Fibrous preform comprising a marker pattern

Abstract

FIBER PREFORM COMPRISING A REFERENCE PATTERN The invention relates to a fiber preform for manufacturing a part made of composite material, the fiber preform having a three-dimensional weave comprising a plurality of layers of weft yarns and a plurality of layers of warp yarns extending in a direction perpendicular to the direction of the weft yarns, wherein each weft yarn connects warp yarns of several layers, the weft and warp yarns being woven in a regular weave, the fiber preform being characterized in that it comprises on its surface one or more reference patterns extending in a particular direction (20) of the fiber preform, a reference pattern being created by a local variation of the weave (101, 201, 301). Figure for the abstract: Fig. 3

Description

Title of the invention: Fibrous preform comprising a marker motif technical field

[0001] The invention relates to the field of composite materials and more specifically to fibrous preforms for the manufacture of these materials or to the manufacturing processes of such preforms, or of such materials. Previous technique

[0002] Composite materials have been of increasing technological interest and have seen a wide variety of uses in recent years.

[0003] In particular, organic matrix composites (OMCs) and ceramic matrix composites (CMCs) replace metallic parts in certain sections of turbomachinery. Their use helps to optimize aircraft performance, notably by improving turbomachine efficiency and reducing the overall mass of the turbomachine, thereby significantly reducing harmful emissions (CO, CO2, NOx, etc.).

[0004] The preparation of such materials is generally carried out by forming a matrix within a fibrous preform. The mechanical properties of the final part depend not only on the composition of the preform and the matrix, but also on the weave chosen for the preform, and on the orientation of the fibers within the preform.

[0005] Therefore, the fibrous preform cannot be randomly placed in the manufacturing processes of the part. In particular, it is desirable that the preform can be precisely positioned in a former or in a densification tool. This makes it possible to identify specific areas or directions of the preform, ensuring that the mechanical properties of the final part are as expected.

[0006] Typically, a particular direction of the preform is marked by a tracer thread woven in that direction, the appearance of which differs from the threads of the rest of the preform. This allows for visual identification of a particular direction of the preform, which facilitates the correct positioning of the preform in the tooling.

[0007] To ensure that the appearance of the tracer wires differs from the rest of the preform, the tracer wires are of a different nature than the other wires in the preform. For example, for a preform made of silicon carbide fibers, the tracer wires are generally chosen to be alumina wires.

[0008] While this solution is generally satisfactory, it has nevertheless been observed that the Tracer wires, due to their different nature, do not exhibit the same behavior as the rest of the preform during matrix formation.

[0009] For example, it has been observed that the matrix does not form as well in the area around the tracer wire as on the rest of the preform surface. This poor matrix formation near the tracer wire results in an absence of matrix or a matrix present in a thin layer around the wire, which can lead to non-conformity of the composite part, in particular since an area with less matrix can lead to an area lacking the desired properties.

[0010] On the one hand, it is necessary to have a preform whose orientation can be determined so that it can be precisely placed in a former or densification tool. On the other hand, there remains a need for a preform free from the disadvantages described above and associated with the use of tracer wires in the preform. Description of the invention

[0011] The invention is specifically designed to meet this need.

[0012] To this end, according to a first aspect thereof, the invention proposes a fibrous preform for the manufacture of a part in composite material, the fibrous preform having a three-dimensional weave comprising a plurality of layers of weft yarns and a plurality of layers of warp yarns extending in a direction perpendicular to the direction of the weft yarns, in which each weft yarn binds warp yarns of several layers, the weft yarns and the warp yarns being woven according to a regular weave pattern,

[0013] the fibrous preform being characterized in that it comprises on the surface one or more marker patterns extending in a particular direction of the fibrous preform, a marker pattern being created by a local variation of the weave structure.

[0014] The weave structure of the fibrous preform is very regular to meet aerodynamic requirements. A point variation in the weave structure creates a marker pattern that breaks with the regularity of the rest of the weave.

[0015] The marker pattern makes identifiable the direction in which it extends, without needing to modify the nature of the weft or warp yarns.

[0016] Thus, in such a preform, a particular direction can be identified, without requiring threads of a different nature than the warp or weft threads.

[0017] Furthermore, the local variation in the weave structure of the preform used to create the marker pattern(s) does not adversely affect the properties of the final part. In particular, the densification of the preform by the matrix is ​​not altered by the local variation in weave structure, unlike what can be observed with a marker yarn of a different nature.

[0018] In one embodiment, the local variation of the weave is only carried out on the top layer of the weave, that is to say that only the top layer of the weave comprises a weave different from the rest of the weave.

[0019] The upper layer of the preform is also called the skin layer or skin of the preform.

[0020] In one embodiment, the fibrous preform includes a 3D weave, for example an interlock weave under the skin layer in contact with the free surface.

[0021] By "three-dimensional weaving" or "3D weaving," we mean a weaving method in which at least some of the warp yarns interlock with weft yarns over several weft layers, such as an "interlock weave." "Interlock weaving" refers to a 3D weave structure in which each warp layer interlocks with several weft layers, with all yarns in the same warp layer having the same movement within the plane of the weave.

[0022] A preform according to the invention therefore makes it possible to overcome the disadvantages associated with the use of tracer wires described above.

[0023] In one embodiment of the invention, all the weft yarns, present in the skin of the preform, have the same composition.

[0024] In one embodiment of the invention, all the warp threads, present in the skin of the preform, have the same composition.

[0025] In one embodiment of the invention, all the warp and weft yarns present in the skin of the preform have the same composition.

[0026] In one embodiment, the particular direction identified in a preform of the invention is a weft or warp direction.

[0027] It should be noted that the terms "weft" and "warp" are conventions and should not be interpreted restrictively. In particular, it should be noted that, throughout the text, warp and weft may be interchanged.

[0028] In one embodiment, the marker pattern is a skin thread making a float longer than the floats of the weft or warp threads in a pattern of the regular weave.

[0029] A skin yarn is a weft or warp yarn that is present on the surface of the preform.

[0030] This embodiment is advantageous because it allows for the creation of a reference pattern by modifying the weave of only one hide thread, the rest of the weave remaining identical to a regular weave. This embodiment makes it very easy to identify a warp or weft direction without complicating the weave.

[0031] In such an embodiment, the marker pattern may be a float of a hide thread over a length greater than or equal to two and a half times the length of the elementary pattern of the weave.

[0032] The "elementary motif of the weave", also called "weave ratio", is understood, in the usual sense of the field, as the unit of repetition strictly necessary to reproduce the regular weave structure by periodicity.

[0033] For example, for a twill or satin weave the weave ratio is usually specified, and we speak thus of 2-linked twill, 4-link satin in which the weave ratio is 4, or 8-link satin in which the weave ratio is 8.

[0034] Such a length for the float of a skin thread defining a marker pattern allows the float of the marker pattern to be long enough to be visible to the operator, and is also distinguished from a simple unintentional weaving fault.

[0035] It should be noted that the regular weave may include floats of leather threads, but over a shorter distance than the float of the reference pattern. The leather thread forming a longer float therefore disrupts the periodic repetition of the regular weave to form a reference pattern.

[0036] Such a marker pattern is easily identifiable by an optical device, in particular by a human eye.

[0037] In one embodiment, the local variation of the weave structure may correspond to an inversion of the weaving planes.

[0038] In this embodiment, the reference pattern is a plane of symmetry of the weave structure, and the particular direction is aligned along this plane of symmetry.

[0039] The regular weave comprises a repeating pattern and is produced by successively weaving planes 1, 2 ... n, n+1, n+2 ... and until the periodicity of the regular weave is reached, at which point we start again with plane 1.

[0040] The inversion of the weaving planes is obtained by weaving, from the inversion plane n, the same planes as before, but in descending order.

[0041] That is to say, from the plane n of the inversion, we weave the planes n-1, n-2 ... and so on up to 1 and then we continue by reproducing the periodicity of the regular weave in descending order.

[0042] Such an inversion of the weaving planes creates on the surface of the preform a plane of symmetry of the weave, sometimes called a chevron, which extends in a particular direction of the preform.

[0043] In one embodiment, the preform includes, in addition to an inversion of the weaving planes, a modification of the skin weave compared to the regular weave, making the pattern even more easily identifiable.

[0044] In this embodiment, the weave structure of the preform skin may be different from the rest of the preform, for example a 2-linked 2 twill skin, and the rest of the preform is an interlock weave.

[0045] This embodiment allows for the specific selection of a skin armor in which the local variation will be even more clearly detectable, thus improving the identifying the specific direction.

[0046] In one embodiment, the regular weave is chosen from a satin weave, for example 4 satin, 8 satin, a twill weave, for example 2 twill bound 2 or 4 twill bound 4 or even a plain weave, and the rest of the preform being an interlock type weave.

[0047] In one embodiment, the reference motif may be the superposition of a plane of symmetry and unusual floats.

[0048] This can be achieved by superimposing an inversion of the weaving planes in conjunction with the realization of unusual floats.

[0049] This embodiment makes it possible to obtain an even more singular reference pattern on the surface of the preform.

[0050] In one embodiment, the reference pattern extends over the entire width of the preform in the particular direction.

[0051] In one embodiment, the marker pattern extends over the entire width of the preform in the weft or warp direction. According to another aspect, the invention relates to a method for weaving a fibrous preform in a regular weave structure comprising the three-dimensional weaving of a plurality of layers of weft yarns and a plurality of layers of warp yarns extending in a direction perpendicular to the direction of the weft yarns, in which each weft yarn binds warp yarns of several layers, the method being characterized in that it comprises one or more steps of local variation of the weave structure so as to create a marker pattern on the surface of the fibrous preform, the marker pattern extending in a particular direction of the preform.

[0052] As indicated, the reference pattern allows a particular direction to be identified. A localized weaving error, therefore, cannot be considered a reference pattern, as it does not extend in a particular direction.

[0053] In one embodiment, the local variation of the weave structure includes a step of creating an unusual float of a skin yarn.

[0054] An unusual float is characterized by a surface yarn that does not conform to the regular weave structure and passes over a greater number of surface weft yarns than according to the regular weave.

[0055] In one embodiment, the unusual float is a float with a length greater than or equal to the length of two and a half times the ratio of the regular armor.

[0056] This embodiment makes it possible to ensure a reference pattern that is easily distinguishable from an unintentional, one-off weaving error.

[0057] In one embodiment, the local variation of the weave structure may include a step of reversing the weaving planes.

[0058] This embodiment makes it possible to artificially obtain a plane of symmetry in the weaving structure as a reference pattern.

[0059] In one embodiment, the weaving variation can be achieved by combining an inversion of the weaving planes and the realization of unusual floats, the unusual floats being made in the plane corresponding to the inversion of the weaving planes.

[0060] This makes it possible to obtain a reference pattern that is even more easily identifiable than either of the variations of the armor taken in isolation, and ensures that together the plane of symmetry and the unusual floats clearly identify the same particular direction of the preform.

[0061] According to another aspect of it, the invention relates to a method for manufacturing a part made of composite material comprising at least one step of arranging a preform as described above in a tooling during which one or more particular directions of the preform identified by the preform's reference patterns are aligned in one or more particular directions of the tooling; and a step of forming a matrix in the preform thus arranged in the tooling to form the matrix of the part made of composite material.

[0062] The inventors have found that such a process makes it possible to use the same tools as those already existing and in which it is planned to place the preform in a particular direction, while avoiding the inhomogeneities in the formation of the matrix caused by the presence of the tracer wires usually used to locate a particular direction of the preform.

[0063] Indeed, the marker pattern, which is obtained without variation in the nature of the skin fibers of the preform, does not disrupt the formation of the matrix in the preform.

[0064] In one embodiment, the preform may include weft yarns that are identical or different from the warp yarns.

[0065] In one embodiment, the preform may include warp yarns and weft yarns composed of carbon fibers, glass fibers, alumina fibers, silicon carbide fibers, Kevlar fibers or a mixture of several of these fibers.

[0066] It must be understood that the process of the invention is compatible with any three-dimensional fibrous armor.

[0067] In one embodiment, the part can be a part made of ceramic matrix composite material, or organic matrix composite material.

[0068] In one embodiment, the matrix can be a resin, for example a resin comprising unsaturated polyesters or epoxies.

[0069] In one embodiment, the matrix can be alumina, mullite, silicon carbide, carbon.

[0070] In one embodiment, the matrix formation step can be chosen from among many impregnation processes, including liquid composite molding, also known as "LCM" for the English acronym "Liquid Composite Molding", resin transfer molding, also known as "RTM" for the English acronym "Resin Transfer Molding", high-pressure resin transfer molding, also known as "HP-RTM" for the English acronym "High-Pressure Resin Transfer Molding", compression resin transfer molding, also known as "C-RTM" for the English acronym "Compression Resin Transfer Molding".

[0071] In such a case, the tooling may, for example, be a mold for carrying out one of the processes that has just been described.

[0072] In another embodiment, the matrix formation step can be a molten metal infiltration step (or MI for the English acronym "melt-infiltration").

[0073] In one embodiment, the process may further include a preform consolidation step, for example carried out by chemical vapor infiltration (or CVI for the English acronym "Chemical vapor infiltration") carried out before the matrix formation step, and the tooling may be a conformer.

[0074] In this embodiment, the process may be a process for manufacturing a part made of ceramic matrix composite material comprising at least the following steps:

[0075] - a step of disposing of a preform as described above in a conformer during which one or more particular directions of the preform identified by the preform's reference patterns are aligned in one or more particular directions of the conformer;

[0076] - a preform consolidation step carried out by chemical infiltration in vapor phase; and

[0077] - a step of infiltrating the consolidated preform with molten silicon, for form the matrix in the consolidated preform.

[0078] According to another aspect of it, the invention relates to a part made of composite material comprising a preform as described above.

[0079] For example, such a part made of composite material may be an aeronautical part, for example a turbomachine blade, a turbomachine ring or a turbomachine distributor.

[0080] The composite material part includes on its surface a textile marker that is still visible. Brief description of the drawings

[0081] [Fig.1] Fig.1 schematically represents a weaving armature according to a first embodiment of the invention.

[0082] [Fig.2] Fig.2 schematically represents a weaving armature according to a second embodiment of the invention.

[0083] [Fig.3] Fig.3 schematically represents a weaving structure according to a third embodiment of the invention.

[0084] [Fig.4] Fig.4 schematically represents a weaving structure according to a fourth embodiment of the invention. Description of the implementation methods

[0085] The invention is now described by means of figures, which are provided for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0086] The invention relates to a three-dimensional fibrous preform whose weave structure allows a particular direction to be identified directly, eliminating the need for tracer threads and the associated disadvantages described above.

[0087] In one embodiment, the preform may be a preform of an aeronautical part, for example, a turbomachine blade preform, a turbomachine ring preform, or a distributor preform. Figure 1 schematically represents the weave structure of a fibrous preform 101 according to a first embodiment.

[0088] Conventionally, a weave structure is represented by a grey and white table in which the weft direction is represented horizontally, and the warp direction the vertical direction.

[0089] Each square of a weave represents a crossing between a weft yarn and a warp yarn. A white dot indicates that the weft yarn passes over the warp yarn, while a grey dot indicates that the warp yarn passes over the weft yarn.

[0090] The armor represented schematically by grey and white squares is visible on the surface of the preform, regardless of the nature of the wires.

[0091] Of course, the sharpness of the weave structure on an actual preform is not the same as that represented schematically on the weave structure, but the relief created by the interlacing of the warp and weft threads in an actual preform is easily comparable to the schematic weave structure.

[0092] Thus, the invention is not limited by the nature of the fibers, and the advantages described for the preforms of the invention can be obtained regardless of the nature of the weft or warp yarns.

[0093] For example, the weft and / or warp yarns may be composed of fibers of carbon, glass fibers, alumina fibers, silicon carbide fibers, Kevlar fibers or a mixture of several of these fibers.

[0094] In [Fig. 1], the regular weave shown is a satin of 4 whose elementary pattern 10 is identified in [Fig. 1].

[0095] The precise weave pattern does not affect the proper achievement of the technical effect. Indeed, it is only necessary that the reference pattern be different from the rest of the weave to allow the operator to easily identify a particular direction.

[0096] Weave 101 of [Fig.1] represents 40 warp planes identified by numbers from 1 to 40, and 14 weft planes.

[0097] On [Fig.1], the particular direction 20, here aligned with the fourth plane of the weave, is easily identifiable because it differs visually from the rest of the weave.

[0098] In this case, the weft yarn aligned with the particular direction 20 of the fibrous preform produces unusual floats, which create marker patterns aligned with the weft direction.

[0099] It will be noted that the elementary motif 10 includes regular floats, on [Fig.1], floats of 3, characterized by a succession of 3 grey squares representing a weft yarn passing over 3 warp yarns in succession before being taken up under a warp yarn (white square).

[0100] In [Fig. 1], an unusual float is present as a reference pattern and is formed by the absence of two consecutive crossings of the weft yarn with the warp yarns. Points 31a and 31b, then 31c and 31d, then 31e and 31i constitute the reference patterns in [Fig. 1].

[0101] In actual armor, these reference patterns will be seen as a skin thread much longer than the other surrounding threads and will allow the operator to spot the particular direction 20.

[0102] Such an irregular pattern in an otherwise regular armor is indeed easily detectable by an optical device, and especially by the human eye.

[0103] In [Fig. 1], the float of the weft yarn in the particular direction 20 is carried out over a length of 11 warp planes. The regular weave ratio of the figure is 4, as illustrated by the motif element 10, which is a 4x4 square.

[0104] In [Fig. 1], the float of the weft yarn forming the marker pattern is therefore greater than two and a half times the ratio of the regular weave, which ensures that the marker pattern includes 2 differences with the elementary pattern of the regular weave, before the formation of a new regular pattern. In [Fig. 1], it can indeed be observed that along the particular direction, the marker pattern is created by the irregularity of 2 consecutive points 31a and 31b, then 31c and 31d, then 31e and 31b.

[0105] An unusual float length that is greater than or equal to two and a half times the ratio of the regular weave thus ensures that the marker pattern is different from an error punctual weaving.

[0106] Of course, when the marker pattern is an unusual float, its length must remain less than the maximum length beyond which the wire can deform, because this would make it imprecise to determine the particular direction precisely located by the unusual float.

[0107] For example, the maximum length of an unusual float may be less than or equal to 15 mm.

[0108] Figure [Fig. 2] represents a weaving armature in another embodiment of the invention.

[0109] This is a satin weave of 4, the elementary motif of which 10 is identified on [Fig.2],

[0110] In [Fig.2], the reference pattern, locating the particular direction 20, is obtained by reversing the weaving planes.

[0111] The armor to the left of the particular direction 20 is completely regular. It is obtained by the periodic repetition of planes 1 to 8.

[0112] It should be noted that the minimum periodicity is 4, and that plans 5 to 8 are equivalent to plans 1 to 4, but the periodicity of 8 illustrates the plan inversion better here.

[0113] From the numbered plane 5 comprising the particular direction 20, the weave planes are no longer repeated in ascending order 1 to 8 but in descending order 8 to 1.

[0114] The portion of the weave 201 to the right of the particular direction 20 is also a 4 satin weave, and it can be noted that the marker pattern introduced to locate the particular direction 20 has in no way altered the long-distance periodicity of the weave 201 beyond the particular direction 20.

[0115] The armor modification created by the marker pattern is extremely localized, which ensures minimal disturbance of the preform.

[0116] This ensures in particular that the matrix formation properties are identical, despite the presence of the visual reference.

[0117] The inversion of the weaving planes allows the appearance of a reference pattern in the weave 201 which extends along the particular direction 20. Indeed, the periodicity is locally broken, and is replaced by an axial symmetry, which singles out the particular direction 20 among the rest of the weave 201 and makes it easily identifiable, in particular for a human eye.

[0118] [Fig.3] represents a 301 weave in another embodiment.

[0119] This is a 2-linked twill weave, whose elemental pattern 10 is spotted on the [Fig.3],

[0120] As in the case of [Fig. 2], the local variation of the weave 301 is an inversion of the weave planes. [Fig. 3] shows the numbering of the weaving patterns to aid understanding.

[0121] Starting from the numbered plane 3 and including the particular direction, the weave planes are no longer repeated in ascending order 1 to 8 but in descending order 8 to 1.

[0122] The modification of the weave structure created by reversing planes on a 2-linked 2 twill weave forms a marker pattern which is even more visible than for other types of weave, for example the 4-weave satin of [Fig.2].

[0123] Figure 4 describes an embodiment of a weave structure 401 which would be obtained, as with weave structure 201 of Figure 2, with a reference pattern corresponding to a plane of symmetry, obtained by inverting the weave planes. In order to further reinforce the particular direction 20, the weave structure 401 further includes unusual floats 32a, 32b, 32c, and 32d, aligned with said particular direction 20.

[0124] The reference pattern enabling the particular direction 20 to be located is therefore the combination of the plane of symmetry and the unusual floats.

[0125] The embodiment illustrated in [Fig.4] clearly shows how the superposition of the two embodiments described above for obtaining a reference pattern can be combined to achieve a weave structure 401, and consequently a fibrous preform, of which a particular direction 20 can be easily identified.

[0126] This embodiment is preferred when, for the chosen weave, the mere inversion of the weave planes does not define the particular direction extremely clearly. For example, it can be noted that the plane inversion in a 4-ply satin weave ([Fig. 2]) is not as distinct as in the case of a 2-ply twill ([Fig. 3]). Adding the creation of unusual floats to the plane inversion then makes it possible to identify the particular direction even more precisely.

Claims

Demands

1. A fibrous preform for the manufacture of a part of composite material, the fibrous preform having a three-dimensional weave comprising a plurality of layers of weft yarns and a plurality of layers of warp yarns extending in a direction perpendicular to the direction of the weft yarns, in which each weft yarn binds warp yarns of several layers, the weft yarns and warp yarns being woven in a regular weave, the fibrous preform being characterized in that it comprises on the surface one or more marker patterns extending in a particular direction (20) of the fibrous preform, a marker pattern being created by a local variation of the weave (101, 201, 301, 401).

2. Preform according to claim 1, wherein the particular direction (20) is a weft or warp direction.

3. Preform according to claim 1 or 2, wherein the marker pattern is a skin yarn making a float longer than the floats of the weft or warp yarns in a pattern (10) of the regular weave.

4. Preform according to claim 3, wherein the marker pattern is a float of a hide thread over a length greater than or equal to two and a half times the length of the elementary pattern of the weave.

5. Preform according to claim 1 to 4, wherein the marker pattern is a plane of symmetry of the weave structure, and the particular direction (20) is aligned along this plane of symmetry.

6. Preform according to any one of claims 1 to 5, wherein the warp yarns and weft yarns may be composed of carbon fibers, glass fibers, alumina fibers, silicon carbide fibers, Kevlar fibers or a mixture of several of these fibers.

7. A method of weaving a fibrous preform in a regular weave comprising the three-dimensional weaving of a plurality of layers of weft yarns and a plurality of layers of warp yarns extending in a direction perpendicular to the direction of the weft yarns, wherein each weft yarn binds warp yarns of several layers, the method being characterized in that it further comprises one or more steps of local variation of the weave structure (101, 201, 301, 401) so as to create a reference pattern on the surface of the fibrous preform, the reference pattern extending in a particular direction (20) of the preform.

8. Weaving method according to claim 7, wherein the local variation of the weave weave (101, 201, 301) comprises a step of realizing an unusual float.

9. Weaving method according to claim 7 or 8, wherein the local variation of the weave weave (101, 201, 301) comprises a step of reversing the weaving planes.

10. A method for manufacturing a part made of composite material comprising at least one step of arranging a preform according to claims 1 to 6 in a tool during which one or more particular directions of the preform identified by the preform's marker patterns are aligned in one or more particular directions of the tool; and a step of forming a die in the preform thus arranged in a tool.

11. Part made of composite material comprising a preform according to claims 1 to 6.

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