Whole profiling weaving method for warp insertion 2.5 D woven fabric with through holes

Abstract

The invention relates to an overall profiling weaving method for warp insertion 2.5 D woven fabric with through holes. The overall profiling weaving method comprises the following steps that S1, the number of warp columns for yarn moving is determined; s2, the yarn moving times and the yarn moving number are designed; s3, after the opening motion, moving yarns according to the yarn moving scheme and changing reeds, and executing the yarn moving and reed changing operation once every other weft; after each time of yarn moving, adding the same kind of yarn at the position of the vacant yarn of the yarn moving column to replace the moved-out yarn to participate in subsequent weaving; s4, after all the yarns in the yarn moving column are moved away, the added yarns are taken down from the creel and hung outside the prefabricated body, a cylindrical core mold is placed at the position of the center line of the hole, and a through hole structure formed by wrapping the yarns around the hole layer by layer is formed; s5, yarn is introduced from the outside of the fabric again to fill the gap of the yarn moving column; when the yarn moves back to the yarn moving column, the yarn at the corresponding position is led out firstly, the moved-back yarn replaces the led-out yarn to return to the initial position, the yarn on the outer surface of the prefabricated body is cut off after the yarn moves back, and operation is finished. The mechanical property of the material is improved through layer-by-layer and multi-time yarn moving and yarn adding operation.

Description

Technical Field

[0001] The invention belongs to the technical field of three-dimensional integral weaving of composite material preforms, and in particular relates to an integral contour weaving method of a 2.5D woven fabric with through holes and a lining warp. Background Art

[0002] Three-dimensional woven composite materials have the characteristics of good structural integrity, strong designability, and near-net forming ability of special-shaped components. Among them, the multi-layer binding warp yarns in the lining warp 2.5D woven fabric as a reinforcement bundle multiple layers of lining warp yarns and weft yarns to form a non-layered structure. The mechanical properties retention rate of the composite material after mechanical processing in the thickness direction is high, and it is expected to replace metal materials for main load-bearing components. Although the contoured overall forming ability of three-dimensional woven composite materials greatly reduces the number of parts to be assembled, the necessary assembly connection is still inevitable. The hole opening processing in the screw connection, riveting, rubber screw, and rubber rivet connection method destroys the fiber reinforced structure and greatly reduces the bearing capacity of the composite material components. Therefore, it is necessary to propose a hole-containing weaving method that maximizes the retention of the fiber reinforced structure and improves the retention rate of the mechanical properties of the material.

[0003] Hole-containing weaving is a special case of material cross-section change. Some patents have conducted relevant research on the design method of three-dimensional woven / woven variable-section structures. In 2004, the patent "A method for weaving a variable-section three-dimensional fabric for composite materials (CN1540052A)" proposed to gradually reduce the number of warp and weft yarns interwoven by the binding yarns, so that the warp and weft yarns not interwoven by the binding yarns float outside the fabric, so as to achieve a gradual decrease in the thickness of the three-dimensional orthogonal woven preform. In 2005, the patent "Three-dimensional weaving method for variable-section preforms and their products (CN1651627A)" proposed to complete the overall three-dimensional weaving of variable-section preforms by moving the weaving yarns, folding, thinning or increasing the yarns, dividing the strands and moving them again. In 2006, the patent "A three-dimensional overall weaving method that can fold the weaving forming direction (CN1827888A)" proposed to gradually reduce the number of yarn columns participating in the weaving to achieve a gradual decrease in the cross-sectional size. In 2006, the patent "A three-dimensional integral weaving method for multi-directional preformed parts (CN1827887A)" proposed that when weaving in the first forming direction to the intersection with the contour line of the second forming direction, the yarn required for weaving in the second forming direction is reserved, and the same number of yarns are reserved for continued weaving in the first forming direction, thereby realizing the integral weaving of the multi-directional preformed parts. In 2008, the patent "Weaving method for 2.5-dimensional integrally woven multi-channel tube fabric (CN101503838A)" proposed to move the warp yarn between the warp yarn columns so that the yarn addition and subtraction points are dispersed to multiple warp yarn columns, thereby improving the hole phenomenon caused by the addition and subtraction of the entire column. In 2008, the patent "Multi-directional preformed braided parts and their three-dimensional integral weaving method (CN101586285A)" proposed to use the yarn lead-out end of the yarn introduction area in the first forming direction and the reserved end yarn of the yarn addition area as the braiding yarn in the second forming direction, thereby realizing the integral three-dimensional weaving of the multi-directional preformed parts. In 2010, Yu Jianyong et al. proposed in the patent "Net shape preparation method of variable cross-section three-dimensional woven preform (CN102011269A)" to reduce one or more columns, one or more rows of yarns inside the preform, and gradually fill the vacancies of the reduced yarns with the outer yarns adjacent to the reduced yarn positions by translation, so as to reduce the width and thickness of the preform cross section. In 2011, the patent "Insertion weaving method for three-dimensional woven special-shaped preform (CN102051763A)" proposed to move the yarns and outer yarns on the m-column or n-row (m, n≥2) inser spindles outward by m columns or n rows, and to perform inser when there is no yarn on the inser spindle. In 2012, the patent "Weaving method of 2.5-dimensional and 2.5-dimensional derivative structure combined unit body (CN103014998A)" proposed to combine adjacent layers of warp yarns or split double yarns into two layers of yarns, so as to reduce or increase the number of warp and weft layers, thereby achieving changes in fabric thickness.In 2013, the patent "Method for reducing and adding yarns for three-dimensional variable cross-sectional area woven preforms based on active yarn carriers (CN103437064A)" proposed to increase or decrease the number of active yarn carriers along the closed curve of the cross-sectional edge to achieve the net size weaving of three-dimensional variable cross-sectional area preforms. In 2013, the patent "A woven 2D+2.5D contoured fabric combination fabric and molding method (CN103266391A)" proposed to gradually reduce the edge warp yarns to achieve the contour molding of barrel-shaped variable cross-sectional fabrics. In 2015, Zhu Jianxun et al. proposed in the patent "A method for integrally weaving layered fabrics with internally split and merged yarn bundles (CN104790117A)" to split multiple yarns on one or more columns of spindles into single yarns and move them to adjacent columns of spindles, or to merge yarns on multiple columns of spindles into one column of spindles, so as to achieve the gradual widening and thinning of the cross-section of the material, as well as the gradual narrowing and thickening. In 2017, the patent "A method for weaving a 2.5D corner interlocking preform with a decreasing cross-section (CN107740220A)" proposed the use of yarn reduction, yarn transfer, and yarn reed replacement methods to achieve a gradual decrease in the cross-section of the preform. In 2018, the patent "A three-dimensional weaving method and product of a preform with variable cross-section by row and column transformation (CN108998888A)" proposed that without increasing or decreasing the yarn, the arrangement of the new cross-section is completed only by mutual transformation between rows and columns, thereby achieving the change of the cross-section of the three-dimensional woven preform along the length direction. In 2018, the patent "A warp arrangement method and a profiling woven sleeve for a 2.5D contoured woven sleeve (CN109537137A)" proposed a method of arranging the warp yarns in a gradient decreasing manner from both sides of the main warp yarn to the edge, and a 2.5D cylindrical contoured woven sleeve was prepared by this method. In 2023, the patent "A preform for an aircraft engine fan blade and its profiling preparation method (CN117005081A)" proposed to change the weft width by increasing or decreasing the number of warp yarn rows, and to change the warp and weft thickness by increasing or decreasing the number of warp yarn layers. In 2023, the patent "A preform with variable thickness coupling structure with adjustable fiber orientation and its preparation method (CN117166118A)" proposed to gradually reduce the fabric thickness along the length direction of the preform by reducing the number of inner weft yarn layers and cutting the corresponding warp yarns and lining warp yarns, and convert part of the lining warp in the low thickness area into bias yarns along the in-plane deflection, so as to realize the weaving of a three-dimensional woven preform with variable thickness of bias yarns. In 2024, in the patent "A weaving method for reducing yarn holes in thin 2.5D preforms (CN117888278A)", it was proposed to move part of the warp yarns in the adjacent columns of the added yarn column to its empty spindles, and then add yarn to the remaining empty spindles in the added yarn column and the empty spindles in the adjacent columns, and use the "blocking" effect of the inter-column yarn transfer to compensate for the penetrating holes.

[0004] In 2007, the paper "Yarn Addition and Reduction Mechanism of Variable-Section Three-Dimensional Braided Preforms" studied the yarn reduction mechanism of reducing yarn fineness and reducing the number of yarns at the cross-sectional changes, and established a fiber bundle interlaced structure model of three-dimensional braided preforms with yarn reduction process. It was found that there were no permeable void defects on the surface of the preforms of the two yarn reduction processes. In 2018, the paper "Axial Tensile Properties of Three-Dimensional Woven Composite Materials with Variable Structures" used a combination of yarn addition, yarn reduction, and yarn transfer to prepare four 2.5D woven composite material specimens with variable structures with equal cross-sections. The material tensile strength and tensile modulus retention rates were greater than 93% and 88%, respectively. In 2021, the paper "Design of Near-Net Shape Braided Structure of Typical Multidirectional 2.5D Woven Preforms" targeted the lining warp 2.5D woven structure. During the weaving process, the inner warp yarn / binding warp yarn of the preform was led out to the surface along the thickness direction, and a yarn was added at the lead-out position to replace the lead-out yarn to participate in subsequent weaving. Taking yarn type, number of lead-in and lead-out, and the state of the heald frame during lead-out as variables, five methods of lead-in and yarn addition were proposed. The flexural strength and flexural modulus retention rates of the five composite materials prepared by this method reached 82.6% to 95.7% and 89.1% to 97.9%, respectively.

[0005] In 2018, in the paper "X-ray 3D microscopy analysis of fracture mechanisms for 3D orthogonal woven E-glass / epoxy composites with drilled and moulded-inholes", a perforated glass / epoxy three-dimensional orthogonal woven composite was prepared by inserting cylindrical pins between adjacent warp rows and adjacent wefts. Compared with drilled composites, the retention rate of tensile and bending strength of perforated composites increased by 20%-30%. In 2020, in the paper "Improving the open-hole tension characteristics with variable-axial composite laminates: Optimization, progressive damage modeling and experimental observations", two yarn loop path schemes were designed based on the principal stress vector and direct fiber path optimization method, and the customized fiber placement (TFP) technology was used to consolidate the continuous yarn on the substrate according to the designed path. The tensile strength retention rates of the porous composite materials obtained according to the two design schemes were 68.15% and 97.98%, respectively, which were 20.47% and 50.3% higher than those of the drilled samples, respectively. In 2024, in the paper "Experimental and numerical analysis of drilled-and molded-hole glass fiber reinforced polymer matrix (GFRP) composites", the fracture position of the composite specimens made by the extrusion process appeared in the non-hole area, and the tensile strength was 12% higher than that of the drilled specimens.

[0006] In summary, the design methods of three-dimensional woven / knitted variable cross-sections include: (1) changing the yarn fineness in the cross-section change area, that is, thickening or thinning the yarn, usually by plying and splitting the yarn. (2) changing the number of yarns involved in the weaving in the cross-section change area, that is, adding or subtracting yarns. When the number of yarns subtracted is constant, all rows of yarns in the entire column, or part of the rows of yarns in multiple columns are subtracted. (3) changing the yarn path, including shifting yarns between warp columns in the weft direction, drawing yarns out of the plane in the thickness direction, and adding yarns in the plane. (4) a combination of the above three methods. Most of the existing variable cross-section design methods are aimed at the situation where the entire cross-section of the material changes, and there are fewer design methods for small-area cross-section changes. There are currently only a few reports on the design methods of reserved through holes for three-dimensional weaving / knitting, most of which use a cylindrical core mold to extrude the fibers to form a circular hole. The extruded composite material maintains the continuity of the reinforcing fiber, and the strength retention rate is improved to a certain extent compared with the drilled composite material. However, the controllability and designability of the hole extrusion process are relatively weak. In the case of high warp and weft density and large hole diameter, it may cause operational difficulties and serious yarn protrusions on the surface of the fabric around the holes. Using TFP technology to lay reinforcing fibers according to the designed fiber path seems to be the optimal solution to achieve reinforcement around the holes. After optimizing the reinforcing fiber path, the strength retention rate can almost reach 100%, but this technology is currently limited to laminated composite materials. Therefore, how to maintain the continuity of the fibers of the three-dimensional woven / woven preform while optimizing the design of the fiber path and volume content around the holes according to the stress distribution of the open-hole three-dimensional woven / woven composite material under load to achieve the maximum mechanical property retention rate is the focus of the through-hole weaving method. Summary of the invention

[0007] In order to solve the technical problems existing in the known technology, the present invention provides an overall contour weaving method for a 2.5D woven fabric with a lining warp containing through holes. In order to realize the continuity of the overall fiber structure, the weaving method proposes a yarn shifting-yarn adding method based on the relationship between the hole diameter and the warp yarn density and the principle of minimizing the change in the yarn space path. The warp yarn that originally needs to be cut at the hole position is moved to other warp yarn columns around the hole by shifting the yarn layer by layer. The yarn adding method ensures that the fiber volume content at the yarn shifting position remains unchanged before and after the yarn shifting. The yarn shifting also increases the fiber volume content in the area around the hole, which can reduce the stress concentration phenomenon around the hole and improve the mechanical properties of the 2.5D woven composite material with a lining warp containing through holes.

[0008] The present invention includes the following technical solutions:

[0009] A method for integral contour weaving of a 2.5D woven fabric with through holes and a lining warp, comprising the following steps: S1, determining the number of warp yarn columns that need to be moved according to the warp density of the fabric and the diameter of the through holes; S2, designing the number of yarn moves and the number of yarns moved each time according to the total number of yarns moved; S3, after the opening movement, moving the yarn and changing the reed according to the designed yarn moving scheme, and performing the yarn moving and reed changing operation once every weft; after each yarn moving, adding the same yarn to the position of the vacant yarn in the moving yarn column, one end of the yarn is connected to the creel, and the other end is hung outside the preform, and the added yarn replaces the removed yarn to participate in subsequent weaving; S4, when all the yarns in the moving yarn column are moved away, the added yarn is removed from the creel Remove and hang it outside the preform, and place a cylindrical core mold that penetrates the fabric in the thickness direction at the center line of the hole. The core mold is squeezed with adjacent multiple layers of warp and weft yarns to form a through-hole structure with yarn wrapped around the hole layer by layer; S5, reintroduce yarn from the outside of the fabric to fill the gaps in the moved yarn column, and move the removed yarn back every other weft in the manner of "moving the yarn moved back later first"; when the yarn is moved back to the moved yarn column, first lead the yarn added at the corresponding position of the yarn out of the fabric, and then the moved back yarn replaces the led-out yarn and returns to the initial position. After all the yarns are moved back, cut off the yarn remaining on the outer surface of the preform (the yarn can also be called added yarn), and the weaving operation is ended.

[0010] Furthermore, the number of warp yarns in S1 is N wp , Where P wp is the warp yarn of the fabric, P bi It is the warp density of the fabric.

[0011] Furthermore, the specific number of yarn shifting times and the number of yarns shifted each time in S2 are designed according to the stress distribution of the open-cell 2.5D woven composite material when it is loaded.

[0012] Furthermore, the number of wefts of the yarn shifting and reed changing interval in S3 is determined by the minimum cycle number; the minimum cycle number of 2.5D woven fabric and lining 2.5D woven fabric is 2, and the number of wefts of the interval is 1.

[0013] Furthermore, after the yarn shifting in S3, the reed is changed, the yarn exits the original reed tooth and is replaced by the target row of reed teeth.

[0014] Furthermore, the yarn shifting operation in S3 is based on the principle of minimum change in the spatial position of the yarn before and after the yarn shifting, and specifically includes the following operations: i. When shifting the yarn, the center line of the hole is used as the symmetry axis, and the yarns in the shifting yarn column on the left side of the symmetry axis are shifted to the left, and the yarns in the shifting yarn column on the right side of the symmetry axis are shifted to the right; ii. When shifting the yarn in the weft direction, the target column for each yarn shift is the adjacent column of the column where the yarn is located, that is, one warp yarn column position is moved each time; iii. Each time the yarn is shifted, the warp yarn closest to the middle layer of the fabric is selected to ensure that the structure of the shifting yarn column is stable and the surface of the fabric is smooth and flat; iv. The yarn is moved from the shifting yarn column to the target column, and the shifting yarn column is low If the target column is a warp yarn column with high knots, the yarn will be moved up one warp yarn layer position to above the target column yarn; v. If the yarn is moved from the shifting yarn column to the target column, and the shifting yarn column is a warp yarn column with high knots, the yarn will be moved down one warp yarn layer position to below the target column yarn; vi. If the yarn is moved from the shifting yarn column to the target column, and the shifting yarn column is a warp yarn column, if the target column is a warp yarn column with high knots, the yarn will be moved up one warp yarn layer position to above the target column yarn, otherwise it will be moved down one warp yarn layer position to below the target column yarn; ⅶ. When the yarn is shifted between columns that do not contain the shifting yarn column, it will move horizontally within the layer without changing the yarn layer position, and the yarn before and after the shifting yarn is located in the same warp yarn layer.

[0015] Furthermore, the high binding warp yarn column and the low binding warp yarn column differ by two yarn layer heights, the relatively higher group is called the high binding warp yarn column, and the other group is called the low binding warp yarn column.

[0016] Furthermore, when adding yarn in S3, if the column where the added yarn is located belongs to the low-knot warp yarn column, it is introduced from the outside of the upper surface of the fabric; if the column where the added yarn is located belongs to the high-knot warp yarn column, it is introduced from the outside of the lower surface of the fabric; if it is a warp yarn, it can be introduced from the outside of the upper surface or the lower surface of the fabric.

[0017] Furthermore, when it is not the first time to move the yarn in S3, the yarn movement is performed in the order of the yarn movement history; according to the method of "the yarn moved out in the previous step is moved first", the yarn moved out in the previous yarn moving step is first moved further to the adjacent column, and then the newly moved yarn in the current yarn moving step is moved to the adjacent column.

[0018] Furthermore, moving the yarn back in S5 is the "reverse process" of moving the yarn out, following the principle of "the yarn moved out later is moved back first", that is, the yarn closer to the center line of the hole in the weft direction is moved back first.

[0019] The present invention has the following advantages and positive effects:

[0020] 1. Compared with the prior art, the present invention ensures the integrity of the fiber bundle reinforcement skeleton and the continuity of the reinforced fiber bundle by gradually moving the warp yarns in the intersection area of ​​the hole and the fabric to the area around the hole.

[0021] 2. The present invention adopts a multi-step layer-by-layer yarn shifting method to move the yarn to other rows around the hole to reserve a suitable space for the hole, thereby avoiding a sudden change in the thickness of the fabric around the hole, and at the same time slowly and evenly increasing the fiber volume content around the hole as the yarn is shifted; the present invention starts to move from the middle layer yarn first to ensure that the structure of the yarn shifting row is stable, the fabric surface is smooth and flat, and the structure is complete.

[0022] 3. In order to avoid the reduction in strength caused by cutting the yarn, the present invention adopts the yarn shifting-yarn adding method to ensure that the fiber volume content at the shifting position remains unchanged before and after the yarn shifting; after the yarn is shifted by the method of the present invention, the increase in the fiber volume content around the hole and the formation of the annular hole path further alleviate the phenomenon of stress concentration around the hole, so that the strength retention rate of the porous composite material is as close to 100% as possible.

[0023] 4. The interwoven structure of the 2.5D woven fabric with through-hole lining obtained by the present invention has good integrity and strong designability, which ensures the structural integrity and load-bearing performance of the composite material components reinforced by it. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Angle 1 of the three-dimensional view of 2.5D woven fabric with through-hole lining;

[0025] Figure 2 The second angle of the three-dimensional view of the 2.5D woven fabric with through-hole lining;

[0026] Figure 3 Schematic diagram of yarn arrangement and movement law of 2.5D woven fabric with φ4mm through-hole lining; Figure 3 (a) is a schematic diagram of the movement of odd-numbered weft and warp yarns. Figure 3 (b) is a schematic diagram of the movement of even-numbered weft and warp yarns;

[0027] Figure 4 This is a schematic diagram of yarn transfer through a φ4mm through hole; Figure 4 (a) is the motion law of the yarn during the first yarn transfer. Figure 4 (b) is the movement law of the yarn during the second yarn transfer. Figure 4 (c) is the movement law of the yarn during the third yarn shifting. Figure 4 (d) is the movement law of the yarn during the fourth yarn transfer;

[0028] Figure 5 for Figure 4 Schematic diagram of the change of the cross-sectional shape of the warp yarn during the yarn shifting process;

[0029] Figure 6 This is a schematic diagram of the yarn being moved back through a φ4mm hole; Figure 6 (a) is the motion law of the yarn when the yarn is moved back for the first time. Figure 6 (b) is the movement law of the yarn when the yarn is moved back for the second time. Figure 6(c) is the movement law of the yarn when the yarn is moved back for the third time. Figure 6 (d) is the movement law of the yarn when the yarn is moved back for the fourth time;

[0030] Figure 7 This is a schematic diagram of the yarn arrangement and movement law of a 2.5D woven fabric with a φ6mm through-hole lining; Figure 7 (a) is a schematic diagram of the movement of odd-numbered weft and warp yarns. Figure 7 (b) is a schematic diagram of the movement of even-numbered weft and warp yarns;

[0031] Figure 8 This is a schematic diagram of yarn transfer through a φ6mm hole; Figure 8 (a) is the motion law of the yarn during the first yarn transfer. Figure 8 (b) is the movement law of the yarn during the second yarn transfer. Figure 8 (c) is the movement law of the yarn during the third yarn shifting. Figure 8 (d) is the movement law of the yarn during the fourth yarn shift. Figure 8 (e) is the movement law of the yarn during the fifth yarn transfer;

[0032] In the figure, 11 is the connecting warp yarn, 12 is the warp yarn, 13 is the center line of the hole; 21 is the first weft of the shifted yarn, 22 is the last weft of the shifted yarn, 23 is the shifted yarn area, 24 is the two columns of warp yarns of the shifted yarn; 61 is the added warp yarn, and 62 is the added connecting warp yarn. DETAILED DESCRIPTION

[0033] In order to further disclose the content, features and effects of the invention, the following examples are specifically cited and described in detail in conjunction with the accompanying drawings. In the description of the following embodiments, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing this patent and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this patent.

[0034] In the description of the following embodiments, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, it can be fixedly connected or set, or it can be detachably connected or set, or connected or set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0035] Example 1, see attached Figure 1-6, a method for integrally weaving a 2.5D woven fabric with a φ4mm through hole; the fabric thickness is 4±0.1mm, and comprises 8 layers of warp yarns 12 and 9 layers of weft yarns. The warp yarns 12 and weft yarns are T800-12K carbon fibers, the connecting warp yarns 11 are T300-3K carbon fibers, and the warp density is P wp And knot warp density P bi 3±0.2mm root / cm, weft density P wf The warp yarns 12 and the binding warp yarns 11 are collectively referred to as warp yarns.

[0036] The arrangement and movement of the warp yarn 12 on the creel are as follows: Figure 3 As shown, the arrows in the figure indicate the direction of movement of the binding warp yarn rows, and the dotted line indicates the hole center line 13. Only 10 rows of warp yarns symmetrical about the hole center line 13 in the yarn transfer area 23 are shown here.

[0037] In addition, since the weft yarn has nothing to do with the yarn transfer process, Figure 3 It is omitted in Figure 3 In the warp yarn composition shown, the binding warp yarn columns are divided into two groups, and the difference between the two groups is two yarn layers. The relatively higher group is called the high binding warp yarn column, and the other group is called the low binding warp yarn column. In each weft of the weaving process, the warp yarn column does not move, the high binding warp yarn column moves downward, and the low binding warp yarn column moves upward by two yarn layers. In the weaving process, two wefts form a cycle, which is divided into odd wefts and even wefts, corresponding to the two warp yarn arrangement states. Figure 3 Among them, L1 to L10 represent the warp yarn column position numbers, and R1 to R10 represent the warp yarn layer position numbers. Figure 3 The z-axis direction is defined as up, the -z-axis direction is defined as down, the -y-axis direction is defined as left, and the y-axis direction is defined as right. The shifting yarn column refers to the warp yarn column for the shifting yarn operation. The target column refers to the column where the yarn is located after the yarn is moved from the shifting yarn column to the non-shifting yarn column. The shifting yarn area 23 refers to the weft where the yarn is located from the first shifting yarn to the last shifting yarn, and the rectangular area formed by the column where the yarn of the shifting yarn column moves the farthest to both sides along the hole center line 13.

[0038] In order to minimize the change in the spatial position of the yarn before and after the yarn shifting, the yarn shifting follows the following principles: (1) When shifting the yarn, take the hole center line 13 as the symmetry axis, the yarns in the shifting yarn column on the left side of the symmetry axis shift to the left, and the yarns in the shifting yarn column on the right side of the symmetry axis shift to the right. (2) The target column for each yarn shift is the adjacent column to the column where the yarn is located, that is, one warp yarn column position is moved each time. (3) Each time the yarn is shifted, the warp yarn closest to the middle layer of the fabric is selected to ensure that the structure of the shifting yarn column is stable and the surface of the fabric is smooth and flat. (4) When the yarn moves from the shifting yarn column to the target column, and the shifting yarn column is a low-binding warp yarn column, it is moved up one warp yarn layer position to above the target column yarn. (5) When the yarn moves from the shifting yarn column to the target column, and the shifting yarn column is a high-binding warp yarn column, it is moved down one warp yarn layer position to below the target column yarn. (6) The yarn is moved from the shifting yarn column to the target column, and the shifting yarn column is a warp yarn column. If the target column is a high-binding warp yarn column, the yarn is moved up one warp yarn layer position to above the target column yarn, otherwise it is moved down one warp yarn layer position to below the target column yarn. (7) When the yarn is shifted between columns that do not contain the shifting yarn column, the horizontal movement within the layer does not change the yarn layer position, and the yarn is located in the same warp yarn layer before and after the shifting yarn.

[0039] A method for integrally weaving a 2.5D woven fabric with a φ4mm through hole comprises the following steps:

[0040] (1) Determine the number of shifted yarns, times and roots. Determine the number of warp yarns occupied by the hole according to the warp density and the knotting warp density. wp :

[0041]

[0042] For this embodiment, N wp The value is 2. The total number of shifted yarns is 16, and the number of shifted yarns is set to 4. By shifting the yarns layer by layer, the thickness of the fabric around the holes can be avoided from changing suddenly, and the volume content of the fibers around the holes can be increased slowly and evenly with the shifting of the yarns. The total number of shifted yarns is evenly divided according to the number of shifted yarns, and the number of shifted yarns each time is 4. The first shifted yarn position is taken as the first weft 21 of the shifted yarn, and the yarn arrangement state at this time corresponds to the odd weft. The relationship between the lining warp 2.5D woven fabric structure and the position of the hole and the shifted yarn area 23 is shown in the figure. Figure 1-Figure 2 As shown, the x-axis is the longitude direction, the y-axis is the latitude direction, and the z-axis is the thickness direction.

[0043] (2) Yarn shifting and reed changing. After the opening movement, select the yarn closest to the middle layer of the shifting yarn column (column L5, L6) (column 5 of the 6th layer, column 5 of the 7th layer, column 6 of the 5th layer, column 6 of the 6th layer), remove the yarn from the creel, and according to the above-mentioned yarn shifting principle, move up one warp yarn layer position and move to the top of the yarn at the target column position (column 4 of the 5th layer, column 4 of the 6th layer, column 7 of the 4th layer, column 7 of the 5th layer). After the yarn shifting, the yarn exits the original reed tooth and is replaced by the target reed tooth. Then, 9 layers of weft yarn are introduced between the warp yarn layers layer by layer from top to bottom and the weft is beaten.

[0044] (3) Weave one weft according to the weaving motion law of the lining warp 2.5D woven fabric. No yarn transfer is performed in this step, and the transferred yarn is interwoven with the weft yarn according to the motion law of the row in which it is located.

[0045] (4) Repeat the yarn shifting and reed changing of step (2) above. The difference is that there are two groups of yarns at this time, including the yarns that have been shifted before and the newly moved yarns in the current yarn shifting step. The yarn shifting is carried out in the order of the yarn shifting history, following the principle of "the yarns moved out in the previous step are moved first". First, the yarns moved out of the previous yarn shifting point are further moved to the target column, specifically, the yarns (4th column of the 5th layer, 4th column of the 6th layer, 7th column of the 4th layer, 7th column of the 5th layer) are translated to the target column position (3rd column of the 5th layer, 3rd column of the 6th layer, 8th column of the 4th layer, 8th column of the 5th layer). Then the newly moved yarns in the current yarn shifting step (5th column of the 5th layer, 5th column of the 8th layer, 6th column of the 4th layer, 6th column of the 7th layer) are moved to the corresponding positions (4th column of the 4th layer, 4th column of the 7th layer, 7th column of the 3rd layer, 7th column of the 6th layer) according to the yarn shifting process described in step (2). After all the yarns have been moved, all the yarns will exit the reed teeth in turn and enter the target row of reed teeth according to the above yarn moving sequence. Finally, 9 layers of weft yarns are introduced layer by layer between the warp yarn layers and beaten.

[0046] (5) Repeat steps (3) and (4) until all the yarns in the shifting yarn column are moved out and evenly distributed to the shifting yarn area around the hole. At this time, weave to the weft where the weft bisector of the hole is located (the 8th weft). Then, a cylindrical core mold that penetrates the thickness of the fabric is placed vertically at position 13 of the center line of the hole. The core mold is squeezed with the adjacent multiple layers of warp and weft yarns, and the yarns around the hole wrap around the core mold layer by layer to form a through-hole structure. The position changes of each weft of the shifting yarn column are shown in Table 1. The first element of the coordinate represents the position number of the warp yarn layer, and the second element represents the position number of the warp yarn column. Since each yarn undergoes multiple steps of yarn shifting, the total number of movements of the 16 yarns is 40 times. The schematic diagram of the φ4mm simulated through-hole yarn shifting is shown in Figure 1. Figure 4 As shown, since there is no yarn shifting operation for even-numbered wefts, only odd-numbered wefts are shown in the figure. The number i in the circle in the figure indicates that the first yarn shift is the i-th yarn shift, i = 1 to 4. From the 1st weft to the 7th weft, two columns of yarn are shifted to the two sides of the hole center line in 4 times, a total of 10 columns of warp yarns.

[0047] Table 1 Schematic diagram of the change of each weft position of the yarn in the φ4mm through-hole shifting yarn array

[0048]

[0049] (6) The yarns that have been moved out and distributed in the warp yarn column around the hole are gradually moved back to the moving yarn column in batches. Moving the yarn back is the "reverse process" of moving the yarn out, and follows the principle of "the yarns that were moved out later are moved back first", that is, the yarns that are closer to the hole center line 13 in the weft direction (y direction) are moved back first. When the yarn is moved to the moving yarn column, it is moved down one warp yarn layer position, otherwise it is moved horizontally to the target column. As with the process of moving the yarn out, the odd-numbered wefts are used to move the yarn back. From the 11th weft to the 17th weft, all the moved out yarns are moved back to their original positions in 4 times. The schematic diagram of moving the yarn back with a φ4mm through hole is shown in the figure below. Figure 6 As shown in the figure. From the first yarn transfer to the last yarn return, a total of 17 wefts are passed. After all the yarns are returned to the yarn transfer row, the contour knitting process of the 2.5D woven fabric with φ4mm through-hole lining warp is completed.

[0050] Example 2, see attached Figure 1 , 2 , 7, 8, a method for integrally weaving a 2.5D woven fabric with φ6mm through holes. This embodiment is a supplement to the embodiment 1. For the case where the number of shifting yarn columns is an odd number, the fabric structure is the same as that of the embodiment 1. The arrangement and movement rules of the warp yarns on the creel are as follows Figure 7 As shown, the arrow indicates the direction of movement of the binding warp yarn row, and the dotted line indicates the hole center line 13. According to the formula described in Example 1, N wp The value is 3. Move 3 columns of 24 yarns in 4 times, and the total number of yarns moved is allocated to each yarn moving step according to the gradient. The number of yarns moved from the 1st to the 4th time is 3, 6, 6, and 9 respectively.

[0051] Each time the yarn is shifted, the yarn closest to the middle layer in the shifting yarn column is selected. The yarns in the shifting yarn column on the left side of the hole center line 13 are shifted to the left, and the yarns in the shifting yarn column on the right side are shifted to the right. The yarns in the shifting yarn column at the hole center line 13 are shifted alternately to the left and right sides, and each time they are moved to the adjacent warp yarn column. According to the sequence of the yarn shifting history, the yarns shifted out in the previous step and the yarns in the shifting yarn column added in the current step are moved, that is, in the weft direction (y direction), the yarns in the shifting yarn column farther from the hole center line 13 are moved first. When the yarns are shifted between columns that do not contain the shifting yarn column, the yarns move in parallel, and the z-direction position of the yarns remains unchanged. Otherwise, according to the relative height between the shifting yarn column and the target column, if the relative position of the target column is higher, move up one warp layer position to above the target column yarns, otherwise, move down one warp layer position to below the target column yarns.

[0052] In addition, compared with Example 1, this embodiment adds a yarn adding process to compensate for the reduction in fiber volume content at the shifting yarn column position caused by yarn shifting. The yarn adding process is also applicable to Example 1. The specific method is that after each yarn shifting, yarn is added to the vacant yarn position of the shifting yarn column to replace the shifted yarn to participate in subsequent weaving. The added and shifted yarns are of the same type. The added yarn is introduced from the outer surface of the fabric along the thickness direction. Specifically, if the shifting yarn column is a low-knot warp yarn column, it is introduced from the outside of the upper surface of the fabric. If the shifting yarn column is a high-knot warp yarn column, it is introduced from the outside of the lower surface of the fabric. If it is a warp yarn, it can be introduced from the outside of the upper or lower surface of the fabric.

[0053] A method for integrally weaving a 2.5D woven fabric with a 6mm through hole comprises the following steps:

[0054] (1) Yarn transfer and reed replacement. After the opening movement, select the three yarns (R6L5, R7L6, R6L7) in the middle layer of the transfer yarn column (L5, L6, L7), take them off the yarn rack, and according to the above-mentioned yarn transfer principle, move them up one warp layer to above the yarns in the target column (R5L4, R6L5, R5L8). After the yarn transfer, the yarn exits the reed where it is located and is replaced by the reed where the target column is located. The symbol RmLn represents the yarn in the mth layer and nth column.

[0055] (2) Yarn introduction and yarn addition. Introduce the same type of yarn from the outside of the upper surface of the fabric to the yarn missing position (R7L6, R6L7) of the yarn transfer row, hang one end on the yarn rack, and pass the other end through the reed teeth to hang on the outside of the fabric. After the yarn addition is completed, introduce 9 layers of weft yarn between the warp yarn layers layer by layer and beat up.

[0056] (3) Weave one weft according to the weaving motion law of the lining warp 2.5D woven fabric. No yarn transfer is performed in this step, and the transferred yarn is interwoven with the weft yarn according to the motion law of the row in which it is located.

[0057] (4) Multiple groups of yarns are moved and reeds are replaced. According to the yarn moving principle, the yarns (R5L4, R6L5, R5L8) moved out in the previous step are first moved to the top of the yarns at the target position (R5L3, R5L4, R5L9) in the adjacent column. Then the newly added yarns (R5L5, R7L5, R5L7, R7L7, R8L6, R6L6) are moved to the top of the yarns at the designated position (R4L4, R6L4, R4L8, R6L8, R7L5, R5L7). Finally, the moved yarns are removed from the reed where they are located and replaced with the reed where the target column is located.

[0058] (5) Repeat steps (2)-(4) until all the yarns in the three shifting yarn columns are moved out and distributed to the shifting yarn area around the hole, and at the same time, the missing yarn positions in the three shifting yarn columns are completely filled with the added yarns. This is the 9th weft. The changes in the shifting yarn positions of the shifting yarn columns for each weft are shown in Table 2. Each yarn undergoes multiple shifting yarns, with a total of 54 shifting times. Weave one weft conventionally, then remove the three added columns of yarn from the yarn frame and hang them outside the fabric. After weaving another weft, a cylindrical core mold that penetrates the thickness of the fabric is vertically placed at the center line of the hole. The core mold is squeezed with the adjacent multiple layers of warp and weft yarns to form a through-hole structure with yarns wrapped around the hole layer by layer. The schematic diagram of the φ6mm through-hole shifting yarn is shown in Figure 8 As shown, only 11 columns of warp yarns with odd numbered wefts are shown in the figure.

[0059] Table 2 Schematic diagram of the change of each weft position of the yarn in the φ6mm through-hole shifting yarn array

[0060]

[0061] (6) After the cylindrical core mold is placed, one weft is woven, and three rows of warp yarns are added from the outside of the upper and lower surfaces of the fabric. One end is hung on the outside of the fabric, and the other end is hung on the yarn rack to participate in subsequent weaving. The yarns of the yarn shifting column distributed in the yarn shifting area 23 are gradually moved back to the original position of the yarn shifting column according to the "reverse process" of the yarn being moved out. When the yarn is moved back, the yarn corresponding to the yarn adding position is first removed from the yarn rack, led out along the thickness direction and hung on the outside of the fabric. The returned yarn replaces the "added yarn" and returns to the initial position to participate in subsequent normal weaving. After all the yarns are moved back, they are woven conventionally to the predetermined length, and finally the machine is removed and the yarns left on the outside of the fabric are cut off. At this point, the overall weaving process of the 2.5D woven fabric with φ6mm through-hole lining warp is completed.

[0062] Although the preferred embodiments of the present invention are described above, the present invention is not limited to the above specific embodiments, which are merely illustrative and not restrictive. Under the guidance of the present invention, a person skilled in the art can make many forms without departing from the scope of protection of the present invention and the claims. All of these fall within the protection scope of the present invention.

Claims

1. A method for integrally profiling a 2.5D woven fabric with through holes, characterized in that The following steps are involved: S1. Determine the number of warp yarns that need to be shifted according to the warp density and through-hole diameter of the fabric; S2. Design the number of yarn shifting times and the number of yarns shifted each time according to the total number of shifted yarns; S3. After the opening movement, shift the yarn and change the reed according to the designed yarn shifting plan, and perform the yarn shifting and reed changing operation every other weft; after each yarn shifting, add the same yarn to the position of the vacant yarn in the shifting yarn column, one end of the yarn is connected to the creel, and the other end is hung outside the preform, and the added yarn replaces the removed yarn to participate in the subsequent weaving; S4. When all the yarns in the shifting yarn column are moved away, remove the added yarn from the creel and hang it outside the preform, and place it on the thick center line of the hole. A cylindrical core mold penetrates the fabric in the direction of degree, and the core mold is squeezed with adjacent multiple layers of warp and weft yarns to form a through-hole structure with yarns wrapped around the hole layer by layer; S5, yarns are reintroduced from the outside of the fabric to fill the gaps in the moved yarn column, and the removed yarns are moved back every other weft in the manner of "the yarns moved later are moved back first"; when the yarns are moved back to the moved yarn column, the yarns added at the corresponding positions of the yarns are led out of the fabric, and the moved back yarns replace the led-out yarns and return to the initial position. After all the yarns are moved back, the yarns remaining on the outer surface of the preform are cut off, and the weaving operation is ended.

2. The integral contour weaving method of a 2.5D woven fabric with through-holes as claimed in claim 1, characterized in that: The number of warp yarns in S1 is N wp , Where P wp is the warp density of the fabric, P bi It is the warp density of the fabric.

3. The integral contour weaving method of a 2.5D woven fabric with through-holes as claimed in claim 1, characterized in that: The specific number of yarn shifting times and the number of yarns shifted each time in S2 are designed according to the stress distribution of the open-cell 2.5D woven composite material when it is loaded.

4. The integral contour knitting method of a 2.5D woven fabric with through-holes as claimed in claim 1, characterized in that: The number of wefts of the yarn shifting and reed changing interval in S3 is determined by the minimum cycle number; the minimum cycle number of 2.5D woven fabric and lining 2.5D woven fabric is 2, and the number of wefts of the interval is 1.

5. The integral contour knitting method of a 2.5D woven fabric with through-holes as claimed in claim 1, characterized in that: After the yarn is moved in S3, the reed is changed, the yarn exits the original reed tooth and is replaced by the target row of reed teeth.

6. The integral contour knitting method of a 2.5D woven fabric with through-holes as claimed in claim 5, characterized in that: The yarn shifting operation in S3 is based on the principle of minimum change in the spatial position of the yarn before and after the yarn shifting, and specifically includes the following operations: i. When shifting the yarn, the center line of the hole is used as the symmetry axis, the yarns in the shifting yarn column on the left side of the symmetry axis are shifted to the left, and the yarns in the shifting yarn column on the right side of the symmetry axis are shifted to the right; ⅱ. The target column of each yarn shift is the adjacent column of the column where the yarn is located, that is, one warp yarn column position is moved each time; ⅲ. The warp yarn closest to the middle layer of the fabric is selected each time the yarn is shifted; iv. The yarn is moved from the shifting yarn column to the target column, and if the shifting yarn column is a low-binding warp yarn column, the yarn is moved up by one warp yarn layer to above the target column yarn; ⅴ, when the yarn is moved from the shifting yarn row to the target row, and the shifting yarn row is a high-binding warp yarn row, the yarn is moved down one warp yarn layer to below the target row yarn; ⅵ. The yarn is moved from the shifting yarn column to the target column, and the shifting yarn column is a warp yarn column. If the target column is a high-binding warp yarn column, the yarn is moved up by one warp yarn layer to above the yarn in the target column, otherwise, the yarn is moved down by one warp yarn layer to below the yarn in the target column; ⅶ. When the yarn is shifted between columns that do not include the shifting yarn column, it moves horizontally within the layer without changing the position of the yarn layer. The yarn is located in the same warp yarn layer before and after the shifting yarn.

7. The method for integrally profiling a 2.5D woven fabric with through-holes as claimed in claim 6, characterized in that: The high binding warp yarn row and the low binding warp yarn row differ by several yarn layer heights. The relatively higher group is called the high binding warp yarn row, and the other group is called the low binding warp yarn row.

8. The integral contour knitting method of a 2.5D woven fabric with through-holes as claimed in claim 7, characterized in that: When adding yarn in S3, if the added yarn is in a row belonging to a low-binding warp yarn row, it is introduced from the outside of the upper surface of the fabric; if the added yarn is in a row belonging to a high-binding warp yarn row, it is introduced from the outside of the lower surface of the fabric; if it is a warp yarn, it can be introduced from the outside of the upper surface or the lower surface of the fabric.

9. The method for integrally contour weaving a 2.5D woven fabric with through-holes as claimed in claim 1, characterized in that: When it is not the first time to move the yarn in S3, the yarn is moved in the order of the yarn moving history; according to the method of "the yarn moved out in the previous step is moved first", the yarn moved out in the previous yarn moving step is first moved further to the adjacent column, and then the newly moved out yarn in the current yarn moving step is moved to the adjacent column.

10. The integral contour knitting method of a 2.5D woven fabric with through-holes as claimed in claim 1, characterized in that: Moving the yarn back in S5 is the "reverse process" of moving the yarn out, following the principle of "the yarn moved out later is moved back first", that is, the yarn closer to the center line of the hole in the weft direction is moved back first.

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