CN119194712A

CN119194712A - A locally reinforced three-dimensional woven profile preform and preparation method thereof

Info

Publication number: CN119194712A
Application number: CN202411518728.3A
Authority: CN
Inventors: 张欢; 荆云娟; 韦鑫; 董经经; 张艺会; 王业宝
Original assignee: Shaanxi Yuanfeng New Materials Technology Co ltd
Current assignee: Shaanxi Yuanfeng New Materials Technology Co ltd
Priority date: 2024-10-29
Filing date: 2024-10-29
Publication date: 2024-12-27

Abstract

The present invention provides a locally enhanced three-dimensional woven profile preform, the three-dimensional woven profile preform is an I-shaped structure, including a web, an upper flange and a lower flange, the upper flange length is 35-45mm, the lower flange length is 35-45mm, the upper flange width is 110-130mm, the lower flange width is 110-130mm, the flange thickness is 2.5-3.5mm, the web length is 95-105mm, the web width is 110-130mm, and the web thickness is 5-7mm. The present invention performs weft yarn enhancement, normal yarn and weft yarn composite enhancement on the basis of the special position and connection position structure of the profile component, and solves the problem of weak component flange performance and connection performance between the flange and the web by locally enhancing.

Description

Locally reinforced three-dimensional woven profile prefabricated body and preparation method thereof

Technical Field

The invention relates to the technical field of textile methods, in particular to a partially reinforced three-dimensional woven section bar preform and a preparation method thereof.

Background

Three-dimensional woven structure preforms are typically composed of two systematic yarns, a binder warp yarn and a weft yarn. The binding warp yarn connects the layers of the preform along the forming direction of the preform, the yarn is in a sine curve state in the preform, and the weft yarn is in a straight line state in the preform perpendicular to the forming direction of the preform when no load exists. The structural designability is strong, the T-shaped, I-shaped, ten-shaped and other sectional materials are easy to prepare, the current more braiding methods are to arrange gauze carts according to the shapes of the sectional materials, the sectional materials are directly molded after braiding, and the greatest disadvantage of the mode is that the sectional materials are easy to be limited by heald frames and heald eyes, and the sectional materials with larger sizes cannot be continuously braided.

In order to solve the problem, a flattening and reducing weaving mode is adopted, namely, the flange part of the section bar is flattened to form a regular shape with the web plate, and the flange part is unfolded to restore the shape of the section bar after weaving is completed according to the regular shape. The forming mode solves the problem of limited size of the section bar, but obvious grooves appear at the expansion positions of the web plate and the flange, so that the partial weak sections of the prefabricated body are formed, and structural failure is easy to occur in the service process. Therefore, there is a need for a method of producing a preform with a local reinforcing effect.

Patent CN 101775683A discloses a normal reinforcing 2.5D fabric and a weaving method thereof, the fabric comprises a warp yarn system and a weft yarn system, and the warp yarn system and the weft yarn system are interwoven into a layer-by-layer angle interlocking structure, which is characterized by further comprising a normal yarn system, the normal yarn system is perpendicular to the interweaved warp yarn system and weft yarn system, penetrates through the thickness of the fabric and is clamped by adjacent warp yarns and weft yarns, so that the normal reinforcing 2.5D fabric is formed. The weaving method of the fabric is characterized in that a normal yarn system is added on the basis of the existing 2.5D fabric weaving method, normal yarns are vertically introduced between adjacent warp yarn columns by a yarn guiding device line by line along the weft yarn direction according to a certain introduction mode, penetrate through the thickness direction of the fabric and are clamped by the adjacent weft yarn columns, the weaving of the 2.5D fabric is realized, the specific process steps comprise initial yarn arrangement, opening movement, weft yarn introduction, normal yarn introduction, secondary opening movement, weft yarn introduction, and repeating the three steps to obtain the normal reinforced 2.5D fabric. The technology adds a weft normal yarn system on the basis of layer-by-layer angle interlocking to form a normal reinforcement 2.5D fabric, wherein the normal yarn plays a role of binding warp yarns in the thickness direction. Although the composite material made of the normal reinforced 2.5D fabric has higher interlayer (normal) connection strength and improves warp compression resistance, the buckling degree of the fiber is a key factor influencing compression resistance and bending performance, warp buckling is a rule that the warp and weft buckling wave heights are constant when the fabric bears load, the warp buckling is increased when the warp buckling is decreased, the originally straightened weft buckling occurs at the moment, the contribution strength is greatly reduced, the weft density is usually smaller than warp density, the weft compression resistance and bending performance of the 2.5D preform reinforced composite material are far inferior to those of warp, and the warp and weft compression strength and bending strength of the 2.5D preform reinforced composite material are unbalanced. In the embodiment of the patent, weft normal yarns are introduced between warp columns by using a normal opening device in a winding mode or an implantation mode, the opening device enables the warp to open column by column, and normal yarns are sequentially and vertically introduced between adjacent warp yarns.

The design and weaving of I-shaped three-dimensional woven fabric (DOI: 10.19670/j.cnki.dlgydxb.2019.0311) adopts a flattening reduction method to design and weave the I-shaped three-dimensional woven fabric, and the result shows that the flattening reduction weaving method is simple and effective, and solves the problem that the web height of the common I-shaped three-dimensional woven fabric is limited by the number of heald frames in the weaving process to a certain extent. But wherein the upper flange, the lower flange and the web plate of the I-shaped are designed by adopting an angle interlocking structure. The design has the defects that the connection positions of the upper flange and the lower flange and the web plate are uneven, obvious grooves exist, and the binding strength is insufficient. In addition, the upper flange and the lower flange generate larger moment of inertia in the use process of the profile except for better compression resistance, and the profile is required to be capable of effectively resisting bending moment, if shallow cross-bending connection structures are used at all parts, the upper flange and the lower flange form local weak joints, the mechanical enhancement effect of key parts is not achieved, and the performance stability of the parts in the use process is seriously affected.

Based on the above, the invention provides a preparation method of a locally reinforced three-dimensional woven profile prefabricated body.

Drawings

FIG. 1 is a flange weave diagram, particularly a shallow cross-linking structure with weft reinforcement;

FIG. 2 is a weave diagram of the connection position of a flange and a web, which is specifically a shallow cross-linking structure of latitudinal reinforcement and normal composite reinforcement;

FIG. 3 is a woven web view, particularly a shallow cross-linked structure;

FIG. 4 is a schematic view of an I-shaped member;

fig. 5 is a diagram showing a flattening reduction knitting method.

Disclosure of Invention

The invention aims to provide a locally reinforced three-dimensional woven section bar preform and a preparation method thereof.

The invention provides a preparation method of a locally reinforced three-dimensional woven section prefabricated body, which comprises the following steps:

further, the three-dimensional woven profile prefabricated body is of an I-shaped structure and comprises a web plate, an upper flange and a lower flange, wherein the upper flange is 35-45mm in length, the lower flange is 35-45mm in length, the upper flange is 110-130mm in width, the lower flange is 110-130mm in width, the flange is 2.5-3.5mm in thickness, the web plate is 95-105mm in length, the web plate is 110-130mm in width, and the web plate is 5-7mm in thickness

Further, the raw material of the preform is Zhongfushenying 3K carbon fiber, and the fiber volume fraction of the preform is 45% +/-5%.

Further, the warp density of the prefabricated body is 8-10 pieces/cm, the weft density of the flange is 6-8 pieces/cm, the weft density of the web is 3-4 pieces/cm, and the row and column numbers are (10-14) row and X (88-130) columns.

Further, the prefabricated body is woven by warps in double strands, wefts are woven by wefts in single strands, the web plate is of a shallow cross-linking structure, the flange is of a shallow cross-linking structure with weft reinforcement, and the connection position of the flange and the web plate is of a shallow cross-linking structure with weft reinforcement and normal composite reinforcement.

Further, the prefabricated body is woven by adopting a flattening reduction method, namely, the flattening of the I-shaped flange and the web are integrally used as flat plates for weaving, the flange is unfolded to restore the I shape after the weaving is completed, the flat plates are formed after the flattening of the I-shaped prefabricated body, and the flat plates are 170-190mm in length, 110-130mm in width and 5-7mm in thickness.

Further, the preform braiding step includes:

(1) Threading, namely threading normal reinforcing yarns at the flange position and the local reinforcing position of the joint, fixing warp yarns on a back beam, and threading normal reinforcing yarns in a first area into heald eyes of a third heald frame and a fourth heald frame firstly and then threading normal reinforcing yarns in two areas on two sides of a flange through a reed and fixing the heald eyes of the fifth heald frame and the sixth heald frame;

(2) Two flanges are woven:

(3) Local reinforcement braiding is carried out by using weft direction and normal direction compound reinforcement, wherein the local reinforcement braiding comprises reinforcement of connecting points and reinforcement after the connecting points;

(4) Normal braiding is started according to the shallow cross-linked structure until the web braiding is finished;

(5) And repeating the reinforcement after connecting points in the steps, the reinforcement of connecting points and the braiding of two flanges to the folded shape of the I-shaped preform, and finishing and restoring the I-shaped shape by a lower machine to obtain the locally reinforced woven I-shaped preform.

Furthermore, the normal threading step comprises the steps of fixing warp yarns on a back beam of loom equipment, penetrating the first heald frame and the second heald frame in sequence according to the sequential threading method, penetrating a reed and fixing the reed on a breast beam. After each drawing-in, two warp yarns penetrate into the same reed eye after penetrating into two adjacent layers of heald eyes of the same heald wire at the same time, and then the two warp yarns sequentially draw-in.

Further, the two flange braiding step includes:

When the first opening is carried out, an upper opening and a lower opening are formed on the first heald frame and below the second heald frame, weft yarns are introduced into the outer layer except the layering part, and beating-up and forming are carried out;

when the heald frames are opened for the second time, the first heald frame and the second heald frame do not move, so that the heald frames are positioned at the horizontal position, weft yarns are introduced into the outer layer except the layering position, and beating-up and forming are carried out;

Forming a next upper opening on the second heald frame under the first heald frame when the third opening is performed, and inserting weft yarns except for an outer layer at the layering position for beating up and forming;

When the heald frame is opened for the fourth time, the first heald frame and the second heald frame do not move, so that the heald frames are positioned at the horizontal position, weft yarns are introduced into the outer layer except the layering position, and beating-up and forming are carried out;

the above is one cycle, and thus, the cycle is repeated 14 times and then the local reinforcement knitting is started.

Further, the reinforcing braiding step before the connection point comprises the following steps:

When the first time is opened, weft yarns are introduced into the outer layers except the layering positions under the first, third and fifth heald frames and the second, fourth and sixth heald frames, and beating-up and forming are carried out;

When the heald frames are opened for the second time, the first heald frame and the second heald frame do not move, so that the heald frames are positioned at the horizontal position, the third heald frame and the fifth heald frame are positioned below, the fourth heald frame and the sixth heald frame are provided with openings, weft yarns are introduced into the outer layer of the layered part, and beating-up and forming are carried out;

Opening for the third time, forming openings on the second, third and fifth heald frames under the first, fourth and sixth heald frames, and inserting weft yarns except the outer layer of the layered part for beating-up and forming;

Opening the fourth time, wherein the first heald frame and the second heald frame do not move, so that the heald frames are positioned at the horizontal position, openings are formed on the fourth heald frame and the sixth heald frame below the third heald frame and the fifth heald frame, weft yarns are introduced into the outer layer of the layering part, and beating-up and forming are carried out;

the above is one cycle, and the enhancement of the connection point is started after 2 times of cycles.

Further, the step of reinforcing and knitting the connection point includes:

when the first time is opened, openings are formed on the first heald frame and the third heald frame and under the second heald frame and the fourth heald frame, weft yarns are introduced layer by layer at the moment, and beating-up and forming are carried out;

the second opening, the first heald frame and the second heald frame do not move, so that the heald frames are positioned at the horizontal position, the third heald frame is arranged below the fourth heald frame, and an opening is formed on the fourth heald frame, weft yarns are introduced layer by layer at the moment, and beating-up and forming are carried out;

Opening for the third time, forming openings on the second and third heald frames under the first and fourth heald frames, introducing weft yarns layer by layer at the moment, and beating up and forming;

Opening for the fourth time, wherein the first heald frame and the second heald frame do not move, so that the heald frames are positioned at the horizontal position, the third heald frame is arranged below the fourth heald frame, and an opening is formed on the fourth heald frame, weft yarns are introduced layer by layer at the moment, and beating up and forming are carried out;

the above is a loop, and the enhancement of the first local position is ended after 2 loops.

The invention has the beneficial effects that:

The invention aims to provide a method for preparing a locally reinforced woven profile preform, wherein a three-dimensional woven structure comprises an angle interlocking structure (also called a 2.5D structure) and a three-way orthogonal structure. Weaving by adopting a multi-heddle eyelet loom, wherein a layer-by-layer angle interlocking structure (figure 1) with weft reinforcement is adopted at the flange position of the section bar, a layer-by-layer angle interlocking structure (figure 2) with warp normal yarns and weft yarns compositely reinforced at the connecting positions of the upper flange and the lower flange and the web plate is adopted, and the rest positions are woven normally according to the layer-by-layer angle interlocking structure (figure 3).

On the one hand, the weft yarn reinforcement mode adopted at the flange position is equivalent to that the weft density is increased to more than one time of the original weft density, the warp and weft density gap is reduced, the contribution of weft yarn to compression resistance and bending performance is greatly improved, the difference of warp and weft properties is reduced, and the warp and weft property stability of the preform is improved.

On the other hand, the weft yarns and the warp normal yarns are added at the connection positions of the upper flange and the lower flange and the web plate, so that the connection positions can be filled and compacted intuitively, in addition, the weft yarns and the weft reinforcing yarns in the warp direction can be respectively bundled by the weft reinforcing yarns matched with the warp normal yarns, the slippage caused by the load of the connection positions is avoided, the influence on warp yarns is avoided, the structure of the connection positions of the flange and the web plate is compact and flat, the contribution of the warp and weft yarns to the local part is uniform and stable, and the purpose of reinforcing the local position of the profile member is achieved.

The invention respectively carries out weft yarn reinforcement and normal yarn and weft yarn composite reinforcement on the basis of the special position and the connecting position structure of the profile member, and solves the problems of weak member flange performance and connection performance between the flange and the web by a local reinforcement mode.

The invention adopts the principle of locally adding weft reinforcing yarns and normal reinforcing yarns, so that the connection positions of the flanges and the web plate are tighter and smoother, the connection force is stronger, and the risks caused by weak bearing parts and weak links of the connection positions of the parts of the profile are greatly weakened. The weft reinforcement can greatly improve the contribution of the weft yarns at the flange positions to the compression resistance and bending performance, reduce the difference of warp and weft properties and increase the stability of the warp and weft properties of the preform. The warp normal yarns can bundle weft yarns and weft reinforcing yarns in the warp direction respectively, the fibers cannot slide due to the load of the connecting position, the warp cannot be influenced, the structure of the connecting position of the flange and the web is compact and flat, and the contribution of the warp and weft yarns to the part is uniform and stable.

The normal yarn reinforcement in the local reinforcement method adopts a mode that the heald frame moves to drive the warp normal yarn to move, and has high efficiency and small abrasion. The binding action of each weft yarn is completed once, and compared with the reinforcing action of the weft yarn, the binding action has high efficiency and reduces the abrasion to the fiber.

Detailed Description

The following description of the present invention will be made clearly and fully, and it is apparent that the embodiments described are some, but not all, of the embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Examples

In this embodiment, as shown in fig. 4, a piece of the prefabricated body is woven, the upper flange length is 40mm, the lower flange length is 40mm, the upper flange width is 120mm, the lower flange width is 120mm, the flange thickness is 3mm, the web length is 100mm, the web width is 120mm, and the web thickness is 6mm.

In a further embodiment, the length of the upper flange of the three-dimensional woven profile prefabricated body with the I-shaped structure can be 35-45mm, the length of the lower flange can be 35-45mm, the width of the upper flange can be 110-130mm, the width of the lower flange can be 110-130mm, the thickness of the flange can be 2.5-3.5mm, the length of the web can be 95-105mm, the width of the web can be 110-130mm, and the thickness of the web can be 5-7mm.

The fiber volume fraction of the preform is 45%, the warp density is 9 roots/cm, the flange weft density is 7 roots/cm, the web weft density is 3.5 roots/cm, and the row and column number is 12 rows multiplied by 108 columns.

In still further embodiments, the warp density is 8-10 per cm, the flange weft density is 6-8 per cm, and the web weft density is 3-4 per cm.

Further, the weft density of the web can be adjusted according to the actual bearing capacity.

The specific braiding steps do not affect the unfolding of the shape.

Adopting medium recovery eagle 3K carbon fiber as raw material, weaving warp yarns in double strands, weaving weft yarns in single strands, and adopting a shallow cross-linking structure as shown in figure 3;

the flanges are of shallow cross-linking structures with latitudinal reinforcement, as shown in fig. 1;

the connection position of the flange and the web is a shallow cross-linking structure of latitudinal reinforcement and normal composite reinforcement, as shown in figure 2.

Braiding by adopting a flattening reduction method, namely flattening the I-shaped flange and integrally using the web plate as a flat plate for braiding, as shown in figure 5;

The braiding is completed with the flanges deployed back into the shape as shown in fig. 4.

The implementation precondition is:

Because the flat plate is woven by adopting a flattening reduction method, the length of the flat plate (flat plate shape after flattening) is 180mm, the width is 120mm, and the thickness is 6mm.

In still further embodiments, the plate may also have a length of 170-190mm, a width of 110-130mm, and a thickness of 5-7mm.

The embodiment adopts a warp knitting method, and warp yarns are distributed in the length direction, so that the flanges and the web are more in warp and weft interweaving points and strong in connecting force.

(1) The flange position reinforcing structure is designed to ensure the compression resistance and bending performance of the flange in the actual working condition, and the part of the structure is required to be reinforced, and the design structure is layer-by-layer angle interlocking weft reinforcement, as shown in figure 1.

(2) The web and flange connection position reinforcing structure is designed in such a way that the web and flange connection position belongs to local weak joints, the reinforcing design is needed for the part of the structure, and the design structure is layer-by-layer angle interlocking weft-added reinforcing addition reinforcing, as shown in figure 2.

(3) The design of the technological parameters of the local reinforcing position is that the I-shaped local reinforcing position is at the flange position and the connecting part of the web plate and the flange, and the total is three parts.

Accordingly, the specific preparation steps of a locally reinforced three-dimensional woven profile preform in this embodiment are as follows:

(1) The warp density at the flange position is 9 pieces/cm, the weft density is 7 pieces/cm, the weaving is completed according to the length of the flange, the warp density at the connecting position of the web plate and the flange is 18 pieces/cm, the weft density is 7 pieces/cm, 4 wefts are woven at the two connecting positions respectively, wherein the two wefts are distributed at one side of the web plate at the connecting position and are distributed at one side of the flange at the connecting position, the total number of 1296 warps is fixed on a back beam of loom equipment, and the warps sequentially penetrate into the first heald frame and the second heald frame according to a sequential threading method and then pass through a reed and then are fixed on a breast beam. After each drawing-in, two warp yarns penetrate into the same reed eye after penetrating into two adjacent layers of heald eyes of the same heald wire at the same time, and then the two warp yarns sequentially draw-in.

The loom apparatus may be a 2.5D loom or a flat loom, and the object of the present invention can be achieved without limiting the type of loom, and a 2.5D loom is used in this embodiment.

(2) And the normal direction reinforcing yarns are penetrated into the third heald frame and the fourth heald frame at local reinforcing positions (flange positions and connecting positions), 107 warp yarns are totally penetrated into the normal direction reinforcing yarns, the first area normal direction reinforcing yarns penetrate into heald eyes of the third heald frame and the fourth heald frame, and then penetrate through the reed to be fixed on the breast beam.

Because two flanges exist at one connecting position, each flange is provided with reinforcing yarns, the normal reinforcing yarns of two areas are required to be worn, the second area is consistent with the first area in a wearing way, and the heald eyes of the fifth heald frame and the sixth heald frame are penetrated.

(3) Two flanges are woven:

The local reinforcement knitting comprises reinforcement of connecting points and reinforcement after connecting points, and the knitting rule is different from that of normal knitting by performing weft addition and composition reinforcement.

(7) Enhancement before the connection point:

And opening the fourth time, wherein the first heald frame and the second heald frame do not move, so that the heald frames are positioned at the horizontal position, openings are formed on the fourth heald frame and the sixth heald frame below the third heald frame and the fifth heald frame, and weft yarns are introduced into the outer layer of the layered part for beating-up and forming.

(8) Enhancement of connection point:

(9) And (5) starting normal knitting according to the shallow cross-linked structure until the web knitting is finished.

(10) And (3) repeating the steps (8), (7) and (6) until the required length is reached (the shape of the folded H-shaped prefabricated body), and finishing and restoring the H-shaped shape by a machine to obtain the locally reinforced woven H-shaped prefabricated body.

The local position of the section bar is further connected and filled by adding weft reinforcing yarns and normal reinforcing yarns, the performance stability of the local position, the compactness and the flatness of the connecting point are structurally enhanced, and the compactness and the strength of the local position of the section bar and the connecting position of each part are enabled to meet the actual demands by setting proper densities of the weft reinforcing yarns and the normal reinforcing yarns.

The invention mainly increases the weft-direction reinforcing yarns through the local positions of the sectional materials and increases the weft-direction addition to the composite reinforcing yarns through the connecting positions, thereby realizing the structural reinforcement of the yarns at the local positions, enhancing the flatness and the compactness of the parts, and the operation method of the invention has complete regularity, no free play space and uniqueness and greatly reduces the operation difficulty by adding the weft-direction yarns and the normal yarns at the local positions of the prefabricated body. The profile component is widely applied to various fields of national defense science and technology, aerospace, transportation, biomedical treatment, sports equipment, chemical equipment and the like, wherein the 'I' -shaped prefabricated body has great demand on connecting pieces such as a military and civil satellite switching frame, a truss and the like in the space field, and the 'I' -shaped component and the assembly component are more applied to the star cloud and star net.

It should be finally understood that the foregoing embodiments are merely illustrative of the present invention and not limiting the technical solutions described in the present invention, and it should be understood by those skilled in the art that modifications and equivalent substitutions can be made thereto without departing from the spirit and scope of the present invention, and all such modifications and improvements are intended to be included in the scope of the claims of the present invention.

Claims

1. The three-dimensional woven profile prefabricated body is characterized by being of an I-shaped structure and comprising a web plate, an upper flange and a lower flange, wherein the upper flange is 35-45mm in length, the lower flange is 35-45mm in length, the upper flange is 110-130mm in width, the lower flange is 110-130mm in width, the flange is 2.5-3.5mm in thickness, the web plate is 95-105mm in length, the web plate is 110-130mm in width and the web plate is 5-7mm in thickness.

2. A locally reinforced three-dimensional woven profile preform according to claim 1, wherein the preform is made of medium recovery hawk 3K carbon fibers, and the preform fiber volume fraction is 45% ± 5%.

3. A partially reinforced three-dimensional woven section preform according to claim 1, wherein the preform has a warp density of 8-10 threads/cm, a flange weft density of 6-8 threads/cm, a web weft density of 3-4 threads/cm, and a row/column number of (10-14) rows by x (88-130) columns.

4. The locally reinforced three-dimensional woven section prefabricated body according to claim 1, wherein the prefabricated body is woven by warps in double strands, wefts in single strands, webs are of shallow cross-linking structures, flanges are of shallow cross-linking structures with weft reinforcement, and connection positions of the flanges and the webs are of shallow cross-linking structures with weft reinforcement and normal composite reinforcement.

5. A method for preparing a locally reinforced three-dimensional woven profile prefabricated body according to any one of claims 1-4, wherein the prefabricated body is woven by adopting a flattening reduction method, i.e. an I-shaped flange is flattened and integrally woven with a web plate as a flat plate, the flange is unfolded to restore the I shape after the weaving is completed, the flat plate is formed by flattening the I-shaped prefabricated body, and the flat plate has the length of 170-190mm, the width of 110-130mm and the thickness of 5-7mm.

6. The method of preparing a locally reinforced three-dimensional woven profile preform according to claim 5, wherein said preform braiding step comprises:

(2) Knitting two flanges;

7. The method for preparing a partially reinforced three-dimensional woven profile preform according to claim 6, wherein the normal threading step comprises fixing warp yarns on a back beam of a loom device, sequentially threading first and second heald frames according to a sequential threading method, fixing the heald frames on a breast beam after passing through a reed, threading each time, threading two warp yarns into the same reed eye after simultaneously threading two adjacent heald eyes of the same heald, and sequentially threading two warp yarns.

8. A method of preparing a locally reinforced three-dimensional woven profile preform according to claim 6, wherein said two flange braiding steps comprise:

9. A method of preparing a locally reinforced three-dimensional woven-section preform according to claim 6, wherein the reinforcing braiding step prior to the joining point comprises:

10. The method of preparing a locally reinforced three-dimensional woven profile preform of claim 6, wherein the reinforcing braiding step of the connection points comprises: