapt to various industrial and research needs. Attached Figure Description

[0023] Figure 1 This is a flowchart of the present invention.

[0024] Figure 2 This is a schematic diagram of the internal mesh rib structure of the reinforced cylindrical shell of the present invention.

[0025] Figure 3 This is a schematic diagram of the path planning of the mesh reinforcement bars according to the present invention.

[0026] Figure 4 This is a schematic diagram of the path planning for the external skin according to the present invention.

[0027] Figure 5This is a schematic diagram of the integral reinforced cylindrical shell formed by rotary 3D printing according to the present invention.

[0028] Figure 6 This is a schematic diagram of the integrally reinforced cylindrical shell structure of the present invention.

[0029] Figure 7 This is a schematic diagram comparing the mechanical properties of the reinforced cylindrical shell of the present invention. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0031] Reference Figure 1 A method for rotary 3D printing of a continuous carbon fiber reinforced composite stiffened cylindrical shell structure includes the following steps:

[0032] 1) Design the mesh rib shape using Solidworks software, using methods such as... Figure 2 The rectangular, triangular, and rhomboid grids shown serve as the basis for the grid structure and rib forming;

[0033] 2) Based on the shape of the mesh reinforcement obtained in step 1), and considering the load-bearing capacity requirements of the reinforced cylindrical shell under working conditions, determine the height and thickness of the reinforced cylindrical shell; the interior of the reinforced cylindrical shell is composed of mesh reinforcements prepared by continuous carbon fiber reinforced composite material 3D printing technology. The mesh reinforcements include annular reinforcements and longitudinal (diagonal) reinforcements, such as... Figure 3 As shown, Figure 3 This is a development diagram along the xy plane of the internal mesh rib structure of the reinforced cylindrical shell. In this embodiment, the number of annular ribs and longitudinal (diagonal) ribs are 2 and 20 respectively, that is, the number of annular ribs divided into m is 20, the number of mesh shape constraint points n is 4, the number of slice layers is represented by δ, the desired number of layers h is represented by 10, and the rib nodes are represented by n. i,j,δ i = 1, 2, 3, ... 20; j = 1, 2, 3, 4; δ = 1, 2, 3, ..., 10, n rib nodes i,j,δ The spatial coordinates are (x k ,y k ,z k ), where Z k =0.3δ; The coordinate information of the rib nodes is used for the forming design of the mesh rib structure, such as Figure 4 As shown, Figure 4 The diagram shows the unfolded structure of the outer skin of the reinforced cylindrical shell along the xy plane. In this embodiment, the length of the skin along the y-axis is 80mm, the unfolded length along the x-axis is 534mm, and the winding angle is approximately 0.08°. The skin node coordinate information is used for the forming design of the skin structure. The outer skin is formed using different rotational 3D printing reference surfaces under the same spatial coordinate system.

[0034] The grid rib structure employs different grid shapes, and by changing the coordinates (x, y) in each layer of the plane... k ,y k ), k=1,2,3,…,m×n, to achieve adjustment of the shape of the mesh ribs; in addition, the density of the mesh shape can be changed according to the axial load distribution of the stiffened cylindrical shell to achieve controllable design of load-bearing performance under different requirements;

[0035] 3) Based on the mesh rib shape information obtained in step 1) and the height and thickness information of the stiffened cylindrical shell obtained in step 2), the stiffened cylindrical shell is path-planned. The coordinate information of the closed contour is obtained in the Cartesian coordinate system. The x-axis direction of the Cartesian coordinate is replaced with the rotation direction. The 3D printing path of the stiffened cylindrical shell is generated based on the characteristics of rotary 3D printing.

[0036] Step 3) Specifically, based on the manufacturing process characteristics of rotary 3D printing of continuous carbon fiber reinforced composite materials, determine the corner radius r of the printing path. set and scanning spacing h set , make r set ≥R, h set ≤H, where R and H are the minimum fiber turning radius and maximum scanning spacing allowed in rotary 3D printing; based on the spatial coordinates of the nodes and the process characteristics of rotary 3D printing of the outer wall, the printing path of the mesh ribs is first generated, which consists of the outer contour path of the mesh shape and the rotary paths of the upper and lower widened ring ribs;

[0037] 4) Based on the total length L of the composite material rotary 3D printing path obtained in step 3) and the weight w1 of the composite material filament per unit length, calculate the theoretical weight w of the stiffened cylindrical shell structure. all , i.e. w all =L×w1; Based on the mesh rib shape information obtained in step 1) and the height and thickness information of the stiffened cylindrical shell obtained in step 2), the theoretical axial bearing critical load F1 of the stiffened cylindrical shell is obtained through simulation analysis in ABAQUS finite element simulation software. The load-to-mass ratio a of the composite material stiffened cylindrical shell is calculated, i.e. If the theoretical load-to-mass ratio of the stiffened cylindrical shell structure meets the lightweight requirements, then proceed to the next step of structural forming; if the theoretical load-to-mass ratio of the stiffened cylindrical shell structure does not meet the lightweight requirements, then redetermine the internal structural design parameters through steps 1) and 2), increase the desired number of mesh rib shapes h, and reduce the thickness of the stiffened cylindrical shell until the high load-to-mass ratio lightweight requirements of the stiffened cylindrical shell structure are met.

[0038] 5) Based on the above steps, the rotary 3D printing path for the stiffened cylindrical shell is obtained. Considering the working environment and strength requirements of the stiffened cylindrical shell, a suitable material system is selected. The corresponding composite material feed parameters and printhead movement speed are input. The outer skin is formed on the basis of the mesh rib structure. The stiffened cylindrical shell is then formed using a rotary 3D printing device. Figure 5 As shown, the motor 2 drives the cylindrical mold 3 to rotate through the optical axis 4, and the filament 5 and continuous carbon fiber 6 are melted, impregnated and extruded in the heating block 1 to complete the rotary 3D printing, thereby obtaining a lightweight cylindrical shell structure reinforced with continuous carbon fiber reinforced composite material.

[0039] Step 5) specifically involves: adjusting the position of the mesh ribs to constrain the spacing d between adjacent ribs in the outer skin's rotational printing direction. r , making d r ≤D, where D is the maximum allowable spacing distance for rotary 3D printing suspended forming; at this time, relying on the characteristics of rib support and continuous carbon fiber uninterrupted forming, the outer skin is directly rotary printed on the mesh ribs, realizing the rotary 3D printing forming of continuous carbon fiber reinforced composite stiffened cylindrical shell structure.

[0040] This embodiment focuses on a continuous carbon fiber reinforced composite material structure. Based on the shape of the internal mesh ribs and the requirements for axial load-bearing capacity, a stiffened cylindrical shell is formed by rotary 3D printing, resulting in the following: Figure 6 The diagram shows a rotary 3D printed continuous carbon fiber reinforced composite stiffened cylindrical shell structure.

[0041] like Figure 7 As shown, the axial compression critical load of the rhomboid mesh continuous carbon fiber reinforced composite stiffened cylindrical shell structure can reach up to 6822 N, and the load-to-mass ratio can reach up to 82.67 N / g. Compared with the unstiffened continuous carbon fiber reinforced composite cylindrical shell structure, the performance is improved by 197%. This method not only realizes the integration of stiffened cylindrical shell structure design and forming process, but also effectively solves the problem that the direction of 3D printing of continuous carbon fiber reinforcement cannot be printed along the axial load-bearing direction by using rotary 3D printing. Finally, it realizes the controllable design and rapid prototyping of continuous carbon fiber reinforced composite stiffened cylindrical shell structure with high specific performance, low cost and multiple material systems.

Claims

1. A method for rotary 3D printing of a continuous carbon fiber reinforced composite stiffened cylindrical shell structure, characterized in that, Includes the following steps: 1) Design the shape of the mesh ribs using Solidworks software; 2) Based on the shape of the mesh reinforcement obtained in step 1), and in combination with the load-bearing performance requirements of the reinforced cylindrical shell under working conditions, determine the height and thickness of the reinforced cylindrical shell; 3) Based on the mesh rib shape information obtained in step 1) and the height and thickness information of the stiffened cylindrical shell obtained in step 2), the stiffened cylindrical shell is path-planned. The coordinate information of the closed contour is obtained in the Cartesian coordinate system. The x-axis direction of the Cartesian coordinate is replaced with the rotation direction. The 3D printing path of the stiffened cylindrical shell is generated based on the characteristics of rotary 3D printing. 4) Based on the total length L of the composite material rotary 3D printing path obtained in step 3) and the weight of the composite material filament per unit length Calculate the theoretical weight of a stiffened cylindrical shell structure ,Right now Based on the mesh rib shape information obtained in step 1) and the height and thickness information of the stiffened cylindrical shell obtained in step 2), the theoretical critical axial load of the stiffened cylindrical shell is obtained through simulation analysis in finite element simulation software. Calculate the load-to-mass ratio 'a' of the composite reinforced cylindrical shell, i.e. If the theoretical load-to-mass ratio of the reinforced cylindrical shell structure meets the lightweight requirements, then proceed to the next step of structural forming. If the theoretical load-to-mass ratio of the stiffened cylindrical shell structure does not meet the lightweight requirements, the internal structural design parameters are redefined through steps 1) and 2), the desired number of mesh stiffener layers h is increased, and the thickness of the stiffened cylindrical shell is reduced until the high load-to-mass ratio and lightweight requirements of the stiffened cylindrical shell structure are met. 5) Based on the above steps, the rotary 3D printing path of the stiffened cylindrical shell is obtained. Combining the working environment and strength requirements of the stiffened cylindrical shell, the corresponding material system is selected, and the corresponding composite material feed parameters and printing nozzle moving speed are input. The outer skin is formed on the basis of the mesh rib structure. The stiffened cylindrical shell is formed by rotary 3D printing equipment, thus obtaining a lightweight structure of continuous carbon fiber reinforced composite stiffened cylindrical shell.

2. The rotary 3D printing method according to claim 1, characterized in that: Step 1) uses rectangular grids, triangular grids, and diamond grids as the basis for grid structure and rib forming.

3. The rotary 3D printing method according to claim 1, characterized in that: Step 2) The reinforced cylindrical shell is internally composed of mesh ribs fabricated using continuous carbon fiber reinforced composite material 3D printing technology. The mesh ribs include annular ribs and longitudinal or diagonal ribs. The number of annular ribs is m, the number of mesh shape constraint points is n, and the number of slice layers is expressed as follows: The desired number of layers is represented by h, and the stiffener nodes are represented by... , i=1,2,3,…m; j=1,2,3,…n; =1,2,3,…,h, rib nodes The spatial coordinates are ( , , ),in 0.3 The coordinate information of the rib nodes is used for the forming design of the mesh rib structure, and the outer skin is formed using different rotational 3D printing reference surfaces under the same spatial coordinate system.

4. The rotary 3D printing forming method according to claim 3, characterized in that: In step 2), the mesh rib structure employs different mesh shapes, and the coordinates within each layer of the plane are changed ( , The grid can be adjusted by setting k=1,2,3,…,m×n. In addition, the density of the grid can be changed according to the axial load distribution of the reinforced cylindrical shell to achieve controllable design of load-bearing performance under different requirements.

5. The rotary 3D printing method according to claim 1, characterized in that, Step 3) specifically involves: determining the turning radius of the 3D printing path based on the characteristics of rotary 3D printing of continuous carbon fiber reinforced composite materials. and scan spacing ,make , Where R and H are the minimum fiber turning radius and maximum scanning spacing allowed in rotary 3D printing; based on the spatial coordinates of the nodes and the process characteristics of rotary 3D printing of the outer wall, the printing path of the mesh ribs is first generated. The printing path consists of the outer contour path of the mesh shape and the rotary paths of the upper and lower widened ring ribs.

6. The rotary 3D printing method according to claim 1, characterized in that, Step 5) specifically involves: adjusting the position of the mesh ribs to constrain the spacing between adjacent ribs in the rotational printing direction of the outer skin. ,make Where D is the maximum allowable spacing distance for rotary 3D printing suspended forming; at this time, relying on the characteristics of rib support and continuous carbon fiber uninterrupted forming, the outer skin is directly rotary printed on the mesh ribs, realizing the rotary 3D printing forming of the continuous carbon fiber reinforced composite stiffened cylindrical shell structure.

7. The rotary 3D printing method according to claim 1, characterized in that: In step 5), the material system consists of different types of high-performance polymer materials such as polyimide (PA), polylactic acid (PLA), and polyether ether ketone (PEEK), which are selected according to the specific application requirements.

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