A method for adding and subtracting yarns in a three-dimensional woven structure preform

Abstract

The application provides a method for adding or subtracting yarns in a three-dimensional woven structure preform, which comprises the following steps: calculating the total number of added or subtracted yarns according to the row and column numbers of the initial and final cross sections; designing the total number of added or subtracted weft yarns according to the weaving length and weft density of the preform added or subtracted yarn range; if the theoretical total number of added or subtracted weft yarns is greater than the multiple of the number of warp yarn layers, the actual total number of added or subtracted weft yarns is adjusted to the multiple of the number of warp yarn layers; calculating the number of added or subtracted yarns per weft according to the total number of added or subtracted yarns and the total number of added or subtracted weft yarns; calculating the number of added or subtracted yarn positions per cross section according to the number of added or subtracted yarns per weft and the addition or subtraction of 2 yarns at each position; evenly distributing c positions on the same cross section; starting normal weaving, and performing the addition or subtraction of yarns every time the weft is introduced within the added or subtracted yarn range; if the weaving starts from the small end, the addition of yarns is performed; if the weaving starts from the large end, the subtraction of yarns is performed.

Description

A method for adding or subtracting yarns in a three-dimensional woven prefabricated structure Technical Field

[0001] This invention relates to the field of textile method technology, specifically to a method for adding or subtracting yarns in a three-dimensional woven structure preform. Background Technology

[0002] 2.5D woven structures, also known as interlocking structures, are a type of three-dimensional woven structure. Patent CN101503838B discloses a method for weaving a 2.5D integrally woven multi-tube fabric, including a yarn-adding / reducing method for changes in the cross-section of the 2.5D structure fabric. Specifically, when the horizontal cross-section of the connecting body increases, a shifting yarn-adding method is used to increase the warp yarns, effectively improving the porosity at the yarn-adding points. Conversely, when the horizontal cross-section of the connecting body decreases, a shifting yarn-reducing method is used to reduce the warp yarns, effectively improving the porosity at the yarn-reducing points. This method can also be used for yarn-adding / reducing processes of other components with changing cross-sections. However, the yarn-adding / reducing method in this patent involves the movement of four rows of yarns at the yarn-adding / reducing points, covering a wide range and is complex and prone to errors. After testing, porosity still appeared at the yarn-adding / reducing points using this method.

[0003] Patent CN107740220A discloses a weaving method for 2.5D angle-interlocking prefabricated components with a gradually decreasing cross-section. This method involves reducing yarn count at designed locations during the reduction weaving process. Yarns at the corresponding locations near the reduction points are then moved to their respective suspension points. To ensure a uniform fabric structure, some yarns are subsequently moved using a reed change operation to reduce the number of yarns used in the weaving. However, this patent requires yarn movement and reed changes after the reduction operation before normal weaving can begin, making the process complex and inefficient. Furthermore, this method is only applicable to 2.5D angle-interlocking prefabricated structures.

[0004] Three-dimensional woven structures, as commonly used prefabricated structures in the field of composite materials, play an important role in improving the mechanical properties of composite materials. Most composite material components are irregularly shaped components of various types. For rotating, variable-diameter components, maintaining a constant thickness during weaving requires yarn addition (reduction) operations. This is a key technology in the weaving process of irregularly shaped components. Generally, yarn addition (reduction) operations cause some damage to the prefabricated structure due to fiber breakage, especially with traditional straight-row yarn addition (reduction) methods. Therefore, it is necessary to invent a yarn addition (reduction) method that causes no or minimal damage to the prefabricated structure. Based on this, this invention provides a yarn addition and reduction method for three-dimensional woven structure prefabricated structures. Attached Figure Description

[0005] Figure 1 is a schematic diagram of the yarn reduction operation of the shallow cross-bending structure; wherein, Figure 1(a) is a schematic diagram of the first yarn reduction operation of the shallow cross-bending structure; Figure 1(b) is a schematic diagram of the second yarn reduction operation of the shallow cross-bending structure.

[0006] Figure 2 is a schematic diagram of the yarn reduction operation of the shallow cross-linked direct connection structure; wherein, Figure 2(a) is a schematic diagram of the first yarn reduction operation of the shallow cross-linked direct connection structure; Figure 2(b) is a schematic diagram of the second yarn reduction operation of the shallow cross-linked direct connection structure; Figure 2(c) is a schematic diagram of the third yarn reduction operation of the shallow cross-linked direct connection structure; Figure 2(d) is a schematic diagram of the fourth yarn reduction operation of the shallow cross-linked direct connection structure.

[0007] Figure 3 is a schematic diagram of the yarn reduction operation of the three-way orthogonal structure; wherein, Figure 3(a) is a schematic diagram of the first yarn reduction operation of the three-way orthogonal structure; Figure 3(b) is a schematic diagram of the second yarn reduction operation of the three-way orthogonal structure.

[0008] In this diagram, circles represent warp yarns, straight lines represent weft yarns, and circles with patterns indicate warp yarns that need to be subtracted.

[0009] Figure 4 is a schematic diagram of the yarn addition and subtraction positions of the cone;

[0010] Figure 5 is a schematic diagram of a cone with a circular cross-section; wherein, Figure 5(a) is a schematic diagram of the longitudinal cross-section of the cone with a circular cross-section; Figure 5(b) is a schematic diagram of the cross-section of the cone with a circular cross-section.

[0011] Figure 6 shows a schematic cross-section of the cylindrical and conical composite component; Figure 6(a) shows a schematic longitudinal section of the cylindrical and conical composite component; Figure 6(b) shows a schematic cross-section of the cylindrical and conical composite component.

[0012] Figure 7 is a schematic diagram of a cone with a rectangular cross section; wherein, Figure 7(a) is a schematic diagram of the longitudinal cross section of the cone with a rectangular cross section; and Figure 7(b) is a schematic diagram of the cross section of the cone with a rectangular cross section. Summary of the Invention

[0013] The purpose of this invention is to provide a method for adding or subtracting yarns in a three-dimensional woven prefabricated structure.

[0014] This invention provides a method for adding or subtracting yarns in a three-dimensional woven prefabricated structure, the steps of which include:

[0015] (1) Given the number of rows and columns of the initial and final cross sections, calculate the total number of yarns added or subtracted, N'.

[0016] N1=m1×n j Equation (1)

[0017] N2=m2×n j Equation (2)

[0018] N' = N1 - N2 (Equation 3)

[0019] in,

[0020] N'—Total number of yarns added or subtracted;

[0021] N1—Total number of major-end meridians;

[0022] N2—Total number of little-endian roots;

[0023] m1—number of big-end warp rows;

[0024] m2—Number of warp rows at the small end;

[0025] n j —Number of warp layers;

[0026] (2) Design the total number of wefts to be added or subtracted based on the weft length and weft density of the prefabricated body; if the theoretical total number of wefts to be added or subtracted is greater than a multiple of the number of warp layers, then adjust the actual total number of wefts to be added or subtracted to a multiple of the number of warp layers.

[0027] H = L × P w Equation (4)

[0028] in,

[0029] H—Total number of yarn wefts added or subtracted, rounded to the nearest integer;

[0030] L—Knitting length within the range of yarn addition or subtraction in the prefabricated body, in cm;

[0031] P w -Weft yarn density;

[0032] L×P w -Total latitude;

[0033] (3) Calculate the number of yarns to be added or subtracted per weft based on the total number of yarns added or subtracted and the total number of wefts to be added or subtracted; the number of yarns to be added or subtracted per weft should be an even number, and if the calculated value is an odd number, adjust it to an even number.

[0034]

[0035] Where O—the number of yarns to be added or subtracted per weft, taking an even number;

[0036] (4) Based on the number of yarns to be added or subtracted per weft and the number of yarns to be added or subtracted at each position, calculate the number of positions to add or subtract yarns at each cross section;

[0037]

[0038] Where c—the number of yarn addition or subtraction positions at the cross section, taken as an integer;

[0039] (5) Distribute the c positions evenly on the same cross-section;

[0040] (6) Start normal weaving. Add or subtract yarn each time you insert weft within the range of adding or subtracting yarn. If you start weaving from the small end, add yarn. If you start weaving from the large end, subtract yarn.

[0041] Furthermore, in step (2), the multiple is a natural number other than 0.

[0042] Furthermore, in step (2), the difference between the theoretical number of added or subtracted weft yarns and the multiple of the number of warp yarn layers does not exceed 10% of the total number of weft yarns.

[0043] Furthermore, in step (4), the number of positions for adding or subtracting yarn is no greater than half the number of columns at the smallest cross-section.

[0044] Furthermore, the small end refers to the end with fewer warp rows, and the large end refers to the end with more warp rows.

[0045] Furthermore, the woven fabric structure includes shallow cross-linking, shallow cross-linking, and three-way orthogonal structure.

[0046] Furthermore, when the woven fabric structure is a shallowly interlaced structure, its transformation process includes:

[0047] S1 first raises the odd-numbered column heddle eyes by 2 strokes, while keeping the even-numbered columns unchanged, and introduces n+1 layers of weft yarn. Then, add or subtract the 2 warp yarns of the 1st or nth layer in the two columns of warp yarns at each of the addition or subtraction positions.

[0048] S2 odd-numbered heddle eyes descend by 2 strokes, even-numbered heddle eyes rise by 2 strokes, introduce n+1 layers of weft yarn, and then add or subtract 2 warp yarns from the 2nd or n-1th layer of the two warp yarns at each addition or subtraction position;

[0049] Steps S3 and S1 and S2 form a weaving cycle. Repeat this cycle, moving one layer at a time, until all layers in the column have been added or subtracted yarn. At this point, one yarn addition or subtraction cycle is completed.

[0050] S4 The next step is to continue adding or subtracting yarn until the addition or subtraction of yarn is completed.

[0051] Furthermore, when the woven fabric structure is a shallow cross-linked structure, its transformation process includes:

[0052] S1 first raises the odd-numbered column heddle eyes by 2 strokes, while keeping the even-numbered columns unchanged, and introduces n+1 layers of weft yarn. Then, add or subtract the 2 warp yarns of the 1st or nth layer in the two columns of warp yarns at each of the addition or subtraction positions.

[0053] S2 The odd-numbered columns of heddles descend by 2 strokes, while the even-numbered columns remain stationary. At this point, the heddles are in the level position. Introduce n layers of weft yarn, and then add or subtract the two warp yarns from the second or (n-1)th layer of the two warp yarns in each of the two warp yarn columns at each addition or subtraction position.

[0054] S3 Odd-numbered heddle eyes remain stationary, even-numbered heddle eyes move up 2 strokes, introduce n+1 layers of weft yarn, and then add or subtract 2 warp yarns from the 3rd or n-2nd layer of the two warp yarns at each addition or subtraction position;

[0055] S4 The odd-numbered heddle eyes remain stationary, while the even-numbered heddle eyes descend two strokes. At this point, the heddle is in the flat position. Introduce n layers of weft yarn, and then add or subtract two warp yarns from the 4th or (n-3)th layer of warp yarns in each of the two warp yarn columns at the addition or subtraction positions.

[0056] Steps S1-S4 in S5 constitute one weaving cycle. Repeat this cycle, moving one layer at a time, until all layers in the column have been added or subtracted yarn. At this point, one yarn addition or subtraction cycle is completed.

[0057] S6 The next step is to continue adding or subtracting yarn until the addition or subtraction of yarn is completed.

[0058] Furthermore, when the woven fabric structure is a triaxial orthogonal structure, its transformation process includes:

[0059] S1 First, the odd-numbered columns of normal yarn heald frames are raised, and the even-numbered columns of normal yarn heald frames are lowered. Then, n+2 layers of weft yarn are introduced. Finally, the two warp yarns of the first or nth layer in the two columns of warp yarn at each addition or subtraction position are added or subtracted.

[0060] S2 normal yarn: odd-numbered heald frames descend, even-numbered heald frames rise, introducing n+2 layers of weft yarn. Then, at each addition or subtraction position, add or subtract two warp yarns from the 2nd or (n-1)th layer of warp yarns in the two warp columns;

[0061] Steps S3 and S1 and S2 form a weaving cycle. Repeat this cycle, moving one layer at a time, until all layers in the column have been added or subtracted yarn. At this point, one yarn addition or subtraction cycle is completed.

[0062] S4 The next step is to continue adding or subtracting yarn until the addition or subtraction of yarn is completed.

[0063] The beneficial effects of this invention are as follows:

[0064] Three-dimensional woven structures include shallow cross-linked structures, shallow cross-linked straight structures, and three-dimensional orthogonal structures. This invention provides a method for adding or subtracting yarns in a three-dimensional woven structure preform. The method uses a multi-heal loom for weaving and adds or subtracts yarns axially. Specifically, the yarns that would normally be added or subtracted at once from two rows are distributed uniformly along the weaving length (axial direction) and the thickness direction of each cross section, based on calculations. At each position, only two adjacent yarns after the rows are aligned are added or subtracted at a time. This method greatly reduces the problem of adding or subtracting too many yarns at once, thus avoiding the hole problem caused by many yarn breaks at the yarn addition or subtraction positions. Detailed Implementation

[0065] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] This invention provides a method for adding or subtracting yarns in a three-dimensional woven prefabricated structure, the steps of which include:

[0067] (1) Given the number of rows and columns of the initial and final cross sections, calculate the total number of yarns added or subtracted, N'.

[0068] N1=m1×n j Equation (1)

[0069] N2=m2×n j Equation (2)

[0070] N' = N1 - N2 (Equation 3)

[0071] in,

[0072] N'—Total number of yarns added or subtracted;

[0073] N1—Total number of major-end meridians;

[0074] N2—Total number of little-endian roots;

[0075] m1—number of big-end warp rows;

[0076] m2—Number of warp rows at the small end;

[0077] n j —Number of warp layers;

[0078] (2) Design the total number of wefts to be added or subtracted based on the weaving length and weft density of the prefabricated body; if the theoretical total number of wefts to be added or subtracted is greater than a multiple of the number of warp layers, then adjust the actual total number of wefts to be a multiple of the number of warp layers, and the difference between the theoretical total number of wefts to be added or subtracted and the multiple of the number of warp layers shall not exceed 10% of the total number of wefts;

[0079] H = L × P w Equation (4)

[0080] in,

[0081] H—Total number of yarn wefts added or subtracted, rounded to the nearest integer;

[0082] L—Knitting length within the range of yarn addition or subtraction in the prefabricated body, in cm;

[0083] P w -Weft yarn density;

[0084] L×P w -Total latitude;

[0085] (3) Calculate the number of yarns to be added or subtracted per weft based on the total number of yarns added or subtracted and the total number of wefts to be added or subtracted; the number of yarns to be added or subtracted per weft should be an even number, and if the calculated value is an odd number, adjust it to an even number.

[0086]

[0087] Where O—the number of yarns to be added or subtracted per weft, taking an even number;

[0088] (4) Based on the number of yarns to be added or subtracted per weft and the number of yarns to be added or subtracted at each position, calculate the number of positions to be added or subtracted at each cross section. This number of positions shall not be greater than half the number of columns at the smallest cross section.

[0089]

[0090] Where c—the number of yarn addition or subtraction positions at the cross section, taken as an integer;

[0091] (5) Distribute the c positions evenly on the same cross-section;

[0092] (6) Start normal weaving. Add or subtract yarn each time you insert weft within the range of adding or subtracting yarn. If you start weaving from the small end, add yarn. If you start weaving from the large end, subtract yarn.

[0093] In step (2), the step multiple is a natural number other than 0; the small end refers to the end with fewer warp yarns and the large end refers to the end with more warp yarns; the woven fabric structure includes shallow cross-bending, shallow cross-straightening, and three-way orthogonal structure.

[0094] Example 1

[0095] This embodiment provides a method for reducing yarn density in prefabricated structures with shallow cross-bending.

[0096] A cone-shaped component is woven with a die diameter of 100mm at the large end, 50mm at the small end, and a bevel length of 150mm. The overall thickness is uniform at 4mm, with a fiber volume fraction of 45%. Figure 5 shows a schematic diagram of the cone. The raw material used is T800-6K Toray carbon fiber, woven in a double-strand pattern with a shallow cross-linked structure. The cone is a component with a uniformly varying diameter, and the weaving process from beginning to end involves no changes except for adding or subtracting yarns. In this embodiment, weaving proceeds from the large end to the small end, with yarn reduction occurring at the large end as the initial cross-section.

[0097] The specific steps are as follows:

[0098] (1) Given that the number of rows and columns of the initial section is 360×6 and the number of rows and columns of the end section is 188×6, calculate the total number of warp reductions N' at this section.

[0099] N' = 2160 - 1128 = 1032 (Equation 1)

[0100] Calculations show that N' is 1032 roots.

[0101] (2) Design the total number of reduced wefts based on the fabric's reduced yarn range, weaving length, and weft density. If the theoretical total number of reduced wefts is greater than a multiple of the number of warp layers (this multiple is a natural number other than 0), then adjust the actual total number of reduced wefts to a multiple of the number of warp layers. However, generally, the difference between the theoretical total number of reduced wefts and the multiple of the number of warp layers should not exceed 10% of the total number of wefts.

[0102] H = 15 × 2 = 30 (Equation 2)

[0103] The designed weft density is 2 threads / cm. Calculations show that H is 30, which is 5 times the number of warp layers. Therefore, the total axial reduction weft count in this design is 30.

[0104] (3) Calculate the number of yarns to be reduced per weft based on the total number of yarns reduced and the total number of wefts to be reduced; the number of yarns to be reduced per weft should be an even number. If the calculated value is an odd number, adjust it to an even number.

[0105]

[0106] Calculations show that the total number of yarn reductions is 1032, and the total number of yarn reductions is 30, so the number of yarn reductions per weft is 34.

[0107] (4) Based on the number of yarns to be reduced per weft and the fact that 2 yarns are to be reduced at each position, calculate the number of yarn reduction positions at each cross section. This number of positions shall not be greater than half the number of columns at the smallest cross section.

[0108]

[0109] Calculations show that the number of yarn reduction positions at each cross-section is 17, which is less than half the number of columns at the smallest cross-section (94). In Figure 4, m represents the number of yarn reduction positions as 17.

[0110] (5) Distribute the 17 positions evenly on the same cross-section;

[0111] (6) Begin normal weaving. Within the yarn reduction range, perform yarn reduction operations each time you insert weft. The specific operation is as follows:

[0112] S1 first raises the odd-numbered column heddles by 2 strokes, while keeping the even-numbered columns stationary, and introduces 7 layers of weft yarn. Then, it subtracts the 2 warp yarns of the 6th layer from the two warp yarns in each reduction position (the subtracted warp yarns are the shaded circles in Figure 1(a)). Figure 1(a) is a schematic diagram of the first reduction operation, where n is 6.

[0113] In step S2, the odd-numbered heddle eyes are lowered by 2 strokes, and the even-numbered heddle eyes are raised by 2 strokes, introducing 7 layers of weft yarn. Then, the 2 warp yarns of the 5th layer in the two warp yarns at each yarn reduction position are removed (the removed warp yarns are the shaded circles in Figure 1(b)). Figure 1(b) is a schematic diagram of the second yarn reduction operation, where n is 6.

[0114] Step S3, S1-S2, constitutes one weaving cycle. This cycle is repeated, moving one layer at a time, until all layers in the column have been reduced in yarn. At this point, one yarn reduction cycle is complete.

[0115] S4 continues to reduce yarn count until five yarn reduction cycles are completed.

[0116] Example 2

[0117] This embodiment provides a method for reducing yarn density in shallow cross-linked prefabricated structures.

[0118] A component with a conical tail is woven. The large end of the die has a diameter of 70cm, the small end has a diameter of 30cm, the bevel section of the die is 41cm long, the straight section of the die is 20cm long, and the overall thickness is uniform at 10cm. The fiber volume fraction is 45%. Figure 6 shows a schematic diagram of the longitudinal section of this component. The raw material used is Toray T700-12K carbon fiber, woven in double strands with a shallow cross-linked structure. This component is a combination of a straight cylinder and a conical shape. The weaving process from beginning to end involves no changes except for yarn reduction. In this embodiment, weaving is performed from the large end to the small end, with yarn reduction occurring during the process.

[0119] The specific steps are as follows:

[0120] (1) Given that the number of rows and columns of the initial section is 2828×38 and the number of rows and columns of the final section is 1380×38, calculate the total number of warp reductions N' at this section.

[0121] N' = 107464 - 52440 = 55024 (Equation 1)

[0122] Calculations show that N' is 55024 roots.

[0123] (2) Design the total number of reduced wefts based on the fabric's reduced yarn range, weaving length, and weft density. If the theoretical total number of reduced wefts is greater than a multiple of the number of warp layers (this multiple is a natural number other than 0), then adjust the actual total number of reduced wefts to a multiple of the number of warp layers. However, generally, the difference between the theoretical total number of reduced wefts and the multiple of the number of warp layers should not exceed 10% of the total number of wefts.

[0124] H = 41 × 2 = 82 (Equation 2)

[0125] The design weft density is 1 thread / cm. Due to the shallow cross weft structure, the actual weft density of the outer and inner layers is 2 threads / cm. Through calculation, H is 82. Since 82 > 38 × 2, the actual total reduction weft is adjusted to twice the number of warp layers, that is, the total axial reduction weft in this design is 76.

[0126] (3) Calculate the number of yarns to be reduced per weft based on the total number of warp yarns and the total number of weft yarns to be reduced; the number of yarns to be reduced per weft should be an even number. If the calculated value is an odd number, adjust it to an even number.

[0127]

[0128] Calculations show that 724 yarns need to be reduced per weft.

[0129] (4) Based on the number of yarns to be reduced per weft and the reduction of 2 yarns at each position, calculate the number of yarn reduction positions at each cross section. This number of positions shall not be greater than half the number of columns at the smallest cross section.

[0130]

[0131] Calculations show that the number of yarn reduction positions at each cross-section is 362, which is less than half the number of columns at the smallest cross-section (690). As shown in Figure 4, m represents the number of yarn reduction positions as 362.

[0132] (5) Distribute the 362 positions evenly on the same cross section.

[0133] (6) When weaving the slope section, a yarn reduction operation is performed every time weft is inserted within the yarn reduction range. The specific operation is as follows:

[0134] S1 first raises the odd-numbered column heddles by 2 strokes, while keeping the even-numbered columns stationary, and introduces 39 layers of weft yarn. Then, the two warp yarns of the 38th layer in the two columns of warp yarn at each yarn reduction position are removed. Figure 2(a) is a schematic diagram of the first yarn reduction operation, where n is 38.

[0135] In step S2, the odd-numbered columns of heddles descend by 2 strokes, while the even-numbered columns remain stationary. At this point, the heddles are in the flat position. 38 layers of weft yarn are introduced, and then the two warp yarns of the 37th layer in each of the two warp yarns at each yarn reduction position are removed. Figure 2(b) is a schematic diagram of the second yarn reduction operation, where n is 38.

[0136] In step S3, the odd-numbered heddle eyes remain stationary, while the even-numbered heddle eyes are raised by 2 strokes to introduce 39 layers of weft yarn. Then, the two warp yarns of the 36th layer in each of the two warp yarns at each yarn reduction position are removed. Figure 2(c) is a schematic diagram of the third yarn reduction operation, where n is 38.

[0137] In step S4, the odd-numbered heddle eyes remain stationary, while the even-numbered heddle eyes descend two strokes. At this point, the heddle is at its flat position. 38 layers of weft yarn are introduced, and then the two warp yarns of the 35th layer in each of the two warp yarns at each yarn reduction position are removed. Figure 2(d) is a schematic diagram of the fourth yarn reduction operation, where n is 38.

[0138] Steps S1-S4 in S5 constitute one weaving cycle. Repeat this cycle, moving one layer at a time, until all layers in the column have been reduced in yarn. At this point, one yarn reduction cycle is complete.

[0139] S6 continues to reduce yarn until two yarn reduction cycles are completed.

[0140] (7) Weave straight sections, weave normally until the weaving is finished.

[0141] Example 3

[0142] This embodiment provides a method for reducing yarn density in a three-dimensional orthogonal prefabricated structure.

[0143] A conical component with a rectangular cross-section is woven. The large end of the die is 5cm wide and 10cm long, the small end is 2.5cm wide and 5cm long, the bevel section of the die is 20cm long, the overall thickness is uniform at 5mm, and the fiber volume fraction is 45%. Figure 7 shows a schematic diagram of the longitudinal section of this component. The raw material used is Toray T300-3K carbon fiber, double-stranded, with a triaxial orthogonal structure. This component is a type of conical component with a rectangular cross-section, and the weaving process from beginning to end, except for yarn reduction, involves no other process changes. In this embodiment, weaving is performed from the large end to the small end, with yarn reduction occurring during the process.

[0144] The specific steps are as follows:

[0145] (1) Given that the number of rows and columns of the initial section is 408×6 and the number of rows and columns of the end section is 228×6, calculate the total number of warp reductions N' at this section.

[0146] N' = 408 × 6 - 228 × 6 = 1080 (Equation 1)

[0147] Calculations show that N' is 1080 roots.

[0148] (2) Design the total number of reduced wefts based on the fabric's reduced yarn range, weaving length, and weft density. If the theoretical total number of reduced wefts is greater than a multiple of the number of warp layers (this multiple is a natural number other than 0), then adjust the actual total number of reduced wefts to a multiple of the number of warp layers. However, generally, the difference between the theoretical total number of reduced wefts and the multiple of the number of warp layers should not exceed 10% of the total number of wefts.

[0149] H = 20 × 3 = 60 (Equation 2)

[0150] The designed weft density is 3 threads / cm. Calculations show that H is 60, which is 10 times the number of warp layers. Therefore, the total axial reduction weft count in this design is 60.

[0151] (3) Calculate the number of yarns to be reduced per weft based on the total number of warp yarns and the total number of weft yarns to be reduced; the number of yarns to be reduced per weft should be an even number. If the calculated value is an odd number, adjust it to an even number.

[0152]

[0153] Calculations show that 18 yarns need to be reduced per weft.

[0154] (4) Based on the number of yarns to be reduced each time and the reduction of 2 yarns at each position, calculate the number of yarn reduction positions at each cross section. This number of positions shall not be greater than half the number of columns at the smallest cross section.

[0155]

[0156] Calculations show that the number of yarn reduction positions at each cross-section is 9, which is less than half the number of columns at the smallest cross-section (114). As shown in Figure 4, m represents the number of yarn reduction positions as 9.

[0157] (5) Distribute the nine positions evenly on the same cross section.

[0158] (6) Begin knitting. Within the yarn reduction range, perform yarn reduction operations each time you insert weft. The specific operation is as follows:

[0159] S1 First, the odd-numbered columns of normal yarn heald frames are raised, and the even-numbered columns of normal yarn heald frames are lowered, introducing 8 layers of weft yarn. Then, the 2 warp yarns in the 6th layer of the two columns of warp yarn at each yarn reduction position are removed. Figure 3(a) is a schematic diagram of the first yarn reduction operation, where n is 6.

[0160] In step S2, the odd-numbered heald frames of the normal yarn are lowered and the even-numbered heald frames are raised, introducing 8 layers of weft yarn. Then, the 2 warp yarns of the 5th layer in the two warp yarns at each yarn reduction position are removed. Figure 3(b) is a schematic diagram of the second yarn reduction operation, where n is 6.

[0161] Step S3, S1-S2, constitutes one weaving cycle. This cycle is repeated, moving one layer at a time, until all layers in the column have been reduced in yarn. At this point, one yarn reduction cycle is complete.

[0162] S4 continues to reduce yarn until 10 yarn reduction cycles are completed.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for adding or subtracting yarns in a three-dimensional woven prefabricated structure, characterized in that the steps include... include: (1) Given the number of rows and columns of the initial and final cross sections, calculate the total number of yarns added or subtracted, N'. Equation (1) Equation (2) Equation (3) Where, N'—total number of yarns added or subtracted; N1—total number of warp ends at the large end; N2—total number of warp ends at the small end; m1—number of warp rows at the large end; m2—number of warp rows at the small end; n j —Number of warp layers; (2) Design the total number of wefts to be added or subtracted based on the weaving length and weft density of the prefabricated body; If the theoretical total number of wefts to be added or subtracted is greater than a multiple of the number of warp layers, then adjust the actual total number of wefts to be a multiple of the number of warp layers; Formula (4) Where, H—total number of yarns added or subtracted, taken as an integer; L—knitting length within the range of yarn addition or subtraction in the prefabricated body, in cm; P w -Weft yarn density, roots / cm; (3) Calculate the number of yarn roots to be added or subtracted per weft based on the total number of yarns added or subtracted and the total number of wefts added or subtracted; the number of yarn roots to be added or subtracted per weft is even, and if the calculated value is odd, it is adjusted to an even number; Formula (5) Where, O—the number of yarns to be added or subtracted per weft, take an even number; (4) Based on the number of yarns to be added or subtracted per weft, and the number of yarns to be added or subtracted at each position, calculate the number of positions to be added or subtracted at each cross section; In formula (6), c is the number of positions for adding or subtracting yarn in the cross section, which is an integer; (5) distribute c positions evenly on the same cross section; (6) start normal weaving, and perform the addition or subtraction of yarn each time weft is inserted within the range of adding or subtracting yarn. If weaving starts from the small end, perform the addition of yarn; if weaving starts from the large end, perform the subtraction of yarn.

2. The method for adding or subtracting yarns in a three-dimensional woven prefabricated structure according to claim 1, characterized in that, In step (2), the multiples are natural numbers other than 0.

3. The method for adding or subtracting yarns in a three-dimensional woven prefabricated structure according to claim 1, characterized in that, In step (2), the difference between the theoretical total number of added or subtracted weft yarns and the multiple of the number of warp yarn layers shall not exceed 10% of the total number of weft yarns.

4. The method for adding or subtracting yarns in a three-dimensional woven prefabricated structure according to claim 1, characterized in that, In step (4), the number of positions for adding or subtracting yarn should not exceed half the number of columns at the smallest cross section.

5. The method for adding or subtracting yarns in a three-dimensional woven prefabricated structure according to claim 1, characterized in that, The small end refers to the end with fewer warp rows, and the large end refers to the end with more warp rows.

6. The method for adding or subtracting yarns in a three-dimensional woven prefabricated structure according to claim 1, characterized in that, The woven fabric structure includes shallow cross-bending, shallow cross-straightening, and three-way orthogonal.

7. The method for adding or subtracting yarns in a three-dimensional woven prefabricated structure according to claim 6, characterized in that, When the woven fabric structure is a shallow cross-linked structure, the change process includes: S1 First, the odd-numbered column heddle eyes are raised by 2 strokes, while the even-numbered columns remain stationary, and n+1 layers of weft yarn are introduced. Then, 2 warp yarns from the 1st or nth layer of the two warp yarns at each of the addition or subtraction positions are added or subtracted; S2 The odd-numbered column heddle eyes are lowered by 2 strokes, while the even-numbered column heddle eyes are raised by 2 strokes, and n+1 layers of weft yarn are introduced. Then, 2 warp yarns from the 2nd or (n-1)th layer of the two warp yarns at each of the addition or subtraction positions are added or subtracted; S3 Steps S1 and S2 constitute a weave cycle. This cycle is repeated, moving one layer at a time, until all layers of the column have been added or subtracted. At this point, one addition or subtraction cycle is completed; S4 The next step continues to add or subtract yarn until the addition or subtraction is completed.

8. The method for adding or subtracting yarns in a three-dimensional woven prefabricated structure according to claim 6, characterized in that, When the woven fabric structure is a shallow cross-linked structure, the process includes: S1 First, the odd-numbered heddle eyes are raised by 2 strokes, while the even-numbered heddle eyes remain stationary. n+1 layers of weft yarn are introduced, and then two warp yarns from the 1st or nth layer of the two warp yarns at each of the addition or subtraction positions are added or subtracted; S2 The odd-numbered heddle eyes are lowered by 2 strokes, while the even-numbered heddle eyes remain stationary, now in the heddle level position. n layers of weft yarn are introduced, and then two warp yarns from the 2nd or (n-1)th layer of the two warp yarns at each of the addition or subtraction positions are added or subtracted; S3 The odd-numbered heddle eyes remain stationary, while the even-numbered heddle eyes are raised by 2 strokes, introducing n+1 layers of weft yarn. Then, two warp yarns from the 3rd or (n-2)th layer of the two warp yarns at each of the addition or subtraction positions are added or subtracted; S4 The odd-numbered heddle eyes remain stationary, while the even-numbered heddle eyes descend two strokes, reaching the heddle level position. Introduce n layers of weft yarn, then add or subtract two warp yarns from the 4th or (n-3)th layer of warp yarn in each of the two warp yarn columns at each addition or subtraction position; Steps S1-S4 constitute one weave cycle. Repeat this cycle, moving one layer at a time, until all layers in the column have been subtracted. At this point, one subtraction cycle is complete; Step S6: Continue adding or subtracting yarn until the addition or subtraction is complete.

9. The method for adding or subtracting yarns in a three-dimensional woven prefabricated structure according to claim 6, characterized in that, When the woven fabric structure is a three-way orthogonal structure, its transformation process includes: S1 First, the odd-numbered columns of normal yarn heald frames are raised, and the even-numbered columns of normal yarn heald frames are lowered, introducing n+2 layers of weft yarn. Then, two warp yarns from the 1st or nth layer of the two columns of warp yarns at each yarn addition or subtraction position are added or subtracted; S2 The odd-numbered columns of normal yarn heald frames are lowered, and the even-numbered columns of normal yarn heald frames are raised, introducing n+2 layers of weft yarn. Then, two warp yarns from the 2nd or (n-1)th layer of warp yarns at each yarn addition or subtraction position are added or subtracted; S3 Steps S1 and S2 constitute a weave cycle. This cycle is repeated, moving one layer at a time, until all layers of yarn addition or subtraction in the column are completed. At this point, one yarn addition or subtraction cycle is completed; S4 The next step continues to add or subtract yarn until the yarn addition or subtraction is completed.

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