阅读说明：本技术 分层碳纤维预制件 (Layered carbon fiber preform ) 是由 斯拉沃米尔·T·弗莱斯卡 布鲁斯·戈迪 于 2019-07-29 设计创作，主要内容包括：本发明题为“分层碳纤维预制件”。一种用于碳-碳复合材料的预制件,包括叠置并针刺在一起的多个纤维层。多个纤维层中的每个纤维层包括网状纤维和丝束纤维,网状纤维和丝束纤维各自包括碳纤维或碳-前体纤维中的至少一种。多个纤维层包括第一纤维层、第二纤维层和第三纤维层,该第三纤维层定位在第一纤维层与第二纤维层之间。第三纤维层包括以下中的至少一者：小于第一纤维层的网状纤维与丝束纤维的比率的网状纤维与丝束纤维的比率、大于第一纤维层的面积重量的面积重量、或者大于第一纤维层的预针刺厚度的预针刺厚度。(The invention provides a layered carbon fiber preform. A preform for a carbon-carbon composite comprising a plurality of fibre plies stacked and needled together. Each of the plurality of fiber layers includes mesh fibers and tow fibers, each including at least one of carbon fibers or carbon-precursor fibers. The plurality of fibrous layers includes a first fibrous layer, a second fibrous layer, and a third fibrous layer positioned between the first fibrous layer and the second fibrous layer. The third fibrous layer comprises at least one of: a ratio of reticulated fibers to tow fibers that is less than a ratio of reticulated fibers to tow fibers of the first fibrous layer, an areal weight that is greater than an areal weight of the first fibrous layer, or a pre-needling thickness that is greater than a pre-needling thickness of the first fibrous layer.)

1. A preform for a carbon-carbon composite, the preform comprising:

a plurality of fibrous layers stacked and needled together, each fibrous layer of the plurality of fibrous layers comprising:

a network fiber, wherein the network fiber comprises at least one of a carbon fiber or a carbon-precursor fiber; and

a tow fiber, wherein the tow fiber comprises at least one of a carbon fiber or a carbon-precursor fiber;

wherein the plurality of fibrous layers comprises:

a first fibrous layer;

a second fibrous layer; and

a third fiber layer positioned between the first fiber layer and the second fiber layer, wherein the third fiber layer comprises at least one of:

a ratio of mesh fibers to tow fibers that is less than the ratio of mesh fibers to tow fibers of the first fibrous layer;

an area weight greater than an area weight of the first fibrous layer; or

A pre-needling thickness greater than the pre-needling thickness of the first fibrous layer.

2. The preform of claim 1, wherein the third fiber layer comprises at least one of:

a ratio of mesh fibers to tow fibers that is less than the ratio of mesh fibers to tow fibers of the second fibrous layer;

an area weight greater than an area weight of the second fibrous layer; or

A pre-needling thickness greater than the pre-needling thickness of the second fibrous layer.

3. The preform of claim 2, wherein the first and second fiber layers each comprise substantially the same ratio of mesh fibers to tow fibers, substantially the same areal weight; and substantially the same pre-needling thickness.

4. The preform of claim 1, wherein each fiber layer of the plurality of fiber layers comprises a respective plurality of double-sided fabric segments, wherein each double-sided fabric segment comprises a respective plurality of the mesh fibers and a respective plurality of the tow fibers.

5. The preform of claim 1, wherein the ratio of said network fibers to tow fibers in said third fiber layer is from about 1:100 to about 1:2, and the ratio of said network fibers to tow fibers in said first fiber layer is from about 1:5 to about 1: 1.

6. The preform of claim 1, wherein the pre-needling thickness of the third fibrous layer is from about 0.5mm to about 2mm, and the pre-needling thickness of the first fibrous layer is from about 1mm to about 4 mm.

7. The preform of claim 1, wherein the areal weight of the third fiber layer is about 1500 grams per square meter (g/m)²) To about 3000g/m²And the area weight of the first fiber layer is about 1000g @m²To about 2000g/m²。

8. A method comprising stacking and needle punching together a plurality of fiber layers to form a preform of a carbon-carbon composite, wherein each fiber layer of the plurality of fiber layers comprises:

a network fiber, wherein the network fiber comprises at least one of a carbon fiber or a carbon-precursor fiber; and

a tow fiber, wherein the tow fiber comprises at least one of a carbon fiber or a carbon-precursor fiber;

wherein the plurality of fibrous layers comprises:

a first fibrous layer;

a second fibrous layer; and

a third fiber layer positioned between the first fiber layer and the second fiber layer, wherein the third fiber layer comprises at least one of:

a ratio of mesh fibers to tow fibers that is less than the ratio of mesh fibers to tow fibers of the first fibrous layer;

an area weight greater than an area weight of the first fibrous layer; or

A pre-needling thickness greater than the pre-needling thickness of the first fibrous layer.

9. The method of claim 8, wherein each of the plurality of fiber layers comprises a respective plurality of double-sided fabric sections, wherein each double-sided fabric section comprises a respective plurality of the mesh fibers and a respective plurality of the tow fibers, and wherein needling the plurality of fiber layers together comprises stacking a plurality of double-sided fabric sections to form a spiral, wherein each of the plurality of fiber layers completes about 0.9 to about 1.2 revolutions of the spiral.

10. A carbon-carbon composite, the carbon-carbon composite comprising:

a carbon matrix material; and

a plurality of fibrous layers stacked and needled together, each fibrous layer of the plurality of fibrous layers comprising:

a network fiber, wherein the network fiber comprises a carbon fiber; and

a tow fiber, wherein the tow fiber comprises carbon fiber;

wherein the plurality of fibrous layers comprises:

a first fibrous layer;

a second fibrous layer; and

a third fiber layer positioned between the first fiber layer and the second fiber layer, wherein the third fiber layer comprises at least one of:

a ratio of mesh fibers to tow fibers that is less than the ratio of mesh fibers to tow fibers of the first fibrous layer;

an area weight greater than an area weight of the first fibrous layer; or

A pre-needling thickness greater than the pre-needling thickness of the first fibrous layer.

Technical Field

The present disclosure relates to the manufacture of carbon-carbon composites, such as aircraft brake discs made from carbon-carbon composites.

Background

Carbon-carbon composites are composites comprising a matrix comprising carbon reinforced with carbon fibers. Carbon-carbon (C-C) composite components are useful in many high temperature applications. For example, the aerospace industry employs C-C composite components as friction materials, such as brake friction materials, for commercial and military aircraft.

Some carbon-carbon composites, such as some carbon-carbon composite brake discs for the aerospace industry, may be fabricated from a porous preform comprising a layer of carbon fiber, which may be densified using one or more of several processes including chemical vapor deposition/chemical vapor infiltration (CVD/CVI), vacuum/pressure infiltration (VPI), or Resin Transfer Molding (RTM) to infiltrate the porous preform with carbon. Some preforms may be subjected to a needling process prior to the densification process.

Disclosure of Invention

In some examples, the present disclosure describes a preform for a carbon-carbon composite, the preform comprising a plurality of fiber layers stacked and needled together, each fiber layer of the plurality of fiber layers comprising a mesh fiber and a tow fiber, wherein the tow fiber and the mesh fiber comprise a carbon fiber or a carbon-precursor fiber. The plurality of fibrous layers includes a first fibrous layer, a second fibrous layer, and a third fibrous layer positioned between the first fibrous layer and the second fibrous layer, wherein the third fibrous layer includes at least one of: a ratio of mesh fibers to tow fibers that is less than the ratio of mesh fibers to tow fibers of the first fiber layer; an area weight greater than an area weight of the first fibrous layer; or a pre-needling thickness greater than the pre-needling thickness of the first fibrous layer.

In some examples, the present disclosure describes a method comprising stacking and needle punching a plurality of fiber layers together to form a preform of a carbon-carbon composite, wherein each fiber layer of the plurality of fiber layers comprises a mesh fiber and a tow fiber, wherein the tow fiber and the mesh fiber comprise a carbon fiber or a carbon-precursor fiber. The plurality of fibrous layers includes a first fibrous layer, a second fibrous layer, and a third fibrous layer positioned between the first fibrous layer and the second fibrous layer, wherein the third fibrous layer includes at least one of: a ratio of mesh fibers to tow fibers that is less than the ratio of mesh fibers to tow fibers of the first fiber layer; an area weight greater than an area weight of the first fibrous layer; or a pre-needling thickness greater than the pre-needling thickness of the first fibrous layer.

In some examples, the present disclosure describes a carbon-carbon composite comprising a carbon matrix material and a plurality of fiber layers stacked and needled together. Each of the plurality of fiber layers includes a tow fiber and a mesh fiber, wherein the tow fiber and the mesh fiber include a carbon fiber. The plurality of fibrous layers includes a first fibrous layer, a second fibrous layer, and a third fibrous layer positioned between the first fibrous layer and the second fibrous layer, wherein the third fibrous layer includes at least one of: a ratio of mesh fibers to tow fibers that is less than the ratio of mesh fibers to tow fibers of the first fiber layer; an area weight greater than an area weight of the first fibrous layer; or a pre-needling thickness greater than the pre-needling thickness of the first fibrous layer.

The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.

Drawings

FIG. 1 is a conceptual diagram illustrating an example wheel and brake assembly that may include one or more C-C composite disc brakes formed in accordance with the techniques of this disclosure.

FIG. 2 is a schematic perspective view of an example fiber preform that may be used to make densified C-C composite materials (such as the rotor and stator brake disks of FIG. 1).

FIG. 3 is a schematic view of an exemplary double-sided fabric that may be used to form at least a portion of the respective fiber layers of the fiber preform of FIG. 2.

FIG. 4 is a perspective view of an example C-C composite material in the shape of a disc brake that may be produced from the fiber preform of FIG. 2.

FIG. 5 is a flow diagram illustrating an exemplary technique for manufacturing the fiber preform and C-C composite of FIGS. 2 and 4, respectively.

Detailed Description

The present disclosure describes techniques for making carbon fiber preforms. Such preforms may be used to make densified carbon-carbon (C-C) composites, such as C-C composite disc brakes, for example, for aircraft or other vehicles. The preform may comprise a plurality of fibre plies (e.g. fibre plies stacked on top of each other) which are stacked and needled together to form a fibre preform in the shape of a ring. Each fibrous layer may be formed using a combination of reticulated and tow carbon fibers or carbon-precursor fibers. The fiber structure of the respective fiber layers may be selected according to the location at which the respective fiber layers are positioned within the stacked stack of fiber layers (relative to the central axis of the stack) to help customize the physical and mechanical properties of the resulting C-C composite formed from the fiber preform. In some examples, the fiber structure of the fiber layers may be adjusted by, for example, changing the ratio of mesh fibers to tow fibers within the respective layers, changing the areal weight (e.g., weight of fibers per unit area) within the respective layers, changing the relative thickness of the respective layers, or a combination thereof.

FIG. 1 is a conceptual diagram illustrating an example wheel and brake assembly 10 that may include one or more C-C composite disc brakes formed in accordance with the techniques of this disclosure. For ease of description, examples of the present disclosure will be described primarily with respect to aircraft brake assemblies formed from C-C composite materials. However, the techniques of this disclosure may be used to form C-C composite components other than aircraft brake discs. For example, C-C composite components may be used as friction materials in other types of braking applications and vehicles.

In the example of fig. 1, the wheel and brake assembly 10 includes a wheel 12, an actuator assembly 14, a brake stack 58, and an axle 18. The wheel 12 includes a hub 20, a wheel leg flange 22, flange seals 24A and 24B, lug bolts 26, and lug nuts 28. The actuator assembly 14 includes an actuator housing 30, an actuator housing bolt 32, and a plunger 34. The brake stack 58 includes alternating rotor brake disks 36 and stator brake disks 38; the rotor disk 36 is configured to move relative to the stator disk 38. The rotor brake disk 36 is mounted to the wheel 12, and in particular the hub 20, by a beam key 40. The stator brake disk 38 is mounted to the shaft 18, and in particular the torque tube 42, by a rack 44. The wheel and brake assembly 10 may support any type of private, commercial or military aircraft or other type of vehicle.

The wheel and brake assembly 10 includes a wheel 12, and in the example of fig. 1, the wheel 12 is defined by a hub 20 and a wheel leg flange 22. The wheel leg flange 22 may be mechanically secured to the hub 20 by a lug bolt 26 and a lug nut 28. The wheel 12 defines flange seals 24A and 24B. During assembly, an inflatable tire (not shown) may be placed over the hub 20 and secured on the opposite side by the wheel leg flanges 22. Thereafter, the lug nuts 28 may be tightened on the lug bolts 26, and the inflatable tire may be inflated with the flange seals 24A and 24B to provide an airtight seal for the inflatable tire.

The wheel and brake assembly 10 may be mounted to the vehicle via the torque tube 42 and the axle 18. In the example of fig. 1, the torque tube 42 is secured to the shaft 18 by a plurality of bolts 46. The torque tube 42 supports the actuator assembly 14 and the stator brake disk 38. Axle 18 may be mounted to a strut of a landing gear (not shown) or other suitable component of the vehicle to connect wheel and brake assembly 10 to the vehicle.

Braking may need to be applied from time to time during vehicle operation, such as during landing and taxiing procedures of an aircraft. The wheel and brake assembly 10 is configured to provide a braking function to the vehicle via the actuator assembly 14 and the brake stack 58. The actuator assembly 14 includes an actuator housing 30 and a plunger 34. The actuator assembly 14 may include different types of actuators, such as, for example, one or more of electro-mechanical actuators, hydraulic actuators, pneumatic actuators, and the like. During operation, the plunger 34 may extend away from the actuator housing 30 to axially compress the brake stack 58 against the compression point 48 for braking.

The brake stack 58 includes alternating rotor brake discs 36 and stator brake discs 38. Rotor brake discs 36 are mounted on the hub 20 for common rotation by beam keys 40. The stator brake disk 38 is mounted to the torque tube 42 by a rack 44. In the example of fig. 1, the brake stack 58 includes four rotors and five stators. However, in other examples, a different number of rotors and/or stators may be included in the brake stack 58.

The rotor brake disk 36 and the stator brake disk 38 may provide opposing friction surfaces for braking the aircraft. As the kinetic energy of the moving aircraft is converted to thermal energy in the brake stack 58, the temperature in the brake stack 58 may increase rapidly. As such, the rotor brake disks 36 and the stator brake disks 38 forming the brake stack 58 may comprise a strong, thermally stable material capable of operating at very high temperatures.

In one example, the rotor brake disks 36 and/or the stator brake disks 38 form a C-C composite material in the form of a ring that defines a set of opposing wear surfaces. The C-C composite may be manufactured using any suitable manufacturing technique or combination of techniques, including, for example, infiltrating the fiber preform described herein as a starting substrate with a carbon matrix material using Vacuum Pressure Infiltration (VPI), Resin Transfer Molding (RTM), Chemical Vapor Infiltration (CVI), Chemical Vapor Deposition (CVD), additive manufacturing, and the like.

As briefly mentioned, in some examples, the rotor disk 36 and the stator disk 38 may be mounted in the wheel and brake assembly 10 via a beam key 40 and a rack 44, respectively. In some examples, the beam keys 40 may be spaced circumferentially around an interior portion of the hub 20. For example, the beam key 40 may be shaped to have opposing ends (e.g., opposing sides of a rectangle) and may have one end mechanically secured to an inner portion of the hub 20 and an opposing end mechanically secured to an outer portion of the hub 20. The beam key 40 may be integrally formed with the hub 20 or may be separate from the hub 20 and mechanically secured to the hub 20, for example, to provide a thermal barrier between the rotor brake disk 36 and the hub 20. To this end, in various examples, the wheel and brake assembly 10 may include a heat shield (not shown) that extends radially outward and around the brake stack 58, for example, to limit heat transfer between the brake stack 58 and the wheel 12.

In some examples, the racks 44 may be spaced circumferentially around an outer portion of the torque tube 42. As such, the stator brake disk 38 may include a plurality of radially inwardly disposed lug slots along an inner diameter of the brake disk that are configured to engage the rack 44. Similarly, the rotor brake disk 36 may include a plurality of radially inwardly disposed lug grooves along the outer diameter of the brake disk that are configured to engage the beam keys 40. As such, the rotor brake disks 36 will rotate with the movement of the wheel, while the stator brake disks 38 remain stationary, allowing the friction surfaces of adjacent stator brake disks 38 and rotor brake disks 36 to engage each other, thereby slowing the rotation of the wheel 12.

FIG. 2 is a schematic perspective view of an example fiber preform 50 that may be used to make densified C-C composite materials, such as rotor brake disks 36 and stator brake disks 38. Fiber preform 50 includes a plurality of fiber layers 52 including a first outer layer 52A, a second outer layer 52B, and at least one inner layer 52C. Each fiber layer 52 may include one or more fabric segments 56 made from carbon fibers or carbon-precursor fibers, in the form of both mesh and tow fibers. The plurality of layers 52 may be stacked (e.g., on top of each other) in the direction of the central axis 54 to form a stack 58.

Fiber preform 50 also includes a plurality of needled fibers 60 that extend at least partially through two or more fiber layers 52. In some examples, the needled fibers 60 may extend substantially vertically (e.g., vertically or nearly vertically in the z-axis direction) through the stack 58 (e.g., substantially parallel to the central axis 54). Although the figures illustrate the needled fibers 60 as being generally parallel to the central axis 54, in some examples, at least some of the needled fibers 60 may not be parallel to the central axis 54 and may take on other orientations in the stack 58, including, for example, undulating, angled, curved, and the like.

As discussed further below, the needled fibers 60 are introduced during the needling process. In some examples, the needled fibers 60 may be provided by a plurality of fiber layers 52. For example, the needling process may drive the network fibers present within the respective fibrous layers 52 into adjacent fibrous layers 52 to mechanically entangle and bond the fibrous layers 52 together. Additionally or alternatively, as fiber layers 52 are stacked and needled together, at least some of the tow fibers within respective fiber layers 52 may be converted into needled fibers 60 within fiber preform 50. For example, the needling process may break some of the tow fibers contained in the respective fiber layers 52 and at least partially transfer the broken fibers into one or more adjacent fiber layers 52 within the fiber preform 50 to form needled fibers 60.

In some examples, fiber preform 50 may be in the shape of a ring or disk that defines an outer preform diameter (OD). Fiber preform 50 may also include a central bore 62 extending through stack 58 along central axis 54. The central bore 62 may define an inner preform diameter (ID) of the fiber preform 50. In some examples, the outer preform diameter (OD) of fibrous preform 50 may be about 14.5 inches (e.g., about 37cm) to about 25 inches (e.g., about 64 cm). The inner preform diameter (ID) of the fiber preform 50 may be about 4.5 inches (e.g., about 12cm) to about 15 inches (e.g., about 38 cm). In other examples, fiber preform 50 may be partially disk-shaped (e.g., crescent-shaped) or include a different geometry.

As described further below, each fiber layer 52 within fiber preform 50 may include a combination of tow fibers and mesh fibers. Both the tow fibers and the mesh fibers may include carbon fibers, fibers configured to be subsequently pyrolyzed into carbon fibers (hereinafter "carbon-precursor fibers"), or combinations thereof. Carbon-precursor fibers may include, for example, Polyacrylonitrile (PAN) fibers, oxidized polyacrylonitrile (O-PAN) fibers, rayon fibers, and the like. Tow fibers (also sometimes referred to as chordal fibers) may represent relatively long or substantially continuous fibers that are bundled together from a respective tow. In some examples, each respective tow may include hundreds to thousands of individual fibers that have been unidirectionally aligned and bundled together to form the tow. Each fiber layer 52 may include a plurality of tows, each tow including a plurality of tow fibers. In some examples, the tows may be unidirectionally aligned within respective fabric segments that may be used to form all or a portion of the respective fiber layers 52 such that the tow fibers within the fabric segments are all substantially aligned (e.g., aligned or nearly aligned). The network fibers may include chopped, discontinuous, or predominantly carbon fibers or carbon-precursor fibers having a non-specified alignment, which are relatively short compared to the tow fibers. In some examples, the mesh fibers may define substantially random fiber orientations relative to each other and relative to the tow fibers.

In some examples, tow fibers and mesh fibers may be bonded together to form a single layer of material, referred to as a double layer of double-sided fabric, prior to bonding to the respective fiber layers 52 of the fiber preform 50. FIG. 3 is a schematic illustration of an example double-sided fabric 80 that may be used to form at least a portion of a respective fibrous layer 52. The double-sided fabric 80 includes a plurality of unidirectionally aligned tow fibers 82, shown aligned along the x-axis of fig. 3, that have been combined with mesh fibers (not shown).

In some examples, the formation of the double-sided fabric 80 may be accomplished by combining one or more layers of aligned tow fibers 82 with one or more layers of mesh fibers that are subsequently needle-punched into the tow fiber layers 82 to form the double-sided fabric 80. For example, a layer of reticulated fibers may be formed by cross-carding a web to achieve a desired areal weight and then needling the layer to form a reticulated layer. Additionally or alternatively, the mesh layer may be formed by air-laying mesh fibers on top of the layer of aligned tow fibers 82. The aligned tow fiber layer 82 may be formed by spreading large continuous tows using a creel to form a sheet of desired areal weight, with the tow fibers 82 aligned unidirectionally in the same direction. Both the mesh layer and the tow fiber layer 82 may be needled together to force relatively short mesh fibers to entangle with the tow fibers 82 to form the double-sided fabric 80. The entangled network fibers may help mechanically bind the tow fibers 82 together, allowing the double-sided fabric 80 to be effectively treated without the tow fibers 82 in the fabric layer separating or separating during subsequent processing. The resulting double-sided fabric 80 may be more durable, better retain its shape, and generally easier to further manufacture than either only tow fiber layer 82 or only mesh fiber layer. Other techniques may also be used to form the double-sided fabric 80, including both tow fibers 82 and mesh fibers, which may be known to those skilled in the art.

In some examples, in addition to holding the respective double-sided fabric 80 together, the mesh fibers used to make the double-sided fabric 80 may ultimately be used to form or contribute to a portion of the needled fibers 60 in the fiber preform 50, as the fiber layers 52 are stacked and needled together. Both the mesh fibers and tow fibers 82 may be formed from the same carbon fiber or carbon fiber precursor material, may be formed from different carbon fiber or carbon fiber precursor materials, or may be formed from different combinations of carbon fiber and/or carbon fiber precursor materials.

In some examples, each fiber layer 52 may be formed using one or more fabric sections 56, each fabric section 56 cut from a respective double-sided fabric 80. In examples where each fiber layer 52 is formed from a single fabric segment 56, the respective fabric segment 56 may be cut from the double-sided fabric 80 in the shape of a loop and assumed on the other fiber layers 52.

In some examples, each fiber layer (e.g., fiber layer 52B) may include a plurality of fabric segments 56 that collectively comprise the respective fiber layer 52B. For example, the fiber preform 50 may be formed by sequentially adding adjacent fabric segments 56 in a continuous spiral about the central axis 54. In such examples, each fiber layer 52 may define a portion of a helix about the number or turns of the central axis 54. In some examples, each fiber layer 52 may define about 0.9 to about 1.2 turns of the helix (e.g., about 325 ° to about 420 °). In examples where the respective fiber layers 52 define more than one full turn of the helix, a portion of the respective fiber layers 52 may overlap with themselves. Despite the overlap, the respective fiber layers 52 may still be characterized as a single fiber layer 52 within fiber preform 50.

In examples where each fiber layer 52 includes a plurality of fabric segments 56, each fabric segment 56 may define an arcuate shape characterized by an arcuate angle

And its fiber orientation angle (α), which is shown in fig. 3, fiber orientation angle (α) represents the angle between the segment bisector 84 of the respective fabric segment 56 (e.g., the line representing the center or bisector of the arcuate shape of the fabric segment 56) and the direction in which the tow fibers 82 are aligned) Or some intermediate angle.

Arc angle

Indicating the angle between the abutting edges 86 of the respective fabric segments 56 and the degree of rotation that the respective fabric segments 56 will occupy within the respective fiber layers 52. For example, an arc angle equal to 45 °

1/8 showing a full rotation about the central axis 54. In some examples, the fabric segments 56 described herein may define an arc angleSuch that fabric section 56 forming a single fiber layer 52A of fiber preform 50 completes one full revolution. For example, if a total of six arcuate fabric segments 56 are used to define one complete fiber layer 52A, each fabric segment 56 may define an arcuate angle of 60

Such that six fabric segments 56 are aligned (e.g., define an arc angle) with the abutting edge 86 in contact with the abutting edge of an adjacent fabric segment 56

Edge of) will complete one full revolution, with each fabric segment occupying 1/6 of the corresponding fiber layer 56A.

In some examples, fabric segments 56 described herein may define arc angles that add up to 360 ° (i.e., add up to one complete revolution) within respective fiber layers 52A

For example, the fabric segments 56 may be sized such that the plurality of fabric segments 56 within a respective fiber layer 52A complete more or less than one full rotation within the layer. In some examples, each fabric segment 56 may define an arc angle of about 65 ° to about 70 ° (e.g., about 68 °)

However, other arc angles may be used if desiredEach defining an arc angle of about 65 deg. to about 70 deg. at the respective fabric section 56

In some examples, the respective fiber layer 52A may make about 1.08 to about 1.17 turns in a spiral arrangement with a small portion of the layer overlapping itself. Angle of arc

Setting at about 65 ° to about 70 ° (e.g., about 68 °) may help minimize butt joint overlap of abutting edges 86 between adjacent fiber layers 52 within the final constructed fiber preform 50. Additionally or alternatively, for the fabric section 56, the arc angle is rounded

Setting at about 65 to about 70 (e.g., about 68) may facilitate creation of an arc angle within fiber preform 50 as compared to a larger arc angle

More uniform alignment of the tow fibers 82.

While some of the figures described herein show a relatively small number of layers used in the respective fiber preforms, preforms (e.g., fiber preform 50) produced as a result of the techniques described herein may include any suitable number of fiber layers 52 (e.g., 30 or more layers) to produce the desired thickness (T) of the resulting preform.

In the field of C-C composite disc brakes, important performance characteristics of the disc brakes (e.g., rotor disc brake 36 and stator disc brake 38) may include, for example, the ability of the disc brake to transfer heat generated at friction surfaces away from such surfaces, the thermal capacity of the disc brake (e.g., the ability of the disc brake to absorb heat or to accommodate elevated temperatures during braking), the compression, bending, and shear strengths of the disc brake, and the like. In some examples, the selective performance of the resulting C — C composite disc brake may be increased by altering the underlying fiber structure of the fiber preform 50. For example, to improve heat transfer along central axis 54, the number of needled fibers 60 or "z-axis" fibers within fiber preform 50 may be increased. To improve the general heat capacity of the disc brake, the amount of carbon matrix material (e.g., densified carbon material) that penetrates within fiber preform 50 may be increased. Carbon matrix materials (e.g., carbon deposited via CVI/CVD) are denser than carbon materials of carbon fibers and therefore have a better ability to absorb heat generated during fracture than carbon fibers.

In some examples, the fiber structures required to improve such desired performance of C-C composite disc brakes often conflict with one another. For example, to improve heat transfer along central axis 54, fiber preform 60 may be more needled to increase the number of needled fibers 60 or z-axis fibers introduced into the preform. However, the amount or duration of needling performed on fibrous preform 60 may compress the respective fibrous layers 52, leaving less space between the fibers to contain carbon matrix material, thereby reducing the amount of carbon matrix material that may be added to fibrous preform 50 and reducing the heat capacity properties of the resulting C-C composite.

In some examples, fiber layers 52 of fiber preform 50 may be individually tailored to improve one or more performance characteristics of the final C — C composite. In some examples, for reasons described further below, the fiber layers 52 may be individually customized to vary the performance characteristics of each fiber layer 52 according to the position of the respective fiber layer 52 within the stack 58 by adjusting the ratio of network fibers to tow fiber bundles 82 within the respective fiber layer 52, the thickness of the respective fiber layer 52, the areal weight of the respective fiber layer 52, or a combination thereof.

In some examples, fiber layer 52 may be customized by increasing the ratio of mesh fibers to tow fibers 82 within fiber layer 52 to be closer to the exterior of fiber preform 52 (e.g., exterior layers 52A and 52B) than to the interior layer (e.g., interior layer 52C). Increasing the ratio of network fibers within the respective fiber layers 52 increases the number of fibers available that can be converted into needle punched fibers 60 or otherwise arranged into z-axis fibers within fiber preform 50. In some examples, having a higher ratio of mesh fibers near the outer layers 52A and 52B may be used to increase the number of needle punched fibers 60 or z-axis fibers present along the friction surface of the resulting C-C composite disc brake to help transfer heat away from the friction surface of the resulting C-C composite disc brake into an interior region of the disc brake (e.g., toward the inner layer 52C). Additionally or alternatively, increasing the number of needled fibers 60 or z-axis fibers present along the friction surface of fiber preform 50 may increase the shear strength of outer layers 52A and 52B, where such shear forces would be highest during the braking process.

In addition, the degree of compression within the interior layer 52C that occurs through the needling process and the introduction of the needled fibers 60 or z-axis fibers may be reduced by the presence of a lower ratio of reticulated fibers in the interior layer 52C. The relatively reduced compression within interior layer 52C may allow for more pore structures and allow for greater accumulation of carbonaceous material, which is added during subsequent densification cycles. The presence of the increased carbon matrix material may in turn increase the overall thermal capacity of the resulting C-C composite disc brake.

Additionally or alternatively, increasing the ratio of tow fibers 48 present within the inner layer 52C may allow for better radial heat transfer within the C-C composite toward the inner or outer diameter, where the absorbed heat may be dissipated into surrounding components of the wheel and brake assembly 10. The tow fibers 48 present within the respective layers 52 may also impart better flexural strength or resistance (e.g., bending in the x-y plane) to the resulting C-C composite, with inner layers 52C being more critical than outer layers 52A and 52B.

In some examples, each fiber layer 52 may define a ratio of mesh fibers to tow fibers 82 of about 1:100 to about 1: 1. In some examples, one or more of the inner layers 52C may define a ratio of mesh fibers to tow fibers 82 of about 1:100 to about 1:2 (e.g., about 1:100 to about 1:5), and the outer layers 52A and 52B may define a ratio of mesh fibers to tow fibers 82 of about 1:5 to about 1:1 (e.g., 1:4 to about 1: 1).

Additionally or alternatively, fiber layers 52 may be customized by reducing the relative thickness (e.g., the thickness in the direction of central axis 54) within outer layers 52A and 52B of fiber preform 50 as compared to central or inner layer 52C. Reducing the thickness within the respective fibrous layers 52 may increase the amount of overall needling that occurs within the respective fibrous layers 52. For example, in a conventional needling process, a needle board or loom may include a plurality of needles that include barbs that engage the web fibers during the needling process and drive the fibers into the adjacent fibrous layers 52. The needling process may be performed with each application of a new fiber layer 52 or a set number or number fraction of fiber layers 52. In some examples, a needle board or loom may define a penetration depth that remains relatively constant throughout the needling process. In such examples, the total number of layers penetrated by the needle board or loom may depend on the relative thickness of the respective fiber layers 52. If the respective fibrous layer or group of layers defines a relatively low thickness, the total number of layers required to define the total thickness (T) will be relatively high and additional needle punching may need to occur to bond the layers together. In addition, since the penetration depth of the needles will pass through more fiber layers 52 in a given needle stroke, more needling will occur in the corresponding fiber layers 52. Conversely, if the fiber layers are relatively thick, less overall needling may occur and the number of layers penetrated per needle stroke will be reduced. The relative increase or decrease in the occurrence of needling within a respective fibrous layer 52 may correspond to an increase or decrease, respectively, in the presence of needle fibers 60 or z-axis fibers within the respective layer.

In some examples, by forming fiber preform 50 to include relatively thick fiber layers 52 toward the center of the preform (e.g., inner layer 52C) and relatively thin fiber layers 52 toward the outside of the preform (e.g., outer fiber layers 52A and 52B and/or inner layers near outer fiber layers 52A and 52B), more needling may occur in the thinner outer layers than in the thicker inner layers, thereby increasing the comparative number of needled fibers 60 or z-axis fibers generated within outer fiber layers 52 of fiber preform 50. The addition of the presence of needled fibers 60 or z-axis fibers within the outer layers (e.g., outer layers 52A and 52B) of fiber preform 50 may impart one or more of the performance characteristics described above to the resulting C-C composite.

In some examples, each fiber layer 52 may have a pre-needling or fabric thickness (e.g., before being needled as a layer of fiber preform 50) of about 1 millimeter (mm) to about 4 millimeters as measured in a direction parallel (e.g., parallel or nearly parallel) to central axis 54. In some examples, one or more of the interior layers 52C may define a pre-needled or fabric thickness of about 0.5mm to about 2mm (e.g., about 1mm to about 2mm), and the exterior layers 52A and 52B may define a pre-needled or fabric thickness of about 1mm to about 4mm (e.g., about 2mm to about 4 mm). The total thickness (T) of the fiber preform 50 at completion may be about 1 inch to about 3 inches (e.g., about 2.5 centimeters (cm) to about 7.6cm), which may be further reduced during subsequent carbonization/pyrolysis.

Additionally or alternatively, the fiber layers 52 may be customized by reducing the areal weight (e.g., fiber weight per unit area) of the fibers (e.g., tow fibers 82 and mesh fibers) within the outer layers 52A and 52B of the fiber preform 50 as compared to the central or inner layer 52C. Using high areal weight fabric sections 56 to increase the areal weight of the fibrous layers 52 may require less needling to join the respective fibrous layers 52. By reducing the areal weight of fiber layers 52 toward the exterior of fiber preform 50 (e.g., outer fiber layers 52A and 52B and/or inner layers closer to outer fiber layers 52A and 52B) as compared to fiber layers 52 near the center of fiber preform 50 (e.g., inner layer 52C), more needling may occur within lower areal weight fiber layers 52 near the exterior, thereby increasing the comparative number of needled fibers 60 or z-axis fibers generated within the respective fiber layers 52 and/or reducing the compression occurring within inner layer 52C. The addition of the presence of needled fibers 60 or z-axis fibers within the outer layers (e.g., outer layers 52A and 52B) of fiber preform 50 may impart one or more of the performance characteristics described above to the resulting C-C composite.

In some examples, the double-sided fabric 80 for the fabric section 56 and the fiber layer 52 may have about 1250 grams per square meter to about 3000 grams per square meter (g/m)²) Area weight of (c). In some examples, one or more of interior layers 52C may be formed from a fabric length defining about 1500g/m²To about 3000g/m²And outer layers 52A and 52B may be defined by a weight of about 1000g/m²To about 2000g/m²(e.g., about 1250g/m²To about 2000g/m²) The areal weight of fabric section.

Once the fiber preform 50 has been fully formed to the desired thickness (T), the preform may be subjected to one or more pyrolysis and densification cycles. For example, the fiber preform 50 may be initially pyrolyzed (e.g., carbonized) to convert any carbon-precursor material into carbon. After pyrolysis, the network fibers and tow fibers 82 become carbon fibers, if not carbon fibers. The fibrous preform 50 may then be subjected to one or more densification cycles, such as chemical vapor deposition/chemical vapor infiltration (CVD/CVI), vacuum/pressure infiltration (VPI), or Resin Transfer Molding (RTM), followed by a pyrolysis or heat treatment cycle to infiltrate the fibrous preform 50 with a carbon matrix material to produce a C — C composite.

Fig. 4 is a perspective view of an example C-C composite 90 in the shape of a disc brake (e.g., stator disc brake 38). The C-C composite 90 may include a fiber preform 50, post-pyrolyzed (if necessary) to substantially convert the network fibers and tow fibers 82 into carbon fibers, and then densified and any optional heat treatment to incorporate the carbonaceous material into the pores within the fiber preform 50. The C-C composite 90 may include a plurality of fiber layers (e.g., fiber layers 52) having a fiber structure similar to fiber preform 50 described above. In some examples, the number of z-axis fibers (e.g., needle punched fibers 60) of the outer fiber layer 92 (e.g., first outer layer 52A or second outer layer 52B) of the C-C composite 90 may be greater than the number of z-axis fibers in the central layer (e.g., inner layer 52C) of the C-C composite 90. Additionally or alternatively, the amount of carbon matrix material in the outer fibrous layers 92 of the C-C composite 90 may be less than the amount of carbon matrix material in the central layer.

The fiber preforms and C-C composites described herein may be formed using any suitable technique.

FIG. 5 is a flow chart illustrating an exemplary technique for fabricating fiber preform 50 and C-C composite 90. For ease of illustration, the exemplary method of FIG. 5 is described primarily with respect to fiber preform 50 of FIG. 2; however, other fiber preforms may be formed using the described techniques, and other techniques may be used to fabricate fiber preform 50 or C-C composite 90.

The example technique of fig. 5 includes stacking and needle punching a plurality of fiber layers 52 together to form a fiber preform 50 (100); pyrolyzed fiber preform 50 (102); and densifying the resulting preform 50 to form the C-C composite 90 (104).

As described above, each fiber layer 52 may include a respective plurality of mesh and tow fibers 82 that define a respective mesh-to-tow fiber ratio, an area weight, and a respective pre-needling thickness of the fiber layer 52. in some examples, each fiber layer 52 may be constructed using a respective plurality of double-sided fabric segments 56. for example, the double-sided fabric segments 56 may be aligned and stacked in a spiral arrangement. in such examples, each fiber layer 52 may complete about 0.9 to about 1.2 revolutions of the spiral, with the fiber layers 52 stacked (e.g., stacked) on one another relative to the central axis 54 to form a stack 58. each fabric segment 56 may each define an arc angle (α) fiber orientation angle as described above

And may be selected or modified to achieve a desired ratio of mesh to tow fibers, areal weight, and/or pre-needling/fabric thickness for the respective fibrous layers 52.

Each fabric section 56 may be needled after being added to fiber preform 50. In some examples, the respective fabric segments 56 may be needled into the preform 50 on a layer-by-layer basis. Additionally or alternatively, more than one fiber layer 52 may be added to preform 50, and then the co-stacked layers 52 may be simultaneously needled to incorporate the layers into fiber preform 50. The entire process may then be continued until the desired preform thickness (T) is obtained.

Once the fiber preform 50 is formed, the fiber preform 50 may be pyrolyzed (102) to convert any carbon-precursor material into carbon by a thermal degradation process to effectively burn off any non-carbon material. For example, the fiber preform 50 may be carbonized by heating the fiber preform 50 in a retort under inert or reducing conditions to remove non-carbon components (hydrogen, nitrogen, oxygen, etc.) from the fiber. Carbonization may be performed using a retort, such as an autoclave, furnace, hot isostatic press, uniaxial hot press, or the like. In each of these techniques, the fiber preform 50 may be heated at a temperature in the range of about 600 ℃ to about 1000 ℃ in an inert atmosphere, while optionally being mechanically compressed. Mechanical compression may be used to define the geometry (e.g., thickness (T)) of fiber preform 50. In some examples, the distiller may be lightly purged with nitrogen for about 1 hour, then slowly heated to about 900 ℃ over the course of about 10 to 20 hours, and then the temperature is raised to about 1050 ℃ over about 1 to 2 hours. The still may then be held at about 1050 ℃ for about 3 to 6 hours, and the carbonized preform then allowed to cool overnight. In some examples, the carbonizing step may be performed at even higher temperatures, including up to about 1800 ℃.

After carbonization, the fiber preform 50 may be subjected to one or more densification cycles to form the C — C composite 90 (104). Example densification cycles may include one or more cycles of CVI/CVD, for example, by application of a carbonaceous gas. Any suitable carbonaceous gas may be used during CVI/CVD processing, including, for example, carbon-based gases such as natural gas, methane, ethane, propane, butane, propylene, or acetylene, or a combination of at least two of these gases. In some examples, the application of the carbonaceous gas via CVI/CVD to densify the fiber preform 50 may occur substantially in a vacuum space (e.g., a vessel having an internal environment of less than 100 torr) or under an inert gas environment in order to control the chemical deposition reaction to produce the carbon matrix material. In some examples, the environment including the fiber preform 50 may be heated to an elevated temperature, such as about 900 ℃ to about 1200 ℃, during application of the CVI/CVD gas to facilitate the chemical deposition reaction.

In other examples, the fiber preform 50 may be densified (104) using other suitable techniques, including resin infiltration and carbonization, e.g., via Resin Transfer Mold (RTM) processing, Vacuum Pressure Infiltration (VPI) processing, High Pressure Infiltration (HPI), and the like. In some examples, the densifying step (104) may produce a densified C-C composite 90 having a final density of about 1.65g/cc to about 1.95 g/cc.

In some examples, the major friction surfaces of the resulting C — C composite may be sculpted into a desired shape, such as a final brake disc shape, during or after densification of the fiber preform 50. For example, the C-C composite 90 may be ground in the shape of a densified C-C composite disc brake having a final thickness T (e.g., about 1.4 inches). Additionally or alternatively, the lug grooves 94 may be formed along either the inner or outer diameter at this time.

Various examples have been described. These examples and other examples are within the scope of the following claims.