Method for manufacturing a fibrous preform of a brake disc with improved service life

Abstract

The invention relates to a method for manufacturing a fibrous reinforcement of a composite brake disc, which comprises: - producing (E10) fibrous portions (11), each intended to define a friction face (F1) separate from the brake disc, using a custom fibre placement technique in which, for each of the portions, carbon or carbon precursor fibres are deposited on a substrate and stitched thereto by a sewing thread made of carbon or polymeric material; - positioning (E20) an intermediate fibrous portion (13), intended to define a non-friction area of the brake disc, between the portions; and - joining (E30) the intermediate fibrous portion (13) to the fibrous portions (11).

Description

Description Title of the invention: Method for manufacturing a fiber brake disc preform with improved service life Technical Field

[0001] The present disclosure relates to a method for manufacturing a fiber preform of a brake disc in which at least the friction zones are produced by a tailor-made fiber placement technique (TFP) so as to increase the Z-shaped fiber ratio and the heat dissipation capacity in operation. The invention also relates to the manufacture of an associated brake disc. Prior art

[0002] It is desirable to have brake discs with improved lifespan. Statement of the invention

[0003] This disclosure relates to a method for manufacturing a fiber preform intended to form the fiber reinforcement of a brake disc made of composite material, comprising: - the production of a first fibrous portion and a second fibrous portion, each intended to define a distinct friction face of the brake disc, by a tailor-made fiber placement technique in which, for each of the first and second portions, carbon or carbon precursor fibers are deposited on a substrate and sewn to the latter by a carbon or polymeric material sewing thread, - the positioning of an intermediate fibrous portion, intended to define a non-friction zone of the brake disc, between the first and second fibrous portions, and - the assembly of the intermediate fibrous portion to the first and second fibrous portions.

[0004] The custom fiber placement technique will be referred to as the “TFP technique” in the following.

[0005] The invention relates to the use of the TFP technique for the manufacture of friction faces of the brake disc by choosing, for the sewing threads, carbon or polymeric material threads which make it possible to increase the rate of Z fibers and thus to have more heat dissipation channels to limit heating of the disc in operation, and thus increase its lifespan. The sewing threads have a Z component and allow, by their mere presence, to increase the Z fiber rate. The materials used for these threads also give them the ability to be transferred in Z and, without the invention being limited to this variant, the assembly to the non-friction portion can be carried out by Z transfer of the sewing threads, as will be detailed below. In addition, the implementation of the TFP technique advantageously makes it possible to reduce material losses and additional machining during the manufacture of the preform compared to the case where the discs are cut from a block of material obtained beforehand. The TFP technique makes it possible to obtain the final shape or a shape very close to it directly after deposition ("near-net shape").

[0006] In one example, the assembly is carried out by needling.

[0007] Needling allows the sewing threads to be transferred in a Z pattern.

[0008] In particular, each of the first and second portions may have, after assembly, a rate of transferred Z-shaped sewing threads of between 1% and 8%. This characteristic corresponds to the contribution of the sewing threads, used in the TFP technique, to the rate of Z-shaped fibers.

[0009] The fiber rate in Z (noted TFZ) in a given zone is a quantity known to those skilled in the art; it corresponds to the volume of fibers extending along the thickness of the preform (Z direction) relative to the volume of the preform. The fiber rate in Z can be determined by morphological analysis (image analysis). In this case, sections are made in the XY plane, the fibers are therefore transverse to this plane and the surface area of ​​the fibers is counted in order to deduce the fiber rate in Z. The fiber rate in Z corresponds to the sum of the fiber sections in Z over the total surface area of ​​the analyzed zone (fibers + porosity). A tomographic analysis (non-destructive method) can also be used to determine the fiber rate in Z.

[0010] The invention is however not limited to the production of an assembly by needling and other techniques can be used. Thus the assembly can be produced by tufting according to a variant of the invention.

[0011] In one example, the sewing threads are made of carbon.

[0012] Alternatively, the sewing threads are made of carbon precursor polymer.

[0013] In one exemplary embodiment, the substrate is a veil of carbon or a carbon precursor material.

[0014] The present disclosure also relates to a method of manufacturing a composite brake disc, comprising (a) manufacturing a fibrous preform by implementing a method as described above, and (b) densifying the preform by a matrix. The brake disc can be made of carbon / carbon composite material. The brake disc can be fitted to a vehicle, such as an aircraft, for example an airplane or a helicopter. Brief description of the drawings [Fig. 1] Figure 1 is a flowchart illustrating a succession of steps in the context of an example of a method according to the invention. [Fig. 2] Figure 2 illustrates, schematically, a section of an example of a first or second fibrous portion usable within the framework of the invention taken along its thickness. [Fig. 3] Figure 3 schematically illustrates the production of the first or second fibrous portion using the TFP technique. [Fig. 4] Figure 4 schematically illustrates the positioning of the intermediate fibrous portion between the first and second fibrous portions. [Fig. 5] Figure 5 illustrates, schematically, a section of an example of a fiber preform according to the invention taken along its thickness. Description of the embodiments

[0015] 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.

[0016] The first fibrous portion and the second fibrous portion, each intended to define a distinct friction face of the brake disc, are produced by TFP technique (step E10). During the production of each of the first and second portions, fibers are deposited on a substrate and sewn to the latter by a sewing thread made of carbon or polymeric material.

[0017] Figure 2 schematically illustrates a fibrous portion 11 intended to define a rubbing face (first or second aforementioned fibrous portion) obtained by TFP technique. The portion 11 comprises several superimposed fibrous layers 111 sewn to the same substrate. The substrate has not been shown in Figure 2.

[0018] The production of the portion 11 by implementing the TFP technique is illustrated in Figure 3. A wick 111a, formed of a plurality of filaments, is deposited on a substrate S while being sewn to the latter by a sewing thread 111b as it is deposited. The wick 111a is unwound through a guide element EG which here has two openings OEG1, OEG2 which are successively crossed by the wick 111a to be deposited. A sewing needle A driven by a transverse movement to the substrate S, and driving the thread 111b, sews the wick 111a to the substrate S.

[0019] The sewn wick 111a is deposited in a plane P defined by the X and Y directions so as to form a first layer 111. Within the same layer 111, the sewn wick 111a can be oriented in a single direction, or in several distinct directions as in the example illustrated in FIG. 3. The deposition of the wick 111a is continued so as to obtain the entirety of the desired surface for the layer 111. Once a first layer 111 is completed, the deposition of a second layer 111 covering the first layer 111 is initiated and carried out in a manner similar to that which has just been described. The method is thus continued, with the desired number of layers 111. Several thicknesses of wick 111a are thus stacked to form the portion 11. The orientations of the wick 111a between two distinct layers 111 can be identical or different.

[0020] The first and second fibrous portions 11 are positioned on either side of an intermediate fibrous portion 13 which is intended to define a non-friction zone of the brake disc (step E20, FIG. 4). The portion 13 may also have been obtained by TFP technique, or by a conventional technique of superposition and needling of fibrous sheets. The substrate S on which each portion 11 has been sewn is not illustrated in FIG. 4. This substrate S may be formed of a material intended to remain in the brake disc obtained after densification by a matrix. Thus the substrate S may be a carbon veil or a carbon precursor material such as oxidized or non-oxidized polyacrylonitrile. According to a variant, the substrate S may be made of a fugitive material intended to be eliminated during a heat treatment subsequent to the formation of the fibrous reinforcement. In this case, the substrate S may be a polyvinyl alcohol (PVA) veil.

[0021] The portion 13 comprises several superimposed fibrous layers 131. The layers 131 may be unidirectional or multidirectional fibrous layers. The intermediate portion may comprise a peripheral circumferential zone comprising at least tenon zones 14.

[0022] The fibers forming portions 11 and 13 may be carbon fibers, for example carbon fibers marketed under the reference HexTow® AS4, or fibers of a carbon precursor such as polyacrylonitrile, possibly oxidized or not.

[0023] The portion 13 can then be assembled to the portions 11 by Z-shaped transfer of fibers 15 from the portions 11 and / or 13 (step E30, figure 5). This transfer is carried out by implementing techniques known per se such as needling. Needling is a mechanical bonding method known per se in which a fibrous structure is crossed with barbed needles to which the fibers cling. This results in a transfer of fibers from one fibrous layer to another in the Z direction, i.e. along the thickness of the preform, thus creating mechanical bonds between the fibrous layers in this direction. According to a variant, the assembly (E30, figure 5) of the portion 13 to the portions 11 is carried out by tufting, it being understood that the needling and tufting techniques can be combined.

[0024] This gives the brake disc preform 1 shown in Figure 5.

[0025] The fiber preform 1 may have an annular shape around a central through orifice 20. The portions 11 are each intended to define a distinct friction face F1 of the brake disc. The portions 11 are surface portions of the fiber preform 1. The thickness ell of each of the portions 11 may be between 10% and 25%, for example between 15% and 25%, of the total thickness el of the fiber preform 1. The thickness ell may be between 2 mm and 20 mm. The portion 13 may define the central part of the thickness of the fiber preform 1.

[0026] Figure 5 illustrates vertical assembly wires 15 extending along the Z direction, for example over the entire thickness of the fiber preform 1, which make it possible to assemble the layers 111 of the portions 11 to the layers 131 of the portion 13. As visible in Figure 5, the portion 13 has a larger dimension greater than a larger dimension of the portions 11, thus defining tenon zones 14 which protrude from the portions 11 (see Figure 5). The tenon zones 14 are intended to define tenons of the brake disc cooperating with the notches of the wheel to be braked. Unless otherwise stated, the largest dimensions are taken perpendicular to the Z direction. The thickness el3 of the portion 13 may be greater than the thickness of each of the portions 11. The thickness el3 of the portion 13 may be between 50% and 90% of the total thickness el of the fiber preform 1. The thickness el3 may be between 10 mm and 40 mm.The fiber preform 1 comprises the superposition of several fiber layers 111 and 131. The fiber preform 1 is not helical in shape. Generally, the thickness el of the fiber preform 1 may be between 15 mm and 50 mm. It will also be noted that the preform 1 may be symmetrical with respect to a plane of symmetry perpendicular to the Z direction, which makes it possible to make the deformations under thermal loading more homogeneous.

[0027] The fiber preform 1 is intended to form the fiber reinforcement of a brake disc, in particular a brake disc made of carbon / carbon composite material. The brake disc can be integrated into an aircraft, such as an airplane or a helicopter.

[0028] The process can continue by densifying the preform 1 with a matrix (step E40), for example a carbon matrix. In the case where there is the presence of carbon fibers, carbon precursor, pyrolysis of this precursor can be carried out to transform them into carbon before introducing the matrix material into the porosity of the preform 1.

[0029] The densification step is a step known per se. The matrix can be obtained in whole or in part by chemical vapor infiltration (“CVI”) or by polymer impregnation and pyrolysis (“PIP”). These two techniques can be combined if desired. Finish machining can then be carried out and protective compositions applied to the surface of the brake disc, for example to improve its resistance to oxidation and then integrate it into a vehicle braking assembly, in a manner known per se.

Claims

Claims

1. Method for manufacturing a fibrous preform (1) intended to form the fibrous reinforcement of a brake disc made of composite material, comprising: - the production (E10) of a first fibrous portion (11) and a second fibrous portion (11), each intended to define a separate friction face (F1) of the brake disc, by a tailor-made fiber placement technique in which, for each of the first and second portions, carbon or carbon precursor fibers are deposited on a substrate and sewn to the latter by a carbon or polymeric material sewing thread, - the positioning (E20) of an intermediate fibrous portion (13), intended to define a non-friction zone of the brake disc, between the first and second fibrous portions, and - the assembly (E30) of the intermediate fibrous portion to the first and second fibrous portions.

2. Method according to claim 1, in which the assembly (E30) is carried out by needling.

3. Method according to claim 2, in which each of the first (11) and second (11) portions has, after assembly (E30), a rate of stitching threads transferred in Z of between 1% and 8%.

4. A method according to claim 1, wherein the assembly (E30) is carried out by tufting.

5. A method according to any one of claims 1 to 4, wherein the sewing threads are carbon.

6. A method according to any one of claims 1 to 4, wherein the sewing threads are made of carbon precursor polymer.

7. A method according to any one of claims 1 to 6, wherein the substrate is a veil of carbon or a carbon precursor material.

8. A method of manufacturing a brake disc made of composite material, comprising (a) manufacturing a fibrous preform (1) by implementing a method according to any one of claims 1 to 7, and (b) densifying (E40) the preform by a matrix.

Images