Applications of opening aids in 3D knitting

Abstract

This invention discloses the application of an opening-aiding tool in three-dimensional weaving. A preform is woven using a four-step three-dimensional weaving method, forming at least one fabric opening, which is a slit. The opening-aiding tool is inserted into the fabric opening to expand it into a cavity of a specific shape. The opening-aiding tool includes an inlet portion and an expanding portion connected to the inlet portion. The inlet portion and the expanding portion are arranged along the length direction of the opening-aiding tool. The rear end of the inlet portion is fixed to the front end of the expanding portion. The inlet portion is a sheet whose width gradually decreases from back to front, and the edge of the tapering is a smooth line. The centerline along the length direction of the opening-aiding tool is used as the axis. The opening-aiding tool of this invention can achieve precise control of the cavity size, helping to solve problems such as large deviations between design parameters and actual production parameters, and difficulties in fabric structure control in existing three-dimensional weaving technologies.

Description

Technical Field

[0001] This invention belongs to the field of high-performance fiber weaving technology, and specifically relates to the use of an opening auxiliary tool in three-dimensional weaving. Background Technology

[0002] To meet the material performance requirements of aerospace equipment, the development of composite materials with high specific strength, high specific modulus, and low density has become a key area. Polygonal lattice structures, characterized by their light weight, high porosity, and low density, have become an important component of core materials for aerospace composites. Currently, the widely used polygonal lattice materials are mainly based on single-layer bonding structures. However, the W-direction inter-wall nodes of the polygonal lattice have weak performance, forming weak loops in the structure. With the development of space exploration, this structure is no longer sufficient to meet performance requirements.

[0003] To address the weak inter-wall connectivity in the W-direction of existing polygonal core lattice structures, a polygonal core lattice prefabricated structure with W-direction interlayer connectivity is obtained using three-dimensional weaving, such as... Figure 1 As shown (the polygonal core is hexagonal), the polygonal core preform is formed by arranging and connecting identical unit cells in an array, with openings formed inside the unit cells. This structure is used as a reinforcing material to further prepare polygonal core composite materials.

[0004] For 3D weaving technology, the four-step method is the fundamental approach to the overall process. The four-step 3D weaving method is currently a relatively mature technology for the integrated molding of irregularly shaped prefabricated structures. The four-step 3D weaving method uses a yarn carrier to carry the yarn, moving it in the X and Y directions according to a set pattern on a Cartesian lathe. The integrated prefabricated structure is formed through the circular motion of the yarn carrier disc along the X and Y axes. Figure 2 The motion trajectory diagram of the yarn carrier is woven. When a certain column of the yarn carrier is controlled to only allow it to move along a single Y-axis in a fixed column, multiple pieces of fabric will be generated inside the preform. By controlling the spacing and position of the fixed columns, the opening and closing of holes can be formed, and finally a polygonal core preform is generated.

[0005] In existing technologies, although the weaving of polygonal core-grid fabrics has been achieved, the use of semi-automatic production modes in actual processing for shape and weaving parameter control has become a key issue affecting the stability of polygonal core-grid fabric performance. Current four-step three-dimensional weaving polygonal core-grid technology employs a core mold-on-demand forming method (i.e., inserting a core mold into each row of unit cells after weaving) to form the polygonal core-grid fabric (e.g., ...). Figure 1 This forming method, under the influence of gravity and tension, will produce significant fabric deformation, resulting in tension errors (such as...). Figure 3 a and Figure 4(As shown). This tension error is affected by the weaving process, operating techniques, and molding technology, making it difficult to predict, control, and correct. Ultimately, this leads to inaccurate molding of the polygonal core structure, severely affecting the performance of the finished material and limiting its application scenarios.

[0006] For example, patent CN115058825A (application number 202210635648.0) discloses a three-dimensional weaving method for a polygonal core structure. This method involves rotating a planar yarn carrier to interweave fiber bundles, forming a vertically arranged polygonal core structure. CN115976729A (application number 202211730601.9) discloses a method for weaving large-size polygonal core preforms using array equipment, involving a four-step three-dimensional weaving process to form a polygonal core preform. However, these applications do not address the shape control design of the three-dimensional woven polygonal core structure, lacking structural design and control for the formed polygonal core structure. This results in unstable processing parameters and ultimately structural defects. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide an opening auxiliary tool for use in three-dimensional weaving.

[0008] The objective of this invention is achieved through the following technical solution.

[0009] The use of an opening aid tool in three-dimensional weaving: a preform is woven using a four-step three-dimensional weaving method, and at least one fabric opening is formed on the preform. The fabric opening is a slit with a length of L. The opening aid tool is filled into the fabric opening to expand it into a cavity of a specific shape. The opening aid tool includes: an inlet part and an enlarging part connected to the inlet part. The inlet part and the enlarging part are arranged along the length direction of the opening aid tool. The rear end of the inlet part is fixed to the front end of the enlarging part. The inlet part is a sheet with a gradually narrowing width from back to front, and the edge of the gradually narrowing width is a smooth line.

[0010] The perimeter of the rear end face of the inlet section is 2L;

[0011] With the centerline of the opening auxiliary tool along its length as the axis, all circumferences of the enlarged hole are the same, 2L.

[0012] The inlet section is located on the plane containing the axis.

[0013] After the inlet section enters the fabric opening, the plane where the inlet section is located is parallel to the length direction of the gap; the shape of the rear end face of the enlarged section is the same as the shape cut off on the cavity by the plane perpendicular to the axial direction of the cavity.

[0014] In the above technical solution, the edge of the inlet is chamfered or rounded.

[0015] In the above technical solution, the smooth line is either a straight line or an arc.

[0016] In the above technical solution, the thickness of the inlet portion is less than 2mm.

[0017] In the above technical solution, when the length of the expanded hole is less than the axial length of the cavity, the rear end face of the expanded hole is used to fix it with a core mold, the core mold is used to expand the fabric opening into a cavity, and the opening auxiliary tool guides the core mold to fill the fabric opening; when the length of the expanded hole is greater than or equal to the axial length of the cavity, the expanded hole is used to expand the fabric opening into a cavity.

[0018] In the above technical solution, after the opening auxiliary tool and the core mold are fixed, the length direction of the core mold is parallel to the length direction of the opening auxiliary tool.

[0019] The opening aid tool of this invention enables precise control of cavity dimensions, helping to solve problems such as large deviations between design parameters and actual production parameters, and difficulties in fabric structure control in existing three-dimensional weaving techniques. It further reduces processing allowances and avoids defects caused by structural variations. Attached Figure Description

[0020] Figure 1 Photograph of a polygonal core lattice prefab;

[0021] Figure 2 A diagram illustrating the weaving motion trajectory of the yarn carrier in the four-step three-dimensional weaving method;

[0022] Figure 3 The images are of polygonal core lattice preforms. a) shows the core mold forming method, and b) shows the method for preparing the three-dimensional woven polygonal core lattice preforms according to the present invention.

[0023] Figure 4 This is a schematic diagram illustrating the tension error that arises from the core mold forming process.

[0024] Figure 5 This is a structural diagram of the preform in step 1 of the method for preparing a three-dimensional woven polygonal core lattice preform in Example 1;

[0025] Figure 6 This is a schematic diagram of the structure of a polygonal core lattice prefabricated structure (the opening shape inside the unit cell is hexagonal);

[0026] Figure 7 The relationship between the yarn carrier and the formed fabric at each stage;

[0027] Figure 8 This is a schematic diagram of the aperture size control plate.

[0028] Figure 9 This is a schematic diagram of the aperture size control plate.

[0029] Figure 10 The opening θ is the honeycomb lattice opening;

[0030] Figure 11 The opening θ is the honeycomb lattice opening;

[0031] Figure 12 This is a structural schematic diagram of an opening-aiding tool, where a is the front view, b is the side view, c is the top view, and d is the perspective view.

[0032] Figure 13 A schematic diagram of a precision shape control tooling for forming a three-dimensional woven polygonal core lattice preform;

[0033] Figure 14 A schematic diagram of a precision shape control tool for forming a three-dimensional woven polygonal core lattice preform, where a represents the state when the first fabric of the first row is opened and b represents the state when the second fabric of the first row is opened.

[0034] Figure 15 (a) a side view and (b) a perspective view of the reference plane frame;

[0035] Figure 16 This is a structural diagram of the length control positioning strip;

[0036] Figure 17 This is a structural diagram of the length control positioning strip;

[0037] Figure 18 This is a structural diagram of the length control positioning strip;

[0038] Figure 19 This is a structural diagram of the aperture size control plate;

[0039] Figure 20 Structural diagram of the opening auxiliary tool for fixing with the core mold;

[0040] Figure 21 A schematic diagram of a precision shape control tooling for forming a three-dimensional woven polygonal core lattice preform;

[0041] Figure 22 A schematic diagram of the structure of a polygonal core lattice prefabricated structure;

[0042] Among them, 1: inlet part, 2: hole enlargement part, 3: height control frame, 4: reference plane frame, 5: length control positioning strip, 6: first connecting rod, 7: initial position control piece, 8: hole diameter control piece, 8-1: mounting part, 8-2: working part, 9: core mold, 10: first through hole, 11: second through hole, 12: second connecting rod; Detailed Implementation

[0043] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0044] Example 1

[0045] A method for preparing a three-dimensional woven polygonal lattice preform, such as Figure 6 and Figure 22 As shown, the polygonal core prefabricated body is formed by arranging and connecting identical unit cells in an array. An opening (a cavity of a specific shape) is formed inside the unit cell. The shape of the opening inside the unit cell is hexagonal, quadrilateral, circular, octagonal, decagonal or concave hexagonal.

[0046] The length of the binding edge of the unit cell is L b The length of the free side of the unit cell is L. f ;

[0047] The method for preparing a three-dimensional woven polygonal core lattice preform includes the following steps:

[0048] Step 1, use the three-dimensional four-step weaving method to weave as follows: Figure 5 The precast body shown has multiple rows of first fabric opening groups and multiple rows of second fabric opening groups along its width direction. A row of second fabric opening groups is provided between every two adjacent first fabric opening groups. The first fabric opening groups are first fabric openings spaced apart on the precast body along the weaving direction, and the second fabric opening groups are second fabric openings spaced apart on the precast body along the weaving direction. Both the first and second fabric openings are slits. The lengths of the first and second fabric openings are the same, both being L. The upper part of each first fabric opening is opposite to the lower part of one second fabric opening in each of its adjacent two second fabric opening groups, and the precast body of the opposite part is called the upper overlapping part, the length of which is L. f The lower part of each first fabric opening is opposite to the upper part of one second fabric opening in each of the adjacent two second fabric opening groups, and the prefabricated part of the opposite part is the lower overlapping part, the length of the lower overlapping part is L. f Each first fabric opening and the portion of the second fabric openings in the adjacent two-sided second fabric opening groups that do not overlap constitute a first non-overlapping portion, the length of which is L. b =L-2L f The prefabricated portion of each second fabric opening that is not opposite to the first fabric opening in the adjacent two-sided first fabric opening group is the second non-overlapping portion, and the length of the second non-overlapping portion is L. b .

[0049] In order to form a gap, the three-dimensional weaving four-step method includes: the first polygonal core grid edge forming stage, the first polygonal core grid free edge forming stage, the second polygonal core grid edge forming stage, and the second polygonal core grid free edge forming stage. The first and second fabric openings are formed through the first polygonal core grid edge forming stage, the first polygonal core grid free edge forming stage, the second polygonal core grid edge forming stage, and the second polygonal core grid free edge forming stage.

[0050] The first polygonal core grid edge forming stage is used to form the second non-overlapping part in the preform; the first polygonal core grid free edge forming stage is used to form the upper overlapping part in the preform; the second polygonal core grid edge forming stage is used to form the first non-overlapping part in the preform; the second polygonal core grid free edge forming stage is used to form the lower overlapping part in the preform.

[0051] The relationship between the yarn carrier and the completed preform at each stage is as follows: Figure 7 As shown, Figure 7 The columns marked with a, b, and c are the fixed column positions of the yarn carrier.

[0052] For the first polygonal core grid edge forming stage, the column numbers of the fixed columns of the yarn carrier are: column 1, the last column, and all columns whose yarn carrier column numbers X conform to the following formula:

[0053] (X-1) / (2*n t +2) = integer

[0054] For the first polygonal core free edge forming stage, the column numbers of the fixed columns of the yarn carrier are: column 1, the last column, and all columns whose yarn carrier column numbers X conform to the following formula:

[0055] (X-1) / (n t +1) = integer

[0056] For the second polygonal core grid edge forming stage, the column numbers of the fixed columns of the yarn carrier are: column 1, the last column, and all columns whose yarn carrier column numbers X conform to the following formula:

[0057] (X+n t ) / (2*n t +2) = integer

[0058] For the second polygonal core free edge forming stage, the fixed column number of the yarn carrier is the same as that of the first polygonal core free edge forming stage.

[0059] Where, n t The number of yarn carrier columns corresponding to a single free edge in a polygonal core prefabricated body;

[0060] When the second polygonal core free edge forming stage is completed and the first fabric opening is not sealed, a hole size control piece is inserted into the unsealed first fabric opening in that row. The hole size control piece is parallel to the length direction of the first fabric opening.

[0061] When the first polygonal core grid free edge forming stage is completed and the second fabric opening is not sealed, a hole size control piece is inserted into the unsealed second fabric opening in that row. The hole size control piece is parallel to the length direction of the second fabric opening.

[0062] The thickness of the aperture size control sheet is less than 2mm.

[0063] After all the aperture size control pieces are placed into the preform, the length of the relative portions of any two adjacent rows of aperture size control pieces along the weaving direction is L. f The length of the adjacent edges of the aperture size control pieces in each adjacent row on the same column along the weaving direction is L. b ;

[0064] Step 2: After the four-step three-dimensional weaving method is completed, remove the aperture size control piece row by row, and insert the opening auxiliary tool (such as...) that is fixed to the mandrel into the first / second fabric opening of the row where the aperture size control piece was removed. Figure 20 As shown), the opening auxiliary tool fills the core mold into the first fabric opening / second fabric opening and makes the first fabric opening / second fabric opening form the unit cell opening of the polygonal core preform respectively, thus obtaining the polygonal core preform.

[0065] Various fixing methods can be used between the opening auxiliary tool and the core mold, such as gluing or magnetic attraction, or even an integral construction.

[0066] Preferably, the surface of the aperture size control sheet is covered with a release cloth or coated with a release agent to further reduce weaving damage.

[0067] Preferably, the surfaces of the core mold and the opening aid are smooth. More preferably, a release cloth is applied to the surface or a release agent is applied.

[0068] Example 2

[0069] Based on Example 1, such as Figure 8 , Figure 9 and Figure 19 As shown, the aperture size control sheet is a single piece and cannot be deformed during use. Therefore, it needs a certain thickness. This means that the variation caused by the thickness of the aperture size control sheet to the polygonal lattice structure must be considered and compensated for.

[0070] The aperture size control piece 8 includes: a working part 8-2 and mounting parts 8-1 located at both ends of the working part. The working part 8-2 and the mounting parts 8-1 are connected. The working part 8-2 is used to insert the first fabric opening / second fabric opening. The mounting parts 8-1 are used to fix the aperture size control piece in the first fabric opening / second fabric opening after it is inserted into the first fabric opening / second fabric opening. The length of the working part along the weaving direction is W1. A compensation value B is set according to the edge of the aperture size control piece, W1 = LB, where B = B1, B2 or B3; t is the thickness of the working part.

[0071] When the corner of the aperture size control plate is a right angle, B = B1, B1 = Q1 * t * 0.5, where Q1 = 1.41.

[0072] When the corner of the aperture size control plate is chamfered, B = B2, B2 = Q2 * t * 0.5, where Q2 is the sine of the chamfer taper C (i.e., for a chamfer taper of 60 degrees, Q2 is 2).

[0073] When the corner of the aperture size control plate is rounded, B = B3, B3 = Q3*(tr), where r is the radius of the rounded corner. When the radius of the rounded corner r is less than or equal to 0.5t, Q3 is 1.41; when the radius of the rounded corner r is greater than 0.5t and less than or equal to t, Q3 is 1; when the radius of the rounded corner r is greater than t, Q3 is 0.

[0074] Q1, Q2, and Q3 are all compensation coefficients.

[0075] The length of the mounting section along the weaving direction is W2, such as Figure 8 As shown, when W2 is less than W1, W2 is less than or equal to L. b .

[0076] like Figure 9 As shown, when W2 is greater than W1, 6mm ≤ W2 < 12mm.

[0077] The transition between the installation section and the working section is smooth.

[0078] Example 3

[0079] Based on Example 2, according to the angle θ of the honeycomb core opening, dimensional compensation is performed on the knot lengths of the joint edges and the free edges of the polygonal core preform to reduce dimensional variations after hole enlargement. To ensure that the unit cell opening of the polygonal core preform obtained by the three-dimensional woven polygonal core preform preparation method is as close as possible to the set specifications, it is necessary to enlarge the knot length of the joint edges and reduce the knot length of the free edges.

[0080] When the opening θ of the honeycomb core is an acute angle or a right angle (θ less than or equal to 90 degrees), the change in the length of the polygonal core wall caused by tension can be ignored, and compensation is only made for the difference in the position of the honeycomb core opening. The knot length l of the joint edge in the three-dimensional woven polygonal core prefabrication method... b The length l of the free edge in the method for preparing ' and 3D woven polygonal core lattice preforms f 'as follows:

[0081] l b ′=[k b / (k b -1 / 2)]*l b

[0082] l f ′=[k f / (k f +1 / 2)]*l f

[0083] When the opening θ of the honeycomb core is an obtuse angle or a straight angle (90 degrees < θ ≤ 180 degrees), the change in the length of the polygonal core wall caused by tension needs to be considered, with a compensation value of 1 / 2. Simultaneously, the shortening of the joint edge length caused by the thickness of the unit cell wall must also be considered. The knot length l of the joint edge in the three-dimensional woven polygonal core prefabrication method... b The length l of the free edge in the method for preparing ' and 3D woven polygonal core lattice preforms f 'as follows:

[0084] l b ′=[k b / (k b -1)+(1 / 2*T b ) / k b ]*l b

[0085] l f ′=[k f / (k f +1)]*l f

[0086] When the opening θ of the honeycomb core is greater than 180 degrees, the elongation of the free edge length caused by the thickness of the unit cell wall must also be considered in addition to the obtuse angle. The knot length l of the joint edge in the method for preparing a three-dimensional woven polygonal core preform. b The length l of the free edge in the method for preparing ' and 3D woven polygonal core lattice preforms f 'as follows:

[0087] l b ′=[k b / (k b -1)+(1 / 2*T b ) / k b ]*l b

[0088] l f ′=[k f / (k f +1)-(1 / 2*T b ) / k f ]*l f

[0089] Where, k b k is the number of flower nodes in the associative edge. f For the number of flower nodes on the free side, lb The theoretical value of the knot length of the joint edge in the polygonal core prefabricated body (i.e., the knot length of the joint edge determined according to the specifications of the polygonal core prefabricated body set before weaving), l f T is the theoretical value of the knot length of the free side in the polygonal core preform (i.e., the knot length of the free side determined according to the specifications of the polygonal core preform set before weaving); b This is the wall thickness of the joint edge.

[0090] The honeycomb core opening θ of polygonal core prefabricated structures with different unit cell shapes, such as... Figure 10 and Figure 11 As shown in the figure.

[0091] Example 4

[0092] Based on Example 3, the structural schematic diagram of the opening auxiliary tool is as follows: Figure 12 As shown, it includes: an inlet part 1 and an enlarging part 2. The inlet part 1 and the enlarging part 2 are connected. The inlet part and the enlarging part are arranged along the length direction of the opening auxiliary tool. The rear end of the inlet part is fixed to the front end of the enlarging part. The inlet part is a sheet body with a gradually narrowing width from back to front and the edge of the gradually narrowing width is a smooth line (the smooth line is a straight line or an arc). The thickness of the inlet part is the same as that of the hole diameter control sheet.

[0093] After the guide part enters the first fabric opening / second fabric opening, the plane where the guide part is located is parallel to the length direction of the first fabric opening / second fabric opening; the shape of the rear end face of the enlarged hole part is the same as the shape of the unit cell opening of the polygonal core preform, so that after the guide part carries the enlarged hole part into the first fabric opening / second fabric opening, the shape of the rear end face of the enlarged hole part inside the first fabric opening / second fabric opening is the same as the shape of the unit cell opening (the shape of the rear end face of the enlarged hole part is the same as the shape of the core mold it is fixed in).

[0094] The perimeter of the rear end face of the inlet section is 2L.

[0095] With the centerline of the opening auxiliary tool along its length as the axis, all circumferences of the enlarged hole are the same, 2L.

[0096] The inlet section is located on the plane where the axis is located.

[0097] After the opening auxiliary tool and the core mold 9 are fixed, the length direction of the core mold is parallel to the length direction of the opening auxiliary tool.

[0098] Since the guide section is a single piece, the opening aid is a smooth transitional structure composed of the rear end faces of the guide section and the enlarging section. The edges of the guide section are chamfered or rounded to ensure smooth entry into the first / second fabric opening. The cross-sectional design of the opening aid should follow these rules: the cross-section of the guide section can be semi-circular, semi-elliptical, or rhomboid. Different shapes of the guide section can be selected for different shapes of the unit cell opening. For example, if the unit cell opening is quadrilateral, the guide section is preferably rhomboid; if the unit cell opening is hexagonal, the guide section is preferably semi-circular.

[0099] Example 5

[0100] To realize the method for fabricating three-dimensional woven polygonal core lattice preforms, a design was developed as follows: Figures 13-18 , Figure 21 The three-dimensional woven polygonal core preform forming precision control fixture shown includes: a frame, at least one yarn hanging rod (not shown in the figure), multiple mounting parts, and multiple aperture size control plates. The yarn hanging rod is fixed on the frame, and each mounting part is used to fix one aperture size control plate on the frame during the weaving process.

[0101] The method of using the precision shape control fixture for forming 3D woven polygonal core lattice preforms includes: hoisting the fixture onto the workstation foundation and performing weaving; during the weaving process, inserting a aperture control piece into the fabric opening (first fabric opening / second fabric opening) of the preform formed by weaving, and fixing the aperture control piece to the frame; and removing the aperture control piece after weaving is completed.

[0102] Preferably, each mounting component includes two first connecting rods 6 parallel to the hanging rod, and a first through hole is formed on the frame for the first connecting rod 6 to pass through. The number of first through holes on the frame corresponding to each first connecting rod is two (each end of each first connecting rod passes through one first through hole). The two mounting parts of the aperture size control piece 8 each have a second through hole for the first connecting rod to pass through. Each second through hole of the aperture size control piece passes through one first connecting rod, and each end of the first connecting rod passes through one first through hole.

[0103] Preferably, the frame includes: a height control frame 3, two reference plane frames 4 and four length control positioning belts 5. The two reference plane frames are arranged in parallel and installed at the bottom of the height control frame. Each reference plane frame is vertically fixed with two parallel length control positioning belts. The two reference plane frames are used to fix the yarn hanging rod (the two ends of the yarn hanging rod are fixed to one reference plane frame respectively). The length control positioning belts are used to fix the hole diameter control piece. The first through hole is located on the length control positioning belt.

[0104] Preferably, the height control frame includes a flat component and a fixing component. The fixing component is fixedly mounted on the upper surface of the flat component. The fixing component is used to fix the three-dimensional woven polygon core preform forming precision control tooling to the workstation foundation and suspend it. The flat component is used to install the reference plane frame.

[0105] Preferably, the two length control positioning bands on each reference plane frame are fixed to the reference plane frame by bolts or slide rails (locking).

[0106] Preferably, the two reference plane frames are fixed to the height control frame by bolts or slide rails (locking).

[0107] Preferably, the length control positioning strips on the two reference plane frames are arranged opposite to each other, and the two ends of each first connecting rod are respectively fixed on the two length control positioning strips arranged opposite to each other on the two reference plane frames.

[0108] Preferably, the first through hole of each length control positioning strip is in at least one column.

[0109] Preferably, when L is less than 6mm, there are at least two rows of first through holes in each length control positioning strip, and multiple rows of first through holes on each length control positioning strip are staggered.

[0110] Preferably, when the first through-hole of each length control positioning strip is in a column, the length of each first through-hole on the length control positioning strip along the weaving direction to the first through-hole of the row directly below it is L. h L h =1 / 2*(L b +2*L f ), L b L is the length of the joint edge of the polygonal core prefabricated body. f The length of the free side of the polygon core prefab.

[0111] Preferably, when the first through-hole of each length control positioning strip is in multiple columns, the length along the weaving direction of each first through-hole on the length control positioning strip and the first through-hole with the closest straight-line distance to its adjacent row is L. h (like Figure 18 As shown), L h =1 / 2*(L b +2*L f ), L b L is the length of the joint edge of the polygonal core prefabricated body. f The length of the free side of the polygon core prefab.

[0112] Preferably, it also includes: an initial position control piece 7, which is used to fix two length control positioning strips fixed on the same reference plane frame. The position of the initial position control piece fixed to the length control positioning strips is a fixed position, and the distance between the two length control positioning strips on the same reference plane frame can be quickly determined by fixing the position.

[0113] Preferably, the two reference plane frames share the same initial position control piece or each uses a separate initial position control piece. When the two reference plane frames share the same initial position control piece, a second connecting rod 12 passes through each of the two fixed positions on the initial position control piece, and the two ends of each second connecting rod are respectively fixed to two opposite length control positioning strips on different reference plane frames.

[0114] When W2 is less than W1, W2 is less than or equal to L. b The setting of "" can prevent the aperture size control plate from obscuring the first through hole 10.

[0115] like Figure 19 As shown, the length of the working part of the aperture size control piece perpendicular to the weaving direction is L2, and L2 is greater than or equal to the depth H of the polygonal core preform. The length of the aperture size control piece perpendicular to the weaving direction is L1.

[0116] The diameter of the first through hole is The diameter of the second through hole 11 is

[0117]

[0118] The number of second through holes on each mounting part of the aperture size control plate is preferably three.

[0119] like Figure 16 and Figure 17 As shown, each length control positioning strip can be directly fixed to the reference plane frame. Figure 16 (or fixed to the reference plane frame by other positioning structures) Figure 17 ).

[0120] Example 6

[0121] Define the specifications of the polygonal core preform: the shape of the opening within the unit cell is hexagonal, and the length of the connecting edge of the unit cell is L. b =9mm, the length of the free side of the unit cell is L f =9mm; n t The joint length is 1; the joint length of the flower knot on the joint side is 1.5mm, and the free side flower knot length is 1.5mm. The flower knot width is 1mm. The wall thickness T of the joint side is... b The thickness is 0.2mm. The number of knots k on the joint edge.b There are 6 free edges, and the number of flower nodes k is... f There are 6. A polygonal core preform is prepared according to the preparation method in Example 1. The corners of the edge of the aperture size control sheet are right angles. The length of the working part along the weaving direction is L = 27 mm (i.e., no edge compensation is made for the aperture size control sheet). The thickness t of the aperture size control sheet is 1 mm.

[0122] The geometric area deviation rate of the unit cell in the polygonal core preform obtained according to the preparation method in Example 1 from the set specification is 7.1%.

[0123] Example 7

[0124] A method for preparing a three-dimensional woven polygonal core preform is basically the same as that in Example 6, except that the length of the working part along the weaving direction is W1, W1 = LB, B = B1, B1 = Q1 * t * 0.5, where Q1 = 1.41; the geometric area deviation rate of the unit cell in the obtained polygonal core preform from the set specification is 3.2%.

[0125] Example 8

[0126] A method for preparing a three-dimensional woven polygonal core lattice preform is basically the same as that in Example 7, except that: the knot length of the joint edge in the preparation method of the three-dimensional woven polygonal core lattice preform in Example 7 is taken as the theoretical value of the knot length of the joint edge in the polygonal core lattice preform in this example, and the knot length of the free edge in the preparation method of the three-dimensional woven polygonal core lattice preform in Example 7 is taken as the theoretical value of the knot length of the free edge in the polygonal core lattice preform in this example. The knot length of the joint edge in the preparation method of the three-dimensional woven polygonal core lattice preform in this example is l b The length l of the free edge in the method for preparing ' and 3D woven polygonal core lattice preforms f 'as follows:

[0127] l b ′=[k b / (k b -1)+(1 / 2*T b ) / k b ]*l b

[0128] l f ′=[k f / (k f +1)]*l f

[0129] Where, k b k is the number of flower nodes in the associative edge. f For the number of flower nodes on the free side, l bThe theoretical value for the length of the knot on the joint edge in a polygonal core prefabricated body, l f T represents the theoretical value of the knot length of the free side in a polygonal core lattice prefabricated structure; b This is the wall thickness of the joint edge.

[0130] In this embodiment, l b =1.82mm,l f = 1.28 mm.

[0131] The deviation rate of the geometric area of ​​the unit cell in the polygonal core prefabricated structure obtained in this embodiment from the set specifications is 1.8%.

[0132] Comparative Example 1

[0133] The method for preparing polygonal core lattice preforms is as follows: the specifications of the polygonal core lattice preforms set in this comparative example are the same as those set in Example 6. The only difference is the preparation method. This comparative example directly adopts the core mold forming method (without using a hole size control sheet).

[0134] The geometric area deviation rate between the unit cell inside the polygonal core prefabricated structure obtained in this embodiment and the set specifications is 16%.

[0135] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. The use of an opening-aiding tool in three-dimensional weaving, wherein a preform is woven using a four-step three-dimensional weaving method, and at least one fabric opening is formed on the preform, characterized in that... The fabric opening is a slit with a length of L. The fabric opening is expanded into a cavity of a specific shape by filling the fabric opening with an opening auxiliary tool. The opening auxiliary tool includes an inlet part and an enlarging part connected to the inlet part. The inlet part and the enlarging part are arranged along the length direction of the opening auxiliary tool. The rear end of the inlet part is fixed to the front end of the enlarging part. The inlet part is a sheet with a gradually narrowing width from back to front and the edge of the gradually narrowing width is a smooth line. The perimeter of the rear end face of the inlet section is 2L; With the centerline of the opening auxiliary tool along its length as the axis, all circumferences of the enlarged hole are the same, 2L. The inlet section is located on the plane containing the axis. After the guide section enters the fabric opening, the plane where the guide section is located is parallel to the length direction of the gap; the shape of the rear end face of the enlarged section is the same as the shape cut off on the cavity by the plane perpendicular to the axial direction of the cavity; When the length of the expanded portion is less than the axial length of the cavity, the rear end face of the expanded portion is used to fix it to a mandrel. The mandrel is used to expand the fabric opening into a cavity, and the opening auxiliary tool guides the mandrel to fill the fabric opening. When the length of the expanded portion is greater than or equal to the axial length of the cavity, the expanded portion is used to expand the fabric opening into a cavity. After the opening auxiliary tool and the core mold are fixed, the length direction of the core mold is parallel to the length direction of the opening auxiliary tool.

2. The use according to claim 1, characterized in that, The edges of the inlet section are chamfered or rounded.

3. The use according to claim 1, characterized in that, Smooth lines can be straight lines or curved lines.

4. The use according to claim 1, characterized in that, The thickness of the inlet section is less than 2mm.

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