Multi-branched, spherical crown, flanged precast structure and its three-dimensional weaving method

Abstract

This invention discloses a three-dimensional weaving method for a multi-branched prefabricated structure containing a spherical crown and a flange. The method includes: weaving the spherical crown using a three-dimensional six-directional or three-dimensional seven-directional weaving method, reserving yarn during the weaving process; weaving the flange using the same method based on the woven spherical crown; and weaving the branch structure using a three-dimensional five-directional weaving method with the yarn reserved during the spherical crown weaving process, thus obtaining the multi-branched prefabricated structure containing a spherical crown and a flange. This invention also discloses a multi-branched prefabricated structure containing a spherical crown and a flange obtained using the above weaving method. This invention enables three-dimensional weaving of multi-branched prefabricated structures containing a spherical crown and a flange, with a simple process that improves product quality and performance.

Description

Technical Field

[0001] This invention belongs to the field of composite material manufacturing and relates to a multi-branched prefabricated structure containing a spherical crown and a flange, and its three-dimensional weaving method. Background Technology

[0002] Three-dimensional weaving technology is applicable to the preparation of almost all types of fiber preforms. Composite materials manufactured through three-dimensional weaving and liquid molding processes possess excellent comprehensive mechanical properties. By planning different three-dimensional weaving trajectories and designing different weaving parameters, the mechanical properties of three-dimensional woven composite materials can be further oriented to match their shape characteristics and operating conditions. With the development of weaving equipment, the shapes of preforms that can be woven are becoming more complex, and many irregularly shaped preforms can be woven into near-net-shape preforms in a single operation. Therefore, the improvement in the capabilities of weaving equipment and human assistance have given more options for the weaving structure of three-dimensional woven composite parts.

[0003] In the product front-end design stage, in addition to designing the shape of the composite material part, the design of its braided structure is equally crucial, as it directly affects the performance of the part. The design of the prefabricated braided structure is mainly achieved through the design of braiding parameters, including: three-dimensional N-axis braiding, fiber specifications, knot length, braiding angle, and the number of braiding rows and columns determined according to the size of the prefabricated body.

[0004] Aerospace products generally require lightweight and high-strength materials, and many structural products have begun to use three-dimensional braided composite materials. However, due to the inherent complexity of some irregularly shaped structural components, fabrication using three-dimensional braiding methods presents certain difficulties, resulting in limited experience and reference points for their composite design methods. Irregularly shaped structural components, such as typical aerospace main support connection structures, have the following characteristics: 1. They contain multiple branches, each used to connect different interfaces; 2. They include flange structures to fix the structures connected to each interface to a main structure; 3. The transition areas between each branch and the flange are often arc-shaped or circular spherical caps, a configuration more adaptable to complex mechanical environments.

[0005] Due to production capacity limitations, most of these connection structures are made of metal materials. However, because metals have a high coefficient of thermal expansion, the dimensional accuracy of each interface cannot be guaranteed in the alternating hot and cold environment of space. In addition, due to their heavy weight, fiber prepreg layup processes have gradually begun to be used as a composite material alternative. However, as functions increase, interface loads become more complex, and interface accuracy requirements become more stringent. Laminated composite materials have exposed delamination problems under complex mechanical environments. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned defects and provide a multi-branched, spherical crown, flanged prefabricated structure and its three-dimensional weaving method. This invention solves the technical problem of delamination of irregular structural parts prepared by traditional methods under complex mechanical environments. This invention can realize the three-dimensional weaving of multi-branched, spherical crown, flanged prefabricated structures. The process is simple and conducive to improving the quality and performance of products.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] A three-dimensional weaving method for a multi-branched, spherical crown, flange-shaped precast structure, comprising:

[0009] The spherical crown is woven using a three-dimensional six-way weaving method or a three-dimensional seven-way weaving method, with yarn reserved during the weaving process;

[0010] Based on the woven spherical crown, the flange is woven using a three-dimensional six-way weaving method or a three-dimensional seven-way weaving method;

[0011] Using the yarn reserved during the weaving of the spherical crown, a three-dimensional five-directional weaving method is used to weave the branch structure, resulting in a multi-branched prefabricated structure containing a spherical crown and a flange.

[0012] Furthermore, the weaving method for the spherical crown and the flange is the same.

[0013] Furthermore, in the three-dimensional five-directional weaving method, the first four directions are the weaving yarn directions, and the fifth direction is the direction along the weaving progress;

[0014] In the three-dimensional six-directional weaving method, the first four directions are the direction of the weaving yarn, the fifth direction is along the direction of weaving, and the sixth direction is along the circumference.

[0015] In the three-dimensional seven-directional weaving method, the first four directions are the direction of the weaving yarn, the fifth direction is along the direction of weaving forward, the sixth direction is along the circumference, and the seventh direction is along the thickness direction.

[0016] Furthermore, when weaving the spherical crown, the number of weaving rows should be ≤500 bundles, and the number of weaving yarn layers * number of rows should be ≤2000 bundles.

[0017] Furthermore, when weaving the spherical crown, the method for determining the yarn weaving angle is as follows:

[0018] The load borne by the joint is divided into a load P1 parallel to the flange surface and a load P2 perpendicular to the flange surface. When P1≥P2, the braiding angle range is 50°~60°. When P1<P2, the braiding angle range is 30°~40°. The joint is a joint prepared using a prefabricated body.

[0019] Furthermore, based on the number of weave rows m and the weave angle θ, the number of weave nodes h is determined according to the following formula:

[0020] S = h * tanθ * m;

[0021] Where S represents the perimeter of the braided cross section.

[0022] Furthermore, when braiding the flange, the number of braided rows ≤ 500 bundles, and the number of braided yarn layers * number of rows ≤ 2000 bundles;

[0023] When braiding the flange, the yarn braiding angle is 30° to 50°.

[0024] Furthermore, when weaving the branch structure, the yarn weaving angle is 30° to 40°.

[0025] A multi-branched prefabricated structure with a spherical crown and a flange is obtained using the above-mentioned three-dimensional weaving method.

[0026] Compared with the prior art, the present invention has at least one of the following advantages:

[0027] (1) This invention proposes for the first time a weaving method for a multi-branched precast body with a spherical crown and flange structure. The method weaves different structures in the precast body according to their characteristics and stresses, and finally forms a precast body with stable quality.

[0028] (2) This invention provides weaving parameters for branches, spherical crowns, and flanges. Using these weaving parameters is beneficial for the rapid design of textile composite products with this configuration.

[0029] (3) The present invention has broad application prospects. The prefabricated internal fiber bundles are interwoven in the layers and between layers, which makes the part have integrity, avoids the occurrence of delamination defects, and can adapt to complex mechanical environment. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a two-branch joint with a spherical crown and a flange structure.

[0031] Figure 2 This is a schematic diagram of the weaving process of the spherical crown of the present invention. Detailed Implementation

[0032] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0033] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0034] Three-dimensional weaving equipment is mostly non-standard equipment. Both domestic and foreign research institutions and equipment manufacturers have developed textile equipment with diverse functions, high automation, flexibility, and a large yarn loading capacity. This has greatly increased the designability of irregular fiber preforms.

[0035] One typical structural form of prefabricated structures is as follows: Figure 1 As shown, taking two branch pipes (two branches) as an example, each branch pipe is connected to a spherical crown, and below the spherical crown is a flange structure. This type of component is often used in connection joints. The three-dimensional braiding parameter design method proposed in this invention is applicable to the preparation of irregular precast bodies. The braiding parameters can be adjusted according to the function and appearance dimensional adaptability of different parts of different precast bodies, so as to reduce the requirements on equipment capabilities and improve feasibility.

[0036] This invention is based on a four-step weaving machine. First, the direction of weaving for each part is determined according to the structural characteristics of different parts of the workpiece. Then, the yarn specifications are determined according to the outer dimensions and wall thickness of the fabric. The weaving angle is determined according to the working conditions of the workpiece, and then the length of the knot is determined.

[0037] This invention proposes a three-dimensional weaving method for weaving multi-branched fiber preforms with spherical crowns and flange structures. The resulting composite material main support joint has excellent characteristics of being lightweight, high-strength, and having a low expansion rate. Since the joints between different parts are the weakest and most likely to fail, the preform design method described in this invention involves integrated weaving, ensuring the continuity of fibers at the weakest points of the joints, and then molding it using RTM (Resin Transfer Molding) technology.

[0038] This invention designs three-dimensional weaving parameters for multi-branched fiber preforms with spherical crowns and flange structures, and divides them into three parts according to the main structure:

[0039] (1) The spherical crown is a transition structure between the branch and the flange, and it bears complex loads. It is generally designed as an arc or circular structure and is prefabricated using a three-dimensional weaving method. Considering its complex stress conditions, it needs to be designed as a three-dimensional six- or seven-directional weaving, where four directions are the weaving yarn directions, the fifth direction is the axis yarn direction (along the weaving forward direction), and the sixth direction is along the circumference of the spherical crown (refer to...). Figure 2The first direction is the circumferential direction (6-way), and the seventh direction is the yarn along its wall thickness. A three-dimensional six-way weaving structure can meet general operating conditions. However, if there are strict requirements for product weight, wall thickness, and mechanical properties, a three-dimensional seven-way weaving should be considered. Three-dimensional woven fabrics have a spatial mesh-like overall structure, and the resulting textile composite material can be approximated as an isotropic material, thus being less affected by load variations. Based on the product's dimensions and the yarn loading capacity of the weaving equipment, and considering the yarn specifications used, the number of weaving rows is generally controlled below 500 bundles, and the number of weaving yarn layers * number of rows is controlled below 2000 bundles. When the number of yarns used exceeds 2000 bundles, yarns with a higher denier or yarn plying should be considered. Finally, the yarn braiding angle is determined based on the actual operating conditions. The selection method is as follows: when the load on the joint is mainly parallel to the flange surface, the braiding angle range is 50° to 60°; when the load on the joint is mainly perpendicular to the flange surface, the braiding angle range is 30° to 40°; if the load is more complex, it is generally selected as 40° to 50°. After the number of braid rows and the braiding angle are determined, the number of braided knots is determined accordingly. At this time, the coverage rate of the yarn on a single layer of the product should be considered. If the coverage rate does not meet the requirements, the number of braid rows and the number of braided knots should be adjusted appropriately. Generally, the relationship between the three is: S = h * tanθ * m, where S represents the perimeter of the braided section, h represents the number of braided knots, θ represents the braiding angle, and m represents the number of braid rows.

[0040] (2) The flange provides an important connection interface, fixing the loads of each branch connected to the joint to the main structure. The flange is a planar structure, and its weaving direction (three-dimensional six-way or three-dimensional seven-way) needs to be determined based on overall weight, wall thickness, and mechanical requirements. The fifth direction is the axial yarn direction (along the weaving advance direction), the sixth direction is along the flange circumference, and the seventh direction is along the thickness direction. Alternatively, unless there are special load requirements, the flange weaving direction can be consistent with that of the spherical crown, i.e., all three-dimensional six-way weaving or all three-dimensional seven-way weaving. Similarly, based on the product's external dimensions and the yarn loading capacity of the weaving equipment, and considering the yarn specifications used, the number of weaving rows is generally controlled below 500 bundles, and the number of weaving yarn layers * number of rows is controlled below 2000 bundles. When the number of yarns used exceeds 2000 bundles, a higher denier yarn or a yarn ply form should be considered. Due to the weaving difficulty and operating conditions, the weaving angle of the prefabricated body at the flange is selected as 30°–50°. Once the number of weaving rows and the weaving angle are determined, the number of weaving knots is determined accordingly. At this point, the coverage of the yarn on a single layer of the product should be considered. If the coverage does not meet the requirements, the number of weaving rows and the number of weaving knots should be adjusted appropriately.

[0041] (3) Branch structures can be round, square, or polygonal cross-section tubes, and their weaving methods are similar. Since the branch structure provides a load installation interface, the connection method is generally adhesive or screw. It has high requirements for axial stiffness along the generatrix direction. Therefore, the branch weaving adopts three-dimensional five-directional weaving, that is, adding axial yarn on the basis of the braided yarn. The branch weaving yarn comes from the yarn reserved during the crown weaving. According to the branch cross-section and wall thickness, the amount of yarn to be reserved when the crown is woven to the branch position is determined. For this type of part, the total number of braided yarns used in the branch is generally less than the number of crown weavings, so there is no need to add yarn. The branch weaving can continue the crown weaving. Since the branch has certain requirements for axial stiffness, a small angle weaving is generally selected, and the angle is generally selected as 30-40°. After the number of weaving rows and the weaving angle are determined, the number of weaving knots is determined accordingly. At this time, the coverage rate of the yarn on the single layer of the product should be considered. If the coverage rate does not meet the requirements, the number of weaving rows and the number of knots should be adjusted appropriately.

[0042] The above describes the process for determining the three-dimensional weaving parameters of multi-branched fiber preforms with spherical crowns and flange structures. Specific parameters (such as the number of weaving layers and columns) need to be determined based on actual operating conditions and trial production results.

[0043] Example:

[0044] The following is a detailed explanation using a two-branch main load-bearing connection structure as an example.

[0045] The two branch pipes are the same size, with a wall thickness of 3mm and an inner diameter of 60mm; the spherical crown structure has a wall thickness of 6mm and an inner diameter of 130mm; the flange structure has a thickness of 5mm and an outer edge diameter of 175mm. The braided fiber raw material is T800-6K. According to the shape characteristics of the precast body, the weaving sequence is: spherical crown → flange → branch pipe.

[0046] (1) Crown

[0047] like Figure 1 As shown, the spherical crown is a thin-walled spherical structure that connects the flange and the branch pipe, and is an important force transmission component. Its force direction is complex and the load distribution is uneven. Therefore, based on four-way weaving, axial and circumferential yarns (directions such as...) are added. Figure 2 As shown in the figure, the final spherical crown was determined to be a three-dimensional six-directional weave.

[0048] Depending on the raw material selection, T800-6K monofilament bundle fiber weaving can be used if the equipment's yarn loading capacity is sufficient. To reduce the equipment's yarn loading capacity, this invention proposes a yarn plying method, which is equivalent to thickening a single bundle of fiber, thus reducing the number of yarn carriers used in the equipment. Taking 4-ply fiber as an example: the inner diameter of the spherical crown is 130mm, and the wall thickness is 6mm. Considering the fiber elasticity and the compaction degree of the RTM mold in the prefabricated state, the prefabricated body weaving thickness is set to 6.5mm, and the spherical crown weaving length along the weaving direction is approximately 95mm. Therefore, the initial arrangement of the number of columns and layers of the weaving yarn and the axial yarn is 0 columns × (4 layers + 3 layers), and the final arrangement is 246 columns × (4 layers + 3 layers). During this process, the six-phase yarn is added layer by layer.

[0049] To maintain consistent overall mechanical properties while considering equipment operating space and difficulty, a 35° weaving angle is chosen for the crown. Combined with the number of yarn rows, the weaving knot length for the crown is determined to be approximately 5mm. Based on the knot length and the thickness of the 4-ply fibers, the above weaving parameters achieve 100% in-plane weaving coverage while meeting wall thickness requirements.

[0050] (2) Flange

[0051] Flanges are often used to provide important load-bearing interfaces, and their prefabricated weaving parameters need to be designed specifically for complex stress conditions. Axial and circumferential yarns are added to the four-way yarn.

[0052] Since the flange is connected to the spherical crown, the flange weaving and the spherical crown weaving are carried out in sequence. When the spherical crown weaving is finished, the flange weaving begins. Therefore, the initial arrangement of the number of columns and layers of the weaving yarn and the axial yarn of the flange is 246 columns × (4 layers + 3 layers). During the weaving process, the six-way yarn is added layer by layer.

[0053] The same 35° weaving angle and 5mm knot length as the spherical crown are used. Since the flange outer diameter is 175mm, the thickness becomes 5mm (5.5mm for the prefabricated body). The yarn arrangement at the end is set to 300 columns × (4 layers + 2 layers). The above weaving parameters can also meet the requirements for in-plane coverage and wall thickness.

[0054] (3) Branch pipe

[0055] The present invention is illustrated in the example of two branch pipes, but in actual implementation, it may include three or more branch pipes. The branch pipes are thin-walled structures and are interlocked with other rod structures during use. Therefore, in addition to the four-way braided yarn, the branch pipes are required to be structurally reinforced along their length to improve the tensile strength and overall stiffness. Ultimately, the branch pipes are selected using a three-dimensional five-way braiding method.

[0056] When knitting the ball crown, the branch yarn needs to be reserved at the corresponding position of the branch. The number of reserved yarns should be based on the design results of the following parameters.

[0057] The branch pipe has an inner diameter of 60mm and a wall thickness of 3mm. Considering fiber elasticity and the compaction degree of the RTM mold in the prefabricated state, the prefabricated braiding thickness is set to 3.5mm. The branch pipe wall thickness and diameter remain unchanged, so the number of yarns arranged at the beginning and end of the braiding is the same, which is 120 rows × (3 layers + 1 layer). The braiding angle and the length of the knot remain unchanged, still 35° and 5mm respectively. Similarly, the above braiding parameters can also meet the requirements of in-plane coverage and wall thickness.

[0058] Note: The above three-dimensional weaving parameter design is only for this embodiment. In actual implementation, the corresponding parameter design and adjustment can be made according to the different shapes and sizes of the parts, such as multiple branches (more than 2 branches), changes in the shape of the spherical crown (polyhedral spherical crown or no spherical crown), and changes in the shape of the flange (polygonal flange). Similarly, different yarn specifications and yarn arrangement can be determined according to the fiber type (thickness).

[0059] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0060] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A three-dimensional weaving method for a multi-branched, precast structure containing a spherical crown and a flange, characterized in that, include: The spherical crown is woven using a three-dimensional six-way weaving method or a three-dimensional seven-way weaving method, with yarn reserved during the weaving process; Based on the woven spherical crown, the flange is woven using a three-dimensional six-way weaving method or a three-dimensional seven-way weaving method; Using the yarn reserved during the weaving of the spherical crown, a three-dimensional five-directional weaving method is used to weave the branch structure, resulting in a multi-branched prefabricated structure containing a spherical crown and a flange. The spherical crown and the flange are woven in the same way; In the three-dimensional five-directional weaving method, the first four directions are the direction of the weaving yarn, and the fifth direction is the direction along the weaving progress. In the three-dimensional six-directional weaving method, the first four directions are the direction of the weaving yarn, the fifth direction is along the direction of weaving, and the sixth direction is along the circumference. In the three-dimensional seven-directional weaving method, the first four directions are the direction of the weaving yarn, the fifth direction is along the direction of weaving forward, the sixth direction is along the circumference, and the seventh direction is along the thickness direction.

2. The three-dimensional weaving method for a multi-branched, crown- and flange-type prefabricated structure according to claim 1, characterized in that, When weaving the spherical crown, the number of weaving rows should be ≤500 bundles, and the number of weaving yarn layers × number of rows should be ≤2000 bundles.

3. The three-dimensional weaving method for a multi-branched, crown- and flange-type prefabricated structure according to claim 2, characterized in that, When weaving a spherical crown, the method for determining the yarn weaving angle is as follows: The load borne by the joint is divided into a load P1 parallel to the flange surface and a load P2 perpendicular to the flange surface. When P1≥P2, the braiding angle range is 50°~60°. When P1<P2, the braiding angle range is 30°~40°. The joint is a joint prepared using a prefabricated body.

4. The three-dimensional weaving method for a multi-branched, crown- and flange-type prefabricated structure according to claim 3, characterized in that, The number of weaving nodes h is determined according to the following formula based on the number of weaving rows m and the weaving angle θ: S = h × tanθ × m; Where S represents the perimeter of the braided cross section.

5. The three-dimensional weaving method for a multi-branched, crown- and flange-type prefabricated structure according to claim 1, characterized in that, When braiding flanges, the number of braided rows should be ≤500 bundles, and the number of braided yarn layers × number of rows should be ≤2000 bundles; When braiding the flange, the yarn braiding angle is 30°~50°.

6. The three-dimensional weaving method for a multi-branched, crown- and flange-type prefabricated structure according to claim 1, characterized in that, When weaving branch structures, the yarn weaving angle is 30°~40°.

7. A multi-branched precast structure with a spherical crown and flange, characterized in that, It is obtained by the three-dimensional weaving method described in any one of claims 1-6.

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