FR3115047A1 - Needle-punched fibrous structure for the production of annular fibrous brake disc preform - Google Patents

Abstract

Needle-punched fibrous structure for the production of annular fibrous preform for brake discs Needle-punched fibrous structure (100) for producing an annular fibrous brake disc preform comprising: a core (130) formed of at least two layers (131, 132, 133, 134) of fibers needled together, each layer comprising continuous fibers; andat least one layer of nonwoven staple fibers (111, 112) on a bottom (120) or top (110) side of the core. Figure for abstract: Fig. 1

Description

Needle-punched fibrous structure for the production of annular fibrous preform for brake discs

The present invention relates to the general field of the manufacture of brake discs, and more particularly the manufacture of the annular fiber preforms of these discs.

The most common aircraft braking architecture consists of friction disc brakes positioned inside the wheels. It is an alternation of rotors and stators generally called "Heat sink", in which the rotors are integral in rotation with the wheel and the stators are integral with a fixed torsion tube and the rod on which the wheel is mounted.

Considering their low density, their thermal properties and their high energy friction performance, C-C composite materials are the most widely used. These composite materials comprise a fibrous reinforcement and a matrix. Their manufacture involves the production of thick annular preforms from carbon fibers or oxidized polyacrylonitrile (PAN). The preforms are then carbonized and then densified with carbon by processes such as vapor phase infiltration or the impregnation of carbon precursor liquids, to fill the porosities of the preform.

Patent FR 2 726 013 describes, for example, such a manufacturing process in which annular preforms of oxidized PAN fibers or carbon fibers are manufactured by successive needling of layers. Nevertheless, this manufacturing process generates a large quantity of needled textile scrap, which can be up to 50% of the raw material used.

It is therefore desirable to have a fibrous structure for the production of these fibrous preforms making it possible to reduce the quantity of textile scraps.

The invention relates to a needled fibrous structure for producing an annular fibrous preform for a brake disc comprising:

- a core formed of at least two layers of fibers needled together, each layer comprising continuous fibers; And

- at least one layer of non-woven staple fibers needled on a lower or upper face of the core.

The needling of the layers forming the core and of the layer of nonwoven discontinuous fibers (layer also called "nonwoven") on the lower and/or upper layer of the core makes it possible to give the fiber preform the necessary cohesion to eliminate the risk of delamination during subsequent handling of the preform. It also provides interlaminar mechanical strength to brake discs made from this fibrous structure.

The non-woven staple fibers can come from textile scraps, which makes it possible to reduce the rate of virgin raw material to be used.

According to a particular characteristic of the invention, the fibers of each layer of nonwoven staple fibers have a length greater than or equal to 4 mm. This length allows sufficient bonding between the fibrous layers of the core and the layers of non-woven staple fibers present on the lower and/or upper face of the core.

According to another particular characteristic of the invention, each layer of nonwoven staple fibers has a basis weight of less than 1700 g/m². This makes it possible to subsequently obtain fibrous reinforcements with an appropriate thickness for braking applications.

According to another particular characteristic of the invention, each layer of nonwoven discontinuous fibers has a volume content of fibers of less than 20%. The fiber volume ratio is the fraction of the apparent volume of the felt actually occupied by the fibers in the relaxed state, i.e. before compression due to needling.

These values of surface mass and density of fiber also make it possible not to complicate the steps of densification of the fibrous preform obtained from the fibrous structure according to the invention.

According to another characteristic of the invention, each layer of non-woven staple fibers comes from the recycling of textile scraps of oxidized polyacrylonitrile PAN or carbon fibers.

Another object of the invention is a process for manufacturing a needled fibrous structure according to the invention comprising:

- the production by needling of a core of the fibrous structure, the core comprising at least two layers of fibers, each layer comprising continuous fibers; And

- the needling of at least one layer of non-woven staple fibers on at least one lower or upper face of the core.

Yet another object of the invention is a process for manufacturing a part made of composite material comprising a fibrous preform densified by a matrix, the process comprising at least the following steps:

- the manufacture of a needled fibrous structure intended to form at least one fibrous preform of the part by a process according to the invention;

- the formation of a matrix in the porosity of the needle-punched fibrous structure; And

- the elimination of each layer of non-woven discontinuous fibers present on at least one lower or upper face of said core.

According to a particular characteristic of the invention, the manufacturing step also comprises a cutting of the needle-punched fibrous structure so as to form a fibrous preform of the part.

Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate examples of embodiments without any limiting character.

FIG. 1 schematically and partially represents an exploded view of a fibrous structure according to one embodiment of the invention.

FIG. 2 schematically and partially represents a method of manufacturing a fibrous structure according to the invention.

FIG. 3 represents, schematically and partially, a process for manufacturing a composite material part comprising a fibrous preform resulting from the fibrous structure according to the invention.

FIG. 4 schematically and partially represents a plurality of fibrous preforms resulting from the fibrous structure according to the invention.

FIG. 1 schematically and partially represents an exploded view of a fibrous structure 100 according to one embodiment of the invention.

The fibrous structure 100 comprises a core 130 having a lower face 120 and an upper face 110. The core 130 comprises four fibrous layers 131, 132, 133 and 134 of needled fibers. Layers 131-134 include continuous fibers.

A layer of nonwoven staple fibers 111 is present on the upper face 110 of the core 130, and another layer of nonwoven staple fibers 112 is present on the lower face 120 of the core 130. The two layers of staple fibers nonwovens 111 and 112 are needled respectively on the lower 120 or upper 110 face.

The fibrous structure 100 can be obtained in different ways. It can come from a fibrous plate composed of layers of fibers in which are cut several annular fibrous structures intended to form annular preforms.

It can be obtained by draping, for example by superimposing annular fibrous layers. In particular, this makes it possible to obtain a preform with an almost definitive shape or “Near Net Shape” preform, which means that there is no cutting apart from peripheral and central machining to obtain a preform with the desired dimensions.

It can also be obtained from a helical fibrous structure, then making it possible to obtain an annular preform by winding, also of the “Near Net Shape” type.

Depending on the shape of the final part and/of the desired fibrous preform, the shape and/or the dimensions of the fibrous structure are adapted. For example, for a part of annular shape, the fibrous structure may have an annular shape; or for a part of polygonal shape, the fibrous structure may also have a polygonal shape.

FIG. 2 schematically and partially represents a method of manufacturing a fibrous structure according to the invention.

The manufacturing process 200 firstly comprises the production by needling 201 of the core of the fibrous structure, then the needling of at least one layer of nonwoven discontinuous fibers 202 on the lower and/or upper face of the 'soul.

The needling 201 of the layers of the core can be carried out on a plane-type needling machine according to the process described in patent FR 2 726 013.

The needling 201 of the layers of the core can also be carried out on another plane-type needling machine, or even a helical needling machine.

The needling 202 of the layers of staple fibers on the lower and/or upper face of the core is carried out after superimposing these layers on the core. They are therefore linked to one of the faces of the core of the fibrous structure only after passing under the needling machine. As for step 201, this needling 202 can be performed on any plane-type needling machine, or on a helical needling machine.

FIG. 3 schematically and partially represents a process for manufacturing a composite material part comprising a fibrous preform densified by a matrix according to the invention. The process 300 firstly comprises the manufacture 301 of a needle-punched fibrous structure intended to form at least one fibrous preform of the part by a manufacturing process as described previously. Then, a matrix 302 is formed in the pores of the needle-punched fibrous structure. Finally, each layer of nonwoven discontinuous fibers 303 present on at least one lower or upper face of the core of the fibrous structure is eliminated.

Manufacturing 301 can also include a cutting of the needle-punched fibrous structure which will be intended to form a fibrous preform. Figure 4 gives an example of cutting the needled fibrous structure.

In the example of FIG. 4, a needled fiber structure 400 is manufactured in the form of a plate, then this plate is cut so as to obtain several needled fiber structures 410, 411, 412 and 413 intended to form fiber preforms. In the example of Figure 4, these cut fibrous structures are annular in shape and can form annular fibrous preforms. The cutting of the fibrous structure can, for example, be carried out by a cutting press.

The formation of the matrix 302 in the pores of the fibrous structure is carried out in a manner known per se. It can thus be carried out by liquid route (impregnation with a precursor resin of the matrix and transformation by cross-linking and pyrolysis, the process being able to be repeated), or by gaseous route (chemical infiltration in the vapor phase of the matrix), or even by infiltration. in the molten state.

The elimination 303 of the layers of non-woven discontinuous fibers makes it possible to obtain a composite material part consisting of structural layers formed at least in part of continuous fibers and to guarantee homogeneous properties of this part in its thickness (axis Z in FIG. 1 ).

This elimination 303 can be carried out by machining operations. For example, it can be made on a machining center or lathe using diamond cutting tools. This elimination makes it possible to machine the lower and/or upper faces of the disc until the desired disc thickness is obtained geometrically.

According to another embodiment of the invention, the fibrous structure 100 comprises only a single layer of nonwoven staple fibers needled on the lower face 120 or upper face 110 of the core 130.

According to another embodiment of the invention, the number of layers of nonwoven staple fibers on one of the faces of the core 130 is greater than 1.

According to a particular characteristic of the invention, the fibers of each layer of nonwoven staple fibers have a length greater than or equal to 4 mm.

According to another particular characteristic of the invention, each layer of nonwoven staple fibers has a basis weight of less than 1700 g/m².

According to another particular characteristic of the invention, each layer of nonwoven discontinuous fibers has a volume content of fibers of less than 20%.

According to another particular characteristic of the invention, each layer of nonwoven discontinuous fibers has a homogeneous fiber content in the plane (plane formed by the X and Y axes of FIG. 1). This makes it possible to subsequently obtain the most isotropic fibrous reinforcement possible in this plane, particularly in terms of thickness under load. For example, for a thickness measurement under load of 50 kPa of a layer of non-woven staple fibres, the coefficient of variation measured for this layer must not exceed 20%.

According to another particular characteristic of the invention, the fibers forming the layers of the core 130 are made of oxidized polyacrylonitrile PAN or carbon.

According to another particular characteristic of the invention, the layers of fibers forming the core 130 are produced by layers of fabrics made up of yarns made up of continuous fibers, or are made up of several layers of unidirectional cables arranged in different directions and linked together them by light needling.

According to another particular characteristic of the invention, the nonwoven discontinuous fibers are made of oxidized polyacrylonitrile PAN or carbon.

According to another particular characteristic of the invention, each layer of nonwoven discontinuous fibers comes from the recycling of textile scraps of oxidized polyacrylonitrile PAN or carbon fibers.

According to another particular characteristic of the invention, the layers of nonwoven discontinuous fibers are produced by a dry process or by an Airlaid-type process or by a paper process.

According to a first exemplary embodiment, the structure 100 comprises on each of the lower and upper faces of the core 130, two layers of nonwoven discontinuous fibers with a surface weight of 200 g/m². These two layers are made by dry process from recycled fibers from oxidized PAN textile scraps. Its core 130 comprises 17 layers of continuous fibers consisting of unidirectional sheets superimposed in different directions and bonded together by pre-needling. For example, the 17 layers include three layers oriented at 0°, +60° and -60°. The two layers of staple fibers are needled on the lower and upper faces when they are positioned on these faces.

In this first example, during needling of the assembly, the initial needle penetration is 11.1 mm ± 0.25 mm and the needling density is 30 strokes/cm² (-4/+2 ). The needling descent step is adjusted and not constant, it is defined by:

• 2 displacement steps at 1.8 mm ± 0.05 mm;
• 10 steps of movement at 1.7 mm ± 0.05 mm;
• 5 displacement steps at 1.6 mm ± 0.05 mm; And
• 2 displacement steps at 0.1 mm ± 0.05 mm.

According to a second exemplary embodiment, the structure 100 comprises on each of the lower and upper faces of the core 130, a layer of non-woven discontinuous fibers with a surface mass of 1000 g/m². As before, the layers of staple fibers are produced by the dry process from recycled fibers obtained from textile scraps of oxidized PAN. The core 130 comprises 17 layers of continuous fibers made up of unidirectional plies superimposed in different directions, the plies being bonded together by pre-needling. The two layers of staple fibers are needled on the lower and upper faces when they are positioned on these faces.

In this second example, during needling of the assembly, the initial penetration of the needle is 8.5 mm ± 0.25 mm and the needling density is 30 strokes/cm² (-4/+2 ). The step of descent of the needle is adjusted and not constant, it is defined by:

• 6 displacement steps at 1.7 mm ± 0.05 mm;
• 6 displacement steps at 1.6 mm ± 0.05 mm; And
• 5 displacement steps at 1.5 mm ± 0.05 mm.

According to a third exemplary embodiment, the structure 100 comprises on each of the lower and upper faces of the core 130, a layer of non-woven discontinuous fibers with a surface mass of 400 g/m². As before, the layers of staple fibers are produced by the dry process from recycled fibers obtained from textile scraps of oxidized PAN. The core 130 comprises 17 layers of continuous fibers made up of unidirectional plies superimposed in different directions, the plies being bonded together by pre-needling. The two layers of staple fibers are needled on the lower and upper faces when they are positioned on these faces.

In this third example, during needling of the assembly, the initial penetration of the needle is 11.1 mm ± 0.25 mm and the needling density is 30 strokes/cm² (-4/+2 ). The needling descent step is adjusted and not constant, it is defined by:

• 2 displacement steps at 1.8 mm ± 0.05 mm;
• 10 steps of movement at 1.7 mm ± 0.05 mm;
• 5 displacement steps at 1.6 mm ± 0.05 mm; And
• 2 displacement steps at 0.1 mm ± 0.05 mm.

The example illustrated in FIG. 1 and the method described in FIG. 2 relate to a fibrous structure for producing an annular fibrous preform for a brake disc, but the scope of the invention is not departed from when the fibrous structure is used to the production of an annular fibrous preform that can be used for molding with an almost final shape, or Near Net Shape in English.

The needling densities, the initial penetrations of the needle and the pitches described in the three preceding examples are chosen according to the characteristics desired for the fibrous reinforcements, included in the final part made of composite material, and obtained from the structure fiber of the invention. For example, these characteristics can be a fiber content along the Z axis, a particular thickness of the final part, a particular thickness of the layers of the core 130 of the fibrous structure 100, an overall fiber content, and/or a specific weight for the final part or the layers forming the fibrous structure, etc.

Claims (8)

Needle-punched fibrous structure (100) for producing an annular fibrous brake disc preform comprising:

• a core (130) formed of at least two fibrous layers (131, 132, 133, 134) of needled fibres, each layer comprising continuous needled fibres; And
• at least one layer of nonwoven staple fibers (111, 112) on a bottom (120) or top (110) face of the core.

A needlepunched fibrous structure according to claim 1, wherein the fibers of each layer of nonwoven staple fibers have a length greater than or equal to 4 mm. A needlepunched fibrous structure according to any of claims 1 or 2, wherein each layer of nonwoven staple fibers has a basis weight of less than 1700gsm. A needlepunched fibrous structure according to any one of claims 1 to 3, wherein each layer of nonwoven staple fibers has a fiber volume content of less than 20%. Needle-punched fibrous structure according to any one of claims 1 to 4, in which each layer of non-woven discontinuous fibers comes from the recycling of textile scraps of oxidized polyacrylonitrile PAN or carbon fibers. Method of manufacturing (200) a needled fibrous structure according to any one of claims 1 to 5 comprising:

• the production (201) by needling of a core of the fibrous structure, the core comprising at least two fibrous layers of fibers, each layer comprising continuous fibers; And
• needling (202) at least one layer of nonwoven staple fibers on at least one bottom or top face of the core.

Method for manufacturing (300) a part made of composite material comprising a fibrous preform densified by a matrix, the method comprising at least the following steps:

• the manufacture (301) of a needled fibrous structure intended to form at least one fibrous preform of the part by a method according to claim 6;
• forming (302) a matrix in the porosity of the needle-punched fibrous structure; And
• removing (303) each layer of nonwoven staple fibers present on at least one lower or upper face of said core.

Method of manufacturing a part according to claim 7, in which the manufacturing step also comprises cutting the needle-punched fibrous structure (400) so as to form a fibrous preform (410, 411, 412, 413) of the part .