Patent Application
20250146550
The present disclosure relates to preforms for composite articles, for example, composite articles used in brake friction articles.
Carbon fiber-reinforced carbon materials, also referred to as carbon-carbon composite materials, are composite materials that include carbon fibers reinforced in a matrix of carbon material. Carbon-carbon composite components can be used in many high temperature applications. For example, the aerospace industry employs carbon-carbon composite components as friction materials for commercial and military aircraft, such as brake friction materials.
In general, the disclosure describes a composite preform that includes a plurality of layers including reinforcing fibers, and systems and techniques for forming composite preforms.
In some examples, the disclosure describes a preform for a composite. The composite may include a plurality of fibrous layers consolidated together and forming the preform extending along a longitudinal axis. The plurality of fibrous layers includes at least one first fibrous layer and at least one second fibrous layer. The at least one first fibrous layer includes a plurality of first segments, and the least one second fibrous layer includes a plurality of second segments. At least one first segment of the plurality of first segments includes a plurality of reinforcing fibers extending at an angle −α relative to a radial direction extending from the longitudinal axis. At least one second segment of the plurality of second segments includes a plurality of reinforcing fibers extending at an angle +α relative to the radial direction. α is greater than 0° and less than 90°.
In some examples, the disclosure describes a method including laying up a plurality of layers including at least one first fibrous layer and at least one second fibrous layer to form a preform extending along a longitudinal axis. The at least one first fibrous layer includes a plurality of first segments, and the least one second fibrous layer including a plurality of second segments. The method further includes consolidating the preform. At least one first segment of the plurality of first segments includes a plurality of reinforcing fibers extending at an angle −α relative to a radial direction extending from the longitudinal axis. At least one second segment of the plurality of second segments includes a plurality of reinforcing fibers extending at an angle +α relative to the radial direction. α is greater than 0° and less than 90°.
The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
In general, the disclosure describes a composite preform that includes a plurality of layers including reinforcing fibers, and systems and techniques for forming composite preforms.
Brakes, for example, aircraft or other vehicular brakes, may be formed from preforms including reinforcing fibers, for example, carbon fibers. For example, preforms may be densified and/or carbonized to form components of brakes to improve the friction material performance consistency.
A brake may be formed from a composite preform, and the composition and configuration of the preform affects the properties of the brake formed from the preform. One or more of the following preform parameters or configurations, or carbonization techniques may be used to promote strength and uniformity of brake structures, and increase and stabilize the brake dyno performance: controlled fiber orientations in segments, controlled segment layup sequence, a relatively high needled preform density, or free-state (unconstrained) carbonization. In certain examples, brake preforms may include a plurality of layers respectively including disk or arcuate segments including reinforcing fibers. The layers may be consolidated (for example, by needle punching, or by stitching and tufting) to promote intermeshing and reinforcement between layers. The segments may include reinforcing fibers laid or arranged in chordal orientation (reinforcing fibers extending at 90° relative to a radial axis) or in radial orientation (reinforcing fibers extending at 0° or substantially aligned with the radial axis.
Instead of being in chordal or radial orientation, the reinforcing fibers may be oriented at other orientations. In some examples, preforms according to the present disclosure may include segments including reinforcing fibers oriented at an angle greater than 0° or less than 90° relative to the radial direction, for example, at 30°, 45°, 60°, or some other angle.
In some examples, the disclosure describes a preform for a composite. The composite may include a plurality of fibrous layers consolidated together and forming the preform extending along a longitudinal axis. The plurality of fibrous layers includes at least one first fibrous layer and at least one second fibrous layer. The at least one first fibrous layer includes a plurality of first segments, and the least one second fibrous layer includes a plurality of second segments. At least one first segment of the plurality of first segments includes a plurality of reinforcing fibers extending at an angle +α relative to a radial direction extending from the longitudinal axis. At least one second segment of the plurality of second segments includes a plurality of reinforcing fibers extending at an angle −α relative to the radial direction. α is greater than 0° and less than 90°.
Orienting the reinforcing fibers at angles +α and −α (for example, having an absolute magnitude of 45°, 60°, or otherwise greater than 0° and less than) 90° may promote balance in preform structures, and distribute friction forces more evenly during braking. Further, angled reinforcing fibers may promote dissipation of heat generated during braking in a radially outward direction, resulting in relatively lower brake temperatures compared to reinforcing fibers arranged in chordal orientation.
The fibrous layers including segments differing in orientation of reinforcing fibers may be laid up in different layup sequences. For example, a 6:6 layup sequence may include an XXXXXX:YYYYYYY pattern, in which six segments having a first fiber orientation (for example, a negative angle) alternate with six segments having a second fiber orientation (for example, a positive angle).
In some examples, other layup sequences may be used, for example, a 1:1 (XY segment pattern), or a 2:2 (XXYY segment pattern), or some other layup sequence. Using a 1:1 (XY pattern) layup sequence may further promote uniformity and strength in brake structures formed from preforms. The 1:1 layup sequence may form controllable and uniform structures within the friction rubbing zones, compared to chordal segment layers and/or radial segment layers having a 6:6 layup sequence.
In some examples, preforms may be needle-punched with a relatively high needled preform density (for example, greater than 0.60 g/cc, or at least 0.65 g/cc). Such a higher needled preform density may include a larger proportion of fibers extending in a Z-direction (perpendicular to layers), promoting connectivity between layers for higher carbon brake strengths.
In certain techniques, consolidated preforms are carbonized under a constrained condition. For example, a load may be applied to a preform during carbonization. In some examples, consolidated preforms may be carbonized in an unconstrained condition, for example, in the absence of a load. Such unconstrained carbonization may promote free thermal shrinkages during high temperature (for example, over 1600° C.) carbonization under an inert environment. Such unconstrained carbonization may allow the fibers within the preforms having self-controlled or free thermal shrinkages for lower fiber volume fractions (FVF) of the resultant materials, in turn resulting in lower Beff, and may provide lower thermal stress residues in the carbonized materials, resulting in lower distortions and higher braking clearance during the braking.
Thus, one or more of reinforcing fiber orientations, layup sequence, needling density, or state of constraint during carbonization described herein may be used to arrive at brake structures that are relatively more uniform, have an increased carbon strength, and have a brake effectiveness in a target range. Further, preforms and techniques according to the present disclosure may also exhibit one or more of predetermined carbon brake dyno performance, relatively higher quality assurance test pass rates, higher carbon yields, reduced carbon scraps, increased productivity, reduced costs, and CO sustainability due to a reduced need to make up or replace out-of-specification articles.
In the example of
Wheel and brake assembly 10 includes wheel 12, which in the example of
Wheel and brake assembly 10 may be mounted to a vehicle via torque tube 42 and axle 18. In the example of
During operation of the vehicle, braking may be necessary from time to time, such as during landing and taxiing procedures of an aircraft. Wheel and brake assembly 10 is configured to provide a braking function to the vehicle via actuator assembly 14 and brake stack 16. Actuator assembly 14 includes actuator housing 30 and ram 34. Actuator assembly 14 may include different types of actuators such as one or more of, e.g., an electrical-mechanical actuator, a hydraulic actuator, a pneumatic actuator, or the like. During operation, ram 34 may extend away from actuator housing 30 to axially compress brake stack 16 against compression point 48 for braking.
Brake stack 16 includes alternating rotor brake discs 36 and stator brake discs 38. Rotor brake discs 36 are mounted to wheel hub 20 for common rotation by beam keys 40. Stator brake discs 38 are mounted to torque tube 42 by splines 44. In the example of
Rotor brake discs 36 and stator brake discs 38 may provide opposing friction surfaces for braking an aircraft. As kinetic energy of a moving aircraft is transferred into thermal energy in brake stack 16, temperatures may rapidly increase in brake stack 16. As such, rotor brake discs 36 and stator brake discs 38 that form brake stack 16 may include robust, thermally stable materials capable of operating at very high temperatures.
In one example, rotor brake discs 36 and/or stator brake discs 38 are formed as a composite (for example, a C-C composite) in the form of an annulus that defines a set of opposing wear surfaces. The composite may be fabricated using any suitable manufacturing technique or combination of techniques including, for example, vacuum pressure infiltration (VPI), resin transfer molding (RTM), chemical vapor infiltration (CVI), chemical vapor deposition (CVD), additive manufacturing, mechanical machining, ablation techniques, or the like using the fiber preforms describe herein as the starting substrate.
As briefly noted, in some examples, rotor brake discs 36 and stator brake discs 38 may be mounted in wheel and brake assembly 10 by beam keys 40 and splines 44, respectively. In some examples, beam keys 40 may be circumferentially spaced about an inner portion of wheel hub 20. Beam keys 40 may, for example, be shaped with opposing ends (e.g., opposite sides of a rectangular) and may have one end mechanically affixed to an inner portion of wheel hub 20 and an opposite end mechanically affixed to an outer portion of wheel hub 20. Beam keys 40 may be integrally formed with wheel hub 20 or may be separate from and mechanically affixed to wheel hub 20, e.g., to provide a thermal barrier between rotor brake discs 36 and wheel hub 20. Toward that end, in different examples, wheel and brake assembly 10 may include a heat shield (not shown) that extends out radially and outwardly surrounds brake stack 16, e.g., to limit thermal transfer between brake stack 16 and wheel 12.
In some examples, splines 44 may be circumferentially spaced about an outer portion of torque tube 42. As such, stator brake discs 38 may include a plurality of radially inwardly disposed lug notches along an inner diameter of the brake disc configured to engage with splines 44. Similarly, rotor brake discs 36 may include a plurality of radially inwardly disposed lug notches along an outer diameter of the brake disc configured to engage with beam keys 40. As such rotor brake discs 36 will rotate with the motion of the wheel while stator brake discs 38 remain stationary allowing the friction surfaces of an adjacent stator brake disc 38 and rotor brake disc 36 to engage with one another to deaccelerate the rotation of wheel 12.
During a braking procedure, splines 44 and beam keys 40 may engage with the respective lug notches 72 of rotor and stator brakes discs 36 and 38 transferring a large amount of torque into the brake discs. As described further below, the torque forces created during the braking procedure may be transferred into the underlying fiber architecture of the composite. As described further below, if the fibers of the composite are oriented in a radial arrangement, the resultant forces may be exerted in a direction generally perpendicular to the longitudinal length of the fibers. In contrast, if the fibers are oriented in a chordal (tangential) arrangement (e.g., aligned perpendicular to the radius) or radial arrangement (e.g., aligned with the radius), the resultant forces may be exerted in a direction generally along the longitudinal length of the fibers. The resulting arrangements may result in either a bending or a compressive force being exerted on the underlying fibers within the composite, neither of which are optimal for purposes of strengthening the resultant composite disc brake.
As discussed further below, the fiber performs described herein, which may be used to form rotor and stator brake discs 36 and 38, may include fiber architectures that tailor orientation of the fiber within specified regions of rotor or stator disc brakes 36 and 38. In some examples, the orientation of the fibers within the regions of rotor or stator disc brakes 36 and 38 may ultimately define lug notches 72 to an intermediate angle that may help to improve the resultant torque and strength properties of rotor or stator disc brakes 36 and 38.
The needle-punch process may introduce a plurality of needled fibers 104 into fibrous preform 100 which mechanically bind fibrous layers 102 together. Needled fibers 104 may extend in a general vertical direction (parallel to a Z-axis) aligned with central axis 108 and penetrate into two or more or fibrous layers 102. In some examples, needled fibers 104 may help secure fibrous layers 102 to one another. Additionally, or alternatively, the needle-punch process and resulting needled fibers 104 may partially compress fibrous layers 102 to form a more compacted fibrous preform 100 compared to a stack including a similar number of fibrous layers 102 that have not been consolidated together.
As described further below, each fibrous layer 102 includes a plurality of fabric segments 106 that collectively form a respective layer 102. In some examples, each fibrous layer 102 may be in the form of a planar disc or ring while in other examples each fibrous layer 102 may be non-planar. For example, fibrous preform 100 may be formed by sequentially adding abutting fabric segments 106 in the form of continuous helix about central axis 108. In such examples, each fibrous layer 102 may define a portion of the helix in terms of the number or revolutions about central axis 108. In some examples, each fibrous layer 102 may define about 0.9 to about 1.2 revolutions (e.g., about 325 degrees (°) to about 420°). In examples where a respective fibrous layer 102 defines more than one full revolution of the helix, a portion of the respective fibrous layer 102 may overlap with itself. Despite the overlap, the respective fibrous layer 102 may still be characterized as a single fibrous layer 102 within fibrous preform 100.
While some of the figures described herein show a relatively small number of layers used form the respective fibrous preforms, the preforms (e.g., fibrous preform 100) produced as a result of the techniques describe herein may include any suitable number of fibrous layers 102 (e.g., 30 or more layers) to produce the desired thickness (T) of the resultant preform. In some examples, each fibrous layer 102 may have a thickness as measured in a direction parallel (e.g., parallel or nearly parallel) to central axis 108 of about 1 millimeter (mm) to about 2 mm and the total thickness (T) of fibrous preform 100 when complete may be about 1 inch to about 3 inches (e.g., about 2.5 cm to about 7.6 cm).
In some examples, fibrous preform 100 may be constructed with lug notches 72 (not shown in
Fibrous preform 100, once completed, may be in the shape of a disc or annulus defining an outer preform diameter (OD) and inner preform diameter (ID). In some examples, the outer preform diameter (OD) of fibrous preform 100 may be about 14.5 inches (e.g., about 37 cm) to about 25 inches (e.g., about 64 cm) and the inner preform diameter (ID) of fibrous preform 100 may be about 4.5 inches (e.g., about 12 cm) to about 15 inches (e.g., about 38 cm).
In some examples, fibers 120 may be in the form of tows (e.g., bundles of individual fibers linearly aligned) of continuous filaments. Each tow may include hundreds to several thousand of individual fibers 120 unidirectionally aligned to form a single tow. In such examples, fabric 110 may include a plurality of unidirectionally aligned tows within the segment with each tow including a plurality of fibers 120.
In some examples, fabric 110 may be a duplex fabric that includes a plurality of unidirectionally aligned fibers 120 (e.g., aligned tows) that have been combined with a plurality of web fibers (not shown). The web fibers may include chopped, discontinuous, or staple fibers having an unspecified alignment that are relatively short in comparison to fibers 120 that, when combined with fibers 120 in a duplex fabric, become intertwined with aligned fibers 120 to impart integrity to fabric 110. The web fibers may define a random fiber orientation relative to each other and to aligned fibers 120.
In some examples, the formation of a duplex fabric may be accomplished by combining one or more layers of aligned tow fibers (e.g., fibers 120) with one or more layers of web fibers that are subsequently consolidated (for example, needle punched or stitched and tufted) into the layer of tow fibers to form duplex fabric. For example, a layer of web fibers may be formed by crosslapping a carded web to achieve a desired areal weight and then needle-punching the layer to form the web layer. Additionally, or alternatively, the web layer may be formed by airlaying the web fibers on top of a layer of the unidirectionally aligned fibers 120. The layer of unidirectionally aligned fibers 120 may be formed by spreading large continuous tows using a creel, to form a sheet of the desired areal weight with fiber 120 being aligned in the same direction. Both the web layer and the layer of unidirectionally aligned fibers 120 may be consolidated together to force the relatively short web fibers to become intertwined with unidirectionally aligned fibers 120 to form the duplex fabric (e.g., fabric 110).
Additionally, or alternatively, fabric 110 may be formed as a duplex fabric by initially incorporating web fibers within the tows of unidirectionally aligned fibers 120. A layer of the described tows may be formed by spreading large the tows using a creel, to form a sheet of the desired areal weight. The layer may then be consolidated (for example, needle-punched or stitched and tufted) to force the relatively short web fibers to become intertwined with unidirectionally aligned fibers 120 thereby forming the duplex fabric.
As a result of the consolidation process in either of the above examples, the web fibers become intertwined with the aligned fibers 120 and help bind aligned fibers 120 together allowing fabric 110 to be efficiently handled without having aligned fibers 120 separate or fall apart with subsequent processing. The resultant duplex fabric (e.g., fabric 110) may be more durable, retain its shape better, and be overall easier to further manufacture compared to a layer of only unidirectionally aligned fibers 120. Other techniques may also be used to form fabric 110 as a duplex fabric that includes both unidirectionally aligned fibers 120 and web fibers which may be known to those skilled in the art. In all the examples described herein, fabric 110 and the fabric segments used to from the fibrous preforms described herein may be composed of one or more layers of a duplex fabric.
In some examples, in addition to holding fabric 110 together, the web fibers used to produce the duplex fabric may ultimately be used to form or contribute to a portion of needled fibers 104 in fibrous preform 100 as a result of fibrous layers 102 being superposed (e.g., stacked on each other) and consolidated together. Additionally, or alternatively, at least some of unidirectionally aligned fibers 120 may be transformed into needled fibers 104 within fibrous preform 100 as a result of fibrous layers 102 being superposed and consolidated together. For example, the needle-punch process may break some of the unidirectionally aligned fibers 120 contained in fabric 110 and at least partially transfer the broken fibers into one or more adjacent fibrous layers 102 within fibrous preform 100 to form needled fibers 104.
Both the web fibers and unidirectionally aligned fibers 120 may be formed of the same fiber or fiber precursor materials, may be formed of different carbon fiber or carbon fiber precursor materials, or may be formed of different combinations of carbon fiber and/or carbon fiber precursor materials. In some examples, fabric 110 may be formed to have an areal fiber weight of the combined web and unidirectionally aligned fibers 120 of about 1250 grams per square meter (g/m2) to about 3000 g/m2 such as, about 1350 g/m2 to about 2000 g/m2.
The fiber orientation angle (α) of the fabric segments described herein may be in a range greater than 0° and less than +90° (e.g., having an absolute magnitude greater than 0° and less than) 90°. For example, referring back to
Each fabric segment 112-118 may be obtained from fabric 110 using any suitable technique. In some examples, fabric segment 112-118 may be die cut from fabric 110 with the fiber orientation angle (α) being obtained by adjusting the angle of the die cut relative to the orientation of unidirectionally aligned fibers 120. As will be appreciate by one skilled in the art, fabric segments 116 and 118 may be constructed using the same die cut orientation with the respective fiber orientation angles (α) of either +45° or −45° being obtained by simply flipping a respective fabric segment over (e.g., flipping fabric segment 116 over will produce fabric segment 118). Such understanding likewise holds true for intermediate fiber orientation angles (α) between 0° and 90°. For example, a fabric segment may be formed with a fiber orientation angle (α) of 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, or 85°, or any other suitable angle. If desired, to obtain a fabric segment having a negative fiber orientation angle (−α), the respective fabric segment may be simply turned over.
In some examples, the fabric segments described herein may define an arc angle (φ) such that, fabric segments forming a single fibrous layer 102 of fibrous preform 100 complete a single full revolution. For example, if a total of six arcuate fabric segments 132 are used to define one complete fibrous layer 102, each fabric segment 132 may define an arc angle (φ) of 60° so that the six fabric segments 132 when aligned with abutting edges 136 (e.g., the edges defining arc angle (φ)) in contact with the abutting edges of adjacent fabric segments 132 will complete one full revolution with each fabric segment occupying ⅙th of the respective fibrous layer 102.
In some examples, the fabric segments described herein may define arc angles (φ) that do not add up to 360° (i.e., one complete revolution) within a fibrous layer 102. For example, fabric segments 106 may be sized so that the plurality of fabric segments 106 within a respective fibrous layer 102 complete more or less than one full rotation within the layer. In some examples, each fabric segment 106 may define arc angle (φ) of about 65° to about 70° (e.g., about) 68°, however, other arc angles (φ) may be used if desired.
In some examples where the respective fabric segments (e.g., fabric segments 106) forming fibrous preform 100 each define an arc angle (φ) of about 65° to about 70°, the respective fibrous layer 102 may complete about 1.08 to about 1.17 revolutions per fibrous layer 102. For example, fabric segments 106 may be sequentially added in a continuing helix pattern. If all the respective fabric segments 106 define an arc angle (φ) of about 68°, the respective fibrous layer 102 may complete about 1.13 revolutions with a small portion of the layer (e.g., about 13%) overlapping itself.
As described further below, setting the arc angle (φ) to about 65° to about 70° (e.g., about) 68° may help to minimize the butt joint overlap of abutting edges 136 between adjacent fibrous layers 102 within the final constructed fibrous preform 100. Additionally, or alternatively, having the arc angle (o) of about 65° to about 70° (e.g., about) 68° for fabric segments 106 may help to create more uniform alignment of fibers 120 within fibrous preform 100 compared to larger arc angles (φ).
For reasons described further below, different fibrous layers 102 may differ in the magnitude or sign of the fiber orientation angle (α). For example, different layers may have the same or different magnitude, or the same or different sign (+α or −α). The fibrous layers 102 may be arranged in different patterns or sequences or layers, as described with reference to
For example, fabric segments 170 may define the positive fiber orientation angle (α) of about +10° to about +80°, or about +30° to about +60°; or about +40° to about +50°; or about +45°. In the example shown in
Each layer 162, or each fabric segment 170 may be uniform in a radial direction. For example, each layer 162 may have a uniform density in a radial direction. Alternatively or additionally, each layer 162 may have a uniform thermal conductivity in a radial direction.
In some examples, by having the fiber orientation angle (α) of the fabric segments 170 be about +10 to +80° (e.g., +45°), unidirectionally aligned fibers 120 within the respective fabric segments 170 may exhibit improved torque strength compared to a fabric segment where unidirectionally aligned fibers 120 within the fabric segment are tangentially or radially aligned (e.g., fabric segments 112 and 114). Further, such a fiber orientation angle (α) may have improved frictional and heat dissipation properties (for example, in a radial direction) compared to tangentially aligned fibers. In other examples, fabric segments 170 may have a negative fiber orientation angle −α, as described with reference to
If fibrous preform 160 is being used to construct stator disc brake 38, within a respective fibrous layer 162, all fabric segments 170 may each define the same fiber orientation angle (α) which may be about +10 to +80° (e.g., +45°).
Each fabric segment of plurality of fabric segments 170 may define any suitable arc angle (φ). In some examples, each respective fabric segment 170 defines the same arc angle (φ), for example, in a range from about 65° to about 70° (e.g., about) 68°. In some such examples, each fibrous layer 162 may include a total of six fabric segments 170. By setting the arc angles (φ) to a value of about 65° to about 70°, associated butt joints 180 between abutting edges 182 of sequentially laid fabric segments 170 may be dispersed so that respective butt joints 180 do not axially align between neighboring fibrous layers (for example, between fibrous layer 162 and a second fibrous layer neighboring fibrous layer 162), thereby improving the strength of fibrous preform 160. It will be understood that in the example described, fibrous layer 162 completes more than one revolution relative to a central axis 184 of fibrous preform 160 within a helical arrangement of fibrous layers. First fibrous layer 162 is also referred to as first fibrous layer 162A herein.
Further fibrous layers may be successively laid on second fibrous layer 162B. Thus, preform 160 may include a plurality of fibrous layers (including first fibrous layer 162A and second fibrous layer 162B) each including fabric segments having the same fiber orientation angle (α) (also referred to as the positive fiber orientation angle). The plurality of fibrous layers may be stacked in an annular arrangement.
Once fibrous preform 160B has been fully formed to a desired thickness (T), the preform may be subjected to one or more pyrolyzation and densification cycles. For example, fibrous preform 160B may be initially pyrolyzed (e.g., carbonized) to convert any carbon-precursor materials into carbon. Fibrous preform 160B 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 subsequent pyrolyzation or heat treatment cycles to infiltrate the porous preform with carbon matrix material.
A densified carbon-carbon composite material may be formed by densifying preform 160. For example, preform 160 may include reinforcing carbon fibers, and preform 160 may be carbonized and/or densified to form a carbon-carbon composite. The preform 160 may be formed by densification in presence of a load, or in absence of a load, as described elsewhere in the present disclosure. In some examples, a brake may include the densified carbon-carbon composite material.
In some examples, different fibrous layers 162 within fibrous preform 160 may include respective fabric segments 170 that define different fiber orientation angles (α) relative to the different fibrous layers 162. For example, some fibrous layers 162 may differ in one or both of magnitude or sign of the fiber orientation angle. In some examples, a first sub-plurality of fibrous layers 162 include first fabric segments having negative fiber orientation angles (−α), and a second sub-plurality of fibrous layers 162 include second fabric segments having positive fiber orientation angle (+a). In some examples, arranging the fiber orientation angles (α) between some fibrous layers to differ from one another (for example, in sign or magnitude) may help to improve the overall strength of a resultant composite formed from preform 160.
Further fibrous layers may be successively laid on second fibrous layer 262B. Thus, preform 260 may include a plurality of fibrous layers (including first fibrous layer 262A and second fibrous layer 262B) each including fabric segments having the different fiber orientation angles (+α and −α) (also referred to as the positive fiber orientation angle and the negative fiber orientation angle respectively).
In some examples, preform 260 includes a plurality of fibrous layers 262 consolidated together and forming preform 260 extending along a longitudinal axis (for example, normal to the x-y plane). The plurality of fibrous layers 262 include at least one first fibrous layer 262A and at least one second fibrous layer 262B. The at least one first fibrous layer 262A may include a plurality of first segments 270A, and the least one second fibrous layer 262B may include a plurality of second segments 270B. At least one first segment of the plurality of first segments 270A includes a plurality of reinforcing fibers extending at an angle −α relative to a radial direction extending from the longitudinal axis. At least one second segment of the plurality of second segments 270B includes a plurality of reinforcing fibers extending at an angle +α relative to the radial direction. α is greater than 0° and less than 90°.
Alternating layers in preform 260 may form a 1:1 or AB pattern, where A represents layers including fabric segments having the negative fiber orientation angle, and where B represents layers including fabric segments having the positive fiber orientation angle (or vice versa). However, layers may be laid up in different patterns, for example, as described with reference to
While segments patterns such as XY (1:1), XXYY (2:2), and XXXXXXYYYYYY (6:6) have been described, segments may extend in any combinations of numbers of X and Y segments. For example, 1:2, 2:1, 3:1, 1:3, 3:2, 2:3, . . . , m:n, for any combination of m and n, where m and n are positive integers. Further, preforms may include layers in a single pattern, or in combinations of patterns. For example, a portion of, or an entirety of, a preform may include segments in same or different segment patterns. For example, a first portion of a preform may include segments in an XY segment pattern, while a second portion of the preform may include segments in an XXXXXX:YYYYYY segment pattern. The arrangement of segments patterns may be symmetric, asymmetric, periodic, or periodic in sections. In some examples, the fibers may be in randomized patterns, but including a predetermined fraction of segments of type X compared to type Y. Respective neighboring layers or segments may be in direct contact.
Further, while segment layup patterns have been described with reference to two segment types (X and Y), more than two types of segments may be present. For example, additional types of segments (T, V, W, and so on) may be present, differing in one or both of magnitude of sign or angle. In some examples, segment layup patterns may include at least one first fabric segment including radial fiber orientation or tangential fiber orientation, and at least one second fabric segment including a non-radial and non-tangential fiber orientation. Moreover, segments X and Y (or other segments) may differ (i) only in magnitude, but not in sign, (ii) only in sign, but not magnitude, or (iii) both in magnitude or sign.
After a preform is formed, for example, preform 100, preform 160, or any other preform according to the present disclosure, the preform may be carbonized and/or densified to form a composite.
While load may be applied during carbonization as described with reference to
The fibrous preforms described herein may be formed using any suitable technique.
In some examples, the disclosure describes a method including laying up a plurality of layers 262 including at least one first fibrous layer 262A and at least one second fibrous layer 262B to form preform 260 extending along a longitudinal axis (800). The at least one first fibrous layer 262A includes a plurality of first segments 270A, and the least one second fibrous layer 262B includes a plurality of second segments 270B. The method further includes consolidating preform 260 (802). The consolidating (802) may include, for example, needle punching or stitching or tufting plurality of layers 262. At least one first segment of the plurality of first segments 270A includes a plurality of reinforcing fibers extending at an angle −α relative to a radial direction extending from the longitudinal axis. At least one second segment of the plurality of second segments 270B includes a plurality of reinforcing fibers extending at an angle +α relative to the radial direction. α is greater than 0° and less than 90°.
The laying up (800) may include superposing (e.g., helically stacking) and needle-punching a plurality of fabric segments 270A and 270B to produce a plurality of fibrous layers 262A and 262B consolidated together to form fibrous preform 260B in the shape of an annulus. The plurality of fibrous layers 262A and 2662B may be stacked in an annular arrangement.
The technique may further include pyrolyzing fibrous preform 260 (804); and densifying the resultant preform 260 (806).
As described above, each fibrous layer 262 may include a respective plurality of fabric segments 270A or 270B, which may be sequentially added in by stacking the plurality of fabric segments to form a helix. In some examples, each fibrous layer 262 may complete about 0.9 to about 1.2 revolutions of the helix such that butt joints 182 between abutting edges 180 do not radially overlap between adjacent fibrous layers 262.
Each fabric segment or set of fabric segments may be consolidated (for example, needle-punched or stitched and tufted) after being added to fibrous preform 260. In some examples, the fabric segments may be consolidated into preform 260 on a layer-by-layer basis. Additionally, or alternatively, more than one fibrous layers 262 may be added to preform 260 and then the collective superposed layers 262 may be consolidated. The entire process may then continue until the desired preform thickness (T) is obtained.
Once fibrous preform 260 has been formed, fibrous preform 260 may be pyrolyzed (804) to convert any carbon-precursor material into carbon through a thermal degradation process to effectively burn off any non-carbon material. For example, fibrous preform 260 may be carbonized by heating fibrous preform 260 in a retort under inert or reducing conditions to remove the non-carbon constituents (hydrogen, nitrogen, oxygen, etc.) from fibers 120 and/or needled fibers 104. The carbonization can be carried out using retort, such as an autoclave, a furnace, a hot isostatic press, a uniaxial hot press, or the like. In each of these techniques, fibrous preform 260 may be heated in the inert atmosphere at a temperature in the range of about 600° C. to about 1000° C. while optionally being mechanically compressed. The mechanical compression may be used to define the geometry (e.g., thickness (T)) of fibrous preform 260. In other examples, no mechanical compression or load is applied. Thus, in some examples, one or both of carbonizing or the densifying (806) of preform 260 is performed in an absence of a load or a constraint on the preform 260.
In some examples, the retort may be purged gently with nitrogen for approximately 1 hour, then slowly heated to about 900° C. over the course of approximately 10-20 hours, followed by elevating the temperature to about 1050° C. over approximately 1-2 hours. The retort then may be held at about 1050° C. for approximately 3-6 hours before the carbonized preform is allowed to cool overnight. In some examples, the carbonization step can be carried out at even higher temperature, including up to about 1800° C. or up to about 2600° C.
After carbonization, fibrous preform 260 may be subjected to one or more densification cycles to form a composite (806). Example densification cycles may include, for example, being densified by applying one or more cycles of CVI/CVD of a carbonaceous gas. Any suitable carbonaceous gas may be used during the 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 to densify a fibrous preform 260 via CVI/CVD may occur substantially in a vacuum space (e.g., a vessel with an internal environment at less than 100 Torr) or under an inert gas environment so as to control the chemical deposition reaction. In some examples, during application of the CVI/CVD gas, the environment including fibrous preform 260 may be heated to an elevated temperature, for example about 900° C. to about 1200° C., to promote the chemical deposition reaction.
In other examples, fibrous preform 260 may be densified (806) using other suitable techniques including for example, resin infiltration and carbonization via resin transfer mold (RTM) processing, vacuum pressure infiltration (VPI) processing, high pressure infiltration (HPI), or the like. In some examples, the densification step (806) may produce a densified composite substrate having a final density of about 1.65 to about 1.95 g/cc.
In some examples, during or after the densification of fibrous preform 260, the major friction surfaces of the resultant composite may be sculpted into a desired shape, such as a final brake disc shape. For example, composite substrate may be ground in the shape of a densified composite disc brake having a final thickness T (e.g., about 1.4 inches (35.56 mm)). Additionally, or alternatively, lug notches 72 may be formed at this time.
Slot pull tests were conducted on a baseline preform size, a 6:6 radial/chordal (R/C) preform, a 6:6±45° preform, a 1:1±45° preform, and a 1:1 radial/chordal preform. The results are shown in TABLE 1.
Slot pull tests were performed on a baseline preform, and with increasing needle punch density.
The following clauses illustrate example subject matter described herein.
Clause 1: A preform for a composite, the preform including:
Clause 2: The preform of clause 1, where the plurality of fibrous layers are stacked in an annular arrangement.
Clause 3: The preform of any of clauses 1 or 2, where the reinforcing fibers include one or more of carbon, a carbon precursor, boron, or silica.
Clause 4: The preform of clause 3, where the carbon precursor includes an aromatic species.
Clause 5: The preform of any of clauses 1 to 4, where the plurality of fibrous layers includes an XY (1:1) segment pattern of the at least one first segment and the at least one second segment.
Clause 6: The preform of any of clauses 1 to 4, where the plurality of fibrous layers includes an XXYY (2:2) segment pattern of the at least one first segment and the at least one second segment.
Clause 7: The preform of any of clauses 1 to 4, where the plurality of fibrous layers includes an XXXXXXYYYYYY (6:6) segment pattern of the at least one first segment and the at least one second fibrous segment.
Clause 8: The preform of any of clauses 1 to 7, where respective neighboring layers of the plurality of fibrous layers are in direct contact.
Clause 9: The preform of any of clauses 1 to 8, where a is 45°.
Clause 10: The preform of any of clauses 1 to 8, where a is 60°.
Clause 11: The preform of any of clauses 1 to 10, where each layer of the plurality of fibrous layers has a uniform density in a radial direction.
Clause 12: The preform of any of clauses 1 to 11, where each layer of the plurality of fibrous layers has a uniform thermal conductivity in a radial direction.
Clause 13: A densified carbon-carbon composite material formed by densifying the preform of any of clauses 1 to 12.
Clause 14: The carbon-carbon composite material of clause 13, where the densifying the preform is performed in an absence of a load or a constraint on the preform.
Clause 15: A brake disc including the densified carbon-carbon composite material of clause 13.
Clause 16: A method including:
Clause 17: The method of clause 16, where the laying up the plurality of fibrous layers includes stacking the plurality of fibrous layers in an annular arrangement.
Clause 18: The method of any of clauses 16 or 17, where the reinforcing fibers include one or more of carbon, a carbon precursor, boron, or silica.
Clause 19: The method of clause 18, where the carbon precursor includes an aromatic species.
Clause 20: The method of any of clauses 16 to 19, where the plurality of fibrous layers includes an XY (1:1) segment pattern of the at least one first segment and the at least one second segment.
Clause 21: The method of any of clauses 16 to 19, where the plurality of fibrous layers includes an XXYY (2:2) segment pattern of the at least one first segment and the at least one second segment.
Clause 22: The method of any of clauses 16 to 19, where the plurality of fibrous layers includes an XXXXXXYYYYYY (6:6) segment pattern of the at least one first segment and the at least one second fibrous segment.
Clause 23: The method of any of clauses 16 to 22, where respective neighboring fibrous layers of the plurality of fibrous layers are in direct contact.
Clause 24: The method of any of clauses 16 to 23, where a is 45°.
Clause 25: The method of any of clauses 16 to 23, where a is 60°.
Clause 26: The method of any of clauses 16 to 25, further including:
Clause 27: The method of clause 26, where the carbonizing or the densifying the preform is performed in an absence of a compressive load or on the preform.
Clause 28: The method of clause 26, further including terminating the densifying at a predetermined fiber volume fraction or a predetermined pore size distribution of the preform.
Clause 29: The method of clause 26, further including forming a brake including the preform.
Clause 30: The method of any of clauses 16 to 29, further including compressing the preform.
Clause 31: The method of any of clauses 16 to 30, where each layer of the plurality of fibrous layers has a uniform density in a radial direction.
Clause 32: The method of any of clauses 16 to 31, where each layer of the plurality of fibrous layers has a uniform thermal conductivity in a radial direction.
Various examples have been described. These and other examples are within the scope of the following claims.
