A yarn reduction method for three-dimensional woven fabrics

Abstract

The present invention discloses a yarn reduction method for three-dimensional woven fabrics, the method comprising: in a three-dimensional four-step weaving process, taking a yarn reduction unit as a reference, the yarn reduction unit is two rows of odd spindles and two rows of even spindles arranged adjacently after 0 to 4 standard cycles, and in 0 to 4 standard cycles, performing a yarn reduction operation on the yarn reduction points in the yarn reduction unit in a dispersed state, and performing a yarn doubling operation in a gathered state. The method has extremely high designability, so the continuity and structural integrity of the three-dimensional fabric can be guaranteed; the preparation method can realize the overall weaving and manufacturing of complex surface fabrics with three-dimensional weaving reduced rows or layers, and the method cleverly utilizes the spindle movement law of the three-dimensional four-step method, so that the yarn reduction points are dispersed with the increase of weaving cycles and then the yarn reduction operation is implemented, eliminating the defects caused by the concentration of the yarn reduction points, thereby ensuring the mechanical properties of the composite material, and at the same time, it is simple to operate, has wide applicability, and strong designability.

Description

Technical Field

[0001] The invention relates to a yarn reduction method for three-dimensional woven fabrics, and belongs to the field of three-dimensional fabric weaving. Background Art

[0002] With the increasing demand for high-performance composite materials in industries such as aerospace, ships and vessels, and green energy, the high-performance fiber composite material industry is booming. High-performance fiber composite materials are an advanced form of fiber-reinforced composite materials. They are obtained by textile processing methods to obtain a two-dimensional or three-dimensional textile reinforcement structure of reinforcing fibers, and then compounded with a matrix material. They have many advantages such as tight interweaving structure, good integrity, and excellent mechanical properties. In extreme environments or environments with special requirements for structural functions, the performance of conventional two-dimensional laminated composite materials is difficult to meet applicable needs. Composite materials with three-dimensional fabrics as composite reinforcements are favored by the industry. Among them, three-dimensional weaving technology is one of the important process technologies for integrated molding of three-dimensional fabrics. Through the weaving method, the fiber yarn bundles are processed into a three-dimensional textile structure according to a certain interweaving rule, making it a flexible fiber aggregate with a certain shape and internal structure.

[0003] With the continuous expansion of the application field of three-dimensional weaving technology, higher requirements are put forward for composite materials. In order to meet the requirements of high uniformity and high profiling accuracy of three-dimensional fabrics, researchers have conducted more and more research on the structure, weaving method, yarn addition and subtraction technology of three-dimensional fabrics, but the method of defect-free yarn addition and subtraction is relatively lacking. In the three-dimensional weaving process, yarn reduction technology is more widely used. The existing yarn reduction methods for three-dimensional woven fabrics are generally divided into two types: A direct reduction of rows or layers; B surface thinning and yarn reduction, such as the net size profiling yarn reduction weaving method for composite materials using three-dimensional multi-directional braids disclosed in Chinese patent CN102938019B. The disadvantages of direct reduction of rows or layers are: ① low-density defects are formed at the location of the reduced rows or layers, even penetrating; ② great influence on the performance of composite materials. The disadvantages of surface thinning and yarn reduction are: ① yarn can only be reduced on the surface of the fabric, and the designability is poor; ② only suitable for fabrics with equal thickness of cross section; ③ complex design control and long development cycle; ④ there is a yarn reduction limit and the adaptability is not wide.

[0004] Both of the above existing yarn reduction methods cannot meet the high requirements of new composite materials for complex surfaces and internal uniformity. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for reducing yarns in three-dimensional woven fabrics. The preparation method can realize the overall weaving and manufacturing of complex surface fabrics with reduced rows or layers in three-dimensional weaving, and can eliminate the defects caused by the concentration of yarn reduction points. At the same time, the method is simple to operate, has wide applicability, and is highly designable.

[0006] The technical solution adopted by the present invention is:

[0007] A yarn reduction method for three-dimensional woven fabrics. In a three-dimensional four-step weaving process, a yarn reduction unit is used as a reference. The yarn reduction unit is two rows of odd spindles and two rows of even spindles arranged adjacent to each other after 0 to 4 standard cycles. Within 0 to 4 standard cycles, a yarn reduction operation is performed on the yarn reduction points in the yarn reduction unit in a dispersed state, and a yarn doubling operation is performed in a gathered state.

[0008] Furthermore, the three-dimensional woven fabric is a three-dimensional fabric formed by a three-dimensional four-step weaving method, and the cross-section of the three-dimensional fabric is I-shaped, T-shaped, V-shaped, U-shaped or ring-shaped.

[0009] Furthermore, the yarn reduction units are provided in a plurality according to the fabric shape, and the number and position of the yarn reduction units are flexibly designed according to the fabric shape.

[0010] Furthermore, the yarn reduction method is used to reduce layers and / or columns.

[0011] Further, the yarn reduction method comprises: a delayed dispersed yarn reduction step and a pre-dispersed yarn reduction step;

[0012] (1) During the overall forming process of the three-dimensional woven fabric, after a standard cycle is completed, the yarns on the two rows of odd-numbered spindles that need to be reduced in the yarn reduction unit are merged into one of the spindles, and the yarns on the two rows of even-numbered spindles that need to be reduced are merged into one of the spindles to form two rows of roving spindles. After continuing to weave 2 to 4 standard cycles, the yarns on the roving spindles in a dispersed state are thinned to complete a delayed dispersed yarn reduction;

[0013] (2) During the overall forming process of the three-dimensional woven fabric, after a standard cycle is completed, the yarns on the spindles in a dispersed state that need to be reduced are thinned to form fine yarn spindles; after continuing to weave 2 to 4 standard cycles, the fine yarn spindles are arranged into a yarn reduction unit, and the yarns on the two rows of odd-numbered fine yarn spindles in the yarn reduction unit are merged into one of the spindles, and the yarns on the two rows of even-numbered fine yarn spindles are merged into one of the spindles, completing a pre-dispersed yarn reduction.

[0014] Further, step (1) comprises:

[0015] (1.1) The yarn reduction unit is composed of two rows of odd-numbered spindles and two rows of even-numbered spindles arranged adjacently. After a standard cycle is completed, the yarns on the two rows of odd-numbered spindles are merged in the same layer onto one of the spindles, and the yarns on the two rows of even-numbered spindles are merged in the same layer onto one of the spindles to form two rows of roving spindles. After weaving for 2 to 4 standard cycles, the yarns on the roving spindles in a dispersed state are thinned to complete a delayed dispersed row reduction and yarn reduction.

[0016] (1.2) The yarn reduction unit is composed of two layers of odd-numbered spindles and two layers of even-numbered spindles arranged adjacent to each other. After a standard cycle is completed, the yarns on the two layers of odd-numbered spindles are merged in the same column onto one of the spindles, and the yarns on the two layers of even-numbered spindles are merged in the same column onto one of the spindles to form two layers of coarse yarn spindles. After weaving for 2 to 4 standard cycles, the yarns on the dispersed coarse yarn spindles are thinned to complete a delayed dispersed layer and yarn reduction.

[0017] Further, step (2) comprises:

[0018] (2.1) The yarns on the spindles in a dispersed state that need to be reduced are thinned to form fine yarn spindles; after continuing to weave 2 to 4 standard cycles, the fine yarn spindles are arranged into a yarn reduction unit, wherein the yarn reduction unit is composed of two columns of odd-numbered spindles and two columns of even-numbered spindles arranged adjacently, and the yarns on the two columns of odd-numbered spindles in the yarn reduction unit are merged into one of the spindles, and the yarns on the two columns of even-numbered spindles are merged into one of the spindles, thereby completing a pre-dispersed column reduction and yarn reduction;

[0019] (2.2) The yarns on the spindles that need to be reduced are thinned to form fine yarn spindles; after continuing to weave 2 to 4 standard cycles, the fine yarn spindles are arranged into a yarn reduction unit, and the yarn reduction unit is composed of two layers of odd-numbered spindles and two layers of even-numbered spindles arranged adjacent to each other, and the yarns on the two layers of odd-numbered fine yarn spindles in the yarn reduction unit are merged into one of the spindles, and the yarns on the two layers of even-numbered fine yarn spindles are merged into one of the spindles, thereby completing a pre-dispersed layer reduction and yarn reduction.

[0020] Furthermore, in step (1), the thinning operation is to remove any number of yarns on the spindle. Preferably, the yarn removed is half of the total amount of the original yarn, which is conducive to maintaining the uniformity of the fabric after the yarn is reduced.

[0021] Furthermore, in step (2), the thinning operation is to remove any number of yarns on the spindle. Under extreme conditions, all the yarns on the spindle can be removed, and in this process, the yarn doubling step is omitted.

[0022] Furthermore, the yarn reduction unit is subjected to full or partial yarn reduction. The partial yarn reduction operation is performed to adapt to the knitting of fabrics with complex cross-sectional shapes.

[0023] The beneficial effects of the present invention are:

[0024] 1. The method of the present invention can solve technical problems such as complex fabric shape, local special load-bearing requirements, and overall weaving molding. The three-dimensional fabric prepared by the present invention has good integrity and greatly improved mechanical properties, thereby improving the overall mechanical properties of the composite material.

[0025] 2. Based on the traditional three-dimensional weaving four-step process, the present invention realizes defect-free overall weaving by dispersing the yarn reduction points; the method has extremely high designability, so the accuracy of the complex shape of the three-dimensional fabric can be guaranteed; the method can eliminate the defects of the three-dimensional fabric when the yarn is reduced, thereby improving the mechanical properties of the composite material; the method cleverly utilizes the spindle movement law of the three-dimensional four-step method, and the method is simple to operate and has wide adaptability, and can be applied to weaving of different shapes, such as rectangle, trapezoid, circular ring, conical ring, T-shape, U-shape, V-shape, special shape, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the shape of the 3D thin-walled conical parts obtained in Example 1 and Example 2 of the present invention. In the figure, the direction of the arrow is the weaving direction.

[0027] Figure 2 for Figure 1 Schematic diagram of the arrangement of some spindles after a cycle of the conical workpiece is completed.

[0028] Figure 3 for Figure 2 Schematic diagram of the structure in which the two columns of yarn to be removed are merged into the adjacent columns.

[0029] Figure 4 for Figure 3 Schematic diagram of the merged structure.

[0030] Figure 5 for Figure 4 Schematic diagram of the structure after sorting.

[0031] Figure 6 for Figure 5 Schematic diagram of the structure after 2 cycles of exercise.

[0032] Figure 7 for Figure 6 Schematic diagram of the structure of the "roving" after being reduced.

[0033] Figure 8 For Example 2 Figure 1 Schematic diagram of the arrangement of spindles after a cycle is completed in a certain part of the cross-section of the workpiece shown.

[0034] Fig. 9 for Figure 8 Schematic diagram of the structure after 2 cycles of exercise.

[0035] Fig.10 for Figure 8 Schematic diagram of the structure of an empty spindle after 2 cycles of movement.

[0036] Fig.11 for Fig.10 Schematic diagram of the structure after sorting.

[0037] Fig.12 For Example 2 Figure 1 Schematic diagram of the arrangement of spindles after a cycle is completed in a certain part of the cross-section of the workpiece shown.

[0038] Fig.13 for Fig.12 Schematic diagram of the structure after 2 cycles of exercise.

[0039] Fig.14 for Fig.13 Schematic diagram of the merged structure.

[0040] Fig.15 for Fig.14 Schematic diagram of the structure after sorting. DETAILED DESCRIPTION

[0041] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0042] In the embodiments, Tex refers to the fineness of the woven yarn bundle, that is, the weight of the yarn bundle per kilometer.

[0043] In the embodiments, the number of yarns refers to the number of spindles, and one yarn may be a plurality of ply yarns.

[0044] Example 1

[0045] The three-dimensional four-step method is used to weave Figure 1 The thin-walled conical part shown has an inner diameter of φ190mm, a height of 200mm, and a wall thickness of 5mm. The weaving starts with the cross section at the large end as the reference section, and the weaving direction is along the height direction of the cylinder. Figure 1 Indicated by the direction of the arrow.

[0046] This embodiment adopts a three-dimensional four-way braiding structure and uses T300-3K fiber for braiding. The dynamic yarn has 7 strands, the mother-direction flower knot is 95mm / 10 flowers, the circumferential flower knot is 70mm / 10 flowers, the fiber volume fraction is 50.0%, and the number of dynamic yarns required for the reference cross-section design is 1575, which are arranged in 9 layers and 182 rows along the ring.

[0047] According to the structural design, in order to meet the appearance requirements of thin-walled conical parts, 4 columns of yarn need to be reduced for each knitting cycle. According to the movement law of the three-dimensional four-step method, the yarn is reduced in groups of 2 columns, that is, the yarn is reduced in two yarn reduction units, and two positions are selected symmetrically on the ring to perform the column and yarn reduction operation. Taking one of them (a yarn reduction unit) as an example, the column and yarn reduction method of the delayed dispersed yarn reduction point of the present invention is described as follows:

[0048] (1) See Figure 2 , Figure 2The figure is a schematic diagram of the arrangement of spindles at a certain point in the ring after a cycle ends. The spindles shown in the box form a yarn reduction unit. If you choose to reduce the 3rd and 4th columns of yarn, first merge the yarns on the 3rd and 4th columns of spindles to the adjacent 1st and 2nd columns of spindles with the same motion law, that is, merge the 1st and 3rd columns at the same level, and merge the 2nd and 4th columns at the same level, such as Figure 3 After the merging is completed, two columns of "roving" are formed, namely, column 1 and column 2 yarns, as shown in Figure 4 As shown in the figure, the yarn has lost 2 rows. Figure 5 .

[0049] (2) After weaving two standard cycles according to the design requirements, the two combined columns of "roving", i.e., columns 1 and 2, are dispersed according to the movement law of the spindles, such as Figure 6 As shown in the figure, the thinning operation of the "roving" is carried out at this time. According to the design requirements, half of the yarn in each "roving" is reduced. After the reduction, the yarn is arranged as follows Figure 7 As shown. In this way, the fabric is reduced in a dispersed manner. Repeat the above steps until the weaving is completed. Figure 1 The thin-walled conical part with uniform wall thickness is shown.

[0050] In the existing three-dimensional weaving process, weaving is achieved by reducing rows and yarns by directly removing two rows of yarns. This method will form low-density defects that penetrate the thickness direction of the fabric, seriously affecting the performance of the composite material.

[0051] The fabric woven by the method of the present invention adopts the yarn reduction method of dispersed yarn reduction points to eliminate the defects of the fabric caused by yarn reduction, thereby ensuring various properties of the composite material. At the same time, the method has extremely high designability, simple operation and wide adaptability, so the accuracy of the complex shape of the three-dimensional fabric can be guaranteed.

[0052] Example 2

[0053] The three-dimensional four-step method is used to weave Figure 1 The thin-walled conical part shown has an inner diameter of φ190mm, a height of 200mm, and a wall thickness of 5mm. The weaving starts with the cross section at the large end as the reference section, and the weaving direction is along the height direction of the cylinder. Figure 1 Indicated by the direction of the arrow.

[0054] This embodiment adopts a three-dimensional four-way braiding structure and uses T300-3K fiber for braiding. The dynamic yarn has 7 strands, the mother-direction flower knot is 95mm / 10 flowers, the circumferential flower knot is 70mm / 10 flowers, the fiber volume fraction is 50.0%, and the number of dynamic yarns required for the reference cross-section design is 1575, which are arranged in 9 layers and 182 rows along the ring.

[0055] According to the structural design, in order to meet the requirements of the appearance of thin-walled conical parts, 4 columns of yarn need to be reduced for each knitting cycle. According to the movement law of the three-dimensional four-step method, the yarn is reduced in groups of 2 columns, that is, the yarn is reduced in two yarn reduction units. Two positions are selected symmetrically on the ring to perform the column and yarn reduction operation. One of the positions (a yarn reduction unit) is taken as an example to illustrate the method of reducing columns and yarns by pre-dispersing the yarn reduction points of the present invention. The method of pre-dispersing the yarn reduction points and reducing columns and yarns is divided into the following two methods:

[0056] ①Pre-reduction formula:

[0057] (1) See Figure 8 , Figure 8 The figure is a schematic diagram of the arrangement of spindles at a certain point in the ring after a cycle is completed. After finding two weaving cycles, the spindles will move to two adjacent columns, that is, Figure 8 For the colored spindles in the figure, the yarn thinning operation is carried out at this time, and each yarn in the diagram is completely removed according to the design requirements.

[0058] (2) After two weaving cycles, the spindles that have undergone the yarn reduction operation are Fig. 9 As shown, they are arranged into two adjacent rows. At this time, the spindles in these two rows are empty spindles. Fig.10 After finishing the yarn, Fig.11 , the knitting yarn is reduced by two rows. In this way, the fabric is pre-dispersed and the yarn reduction point is reduced and the yarn reduction operation is realized. Repeat the above steps until the knitting is completed, and the result is Figure 1 The thin-walled conical part with uniform wall thickness is shown.

[0059] ②Pre-reduction type:

[0060] (1) See Fig.12 , Fig.12 The figure is a schematic diagram of the arrangement of spindles at a certain point in the ring after a cycle is completed. After finding two weaving cycles, the spindles will move to the adjacent four columns, that is, Fig.12 For the colored spindles in the diagram, the yarn thinning operation is carried out at this time. According to the design requirements, the number of yarn strands of one group shown in the figure is reduced from 7 to 3, and the number of yarn strands of the other group is reduced from 7 to 4.

[0061] (2) After two weaving cycles, the spindles that have undergone the thinning operation are Fig.13 As shown, the yarns are arranged in four adjacent columns 1, 2, 3, and 4 (i.e., one yarn reduction unit). Figure 3 The method shown is used to merge the yarns on the 3rd and 4th columns of spindles, that is, the yarns on the 1st and 2nd columns of spindles with the same motion law are merged respectively, that is, the 1st and 3rd columns are merged at the same layer, and the 2nd and 4th columns are merged at the same layer. Fig.14 As shown in the figure. At this time, the yarn has lost 2 rows. Fig.15 As shown. In this way, the pre-dispersed yarn reduction point reduction and yarn reduction operation of the fabric is realized. Repeat the above steps until the weaving is completed and obtain Figure 1 The thin-walled conical part with uniform wall thickness is shown.

Claims

1. A yarn reduction method for three-dimensional woven fabrics, characterized in that: In the three-dimensional four-step weaving process, a yarn reduction unit is taken as a reference. The yarn reduction unit is two rows of odd spindles and two rows of even spindles arranged adjacent to each other after 0 to 4 standard cycles. Within 0 to 4 standard cycles, the yarn reduction points in the yarn reduction unit are subjected to yarn reduction operations in a dispersed state, and yarn doubling operations are performed in a gathered state.

2. The yarn reduction method according to claim 1, characterized in that: The three-dimensional woven fabric is a three-dimensional fabric formed by a three-dimensional four-step weaving method, and the cross section of the three-dimensional fabric is I-shaped, T-shaped, V-shaped, U-shaped or ring-shaped.

3. The yarn reduction method according to claim 1, characterized in that: The yarn reducing units are arranged in plurality according to the shape of the fabric.

4. The yarn reduction method according to claim 1, characterized in that: The yarn reduction method is used for reducing layers and / or columns.

5. The yarn reduction method according to any one of claims 1 to 4, characterized in that: include: A delayed dispersion yarn reduction step and a pre-dispersion yarn reduction step; (1) During the overall forming process of the three-dimensional woven fabric, after a standard cycle is completed, the yarns on the two rows of odd-numbered spindles that need to be reduced in the yarn reduction unit are merged into one of the spindles, and the yarns on the two rows of even-numbered spindles that need to be reduced are merged into one of the spindles to form two rows of roving spindles. After continuing to weave 2 to 4 standard cycles, the yarns on the roving spindles in a dispersed state are thinned to complete a delayed dispersed yarn reduction; (2) During the overall forming process of the three-dimensional woven fabric, after a standard cycle is completed, the yarns on the spindles in a dispersed state that need to be reduced are thinned to form fine yarn spindles; after continuing to weave 2 to 4 standard cycles, the fine yarn spindles are arranged into a yarn reduction unit, and the yarns on the two rows of odd-numbered fine yarn spindles in the yarn reduction unit are merged into one of the spindles, and the yarns on the two rows of even-numbered fine yarn spindles are merged into one of the spindles, completing a pre-dispersed yarn reduction.

6. The yarn reduction method according to claim 5, characterized in that: Step (1) comprises: (1.1) The yarn reduction unit is composed of two rows of odd-numbered spindles and two rows of even-numbered spindles arranged adjacently. After a standard cycle is completed, the yarns on the two rows of odd-numbered spindles are merged in the same layer onto one of the spindles, and the yarns on the two rows of even-numbered spindles are merged in the same layer onto one of the spindles to form two rows of roving spindles. After weaving for 2 to 4 standard cycles, the yarns on the roving spindles in a dispersed state are thinned to complete a delayed dispersed row reduction and yarn reduction. (1.2) The yarn reduction unit is composed of two layers of odd-numbered spindles and two layers of even-numbered spindles arranged adjacent to each other. After a standard cycle is completed, the yarns on the two layers of odd-numbered spindles are merged in the same column onto one of the spindles, and the yarns on the two layers of even-numbered spindles are merged in the same column onto one of the spindles to form two layers of coarse yarn spindles. After weaving for 2 to 4 standard cycles, the yarns on the dispersed coarse yarn spindles are thinned to complete a delayed dispersed layer and yarn reduction.

7. The yarn reduction method according to claim 5, characterized in that: Step (2) comprises: (2.1) The yarns on the spindles in a dispersed state that need to be reduced are thinned to form fine yarn spindles; after continuing to weave 2 to 4 standard cycles, the fine yarn spindles are arranged into a yarn reduction unit, wherein the yarn reduction unit is composed of two columns of odd-numbered spindles and two columns of even-numbered spindles arranged adjacently, and the yarns on the two columns of odd-numbered spindles in the yarn reduction unit are merged into one of the spindles, and the yarns on the two columns of even-numbered spindles are merged into one of the spindles, thereby completing a pre-dispersed column reduction and yarn reduction; (2.2) The yarns on the spindles that need to be reduced are thinned to form fine yarn spindles; after continuing to weave 2 to 4 standard cycles, the fine yarn spindles are arranged into a yarn reduction unit, and the yarn reduction unit is composed of two layers of odd-numbered spindles and two layers of even-numbered spindles arranged adjacent to each other, and the yarns on the two layers of odd-numbered fine yarn spindles in the yarn reduction unit are merged into one of the spindles, and the yarns on the two layers of even-numbered fine yarn spindles are merged into one of the spindles, thereby completing a pre-dispersed layer reduction and yarn reduction.

8. The yarn reduction method according to claim 5, characterized in that: In step (1), the thinning operation is to remove any number of yarns on the spindle.

9. The yarn reduction method according to claim 5, characterized in that: In step (2), the thinning operation is to remove any number of yarns on the spindle.

10. The yarn reduction method according to claim 5, characterized in that: The yarn reduction unit is subjected to full or partial yarn reduction.

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