WO2024042294A1

WO2024042294A1 - Loom and method for manufacturing a shaped fabric

Info

Publication number: WO2024042294A1
Application number: PCT/FR2023/051285
Authority: WO
Inventors: Maxime GUILLOT; Romain CHAUFOUR; Hubert Jean Marie Fabre
Original assignee: Safran Aircraft Engines
Priority date: 2022-08-22
Filing date: 2023-08-22
Publication date: 2024-02-29
Also published as: FR3138920A1

Abstract

The invention relates to a Jacquard loom (10) for manufacturing a fabric (T) having a variable thickness (e₁, e₂, e₃) across its width (L) by means of weaving between a plurality of warp yarns (30) and a plurality of weft yarns (31), the loom comprising: a plurality of heald wires (22), which are connected to a mechanism (11) capable of moving the heald wires in a vertical direction (Dv) between a reference position (PH) and a first position for opening the warp yarns, each heald wire being further provided with an eye (23) through which a warp yarn (30) passes, a rapier (40) arranged downstream of the heald wires (113), capable of drawing a weft yarn (31) from a bobbin (50), a device (90) for holding the fabric arranged downstream of the plurality of heald wires (22) and of the rapier (40), comprising two bearing surfaces (93, 94) arranged on either side of the fabric (T) to compress the fabric between the bearing surfaces (93, 94), characterised in that at least a first bearing surface (93) is shaped so as to be at least partially complementary to a surface of the fabric.

Description

WEAVING LOM AND METHOD FOR MANUFACTURING A SHAPED FABRIC

Technical area

The invention relates to the manufacture of a fabric, in particular a three-dimensional fabric, in shape, that is to say having a variable thickness over its width. Such a fabric can in particular serve as reinforcement or preform in the manufacture of composite objects by resin transfer molding, particularly for applications in aeronautics.

State of the art

Three-dimensional (3D) fabrics can be used as reinforcements or preforms in composite objects manufactured by resin transfer molding (RTM, acronym for the Anglo-Saxon term “Resin Transfer Molding”).

Depending on the geometry of the object, the reinforcement does not always have a constant thickness over its entire width. In particular, the surface of the mold on which the reinforcement is placed before the injection of the resin may not be developable. In this case, to avoid the formation of folds when placing the reinforcement in the mold cavity, it may be advantageous for the fabric to have a variable thickness, for example, a lower thickness on its edges than in its center.

Such a fabric can be manufactured using a Jacquard type loom, which is described in particular in document FR 3 074 195 A1.

Figure 1 illustrates a Jacquard type loom 10 used for the production of a three-dimensional fabric obtained by multilayer weaving between a plurality of layers of warp threads 30 and a plurality of layers of weft threads 31.

The weaving loom 10 is equipped with a Jacquard mechanism 11 supported by a superstructure not shown in Figure 1.

The loom 10 also includes a harness 20 consisting of a cutting board 21 and control wires or heddles 22, each heddle 22 being connected at one end to a control hook 12 of the Jacquard mechanism 11 and at the other end to one of the return springs 13 fixed to the frame 14 of the loom 10.

Each heddle 22 comprises an eyelet 23 crossed by a warp wire 30. The heddles 22 and their associated eyelet 23 are animated by a substantially vertical oscillation movement represented by the double arrow F under the tensile forces exerted respectively by the hooks control 12 and return springs 13.

The heddles 22 make it possible to lift certain warp threads 30 and thus create a shed 15, that is to say an opening between lower and upper layers of warp threads 30 allowing the introduction of weft threads 31 by means of 'a lance 40.

The lance 40 is provided at its end with a clamp 41 which grasps a weft thread 31 from a spool 50 to place it through the opening between the layers of threads of warp 30 created by the shed 15, the weft thread 31 being cut using a knife 60 after its positioning in the shed 15.

A comb 70 present upstream of the lance 40 is then folded down in order to pack the weft thread(s) introduced into the shed 15.

The lance 40 is then ready to again grab a new weft thread 31 from the spool 50 and place it either again in the shed 15, or in a different shed depending on the defined weaving.

We thus gradually form a fabric T having a 3D or multilayer weave between the warp threads 30 and the weft threads 31.

The weaving loom 10 further comprises a fabric holding device T present downstream of the heddles 22 and the lance 40.

The holding device 80 comprises a lower jaw 81 and an upper jaw 82 each connected to an actuation means (not shown). Said holding device makes it possible in particular to control the position of the opening point of the shed 15, that is to say the location from which two layers of warp threads move away from each other towards upstream.

A difficulty encountered when weaving a three-dimensional fabric is the expansion of the fabric, that is to say the phenomenon of swelling of the fabric due to the interweaving of the warp and weft threads.

Because of this expansion, the three-dimensional fabric leaving the loom has a thickness greater than the planned thickness, which can cause defects during the implementation of the RTM process.

In particular, the reinforcement can form localized bumps, which can give rise to pinching of the fabric when closing the mold, resulting, in the final object, in areas whose mechanical properties are not controlled.

Document WO 2021/048486 thus describes a method of closing a mold intended to avoid such pinching.

Brief description of the invention

An aim of the invention is therefore to design a loom making it possible to control the expansion of the shaped fabric and thus improve the RTM process which may be implemented subsequently.

For this purpose, the invention proposes a Jacquard type loom for the manufacture of a fabric, in particular a two-dimensional or three-dimensional fabric, having a variable thickness over its width by weaving between a plurality of warp threads and a plurality of weft threads, said loom comprising: - a plurality of control wires, connected to a mechanism capable of moving the control wires in a vertical direction between a reference position and a first opening position of the chain wires, each control wire being further provided with an eyelet crossed by one of the warp threads,

- a lance arranged downstream of the control wires, capable of pulling a weft wire from a spool,

- a fabric holding device arranged downstream of the plurality of control wires and the lance, comprising at least two support surfaces, including at least a first support surface and a second support surface arranged on either side and on the other side of the fabric to compress the fabric between said support surfaces.

Said loom is characterized in that at least the first support surface is shaped in a manner that is at least partially complementary to a surface of the fabric.

Due to the variation in thickness of the fabric, at least one surface of the fabric is non-flat.

By “conformed in an at least partially complementary manner”, we mean in the present text that the first support surface has a non-planar shape whose concavity is oriented towards the surface of the fabric. Preferably, the support surface matches at least partly the non-flat surface of the fabric, that is to say, when the first support surface is brought towards the surface of the fabric following the vertical direction , the distance between the first support surface and the surface of the fabric is substantially constant at least in part of the width of the fabric.

In this text, the terms “upstream” and “downstream” are understood in the sense of the progress of the weaving of the threads.

Advantageously, the holding device comprises at least one holding bar having said at least one first support surface.

In certain embodiments, said support bar comprises a body and a removable portion carrying the first support surface, the removable portion being reversibly linked to the body of the support bar.

Said removable portion may be in the form of a solid metal bar, in which the first bearing surface is formed.

In certain embodiments, the holding device comprises a table presenting the second support surface, said second support surface being flat.

Particularly advantageously, the distance between the first and second support surfaces is chosen so as to reduce the expansion of the fabric to reach a minimum expansion threshold.

Another object of the invention relates to a method of manufacturing a fabric, in particular a 3D fabric, having a variable thickness over its width, comprising: - weaving a plurality of warp threads and a plurality of weft threads using a Jacquard type loom as described above, so as to form said fabric, and

- the application, by the holding device, of a compression of the tissue via said first and second support surfaces.

Particularly advantageously, the distance between the support surfaces is controlled so as to reduce the expansion of the fabric to reach a minimum expansion threshold.

In some embodiments, the warp threads and the weft threads include carbon and/or glass.

Another object of the invention relates to a method of manufacturing a composite object comprising a fabric, in particular a two-dimensional or three-dimensional fabric, having a determined shape, said method comprising:

- the manufacture of said fabric by the process as described above;

- the winding of a reinforcement formed from a portion of said fabric in an imprint of a mold defining an exterior surface of the object;

- closing the mold;

- the introduction of a resin into the impression to impregnate the reinforcement.

In certain embodiments, the object presents a form of revolution.

The object may in particular be a fan casing, a turbine casing, a nozzle casing or a mixer casing for an aeronautical engine.

Brief description of the figures

Other characteristics and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings, in which:

- Figure 1 shows an overview of a known Jacquard type loom;

- Figures 2A, 2B and 2C are sectional views of a three-dimensional fabric having a variable thickness over its width;

- Figure 3 is a sectional view of the three-dimensional fabric of Figure 2A and of a bar of the holding device according to one embodiment;

- Figure 4 is a sectional view of the three-dimensional fabric of Figure 2A and of a bar of the holding device according to the state of the art;

- Figure 5 shows an overview of a Jacquard type loom according to one embodiment of the invention;

- Figure 6 is a principle graph of the evolution of the expansion as a function of the distance between the bearing surfaces of the holding device. For reasons of readability of the figures, the drawings have not necessarily been represented to scale.

Reference signs that are identical from one figure to another designate elements that are identical or perform the same function.

Detailed description of embodiments

The invention relates to the manufacture of a shaped fabric having controlled expansion. In the remainder of the text, reference will mainly be made to a three-dimensional fabric, but the description also applies to a two-dimensional fabric.

Figure 2A illustrates an example of a shaped three-dimensional fabric, seen in section. In this example, the fabric has a flat lower surface and a thickness increasing successively from its edge (thickness ei) towards its center (thickness es) with an intermediate thickness e2, thus forming a non-flat upper surface. Naturally, this thickness variation profile is given for illustrative purposes only and is not limiting.

Furthermore, the two main surfaces of the fabric may have a non-planar shape.

Figure 2B illustrates a second example of a shaped three-dimensional fabric, seen in section.

Figure 2C illustrates a third example of a shaped three-dimensional fabric, seen in section.

Generally speaking, shaped weaving consists of weaving a profile proportional to the interior profile of the composite object to be produced. In a manner known in itself, this profile is obtained by a differential draw of wires by means of a non-cylindrical take-up roller which allows different lengths of wires depending on the location of each wire on the roller.

The expansion of such a fabric can be defined as being the ratio between the total volume occupied by the fabric, as produced by the loom, and a reference volume for this fabric, corresponding for example to the smallest volume at which we could bring this tissue by compressing it.

In the invention, the expansion is controlled by the use of a holding device which has a support surface shaped at least partially complementary to the shape of the surface of the fabric opposite.

Figure 3 illustrates a sectional view of the fabric of Figure 2A and of a bar 92 of the holding device according to one embodiment of the invention.

The support surface 93, which comes into contact with the fabric T, makes it possible to compress the assembly of the warp and weft threads and thus reduce the expansion of the fabric. On the contrary, in a holding device of known type, as illustrated in Figure 4, the surface of the jaw 82 facing the tissue is flat and cannot therefore come into contact with the entire surface of the tissue nor compress evenly the fabric.

Figure 5 illustrates a Jacquard type loom 10 comprising a holding device according to the invention.

In a manner known in itself, the weaving loom 10 is equipped with a Jacquard mechanism 11 supported by a superstructure not shown in Figure 5.

The lance 40 is provided at its end with a clamp 41 which grasps a weft thread 31 from a spool 50 to place it through the opening between the layers of warp threads 30 created by the shed 15, the weft thread 31 being cut using a knife 60 after its positioning in the shed 15.

The weaving loom 10 further comprises a device 90 for holding the fabric T present downstream of the heddles 22 and the lance 40.

In accordance with the invention, said holding device 90 comprises two supporting surfaces 93, 94 arranged on either side of the fabric.

The support surface 93 facing the upper surface of the fabric, which is a shaped surface of the fabric, has a shape complementary to the surface of the fabric.

In the embodiment illustrated in Figure 3, the shape of the support surface is complementary to the surface of the fabric to the extent that, at any point of the width of the fabric, the distance between the support surface and the surface of the fabric is constant (this distance being zero when the support surface is in contact with the fabric). However, in other embodiments, the support surface could have a shape partially complementary to that of the surface of the fabric, that is to say the distance between the support surface and the fabric could be constant in one part of the width of the fabric (for example a central part), but different in another part of the width of the fabric (for example a peripheral part). In other embodiments, the shape of the support surface could not coincide perfectly with the shape of the surface of the fabric, but present an intermediate shape between a planar shape and the shape of the surface of the fabric, this shape intermediate having a concavity oriented towards the surface of the fabric (in other words, if the surface of the fabric has a hollow, the corresponding part of the support surface has a bump and vice versa, if the surface of the fabric has a bump, the corresponding part of the support surface has a hollow). Generally speaking, the relative distance difference between the support surface and the surface of the fabric depending on the width of the fabric is on average less than 30%, or even less than 10%.

Said support surface 93 belongs to a holding bar 92. The holding bar 92 can be integral with the frame 14 of the loom 10.

Optionally, the loom may have several support surfaces each arranged on a respective holding bar, said holding bars being arranged parallel to each other.

Furthermore, the support surface 93 is not necessarily continuous. For example, said support surface can extend over at least two parallel support bars.

In the embodiment illustrated in Figure 5, the support surface 94 facing the lower surface of the fabric, which is flat, belongs to a table 91 secured to the frame 14.

Alternatively (not illustrated), if the opposite surface of the fabric also has a non-planar shape, the table 91 can be replaced by one or more holding bar(s) also having a supporting surface complementary to the lower surface of the fabric, and arranged opposite the support surface 93 of the holding bar 92 in a direction Z perpendicular to the main surface of the fabric.

The support surface 93 is therefore specifically shaped to at least partially match the shape of the non-flat surface of the fabric.

To manufacture a 3D fabric with a different shape, simply replace the holding bar(s) with one or two holding bar(s) having a supporting surface complementary to that of the surface of the new fabric. It is therefore a particularly simple modification of the loom. To simplify such modification, the holding bars can be in the form of an assembly of a body secured to the frame of the loom and a removable portion carrying the support surface. The removable portion can for example be linked to the body by screws or any reversible connection means.

Furthermore, the distance d between the support surfaces 93 and 94 is chosen so as to apply the support surface against the surface of the fabric and to exert a force of compression of the fabric between the holding bar 92 and the table 91 , or, where applicable, between the two retaining bars.

The support bar and the table are made in the form of structures sufficiently rigid to resist the compressive force exerted on the fabric. For example, each retaining bar (or, in the case of a removable assembly, the removable portion of the retaining bar) can be in the form of a solid metal bar, in which the bearing surface is machined .

Due to the complementarity of the surfaces in contact, this compression is substantially homogeneous over the entire contact surface, and preferably over the entire width L of the fabric. Compression has the effect of compacting the warp and weft threads in the direction of the thickness of the fabric (Z direction) and thus reducing the expansion of the fabric.

The distance d between the support surfaces is generally fixed during weaving, the holding bar 92 and the table 91 being fixed relative to the frame. However, this distance can possibly be adjusted, particularly when fine-tuning the weave, for example using shims of different thicknesses.

Those skilled in the art are able to define the force to be applied depending on the structure of the fabric to obtain minimal expansion. For example, we can measure the expansion of the fabric without applying compression through the holding device, then gradually apply an increasing compression force by decreasing the distance between the support surfaces until the required expansion is obtained.

In particular, it is possible to measure the expansion of the fabric for different distances between the support surfaces.

Figure 6 thus schematically illustrates the expansion F for a fabric of the type of that of Figure 2A, obtained empirically as a function of the distance d between the bearing surface of the holding bar and the bearing surface of the table. We observe that the more we reduce the distance d, the more the expansion is reduced until reaching a limit (which may be non-zero) corresponding to the minimum expansion Fmin that can be obtained for this tissue. Those skilled in the art are therefore able, using simple tests, to determine the distance between the support surfaces to obtain a determined expansion (preferably minimal) for a given fabric.

The holding bar 92 is then fixed at the desired distance from the table 91.

We thus gradually form a fabric T having a 3D or multilayer weave between the warp threads 30 and the weft threads 31 and having minimal expansion, that is to say that the thickness of the fabric leaving the loom 10 is substantially equal to the planned thickness, while respecting the shape defined by the variations in thickness.

In particular, in the case where the fabric is intended to form a preform or reinforcement for the manufacture of a composite object by the RTM process, the thickness of the fabric leaving the loom 10 is substantially equal to the thickness for which the mold was designed.

To manufacture such a composite object, we have a certain length of the 3D fabric manufactured using the loom 10, which constitutes a preform or reinforcement.

Said reinforcement is placed in the mold cavity of the RTM process.

For example, in the case of a fan casing, the reinforcement is wound onto a mandrel.

Even if the mandrel has a non-developable shape, the shape of the reinforcement, due to variations in fabric thickness, is adapted to minimize the formation of folds or bumps.

Furthermore, to the extent that the thickness of the reinforcement is identical to the thickness planned for the design of the mold, closing the mold does not cause pinching of the fabric.

Once the mold is closed, a resin is injected into the mold cavity. The resin impregnates the mesh of the fabric.

The molded composite object is kept in the impression for a sufficient time to allow the resin to harden.

Then, the composite object is unmolded and any finishing treatments are carried out, which are conventional and will therefore not be described in this text.

Reference may in particular be made to document EP 1 961 923 which describes a process for manufacturing a gas turbine casing made of composite material.

The quality of the composite object is significantly improved compared to that of an object made from a fabric whose expansion has not been controlled during weaving. In particular, the absence of folds or bumps during placement in the impression makes it possible to preserve the structure of the tissue at any point of the object, and thus avoid changes in localized mechanical properties. The invention finds application for the manufacture of any type of casing or casing element having a shape of revolution, in particular for an aeronautical engine, such as a fan casing, a turbine casing, a nozzle casing or a mixer housing.

Claims

1. Jacquard type loom (10) for manufacturing a fabric (T) having a variable thickness (ei, e2, es) over its width (L) by weaving between a plurality of warp threads (30) and a plurality of weft threads (31), said loom comprising:

- a plurality of control wires (22), connected to a mechanism (11) capable of moving the control wires in a vertical direction (Dv) between a reference position (PH) and a first opening position of the control wires chain, each control wire being further provided with an eyelet (23) crossed by one of the chain wires (30),

- a lance (40) arranged downstream of the control wires (113), capable of pulling a weft thread (31) from a spool (50),

- a fabric holding device (90) arranged downstream of the plurality of control wires (22) and the lance (40), comprising at least two bearing surfaces, including at least one first bearing surface ( 93) and a second support surface (94) arranged on either side of the fabric (T) to compress the fabric between said first and second support surfaces (93, 94), characterized in that at least the first support surface (93) is shaped at least partially complementary to a surface of the fabric.

2. Weaving loom according to claim 1, in which the holding device comprises at least one holding bar (92) having said at least one first bearing surface (93).

3. Weaving loom according to claim 2, wherein said holding bar comprises a body and a removable portion carrying the first support surface, the removable portion being reversibly linked to the body of the holding bar.

4. Weaving loom according to claim 3, in which said removable portion is in the form of a solid metal bar, in which the first support surface is formed.

5. Weaving loom according to one of claims 1 to 4, wherein the holding device comprises a table (91) having the second support surface (94), said second support surface (94) being flat.

6. Weaving loom according to one of claims 1 to 5, in which the distance (d) between the first and second bearing surfaces is chosen so as to reduce the expansion (F) of the fabric (T) to achieve a minimum expansion threshold (Fmin).

7. Weaving loom according to one of claims 1 to 6, configured to manufacture a three-dimensional fabric.

8. Process for manufacturing a fabric, in particular a three-dimensional fabric (T), having a thickness (ei, e2, es) variable over its width (L), comprising:

- weaving a plurality of warp threads (30) and a plurality of weft threads (31) by means of a Jacquard type loom according to one of claims 1 to 7, so as to form said fabric, and

- the application, by the holding device, of a compression of the tissue via said first and second support surfaces (93, 94).

9. Method according to claim 8, in which the distance (d) between the first and second bearing surfaces is controlled so as to minimize the expansion of the fabric.

10. Method according to one of claims 8 or 9, in which the warp threads and the weft threads comprise carbon and/or glass.

11. Process for manufacturing a composite object comprising a fabric, in particular a three-dimensional fabric, having a specific shape, comprising:

- the manufacture of said fabric by the process according to one of claims 8 to 10;

- closing the mold;

12. Method according to claim 11, in which the object has a form of revolution.

13. Method according to one of claims 11 or 12, in which the object is a fan casing, a turbine casing, a nozzle casing or a mixer casing for an aeronautical engine.