Preparation method of variable-section three-dimensional multi-directional preform and variable-section three-dimensional preform

Abstract

The present invention provides a method for preparing a variable-section three-dimensional multidirectional preform and a variable-section three-dimensional preform, belonging to the field of textile technology. The present invention realizes the connection of yarns between different gradients by horizontally moving the outer yarns of adjacent gradients, thereby realizing the change of the cross-sectional size along the length direction or the height direction. The method is not limited by the change of the number of yarn strands, and the cross-sectional size can be varied in a wide range; at the same time, horizontal yarn shifting reduces the difficulty of yarn shifting for the operator, and improves the weaving efficiency and weaving quality; the variable thickness preform prepared by the present invention has strong yarn connection between different thicknesses, so the preform has good integrity.

Description

Technical Field

[0001] The invention relates to the technical field of three-dimensional preform preparation, and in particular to a method for preparing a variable-cross-section three-dimensional multi-directional preform and a variable-cross-section three-dimensional preform. Background Art

[0002] Three-dimensional multi-directional preforms have been widely used in aerospace, rail transportation and other fields in recent years due to their good structural integrity and high fiber volume content. With the continuous expansion of its application fields, the cross-sectional shape of the preform has also developed from simple, equal-wall thickness sections to complex variable cross-sectional shapes. Variable cross-sectional preforms are generally divided into: preforms with cross-sectional dimensions that change along the weaving length direction, preforms with cross-sectional dimensions that change along the height direction, and preforms with the above two changes combined.

[0003] Chinese patent CN102938019B discloses a three-dimensional multi-directional braided fabric net size contoured yarn reduction weaving method for composite materials and Chinese patent CN100491618C discloses a three-dimensional weaving method for variable cross-section preformed parts and parts thereof, both of which achieve continuous changes in the cross-sectional dimensions of the preform along the weaving length direction by changing the number of yarns during the weaving process. Chinese patent CN108998888B discloses a three-dimensional weaving method for variable cross-sectional preformed parts with row-column transformation and parts thereof, which achieves the overall weaving of a special-shaped preform with a variable cross-sectional dimension along the length direction by mutual transformation between rows and columns under the premise that the total number of fibers remains unchanged.

[0004] Chinese patent application number CN201510195792.7 discloses a method for preparing a variable thickness layered structure fabric. This method achieves a change in the cross-sectional size of the preform along the height direction by thinning or thickening the surface yarn bundles. However, the change in the cross-sectional size of the preform is limited by the change in the number of yarn strands, and the size can be changed in a small range. Chinese patent CN110318140A discloses a weaving method for realizing four-step integrated weaving of unequal-layer fabrics. This method achieves the overall forming of unequal-layer fabrics by cross-shifting yarns between two unequal-layer yarn arrays. However, cross-shifting yarns between different layers is complicated to operate, has low weaving efficiency, and is prone to yarn shifting errors, which affects product quality. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a three-dimensional multi-directional preform with a variable cross-section and a preparation method thereof.

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

[0007] A method for preparing a variable-cross-section three-dimensional multi-directional preform comprises the following steps connected in sequence:

[0008] (1) Preform area division and yarn array distribution: A virtual plane is used to divide the preform into two parts, the first gradient and the second gradient. The yarn array corresponding to the first gradient is M layers and N columns, and the yarn array corresponding to the second gradient is M' layers and N' columns, where M'-M = 2X, and X is a natural number;

[0009] (2) The first yarn movement: in the M-layer yarn array, except for the 1st and Mth layers which are fixed, the remaining layers move one spindle position at intervals along the layer direction in the order of one layer to the left and one layer to the right; in the M'-layer yarn array, except for the 1st and M'th layers which are fixed, the remaining layers move one spindle position in accordance with the movement law consistent with the M-layer yarn array, thus forming two yarn arrays, the M-layer N+1 column and the M'-layer N'+1 column;

[0010] (3) The first gradient inter-yarn shifting: the yarns on the N+1th column in the M-layer yarn array are moved in parallel to the empty positions in the second column in the M'-layer yarn array, the yarns on the first column corresponding to the number of layers of the M'-layer yarn array are moved in parallel to the empty positions in the Nth column in the M-layer yarn array, and the remaining yarns on the first column in the M'-layer yarn array are moved to the empty positions in the second column of the same yarn array. After the yarn shifting is completed, an M-layer N-column and an M'-layer N'-column yarn array are formed; the empty positions are the empty yarn positions generated after the first yarn movement;

[0011] (4) Second yarn movement: except for the first column in the M-layer yarn array and the N'th column in the M'-layer yarn array, which are fixed, the rest of the yarns move one spindle position at a time in the order of one column upward and one column downward;

[0012] (5) The third yarn movement: the M-layer yarn array and the M'-layer yarn array move in opposite directions according to the same movement rule as step (2), forming two yarn arrays, M-layer N+1 column and M'-layer N'+1 column;

[0013] (6) Second gradient inter-yarn shifting: moving the yarns on the N+1th column in the M-layer yarn array and the yarns on the 1st column in the M'-layer yarn array according to the same motion rule as step (3);

[0014] (7) The fourth yarn movement: the M-layer yarn array and the M'-layer yarn array move in opposite directions according to the same movement rules as step (4);

[0015] (8) Tightening movement: The tightening mechanism tightens the yarn interlacing point to the required height;

[0016] (9) Repeat the process steps (2) to (8) until the required length is obtained to obtain a variable cross-section three-dimensional multi-directional preform.

[0017] Furthermore, in step (1), a plurality of virtual planes are used to divide the preform into a plurality of gradient parts, and the yarn movement rules of two adjacent gradient parts are the same as steps (2) to (8), except that in steps (2) and (5), the number of columns of the middle part is increased by two after the first yarn movement.

[0018] By adopting the above technical scheme, the cross-sectional shape of the prepared preform can be continuously changed, and the cross-sectional shape of the preform can be flexibly divided according to the requirements of the profiling accuracy of the preform, and the operability is strong. For preforms with complex cross-sectional shapes such as "T" shape, "I" shape, "π" shape, etc., the preparation method of the present invention is used, the number of yarn movement steps is small, the yarn moving movement law is simple, and the production efficiency can be significantly improved.

[0019] Furthermore, in step (1), the yarns of the 1st layer and the Mth layer in the M-layer yarn array are spaced apart by one row and staggered up and down, the yarns of the 1st layer and the M'th layer in the M'-layer yarn array are spaced apart by one row and staggered up and down, the yarns of the 1st layer in the M-layer yarn array and the yarns of the 1st layer in the M'-layer yarn array are spaced apart by one row; the 1st layer and the Mth layer in the 1st column in the M-layer yarn array have no yarn, and the 1st layer and the M'th layer in the N'th column in the M'-layer yarn array have no yarn.

[0020] Furthermore, in step (1), the yarns in the 1st column of the M-layer yarn array are arranged one layer apart, and the yarns in the N'th column of the M'-layer yarn array are arranged one layer apart, and the yarns in the 1st column of the M-layer yarn array and the yarns in the N'th column of the M'-layer yarn array are not on the same layer.

[0021] Furthermore, in step (2), the layer with yarn in the first column of the M-layer yarn array moves to the right, and the layer without yarn moves to the left; the layer with yarn in the N'th column of the M'-layer yarn array moves to the left, and the layer without yarn moves to the right.

[0022] Further, in step (4), the first layer of the M-layer yarn array has columns with yarns moving downward, and the columns without yarns moving upward; the first layer of the M'-layer yarn array has columns with yarns moving downward, and the columns without yarns moving upward.

[0023] Furthermore, M and M' are both odd numbers or both even numbers.

[0024] Furthermore, N and N' are odd numbers or even numbers.

[0025] A three-dimensional multi-directional preform with a variable cross-section is made by any one of the above-mentioned preparation methods.

[0026] The beneficial effects of the present invention are as follows: the present invention improves upon the existing four-step weaving technology, and achieves connection between yarns of different gradients by horizontally moving the outer yarns of adjacent gradients, thereby achieving changes in cross-sectional dimensions along the length direction or the height direction. This method is not limited by changes in the number of yarn strands, and the cross-sectional dimensions can vary over a wide range; at the same time, horizontal yarn movement reduces the difficulty of yarn movement for the operator, and improves weaving efficiency and weaving quality; the variable thickness preform prepared by the present invention has strong connectivity between yarns of different thicknesses, and therefore the preform has good integrity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the appearance of the preform of Example 1 of the present invention

[0028] Figure 2 This is a schematic diagram of the initial arrangement of yarns of the preform of Example 1 of the present invention.

[0029] Figure 3 This is a schematic diagram of the first yarn movement of the preform in Example 1 of the present invention.

[0030] Figure 4 This is a schematic diagram of the first gradient inter-yarn shifting of the preform in Example 1 of the present invention.

[0031] Figure 5 This is a schematic diagram of the yarn arrangement after the first gradient inter-yarn shifting of the preform in Example 1 of the present invention.

[0032] Figure 6 This is a schematic diagram of the second yarn movement of the preform in Example 1 of the present invention.

[0033] Figure 7 This is a schematic diagram of the third yarn movement of the preform in Example 1 of the present invention.

[0034] Figure 8 This is a schematic diagram of the second gradient inter-yarn shifting of the preform in Example 1 of the present invention.

[0035] Fig. 9 This is a schematic diagram of the yarn arrangement after the second gradient inter-yarn shifting of the preform in Example 1 of the present invention.

[0036] Fig.10 This is a schematic diagram of the fourth yarn movement of the preform in Example 1 of the present invention.

[0037] Fig.11 This is a schematic diagram of the appearance of the preform of Example 2 of the present invention.

[0038] Fig.12 This is a schematic diagram of the initial arrangement of yarns in the preform of Example 2 of the present invention.

[0039] Fig.13 This is a schematic diagram of the first yarn movement of the preform in Example 2 of the present invention.

[0040] Fig.14 This is a schematic diagram of the first gradient inter-yarn shifting of the preform in Example 2 of the present invention.

[0041] Fig.15 This is a schematic diagram of the yarn arrangement after the first gradient inter-yarn shifting of the preform in Example 2 of the present invention.

[0042] Fig.16 This is a schematic diagram of the second yarn movement of the preform in Example 1 of the present invention.

[0043] Fig.17 This is a schematic diagram of the third yarn movement of the preform in Example 2 of the present invention.

[0044] Fig.18 This is a schematic diagram of the second gradient inter-yarn shifting of the preform in Example 2 of the present invention.

[0045] Fig.19 This is a schematic diagram of the yarn arrangement after the second gradient inter-yarn shifting of the preform in Example 2 of the present invention.

[0046] Fig. 20 This is a schematic diagram of the fourth yarn movement of the preform in Example 2 of the present invention. DETAILED DESCRIPTION

[0047] 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.

[0048] Example 1

[0049] This embodiment provides a cross-sectional shape such as Figure 2 The variable cross-section three-dimensional multi-directional preform shown in the figure has a preparation method comprising the following steps:

[0050] (1) Preform area division and yarn array distribution: Figure 1 As shown, the virtual plane 1-1 divides the preform into two parts, A and B. The number of yarn arrays corresponding to part A is 8 layers and 5 columns, and the number of yarn arrays corresponding to part B is 10 layers and 4 columns. The initial arrangement of the yarns in parts A and B is as follows Figure 2 shown.

[0051] (2) The first yarn movement: Figure 3As shown. In the 8-layer 5-column yarn array, the 1st and 8th layers are stationary, the 2nd, 4th, and 6th layers of yarn move one spindle position to the right along the layer direction, and the 3rd, 5th, and 7th layers of yarn move one spindle position to the left along the layer direction, forming an 8-layer 6-column yarn array; in the 10-layer 4-column yarn array, the 1st and 10th layers are stationary, the 2nd, 4th, 6th, and 8th layers of yarn move one spindle position to the right along the layer direction, and the 3rd, 5th, 7th, and 9th layers of yarn move one spindle position to the left along the layer direction, forming a 10-layer 5-column yarn array.

[0052] (3) The first gradient yarn shift: Figure 4 As shown, the yarns on the 2nd, 4th and 6th layers of the 6th column in the 8-layer 6-column yarn array are moved in parallel to the 2nd, 4th and 6th empty layers of the 2nd column in the 10-layer yarn array, the yarns on the 3rd, 5th and 7th layers of the 1st column in the 10-layer 5-column yarn array are moved in parallel to the 3rd, 5th and 7th empty layers of the 5th column in the 8-layer 6-column yarn array, and the yarns on the 9th layer of the 1st column in the 10-layer 5-column yarn array are moved to the 8th empty layer of the 2nd column. The yarn arrangement after yarn movement is shown in FIG. Figure 5 .

[0053] (4) Second yarn movement: Figure 6 As shown. In the 8-layer 5-column yarn array, the 2nd and 4th columns move down by one spindle position, and the 3rd and 5th columns move up by one spindle position; in the 10-layer 4-column yarn array, the 1st and 3rd columns move down by one spindle position, and the 2nd column moves up by one spindle position.

[0054] (5) The third yarn movement: Figure 7 As shown. In the 8-layer 5-column yarn array, the 1st and 8th layers are stationary, the 2nd, 4th, and 6th layers of yarn move one spindle position to the left along the layer direction, and the 3rd, 5th, and 7th layers of yarn move one spindle position to the right along the layer direction, forming an 8-layer 6-column yarn array; in the 10-layer 4-column yarn array, the 1st and 10th layers are stationary, the 2nd, 4th, 6th, and 8th layers of yarn move one spindle position to the left along the layer direction, and the 3rd, 5th, 7th, and 9th layers of yarn move one spindle position to the right along the layer direction, forming a 10-layer 5-column yarn array.

[0055] (6) Second gradient yarn shift: Figure 8 As shown, the yarns on the 3rd, 5th and 7th layers of the 6th column in the 8-layer 6-column yarn array are moved in parallel to the empty positions of the 3rd, 5th and 7th layers of the 2nd column in the 10-layer yarn array, the yarns on the 2nd, 4th and 6th layers of the 1st column in the 10-layer 5-column yarn array are moved in parallel to the empty positions of the 2nd, 4th and 6th layers of the 5th column in the 8-layer yarn array, and the yarns on the 8th layer of the 1st column in the 10-layer yarn array are moved to the empty position of the 9th layer of the 2nd column. The yarn arrangement after yarn movement is shown in FIG. Fig. 9 .

[0056] (7) The fourth yarn movement: Fig.10 As shown in the figure, the 2nd and 4th columns of the 8-layer 5-column yarn array move one spindle position upward, and the 3rd and 5th columns move one spindle position downward; the 1st and 3rd columns of the 10-layer 4-column yarn array move one spindle position upward, and the 2nd column moves one spindle position downward.

[0057] (8) Tightening movement: The tightening mechanism tightens the yarn interlacing points to the required height.

[0058] (9) Repeat the process steps (2) to (8) until the desired length is obtained, and the cross section is as follows: Figure 1 The preform shown.

[0059] Example 2

[0060] This embodiment provides a cross-sectional shape such as Fig.11 The variable cross-section three-dimensional multi-directional preform shown in the figure has a preparation method comprising the following steps:

[0061] (1) Preform area division and yarn array distribution: Fig.11 As shown, virtual planes 2-1 and 2-2 divide the preform into three parts: A1, B1, and C1. The yarn array numbers of the three parts A1, B1, and C1 are 5 layers and 4 columns, 7 layers and 4 columns, and 5 layers and 4 columns, respectively. The initial arrangement of the yarns is as follows: Fig.12 shown.

[0062] (2) The first yarn movement: Fig.13 As shown, in the 6-layer 4-column yarn array of part A1 and part C1, the 1st and 5th layers remain stationary, the 2nd and 4th layers of yarn move one spindle position to the left along the layer direction, and the 3rd layer of yarn moves one spindle position to the right along the layer direction, forming a yarn array of 5 layers and 5 columns; in the 7-layer 4-column yarn array of part B1, the 1st and 7th layers remain stationary, the 2nd, 4th and 6th layers of yarn move one spindle position to the left along the layer direction, and the 3rd and 5th layers of yarn move one spindle position to the right along the layer direction, forming a yarn array of 7 layers and 6 columns.

[0063] (3) The first gradient yarn shift: Fig.14As shown, the yarn on the 3rd layer of the 5th column in the 5-layer 5-column yarn array of part A1 is moved in parallel to the empty position of the 5th layer in the 2nd column in the 7-layer 6-column yarn array of part B1, the yarn on the 4th and 6th layers in the 1st column in the 7-layer 6-column yarn array of part B1 is moved in parallel to the empty positions of the 2nd and 4th layers in the 4th column in the 5-layer 5-column yarn array of part A1, and the yarn on the 2nd layer in the 1st column in the 7-layer 6-column yarn array of part B1 is moved to the empty position of the 3rd layer in the 2nd column; at the same time , move the yarns on the 2nd and 4th layers of the 1st column in the 5-layer 5-column yarn array of part C1 in parallel to the 4th and 6th empty layers of the 5th column in the 7-layer 6-column yarn array of part B1, move the yarns on the 5th layer of the 6th column in the 7-layer 6-column yarn array of part B1 in parallel to the 3rd empty layer of the 2nd column in the 5-layer 5-column yarn array of part C1, move the yarns on the 3rd layer of the 6th column in the 7-layer 6-column yarn array to the 2nd empty layer of the 5th column, and the yarn arrangement after yarn movement is shown in FIG. Fig.15 .

[0064] (4) Second yarn movement: Fig.16 As shown, the 3rd column in the 5-layer 4-column yarn array of part A1 moves downward by one spindle position, and the 2nd and 4th columns move upward by one spindle position; the 1st and 3rd columns in the 7-layer 4-column yarn array of part B1 move downward by one spindle position, and the 2nd and 4th columns move upward by one spindle position; the 1st and 3rd columns in the 5-layer 4-column yarn array of part C1 move downward by one spindle position, and the 2nd column moves upward by one spindle position.

[0065] (5) The third yarn movement: Fig.17 As shown, in the 5-layer 4-column yarn array of part A1 and part C1, the 1st and 5th layers remain stationary, the 2nd and 4th layers of yarn move one spindle position to the right along the layer direction, and the 3rd layer of yarn moves one spindle position to the left along the layer direction, forming a yarn array of 5 layers and 5 columns; in the 7-layer 4-column yarn array of part B1, the 1st and 7th layers remain stationary, the 2nd, 4th and 6th layers of yarn move one spindle position to the right along the layer direction, and the 3rd and 5th layers of yarn move one spindle position to the left along the layer direction, forming a yarn array of 7 layers and 6 columns.

[0066] (6) Second gradient yarn shift: Fig.18As shown, the yarns on the 2nd and 4th layers of the 5th column in the 5-layer, 5-column yarn array of part A1 are moved in parallel to the empty positions of the 4th and 6th layers of the 2nd column in the 7-layer, 6-column yarn array of part B1, the yarns on the 5th layer of the 1st column in the 7-layer, 6-column yarn array of part B1 are moved in parallel to the empty positions of the 3rd layer of the 4th column in the 5-layer, 5-column yarn array of part A1, and the yarns on the 3rd layer of the 1st column in the 7-layer, 6-column yarn array of part B1 are moved to the empty positions of the 2nd layer of the 2nd column; at the same time, The yarn on the 3rd layer of the 1st column in the 5-layer 5-column yarn array of part C1 is moved in parallel to the 5th layer empty space of the 5th column in the 7-layer 6-column yarn array of part B1. The yarn on the 4th and 6th layers of the 6th column in the 7-layer 6-column yarn array of part B1 is moved in parallel to the 2nd and 4th layers empty space of the 2nd column in the 5-layer 5-column yarn array of part C1. The yarn on the 2nd layer of the 6th column in the 7-layer 6-column yarn array of part B1 is moved to the 3rd layer empty space of the 5th column. The yarn arrangement after yarn movement is shown in FIG. Fig.19 .

[0067] (7) The fourth yarn movement: Fig. 20 As shown, the 2nd and 4th columns of the 5-layer 4-column yarn array of part A1 move downward by one spindle position, and the 3rd column moves upward by one spindle position; the 2nd and 4th columns of the 7-layer 4-column yarn array of part B1 move downward by one spindle position, and the 1st and 3rd columns move upward by one spindle position; the 2nd column of the 5-layer 4-column yarn array of part C1 moves downward by one spindle position, and the 1st and 3rd columns move upward by one spindle position.

[0068] (8) Tightening movement: The tightening mechanism tightens the yarn interlacing points to the required height.

[0069] (9) Repeat the process steps (2) to (8) until the desired length is obtained, and the cross section is as follows: Fig.11 The preform shown.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications are also within the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional multi-directional preform with a variable cross-section, characterized in that: The method comprises the following steps, which are connected in sequence: (1) Preform area division and yarn array distribution: A virtual plane is used to divide the preform into the first gradient and the second The first gradient has two parts, the yarn array corresponding to the first gradient is M layers and N columns, and the yarn array corresponding to the second gradient is M' layers and N' columns, where M'-M=2X, and X is a natural number; (2) The first yarn movement: In the M-layer yarn array, except for the first and Mth layers, which are fixed, the remaining layers move along the layer direction according to One layer moves to the left and one layer moves to the right in sequence, one spindle position at a time; in the M'-layer yarn array, except for the 1st layer and the M'-layer which are fixed, the remaining layers move one spindle position according to the same movement law as the M-layer yarn array, thus forming two yarn arrays, the M-layer N+1 column and the M'-layer N'+1 column; (3) The first gradient inter-yarn shift: the yarn on the N+1th column in the M-layer yarn array is moved parallel to the M'-layer yarn array. The yarns on the first column of the M'-layer yarn array corresponding to the number of layers of the M-layer yarn array are moved in parallel to the empty positions of the Nth column in the M-layer yarn array, and the remaining yarns on the first column of the M'-layer yarn array are moved to the empty positions of the second column of the same yarn array, and after the yarn moving is completed, an M-layer N-column and an M'-layer N'-column yarn array are formed; the empty positions are the empty yarn positions generated after the first yarn movement; (4) Second yarn movement: The entire yarn array except the first column in the M-layer yarn array and the first column in the M'-layer yarn array Except for the N' row which is fixed, the other yarns move one spindle position at a time in the order of one row upward and one row downward; (5) The third yarn movement: The M-layer yarn array and the M'-layer yarn array follow the same movement rules as step (2). Move in the opposite direction to form two yarn arrays: M layers and N+1 rows and M' layers and N'+1 rows; (6) Second gradient inter-yarn shifting: Move the N+1th column of the M-layer yarn array according to the same motion rule as step (3). The yarns of and the yarns on the first column in the M'-layer yarn array; (7) The fourth yarn movement: The M-layer yarn array and the M'-layer yarn array follow the same movement rules as step (4). Towards movement; (8) Tightening movement: The tightening mechanism tightens the yarn interlacing point to the required height; (9) Repeat steps (2) to (8) until the required length is reached to obtain a variable cross-section three-dimensional multi-directional preform.

2. The method for preparing a variable cross-section three-dimensional multi-directional preform according to claim 1, characterized in that: In step In (1), multiple virtual planes are used to divide the preform into several gradient parts. The yarn motion law of two adjacent gradient parts is Except that in step (2) and step (5), the number of rows in the middle part after the yarn movement increases by two, the remaining steps are the same as step (2) to step (5). (8)Same.

3. The method for preparing a variable cross-section three-dimensional multi-directional preform according to claim 1, characterized in that: In step (1), the yarns of the 1st layer and the Mth layer in the M-layer yarn array are spaced apart by one row and staggered up and down, the yarns of the 1st layer and the M'th layer in the M'-layer yarn array are spaced apart by one row and staggered up and down, the yarns of the 1st layer in the M-layer yarn array and the yarns of the 1st layer in the M'-layer yarn array are spaced apart by one row; the 1st layer and the Mth layer in the 1st column of the M-layer yarn array have no yarns, and the 1st layer and the M'th layer in the N'th column of the M'-layer yarn array have no yarns.

4. The method for preparing a variable cross-section three-dimensional multi-directional preform according to claim 1, characterized in that: In step In (1), the yarns in the first column of the M-layer yarn array are arranged one layer apart, and the yarns in the N'th column of the M'-layer yarn array are arranged one layer apart, and the yarns in the first column of the M-layer yarn array and the yarns in the N'th column of the M'-layer yarn array are not on the same layer.

5. The method for preparing a variable cross-section three-dimensional multi-directional preform according to claim 1, characterized in that: In step In (2), the layer with yarn in the first column of the M-layer yarn array moves to the right, and the layer without yarn moves to the left; the layer with yarn in the N'th column of the M'-layer yarn array moves to the left, and the layer without yarn moves to the right.

6. The method for preparing a variable cross-section three-dimensional multi-directional preform according to claim 1, characterized in that: In step (4), the first layer of the M-layer yarn array has a row of yarns that moves downward, and the row of yarns that does not move upward; the M'-layer yarn array The columns with yarn in the first layer move downward, and the columns without yarn move upward.

7. The method for preparing a variable cross-section three-dimensional multi-directional preform according to claim 1, characterized in that: M and M' Both are odd numbers or both are even numbers.

8. The method for preparing a variable cross-section three-dimensional multi-directional preform according to claim 1, characterized in that: N and N' Is an odd or even number.

9. A three-dimensional multi-directional preform with a variable cross-section, characterized in that: A preparation method according to any one of claims 1 to 8 Made in France.

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