Chemical vapor infiltration densification method using a single stacked plate for semi-forced flow

Abstract

The present invention relates to a method for densifying a porous annular substrate (21) having a central channel (21a) by chemical vapor infiltration, the method comprising at least the following steps: providing a stack (20) of porous annular substrates (21); providing a plurality of individual modules (30), the individual modules (30) comprising a stack (20) disposed on a support plate (31), each support plate having a perforated injection tube (33), each injection tube being mounted on a gas inlet opening (32); forming a stack of individual modules (30), aligning the individual modules (30) of the stack in a sealed manner by means of an annular seal (35) disposed between the injection tube (33) of a second individual module (30b) and the gas inlet opening (32) of a cooperating first individual module (30a), and injecting a gas phase into the internal volume (24) of each stack (20) of porous annular substrates (21), the gas phase comprising a gaseous precursor of a matrix material to be deposited in the pores of the substrate (21).

Description

Technical Field

[0001] The present invention relates to the production of composite parts comprising a porous annular substrate densified by chemical vapor infiltration (CVI), and more particularly to the production of parts having a central channel.

[0002] The present invention is particularly but not limited to the production of annular brake friction discs or divergent nozzles of rocket engines made of thermostructural composite materials. Background Art

[0003] Thermostructural composite materials are notable for their excellent mechanical properties and their ability to maintain these properties at high temperatures. Typical examples of thermostructural composite materials are carbon-carbon (C-C) composites, which comprise a porous reinforcing substrate of carbon fibers densified by a carbon matrix, and ceramic matrix composites (CMCs), which comprise a porous reinforcing substrate of refractory fibers (such as carbon or ceramic) densified by a ceramic matrix (such as silicon carbide).

[0004] C-C composites are commonly used in aircraft brake friction discs because of their high-energy friction characteristics, non-brittle nature, thermal properties (conductivity and heat capacity), and density.

[0005] Densification of a porous substrate by chemical vapor infiltration (CVI) involves placing an annular preform in the reaction chamber of an infiltration device and introducing into the reaction chamber a gas phase, one or more of whose components form precursors of the matrix material, to be deposited in the substrate to ensure its densification. The infiltration conditions are selected, in particular the composition and flow rate of the gas phase, and the temperature and pressure in the chamber, to allow the gas phase to diffuse into the accessible internal pores of the substrate, so that the desired material is deposited therein by decomposition of the gas phase components or by reaction between several of its components. Document FR 2,834,713 describes such a method and the device for implementing it.

[0006] Those skilled in the art have long known the conditions for chemical vapor infiltration of pyrolytic carbon. The carbon precursors are alkanes, alkyls or alkenes, usually propane, methane or a mixture of both. For example, the infiltration is carried out at a temperature of about 1000 °C and a pressure of about 1 kPa.

[0007] A gas phase containing precursors of the material to be deposited in the preform is introduced at one longitudinal end of the reaction chamber, while the residual gas is evacuated at the opposite end and withdrawn from this end by a pumping device.

[0008] Reactors for carrying out infiltration studies and R&D for brake friction discs have a loading configuration, usually consisting of a stack of plates, each plate carrying a stack of discs. These are so-called "single-stack" furnaces. This configuration is different from the industrial load produced in large reactors, where the plates carry several stacks of discs side by side, i.e., so-called "multi-stack" furnaces.

[0009] In both cases, the disks are separated by intermediate supports called spacers, the plates include openings aligned with the central channels of the disks so that the reactive gas phase circulates in each stack and then the reactive gas phase passes through the disks to densify them. The upper plate is located above the load and encloses the internal space of each stack. The plates supporting the disk stacks are fixed by vertical rods.

[0010] The traditional densification method used industrially and suitable for R & D furnaces is directed flow.

[0011] Figure 1 A known example of a single-stack disk load that can be used in a reaction chamber (commonly referred to as a "densification furnace") is shown.

[0012] The chamber 1 has cylindrical symmetry about the axis Z. The load includes a stack of individual modules 2, each individual module 2 including a single stack 3 of porous annular substrates 4 supported by a lower support plate 5. The plate 5 includes an opening 6 aligned with the central channel 7 of the substrate 4 so that the reactive gas phase circulates in each stack 3, and the reactive gas phase then passes through the substrate 4 to densify it. An annular cover disk 8 is installed above each stack 3, and each individual module 2 also includes a vertical rod 9 extending between the support plate 5 of the individual module 2 and the support plate 5 of the upper individual module 2. The vertical rod 9 is used to bear the mass of the upper support plate 5, so as to ensure that the support plate 5 remains in place.

[0013] Figure 1 It is a schematic diagram of the hot zone of a directed flow load. The hot zone from bottom to top includes: an inlet 10 for the reaction gas mixture, then a preheating zone 11 which can raise the gas temperature to the densification temperature, and finally a load zone 12. At the top of the furnace, at the base cover 13, a chimney 14 is installed in the cover 13, and the exhaust gas generated by the deposition reaction is discharged through the chimney 14.

[0014] On each plate 5, there is a stack of substrates 4 separated by spacers 15, and at the top of each stack there is a cover disk 8 that limits leakage.

[0015] The gas at the end of the preheating zone 11 enters each column formed by the stack 3 of substrates 4. The gas leaks from the inside to the outside of the column of substrates 4 via the pores of each preform 4, the gaps generated between the substrates 4 by the spacers 15, and the channels between the plates 5.

[0016] Document FR 2,821,859 discloses a chemical vapor infiltration densification method for porous substrates, especially using semi-forced flow. In order to adapt to the semi-forced flow described in this document, it is necessary to control the leakage between the substrates and also to control the leakage of the inter-plate channels. In other words, in addition to controlling the leakage related to the porosity of the preform 4, controlling other leakages can improve the densification kinetics: this is the implementation of the so-called "semi-forced flow" method.

[0017] The implementation of semi-forced flow involves providing calibrated leak channels between the inside and outside of the substrate column, which involves sealing the free areas left when implementing the method of directed current flow: these areas are particularly located at the joints between the inter-disk spacers and between the lower stack and the support plate of the upper individual module.

[0018] As the preform densifies between the inside (where the gas arrives) and the outside of the stack, a pressure gradient will be established and increase. The installation of calibrated leaks must allow this pressure gradient to be limited to avoid soot deposition inside the substrate stack due to excessive pressure. Therefore, monitoring the pressure gradient reflecting the progress of densification is necessary for the cycle to proceed.

[0019] Leakage in the inter-plate channels is the most difficult to control because the stack heights of the porous annular substrates are not the same. If the sealing at the top of each stack cannot be well controlled, the pressure difference required to force the gas into the pores of the substrate 2 cannot be obtained.

[0020] It is also known from patent FR 3,084,892 that replacing the rod with a gas distributor makes it possible to simultaneously perform the functions of bearing the load (previously performed by the rod), guiding the gas (cold), which avoids cooling the disks, and gas distribution at the preform level. Summary of the Invention

[0021] The object of the present invention is to provide a technical solution for implementing a densification method, which can improve the distribution of reaction gases in the load zone of the densification furnace and generally reduce the densification gradient between substrates located at different positions in the load zone without affecting the load capacity of the furnace or even increasing its load capacity.

[0022] An object of the present invention proposes a densification method for chemically vapor infiltrating a porous annular substrate with a central channel through a pressure gradient, the method comprising at least the following steps:

[0023] - Providing a stack of a plurality of porous annular substrates, each stack comprising an internal volume formed by the central channels of the stacked substrates,

[0024] - Providing a plurality of individual modules, each individual module comprising a support plate and a single stack of porous annular substrates arranged on the support plate, the support plate having a gas inlet opening and an injection tube mounted on the gas inlet opening, the injection tube extending into the internal volume of the stack between a first tube end connected to the support plate and a free second tube end, and the injection tube further comprising gas injection holes leading to the internal volume,

[0025] - Form a stack of individual modules in the chamber of the densification furnace, with each first individual module stacked on a second individual module. The gas inlet opening of the support plate of the first individual module communicates with the second end of the injection tube of the second individual module on which it is stacked, to allow gas to circulate between the individual modules, and

[0026] - Inject a gas phase containing a gaseous precursor of a matrix material to be deposited in the pores of the substrate into the internal volume of each stack of porous annular substrates.

[0027] According to the general features of the present invention, in each individual module, each first porous annular substrate is supported on a second porous annular substrate or on a support plate by a sealing ring, which provides a radial seal between the first porous annular substrate and the second porous annular substrate or between the first porous annular substrate and the said support plate.

[0028] In other words, each individual module includes a plurality of sealing rings, each sealing ring being placed in the support between two consecutive porous annular substrates or between the porous annular substrate and the support plate.

[0029] "Radial seal" is understood to mean a seal that prevents gas from circulating radially between the internal volume of the stack and the outside of the stack.

[0030] Thus, the present invention can better control the circulation of gas around the porous annular substrate, thereby improving the gas distribution in the furnace chamber.

[0031] Furthermore, in each individual module, each sealing ring is coupled to an annular spacer, the inner diameter of which is equal to the inner diameter of the porous annular substrate.

[0032] The annular spacer allows the sealing ring to be centered, thus facilitating its positioning.

[0033] The thickness of each annular spacer is less than the thickness of the sealing ring to which it is coupled. The advantage of this thickness ratio is to ensure that the porous annular substrate is supported on the sealing ring. This ensures the radial seal. In addition, this thickness ratio has the advantage of allowing the gas phase to circulate freely around the porous annular substrate.

[0034] In an exemplary embodiment, each stack includes at least one cover plate, which is supported on the porous annular substrate at the top of the stack by a sealing ring, which provides a radial seal between the cover plate and the said porous annular substrate at the top of the stack.

[0035] Each stack may also include a deformable annular seal, which is arranged to be compressed between the cover plate and the support plate of the upper individual module.

[0036] The deformable annular seal is made of, for example, carbon fiber felt.

[0037] In addition, each stack may further include an expanded graphite disk disposed between the deformable annular seal and the support plate of the upper individual module. The expanded graphite disk prevents the deformable annular seal from sticking to the upper support plate.

[0038] According to the first embodiment, in each individual module, the sealing ring is disposed on the radially outer periphery of the porous annular substrate.

[0039] According to the second embodiment, in each individual module, the sealing rings are alternately disposed on the radially outer periphery and the radially inner periphery of the porous annular substrate along the stacking direction of the porous annular substrates.

[0040] These two embodiments can maximize the contact surface of the porous annular substrate with the gas phase.

[0041] The sealing ring is made of, for example made.

[0042] The annular spacer may also be made of made.

[0043] For example, each sealing ring is welded to the annular spacer coupled thereto. This welding helps in the formation of the stack.

[0044] According to a specific embodiment, the method further includes placing a solid lid on top of the stack of individual modules. The solid lid compresses the deformable elements, particularly the sealing rings and the deformable annular seal.

[0045] According to a specific embodiment, the method further includes a step of sealing alignment of the individual modules of the stack, including: for each first individual module stacked on a second individual module, inserting the second end of the injection tube of the second individual module into the gas inlet opening of the first individual module stacked on the second individual module, with the annular seal disposed between the second end of the injection tube of the second individual module and the gas inlet opening of the first individual module stacked on the second individual module.

[0046] In an exemplary embodiment, for each individual module, the support plate may include a first face and a second face opposite the first face, the stack of individual modules is disposed on the first face, the gas inlet opening may include a frustoconical shape having a first diameter formed on the second face of the support plate and a second diameter smaller than the first diameter formed on the first face of the support plate or between the first face and the second face, and the second end of the injection tube may include a complementary frustoconical shape that mates with the frustoconical shape of the gas inlet opening.

[0047] Thus, the injection tube forms a male centering tool and the gas inlet opening forms a female centering tool, which cooperate together to ensure good centering of the individual modules with respect to each other.

[0048] Preferably, each support plate may include a centering ring on its first face, which is centered on the gas opening and shaped to receive the injection tube.

[0049] Thus, the centering ring facilitates and optimizes the assembly of the injection tube on the support plate.

[0050] In an example of the implementation of the method, the method may further include the step of setting a stack of individual modules on a carrier shell, which is arranged on the preheating zone of the densification furnace.

[0051] In an exemplary embodiment, each individual module may include an annular foot disposed between the support plate of the individual module and the stack of the porous annular substrates of the individual module. The annular foot has a radial groove that forms a channel between the central cavity of the annular foot and the outer side of the annular foot along a direction orthogonal to the direction of stacking of the porous annular substrates.

[0052] According to a specific embodiment, the step of injecting a gas phase into the internal volume of each stack includes maintaining a pressure difference between the internal volume of the stack and the outside of the stack at 0 - 100 mbar.

[0053] In an exemplary embodiment, each porous annular substrate may include carbon.

[0054] In one embodiment, each porous annular substrate may constitute a fiber brake friction disc preform. Description of the Drawings

[0055] Figure 1 Figure 1 , which has been described, very schematically shows an example of loading a porous annular substrate according to the prior art.

[0056] Figure 2 Figure 2 A cross-sectional view schematically showing an example of a stack of porous annular substrates according to the present invention is shown.

[0057] Figure 3 Figure 3 A cross-sectional view schematically showing a densification furnace according to the present invention is shown.

[0058] Figure 4 Figure 4 A top view schematically showing the annular foot is shown.

[0059] Figure 5 Figure 5 A cross-sectional view schematically showing the annular foot is shown. Detailed Description

[0060] ​​​​​​​​​​The chemical vapor infiltration densification method according to the present invention first comprises the following steps: providing a plurality of stacks of porous annular substrates to be treated by chemical vapor infiltration.

[0061] Figure 2 A cross-sectional view showing an example of a stack 20 of porous annular substrates 21 is shown. The porous annular substrates 21 have cylindrical symmetry and are stacked along a first direction Z. Each porous annular substrate 21 extends mainly in a plane perpendicular to the first direction Z. Figure 2 The cross-section shown in includes a first direction Z and a second direction X perpendicular to the first direction Z. The first direction Z coincides with the axis of rotation of the porous annular substrate 21, and the second direction X corresponds to the radial direction.

[0062] Thus, each porous annular substrate 21 of the stack 20 has an annular shape and has a central channel 21a. Each porous annular substrate 21 is disposed on an assembly including an annular spacer 22 and a sealing ring 23. The outer diameter of the annular spacer 22 is smaller than the outer diameter of the porous annular substrate 21, and the diameter of the annular spacer 22 is equal to the diameter of the orifice of the porous annular substrate 21.

[0063] Each annular spacer 22 is surrounded by a sealing ring 23 in a plane perpendicular to the first direction Z. The thickness of the sealing ring 23 measured along the first direction Z is greater than the thickness of the annular spacer 22, so that each porous annular substrate 21 lies on the sealing ring 23. The annular spacer 22 is used to center the sealing ring 23 in the first direction Z.

[0064] The alternating stacking of the porous annular substrates 21 and the sealing rings 23 forms an internal volume 24 of the stack 20 at the center of the stack 20.

[0065] In addition, the top of the stack 20 is closed by an annular cover plate 25. The cover plate 25 is placed on the stack through the annular spacer 22 and the sealing ring 23. The stack further includes a deformable annular seal 26 made of compressed carbon fiber felt placed on the cover plate 25, and an expanded graphite disk 27 disposed on the deformable annular seal 26 to prevent the deformable annular seal 26 from adhering to the upper support plate.

[0066] The stack 20 further includes an annular secondary seal ring 28 also made of compressed carbon fiber felt, which is directly located on the annular spacer 22 supporting the cover plate 25. The secondary seal ring 28 covers the portion of the annular spacer 22 not covered by the cover plate 25.

[0067] The chemical vapor infiltration densification method according to the present invention then comprises the step of providing a plurality of individual modules 30.

[0068] Figure 3 A cross-sectional view of a densification furnace according to the present invention is schematically shown.

[0069] The densification furnace 40 according to the present invention comprises a plurality of stacks of individual modules 30. Each individual module 30 comprises a support plate 31, on which a stack 20 of porous annular substrates is provided by means of an annular foot 29, the annular foot 29 being provided between the support plate 31 and the stack 20 of the same individual module 30.

[0070] As Figure 4 and Figure 5 shown, Figure 4 and Figure 5 show a top view and a cross-sectional view of the annular foot 29, the annular foot 29 comprising a radial groove 295 which forms a passage radially between the central cavity 290 of the annular foot 29 and the outside of the annular foot 29.

[0071] As Figure 3 shown, the support plate 31 of the individual module 30 comprises a gas inlet opening 32 and an injection tube 33, the injection tube 33 being mounted on the gas inlet opening 32 and extending into the internal volume 24 of the stack 20 between a first tube end 33a connected to the support plate 31 and a free second tube end 33b.

[0072] The injection tube 33 further comprises gas injection holes 34 leading to the internal volume 24.

[0073] The chemical vapor infiltration densification method according to the present invention then comprises the step of forming a stack of individual modules 30 in the chamber of the densification furnace 40.

[0074] Figure 3 shows the support plate 31 of the first individual module 30a to be stacked on the second individual module 30b.

[0075] The step of forming a stack of individual modules 30 further comprises the step of sealing and aligning the individual modules 30 of the stack. As Figure 3 shown, in order to achieve alignment, the second end 33b of the injection tube 33 of the second individual module 30b is inserted into the gas inlet opening 32 of the first individual module 30a.

[0076] In order to seal the joint between the injection tube 33 of the second individual module 30b and the gas inlet opening 32 of the first individual module 30a, the second individual module 30a further comprises an annular seal 35 which is provided between the second end 33b of the injection tube 33 of the second individual module 30b and the gas inlet opening 32 of the first individual module 30a.

[0077] More specifically, each support plate 31 includes a first face 31a and a second face 31b opposite the first face 31a, and the stack 20 is disposed on the first face 31a. The gas inlet opening 32 has a frustoconical shape, having a first diameter d1 formed in the second face 31b of the support plate 31 and a second diameter d2 formed between the first face 31a and the second face 31b of the support plate 31, and the second diameter d2 is smaller than the first diameter d1.

[0078] The second end 33b of each injection tube 33 includes a frustoconical shape complementary to the frustoconical shape of the gas inlet opening 32, such that the two frustoconical shapes cooperate with each other. The complementary frustoconical shape of the second end 33b of the injection tube 33 includes a third diameter that is greater than a fourth diameter measured at the free end, while the first diameter is measured at the proximal end coupled to the remainder of the injection tube 33, particularly the proximal end coupled to the main portion 33c.

[0079] As Figure 3 shown, in order to improve the sealing of the stack of individual modules 30, the dimensions of the deformable annular seal 26 are designed to fill the gap between the cover plate 25 of the stack 20 of the second individual module 30b and the support plate 31 of the first individual module 30a in the first direction Z.

[0080] The chemical vapor infiltration densification method according to the present invention then includes the step of arranging the stack of individual modules 30 on a carrier shell 42, and the carrier shell 42 is arranged on the preheating zone 44 of the densification furnace 40.

[0081] The chemical vapor infiltration densification method according to the present invention then includes placing a solid lid 46 on top of the stack of individual modules 30.

[0082] The chemical vapor infiltration densification method according to the present invention then includes the step of injecting a gas phase of a gaseous precursor containing a matrix material to be deposited in the pores of the substrate 21 into the internal volume 24 of each stack 20 of the porous annular substrate 21. The injection of the gas is indicated by an arrow G in Figure 3 The step of injecting the gas into the internal volume 24 of the stack 20 preferably includes adjusting the pressure difference between the internal volume 24 of the stack 20 and the outside of the stack. The pressure difference is preferably maintained between 0 and 100 mbar. Such a range makes it possible to ensure the flow of the gas phase around the porous annular substrate 21 while avoiding the deposition of soot.

Claims

1. A method for densifying a porous annular substrate having a central channel by pressure gradient chemical vapor infiltration, the method comprising at least the following steps: - Providing a plurality of stacks of porous annular substrates, each stack including an internal volume formed by the central channels of the stacked substrates, - Providing a plurality of individual modules, each individual module including a support plate and a single stack of porous annular substrates disposed on the support plate, the support plate including a gas inlet opening and an injection tube, the injection tube being mounted on the gas inlet opening and extending into the internal volume of the stack, the internal volume being disposed on the support plate between a first tube end connected to the support plate and a free second tube end, the injection tube further including gas injection holes leading to the internal volume, - Forming a stack of individual modules in a chamber of a densification furnace, each first individual module being stacked on a second individual module, the gas inlet opening of the first individual module communicating with the second end of the injection tube of the second individual module on which it is stacked to allow gas to circulate between the individual modules, and - Injecting a gas phase into the internal volume of each stack of porous annular substrates, the gas phase including a gaseous precursor of a matrix material to be deposited in the pores of the substrate, Characterized in that, In each individual module, each first porous annular substrate is supported on a second porous annular substrate or on the support plate by a sealing ring, the sealing ring providing a radial seal between the first porous annular substrate and the second porous annular substrate or between the first porous annular substrate and the support plate, each sealing ring being coupled to an annular spacer, the inner diameter of the annular spacer being equal to the inner diameter of the porous annular substrate, each annular spacer being surrounded by the sealing ring connected thereto in a plane perpendicular to the stacking direction of the porous annular substrates, and the thickness of the annular spacer being less than the thickness of the sealing ring coupled thereto.

2. The method according to claim 1, Wherein, Each stack includes at least one cover plate, the cover plate being supported on the porous annular substrate at the top of the stack by a sealing ring, the sealing ring providing a radial seal at the top of the stack between the cover plate and the porous annular substrate.

3. The method according to claim 2, Wherein, Each stack further includes a deformable annular seal, the deformable annular seal being arranged to be compressed between the cover plate and the support plate of the upper individual module.

4. The method according to any one of claims 1 to 3, Wherein, In each individual module, the sealing ring is disposed on the outer peripheral of the porous annular substrate.

5. The method according to any one of claims 1 to 3, Wherein, In each individual module, the sealing rings are alternately disposed on the outer peripheral and the inner peripheral of the porous annular substrate along the stacking direction of the porous annular substrates.

6. The method according to any one of claims 1 to 3, Wherein, The sealing ring is made of .

7. The method according to claim 4, Wherein, The sealing ring is made of .

8. The method according to claim 5, Wherein, The sealing ring is made of and manufactured 9. The method according to any one of claims 1 to 3 and 7 to 8, Wherein, Each sealing ring is welded to the annular spacer coupled thereto.

10. The method according to any one of claims 1 to 3 and 7 to 8 further includes a step of sealing and aligning stacked individual modules, comprising: For each first individual module stacked on a second individual module, inserting a second end of an injection tube of the second individual module into a gas inlet opening of the first individual module stacked on the second individual module, and an annular seal is provided between the second end of the injection tube of the second individual module and the gas inlet opening of the first individual module stacked on the second individual module.

11. The method according to claim 9 further includes a step of sealing and aligning stacked individual modules, comprising: For each first individual module stacked on a second individual module, inserting a second end of an injection tube of the second individual module into a gas inlet opening of the first individual module stacked on the second individual module, and an annular seal is provided between the second end of the injection tube of the second individual module and the gas inlet opening of the first individual module stacked on the second individual module.

12. The method according to claim 10, wherein, For each individual module, the support plate includes a first surface supporting the stack of individual modules and a second surface opposite the first surface, the gas inlet opening includes a frustoconical shape having a first diameter formed on the second surface of the support plate and a second diameter smaller than the first diameter and formed on the first surface of the support plate or between the first surface and the second surface, and the second end of the injection tube includes a complementary frustoconical shape mating with the frustoconical shape of the gas inlet opening.

13. The method according to claim 11, wherein, For each individual module, the support plate includes a first surface supporting the stack of individual modules and a second surface opposite the first surface, the gas inlet opening includes a frustoconical shape having a first diameter formed on the second surface of the support plate and a second diameter smaller than the first diameter and formed on the first surface of the support plate or between the first surface and the second surface, and the second end of the injection tube includes a complementary frustoconical shape mating with the frustoconical shape of the gas inlet opening.

14. The method according to any one of claims 1 to 3, 7 to 8 and 11 to 13 further includes a step of arranging the stack of individual modules on a carrier shell, and the carrier shell is arranged on a preheating zone of a densification furnace.

15. The method according to any one of claims 1 to 3, 7 to 8 and 11 to 13, wherein, Each individual module includes an annular foot provided between the support plate of the individual module and the stack of the porous annular substrate of the individual module, the annular foot has a radial groove, and the radial groove forms a channel between the central cavity of the annular foot and the outside of the annular foot along a direction orthogonal to the stacking direction of the porous annular substrate.

16. The method according to claim 14, wherein, Each individual module includes an annular foot provided between the support plate of the individual module and the stack of the porous annular substrate of the individual module, the annular foot has a radial groove, and the radial groove forms a channel between the central cavity of the annular foot and the outside of the annular foot along a direction orthogonal to the stacking direction of the porous annular substrate.

17. The method according to any one of claims 1 to 3, 7 to 8, 11 to 13, and 16, wherein each porous annular substrate comprises carbon.

18. The method according to any one of claims 1 to 3, 7 to 8, 11 to 13, and 16, wherein each porous annular substrate forms a fiber brake friction disc preform.

19. The method according to claim 17, wherein each porous annular substrate forms a fiber brake friction disc preform.

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