Fibrous blank with at least one disconnection having an alternation of weaving

Abstract

The invention relates to a fibrous blank (100) produced by weaving and comprising at least one first disconnection (110), the first disconnection (110) separating first and second woven portions (101, 102) in the blank (100), the fibrous blank (100) being characterized in that it has an alternation between a first weaving plane and a second, different weaving plane.

Description

Description Title of the invention: FIBROUS BLANK WITH AT LEAST ONE DELINKAGE PRESENTING AN ALTERNATING WEAVE Technical Field

[0001] The invention relates to a fiber blank having at least one debonding. The invention relates, for example, to a fiber blank intended to form the fiber reinforcement of a turbomachine part, and in particular an inter-blade platform or a turbomachine ring sector. Prior art

[0002] In order to obtain lightweight turbomachine parts with excellent thermomechanical properties, composite material parts are produced in a well-known manner, i.e. parts comprising a fiber reinforcement densified by a matrix. The use of composite materials contributes to optimizing the performance of the turbomachine, in particular by reducing the overall mass of the turbomachine, which contributes to a reduction in fuel consumption and therefore to a significant reduction in pollutant emissions.

[0003] Furthermore, ceramic matrix composite materials can withstand temperatures ranging from 600°C to 1400°C. Due to their better resistance to high temperatures, ceramic matrix composite materials require less cooling. Since this cooling traditionally comes from a tap in the compressor, which impacts the efficiency of the turbomachine, composite materials therefore make it possible to further improve engine efficiency and further reduce fuel consumption.

[0004] In particular, it is known to produce the fibrous blank of the part by three-dimensional weaving on a jacquard-type loom, said blank then being shaped to obtain a fibrous preform of the part to be produced, which will be densified by the matrix.

[0005] The creation of a delinking during the weaving of a fiber blank is well known. Such a delinking makes it possible to separate two portions of the fiber blank, for example by deploying one of the portions of the fiber blank. However, composite material parts comprising such a portion deployed by means of debonding have areas of weakness devoid of fibers and consisting only of matrix, and may have unwanted tensions in the fibers.

[0006] For example, to produce parts comprising a base from which "legs" extend, such as an inter-blade platform or an n-shaped turbine ring sector, a flat fibrous blank is woven according to a conventional weaving plan, leaving gaps. These gaps make it possible to deploy the portions of the blank intended to form the legs, in order to obtain the fibrous preform of the part to be produced.

[0007] However, it is found that in the parts obtained by this process, the edges of the junction between the base and the legs are essentially made of matrix and are not properly reinforced by the fibers, as illustrated in Figure 1 at the level of zones Z1. In addition, the ends of the legs have unequal fiber lengths, some fibers extending beyond the end of the legs while a part of the end of the legs is not properly reinforced by the fibers, some fibers not reaching the end of the legs, as illustrated in Figure 1 at the level of zone Z2. Finally, the operation of deploying the leg portions can generate excessive stresses on the stressed fibers located near the junction between the base and the legs. To remedy these problems, it is possible to carry out crossings of threads at the level of the bottom of the unlinks during the weaving of the blank.Such a solution is proposed in particular in document WO 2013 / 088040. Thus, the crossing of the threads in the areas adjacent to the bottoms of the delinks makes it possible to reinforce them, thus facilitating the deployment of the leg portions. In addition, these crossings of threads make it possible to increase the expansion of the fibrous blank at the junction between the base portion and the leg portions, which makes it possible to have a complete filling of fibers of the junction between the base and the legs.

[0008] However, the multiple bends of the fibers, especially at the two junctions, generate unwanted stresses in the fibers of the final part that belong to both the first leg and the second leg. Statement of the invention

[0009] The main aim of the present invention is therefore to remedy the aforementioned drawbacks by ensuring ease of shaping of the fiber blank while limiting the stresses generated in the fibers of the final part.

[0010] To this end, the invention proposes a fiber blank produced in a single piece by three-dimensional weaving between a plurality of warp threads extending in a longitudinal direction and a plurality of weft threads extending in a transverse direction, the blank comprising at least a first uncoupling extending in the longitudinal direction, the first uncoupling extending from a first longitudinal edge of the fiber blank and separating first and second woven portions in the blank, the blank further comprising a main woven portion devoid of uncoupling and located in the extension of the first and second woven portions in the longitudinal direction,the fibrous blank being characterized in that it has a first weaving plane in which at least a portion of the warp threads of the first and second woven portions cross in the main woven portion in a crossing zone adjacent to the first uncoupling, and a second weaving plane different from the first weaving plane in which the warp threads of the first and second woven portions do not cross in a zone adjacent to the first uncoupling, and in that the fibrous blank has an alternation between the first and second weaving planes in the transverse direction.,

[0011] Thus, the fiber blank according to the invention is particularly easy to shape to obtain a fiber preform of the part to be produced, while limiting the stresses generated in the fibers.

[0012] Indeed, the crossings of threads of the first and second woven portions in the main woven portion make it easier to bend the first woven portion in relation to the second woven portion, or vice versa, because the The change in trajectory of the warp threads is less abrupt and corresponds more to the natural rigidity of the fibers. In addition, these thread crossings allow for an increase in the bulk of the threads in the main woven portion, which allows for more satisfactory fiber reinforcement at the level of the main woven portion in the final piece.

[0013] The alternation of the two weaving planes allows for easy shaping of the fiber blank and satisfactory fiber reinforcement of the junctions between the first and second portions and the main portion. By alternating the weaving planes, friction between the threads during weaving is limited by reducing the contact points. The bulk of the threads within the fiber blank is also limited, as is the rigidity of the blank, further facilitating its shaping.

[0014] Thus, in the second weaving plane, the warp threads of the first woven portion extend in a first part of an area of ​​the main woven portion adjacent to the first unbundling and in which the warp threads of the second woven portion extend in a second part of the area of ​​the main woven portion adjacent to the first unbundling, the first and second parts of the area of ​​the main woven portion adjacent to the first unbundling being distinct.

[0015] According to a particular embodiment of the invention, all of the warp threads of the first and second woven portions cross in the main woven portion in the first weaving plane.

[0016] This ensures a particularly high fiber abundance in the main woven portion, and a relatively smooth trajectory for all the warp threads in the final piece. In addition, by crossing all the warp threads, the path lengths of each warp thread are very similar, which allows for a consistent yarn length at the ends of the first and second portions in the final piece.

[0017] According to another particular embodiment of the invention, the warp threads of the first and second woven portions cross at most once in the main woven portion in the first weaving plane.

[0018] This limits the risk of damage to the threads during weaving by reducing the contact points between the fibers. In addition, it is ensured that the warp threads undergo a limited number of bends to limit the tensions generated in the fibers of the final piece. By crossing the warp threads only once, an optimal bend in the warp threads is achieved, allowing a compromise between ease of shaping the blank and limiting the stresses in the fibers of the final piece.

[0019] According to another particular embodiment of the invention, the first weaving plane comprises a plurality of successive weft columns T 5n with n between 1 and N in the main woven portion, the weft column T 5ibeing the weft column adjacent to the first unlinking, N corresponding to the number of warp threads of the first woven portion crossing warp threads of the second woven portion, so that in the weft column T 5n , n warp threads of the first woven portion cross n warp threads of the second woven portion.

[0020] According to another particular embodiment of the invention, the fibrous blank comprises a second uncoupling extending from a second longitudinal edge of the fibrous blank and separating third and fourth woven portions in the blank, the main woven portion being present between the first and second woven portions on the one hand, and between the third and fourth woven portions on the other hand, at least a portion of the warp threads of the third and fourth woven portions crossing in the main woven portion in a crossing zone adjacent to the second uncoupling in the second weaving plane.

[0021] This particular embodiment makes it possible to produce a fiber blank intended to be deployed to form a fiber preform with a base from which two legs extend. Thus, the crossings of threads of the third and fourth woven portions in the main woven portion make it possible to facilitate the curvature of the third woven portion relative to the fourth woven portion, or conversely, in order to form one of the legs. The alternation of the two weaving planes allows for easy shaping of the fiber blank and satisfactory fiber reinforcement of the junctions between the legs and the base of the final piece, thanks to the alternating crossings between the warp threads.

[0022] Preferably, all of the warp yarns of the third and fourth woven portions intersect in the main woven portion in the second weaving plane. Thus, the path lengths of each warp yarn are very similar, which allows for a consistent yarn length at the ends of the legs in the final piece.

[0023] Preferably, the warp threads of the third and fourth woven portions cross at most once in the main woven portion in the second weaving plane. Indeed, it is desired to avoid, in the final piece, the same fiber being present in both the first leg and the second leg, thus undergoing at least two significant bends and generating significant differences in fiber length at the ends of the legs.

[0024] According to another particular embodiment of the invention, the second weaving plane comprises a plurality of successive weft columns T 6 n with n between 1 and N in the main woven portion, the weft column TÔI being the weft column adjacent to the second unlinking, N corresponding to the number of warp threads of the third woven portion crossing warp threads of the fourth woven portion, so that in the weft column T 6 n, n warp threads from the third woven portion cross n warp threads from the fourth woven portion.

[0025] This ensures a regular crossing of the fibers in the crossing zones, in order to maximize the expansion while limiting the contact points between the fibers, which generate friction and unwanted stiffening of the blank.

[0026] According to another particular embodiment of the invention, the fibrous blank is intended to form the fibrous reinforcement of an n-shaped turbine ring sector. The fibrous blank may also be intended to form the reinforcement fibrous reinforcement of a blade with one or more integrated platforms formed by delinking, or the fibrous reinforcement of an aeronautical engine distributor.

[0027] According to a particular embodiment of the invention, each warp thread of the first woven portion crossing a warp thread of the second woven portion crosses all of the warp threads of the second woven portion crossing warp threads of the first woven portion in the first weaving plane.

[0028] Conversely, each warp thread of the second woven portion crossing a warp thread of the first woven portion may cross all of the warp threads of the first woven portion crossing warp threads of the second woven portion in the first weaving plane.

[0029] According to a particular embodiment of the invention, each warp thread of the first woven portion crosses all of the warp threads of the second woven portion in the first weaving plane. Conversely, each warp thread of the second woven portion can cross all of the warp threads of the first woven portion in the first weaving plane.

[0030] The invention also relates to a method of manufacturing a fiber preform for a composite material part, the method comprising the following steps: - the production of a fiber blank according to the invention, - shaping the fiber blank so as to obtain the fiber preform, said shaping comprising at least the deployment of the first or second woven portion.

[0031] In the case where the fiber blank comprises two debonds as described previously, the shaping of the fiber blank may comprise the deployment of the third or fourth woven portion.

[0032] Furthermore, the invention relates to a method for manufacturing a part made of composite material comprising the following steps: - the production of a fiber preform in accordance with the method for manufacturing a fiber preform according to the invention, and - the densification of said fibrous preform by a matrix to obtain the composite material part.

[0033] Preferably, the part produced is a part made of a ceramic matrix composite material of the CMC type or an organic matrix of the CMO type.

[0034] Finally, the invention relates to a use of the method for manufacturing a composite material part according to the invention, for the manufacture of a turbine ring sector. The invention may also relate to the use of the method for manufacturing a composite material part for the manufacture of a blade with one or more integrated platforms or a distributor. Brief description of the drawings

[0035] [Fig. 1] Figure 1 is a diagram of a part obtained according to a prior art method, representing the organization of the fibers in the matrix.

[0036] [Fig. 2] Figure 2 is a schematic illustration of a fiber blank according to the invention.

[0037] [Fig. 3] Figure 3 is a schematic sectional view of the fiber blank of Figure 2 representing the first weaving plane.

[0038] [Fig. 4] Figure 4 is a schematic sectional view of the fiber blank of Figure 2 representing the second weaving plane.

[0039] [Fig. 5] Figure 5 is a schematic view of a fiber preform obtained by shaping the fiber blank of Figure 2.

[0040] [Fig. 6] Figure 6 is a schematic sectional view of the fiber preform of Figure 5 in a rigid tool.

[0041] [Fig. 7] Figure 7 is a schematic sectional view of the fiber preform of Figure 5 in a tooling comprising a flexible membrane.

[0042] [Fig. 8] Figure 8 is a schematic view of the part obtained by densification of the fiber preform of Figure 5.

[0043] [Fig. 9] Figure 9 is a diagram of a part obtained according to the method of the invention, representing the organization of the fibers in the matrix. Description of the embodiments

[0044] Figures 2 to 4 schematically illustrate an example of a fiber blank 100 according to the invention.

[0045] The fiber blank 100 is produced by three-dimensional weaving between a plurality of layers of warp threads and a plurality of layers of weft threads. By "three-dimensional weaving" or "3D weaving" is meant here a weaving method by which at least some of the warp threads bind weft threads over several weft layers. A reversal of roles between warp and weft is possible.

[0046] The fiber blank may, for example, have a multi-satin weave, i.e., a fabric obtained by three-dimensional weaving with several layers of weft yarns, the basic weave of each layer of which is equivalent to a conventional satin weave but with certain points of the weave that bind the layers of weft yarns together. The fiber blank may also, for example, have an interlock weave, i.e., a fabric obtained by three-dimensional weaving in which each layer of warp yarns binds several layers of weft yarns with all the yarns of the same warp column having the same movement in the plane of the weave. Other three-dimensional weaving methods are conceivable, such as, for example, multi-plain weave weaves. Different multi-layer weaving methods that can be used to form the fiber blank are described in WO 2006 / 136755.

[0047] The fibrous blank 100 is preferably produced using a jacquard type loom. Such a loom is for example described in document FR 3 047 744 A1.

[0048] The fibrous blank 100 extends in the warp direction along a longitudinal direction D L between a first longitudinal edge 100a and a second longitudinal edge 100b. The fibrous blank 100 extends in the weft direction along a transverse direction D T between a first transverse edge 100c and a second transverse edge 100d. The fibrous blank 100 extends in thickness along a thickness direction D Ë perpendicular to the longitudinal directions D L and transverse DT between a first surface 100e and a second surface lOOf.

[0049] The fibrous blank 100 comprises at least a first unbonding 110 and a second unbonding 120 extending in the longitudinal directions D Land transverse DT. Preferably, the first delink 110 and the second delink 120 are present on the same plane perpendicular to the thickness direction D Ë .

[0050] The first uncoupling 110 extends in the longitudinal direction DL from the first longitudinal edge 100a of the fiber blank 100 to a uncoupling bottom 110a. The first uncoupling 110 is open on the first longitudinal edge 100a, that is to say it opens onto the first longitudinal edge 100a of the fiber blank 100. The first uncoupling 110 extends in the transverse direction D T between the first transverse edge 100c and the second transverse edge 100d. Preferably, the first uncoupling 110 is open on the first transverse edge 100c and on the second transverse edge 100d, that is to say that it opens onto the first transverse edge 100c and on the second transverse edge 100d.

[0051] The second disconnection 120 extends in the longitudinal direction D L from the second longitudinal edge 100b of the fiber blank 100 to a decoupling bottom 120b. The second decoupling 120 is open on the second longitudinal edge 100b, that is to say it opens onto the second longitudinal edge 100b of the fiber blank 100. The second decoupling 120 extends in the transverse direction DT between the first transverse edge 100c and the second transverse edge 100d. Preferably, the second decoupling 120 is open on the first transverse edge 100c and on the second transverse edge 100d, that is to say it opens onto the first transverse edge 100c and on the second transverse edge 100d.

[0052] The sum of the lengths of the first and second delinks 110 and 120 along the longitudinal direction DL is less than the total length of the fiber blank 100 along the direction D L. Thus, the fibrous blank 100 comprises a main woven portion 105 having no unbonding. The main woven portion 105 of the fibrous blank 100 extends in the longitudinal direction D L between the bottom 110a of the first uncoupling 110 and the bottom 120b of the second uncoupling 120. The main woven portion 105 of the fibrous blank 100 extends along the transverse direction DT between the first transverse edge 100c and the second transverse edge 100d of the fiber blank 100. The main woven portion 105 of the fiber blank 100 extends along the thickness direction D E between the first surface 100e and the second surface 100f of the fiber blank 100.

[0053] The first delinking 110 separates a first woven portion 101 and a second woven portion 102 of the fibrous blank 100. Thus, the first woven portion 101 of the fibrous blank 100 extends in the longitudinal direction DL between the first longitudinal edge 100a and the main woven portion 105 of the fibrous blank 100. The first woven portion 101 of the fibrous blank 100 extends along the thickness direction D E between the first surface 100e of the fibrous blank 100 and the first debonding 110. Similarly, the second woven portion 102 of the fibrous blank 100 extends in the longitudinal direction DL between the first longitudinal edge 100a and the main woven portion 105 of the fibrous blank 100. The second woven portion 102 of the fibrous blank 100 extends in the thickness direction D E between the second surface 100f of the fibrous blank 100 and the first unbonding 110. Preferably, the first woven portion 101 and the second woven portion 102 of the fibrous blank 100 extend in the transverse direction D Tbetween the first transverse edge 100c and the second transverse edge 100d of the fiber blank 100. Preferably, the first and second woven portions 101 and 102 are only connected to each other by means of the main woven portion 105.

[0054] The second delinking 120 separates a third woven portion 103 and a fourth woven portion 104 of the fibrous blank 100. Thus, the third woven portion 103 of the fibrous blank 100 extends in the longitudinal direction D L between the second longitudinal edge 100b and the main woven portion 105 of the fibrous blank 100. The third woven portion 103 of the fibrous blank 100 extends along the thickness direction D Ebetween the first surface 100e of the fibrous blank 100 and the second unbonding 120. Similarly, the fourth woven portion 104 of the fibrous blank 100 extends in the longitudinal direction DL between the second longitudinal edge 100b and the woven portion main portion 105 of the fiber blank 100. The fourth woven portion 104 of the fiber blank 100 extends along the thickness direction D Ë between the second surface 100f of the fibrous blank 100 and the second unbonding 120. Preferably, the third woven portion 103 and the fourth woven portion 104 of the fibrous blank 100 extend in the transverse direction DT between the first transverse edge 100c and the second transverse edge 100d of the fibrous blank 100. Preferably, the third and fourth woven portions 103 and 104 are only bonded to each other by means of the main woven portion 105.

[0055] The fiber blank 100 comprises, along the transverse direction DT, an alternation between a first weaving plane, illustrated schematically in FIG. 3, and a second weaving plane, illustrated schematically in FIG. 4. The first and second weaving planes are different. The first and second weaving planes of FIGS. 3 and 4 correspond to sections of the fiber blank 100 illustrated in FIG. 2 along planes perpendicular to the transverse direction D. T , and schematically represent the weaving between the warp threads and the weft threads, and the crossings between the warp threads. The weaving plans shown in Figures 3 and 4 are schematic diagrams, and therefore represent a number of warp threads and a number of weft threads lower than the actual numbers of warp threads and weft threads.

[0056] In the first weaving plane of the fiber blank 100 illustrated in Figure 3, first warp threads Cn, C12, C13, Ci 4 bind together the weft threads ti of the first woven portion 101 of the fibrous blank 100, and the second warp threads C15, CIÔ, Ci 7 , Cis binds the weft threads together t 7 of the second woven portion 102 of the fiber blank 100. The first and second warp threads Cn, C12, C13, C14, C15, Ci6, C17, Cis then bind together the weft threads t 5 and to of the main woven portion 105.

[0057] In the foreground weaving example shown in Figure 3, all of the first warp yarns Cn, C12, C13, Ci 4 from the first woven portion 101 cross all of the second warp threads C15, CIÔ, Ci 7, Cis from the second woven portion 102. Thus, all the first or second warp threads have a trajectory of length similar to the trajectories of the other first or second warp threads, which allows a more regular filling of the ends of the legs of the final piece with fibers. It is of course not departing from the scope of the invention if only a part of the first warp threads Cn, C12, C13, C14 from the first woven portion 101 cross the second warp threads C15, Ci6, c i7 , Cis from the second woven portion 102, or if only a part of the second warp threads C15, Ci6, Ci 7 , Cis from the second woven portion 102 cross the first warp threads Cn, C12, C13, C14 from the first woven portion 101.

[0058] The first warp threads Cn, C12, C13, C14 from the first woven portion 101 and the second warp threads C15, Ci6, Ci 7, Cis from the second woven portion 102 cross in a first crossing zone 105a of the main woven portion 105. The first crossing zone 105a comprises at least in part a plurality of weft columns T51, T52, ... T 57 each comprising at least one crossing between a first warp thread Cn, C12, C13, C14 from the first woven portion 101 and a second warp thread C15, Ci6, Ci 7 , Cis from the second woven portion 102. In particular, the first crossing zone 105a extends in the longitudinal direction DL between on the one hand the weft column T51 comprising at least one crossing closest to the first unlinking 110, that is to say closest to the bottom 110a of the unlinking 110, and on the other hand the weft column T 57comprising at least one crossing closest to the second unlinking 120, that is to say closest to the bottom 120b of the unlinking 120, and therefore furthest from the first unlinking 110. The first crossing zone 105a does not comprise all or part of a weft column located between the first unlinking 110 and the weft column T51 closest to the first unlinking 110 comprising at least one crossing, and does not comprise all or part of a weft column located between the second unlinking 120 and the weft column Ts 7 closest to the second disconnection 120 comprising at least one crossing.

[0059] Preferably, the first crossing zone 105a is limited to the reduced area of ​​the main woven portion 105 in which each weft column T 5i to T 57comprises at least one crossing between a first warp thread Cn, C12, C13, C14 from the first woven portion 101 and a second warp thread C15, Ci6, Ci 7 , Cis from the second woven portion 102. Thus, each weft column T 5 I to T 57 present at least in part in the first crossing zone 105a comprises at least one crossing between a first warp thread Cn, C12, C13, C14 from the first woven portion 101 and a second warp thread C15, Ciô, c i7 , Cis from the second woven portion 102.

[0060] In the foreground weaving example illustrated in Figure 3, the first crossing zone 105a of the main woven portion 105 is adjacent to the first unlinking 110, i.e. adjacent to the bottom 110a of the unlinking 110. In particular, this means that the end weft column T51 of the main woven portion 105 closest to the first unlinking 110, i.e. closest to the bottom 110a of the unlinking 110, comprises at least one crossing between a first warp yarn Cn, C12, C13, C14 from the first woven portion 101 and a second warp yarn C15, C16, C17, C18, C19, C20, C21, C22, C23, C24, C25, C26, C27, C28, C29, C30, C31, C32, C33, C34, C35, C36, C37, C38, C39, C40, C41, C42, C43, C44, C45, C46, ​​C47, C48, C49, C50, C51, C52, C53, C54, C55, C56, C57, C58, C59, C60, C61, C62, C63, C64, C65, C66, C67, C68, C69, C70, C71, C72, C73, C74, C75, C76, C77, C78, ​​C79, C80, C81, C82, C83, C84, C85, C86, C87, C88, C89, C90, C91, C92, C93, C94, C95, C96, C97, C98, C99, C9 i7 , Cis from the second woven portion 102. Preferably, the weft columns TÔI to TÔ 7present in the main woven portion 105 closest to the second unlinking 120, that is to say to the bottom 120b of the second unlinking 120, do not have a crossing between a first warp thread Cn, C12, C13, C14 from the first woven portion 101 and a second warp thread C15, Ci6, Ci 7 , Cis from the second woven portion 102.

[0061] Preferably, as illustrated in Figure 3, each first warp yarn C11, C12, C13, C14 crossing a second warp yarn C15, C16, C17 7 , Cis crosses every second warp thread C15 once, Ciô, c i7 , Cis. Conversely, every second warp thread C15, Ci6, Ci 7 , Cis crossing a first warp thread Cn, C12, C13, C14 crosses each first warp thread Cn, C12, C13, C14 once.

[0062] Preferably, as illustrated in Figure 3, the crossing of the first warp threads Cn, C12, C13, c i4from the first woven portion 101 with the second warp threads C15, Ci6, Ci 7 , Cis from the second woven portion 102 is done regularly in the first weaving plane, by first crossing the warp threads closest to the first uncoupling 110, then by progressively crossing warp threads further and further away from the first uncoupling 110. Thus, in the first weft column T51 closest to the first uncoupling 110 belonging to the first crossing zone 105a, a single first warp thread Ci4 from the first portion 101 crosses a single second warp thread C15 from the second woven portion 102: the first warp thread C14 closest to the first uncoupling 110 crosses the second warp thread C15 closest to the first uncoupling 110. In the second weft column T52 closest to the first uncoupling 110 belonging to the first crossing zone 105a, only two first warp threads Ci 4, C13 from the first portion 101 cross only two second warp threads C15, Ci6 from the second woven portion 102: the first warp thread C14 crosses the second warp thread Ci6 and the first warp thread C13 crosses the second warp thread C15. In the third weft column T53 closest to the first unlinking 110 belonging to the first crossing zone 105a, only three first warp threads C14, C13, C12 from the first portion 101 cross only three second warp threads C15, C16, C17 from the second woven portion 102: the first warp thread C14 crosses the second warp thread C17, the first warp thread C13 crosses the second warp thread Ci6 and the first warp thread C12 crosses the second warp thread C15.

[0063] Generally, we denote by T 5nthe n-th frame column of the main portion 105 closest to the first unlinking 110 for n between 1 and N inclusive, N being the number of first wires Cn, C12, C13, C14 crossing second wires C15, Ci6, C17, Cis in the first crossing zone 105a or N being the number of second wires C15, C16, C17, Cis crossing first wires Cn, C12, C13, C14 in the first crossing zone 105a. In the example illustrated in Figure 3, the number N has the value 4. Thus, in each column T 5n , n first warp threads from the first woven portion 101 cross n second warp threads from the second woven portion 102. In the example illustrated in figure 3, for n = N, we have in the fourth column T 54 4 first warp threads Cn, C12, C13, C14 from the first woven portion 101 which cross 4 second warp threads C15, Ci6, C17, Cis from the second woven portion 102.

[0064] Additionally, in each column T 5n , the first warp thread Ci N -i crosses the second warp thread Ci N+ni for i between 0 and n-1 inclusive. Thus, in the example illustrated in Figure 3, in column T52, i.e. n = 2, the increment i = 0 indicates that the first warp thread Ci 4 -o, or Ci 4 , cross the second warp thread Ci 4+ 2-o, or Ci6, and the increment i = 1 clearly indicates that the first warp thread Ci 4 -i, or C13, crosses the second warp thread Ci 4 +2-i, or C15.

[0065] Once the frame column T 5N reached, which corresponds to column T 54in Figure 3, the number of thread crossings per weft column decreases regularly up to the end of the first crossing zone 105a furthest from the first unlinking 110. We denote by Ts N+m the (N+m)-th weft column of the main portion 105 closest to the first unlinking 110 for m between 1 and Nl inclusive, N being the number of first threads Cn, C12, C13, c i4 crossing second wires C15, Ci6, Ci 7 , Cis in the first crossing zone 105a or N being the number of second wires C15, Ci6, Ci 7 , Cis crossing first sons Cn, C12, C13, Ci 4 in the first crossing zone 105a. Thus, in each column T 5 N + m , Nm first warp threads from the first woven portion cross Nm second warp threads from the second woven portion. In the example illustrated in Figure 3, for m = 2, we have in column T 56 2 first warp threads Cn, C12 from the first woven portion 101 which cross 2 second warp threads Ci 7 , Cis from the second woven portion 102.

[0066] Preferably, in the first weaving plane, the first warp threads Cn, C12, C13, c i4 from the first woven portion 101 having been crossed with second warp threads C15, Ci6, Ci 7 , Cis from the second woven portion 102 bind the weft threads t together 4 of the fourth woven portion 104 of the fiber blank 100 and do not bind weft threads ts of the third woven portion 103 of the fiber blank 100, in order to limit the curvatures of these first warp threads C11, C12, C13, Ci 4 which have been crossed. For the same reasons, preferably the second warp threads C15, Ci6, c i7 , Cis from the second woven portion 102 having been crossed with first warp threads Cn, C12, C13, Ci4 from the first woven portion 101 bind together the weft threads ts of the third woven portion 103 of the fiber blank 100 and do not bind weft threads t 4 of the fourth woven portion 104 of the fibrous blank 100.

[0067] In the second weaving plane of the fiber blank 100 illustrated in Figure 4, third warp threads C21, C22, C23, c 74 bind the weft threads together ts of the third woven portion 103 of the fibrous blank 100, and the fourth warp threads C25, C26, C27, C28 bind together the weft threads t 4 of the fourth woven portion 104 of the fiber blank 100. The third and fourth warp threads C21, C22, C23, C24, C25, C26, C27, C28 then bind together the weft threads t 5 and tg of the main woven portion 105.

[0068] In the example of the second weaving plane illustrated in Figure 4, all of the third warp threads C21, C22, C23, C24 from the third woven portion 103 cross all of the fourth warp threads C25, C2g, C27, C28 from the fourth woven portion 104. Thus, all of the third or fourth warp threads have a trajectory of similar length to the trajectories of the other third or fourth warp threads, which allows for more regular filling of the ends of the legs of the final piece with fibers.It is of course not outside the scope of the invention if only a portion of the third warp threads C21, C22, C23, C24 from the third woven portion 103 cross the fourth warp threads C25, C26, C27, C28 from the fourth woven portion 104, or if only a portion of the fourth warp threads C25, C26, C27, C28 from the fourth woven portion 104 cross the third warp threads C21, C22, C23, C24 from the third woven portion 103.

[0069] The third warp threads C21, C22, C23, C24 from the third woven portion 103 and the fourth warp threads C25, C26, C27, C28 from the fourth woven portion 104 cross in a second crossing zone 105b of the main woven portion 105. The second crossing zone 105b comprises at least in part a plurality of weft columns Tgi, T 52 , ... T 57each comprising at least one crossing between a third warp thread C21, C22, C23, C24 from the third woven portion 103 and a fourth warp thread C25, C2g, C27, C28 from the fourth woven portion 104. In particular, the second crossing zone 105b extends in the longitudinal direction D L between on the one hand the frame column Tgi comprising at least one crossing closest to the second unlinking 120, that is to say closest to the bottom 120b of the unlinking 120, and on the other hand the frame column Tg7 comprising at least one crossing closest to the first unlinking 110, that is to say closest to the bottom 110a of the unlinking 110, and therefore the furthest from the second unlinking 120. The second crossing zone 105b does not include all or part of a frame column located between the second unlinking 120 and the frame column TÔI closest to the second unlinking 120 comprising at least one crossing, and does not include all or part of a frame column located between the first unlinking 110 and the frame column T 67 closest to the first disconnection 110 comprising at least one crossing.

[0070] Preferably, the second crossing zone 105b is limited to the reduced area of ​​the main woven portion 105 in which each weft column TÔI to T 67comprises at least one crossing between a third warp thread C21, C22, C23, C24 from the third woven portion 103 and a fourth warp thread C25, C26, C27, C28 from the fourth woven portion 104. Thus, each weft column TÔI to Tô7 present at least in part in the second crossing zone 105b comprises at least one crossing between a third warp thread C21, C22, C23, C24 from the third woven portion 103 and a fourth warp thread C25, C26, C27, C28 from the fourth woven portion 104.

[0071] In the example of a second weaving plane illustrated in FIG. 4, the second crossing zone 105b of the main woven portion 105 is adjacent to the second unlinking 120, i.e. adjacent to the bottom 120b of the unlinking 120. In particular, this means that the end weft column TÔI of the main woven portion 105 closest to the second unlinking 120, i.e. closest to the bottom 120b of the unlinking 120, comprises at least one crossing between a third warp yarn C21, C22, C23, C24 from the third woven portion 103 and a fourth warp yarn C25, C26, C27, C28 from the fourth woven portion 104. Preferably, the weft columns T 5i to T 57present in the main woven portion 105 closest to the first unlinking 110, that is to say to the bottom 110a of the first unlinking 110, do not have a crossing between a third warp thread C21, C22, C23, C24 coming from the third woven portion 103 and a fourth warp thread C25, C26, C27, C28 coming from the fourth woven portion 104.

[0072] Preferably, as illustrated in Figure 4, each third warp yarn C21, C22, C23, C24 crossing a fourth warp yarn C25, C26, C27, C28 crosses a single times every fourth warp thread C25, C26, C27, C28- Conversely, every fourth warp thread C25, C26, C27, C28 crossing a third warp thread C21, C22, C23, C24 crosses every third warp thread C21, C22, C23, C24 once-

[0073] Preferably, as illustrated in Figure 4, the crossing of the third warp threads C21, C22, C23, C24 from the third woven portion 103 with the fourth warp threads C25, C26, C27, C28 from the fourth woven portion 104 is done regularly in the second weaving plane, by first crossing the warp threads closest to the second uncoupling 120, then by progressively crossing warp threads further and further from the second uncoupling 120. Thus, in the first weft column T 6iclosest to the second unlinking 120 belonging to the second crossing zone 105b, a single third warp thread C24 from the third portion 103 crosses a single fourth warp thread C25 from the fourth woven portion 104: the third warp thread C24 closest to the second unlinking 120 crosses the fourth warp thread C25 closest to the second unlinking 120. In the second weft column TÔ2 closest to the second unlinking 120 belonging to the second crossing zone 105b, only two third warp threads C24, C23 from the third portion 103 cross only two fourth warp threads C25, C26 from the fourth woven portion 104: the third warp thread C24 crosses the fourth warp thread C26 and the third warp thread C23 crosses the fourth warp thread C25. In the third column of frame T 63closest to the second unlinking 120 belonging to the second crossing zone 105b, only three third warp threads C24, C23, C22 from the third portion 103 cross only three fourth warp threads C25, C26, C27 from the fourth woven portion 104: the third warp thread C24 crosses the fourth warp thread C27, the third warp thread C23 crosses the fourth warp thread C26 and the third warp thread C22 crosses the fourth warp thread C25.

[0074] In general, Tôn denotes the n-th frame column of the main portion 105 closest to the second unlinking 120 for n between 1 and N inclusive, N being the number of third wires C21, C22, C23, C24 crossing fourth wires C25, C26, C27, C28 in the second crossing zone 105b or N being the number of fourth threads C25, C26, C27, C28 crossing third threads C21, C22, C23, C24 in the second crossing zone 105b. In the example illustrated in Figure 4, the number N has the value 4. Thus, in each column Tôn, n first warp threads from the third woven portion 103 cross n fourth warp threads from the fourth woven portion 104. In the example illustrated in Figure 4, for n = N, we have in the fourth column T 64 4 first warp threads C21, C22, C23, C24 from the third woven portion 103 which cross 4 fourth warp threads C25, C26, C27, C28 from the fourth woven portion 104.

[0075] Furthermore, in each column Tôn, the third warp thread C2 N-Ï crosses the fourth warp thread C2 N+ni for i between 0 and n-1 inclusive. Thus, in the example illustrated in Figure 4, in column TÔ2, i.e. n = 2, the increment i = 0 clearly indicates that the third warp thread C24-0, i.e. C24, crosses the fourth warp thread C24+2-0, i.e. C26, and the increment i = 1 clearly indicates that the third warp thread C24-1, i.e. C23, crosses the fourth warp thread C24+2-1, i.e. 025-

[0076] Once the frame column T 6N reached, which corresponds to column T 6in Figure 4, the number of thread crossings per weft column decreases regularly up to the end of the second crossing zone 105b furthest from the second unlinking 120. We denote by Tô N+m the (N+m)-th weft column of the main portion 105 closest to the second unlinking 120 for m between 1 and N-1 inclusive, N being the number of third threads C21, C22, C23, C24 crossing fourth threads C25, C26, C27, C28 in the second crossing zone 105b or N being the number of fourth threads C25, C26, C27, C28 crossing third threads C21, C22, C23, C24 in the second crossing zone 105b. Thus, in each column Tô N+m, Nm third warp threads from the third woven portion cross Nm fourth warp threads from the fourth woven portion. In the example illustrated in Figure 4, for m = 2, we have in column T 662 third warp threads C21, C22 from the third woven portion 103 which cross 2 fourth warp threads C27, C28 from the fourth woven portion 104.

[0077] Preferably, in the second weaving plane, the third warp threads C21, C22, C23, C24 from the third woven portion 103 having been crossed with fourth warp threads C25, C26, C27, C28 from the fourth woven portion 102 bind together the weft threads t2 of the second woven portion 102 of the fiber blank 100 and do not bind weft threads ti of the first woven portion 101 of the fiber blank 100, in order to limit the curvatures of these third warp threads C21, C22, C23, C24 which have been crossed. For the same reasons, preferably, the fourth warp threads C25, C26, C27, C28 from the fourth woven portion 104 having been crossed with third warp threads C21, C22, C23, C24 from the third woven portion 103 bind together the weft threads ti of the first woven portion 101 of the fiber blank 100 and do not bind weft threads t2 of the second woven portion 102 of the fiber blank 100.

[0078] Preferably, the first plane and the second weaving plane are alternated regularly along the transverse direction DT, in order to facilitate the future shaping of the fiber blank 100 over its entire width along the transverse direction DT. It is of course not outside the scope of the invention if the first plane and the second weaving plane are alternated irregularly along the transverse direction DT. Preferably, a first weaving plane never immediately follows another first weaving plane along the transverse direction D. T . Preferably, a second weaving plane never immediately follows another second weaving plane along the transverse direction D. T .

[0079] Preferably, there is no crossing between the warp threads in the first, second, third and fourth woven portions 101, 102, 103 and 104, in order to limit the curvatures and tensions in the fibers belonging to the fiber blank 100.

[0080] Preferably, the fiber blank 100 according to the invention does not comprise a layer outlet, which means that the sum of the number of layers of warp threads in the first portion 101 and the number of layers of warp threads in the second portion 102 corresponds to the number of layers of warp threads in the main portion 105, and corresponds to the sum of the number of layers of warp threads in the third portion 103 and the number of layers of warp threads in the fourth portion 104.

[0081] Preferably, the fibrous blank 100 corresponds to a fibrous texture "dry", that is to say not impregnated with a resin or the like. The fibrous blank 100 may comprise a plurality of threads of various natures, in particular ceramic or carbon threads or a mixture of such threads. Preferably, the fibrous blank 100 may be made from silicon carbide fibers. Generally, the fibrous blank 100 may also be made from fibers made of the following materials: alumina, mullite, silica, an aluminosilicate, a borosilicate, carbon, or a mixture of several of these materials.

[0082] The fibrous blank 100 thus obtained is then shaped in order to obtain a fibrous preform 10, as illustrated in FIG. 5, by separating the first and second woven portions 101 and 102 by means of the first unlinking 110 and by separating the third and fourth woven portions 103 and 104 by means of the second unlinking 120. This shaping operation is greatly simplified on the one hand by means of the crossings of warp threads in the main woven portion 105 near the bottom 110a and 120b of the unlinkings 110 and 120 and on the other hand by means of the alternation of the location of the crossing zone 105a or 105b of the main woven portion 105 between the first and second weaving planes.

[0083] In the example illustrated in Figures 5 to 9, it is desired to produce a part 1 in the shape of n (pi), comprising a base 2 from which a first leg 3 and a second leg 4 extend. The part 1 is preferably a turbine ring sector, or an inter-blade platform. It is of course not departing from the scope of the invention if it is desired to produce another part in composite material from a fiber blank according to the invention.

[0084] Thus, in order to form a fibrous preform 30 of the first leg 3, intended to form the fibrous reinforcement of said first leg 3, the first woven portion 101 of the fibrous blank 100 is deployed to arrange it perpendicular to the second woven portion 102 and to the main woven portion 105. In order to form a fibrous preform 40 of the second leg 4, intended to form the fibrous reinforcement of said second leg 4, the third woven portion 103 of the fibrous blank 100 is deployed to arrange it perpendicular to the fourth woven portion 104 and the main woven portion 105. Finally, a fibrous preform 20 of the base 2 is formed by the second woven portion 102, the fourth woven portion 104 and the main woven portion 105 of the fibrous blank 100.

[0085] The fiber preform 10 illustrated in FIG. 5 thus comprises the base preform 20, the preform of the first leg 30 extending from the base preform 20 and the preform of the second leg 40 extending from the base preform 20.

[0086] Preferably, the length and width of the base preform 20, the length of the leg preforms 30 and 40, and the spacing between the two leg preforms 30 and 40 of the fiber preform 10 correspond substantially respectively to the length and width of the base 2, to the length of the legs 3 and 4, and to the spacing between the two legs 3 and 4 of the part 1 to be obtained, illustrated schematically in FIG. 8.

[0087] Once the fibrous preform 10 has been obtained, said preform 10 is densified by a matrix to obtain the part 1 comprising a fibrous reinforcement constituted by the preform 10.

[0088] The fibrous preform can be consolidated or densified in a well-known manner by gaseous means by chemical vapor infiltration of the matrix, called "CVI". The fibrous preform corresponding to the fibrous reinforcement of the part to be produced is placed in an oven into which a reaction gas phase is admitted. The pressure and temperature prevailing in the oven and the composition of the gas phase are chosen so as to allow the diffusion of the gas phase within the porosity of the preform to form at least part of the matrix by deposition, at the heart of the material in contact with the fibers, of a solid material resulting from a decomposition of a constituent of the gas phase or a reaction between several constituents, unlike the pressure and temperature conditions specific to CVD ("Chemical Vapor Deposition") processes which exclusively lead to a deposition on the surface of the material.The formation of a SiC matrix can be achieved with methyltrichlorosilane (MTS) yielding SiC by decomposition of MTS.

[0089] A densification combining gas and liquid routes can be used in a well-known manner to facilitate implementation and limit costs and manufacturing cycles while obtaining satisfactory characteristics for the intended use. In this configuration, a consolidation of the fiber preform is carried out by gas as described above, then an impregnation of the fiber preform is carried out with a suspension or slip ("slurry cast") containing for example SiC particles and organic binders, followed by infiltration with liquid silicon ("melt infiltration"). The densification can be carried out in a well-known manner by resin injection molding, or "Resin Transfer Molding" (abbreviated "RTM") in English, or by injection molding of a suspension, or "Slurry Transfer Molding" (abbreviated "STM") in English.As in the example illustrated in Figure 6, the fibrous preform 10, previously consolidated by gas or not, is arranged in a cavity defined by a first part 61 and a second part 62 of a mold 60. The cavity has the shape of the part to be manufactured, the latter having at least generally the shape of the part 1 to be manufactured.

[0090] Conventionally, a slip 6 loaded with matrix precursor particles or a resin is injected into the cavity receiving the fiber preform 10, in order to pass through said fiber preform 10 by applying a pressure gradient P. The mold 6 into which the injection of the slip 6 is carried out comprises a filter 63 at the outlet orifice of the slip 6 in the mold 60, thus making it possible to retain any matrix precursor particles in the mold 60 and to impregnate the fiber preform 10 as the matrix precursor particles are deposited in the mold 60 in the case of a slip.

[0091] Densification can also be achieved in a well-known manner by membrane injection, as illustrated in Figure 7. This injection method allows complete control of the quantity of resin or slip injected, thus ensuring a precise and suitable fiber volume ratio. Consequently, the mechanical characteristics of the part thus manufactured are improved, with low variability from one part to another.

[0092] The fibrous preform 10 intended to form the fibrous reinforcement of the part 1 is arranged in a mold 70. In particular, the fibrous preform 10 can be arranged directly on the lower face of the impregnation chamber 71. This lower face of the impregnation chamber 71 can comprise a filter (not shown in FIG. 7).

[0093] The mold 70 comprises on the one hand an impregnation chamber 71 in which the fiber preform 10 is arranged in order to be densified by a matrix by the injection of an impregnation fluid 8, and on the other hand a compaction chamber 72 in which a compression fluid 9 is injected in order to apply pressure to the preform 10 during its densification by the matrix. The impregnation chamber 71 and the compaction chamber 72 are separated by a flexible membrane 73. The membrane 73 makes it possible to apply pressure to the fiber preform 10 installed in the impregnation chamber 71, the compression fluid 9 applying a pressure Q to the membrane 73 which deforms and thus in turn applies pressure to the fiber preform 10.

[0094] Preferably, and as illustrated in FIG. 7, the membrane fits the leg preforms 30 and 40 of the fiber preform 10 and the surface of the base preform 20 located between the leg preforms 30 and 40, while the surface of the base preform 20 opposite the leg preforms 30 and 40 rests against one of the walls of the impregnation chamber 71, opposite the membrane 73. An insert 74 can be used to facilitate the impregnation of the fiber preform 10 of the part 1. As shown in FIG. 7, it is possible, for example, to inject a resin 8 through an inlet opening into the impregnation chamber 71, and to inject the compression liquid 9 through an inlet opening into the compaction chamber 72.

[0095] Depending on the size, thickness and shape of the part 1 to be manufactured, a different injection sequence for the compression and impregnation fluids will be preferred.

[0096] The compression fluid, for example water, is injected into the compaction chamber so as to exert pressure on the flexible membrane. The flexible membrane thus applies pressure to the fiber preform, allowing the impregnation fluid to penetrate into said preform.

[0097] The preform is then subjected to heat treatment while the pressure exerted by the membrane is maintained, in order to form a matrix in the porosities of the fibrous preform.

[0098] When the densification step is completed, a composite material part 1 is obtained, as illustrated in Figures 8 and 9, the fiber reinforcement of which is constituted by the fiber preform 10 and the shape of which corresponds generally to the part 1 to be manufactured. A trimming or light machining step can be carried out on the part produced to obtain the part 1 to be produced. In addition, other elements can be mounted or welded onto the part produced to obtain the part 1 to be produced.

[0099] The part obtained may be a part made of ceramic matrix composite (CMC) or organic matrix composite (OMC). Preferably, the composite part obtained is a part made of ceramic matrix composite (CMC) of the SiC / SiC type.

[0100] Figure 9 illustrates the distribution of the fibers in the matrix in the part obtained by the method of the invention, the fibers crossing in zone Z3 and not crossing in zone Z4. As illustrated in Figure 9 at zone Z5, the fibers of the part obtained 1 fill the angles between the base 2 and the legs 3 and 4 well. The improvement compared to a part obtained according to the method of the prior art, as illustrated in Figure 1, is notable.

[0101] The expression "between ... and ..." must be understood as including the limits.

Claims

Claims

1. Fibrous blank (100) produced in a single piece by three-dimensional weaving between a plurality of warp threads extending in a longitudinal direction (D L ) and a plurality of weft threads (ti, t2, ts, , ts, tô) extending in a transverse direction (D T ), the blank (100) comprising at least a first uncoupling (110, 120) extending in the longitudinal direction (DL), the first uncoupling (110) extending from a first longitudinal edge (100a) of the fibrous blank (100) and separating first and second woven portions (101, 102) in the blank (100), the blank (100) further comprising a main woven portion (105) devoid of uncoupling and located in the extension of the first and second woven portions (101, 102) in the longitudinal direction (D L), the fibrous blank (100) being characterized in that it has a first weaving plane in which at least part of the warp threads (en, C12, C13, Ci 4 , Here 5 , Ci6, Ci?, Cis) of the first and second woven portions (101, 102) cross in the main woven portion (105) in a crossing zone (105a) adjacent to the first unlinking (110), and a second weaving plane different from the first weaving plane in which the warp threads (en, C12, C13, Ci 4 , Here 5 , CIÔ, Ci 7 , Cis) of the first and second woven portions (101, 102) do not cross in an area adjacent to the first unbonding (110), and in that the fibrous blank (100) has an alternation between the first and second weaving planes in the transverse direction (D T ).

2. A fibrous blank (100) according to claim 1, wherein all of the warp yarns (C12, C13, C14, C15, C16, C17, C18, C19, C20, C21, C22, C23, C24, C25, C26, C27, C28, C29, C30, C31, C32, C33, C34, C354 , C15, Ci6, Ci 7 , Cis) of the first and second woven portions (101, 102) intersect in the main woven portion (105) in the first weaving plane.

3. A fibrous blank (100) according to claim 1 or 2, wherein the warp yarns (C12, C13, C14, C15, C16, C17, C18, C19, C20, C21, C22, C23, C24, C25, C26, C27, C28, C29, C30, C31, C32, C33, C34, C3 4 , C15, Ci6, Ci 7 , Cis) of the first and second woven portions (101, 102) intersect at most once in the main woven portion (105) in the first weaving plane.

4. A fibrous blank (100) according to any one of claims 1 to 3, wherein the first weaving plane comprises a plurality of successive weft columns T 5n (T 5 I, T52, T53, T 54 , T 55 , T 5 6, T 57 ) with n between 1 and N in the main woven portion (105), the weft column T 5ibeing the weft column adjacent to the first unlinking (110), N corresponding to the number of warp threads (en, C12, C13, c i4 ) of the first woven portion (101) crossing warp threads (C15, Ci6, C17, Cis) of the second woven portion (102), so that in the weft column T 5n , n warp threads (in, C12, C13, c i4 ) of the first woven portion (101) cross n warp threads (C15, Ci6, C17, Cis) of the second woven portion (102).

5. A fibrous blank (100) according to any one of claims 1 to 4, the fibrous blank (100) comprising a second uncoupling (120) extending from a second longitudinal edge (100b) of the fibrous blank (100) and separating third and fourth woven portions (103, 104) in the blank (100), the main woven portion (105) being present between the first and second woven portions (101, 102) on the one hand, and between the third and fourth woven portions (103, 104) on the other hand, at least a portion of the warp threads (C21, C22, C23, C2 4 , C25, C26, C27, C28) of the third and fourth woven portions crossing in the main woven portion (105) in a crossing zone (105b) adjacent to the second unlinking (120) in the second weaving plane.

6. A fibrous blank (100) according to claim 5, wherein the second weaving plane comprises a plurality of successive weft columns T 6 n (T 6 I, T 62 , T 63 , T 64 , T 65 , T 66 , T 67 ) with n between 1 and N in the main woven portion (105), the weft column TÔI being the weft column adjacent to the second unlinking (120), N corresponding to the number of warp threads (C21, C22, C23, C2 4 ) of the third woven portion (103) crossing warp threads (C25, C26, C27, C28) of the fourth woven portion (104), so that in the weft column Tôn, n warp threads (C21, C22, C23, C2 4 ) from the third woven portion (103) cross n warp threads (C25, C26, C27, C28) of the fourth woven portion (104).

7. A fibrous blank (100) according to claim 5 or 6, the fibrous blank (100) being intended to form the fibrous reinforcement of an n-shaped turbine ring sector.

8. A fibrous blank (100) according to any one of claims 1 to 7, wherein each warp yarn of the first woven portion (101) crossing a warp yarn of the second woven portion (102) crosses all of the warp yarns of the second woven portion (102) crossing warp yarns of the first woven portion (101) in the first weaving plane.

9. A fibrous blank (100) according to any one of claims 1 to 8, wherein each warp yarn of the first woven portion (101) crosses all of the warp yarns of the second woven portion (102) in the first weaving plane.

10. A method of manufacturing a fiber preform (10) for a composite material part, the method comprising the following steps: - the production of a fibrous blank (100) according to any one of claims 1 to 9, - shaping the fibrous blank (100) so as to obtain the fibrous preform (10), said shaping comprising at least the deployment of the first or second woven portion (101).

11. Method for manufacturing a part (1) made of composite material comprising the following steps: - producing a fiber preform (10) in accordance with the method for manufacturing a fiber preform according to claim 10, and - densification of said fibrous preform (10) by a matrix to obtain the part (1) in composite material.

12. Use of the method according to claim 11, for the manufacture of a turbine ring sector.

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