Fibrous preform comprising a reference pattern

Abstract

The invention relates to a fibrous preform for the manufacture of a part made 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 which extend in a direction perpendicular to the direction of the weft yarns, wherein each weft yarn connects warp yarns of multiple layers, the weft yarns and the warp yarns being woven according to a regular weave, the fibrous preform being characterised in that it comprises, on the surface, one or more reference patterns that extend in a particular direction (20) of the fibrous preform, a reference pattern being created by a local variation in the weave (101, 201, 301).

Description

[0001] Description

[0002] Title of the invention: Fibrous preform comprising a reference pattern

[0003] Technical Field

[0004] The invention relates to the field of composite materials and more specifically to fiber preforms for the manufacture of these materials or to the methods for manufacturing such preforms or such materials.

[0005] Prior art

[0006] Composite materials are of growing technological interest and have found a wide variety of uses in recent years.

[0007] In particular, organic matrix composites (OMCs) and ceramic matrix composites (CMCs) replace metallic parts in certain parts of turbomachines. Their use contributes to optimizing aircraft performance, in particular by improving the efficiency of the turbomachine and reducing the overall mass of the turbomachine, significantly reducing harmful emissions to the environment (CO, CO2, NO X ...).

[0008] The preparation of such materials is generally done by forming a matrix within a fiber preform. The mechanical properties of the final part depend not only on the composition of the preform and matrix, but also on the weave chosen for the preform, and the orientation of the fibers within the preform.

[0009] This is why the fiber preform cannot be randomly arranged in the part manufacturing processes. In particular, it is desirable that the preform can be precisely placed in a former or in a densification tool. This makes it possible to identify certain specific areas or directions of the preform, which ensures that the mechanical properties of the final part are as expected. Usually, a particular direction of the preform is identified by a tracer thread woven in that direction and whose appearance is different from the threads of the rest of the preform. This allows visual identification of a particular direction of the preform, which facilitates the correct positioning of the preform in the tool.

[0010] To make the appearance of the tracer wires different from the rest of the preform, the tracer wires are of a different nature from the other wires in the preform. For example, for a silicon carbide fiber preform, the tracer wires are generally chosen to be alumina wires.

[0011] Although this solution is generally satisfactory, it has been observed that the tracer wires, due to their different nature, do not exhibit the same behavior as the rest of the preform during the formation of the matrix.

[0012] 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 surface of the preform. This poor formation of the matrix near the tracer wire results in an absence of matrix or a matrix present in low thickness 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 not having the desired properties.

[0013] On the one hand, there is a need for a preform whose orientation can be known 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.

[0014] Statement of the invention

[0015] The invention aims precisely to meet this need.

[0016] For this purpose, according to a first of its aspects, the invention proposes 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 threads and a plurality of layers of warp threads extending in a direction perpendicular to the direction of the weft threads, in which each weft thread binds warp threads of several layers, the weft threads and the warp threads being woven according to a regular weave pattern, the fiber preform being characterized in that it comprises on the surface one or more reference patterns extending in a particular direction of the fiber preform, a reference pattern being created by a local variation of the weave pattern.

[0017] The weave pattern of the fiber preform is very regular to meet aerodynamic needs. A point variation in the weave pattern creates a reference pattern that breaks with the regularity of the rest of the weave.

[0018] The reference pattern makes the direction in which it extends identifiable, without the need to modify the nature of the weft or warp threads.

[0019] Thus, in such a preform, a particular direction can be identified, without requiring threads of a nature other than the weft or warp threads.

[0020] Furthermore, the local variation of the weave pattern of the preform to create the reference pattern(s) does not harm the properties of the final part. In particular, the densification of the preform by the matrix is ​​not modified by the local variation of weave pattern, unlike what can be observed with a tracer thread of a different nature.

[0021] In one embodiment, the local variation of the weave is performed only on the top layer of the weave weave, i.e., only the top layer of the weave weave comprises a weave different from the rest of the weave.

[0022] The top layer of the preform is also called the skin layer or preform skin.

[0023] In one embodiment, the fiber preform comprises a 3D weave, for example an interlock weave below the skin layer in contact with the free surface.

[0024] 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, such as an "interlock weave". By "interlock weave" is meant here a 3D weave weave in which each warp layer binds several weft layers with all the threads of the same warp layer having the same movement in the plane of the weave.

[0025] A preform according to the invention therefore makes it possible to overcome the disadvantages linked to the use of tracer wires described above.

[0026] In one embodiment of the invention, all the weft threads present in the skin of the preform have the same composition.

[0027] In one embodiment of the invention, all the warp threads present in the skin of the preform have the same composition.

[0028] In one embodiment of the invention, all the weft and warp threads present in the skin of the preform have the same composition.

[0029] In one embodiment, the particular direction identified in a preform of the invention is a weft or warp direction.

[0030] It should be noted that the terms "weft" and "warp" are conventions, which should not be interpreted in a restrictive manner. In particular, it should be noted that, throughout the text, warp and weft may be interchanged.

[0031] In one embodiment, the reference pattern is a skin yarn having a longer float than the floats of the weft or warp yarns in a regular weave pattern.

[0032] A skin yarn is a weft or warp yarn that is present on the surface of the preform.

[0033] This embodiment is advantageous because it allows the creation of a reference pattern, by only modifying the weaving of one skin thread, the rest of the weave remaining identical to a regular weave. This embodiment makes it very easy to identify a weft or warp direction, without complicating the weaving.

[0034] In such an embodiment, the reference pattern may be a float of a skin thread over a length greater than or equal to the length of two and a half times the length of the elementary pattern of the weave. The “elementary pattern of the weave”, also called “weave repeat” is understood, in the usual sense of the field, as the unit of repetition strictly necessary to reproduce the regular weaving weave by periodicity.

[0035] For example, for a twill or satin weave the weave ratio is usually specified, and we speak of 2-linked 2-linked twill, 4-linked satin in which the weave ratio is 4, or 8-linked satin in which the weave ratio is 8.

[0036] Such a length for the float of a skin yarn defining a reference pattern allows the float of the reference pattern to be long enough to be visible to the operator, and is also distinguished from a simple unintentional weaving fault.

[0037] It should be noted that the regular weave may include floats of skin yarns, but over a shorter distance than the float of the reference pattern. The skin yarn creating a longer float therefore disrupts the periodic repetition of the regular weave to form a reference pattern.

[0038] Such a landmark pattern is easily identifiable by an optical device, particularly by a human eye.

[0039] In one embodiment, the local variation in the weave pattern may correspond to an inversion of the weave planes.

[0040] In this embodiment, the reference pattern is a plane of symmetry of the weave pattern, and the particular direction is aligned along this plane of symmetry.

[0041] The regular weave includes a repeating pattern and is produced by successively weaving planes 1, 2 ... n, n+1, n+2 ... and until reaching the periodicity of the regular weave where we then start again with plane 1.

[0042] The inversion of the weaving planes is obtained by weaving, from the plane n of the inversion, the same planes as before, but in decreasing order.

[0043] That is to say, we weave, from the plane n of the inversion, the planes n-1, n-2 ... and so on up to 1 then we continue by reproducing the periodicity of the regular weave in decreasing order. Such an inversion of the weaving planes creates on the surface of the preform a plane of symmetry of the weave, sometimes called a herringbone, which extends in a particular direction of the preform.

[0044] In one embodiment, the preform comprises, 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.

[0045] In this embodiment, the weave pattern of the skin of the preform may be different from the rest of the preform, for example a 2-bonded twill type skin, and the rest of the preform is an interlock weave.

[0046] This embodiment allows to specifically choose a skin armor in which the local variation will be even more clearly visible, thus improving the identification of the particular direction.

[0047] In one embodiment, the regular weave is chosen from a satin weave, for example 4 satin, 8 satin, a twill weave, for example 2-linked 2 twill or 4-linked 4 twill or a plain weave, and the remainder of the preform being an interlock type weave.

[0048] In one embodiment, the landmark pattern may be the superposition of a plane of symmetry and unusual floats.

[0049] This can be achieved by superimposing an inversion of the weaving planes together with the creation of unusual floats.

[0050] This embodiment makes it possible to obtain an even more unique reference pattern on the surface of the preform.

[0051] In one embodiment, the marker pattern extends across the entire width of the preform in the particular direction.

[0052] In one embodiment, the marker pattern extends across the entire width of the preform in the weft or warp direction. According to another of its aspects, the invention relates to a method of weaving a fiber preform in a regular weave pattern comprising 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 locally varying the weave pattern so as to create a marker pattern on the surface of the fiber preform, the marker pattern extending in a particular direction of the preform.

[0053] As mentioned, the reference pattern allows you to identify a particular direction. A single weaving error cannot therefore be considered a reference pattern, because it does not extend in a particular direction.

[0054] In one embodiment, the local variation of the weave pattern includes a step of making an unusual float of a skin yarn.

[0055] An unusual float is characterized by a surface yarn that does not respect the regular structure of the weave and passes over a greater number of surface weft yarns than according to the regular weave.

[0056] In one embodiment, the unusual float is a float of a length greater than or equal to the length of two and a half times the weave ratio of the regular weave.

[0057] This embodiment makes it possible to ensure a reference pattern that is easily differentiated from an unintentional one-off weaving error.

[0058] In one embodiment, the local variation of the weave pattern may comprise a step of inverting the weave planes.

[0059] This embodiment makes it possible to artificially obtain a plane of symmetry in the weaving weave as a reference pattern.

[0060] In one embodiment, the weave variation may be achieved by combining an inversion of the weave planes and the production of unusual floats, the unusual floats being produced in the plane corresponding to the inversion of the weave planes.

[0061] This provides a more easily identifiable reference pattern than either of the weave variations alone, and ensures that together the plane of symmetry and the unusual floats identify the same particular direction of the preform.

[0062] According to another of its aspects, 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 tool during which one or more particular directions of the preform identified by the reference patterns of the preform are aligned in one or more particular directions of the tool; and a step of forming a matrix in the preform thus arranged in the tool to form the matrix of the part made of composite material.

[0063] The inventors have found that such a method makes it possible to use the same tools as those already existing and in which it is planned to arrange 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 identify a particular direction of the preform.

[0064] In fact, the reference pattern, which is obtained without variation in the nature of the skin threads of the preform, does not disturb the formation of the matrix in the preform.

[0065] In one embodiment, the preform may comprise weft yarns that are the same as or different from the warp yarns.

[0066] In one embodiment, the preform may comprise 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.

[0067] It should be understood that the method of the invention is compatible with any three-dimensional fibrous armor.

[0068] In one embodiment, the part may be a ceramic matrix or organic matrix composite material part.

[0069] In one embodiment, the matrix may be a resin, for example, a resin comprising unsaturated polyesters or epoxies. In one embodiment, the matrix may be alumina, mullite, silicon carbide, carbon.

[0070] In one embodiment, the matrix forming step can be chosen from numerous impregnation processes, including liquid composite molding, also known as “LCM”, resin transfer molding, also known as “RTM”, high-pressure resin transfer molding, also known as “HP-RTM”, and compression resin transfer molding, also known as “C-RTM”.

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

[0072] In another embodiment, the matrix formation step may be a molten metal infiltration (or MI) step.

[0073] In one embodiment, the method may further comprise a step of consolidating the preform, for example carried out by chemical vapor infiltration (or CVI for the acronym in English “chemical vapor infiltration”) carried out before the step of forming the matrix, and the tooling may be a conformer.

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

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

[0076] - a step of consolidation of the preform carried out by chemical vapor infiltration; and - a step of infiltration of the consolidated preform by molten silicon, to form the matrix in the consolidated preform.

[0077] According to another of its aspects, the invention relates to a part made of composite material comprising a preform as described above.

[0078] For example, such a composite material part may be an aeronautical part, for example a turbomachine blade, a turbomachine ring or a turbomachine distributor.

[0079] The composite material part includes a textile marker on its surface which is still visible.

[0080] Brief description of the drawings

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

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

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

[0084] [Fig. 4] Figure 4 schematically represents a weaving armor according to a fourth embodiment of the invention.

[0085] Description of the embodiments

[0086] The invention is now described by means of figures, present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0087] The invention relates to a three-dimensional fiber preform whose weaving pattern makes it possible to directly identify a particular direction, avoiding the use of tracer threads and the associated drawbacks described above.

[0088] 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 weaving armor of a fiber preform 101 according to a first embodiment.

[0089] Conventionally, a weave pattern is represented by a gray and white chart in which the weft direction is represented horizontally, and the warp direction vertically.

[0090] Each square in a weave pattern represents a crossing between a weft and a warp thread. A white dot indicates that the weft thread passes over the warp thread, while a gray dot indicates that the warp thread passes over the weft thread.

[0091] The armor represented schematically by gray and white squares is visible on the surface of the preform, regardless of the nature of the threads.

[0092] Of course, the sharpness of the weave pattern on an actual preform is not the same as that shown schematically on the weave pattern, but the relief created by the interweaving of the weft and warp threads in an actual preform is easily comparable to the schematic weave pattern.

[0093] 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 threads.

[0094] For example, the weft and / or warp yarns may be composed of carbon fibers, glass fibers, alumina fibers, silicon carbide fibers, Kevlar fibers or a mixture of several of these fibers.

[0095] In Figure 1, the regular weave shown is a satin of 4 whose elementary pattern 10 is identified in Figure 1.

[0096] The precise weave pattern has no bearing on the successful achievement of the technical effect. It only matters that the reference pattern is different from the rest of the weave to allow the operator to easily identify a particular direction.

[0097] The weave 101 of Figure 1 represents 40 warp planes identified by numbers from 1 to 40, and 14 weft planes. In Figure 1, the particular direction 20, here aligned with the fourth weft plane, 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 fiber preform produces unusual floats, which create reference patterns aligned with the weft direction.

[0099] It will be noted that the elementary pattern 10 comprises regular floats, in figure 1, floats of 3, characterized by a succession of 3 gray squares representing a weft thread passing over 3 warp threads in a row before being taken up under a warp thread (white square).

[0100] In Figure 1, an unusual float is present as a reference pattern and is formed by the absence of two consecutive crossings of the weft thread with the warp threads. Points 31a and 31b then 31c and 31d then 31e and 3 If constitute the reference patterns in Figure 1.

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

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

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

[0104] In Figure 1, the float of the weft yarn making the reference pattern is therefore greater than two and a half times the ratio of the regular weave, which ensures that the reference pattern includes 2 differences with the elementary pattern of the regular weave, before the creation of a new regular pattern. In Figure 1, we can indeed notice that along the particular direction, the reference pattern is created by the irregularity of 2 consecutive points 31a and 31b, then 31c and 31d, then 31e and 31f. A length of the unusual float which is greater than or equal to two and a half times the ratio of the regular weave thus ensures that the reference pattern is different from a point weaving error.

[0105] Of course, when the reference pattern is an unusual float, its length must remain less than the maximum length beyond which the yarn can deform, because this would make it imprecise to determine the particular direction precisely identified by the unusual float.

[0106] For example, the maximum length of an unusual float may be less than or equal to 15 mm.

[0107] Figure 2 shows a weave pattern in another embodiment of the invention.

[0108] This is a 4 satin weave, with the basic pattern 10 marked in Figure 2.

[0109] In Figure 2, the reference pattern, identifying the particular direction 20, is obtained by reversing the weaving planes.

[0110] The armor to the left of particular direction 20 is completely regular. It is obtained by the periodic repetition of planes 1 to 8.

[0111] Note that the minimum periodicity is 4, and that planes 5 to 8 are equivalent to planes 1 to 4, but the periodicity of 8 here better illustrates the plane inversion.

[0112] From the plane numbered 5 including the particular direction 20, the planes of the weaving weave are no longer repeated in ascending order 1 to 8 but in descending order 8 to 1.

[0113] The portion of the weave pattern 201 to the right of the particular direction 20 is also a satin weave of 4, and it can be noted that the reference pattern introduced to identify the particular direction 20 has in no way modified the long-distance periodicity of the weave 201 beyond the particular direction 20.

[0114] The armor modification created by the marker pattern is extremely localized, ensuring minimal disruption to the preform. This ensures, in particular, that the forming properties of the matrix are identical, despite the presence of the visual marker.

[0115] The inversion of the weaving planes allows the appearance of a reference pattern in the weaving weave 201 which extends along the particular direction 20. Indeed, the periodicity is locally broken, and is replaced by an axial symmetry, which distinguishes the particular direction 20 from the rest of the weave 201 and makes it easily identifiable, in particular for a human eye.

[0116] Figure 3 shows a weave pattern 301 in another embodiment.

[0117] This is a 2-bonded 2-twill weave, whose basic pattern 10 is shown in Figure 3.

[0118] As in the case of Figure 2, the local variation of the weave pattern 301 is an inversion of the weave pattern planes. Figure 3 shows the numbering of the weave patterns to aid understanding.

[0119] Starting with the plane numbered 3 and including the particular direction, the planes of the weaving weave are no longer repeated in ascending order 1 to 8 but in descending order 8 to 1.

[0120] The modification of the weave pattern created by reversing planes on a 2-bonded 2-twill weave forms a landmark pattern that is even more visible than for other weave types, for example the 4-satin of Figure 2.

[0121] Figure 4 depicts an embodiment of a weave pattern 401 which would be obtained as for the weave 201 of Figure 2 with a reference pattern corresponding to a plane of symmetry, obtained by inverting the weaving planes. In order to further reinforce the particular direction 20, the weave pattern 401 further comprises unusual floats 32a, 32b, 32c and 32d, aligned with said particular direction 20.

[0122] The reference pattern making it possible to identify the particular direction 20 is therefore the combination of the plane of symmetry and the unusual floats. The embodiment illustrated in Figure 4 clearly shows how the superposition of the two embodiments described above for obtaining a reference pattern can be combined to achieve a weaving pattern 401, and consequently a fiber preform, for which a particular direction 20 can be easily identified.

[0123] This embodiment is preferred when, for the chosen weave, the inversion of the weaving planes alone does not define the particular direction extremely clearly. For example, it can be noted that the inversion of the plane in a satin weave of 4 (figure 2) is not as clear as in the case of a twill 2 bonded 2 (figure 3). Adding to the inversion of planes the creation of unusual floats then makes it possible to identify the particular direction even more precisely.

Claims

Claims

1. 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 threads and a plurality of layers of warp threads extending in a direction perpendicular to the direction of the weft threads, in which each weft thread binds warp threads of several layers, the weft threads and the warp threads being woven according to a regular weave pattern, the fiber preform being characterized in that it comprises on the 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 pattern (101, 201, 301, 401).

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

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

4. Preform according to claim 3, in which the reference pattern is a float of a skin thread over a length greater than or equal to two and a half times the length of the elementary pattern of the weave.

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

6. Preform according to one of claims 1 to 5, in which the warp threads and the weft threads 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 fiber preform in a regular weave pattern comprising 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 pattern (101, 201, 301, 401) so as to create a reference pattern on the surface of the fiber preform, the reference pattern extending in a particular direction (20) of the preform.

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

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

10. A method of 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 reference patterns of the preform are aligned in one or more particular directions of the tool; and a step of forming a matrix in the preform thus arranged in a tool.

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

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