Three-dimensional braiding method for marine propeller blade preforms

Abstract

The application discloses a three-dimensional weaving forming method of a marine propeller blade preform, which comprises the following steps: firstly, converting an original blade three-dimensional model with bending, twisting, variable cross-section and variable thickness characteristics into a planar model by means of three-dimensional software; and secondly, taking a thick area of a blade root in a planar form as a starting weaving section, and weaving according to a four-step three-dimensional multi-directional weaving process. The three-dimensional weaving forming method can realize near-net-size integral forming of a large-size propeller blade with complex characteristics such as bending, twisting, variable cross-section and variable thickness, effectively solves the problems of poor interlaminar bonding strength of conventional laminated composite blades and serious secondary processing damage, and guarantees the stability of the overall mechanical properties of the blade.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite material preform forming methods, and particularly relates to a three-dimensional braiding forming method for a marine propeller blade preform. BACKGROUND

[0002] The propeller is one of the key components of the ship power system, and its function is to convert the power of the main engine into thrust to push the ship forward. With the increase of ship tonnage and the decrease of main engine speed, the future pump-jet main dimension will be further increased, and the overall weight will also be significantly increased. The traditional metal material used to manufacture the propeller has the problems of poor damping performance, large underwater radiation noise, large weight, poor corrosion resistance and the like. Composite materials have high specific strength and specific stiffness, have the advantages of reducing corrosion and cavitation damage, improving fatigue characteristics, good material damping characteristics and reducing life cycle cost, and in recent years, composite propellers have become a research hotspot.

[0003] At present, the composite material of the marine propeller blade is usually formed by pre-braiding, laying and hot molding to form a preform, and then the preform is subjected to resin impregnation and curing treatment. Among them, the method of three-dimensional integral braiding forming preform overcomes the inherent defects of traditional laminated composite materials, such as poor interlaminar performance and easy delamination under stress, such as the methods disclosed in Chinese Patent CN113415003B with a publication date of September 21, 2021, and Chinese Patent CN113119492B with a publication date of July 16, 2021. However, for blades with complex curved surface structures of variable thickness and torsion, it is difficult to directly braze and form the variable thickness and torsion shape. SUMMARY

[0004] The purpose of the present application is to provide a three-dimensional braiding forming method for a marine propeller blade preform, which can realize three-dimensional braiding forming of the blade variable thickness, variable bending and torsion shape.

[0005] The technical solution adopted by the present application is a three-dimensional braiding forming method for a marine propeller blade preform, which is specifically implemented according to the following steps:

[0006] Step 1, converting the three-dimensional model of the blade into a planar model;

[0007] Step 2, braiding the planar blade converted in step 1.

[0008] The present application is characterized in that:

[0009] Step 1 is specifically:

[0010] Step 1.1, splitting the original three-dimensional model of the propeller blade along the middle surface into two parts of the blade surface and the blade back;

[0011] Step 1.2, the airfoil surface and the pressure surface three-dimensional model are respectively designed in layers to form multiple layers of airfoils;

[0012] Step 1.3, each layer of airfoils obtained in step 1.2 is designed to be flat, and then reconstructed to form a planar airfoil surface and a planar pressure surface;

[0013] Step 1.4, the planar airfoil surface and the planar pressure surface are designed in zones along the width direction of the airfoil, and the zones with close width are combined to form the thickest middle zone, the thicker side zones, and the thinner boundary zones;

[0014] Step 1.5, the planar airfoil surface and the planar pressure surface are designed in segments along the length direction of the airfoil according to the angle change, and the zones with close angle are combined to determine the reference section of the airfoil bending.

[0015] The layering design in step 1.2 is specifically as follows: the airfoil surface and the pressure surface three-dimensional model are respectively designed in layers along the thickness direction of the airfoil from outside to inside with a thickness of 1.0mm-1.5mm.

[0016] Step 2 is specifically as follows:

[0017] Step 2.1, designing the weaving structure of the airfoil three-dimensional preform according to the performance requirements of the propeller airfoil 1;

[0018] Step 2.2, designing the weaving process of each equal-thickness layer and different segments of the airfoil according to the section size of the planar airfoil surface and the planar pressure surface obtained in step 1.3;

[0019] Step 2.3, arranging the yarns;

[0020] Step 2.4, starting weaving from the planar airfoil root, and using 1×1 four-step three-dimensional weaving process to weave;

[0021] Step 2.5, in the weaving process, the left and right boundaries of the section with variable width need to be operated at least once for whole-column yarn adding, the left and right boundaries of the section with variable narrowness need to be operated at least once for whole-column yarn reducing, the inner side of the section with variable thinness need to be operated at least once for whole-row yarn reducing, multiple connection operations are needed between different equal-thickness layers, and at least one lifting operation is needed in the airfoil bending area;

[0022] Step 2.6, repeating step 2.4 and step 2.5, and accompanied by tightening movement, to obtain the complete propeller airfoil three-dimensional preform.

[0023] The weaving process in step 2.2 includes the number of yarns required by each equal-thickness layer, the yarn arrangement method, the stitch height, the cycle number, the number of added yarn columns when the airfoil is widened, the number of reduced yarn columns when the airfoil is narrowed, the number of reduced row columns when the airfoil is thinned, and the position of the connection point column between each equal-thickness layer.

[0024] The yarn arranging method in step 2.3 is specifically as follows:

[0025] The three-dimensional braiding machine is placed symmetrically according to the linear step type, and the blade root of the planar shape is selected as the initial braiding section. The yarns are 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 three-dimensional braiding machine base through a tension line system. The yarns include braiding yarns, shaft yarns and hoop yarns. The braiding yarns are further divided into main yarns and edge yarns. The main yarns are hung on the corresponding yarn carriers of the three-dimensional braiding machine base according to the row and column arrangement, and the edge yarns are arranged around the main yarns to ensure that the number of yarns in each row and each column is the same. The shaft yarns are arranged on both sides of the main yarn column, and the column where the braiding yarn or shaft yarn is located is counted as one column.

[0026] The yarn increasing method when the blade cross section is widened in step 2.5 is as follows:

[0027] Yarns a are added on both sides of the blade. The reserved yarns hung on the braiding machine above are arranged on the yarn carriers of the corresponding braiding machine base on both sides of the blade. After the corresponding column of yarns is increased, the braiding continues. The yarn increasing unit includes at least one adjacent braiding yarn and shaft yarn in the same row and column, i.e., two columns of yarns. The four-step yarn arranging rule cannot be changed during the yarn increasing process.

[0028] The yarn decreasing method when the blade cross section is narrowed in step 2.5 is as follows:

[0029] Yarns b are reduced on both sides of the blade. The yarns on the yarn carriers of the corresponding braiding machine base on both sides of the blade are removed from the yarn carriers to reduce the corresponding column of yarns. After 2 cycles of braiding, the yarns are cut at the narrowed cross section of the blade. The yarn decreasing unit includes at least one adjacent braiding yarn and shaft yarn in the same row and column, i.e., two columns of yarns. The four-step yarn arranging rule cannot be changed during the yarn decreasing process.

[0030] The yarn decreasing method when the blade is thinned in step 2.5 is as follows:

[0031] Yarns c are reduced in the thickness direction of the blade. The innermost yarns of the blade surface and the blade back are separated from the yarn carriers to reduce the corresponding row of yarns. The row of yarns is locked by adjusting the row direction track of the braiding machine so as not to participate in the braiding movement. After 2 cycles of braiding, the corresponding row of yarns separated from the yarn carriers is removed, and the yarns are cut at the thinned cross section of the blade. The yarn decreasing unit includes at least one row of all braiding yarns and shaft yarns. The four-step yarn arranging rule cannot be changed during the yarn decreasing process.

[0032] The method for bending the blade in step 2.5 is as follows:

[0033] When weaving to the bending reference section of the blade, the fabric is lifted by a tool at an angle and then continues to weave, wherein a weaving triangle area is required before each bending reference section, and the triangle area is realized by controlling the three-dimensional weaving machine, that is, different areas are woven out of synchronization in the width direction of the blade, and then the weaving is synchronized after the bending reference section of the blade is reached.

[0034] The beneficial effects of the present application are:

[0035] (1) The three-dimensional weaving forming method of the present application can realize near-net-size integral forming of large-size propeller blades with complex characteristics such as bending, twisting, variable cross-section and variable thickness, effectively solving the problems of poor interlayer bonding strength of conventional laminated composite blades and serious secondary processing damage, and ensuring the stability of the overall mechanical properties of the blade.

[0036] (2) The three-dimensional weaving forming method of the present application uses high-performance fibers to continuously weave to form a near-net-size preform, which can greatly reduce the weight of the blade, greatly reduce propeller vibration noise and maintenance cost, and improve the stealth performance and economy of the ship. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of a ship propeller blade structure of embodiment 1 of the present application;

[0038] Figure 2 is a schematic diagram of the propeller blade being split into a blade surface and a blade back from the middle surface in the method of the present application;

[0039] Figure 3 is a schematic diagram of the structure of the blade surface and the blade back in a planar form in the method of the present application, wherein Fig. a is a schematic diagram of the structure of the blade surface in a planar form, and Fig. b is a schematic diagram of the structure of the blade back in a planar form;

[0040] Figure 4 is a schematic diagram of the planar form blade surface and blade back being designed in the width direction in the method of the present application, wherein Fig. a is a planar form blade surface, and Fig. b is a planar form blade back;

[0041] Figure 5 is a schematic diagram of the planar form blade being designed in the length direction in the method of the present application;

[0042] Figure 6 is a schematic diagram of the placement mode of the three-dimensional weaving machine in the method of the present application;

[0043] Figure 7 is a schematic diagram of the yarn arrangement mode in the method of the present application;

[0044] Figure 8 is a schematic diagram of the column yarn increasing or decreasing mode in the method of the present application;

[0045] Figure 9is a schematic diagram of the yarn reducing mode in the method of the present application;

[0046] Figure 10 is a schematic diagram of the propeller blade structure of the second embodiment of the present application.

[0047] In the figure, 1. blade, 2. blade face, 3. blade back, 4. planar blade face, 5. planar blade back, 6. thickest middle region, 7. thicker two-side region, 8. boundary thin region, 9. first bending reference section, 10. second bending reference section, 11. third bending reference section, 12. shaft yarn, 13. main body yarn, 14. edge yarn, 15. yarn a, 16. yarn b, 17. yarn c. DETAILED DESCRIPTION

[0048] The present application will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0049] The three-dimensional weaving forming method of the propeller blade preform of the present application first converts the original blade three-dimensional model with bending, twisting, variable cross-section and variable thickness characteristics into a planar model by means of three-dimensional software. On this basis, the thick region of the blade root in planar form is taken as the starting weaving section, and weaving is carried out according to the four-step three-dimensional multi-directional weaving process. In the weaving process, at least one whole-line yarn adding operation is required for the left and right boundaries of the section widening region, at least one whole-line yarn reducing operation is required for the left and right boundaries of the section narrowing region, at least one whole-line yarn reducing operation is required for the inside of the section thinning region, multiple connection operations are required between different layers of the same thickness, and at least one lifting operation is required for the blade bending region using a tool. After the above continuous weaving operations, an integral near-net shape propeller blade planar three-dimensional preform is formed. After being taken down from the fabric frame, trimmed and finely arranged, it is placed into the mold for pre-pressing and shaping to form the final propeller blade. The specific implementation is as follows:

[0050] Step 1, convert the blade 1 three-dimensional model into a planar model, as shown in Figures 1-5 ;

[0051] Step 1.1, as shown in Figure 1 , 2 , split the original propeller blade 1 three-dimensional model into blade face 2 and blade back 3 along the middle surface;

[0052] Step 1.2, layer the blade face 2 and blade back 3 three-dimensional models respectively along the blade thickness direction from the outside to the inside with a thickness of 1.0mm-1.5mm to form multiple layers of blades;

[0053] Step 1.3, as shown in Figure 3 , flatten each layer of blade obtained in step 1.2, and then re-construct to form planar blade face 4 and planar blade back 5;

[0054] Step 1.4, as shown in the figure, the planar form of the leaf surface 4 and the planar form of the leaf back 5 are designed along the width direction of the blade, and the regions with close width are combined to form the thickest region 6, the thicker regions 7 on both sides, and the thinner regions 8 on the boundary. Figure 4

[0055] Step 1.5, as shown in the figure, the planar form of the leaf surface 4 and the planar form of the leaf back 5 are designed according to the angle change along the length direction of the blade, and the regions with close angle are combined to determine the reference section of the bending of the blade. As shown in the figure, three reference sections are obtained, which are the first bending reference section 9, the second bending reference section 10, and the third bending reference section 11. Figure 5 Figure 5

[0056] Step 2, the planar form of the blade after step 1 is woven, as shown in the figure. Figures 6-9

[0057] Step 2.1, the three-dimensional preform weaving structure of the propeller blade 1 is designed according to the performance requirements of the blade. The three-dimensional five-directional structure (including weaving yarn and shaft yarn) with excellent axial performance is designed along the length direction of the blade, and the circumferential sixth-directional structure yarn is added along the width direction of the blade to improve the deformation ability of the blade due to bending and twisting.

[0058] Step 2.2, according to the section size of the planar form of the leaf surface 4 and the planar form of the leaf back 5 obtained in step 1.3, i.e. the length, width and thickness of the blade, the weaving process of each equal-thickness layer and different segments of the blade is designed, including the number of yarns required by each equal-thickness layer, the yarn arrangement method, the stitch height, the cycle number, the number of yarns added when the blade widens, the number of yarns reduced when the blade narrows, the number of rows reduced when the blade thins, and the position of the connecting point column between each equal-thickness layer.

[0059] Step 2.3, yarn arrangement. As shown in the figure, the three-dimensional weaving machine is placed symmetrically according to the linear step type, and the planar form of the blade root is selected as the starting weaving section. The yarns are 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 weaving machine, and the other end is hung on the three-dimensional weaving machine bottom plate through the tension line system. As shown in the figure, the yarns include weaving yarn, shaft yarn 12 and circumferential yarn. The weaving yarn is divided into main yarn 13 and edge yarn 14. The main yarn 13 is hung on the corresponding yarn carrier of the three-dimensional weaving machine bottom plate according to the row and column arrangement, and the edge yarn 14 is arranged around the main yarn to ensure that the number of yarns in each row and each column is the same. The shaft yarn 12 is arranged on both sides of the main yarn column, and the column where the weaving yarn or shaft yarn 12 is arranged is counted as one column. Figure 6 Figure 7

[0060] ​​​​​​Step 2.4.4, the weft yarn carriers in the adjacent columns are alternately moved vertically upward or downward along the column in the track direction by one weft yarn carrier position, and the axial yarns 12 in the adjacent rows in different equal-thickness layers exchange the yarn hanging positions for connection; at this time, the carriers all return to the initial positions, and one movement cycle is completed.

[0061] Step 2.4.1, the weft yarn carriers in the adjacent rows are alternately moved horizontally left or right along the row in the track direction by one weft yarn carrier position together with the axial yarn carriers of the row;

[0062] Step 2.4.2, the weft yarn carriers in the adjacent columns are alternately moved vertically upward or downward along the column in the track direction by one weft yarn carrier position, and the axial yarns 12 in the adjacent rows in different equal-thickness layers exchange the yarn hanging positions for connection;

[0063] Step 2.4.3, the weft yarn carriers in the adjacent rows are alternately moved horizontally left or right along the row in the track direction by one weft yarn carrier position together with the axial yarn carriers of the row, and the connecting yarn carriers;

[0064] Step 2.4.4, the weft yarn carriers in the adjacent columns are alternately moved vertically upward or downward along the column in the track direction by one weft yarn carrier position, and the axial yarns 12 in the adjacent rows in different equal-thickness layers exchange the yarn hanging positions for connection; at this time, the carriers all return to the initial positions, and one movement cycle is completed.

[0065] According to steps 2.4.1-2.4.4, the movement cycle is repeated until the designed number of cycles is completed.

[0066] Step 2.5, when a variable cross-section is encountered during weaving, the corresponding weaving method is used for weaving.

[0067] (1) Weft yarn increasing method when the blade widens:

[0068] As shown in Figure 8 When the weaving reaches the point where the cross-section of the blade widens, the yarn a15 needs to be added on both sides of the blade to meet the requirement of the cross-section widening. The reserved yarns hanging above the loom are arranged on the yarn carriers of the corresponding loom chassis on both sides of the blade according to the yarn arrangement rules of step 2.3, and the weaving is continued after the corresponding column of yarns is added. The yarn increasing unit at least includes one weft yarn and one axial yarn in the same row and the same column, i.e. two columns of yarns. The four-step method of yarn arrangement rules cannot be changed during the yarn increasing process.

[0069] (2) Weft yarn decreasing method when the blade narrows:

[0070] As shown in Figure 8As shown, when the cross-section of the blade narrows during weaving, the yarn b16 needs to be reduced on both sides of the blade to meet the requirement of narrowing the cross-section. The yarns on the yarn carriers of the weaving 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, reducing the corresponding column of yarn. After continuing to weave for two more cycles, the yarn is cut at the narrowing section of the blade. Each yarn reduction unit includes at least one adjacent weaving yarn and one bobbin 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.

[0071] (3) Methods for reducing yarn thickness when the blades become thinner:

[0072] like Figure 9 As shown, when the blade cross-section becomes thinner during weaving, it is necessary to reduce the amount of yarn c17 in the thickness direction of the blade to meet the requirement of thickening the cross-section. The innermost yarns on the blade's surface and back are separated from the yarn carrier according to the yarn arrangement rules in step 2.3, reducing the corresponding row of yarns. The yarn in this row is then locked in place by adjusting the weaving machine's row direction track to prevent it from participating in the weaving motion. After weaving for two more cycles, the separated corresponding row of yarns is removed from the yarn carrier and cut at the thinned section of the blade. The yarn reduction unit includes all the weaving yarns and bobbin yarns in at least one row, and the four-step yarn arrangement rules cannot be changed during the yarn reduction process.

[0073] (4) Method of increasing the circumferential sixth-axis structural yarn in the width direction of the blade:

[0074] To improve the blade's resistance to deformation, circumferential yarn needs to be 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 a fixed length of circumferential yarn is introduced between the even-numbered rows in the second half of each cycle. The length of the circumferential yarn is 5mm longer than the blade width.

[0075] (5) Connection method between layers of equal thickness:

[0076] After each weaving cycle, the positions of the yarn 12 hanging yarns in adjacent rows are exchanged according to the corresponding column positions of the blades between layers of different thicknesses, and then weaving continues to achieve layer connection.

[0077] (6) Methods for bending blades:

[0078] like Figure 5 As shown, when weaving reaches the blade bending reference sections 9, 10, and 11, a fixture is used to lift the fabric at a certain angle before continuing weaving. Each bending reference section requires a weaving triangle area, which is achieved by controlling a three-dimensional weaving machine. This means that weaving is asynchronous in different areas along the blade width direction, and synchronous weaving begins after reaching the blade bending reference section.

[0079] Step 2.6, repeat step 2.4, step 2.5, and accompany the tightening movement, to get the complete propeller blade three-dimensional preform.

[0080] Example 1

[0081] A ship propeller single blade three-dimensional preform is processed by using the three-dimensional weaving forming method of the propeller blade preform of the present application, the blade structure is as shown in Figure 1 The maximum size is 1402mm long, 1140mm wide, and 127mm thick. The original three-dimensional model of the blade is as shown in Figure 1 Firstly, it is split along the median surface into two parts, blade surface 2 and blade back 3 as shown in Figure 2 Then, the three-dimensional model of blade surface 2 is designed to be layered from outside to inside along the blade thickness direction with a thickness of 1.0mm-1.5mm, forming 1.5mm layered blade 34 layers and 1mm layered blade 13 layers. Each layer of blade is designed to be flattened and restructured to form the planar blade surface 4. Then, it is designed to be zoned along the blade width direction, merging the areas with close width, forming the thickest middle area 6, the thicker side areas 7, and the thinner boundary areas 8. Then, it is designed to be segmented along the blade length direction according to the angle change, merging the areas with close angle, and determining the reference cross sections 9, 10, 11 of the blade bending. Similarly, the three-dimensional model of blade back 3 is designed to be layered from outside to inside along the blade thickness direction with a thickness of 1.0mm-1.5mm, forming 1.5mm layered blade 36 layers and 1mm layered blade 10 layers. Each layer of blade is designed to be flattened and restructured to form the planar blade back 5. Then, it is designed to be zoned along the blade width direction, merging the areas with close width, forming the thickest middle area 6, the thicker side areas 7, and the thinner boundary areas 8. Then, it is designed to be segmented along the blade length direction according to the angle change, merging the areas with close angle, and determining the reference cross sections 9, 10, 11 of the blade bending.

[0082] The length direction of the blade is taken as the weaving forming direction, and the three-dimensional weaving forming method is as shown in Figure 7The yarns are arranged, the total number of yarns in the thickest middle region 6 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 side region 7 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 boundary region 8 is 986, and the yarns are arranged in 14 rows and 69 columns in the main array; the height of the pattern is designed to be 8 mm, and there are 180 cycles in total; the thickest middle region 6 starts from the 80th cycle, and the number of yarns on both sides is reduced by 2-8 columns per cycle; the thicker side region 7 starts from the 25th cycle, and the number of yarns on both sides is increased by 2-8 columns per cycle; the thinner boundary region 8 starts from the 25th cycle, and the number of yarns on both sides is increased by 2-12 columns per cycle; the number of yarns on the innermost side is reduced by 1 row per 2-4 cycles starting from the 11th cycle in the thickness direction; the three-dimensional preform is knitted according to the four-step method, the positions of the axial yarns corresponding to the column positions between each layer are exchanged once per cycle, and the other yarns are restored to the initial positions; the knitting machines are out of sync when knitting to the 33rd, 96th and 156th cycles, and the machines are used to lift the fabric once and then continue to knit; after 180 machine cycles and accompanied by the tightening movement, the single-blade three-dimensional preform of the ship propeller is obtained. After the preform is removed, it is arranged and molded into a mold to obtain a final blade that meets the requirements.

[0083] Example 2

[0084] Another single-blade three-dimensional preform of a ship propeller is processed by using the three-dimensional knitting forming method of the propeller blade preform of the application. The original three-dimensional model of the blade is shown in Figure 10 , and the maximum size is 1182 mm in length, 282 mm in width and 66 mm in thickness. First, the model is split along the middle surface into a blade surface 2 and a blade back 3 as shown in Figure 2 ; then the three-dimensional model of the blade surface 2 is designed to be layered from the outside to the inside along the thickness direction of the blade with a thickness of 1.0-1.5 mm, forming 1.5 mm layered blades in 17 layers and 1 mm layered blades in 7 layers, the blade of each layer is designed to be flat and restructured to form a flat blade surface 4, then the blade is designed to be partitioned along the width direction, the regions with close width are combined, the thickest middle region 6, the thicker side region 7 and the thinner boundary region 8 are formed, and the blade is designed to be segmented according to the angle change along the length direction, the regions with close angle are combined, and the reference cross sections 9, 10 and 11 of the blade bending are determined; similarly, the three-dimensional model of the blade back 3 is designed to be layered from the outside to the inside along the thickness direction of the blade with a thickness of 1.0-1.5 mm, forming 1.5 mm layered blades in 18 layers and 1 mm layered blades in 6 layers, the blade of each layer is designed to be flat and restructured to form a flat blade back 5, then the blade is designed to be partitioned along the width direction, the regions with close width are combined, the thickest middle region 6, the thicker side region 7 and the thinner boundary region 8 are formed, and the blade is designed to be segmented according to the angle change along the length direction, the regions with close angle are combined, and the reference cross sections 9, 10 and 11 of the blade bending are determined.

[0085] With the length direction of the blade as the weaving forming direction, according to Figure 7 The yarns in the thickest middle region 6 are arranged in 47 rows and 287 columns, the yarns in the thicker side regions 7 are arranged in 21 rows and 25 columns, and the yarns in the thinner boundary regions 8 are arranged in 8 rows and 35 columns. The height of the pattern is designed to be 8 mm, and the total number of cycles is 150. The yarns in the thickest middle region 6 are arranged to decrease by 2-6 columns on both sides from the 36th cycle, the yarns in the thicker side regions 7 are arranged to increase by 2-6 columns on both sides from the 12th cycle, and the yarns in the thinner boundary regions 8 are arranged to increase by 2-8 columns on both sides from the 12th cycle. In the thickness direction, the yarns are arranged to decrease by 1 row on the innermost side from the 5th cycle every 2-4 cycles. The three-dimensional preform is woven according to the four-step method, the positions of the yarns corresponding to the column positions between the layers are exchanged once every cycle, and the other yarns are restored to the initial positions. The weaving machines are required to weave out of synchronization to the 36th, 73rd and 157th cycles at the 19th, 49th and 86th cycles, respectively, the fabric is lifted once using a tool, and then the weaving is continued. After 157 machine cycles and accompanied by a tightening movement, the single-blade three-dimensional preform of the ship propeller is obtained.

[0086] Example 3

[0087] A third single-blade three-dimensional preform of a ship propeller is processed by using the three-dimensional weaving forming method of the propeller blade preform of the application. The maximum size of the blade is 1260 mm in length, 168 mm in width and 34 mm in thickness. The blade surface 2 three-dimensional model is designed to be layered from the outside to the inside along the thickness direction of the blade at a thickness of 1.0-1.5 mm, forming 6 layers of 1.5 mm layered blades and 8 layers of 1 mm layered blades. Each layer of the blade is designed to be flattened and restructured to form a planar blade surface 4, and then is designed to be partitioned and segmented. Similarly, the blade back 3 three-dimensional model is designed to be layered from the outside to the inside along the thickness direction of the blade at a thickness of 1.0-1.5 mm, forming 8 layers of 1.5 mm layered blades and 5 layers of 1 mm layered blades. Each layer of the blade is designed to be flattened and restructured to form a planar blade back 5, and then is designed to be partitioned and segmented.

[0088] With the length direction of the blade as the weaving forming direction, according to Figure 7The yarns are arranged, the total number of yarns in the thickest middle area 6 is 2914, and the yarns are arranged according to the main array of 24 rows and 117 columns; the total number of yarns in the thicker side area 7 is 451, and the yarns are arranged according to the main array of 16 rows and 27 columns; the total number of yarns in the thinner boundary area 8 is 360, and the yarns are arranged according to the main array of 7 rows and 43 columns; the height of the pattern is designed to be 8 mm, and a total of 165 cycles are counted; the thickest middle area 6 starts from the 15th cycle, and the number of yarns on both sides is reduced by 2-6 columns per cycle; the thicker side area 7 starts from the 6th cycle, and the number of yarns on both sides is increased by 2-6 columns per cycle; the thinner boundary area 8 starts from the 6th cycle, and the number of yarns on both sides is increased by 2-8 columns per cycle; in the thickness direction, the number of yarns on the innermost side is reduced by 1 row per 2-4 cycles starting from the 8th cycle; the three-dimensional preform is knitted according to the four-step method, the column positions of the axial yarns between each layer are exchanged once per cycle, and the other yarns are restored to the initial position; when knitting to the 24th and 85th cycles, the knitting machines need to be knitted out of sync to the 50th and 124th cycles, respectively, the tool is used to lift the fabric once, and then the knitting is continued; after 165 machine cycles and accompanied by a tightening movement, the single-blade three-dimensional preform of the ship propeller is obtained. After the preform is removed, it is arranged and loaded into the mold to be shaped to obtain the final blade that meets the requirements.

Claims

1. A method of three-dimensional braiding of a marine propeller blade preform, characterized in that, The method is implemented according to the following steps: Step 1: convert the three-dimensional model of the blade (1) into a planar model; Step 2: weave the planar blade obtained after step 1; Step 1 is specifically: Step 1.1: split the original three-dimensional model of the propeller blade (1) along the middle surface into two parts, the pressure surface (2) and the suction surface (3); Step 1.2: design the three-dimensional model of the pressure surface (2) and the suction surface (3) respectively in layers to form a multi-layer blade; Step 1.3: flatten each layer of the blade obtained in step 1.2, and then reconstruct to form a planar pressure surface (4) and a planar suction surface (5); Step 1.4: divide the planar pressure surface (4) and the planar suction surface (5) into zones along the width direction of the blade, combine the zones with similar width, and form the thickest middle zone (6), the thicker side zones (7), and the thinner boundary zones (8); Step 1.5: divide the planar pressure surface (4) and the planar suction surface (5) into segments according to the angle change along the length direction of the blade, combine the zones with similar angles, and determine the reference cross section of the blade bending; Step 2 is specifically: Step 2.1: design the weaving structure of the three-dimensional preform of the blade according to the performance requirements of the propeller blade (1); Step 2.2: design the weaving process of each equal-thickness layer and different segment of the blade according to the cross-sectional dimensions of the planar pressure surface (4) and the planar suction surface (5) obtained in step 1.3; Step 2.3: arrange the yarns; Step 2.4: start weaving from the root of the planar blade, and use the 1x1 four-step three-dimensional weaving process to weave; Step 2.5: during the weaving process, the left and right boundaries of the cross-sectional widening area need to be operated at least once by whole-column yarn adding; the left and right boundaries of the cross-sectional narrowing area need to be operated at least once by whole-column yarn reducing; the inner side of the cross-sectional thinning area needs to be operated at least once by whole-row yarn reducing; multiple connection operations are needed between different equal-thickness layers; at least one lifting operation is needed in the blade bending area; Step 2.6: repeat steps 2.4 and 2.5, and accompany with the tightening movement to obtain the complete three-dimensional preform of the propeller blade; The yarn arrangement method in step 2.3 is specifically: Place the three-dimensional weaving machine symmetrically according to the linear step type, divide the pressure surface and the suction surface, and select the planar blade root as the starting weaving cross section. Arrange and hang the yarns 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 weaving machine, and hang the other end on the three-dimensional weaving machine bottom plate through the tension line system. The yarns include weaving yarn, shaft yarn (12), and hoop yarn. The weaving yarn is divided into main yarn (13) and edge yarn (14). The main yarn (13) is hung on the corresponding yarn carrier of the three-dimensional weaving machine bottom plate according to the row and column arrangement, and the edge yarn (14) is arranged around the main yarn to ensure that the number of yarns in each row and each column is the same. The shaft yarn (12) is arranged on both sides of the main yarn column. The column where the weaving yarn or shaft yarn (12) is arranged is counted as one column; The blade bending method in step 2.5 is: When weaving to the bending reference section of the blade, the fabric is lifted to a certain angle using a tool, and then the weaving continues, wherein, before each bending reference section, a weaving triangle area is required, which is realized by controlling the three-dimensional weaving machine, that is, different areas are woven out of synchronization in the width direction of the blade, and then the weaving is synchronized after the bending reference section of the blade.

2. The method of claim 1, wherein the method further comprises the step of: The layering design in step 1.2 is specifically: layering the three-dimensional model of the pressure surface (2) and the suction surface (3) from the outside to the inside along the thickness direction of the blade with a thickness of 1.0mm-1.5mm.

3. The method of claim 1, wherein the method further comprises the step of: The weaving process in step 2.2 includes the number of yarns required by each thickness layer, the yarn arrangement method, the stitch height, the cycle number, the number of increased yarn columns when the blade widens, the number of reduced yarn columns when the blade narrows, the number of reduced row columns when the blade thins, and the position of the connecting point column between each thickness layer.

4. The method of claim 1, wherein the method further comprises the step of: The method for increasing yarns when the blade section widens in step 2.5 is: Yarns a (15) are added on both sides of the blade, the reserved yarns hanging above the weaving machine are arranged on the yarn carriers of the corresponding weaving machine bottom plates on both sides of the blade, and the corresponding yarn columns are increased after the yarns are increased, and then the weaving continues; wherein, the yarn increasing unit at least includes one adjacent weaving yarn and shaft yarn in the same row and column, that is, two yarn columns, and the four-step yarn arrangement rule cannot be changed during the yarn increasing process.

5. The method of claim 1, wherein the method further comprises the step of: The method for reducing yarns when the blade section narrows in step 2.5 is: Yarns b (16) are reduced on both sides of the blade, the yarns on the yarn carriers of the corresponding weaving machine bottom plates on both sides of the blade are removed from the yarn carriers to reduce the corresponding yarn columns, and then the weaving continues for 2 cycles, and the yarns are cut off at the blade narrowing section; wherein, the yarn reducing unit at least includes one adjacent weaving yarn and shaft yarn in the same row and column, that is, two yarn columns, and the four-step yarn arrangement rule cannot be changed during the yarn reducing process.

6. The method of claim 1, wherein the method further comprises the step of: The method for reducing yarns when the blade thins in step 2.5 is: Yarns c (17) are reduced in the thickness direction of the blade, the yarns on the innermost side of the pressure surface and the suction surface of the blade are separated from the yarn carriers to reduce the corresponding row yarns, and the row yarns are locked from participating in the weaving movement by adjusting the row direction track of the weaving machine, and then the weaving continues for 2 cycles, and the corresponding row yarns separated from the yarn carriers are removed, and the yarns are cut off at the blade thinning section; wherein, the yarn reducing unit includes all weaving yarns and shaft yarns in at least one row, and the four-step yarn arrangement rule cannot be changed during the yarn reducing process.

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