Three-dimensional braiding forming method for preform of marine propeller blade

Abstract

A three-dimensional braiding forming method for a preform of a marine propeller blade (1). Firstly, by means of three-dimensional software, a three-dimensional model of an original blade (1) having the features of bending, twisting, a variable cross-section, and a variable thickness is converted to a model in a planar form; and on this basis, a thick area of the root of the blade (1) in the planar form is used as a starting braiding cross-section, and braiding is performed according to a four-step three-dimensional multidirectional braiding process. The three-dimensional braiding forming method can realize near-net-size integral forming of a large-size propeller blade (1) having complex features of bending, twisting, a variable cross-section, and a variable thickness, etc., such that the problem that a conventional laminated composite blade (1) has poor inter-layer bonding strength and is severely damaged in secondary processing is effectively solved, thereby ensuring the stability of the overall mechanical properties of the blade (1).

Description

Three-dimensional weaving forming method for marine propeller blade preform Technical Field

[0001] The invention belongs to the technical field of composite material preform forming methods, and in particular relates to a three-dimensional weaving forming method of a marine propeller blade preform. Background Art

[0002] The propeller is a key component of a ship's propulsion system, converting the main engine's power into thrust to propel the vessel forward. As ship tonnage increases and main engine speed decreases, the size of the pump-jet propeller will increase further in the future, significantly increasing its overall weight. Propellers made of traditional metal materials suffer from poor damping performance, high underwater radiation noise, heavy weight, and poor corrosion resistance. Composite materials have high specific strength and stiffness, and offer advantages such as reduced corrosion and cavitation damage, improved fatigue properties, superior material damping properties, and reduced lifecycle costs. Composite propellers have become a research hotspot in recent years.

[0003] Currently, marine propeller blade composite materials are typically prepared by pre-weaving, laying, and hot molding to form a preform, which is then impregnated with resin and cured. The method of forming a preform by three-dimensional integral weaving overcomes the inherent shortcomings of traditional laminated composite materials, such as poor interlayer performance and easy delamination after stress. Examples include the methods disclosed in Chinese patents CN113415003B, published on September 21, 2021, and CN113119492B, published on July 16, 2021. However, for blades with complex curved structures with large torsional cross-sections, the variable thickness torsional form is difficult to directly weave.

[0004] Summary of the Invention

[0005] The purpose of the present disclosure is to provide a three-dimensional weaving forming method for a marine propeller blade preform, which can realize the three-dimensional weaving forming of blades with variable thickness, bending and twisting shapes.

[0006] The technical solution adopted in the present disclosure is a three-dimensional weaving molding method for a marine propeller blade preform, which is specifically implemented according to the following steps: Step 1, converting the three-dimensional model of the blade into a planar model; Step 2, weaving the planar blade converted in Step 1.

[0007] In some embodiments, step 1 is specifically as follows: step 1.1, splitting the original three-dimensional model of the propeller blade into two parts, the blade surface and the blade back, along the mid-surface; step 1.2, respectively performing layered design on the blade surface and blade back three-dimensional models to form a multi-layer blade; step 1.3, flattening and designing each layer of blade obtained in step 1.2, and then reconstructing it to form a planar blade surface and a planar blade back; step 1.4, partitioning the planar blade surface and the planar blade back along the width direction of the blade, merging areas with similar widths to form the thickest area in the middle, thicker areas on both sides, and thinner areas at the boundary; step 1.5, segmenting the planar blade surface and the planar blade back along the length direction of the blade according to angle changes, merging areas with similar angles, and determining the reference section of the blade bending.

[0008] In some embodiments, the layered design method in step 1.2 is specifically as follows: the three-dimensional models of the leaf surface and the leaf back are layered with a thickness of 1.0 mm to 1.5 mm from the outside to the inside along the thickness direction of the leaf.

[0009] In some embodiments, step 2 is specifically as follows: step 2.1, designing a three-dimensional preform weaving structure of the blade according to the performance requirements of the propeller blade 1; step 2.2, designing the weaving process of each equal thickness layer and different segments of the blade according to the planar blade surface and planar blade back cross-sectional dimensions obtained in step 1.3; step 2.3, arranging the yarn; step 2.4, starting weaving from the root of the planar blade, and weaving using a 1×1 four-step three-dimensional weaving process; step 2.5, during the weaving process, the left and right boundaries of the cross-section widening area need to perform at least one whole-row yarn adding operation; the left and right boundaries of the cross-section narrowing area need to perform at least one whole-row yarn reducing operation; the inside of the cross-section thinning area needs to perform at least one whole-row yarn reducing operation; multiple connection operations are required between different equal thickness layers; the blade bending area needs to perform at least one lifting operation; step 2.6, repeating steps 2.4 and 2.5, accompanied by tightening movements, to obtain a complete propeller blade three-dimensional preform.

[0010] In some embodiments, the weaving process in step 2.2 includes the number of yarns required for each equal thickness layer, the yarn arrangement method, the flower node height, the number of cycles, the number of yarn columns increased when the blade becomes wider, the number of yarn columns reduced when the blade becomes narrower, the number of rows and columns reduced when the blade becomes thinner, and the position of the connection point columns between each equal thickness layer.

[0011] In some embodiments, the yarn arrangement method in step 2.3 is specifically as follows: the three-dimensional braiding machine is placed symmetrically in a straight-line stepped manner, with the blade surface and back being divided into two parts, the flat root of the blade is selected as the starting braiding section, and the yarn is arranged and hung according to the cross-sectional shape of the blade, specifically: one end of the yarn is fixed to the yarn hanging device above the three-dimensional braiding machine, and the other end is hung on the chassis of the three-dimensional braiding machine through a tension line; the yarn includes braiding yarn, axial yarn, and circumferential yarn, and the braiding yarn is divided into main yarn and side yarn. The main yarn is arranged in rows and columns and hung on the corresponding yarn carrier of the three-dimensional braiding machine chassis, and the side yarn is arranged at intervals around the main yarn to ensure that the number of yarns in each row and column is the same, the axial yarn is arranged on both sides of the main yarn column, and the columns where the braiding yarn or axial yarn is located are counted as one column.

[0012] In some embodiments, the method of adding yarn when the blade cross-section becomes wider in step 2.5 is: adding yarn a on the left and right sides of the blade, arranging the reserved yarn hung above the knitting machine in advance on the yarn carriers of the knitting machine chassis corresponding to the left and right sides of the blade, and continuing weaving after adding the corresponding columns of yarn; wherein, the yarn adding unit includes at least one adjacent knitting yarn and axial yarn in the same row and column, that is, two columns of yarn, and the four-step yarn arrangement rules cannot be changed during the yarn adding process.

[0013] In some embodiments, the method of reducing yarn when the blade cross-section becomes narrow in step 2.5 is: reducing yarn b on the left and right sides of the blade, removing the yarn on the yarn carrier of the knitting machine chassis corresponding to the left and right sides of the blade from the yarn carrier to reduce the corresponding columns of yarn, and continuing to weave for 2 cycles and then cutting the yarn from the narrowed cross-section of the blade; wherein, the yarn reduction unit includes at least one adjacent knitting yarn and axial yarn in the same row and column, that is, two columns of yarn, and the four-step yarn arrangement rule cannot be changed during the yarn reduction process.

[0014] In some embodiments, the yarn reduction method when the blade becomes thinner in step 2.5 is: reducing yarn c in the direction of blade thickness, separating the innermost yarns on the blade surface and back of the blade from the yarn carrier, reducing the corresponding row of yarns, and locking the row of yarns by adjusting the row direction track of the knitting machine so that they no longer participate in the knitting movement. After continuing to knit for 2 cycles, the separated corresponding row of yarns is removed from the yarn carrier, and the yarn is cut at the thinned section of the blade; wherein, the yarn reduction unit includes all the knitting yarns and axial yarns of at least one row, and the four-step yarn arrangement rules cannot be changed during the yarn reduction process.

[0015] In some embodiments, the method for bending the blade in step 2.5 is: when weaving to the blade bending reference section, use tooling to lift the fabric to a certain angle and then continue weaving, wherein there must be a weaving triangle area before each bending reference section, and the triangle area must be realized by controlling the three-dimensional weaving machine, that is, different areas in the width direction of the blade are weaved asynchronously, and synchronous weaving begins after weaving to the blade bending reference section.

[0016] The beneficial effects of the present disclosure are: (1) the three-dimensional weaving molding method of the present disclosure can realize the near-net-size integral molding of large-sized propeller blades with complex features such as bending, twisting, variable cross-section, and variable thickness, effectively solving the problems of poor interlayer bonding strength and severe secondary processing damage in conventional laminated composite blades, and ensuring the stability of the overall mechanical properties of the blades; (2) the three-dimensional weaving molding method of the present disclosure uses high-performance fibers to continuously weave to form a near-net-size preform, which can greatly reduce the weight of the blades, significantly reduce propeller vibration noise and maintenance costs, and improve the stealth performance and economy of the ship. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG1 is a schematic structural diagram of a marine propeller blade according to Example 1 of the present disclosure;

[0018] FIG2 is a schematic diagram of a propeller blade being split from its mid-plane into a blade face and a blade back in the method disclosed herein;

[0019] FIG3 is a schematic diagram of the structure of the planar leaf surface and the back of the leaf in the method disclosed herein, wherein FIGa is a schematic diagram of the planar leaf surface structure, and FIGb is a schematic diagram of the planar leaf back structure;

[0020] FIG4 is a schematic diagram of the partition design of the planar leaf surface and the leaf back along the width direction in the method disclosed in the present invention, wherein FIGa is the planar leaf surface, and FIGb is the planar leaf back;

[0021] FIG5 is a schematic diagram of the segmented design of a planar blade along the length direction in the method disclosed herein;

[0022] FIG6 is a schematic diagram of the placement of a three-dimensional braiding machine in the method disclosed herein;

[0023] FIG7 is a schematic diagram of a yarn arrangement method in the disclosed method;

[0024] FIG8 is a schematic diagram of a method of increasing or decreasing yarn in the disclosed method;

[0025] FIG9 is a schematic diagram of a yarn reduction method in the disclosed method;

[0026] FIG10 is a schematic diagram of the structure of a marine propeller blade according to Embodiment 2 of the present disclosure.

[0027] In the figure, 1. blade, 2. leaf surface, 3. leaf back, 4. leaf surface in planar shape, 5. leaf back in planar shape, 6. thickest area in the middle, 7. thicker areas on both sides, 8. thinner areas at the boundary, 9. first bending reference section, 10. second bending reference section, 11. third bending reference section, 12. axial yarn, 13. main yarn, 14. side yarn, 15. yarn a, 16. yarn b, 17. yarn c. DETAILED DESCRIPTION

[0028] The present disclosure will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] The present invention discloses a three-dimensional weaving method for a marine propeller blade preform. First, using three-dimensional software, an original three-dimensional blade model, characterized by bending, twisting, variable cross-section, and variable thickness, is converted into a two-dimensional model. Based on this, the blade's thick root region is used as the starting weaving section, and weaving is performed according to a four-step three-dimensional multi-directional weaving process. Blade thickness refers to the normal thickness of the blade. Blade thick refers to the width of the blade. The thickest region is at the blade root, while the widest region is not at the root. The starting weaving section is the blade root. During the weaving process, at least one full-row yarn addition operation is performed at the left and right boundaries of the widening region. At least one full-row yarn reduction operation is performed at the left and right boundaries of the narrowing region. At least one full-row yarn reduction operation is performed inside the thinning region. Multiple connections are performed between layers of varying thickness. The curved region of the blade is subjected to at least one lifting operation using a tool. After these continuous weaving operations, a nearly net-shape three-dimensional propeller blade preform is formed. After being removed from the fabric frame, the trimmed edges are finely trimmed, and then placed in a mold for pre-pressing and shaping to form the final propeller blade. Please follow the steps below to implement it:

[0030] Step 1: Convert the three-dimensional model of the blade 1 into a plane model, as shown in Figures 1 to 5.

[0031] Step 1.1: As shown in Figures 1 and 2, the original three-dimensional model of the propeller blade 1 is split into two parts: the blade surface 2 and the blade back 3 along the mid-surface.

[0032] Step 1.2: The three-dimensional models of the leaf surface 2 and the leaf back 3 are layered with a thickness of 1.0 mm to 1.5 mm from the outside to the inside along the thickness direction of the leaf to form a multi-layer leaf.

[0033] Step 1.3, as shown in FIG3, each layer of blades obtained in step 1.2 is flattened and reconstructed to form a flat blade surface 4 and a flat blade back 5.

[0034] Here, each layer of blades obtained in step 1.2 may be curved. After being flattened, the position close to the root of the blade does not change significantly, and the blades can be aligned and stacked according to the determined reference line.

[0035] Step 1.4, as shown in FIG4 , the planar leaf surface 4 and the planar leaf back 5 are partitioned along the width direction of the leaf, and regions of similar width are merged to form the thickest region 6 in the middle, thicker regions 7 on both sides, and thinner regions 8 at the border.

[0036] Here you can set the area with a width difference within a set value as a close width area. The setting value can be 1.5mm, 1.2mm, 1mm, etc.

[0037] Step 1.5: As shown in Figure 5, the planar blade surface 4 and the planar blade back 5 are segmented along the blade length according to the angle variation. Regions with similar angles are merged to determine the reference cross-sections for blade bending. As shown in Figure 5, three reference cross-sections are obtained: the first bending reference cross-section 9, the second bending reference cross-section 10, and the third bending reference cross-section 11.

[0038] In a specific application, it is possible to preferentially merge areas with similar widths of the blade surface 4 and the blade back 5, and then merge areas with similar angles. Starting from the blade root, areas with different angles can also be divided into one segment, and areas with similar angles can be divided into one segment.

[0039] Step 2: Weave the planar blades transformed in step 1, as shown in Figures 6 to 9.

[0040] Step 2.1: Design the three-dimensional braided structure of the propeller blade 1 based on its performance requirements. Design a three-dimensional five-dimensional structure (including braided yarn and axial yarn) along the entire length of the blade with excellent axial performance. Simultaneously, add a sixth circumferential structural yarn along the width of the blade to improve the blade's deformation resistance due to bending and torsion.

[0041] Step 2.2. Based on the cross-sectional dimensions of the planar leaf surface 4 and the planar leaf back 5 obtained in step 1.3, i.e., the length, width, and thickness of the leaf, design the weaving process for each equal-thickness layer and different segments of the leaf, including the number of yarns required for each equal-thickness layer, the yarn arrangement method, the height of the flower nodes, the number of cycles, the number of yarn columns increased when the leaf becomes wider, the number of yarn columns decreased when the leaf becomes narrower, the number of rows and columns decreased when the leaf becomes thinner, and the position of the connection points between each equal-thickness layer.

[0042] Step 2.3, Arrange the yarn. As shown in Figure 6, place the three-dimensional braiding machine in a straight-line stepped manner, symmetrically divided into two parts: the front and back of the blade. Select the flat root of the blade as the starting braiding section. Arrange and hang the yarn according to the cross-sectional shape of the blade. Specifically, fix one end of the yarn to the yarn hanging device above the three-dimensional braiding machine, and hang the other end on the chassis of the three-dimensional braiding machine through a tension line. As shown in Figure 7, the yarn includes braiding yarn, axial yarn 12, and hoop yarn. The braiding yarn is divided into main yarn 13 and side yarn 14. The main yarn 13 is arranged in rows and columns and hung on the corresponding yarn carrier of the three-dimensional braiding machine chassis. The side yarn 14 is arranged at intervals around the main yarn to ensure that the number of yarns in each row and column is the same. The axial yarn 12 is arranged on both sides of the main yarn column. The columns where the braiding yarn or the axial yarn 12 is located are all counted as one column.

[0043] Step 2.4: Start weaving from the flat blade root using a 1×1 four-step three-dimensional weaving process. The specific steps are:

[0044] Step 2.4.1: The knitting yarn carriers in adjacent rows together with the axial yarn carriers of the row are alternately moved horizontally to the left or to the right along the row track by one knitting yarn carrier position.

[0045] Step 2.4.2, the braiding yarn carriers in adjacent columns move vertically upward or downward along the column track direction alternately by one braiding yarn carrier position, and at the same time, the axial yarns 12 in adjacent rows in different equal thickness layers exchange the yarn hanging positions for connection.

[0046] Step 2.4.3, in the opposite direction of movement to step 2.4.1, the knitting yarn carriers in the adjacent rows together with the axial yarn carriers and connecting yarn carriers of the row move horizontally to the left or right along the row track by one knitting yarn carrier position.

[0047] Step 2.4.4, in contrast to the movement direction of step 2.4.2, the weaving yarn carriers in adjacent columns move vertically upward or downward alternately along the column track direction by one weaving yarn carrier position. At the same time, the axial yarns 12 in adjacent rows in different equal thickness layers exchange the hanging yarn positions for connection; at this point, the yarn carriers are restored to their initial positions, completing a movement cycle.

[0048] Follow steps 2.4.1 to 2.4.4 and repeat the motion cycle until the designed number of cycles is completed.

[0049] Step 2.5: When encountering variable cross-section during the weaving process, weave according to the corresponding weaving method.

[0050] (1) Method of increasing yarn when the blade becomes wider:

[0051] As shown in Figure 8, when the blade cross-section widens during weaving, yarn a15 is added to the left and right sides of the blade to meet the widening requirement. The reserved yarns, pre-hung above the braiding machine, are arranged on the yarn carriers on the corresponding braiding machine chassis on the left and right sides of the blade according to the yarn arrangement rules in step 2.3. After adding the corresponding columns of yarn, weaving continues. The yarn-increasing unit includes at least one adjacent braiding yarn and axial yarn in the same row and column, i.e., two columns of yarn. The four-step yarn arrangement rules cannot be changed during the yarn-increasing process.

[0052] (2) Yarn reduction method when the blade becomes narrower:

[0053] As shown in Figure 8, when the blade cross-section narrows during weaving, yarn b16 needs to be reduced on the left and right sides of the blade to meet the narrowing requirement. The yarns on the yarn carriers on the knitting machine chassis corresponding to the left and right sides of the blade are removed from the yarn carriers according to the yarn arrangement rules in step 2.3. After weaving for two more cycles, the yarn is cut at the narrowing section of the blade. The yarn reduction unit includes at least one adjacent knitting yarn and an axial yarn in the same row and column, i.e., two columns of yarn. The four-step yarn arrangement rules cannot be changed during the yarn reduction process.

[0054] (3) Yarn reduction method when the blade becomes thinner:

[0055] As shown in Figure 9, when the blade cross-section becomes thinner during weaving, it is necessary to meet the need for thickening the cross-section by reducing yarn c 17 in the direction of the blade thickness. The innermost yarns on the blade surface and back of the blade are separated from the yarn carrier according to the yarn arrangement rules of step 2.3, reducing the corresponding row of yarns. The row of yarns is locked by adjusting the row direction track of the braiding machine so that it no longer participates in the weaving movement. After weaving for two more cycles, the separated row of yarns is removed from the yarn carrier and the yarn is cut at the thinning section of the blade. The yarn reduction unit includes all the braiding yarns and the axial yarn of at least one row. The four-step yarn arrangement rules cannot be changed during the yarn reduction process.

[0056] (4) Method of adding the sixth structural yarn in the circumferential direction in the blade width direction:

[0057] To improve the blade's deformation resistance, circumferential yarns are introduced during the weaving process. Specifically, a fixed length of circumferential yarn is introduced between the odd-numbered rows in the first half of each cycle, and between the even-numbered rows in the second half of each cycle. The length of the circumferential yarn is 5mm larger than the blade width.

[0058] (5) Connection method between equal thickness layers:

[0059] Each time a cycle is knitted, the yarn hanging positions of the axial yarns 12 in adjacent rows are exchanged according to the corresponding column positions of the blades between the layers of different thicknesses, and the knitting is continued to realize the layer connection.

[0060] (6) Methods of bending blades:

[0061] As shown in Figure 5, when weaving to the blade bending reference sections 9, 10, and 11, the fabric is lifted to a certain angle using a tool before weaving continues. A weaving triangle is required before each bending reference section. This triangle is achieved by controlling the 3D weaving machine, that is, weaving in different areas along the blade width direction is asynchronous, and synchronous weaving begins after weaving to the blade bending reference section.

[0062] Step 2.6: Repeat steps 2.4 and 2.5, accompanied by tightening movements, to obtain a complete three-dimensional preform of the propeller blade.

[0063] Example 1

[0064] A three-dimensional preform of a single-blade marine propeller is processed using the three-dimensional weaving molding method of the propeller blade preform disclosed in the present invention. The blade structure is shown in FIG1 , and the maximum dimensions are 1402 mm long, 1140 mm wide, and 127 mm thick. The original three-dimensional model of the blade is shown in FIG1 . First, it is split along the middle surface into two parts, the blade surface 2 and the blade back 3, as shown in FIG2 . Then, the three-dimensional model of the blade surface 2 is layered from the outside to the inside with a thickness of 1.0 mm to 1.5 mm, forming 34 layers of 1.5 mm layered blades and 13 layers of 1 mm layered blades. Each layer of the blade is flattened and reconstructed to form a flat blade surface 4. Then, the blade is partitioned and designed along the width direction of the blade, and areas with similar widths are merged to form the thickest area 6 in the middle, thicker areas 7 on both sides, and thinner areas 8 at the border. The blade is also segmented and designed along the length direction of the blade according to angle changes, and areas with similar angles are merged. The reference sections 9, 10 and 11 of the blade bending are determined; similarly, the three-dimensional model of the blade back is layered from the outside to the inside along the blade thickness direction with a thickness of 1.0mm to 1.5mm, forming 36 layers of 1.5mm layered blades and 10 layers of 1mm layered blades. Each layer of the blade is flattened and reconstructed to form a flat blade back 5. Then, the blade is divided into sections along the width direction, and areas with similar widths are merged to form the thickest area 6 in the middle, thicker areas 7 on both sides, and thinner areas 8 at the border. The blade is also divided into sections along the length direction according to the angle change, and areas with similar angles are merged to determine the reference sections 9, 10 and 11 of the blade bending.

[0065] The blade length direction is used as the weaving direction, and the yarn is arranged according to Figure 7. The total number of yarns in the thickest area 6 in the middle is 52978, and the yarns are arranged in 91 rows and 581 columns in the main array; the total number of yarns in the thicker area 7 on both sides is 2185, and the yarns are arranged in 47 rows and 53 columns in the main array; the total number of yarns in the thinner area 8 is 986, and the yarns are arranged in 14 rows and 69 columns in the main array; the flower node height is designed to be 8mm, with a total of 180 cycles; the thickest area 6 in the middle starts from the 80th cycle, and 2 to 8 columns of yarn are reduced on both sides of each cycle. The thicker area 7 on both sides starts from the 25th cycle, and 2 to 8 columns of yarn are added on both sides of each cycle. The thinner border area Starting from the 25th loop, region 8 of the weft increases by 2 to 12 rows on both sides of the weft with each loop. Starting from the 11th loop, the thickness direction decreases by one row on the innermost side every 2 to 4 loops. The three-dimensional preform is knitted using a four-step method, with the corresponding columns of axial yarns between layers swapping their positions once per loop, while the remaining yarns return to their initial positions. During loops 33, 96, and 156, the weaving machines weave asynchronously until loops 76, 126, and 171, using a tool to lift the fabric once before continuing. After 180 machine cycles accompanied by a tightening motion, the three-dimensional preform for the single-blade marine propeller is completed. After removal, the preform is trimmed and placed in a mold for final shaping to achieve the desired blade.

[0066] Example 2

[0067] Another single-blade three-dimensional preform for a marine propeller is processed by the three-dimensional weaving molding method of the propeller blade preform disclosed in the present invention. The original three-dimensional model of the blade is shown in FIG10 , and the maximum dimensions are 1182 mm long, 282 mm wide, and 66 mm thick. First, it is split along the middle surface into two parts, the blade surface 2 and the blade back 3, as shown in FIG2 ; then the three-dimensional model of the blade surface 2 is layered and designed from the outside to the inside with a thickness of 1.0 mm to 1.5 mm, forming 17 layers of 1.5 mm layered blades and 7 layers of 1 mm layered blades. Each layer of the blade is flattened and reconstructed to form a flat blade surface 4. Then, the blade is partitioned and designed along the width direction of the blade, and areas with similar widths are merged to form the thickest area 6 in the middle, thicker areas 7 on both sides, and thinner areas 8 at the border. The blade is also segmented and designed according to angle changes along the length direction of the blade, and areas with similar angles are merged to determine the bending of the blade. Similarly, the three-dimensional model of the blade back is layered from the outside to the inside along the thickness direction of the blade with a thickness of 1.0mm to 1.5mm, forming 18 layers of 1.5mm layered blades and 6 layers of 1mm layered blades. Each layer of the blade is flattened and reconstructed to form a flat blade back 5. Then, the blade is partitioned along the width direction of the blade, and areas with similar widths are merged to form the thickest area 6 in the middle, thicker areas 7 on both sides, and thinner areas 8 at the border. The blade is also segmented along the length direction according to the angle change, and areas with similar angles are merged to determine the reference sections 9, 10, and 11 of the blade bending.

[0068] The length of the blade is used as the weaving direction, and the yarn is arranged according to Figure 7. The total number of yarns in the thickest area 6 in the middle is 13585, and the yarns are arranged in 47 rows and 287 columns in the main array; the total number of yarns in the thicker area 7 on both sides is 516, and the yarns are arranged in 21 rows and 25 columns in the main array; the total number of yarns in the thinner area 8 is 289, and the yarns are arranged in 8 rows and 35 columns in the main array; the flower node height is designed to be 8mm, with a total of 150 cycles; the thickest area 6 in the middle starts from the 36th cycle, and 2 to 6 columns of yarn are reduced on both sides of each cycle. The thicker area 7 on both sides starts from the 12th cycle, and 2 to 6 columns of yarn are added on both sides of each cycle. Region 8 starts from the 12th cycle, and 2 to 8 columns of yarn are added on both sides of each cycle; in the thickness direction, one row of yarn is reduced on the innermost side every 2 to 4 cycles starting from the 5th cycle; the three-dimensional preform is knitted according to the four-step method, and the corresponding column positions of the axial yarns between each layer are exchanged once in each cycle, and the other yarns return to their initial positions; when knitting to the 19th, 49th, 86th, and 149th cycles, each knitting machine needs to knit asynchronously to the 36th, 73rd, and 157th cycles, use a tool to lift the fabric once, and then continue knitting; after 157 machine cycles accompanied by tightening movements, the three-dimensional preform of the single-blade marine propeller is obtained.

[0069] Example 3

[0070] A third type of marine propeller single-blade three-dimensional preform is processed by the three-dimensional weaving molding method of the propeller blade preform disclosed in the present invention. The maximum size of the blade is 1260 mm in length, 168 mm in width, and 34 mm in thickness. The three-dimensional model of the blade surface 2 is layered and designed with a thickness of 1.0 mm to 1.5 mm from the outside to the inside along the thickness direction of the blade, forming 6 layers of 1.5 mm layered blades and 8 layers of 1 mm layered blades. Each layer of blades is flattened and reconstructed to form a planar blade surface 4, and then partition and segment designs are performed. Similarly, the three-dimensional model of the blade back 3 is layered and designed with a thickness of 1.0 mm to 1.5 mm from the outside to the inside along the thickness direction of the blade, forming 8 layers of 1.5 mm layered blades and 5 layers of 1 mm layered blades. Each layer of blades is flattened and reconstructed to form a planar blade back 5, and then partition and segment designs are performed.

[0071] The length of the blade is used as the weaving direction, and the yarns are arranged according to Figure 7. The total number of yarns in the thickest area 6 in the middle is 2914, and the yarns are arranged in 24 rows and 117 columns in the main array; the total number of yarns in the thicker area 7 on both sides is 451, and the yarns are arranged in 16 rows and 27 columns in the main array; the total number of yarns in the thinner area 8 on the border is 360, and the yarns are arranged in 7 rows and 43 columns in the main array; the flower node height is designed to be 8mm, with a total of 165 cycles; the thickest area 6 in the middle starts from the 15th cycle, and 2 to 6 columns of yarn are reduced on both sides of each cycle. The thicker area 7 on both sides starts from the 6th cycle, and 2 to 6 columns of yarn are added on both sides of each cycle. Starting from the sixth cycle, the thinner region 8 adds 2 to 8 rows of yarn on both sides with each cycle. Starting from the eighth cycle, the innermost row of yarn is reduced by one row every two to four cycles. The three-dimensional preform is knitted using a four-step method. Each cycle, the corresponding rows of axial yarns between layers are swapped, and the remaining yarns return to their initial positions. At the 24th and 85th cycles, the knitting machines knit asynchronously until the 50th and 124th cycles, using a tool to lift the fabric once before continuing. After 165 machine cycles accompanied by a tightening motion, the three-dimensional preform for the single-blade marine propeller is obtained. After removal, the preform is trimmed and placed in a mold for final shaping to achieve the desired blade.

Claims

1. A three-dimensional weaving forming method for a preform of a marine propeller blade, wherein: Follow the steps below to implement it: Step 1, converting the three-dimensional model of the blade (1) into a two-dimensional model; Step 2: Weave the planar leaves transformed in step 1.

2. The three-dimensional weaving forming method of a marine propeller blade preform according to claim 1, wherein: Step 1 is as follows: Step 1.1, splitting the original three-dimensional model of the propeller blade (1) into two parts, a blade surface (2) and a blade back (3), along the mid-surface; Step 1.2, designing the three-dimensional models of the leaf surface (2) and the leaf back (3) in layers respectively to form a multi-layered leaf; Step 1.3, flattening and designing each layer of leaves obtained in step 1.2, and then reconstructing to form a flat leaf surface (4) and a flat leaf back (5); Step 1.4, partitioning the planar leaf surface (4) and the planar leaf back (5) along the width direction of the leaf, merging areas with similar widths to form the thickest area in the middle (6), thicker areas on both sides (7), and thinner areas at the border (8); Step 1.5, the planar blade surface (4) and the planar blade back (5) are segmentally designed along the length direction of the blade according to the angle change, and the areas with similar angles are merged to determine the reference cross section of the blade bending.

3. The three-dimensional weaving forming method of a marine propeller blade preform according to claim 2, wherein: The specific method of layered design in step 1.2 is: the three-dimensional models of the leaf surface (2) and the leaf back (3) are layered and designed from the outside to the inside along the thickness direction of the leaf with a thickness of 1.0 mm to 1.5 mm.

4. The three-dimensional weaving forming method of a marine propeller blade preform according to claim 2, wherein: Step 2 is as follows: Step 2.1, designing a blade three-dimensional preform braided structure according to the performance requirements of the propeller blade 1; Step 2.2, according to the cross-sectional dimensions of the planar blade surface (4) and the planar blade back (5) obtained in step 1.3, design the weaving process of the blade with equal thickness layers and different sections; Step 2.3, arrange the yarn; Step 2.4, weaving starts from the root of the flat blade, and adopts a 1×1 four-step three-dimensional weaving process for weaving; Step 2.5, during the weaving process, the left and right borders of the cross-section widening area need to perform at least one whole-row yarn adding operation; the left and right borders of the cross-section narrowing area need to perform at least one whole-row yarn reducing operation; the inner side of the cross-section thinning area needs to perform at least one whole-row yarn reducing operation; multiple connection operations are required between layers of different thickness; and the blade bending area needs to perform at least one lifting operation; Step 2.6: Repeat steps 2.4 and 2.5, accompanied by tightening movements, to obtain a complete three-dimensional preform of the propeller blade.

5. The three-dimensional weaving forming method of a preform for a marine propeller blade according to claim 4, wherein: The weaving process in step 2.2 includes the number of yarns required for each equal thickness layer, the yarn arrangement method, the flower node height, the number of cycles, the number of yarn columns increased when the blade becomes wider, the number of yarn columns decreased when the blade becomes narrower, the number of rows and columns decreased when the blade becomes thinner, and the position of the connection point columns between each equal thickness layer.

6. The three-dimensional weaving forming method of a preform for a marine propeller blade according to claim 4, wherein: The specific method of yarn arrangement in step 2.3 is: The three-dimensional braiding machine is placed symmetrically in a linear step-like manner, with the blade surface and the blade back being divided into two parts. The flat blade root is selected as the starting braiding section, and the yarn is arranged and hung according to the cross-sectional shape of the blade. Specifically, one end of the yarn is fixed on the yarn hanging device above the three-dimensional braiding machine, and the other end is hung on the chassis of the three-dimensional braiding machine through a tension line. The yarn includes braiding yarn, axial yarn (12), and circumferential yarn. The braiding yarn is further divided into main yarn (13) and side yarn (14). The main yarn (13) is hung on the corresponding yarn carrier of the chassis of the three-dimensional braiding machine in rows and columns. The side yarn (14) is arranged at intervals around the main yarn to ensure that the number of yarns in each row and each column is the same. The axial yarn (12) is arranged on both sides of the main yarn column. The columns where the braiding yarn or the axial yarn (12) is located are all counted as one column.

7. The three-dimensional weaving forming method of a marine propeller blade preform according to claim 4, wherein: The yarn increasing method when the blade cross section becomes wider in step 2.5 is: Yarn a (15) is added on the left and right sides of the blade, and the reserved yarn hung above the knitting machine in advance is arranged on the yarn carrier of the knitting machine chassis corresponding to the left and right sides of the blade, and weaving is continued after the corresponding columns of yarn are added; wherein, the yarn adding unit includes at least one adjacent knitting yarn and axial yarn in the same row and column, that is, two columns of yarn, and the four-step yarn arrangement rule cannot be changed during the yarn adding process.

8. The three-dimensional weaving forming method of a marine propeller blade preform according to claim 4, wherein: The yarn reduction method when the blade cross section becomes narrower in step 2.5 is: The yarn b (16) is reduced on the left and right sides of the blade, and the yarn on the yarn carrier of the knitting machine chassis corresponding to the left and right sides of the blade is removed from the yarn carrier to reduce the corresponding column of yarn, and the yarn is cut from the narrowed section of the blade after knitting for 2 cycles; wherein the yarn reduction unit includes at least one adjacent yarn in the same row and the same column. For weaving yarn and axial yarn, i.e. two columns of yarn, the four-step yarn arrangement rule cannot be changed during the yarn reduction process.

9. The three-dimensional weaving forming method of a preform of a marine propeller blade according to claim 4, wherein: The yarn reduction method when the blade becomes thinner in step 2.5 is: The yarn c (17) is reduced in the direction of the thickness of the blade, and the innermost yarns of the blade surface and the blade back are separated from the yarn carrier, thereby reducing the corresponding row of yarns, and locking the row of yarns by adjusting the row direction track of the knitting machine so that the yarns no longer participate in the knitting movement. After continuing to knit for 2 cycles, the separated corresponding row of yarns is removed from the yarn carrier, and the yarns are cut at the thinned section of the blade; wherein the yarn reduction unit includes all the knitting yarns and axial yarns of at least one row, and the four-step yarn arrangement rule cannot be changed during the yarn reduction process.

10. The three-dimensional weaving forming method of a preform of a marine propeller blade according to claim 4, wherein: The method for bending the blade in step 2.5 is: When weaving to the blade bending reference section, use tooling to lift the fabric to a certain angle and then continue weaving. There must be a weaving triangle area before each bending reference section. This triangle area needs to be realized by controlling the three-dimensional weaving machine, that is, different areas in the blade width direction are weaved asynchronously, and synchronous weaving begins after weaving to the blade bending reference section.

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