A design method of a folding strut lower strut based on carbon fiber three-dimensional weaving technology

Abstract

The application belongs to the technical field of three-dimensional weaving based on RTM process, and particularly relates to a folding strut lower strut design method based on carbon fiber three-dimensional weaving technology. The method comprises the following steps: determining the design requirements of the folding strut lower strut of the carbon fiber three-dimensional weaving technology, designing a folding strut lower strut scheme according to the design requirements; taking the outer curved surface of the folding strut lower strut as a reference, constructing a folding strut lower strut finite element model according to the folding strut lower strut scheme, and obtaining the lower strut load and constraint according to the folding strut mechanism form; performing structure regularization on the folding strut lower strut finite element model; performing three-dimensional weaving design according to the folding strut lower strut finite element model to obtain a preformed carbon fiber three-dimensional woven lower strut; integrally forming the preformed carbon fiber three-dimensional woven lower strut through the RTM process to obtain a carbon fiber three-dimensional woven lower strut product; and checking the carbon fiber three-dimensional woven lower strut product according to the lower strut load and constraint.

Description

Technical Field

[0001] This application belongs to the field of three-dimensional weaving technology based on RTM process, and specifically relates to a design method for the lower strut of a folding strut based on carbon fiber three-dimensional weaving technology. Background Technology

[0002] The landing gear assembly is a crucial load-bearing and controllable component of an aircraft, playing a vital role in safe takeoff and landing. Its performance directly impacts the aircraft's usability and safety. The folding strut is the lower landing gear lock, securing the landing gear in the deployed position. It is one of the most important load-bearing structures in the landing gear assembly, its function being to lock the landing gear in the deployed position.

[0003] Currently, most landing gear lower strut structures in China are made of titanium alloy. Although their performance meets the design requirements, they are expensive to manufacture, have long production cycles, and are heavy, making them unable to meet the increasingly stringent weight requirements for landing gear. Therefore, how to design lightweight folding struts for landing gear is of great significance.

[0004] Therefore, there is an urgent need for a technical solution to overcome or mitigate at least one of the aforementioned defects in the existing technology. Summary of the Invention

[0005] The purpose of this application is to provide a design method for the lower strut of a folding strut based on carbon fiber three-dimensional weaving technology, so as to solve at least one problem existing in the prior art.

[0006] The technical solution of this application is:

[0007] A method for designing the lower strut of a folding strut based on carbon fiber three-dimensional weaving technology includes:

[0008] Step 1: Determine the design requirements for the lower strut of the folding strut using carbon fiber three-dimensional weaving technology, and design the lower strut scheme based on the design requirements.

[0009] Step 2: Using the outer curved surface of the lower folding strut as a reference, construct a finite element model of the lower folding strut according to the folding strut lower strut scheme, and obtain the load and constraints of the lower strut according to the folding strut mechanism form;

[0010] Step 3: Perform structural regularization on the finite element model of the lower folding strut;

[0011] Step 4: Perform three-dimensional weaving design based on the finite element model of the folded strut lower strut to obtain the pre-formed three-dimensional woven carbon fiber lower strut;

[0012] Step 5: The pre-formed carbon fiber three-dimensional braided lower support rod is integrally molded using RTM process to obtain the carbon fiber three-dimensional braided lower support rod product;

[0013] Step 6: Verify the carbon fiber three-dimensional braided lower support product based on the load and constraints of the lower support.

[0014] In at least one embodiment of this application, in step one, the design requirements include weight reduction requirements, functional requirements, and installation space requirements.

[0015] In at least one embodiment of this application, step three, which involves structural normalization of the finite element model of the lower strut of the folding strut, includes:

[0016] The weak areas of the finite element model of the lower strut of the folded strut are reinforced;

[0017] Remove the original weight reduction holes in the finite element model of the lower folding strut;

[0018] The structural dimensions of the finite element model of the lower strut of the folded strut are normalized.

[0019] In at least one embodiment of this application, step four, which involves performing a three-dimensional braiding design based on the finite element model of the folded strut lower strut to obtain a pre-formed carbon fiber three-dimensional braided lower strut, includes:

[0020] The lower support rod end is woven using a three-dimensional weaving process, and then the end is assembled with the foam core to obtain the combination of the end and the foam core;

[0021] A two-dimensional weaving process is used to weave circumferential lay-ups on the assembly;

[0022] A pre-shaped assembly is obtained by laying reinforcing layers on both sides of the assembly using unidirectional fabric and performing a pre-shaped treatment.

[0023] The outer layer of fibers is woven onto the pre-shaped assembly using a three-dimensional weaving process to obtain a pre-formed carbon fiber three-dimensional woven lower support rod.

[0024] In at least one embodiment of this application, in step five, the pre-formed carbon fiber three-dimensional braided lower support rod is integrally molded using an RTM process to obtain a carbon fiber three-dimensional braided lower support rod product, including:

[0025] The pre-formed carbon fiber three-dimensional braided lower support rod is placed in the mold of the RTM process molding system. After mold closing, glue injection, curing, and demolding, the connecting holes and assembly holes are processed to obtain the carbon fiber three-dimensional braided lower support rod product.

[0026] In at least one embodiment of this application, the RTM process molding system includes:

[0027] A mold having a glue inlet and a glue outlet;

[0028] An injection device containing resin, the injection device being connected to the resin inlet via a resin inlet pipe;

[0029] A resin recovery device, wherein the resin recovery device is connected to the glue outlet via a glue outlet pipeline;

[0030] A vacuum device, which is connected to the resin recovery device via a vacuum pipeline.

[0031] The invention has at least the following beneficial technical effects:

[0032] The design method for the lower strut of the folding strut based on carbon fiber three-dimensional braiding technology in this application, based on the carbon fiber three-dimensional braiding lower strut formed by RTM process, has excellent interlayer and intralayer mechanical properties. It not only overcomes the inherent shortcomings of traditional composite materials, but also has advantages such as corrosion resistance, fatigue resistance, high strength and high stiffness, low density and excellent toughness. It is a key direction for the future development of composite material technology and can solve the problem of lightweighting of landing gear folding struts. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating the design requirements of the lower strut of a folding strut according to one embodiment of this application;

[0034] Figure 2 This is a schematic diagram of a folding strut lower strut scheme according to one embodiment of this application;

[0035] Figure 3 This is a schematic diagram of the RTM process flow according to one embodiment of this application. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0037] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this application.

[0038] The following is in conjunction with the appendix Figures 1 to 3 This application will be described in further detail.

[0039] This application provides a design method for the lower strut of a folding strut based on carbon fiber three-dimensional weaving technology, including the following steps:

[0040] Step 1: Determine the design requirements for the lower strut of the folding strut using carbon fiber 3D weaving technology, and design the lower strut scheme based on the design requirements;

[0041] Step 2: Using the outer curved surface of the lower folding strut as a reference, construct a finite element model of the lower folding strut according to the lower folding strut scheme, and obtain the load and constraints of the lower strut according to the form of the folding strut mechanism.

[0042] Step 3: Perform structural regularization on the finite element model of the lower strut of the folding strut;

[0043] Step 4: Perform three-dimensional braiding design based on the finite element model of the folded strut lower strut to obtain the pre-formed three-dimensional braided carbon fiber lower strut;

[0044] Step 5: The pre-formed carbon fiber three-dimensional braided lower support rod is integrally molded using the RTM process to obtain the carbon fiber three-dimensional braided lower support rod product.

[0045] Step 6: Verify the carbon fiber three-dimensional braided lower support product based on the load and constraints of the lower support.

[0046] This application discloses a design method for the lower strut of a folding strut based on carbon fiber three-dimensional weaving technology. Firstly, in step one, the design requirements for the lower strut of the folding strut using carbon fiber three-dimensional weaving technology are clarified, such as... Figure 1 As shown. The design requirements for the lower strut of the folding strut include weight reduction, functional requirements, and installation space requirements. New materials and processes are used to optimize the design of the lower strut of the folding strut, including structural design, material selection, and process design. This ensures that the lower strut design meets requirements for interface, strength, equal stiffness, lightweight, economy, and load-bearing capacity.

[0047] This application discloses a design method for the lower strut of a folding strut based on carbon fiber three-dimensional weaving technology. Secondly, in step two, using the outer curved surface of the lower strut as a reference, a finite element model of the lower strut is constructed according to the lower strut design scheme. Figure 2 As shown. The actual load and constraints of the lower strut are obtained based on the form of the folding strut mechanism.

[0048] This application discloses a design method for the lower strut of a folding strut based on carbon fiber three-dimensional braiding technology. In step three, while ensuring that the original function, interface position, and dimensions remain unchanged, the finite element model of the lower strut is structurally regularized. This mainly includes: reinforcing the weak areas of the finite element model of the lower strut to ensure continuous carbon fiber arrangement in the three-dimensional braided structure; and removing the original weight-reduction holes from the finite element model of the lower strut. The structural dimensions of the finite element model of the lower strut are regularized to ensure that the structural dimensions are as regular as possible to facilitate composite material molding.

[0049] The design method for the lower strut of a folding strut based on carbon fiber three-dimensional braiding technology in this application further includes, in step four, performing three-dimensional braiding design based on the finite element model of the lower strut of the folding strut to obtain a pre-formed carbon fiber three-dimensional braided lower strut, including:

[0050] The lower support rod end is woven using a three-dimensional weaving process, and then assembled with the foam core to obtain a combination of the end and the foam core;

[0051] A two-dimensional weaving process is used to weave circumferential lay-ups on the composite material;

[0052] A pre-shaped assembly is obtained by covering both sides of the assembly with a unidirectional fabric and performing a pre-forming process.

[0053] The outer layer of fibers is woven onto a pre-shaped assembly using a three-dimensional weaving process to obtain a pre-formed carbon fiber three-dimensional woven lower support rod.

[0054] In the preferred embodiment of this application, the following optimized design method can be adopted in the three-dimensional weaving design process:

[0055] 1. 3D weaving optimization of end precast bodies

[0056] To address the complex geometry of the end preform, an optimized three-dimensional weaving process was employed. By adjusting the weaving parameters and fiber orientation, a tight fit between the end preform and the foam core was ensured, while simultaneously improving the load-bearing capacity of the end area. This process utilizes the penetrating properties of the weaving fibers to achieve multi-point connections between the end preform and the foam core, further enhancing the overall structural stability.

[0057] 2. Gradual transition design of circumferential ply

[0058] In the fabrication of the circumferential layup using a two-dimensional braiding process on the combination of foam core and end preform, a gradual transition design theory was introduced. By controlling the thickness and fiber density of the circumferential layup, a smooth transition region was formed between the circumferential layup and the end preform, avoiding stress concentration phenomena that may occur in traditional layup processes. This approach significantly improves the fatigue resistance of the lower strut model.

[0059] 3. Multi-level composite design theory of three-dimensional braided structures

[0060] A multi-level composite structure design method is preferred, achieving a multi-level composite three-dimensional braided structure through layered stacking. This method leverages the characteristics of three-dimensional braiding technology, layering circumferential and axial reinforcement layers on top of the end prefabricated body and foam core, ultimately forming a lower strut model with complex geometry and high performance. This layered composite design not only improves the strength and durability of the structure but also significantly reduces the defect rate during manufacturing.

[0061] 4. Optimization of preform coefficient in fabric laying

[0062] During the application of the reinforcing layers on both sides, a pre-forming coefficient optimization method was employed. Through theoretical calculations and experimental verification, the optimal range of the pre-forming coefficient was determined, ensuring uniform stress distribution on the unidirectional fabric during application and preventing wrinkles or slippage. This method not only improves the application quality of the reinforcing layers but also guarantees a good match between the pre-formed fabric and the circumferential layup.

[0063] 5. Embedded reinforcement mechanism of high-performance fiber materials

[0064] High-performance fiber materials were introduced during the application of the reinforcing layers on both sides, defining an embedded reinforcement mechanism. By optimizing the type and arrangement of the fiber materials, the unidirectional fabric can achieve a uniform distribution of fiber materials during the pre-forming stage. This approach not only improves the load-bearing capacity of the reinforcing layers but also enhances their resistance to deformation under complex stress environments.

[0065] 6. Composite reinforcement mechanism of multi-layer braided structure

[0066] A composite reinforcement mechanism based on three-dimensional and two-dimensional braiding is employed. By controlling the braiding angles of the circumferential lay-ups and axial reinforcing layers, the multi-layered braided structure achieves a synergistic reinforcement effect in different directions. This approach significantly improves the impact and bending resistance of the lower strut model, enabling it to meet complex mechanical performance requirements.

[0067] 7. Synergistic Implementation of Weight Reduction and Structural Optimization Design

[0068] To meet the requirements of lightweight design, a weight reduction and structural optimization design method based on three-dimensional weaving technology was adopted. By precisely controlling the weaving parameters and material distribution, the lower strut model was made lighter while maintaining its mechanical properties. This method combines theoretical analysis and experimental verification to ensure the feasibility and reliability of the lightweight design.

[0069] 8. Numerical simulation and experimental verification of the three-dimensional weaving process

[0070] Numerical simulation technology was used to conduct a detailed study of the three-dimensional weaving process, focusing on the fiber arrangement and stress distribution during weaving. Experiments were conducted to verify the accuracy of the numerical simulation results and further optimize the weaving process parameters. This approach not only improves the efficiency of the three-dimensional weaving process but also provides a reliable theoretical basis for subsequent structural design.

[0071] 9. Cooperative weaving mechanism of circumferential lay-up and axial reinforcement layer

[0072] A collaborative weaving mechanism combining circumferential layups and axial reinforcing layers is employed. Optimizing the weaving sequence and process parameters ensures a proper match between the fiber orientations of the circumferential layups and the axial reinforcing layers. This approach improves the overall performance of the multi-layered woven structure.

[0073] 10. Modular Design

[0074] The three-dimensional weaving process of the lower strut model is decomposed into independent modules such as the two side reinforcing layers and the ring fabric, which are then assembled to improve the manufacturing efficiency.

[0075] In the design method of the folding strut lower strut based on carbon fiber three-dimensional braiding technology of this application, step five involves integrally molding the pre-formed carbon fiber three-dimensional braided lower strut using RTM process to obtain a carbon fiber three-dimensional braided lower strut product, including:

[0076] The pre-formed carbon fiber three-dimensional braided lower support rod is placed in the mold of the RTM process molding system. After mold closing, glue injection, curing, and demolding, the connecting holes and assembly holes are processed to obtain the carbon fiber three-dimensional braided lower support rod product.

[0077] like Figure 3 As shown, the RTM (Resin Transformation) molding system includes: a mold, an injection unit, a resin recovery unit, and a vacuum unit. The mold has a sprue and a discharge port; the injection unit contains resin and is connected to the sprue via a sprue pipe; the resin recovery unit is connected to the discharge port via a discharge pipe; and the vacuum unit is connected to the resin recovery unit via a vacuum pipe. After the product is molded using the RTM system, the connecting holes and assembly holes are machined based on the final digital model to obtain the final product.

[0078] In the design method of the folding strut under the folding strut based on the three-dimensional weaving technology of carbon fiber in this application, in step six, the carbon fiber three-dimensional weaving under the folding strut product obtained by applying this method is checked according to the load and constraints obtained in step two. It shows that the carbon fiber three-dimensional weaving under the folding strut can transfer the ground load well and ensure that the structure does not become unstable or damaged under the load.

[0079] This application presents a design method for the lower strut of a folding strut based on three-dimensional carbon fiber weaving technology. This method represents the first application of carbon fiber composite materials in folding struts. It utilizes a multi-layered fiber preform microstructure optimization design, employing lightweight, highly vibration-damping foam to absorb the impact force during landing, lateral unidirectional lay-up to enhance axial stiffness and strength, and three-dimensional weaving to achieve excellent overall mechanical properties, resulting in superior vibration damping and load-bearing performance. This effectively meets the requirements of high strength, impact resistance, vibration damping, and lightweight design for the lower strut of a landing gear folding strut.

[0080] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A design method for a folding strut lower support based on carbon fiber three-dimensional weaving technology, characterized in that, include: Step 1: Determine the design requirements for the lower strut of the folding strut using carbon fiber three-dimensional weaving technology, and design the lower strut scheme based on the design requirements. Step 2: Using the outer curved surface of the lower folding strut as a reference, construct a finite element model of the lower folding strut according to the folding strut lower strut scheme, and obtain the load and constraints of the lower strut according to the folding strut mechanism form; Step 3: Perform structural regularization on the finite element model of the lower folding strut; Step 4: Perform three-dimensional weaving design based on the finite element model of the folded strut lower strut to obtain the pre-formed three-dimensional woven carbon fiber lower strut; Step 5: The pre-formed carbon fiber three-dimensional braided lower support rod is integrally molded using RTM process to obtain the carbon fiber three-dimensional braided lower support rod product; Step 6: Verify the carbon fiber three-dimensional braided lower support product based on the load and constraints of the lower support.

2. The design method for the lower strut of a folding strut based on carbon fiber three-dimensional weaving technology according to claim 1, characterized in that, In step one, the design requirements include weight reduction requirements, functional requirements, and installation space requirements.

3. The design method for the lower strut of a folding strut based on carbon fiber three-dimensional weaving technology according to claim 2, characterized in that, Step three involves structural normalization of the finite element model of the lower folding strut, including: The weak areas of the finite element model of the lower strut of the folded strut are reinforced; Remove the original weight reduction holes in the finite element model of the lower folding strut; The structural dimensions of the finite element model of the lower strut of the folded strut are normalized.

4. The design method for the lower strut of a folding strut based on carbon fiber three-dimensional weaving technology according to claim 3, characterized in that, In step four, a three-dimensional braiding design is performed based on the finite element model of the folded strut lower support to obtain a pre-formed three-dimensional braided carbon fiber lower support, including: The lower support rod end is woven using a three-dimensional weaving process, and then the end is assembled with the foam core to obtain the combination of the end and the foam core; A two-dimensional weaving process is used to weave circumferential lay-ups on the assembly; A pre-shaped assembly is obtained by laying reinforcing layers on both sides of the assembly using unidirectional fabric and performing a pre-shaped treatment. The outer layer of fibers is woven onto the pre-shaped assembly using a three-dimensional weaving process to obtain a pre-formed carbon fiber three-dimensional woven lower support rod.

5. The design method for the lower strut of a folding strut based on carbon fiber three-dimensional weaving technology according to claim 4, characterized in that, In step five, the pre-formed carbon fiber three-dimensional braided lower support rod is integrally molded using RTM technology to obtain the carbon fiber three-dimensional braided lower support rod product, including: The pre-formed carbon fiber three-dimensional braided lower support rod is placed in the mold of the RTM process molding system. After mold closing, glue injection, curing, and demolding, the connecting holes and assembly holes are processed to obtain the carbon fiber three-dimensional braided lower support rod product.

6. The design method for the lower strut of a folding strut based on carbon fiber three-dimensional weaving technology according to claim 5, characterized in that, The RTM process molding system includes: A mold having a glue inlet and a glue outlet; An injection device containing resin, the injection device being connected to the resin inlet via a resin inlet pipe; A resin recovery device, wherein the resin recovery device is connected to the glue outlet via a glue outlet pipeline; A vacuum device, which is connected to the resin recovery device via a vacuum pipeline.

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