BACKGROUND INFORMATION
1. Field:
[0001] The present disclosure relates generally to carbon fibers. More particularly, the present disclosure relates to a method and apparatus for manufacturing carbon fibers using polyacrylonitrile material and a flattening process.
2. Background:
[0002] Carbon fibers have high stiffness, high tensile strength, low weight, high chemical resistance, high temperature tolerance, and low thermal expansion. These properties make carbon fibers particularly useful in certain applications, including aerospace, civil engineering, military, and other types of applications. One of the most common uses of carbon fibers is in the formation of composites. For example, carbon fibers may be combined with resin to form a composite.
[0003] Typically, carbon fiber is supplied in the form of a continuous tow, which is a bundle of hundreds to thousands of individual carbon filaments. These carbon filaments are cylindrical in shape and comprised almost entirely of carbon. Carbon fibers may be derived from different types of materials including, but not limited to, polyacrylonitrile (PAN), rayon, and petroleum pitch.
[0004] One method of manufacturing carbon fibers using polyacrylonitrile (PAN) filaments includes forming a plurality of PAN filaments from PAN material, with the PAN filaments having a cylindrical shape. The PAN filaments may be spread out in a single-layered row, forming a tow band. The tow band is tensioned and heated to carbonize the PAN filaments in the tow band. The tow band may then be further tensioned and heated to graphitize the carbon filaments in the tow band.
[0005] A sizing, which is a type of coating, may be applied to the carbon fiber. The sizing may protect the carbon fiber during handling and processing and may hold the filaments of the carbon fiber together. Further, when the carbon fiber is to be used in the fabrication of a composite, the sizing may be selected based on the type of resin to be used in forming the composite. In certain situations, it may be desirable to apply multiple sizings to carbon fibers to improve the quality of the composites formed using these carbon fibers.
[0006] Additionally, design and manufacturing costs using carbon fibers manufactured through the process described above may be more expensive than desired. Some of the carbon fibers manufactured through this process may not have a desired level of stiffness. Further, the time required for carbonization and graphitization may also be longer than desired. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.
SUMMARY
[0007] In one illustrative embodiment, a method is provided for manufacturing a carbon fiber. Pressure is applied to a filament to change a cross-sectional shape of the filament and create a plurality of distinct surfaces on the filament. The filament is converted into a graphitic carbon fiber having the plurality of distinct surfaces. A plurality of sizings is applied to the plurality of distinct surfaces of the graphitic carbon fiber in which the plurality of sizings includes at least two different sizings.
[0008] In yet another illustrative embodiment, a method is provided for manufacturing a carbon fiber. A polyacrylonitrile polymer is extruded through a plurality of openings of an output system to form a plurality of filaments. Each filament of the plurality of filaments is flattened using a roller system to elongate a cross-sectional shape of each filament and create a plurality of distinct surfaces on each filament. The plurality of filaments is converted into a plurality of graphitic carbon fibers, with each of the plurality of graphitic carbon fibers having the plurality of distinct surfaces. A plurality of sizings is applied to each graphitic carbon fiber of the plurality of graphitic carbon fibers in which the plurality of sizings includes at least two different sizings.
[0009] In another illustrative embodiment, an apparatus comprises a roller system, a heat system, and a plurality of surface sizing applicators. The roller system may be used to apply pressure to a filament to change a cross-sectional shape of the filament and create a plurality of distinct surfaces. The heat system may be used to convert the filament into a graphitic carbon fiber. The plurality of surface sizing applicators may be used to apply a plurality of sizings to the plurality of distinct surfaces of the graphitic carbon fiber in which the plurality of sizings includes at least two different sizings.
[0010] The features and functions can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments in which further details can be seen with reference to the following description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The novel features believed characteristic of the illustrative embodiments are set forth in the appended claims. The illustrative embodiments, however, as well as a preferred mode of use, further objectives and features thereof, will best be understood by reference to the following detailed description of an illustrative embodiment of the present disclosure when read in conjunction with the accompanying drawings, wherein:
Figure 1 is an illustration of a manufacturing environment in the form of a block diagram in accordance with an illustrative embodiment;
Figure 2 is an illustration of a fiber processing system in accordance with an illustrative embodiment;
Figure 3 is an illustration of a group of cross-sectional shapes for a flattened filament in accordance with an illustrative embodiment;
Figure 4 is a flowchart of a process for manufacturing a carbon fiber in accordance with an illustrative embodiment;
Figure 5 is a flowchart of a process for manufacturing carbon fibers in accordance with an illustrative embodiment;
Figure 6 is a flowchart of a process for transforming a plurality of filaments into a plurality of graphitic carbon fibers in accordance with an illustrative embodiment;
Figure 7 is a flowchart of a process for applying sizings to a graphitic carbon fiber in accordance with an illustrative embodiment;
Figure 8 is a flowchart of an aircraft manufacturing and service method in accordance with an illustrative embodiment; and
Figure 9 is a block diagram of an aircraft in accordance with an illustrative embodiment.
DETAILED DESCRIPTION
[0012] The illustrative embodiments recognize and take into account different considerations. For example, the illustrative embodiments recognize and take into account that it may be desirable to have a method and apparatus for manufacturing carbon fibers that allows different sizings to be applied to a single carbon fiber. In particular, it may be desirable to have a method and apparatus for manufacturing carbon fibers in a manner that reduces the overall costs associated with the design and manufacturing of parts using these carbon fibers.
[0013] Thus, the illustrative embodiments provide a method for manufacturing a carbon fiber. In one illustrative embodiment, a polymer, such as a polyacrylonitrile polymer, may be extruded through a plurality of openings of an output system to form a plurality of filaments. Pressure may be applied to each filament of the plurality of filaments to change a cross-sectional shape of each filament and create a plurality of distinct surfaces on each filament. For example, each filament may be flattened and elongated to create a plurality of distinct surfaces. The plurality of filaments may be converted into a plurality of graphitic carbon fibers, with each of the plurality of graphitic carbon fibers having the plurality of distinct surfaces. A plurality of sizings may be applied to each graphitic carbon fiber of the plurality of graphitic carbon fibers. For example, a first sizing may be applied to one surface of a graphitic carbon fiber and a second sizing may be applied to another surface of the graphitic carbon fiber. These two sizings may be applied to the graphitic carbon fiber simultaneously or at different times.
[0014] The pressure may be applied to the plurality of filaments using a roller system configured to flatten the plurality of filaments. Flattening the plurality of filaments may elongate (or flatten) the cross-sectional shape of each of the plurality of filaments. This flattening may allow filaments in the plurality of filaments to band together more densely during manufacturing. Thus, a more densely packed carbon fiber reinforced plastic (CFRP) may be formed. Further, higher part stiffness may be achieved with a more densely packed carbon fiber, which may, in turn, lead to reduced weight in composite parts fabricated using these carbon fibers.
[0015] Further, the increased surface area exposed by flattening the plurality of filaments may allow two sizings to be easily applied to the plurality of filaments. For example, a first sizing may be applied to the top surface of each of the plurality of filaments exposed by flattening. A second sizing may be applied to the bottom surface of each of the plurality of filaments exposed by flattening.
[0016] In one illustrative example, the sizings may be two different types of epoxy resins. Using these different sizings may help chemically align the tetra-functional epoxy molecules as these molecules infiltrate the space between the plurality of filaments making up the carbon fiber bed during prepregging or resin infusion. This chemical alignment may increase the uniformity of the carbon fiber. Increasing uniformity of the carbon fiber within a composite laminate, such as a carbon fiber reinforced plastic laminate, may increase the allowable mechanical properties of the composite laminate. Increasing the allowable mechanical properties of the composite laminate may decrease the amount of composite material that is needed in the manufacturing of parts. Thus, flattening the plurality of filaments prior to carbonization and graphitization may help decrease material and manufacturing costs, synergistically reduce weight, and improve overall manufacturing efficiency.
[0017] Additionally, flattening the filaments prior to carbonization and graphitization may reduce the time required for carbonization and graphitization. The time-at-temperature required for both of these steps may be determined by the conduction of heat through the thickness of a carbon fiber. Carbon fibers that have been roll-flattened have a shorter minimum distance for that conduction of heat, thereby reducing the time needed for carbonization and graphitization. Further, the reduction of time-at-temperature may reduce the manufacturing cost of carbon fibers.
[0018] Referring now to the figures and, in particular, with reference to
Figure 1, an illustration of a manufacturing environment is depicted in the form of a block diagram in accordance with an illustrative embodiment. Manufacturing environment
100 may be an environment in which carbon fibers
102 are manufactured.
[0019] In these illustrative examples, carbon fibers
102 may be manufactured using fiber processing system
104. Fiber processing system
104 may include output system
106, roller system
108, tension system
110, heat system
112, and plurality of surface sizing applicators
113. In one illustrative example, tension system
110 and heat system
112 are independent systems. In other illustrative examples, tension system
110 and heat system
112 may be combined to form a single system.
[0020] Output system
106 has plurality of openings
116. Output system
106 may take the form of, for example, die
114 having plurality of openings
116. Polymer
118 may be extruded through output system
106 and forced out of plurality of openings
116 in the form of plurality of filaments
120. In one illustrative example, polymer
118 takes the form of polyacrylonitrile (PAN) polymer
122. Accordingly, plurality of filaments
120 may also be referred to as a plurality of PAN filaments.
[0021] In this illustrative example, each of the openings of plurality of openings
116 may have a circular or near-circular shape. Thus, each filament of plurality of filaments
120 extruded from output system
106 may have a cylindrical or near-cylindrical shape. For example, plurality of filaments
120 may include filament
121. Filament
121 may have a substantially cylindrical shape such that filament
121 has cross-sectional shape
126 that is substantially circular.
[0022] Roller system
108 is used to apply pressure
124 to plurality of filaments
120 to change the cross-sectional shape of each of plurality of filaments
120 and create distinct surfaces on each filament. Pressure
124 may be applied to a filament, such as filament
121, by applying a force to the surface of the filament per unit area over which that force is distributed
[0023] For example, without limitation, roller system
108 may be used to apply pressure
124 to change cross-sectional shape
126 of filament
121 and create plurality of distinct surfaces
130. Cross-sectional shape
126 may be changed from substantially circular to substantially oval, elliptical, rectangular with rounded corners, a similar flattened shape, or a more flattened shape with edges that are sharp, rounded, or both. In this manner, the flattening of filament
121 increases the exposed surface area of filament
121.
[0024] Further, flattening filament
121 creates plurality of distinct surfaces
130, thereby providing more surfaces on which to apply different sizings. For example, prior to flattening, filament
121 may have a substantially cylindrical shape with one continuous outer surface. Flattening filament
121 may create plurality of distinct surfaces
130 formed by edges that may be sharp our rounded. As one illustrative example, flattening filament
121 may create at least first surface
131 and second surface
132. In some cases, first surface
131 may take the form of a top surface and second surface
132 may take the form of a bottom surface.
[0025] Roller system
108 may be implemented in a number of different ways. In one illustrative example, without limitation, roller system
108 may include first roller
127 and second roller
128 positioned relative to each other with minimal to no gap in between these two rollers. In one illustrative example, first roller
127, second roller
128, or both may have a powder coating to protect plurality of filaments
120 and to prevent plurality of filaments
120 from sticking to these rollers.
[0026] Plurality of filaments
120 may be passed between first roller
127 and second roller
128 to create pressure
124 that flattens plurality of filaments
120. As one illustrative example, first roller
127 may be positioned above plurality of filaments
120, while second roller
128 is positioned below plurality of filaments
120. Running plurality of filaments
120 between these two rollers flattens plurality of filaments
120. For example, running filament
121 between first roller
127 and second roller
128 flattens cross-sectional shape
126 of filament
121.
[0027] The flattening of plurality of filaments
120 by roller system
108 may enable plurality of filaments
120 to form carbon fibers
102 that may be more densely packed in composite manufacturing. In particular, the flattening allows the packing density of carbon fibers in forming carbon fiber reinforced plastics to be increased. The higher packing density may improve part stiffness and strength, which may, in turn, lead to reduced weight in composites that are fabricated using these carbon fibers. In particular, the higher packing density may allow increased fiber volume within the composite without adding additional carbon fibers.
[0028] Once plurality of filaments
120 have been flattened as described above, plurality of filaments
120 may be tensioned, while applying first level of heat
134 to the plurality of filaments
120, to carbonize plurality of filaments
120. Plurality of filaments
120 may be carbonized to form plurality of amorphous carbon fibers
135. For example, filament
121 may be tensioned, while applying first level of heat
134 to filament
121, to form amorphous carbon fiber
136.
[0029] Heat system
112 may include, for example, without limitation, one or more ovens. First level of heat
134 may be a lower level of heat selected to cause the carbonization of plurality of filaments
120. For example, without limitation, first level of heat
134 may be between about 600 degrees Celsius and about
800 degrees Celsius. In some illustrative examples, first level of heat
134 may be between about 200 degrees Celsius and about 1000 degrees Celsius. In other illustrative examples, first level of heat
134 may be between about 1000 degrees Celsius and about 1600 degrees Celsius.
[0030] Tension system
110 is used to perform the tensioning of plurality of filaments
120. In one illustrative example, tensioning plurality of filaments
120 includes stretching plurality of filaments
120 in a manner that elongates each filament and reduces the diameter of each filament, but does not overly change the cross-sectional shape of each filament. For example, without limitation, plurality of filaments
120 may be stretched over series of rollers
139 to cause each of plurality of filaments
120 to become longer and thinner and band together plurality of filaments
120.
[0031] In this illustrative example, heat system
112 applies first level of heat
134 to plurality of filaments
120 prior to the tensioning of plurality of filaments
120 and during at least a portion of the time that plurality of filaments
120 is tensioned. In other illustrative examples, heat system
112 applies first level of heat
134 to plurality of filaments
120 after the tensioning of plurality of filaments
120.
[0032] Plurality of amorphous carbon fibers
135 may be further tensioned using tension system
110, while applying second level of heat
140 using heat system
112, to form plurality of graphitic carbon fibers
138. For example, amorphous carbon fiber
136 may be further tensioned, while applying second level of heat
140 to amorphous carbon fiber
135, to form graphitic carbon fiber
142. In some illustrative examples, a middle interior portion of graphitic carbon fiber
142 may remain amorphous.
[0033] This secondary tensioning and heating process may be performed in a manner similar to the first tensioning and heating process described above. However, amorphous carbon fiber
136 may be stretched with a greater amount of tension than applied to filament
121.
[0034] Further, second level of heat
140 may be a higher level of heat than first level of heat
134. In particular, second level of heat
140 may be selected to cause the graphitization of amorphous carbon fiber
136. For example, second level of heat
140 may be above 1000 degrees Celsius. In some cases, second level of heat
140 may be above 1200 degrees Celsius. In yet other illustrative examples, second level of heat
140 may be between about 1600 degrees Celsius and 3000 degrees Celsius.
[0035] The flattening of plurality of filaments
120 using roller system
108 reduces the thickness of each of plurality of filaments
120. Accordingly, the time needed for the heat produced by heat system
112 to penetrate through this thickness is reduced. Accordingly, the flattening of plurality of filaments
120 reduces the overall time needed to carbonize and graphitize plurality of filaments
120.
[0036] In some illustrative examples, heat system
112 may include set of ovens
141 for applying first level of heat
134 to plurality of filaments
120 and second level of heat
140 to plurality of amorphous carbon fibers
135, respectively. Set of ovens
141 may include one oven capable of switching between first level of heat
134 and second level of heat
140 or two ovens for providing these two different levels of heat. Similarly, tension system
110 may include set of tension devices
143 for applying a first amount of tension to plurality of filaments
120 and a second amount of tension to plurality of amorphous carbon fibers
135. Set of tension devices
143 may include one tension device for providing applying these different amounts of tension or multiple tension devices.
[0037] Because roller system
108 creates plurality of distinct surfaces
130 that are exposed on each filament of plurality of filaments
120, and thereby on each graphitic carbon fiber of plurality of graphitic carbon fibers
138, plurality of sizings
145 may be applied to each graphitic carbon fiber. For example, without limitation, plurality of sizings
145 may be applied to plurality of distinct surfaces
130 on graphitic carbon fiber
142. In one illustrative example, a different sizing may be applied to each distinct surface of graphitic carbon fiber
142. In other illustrative examples, each two distinct surfaces of graphitic carbon fiber
142 may be coated with at different sizings.
[0038] As one illustrative example, first sizing
144 may be applied to a first surface of graphitic carbon fiber
142. Further, second sizing
148 may be applied to a second surface of graphitic carbon fiber
142 using.
[0039] First sizing
144 and second sizing
148 are chemical treatments that protect the physical characteristics of graphitic carbon fiber
142. Further, these sizings may provide lubrication for ease of handling. Still further, these sizings may enable resin to bond to graphitic carbon fiber
142 more easily. First sizing
144 and second sizing
148 may be selected such that these two sizings are mutually attractive to prevent undesired twisting of graphitic carbon fiber
142. In one illustrative example, epoxy resin water-based sizings are used for both first sizing
144 and second sizing
148.
[0040] Applying two different sizings to graphitic carbon fiber
142 may allow graphitic carbon fiber
142 to be customized and may improve uniformity in any composite laminate that is created using graphitic carbon fiber
142. In particular, using two different epoxy sizings may chemically align the tetra-functional epoxy molecules as these molecules infiltrate the space between the filaments of graphitic carbon fiber, which may improve uniformity. A more uniform carbon fiber may allow a more uniform composite laminate to be fabricated, which may, in turn, decrease the amount of composite material that is needed, which may, in turn, decrease material and manufacturing costs and reduce weight.
[0041] Each of plurality of sizings
145 may be applied to graphitic carbon fiber
142 using one of plurality of surface sizing applicators
113. In particular, each of plurality of surface sizing applicators
113 may be configured for applying a sizing to one distinct surface. In other words, each of plurality of surface sizing applicators
113 may be a device for applying a sizing to a single surface or size of graphitic carbon fiber
142. Depending on the implementation, plurality of surface sizing applicators
113 may be used to apply plurality of sizings
145 to the various surfaces of plurality of distinct surfaces
130 of graphitic carbon fiber
142 simultaneously, serially, or at different times.
[0042] Plurality of surface sizing applicators
113 may be implemented in a number of different ways. For example, a surface sizing applicator of plurality of surface sizing applicators
113 may comprise at least one of sizing application roller
150, sizing application spray
152, sizing application brush
154, or chemical bath
155.
[0043] As used herein, the phrase "at least one of," when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, step, operation, process, or category. In other words, "at least one of" means any combination of items or number of items may be used from the list, but not all of the items in the list may be required.
[0044] For example, without limitation, "at least one of item A, item B, or item C" or "at least one of item A, item B, and item C" may mean item A; item A and item B; item B; item A, item B, and item C; item B and item C; or item A and C. In some cases, "at least one of item A, item B, or item C" or "at least one of item A, item B, and item C" may mean, but is not limited to, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.
[0045] Sizing application roller
150 allows a sizing to be rolled onto a surface. Sizing application spray
152 allows a sizing to be sprayed onto a surface. Sizing application brush
154 allows a sizing to be brushed onto a surface. Further, chemical bath
155 allows a sizing to be applied to remaining surfaces after one of these other applicators has been used to apply a different sizing to a single surface. For example, one of sizing application roller
150, sizing application spray
152, and sizing application brush
154 may be used to apply a sizing to one surface. Chemical bath
155 may then be used to apply a different sizing to one or more other surfaces.
[0046] In some cases, both sizing application roller
150 and sizing application spray
152 may be used to apply two different sizings to two different surfaces of plurality of distinct surfaces
130. The application of the two different sizings may be performed simultaneously or at different times. In other cases, at least two different sizings may be applied to different portions of the same distinct surface. In this manner, depending on the implementation, two or more of the same type or different types of surface sizing applicators from plurality of surface sizing applicators
113 may be used to apply discrete sizings to at least two distinct surfaces of plurality of distinct surface
130 simultaneously or at different times.
[0047] In this manner, using roller system
108 to flatten cross-sectional shape
126 of filament
121 may improve the quality of graphitic carbon fiber
142 that is produced. Further, manufacturing carbon fibers
102 using the processes and systems described above may increase manufacturing efficiency and reduce manufacturing costs associated with composite manufacturing.
[0048] The illustration in
Figure 1 is not meant to imply physical or architectural limitations to the manner in which an illustrative embodiment may be implemented. Other components in addition to or in place of the ones illustrated may be used. Some components may be optional. Also, the blocks are presented to illustrate some functional components. One or more of these blocks may be combined, divided, or combined and divided into different blocks when implemented in an illustrative embodiment.
[0049] For example, in some cases, fiber processing system
104 may include oxidation system
156. Oxidation system
156 may be used to thermally oxidize plurality of filaments
120. In one illustrative example, oxidation system
156 may thermally oxidize plurality of filaments
120 in air at a temperature below about 300 degrees Celsius. Thermally oxidizing plurality of filaments
120 stabilizes plurality of filaments
120. The oxidation of plurality of filaments
120 may be performed prior to the carbonization of plurality of filaments
120. Depending on the implementation, the oxidation may be performed prior to or after the flattening of plurality of filament
120.
[0050] With reference now to
Figure 2, an illustration of a fiber processing system is depicted in accordance with an illustrative embodiment. Fiber processing system
200 may be an example of one implementation for fiber processing system
104 in
Figure 1.
[0051] As depicted, fiber processing system
200 includes output system
202, roller system
204, oxidation system
205, carbonization system
206, graphitization system
207, first sizing application roller
208, and second sizing application roller
210. In this illustrative example, output system
202 and roller system
204 may be examples of implementations for output system
106, roller system
108, respectively, in
Figure 1. First sizing application roller
208 and second sizing application roller
210 may be an example of one implementation for plurality of surface sizing applicators
113 in
Figure 1.
[0052] As depicted, polymer
211 is extruded through output system
202 and forced out of output system
202 as plurality of filaments
212. Plurality of filaments
212 may be an example of one implementation for plurality of filaments
120 in
Figure 1. In this illustrative example, plurality of filaments
212 may be collectively referred to as PAN fibers
214. Further, each of plurality of filaments
212 may have a substantially cylindrical shape, such that each filament has a cross-sectional shape that is substantially circular.
[0053] Roller system
204 receives plurality of filaments
212 and applies pressure to plurality of filaments to change a cross-sectional shape of each of plurality of filaments
212 and create a plurality of distinct surfaces on each filament. As depicted, roller system
204 may include first roller
216 and second roller
218. Passing plurality of filaments
212 between first roller
216 and second roller
218 flattens the cross-sectional shape of plurality of filaments
212. For example, the substantially circular cross-sectional shape of each of plurality of filaments
212 may be changed to substantially oval, elliptical, or rectangular with rounded corners.
[0054] In this illustrative example, flattening plurality of filaments
212 between first roller
216 and second roller
218 creates a plurality of distinct surfaces for each of plurality of filaments
212. For example, flattening each filament may create a plurality of edges that define a plurality of distinct surfaces, which may include a top surface and a bottom surface for. The edges defining the plurality of distinct surfaces may be rounded or sharp, depending on the extent and type of flattening performed. Further, flattening plurality of filaments
212 may create more exposed surface area compared to when each of plurality of filaments
212 has a cylindrical shape.
[0055] In some illustrative examples, plurality of filaments
212 may be stretched prior to being received by oxidation system
205. For example, without limitation, fiber processing system
200 may also include tension system
213 for stretching plurality of filaments
212. In one illustrative example, tension system
213 includes a series of rollers (not shown) that may be used to stretch plurality of filaments
212 to make each filament longer and thinner without overly changing the cross-sectional shape of each filament.
[0056] Oxidation system
205 may receive PAN fibers
214 after plurality of filaments
212 has been stretched. Oxidation system
205 may thermally oxidize PAN fibers
214.
[0057] Thereafter, carbonization system
206 carbonizes PAN fibers
214 to form amorphous carbon fibers
220. Amorphous carbon fibers
220 may be an example of one implementation for plurality of amorphous carbon fibers
135 in
Figure 1. In one illustrative example, carbonization system
206 may include an oven that applies a first level of heat having a temperature selected to carbonize PAN fibers
214.
[0058] Graphitization system
207 graphitizes amorphous carbon fibers
220 by applying a second level of heat to amorphous carbon fibers
220. The second level of heat may be higher than the first level of heat applied by carbonization system
206 and may be selected to graphitize amorphous carbon fibers
220. Graphitic carbon fibers
222 may be an example of one implementation for plurality of graphitic carbon fibers
138 in
Figure 1.
[0059] Thereafter, a first sizing is applied to graphitic carbon fiber
222 by running first sizing application roller
208 over the top surfaces of graphitic carbon fibers
222. In particular, first sizing application roller
208 may pick up the sizing from chemical bath
223 and apply this sizing to the top surfaces of graphitic carbon fibers
222 as first sizing application roller
208 runs over these top surfaces. The first sizing may be formulated to protect the physical properties of graphitic carbon fiber
222 and prepare graphitic carbon fiber
222 for combination with other materials.
[0060] Additionally, a second sizing is applied to graphitic carbon fiber
222 by running second sizing application roller
210 over the bottom surfaces of graphitic carbon fiber
222. In particular, second sizing application roller
210 may pick up the sizing from chemical path
225 and apply this sizing to the bottom surfaces of graphitic carbon fibers
222 as second sizing application roller
210 runs over these bottom surfaces. The second sizing may be formulated to protect the physical properties of graphitic carbon fiber
222 and prepare graphitic carbon fiber
222 for combination with other materials.
[0061] Once the first sizing and the second sizing have been applied to graphitic carbon fibers
222, these graphitic carbon fibers
222 may be spun around spool
224 to form carbon tow
226. Carbon tow
226 may be used to fabricate composite laminates.
[0062] The illustration of fiber processing system
200 in
Figure 2 is not meant to imply physical or architectural limitations to the manner in which an illustrative embodiment may be implemented. Other components in addition to or in place of the ones illustrated may be used. Some components may be optional.
[0063] The different components shown in
Figure 2 may be illustrative examples of how components shown in block form in
Figure 1 can be implemented as physical structures. Additionally, some of the components in
Figure 2 may be combined with components in
Figure 1, used with components in
Figure 1, or a combination of the two.
[0064] With reference now to
Figure 3, an illustration of a group of cross-sectional shapes for a flattened filament is depicted in accordance with an illustrative example. Group of cross-sectional shapes
300 may include potential cross-sectional shapes for a filament, such as filament
121 in
Figure 1, after the filament has been flattened by a roller system, such as roller system
108 in
Figure 1.
[0065] As depicted, group of cross-sectional shapes
300 may include first shape
302, second shape
304, third shape
306, and fourth shape
308. Although only four potential cross-sectional shapes are depicted, group of cross-sectional shapes
300 may include other potential shapes, depending on the implementation.
[0066] First shape
302 may be an elliptical shape that defines first surface
310 and second surface
312. Second shape
304 may be a rectangular shape with edges that define first surface
314 and second surface
316. Third shape
306 may be another rectangular shape with even more rounded edges that define first surface
318 and second surface
320. Fourth shape
308 may be a triangular shape that defines first surface
322, second surface
324, and third surface
326.
[0067] In this manner, a filament, such as filament
121 in
Figure 1, may be flattened to form various shapes. Filaments with these types of shapes may be converted into carbon fibers that can be more densely packed in composite manufacturing as compared to filaments with substantially circular cross-sectional shapes. Further, with the type of potential shapes included in group of cross-sectional shapes
300, different sizings may be easily applied to distinct surfaces of the carbon fibers.
[0068] With reference now to
Figure 4, an illustration of a process for manufacturing a carbon fiber is depicted in the form of a flowchart in accordance with an illustrative embodiment. The process illustrated in
Figure 4 may be implemented using fiber processing system
104 in
Figure 1 or fiber processing system
200 described in
Figure 2.
[0069] The process may begin by extruding a polymer through an opening of an output system to form a filament (operation
400). In this illustrative example, the polymer may be polyacrylonitrile. The filament forms in operation
400 may have a cylindrical shape with a cross-sectional shape that is substantially circular. Thus, the filament may have a single continuous outer surface.
[0070] Next, pressure is applied to the filament to change a cross-sectional shape of the filament and create a plurality of distinct surfaces on the filament (operation
402). In particular, in operation
402, the filament may be flattened. In other words, the cross-sectional shape of the filament may be changed from substantially circular to substantially oval, elliptical, rectangular with rounded corners, or some other type of cross-sectional shape that defines a plurality of distinct surfaces. The plurality of distinct surfaces may be defined by edges that are rounded or sharp, depending on the extent and type of flattening performed in operation 4
02.
[0071] Thereafter, the filament may be converted into a graphitic carbon fiber having the plurality of distinct surfaces (operation
404). Next, a plurality of sizings is applied to the plurality of distinct surfaces of the graphitic carbon fiber (operation
406), with the process terminating thereafter. In operation 4
06, at least two of the distinct surfaces of the graphitic carbon fiber may be coated with two different sizings. In one illustrative example, a different sizing is applied to each distinct surface of the graphitic carbon fiber. For example, without limitation, a first sizing may be applied to a top surface of the graphitic carbon fiber, while a second sizing may be applied to the bottom surface of the graphitic carbon fiber.
[0072] With reference now to
Figure 5, an illustration of a process for manufacturing carbon fibers is depicted in the form of a flowchart in accordance with an illustrative embodiment. The process illustrated in
Figure 5 may be implemented using fiber processing system
104 in
Figure 1 or fiber processing system
200 described in
Figure 2.
[0073] The process may begin by extruding polyacrylonitrile material through a plurality of openings of a die to form a plurality of filaments having a white color (operation
500). In operation
500, the plurality of filaments may also be referred to as a plurality of PAN filaments.
[0074] Next, each filament of the plurality of filaments may be flattened using a roller system to elongate a cross-sectional shape of each filament and create a plurality of distinct surfaces on each filament (operation
502). In operation
502, the cross-sectional shape of each filament may be changed from a substantially circular shape to a substantially oval, elliptical, or rectangular shape with rounded corners. In some illustrative examples, in operation
502, the plurality of filaments may be passed between a first set of rollers and a second set of rollers. The flattening of the plurality of filaments in operation
502 increases the exposed surface area of the plurality of filaments. Further, the flattening of the plurality of filaments creates edges that define a plurality of distinct surfaces. These edges may be rounded or sharp.
[0075] Then, the plurality of filaments may be thermally oxidized (operation 5
04). In operation
504, the plurality of filaments may be thermally oxidized at a lower level of heat than the level of heat needed to carbonize the plurality of filaments. For example, the plurality of filaments may be oxidized at less than about
400 degrees Celsius.
[0076] Thereafter, the plurality of filaments may be converted into a plurality of amorphous carbon fibers having a gray color, with each of the plurality of amorphous carbon fibers having the plurality of distinct surfaces (operation
504). Operation
504 may be performed using a tension system that stretches the plurality of filaments and a heat system that heats the plurality of filaments. In operation
504, the plurality of filaments may be made longer and thinner by the stretching. Stretching the plurality of filaments may cause the various filaments to band together. Flattening the plurality of filaments prior to the stretching enables the plurality of filaments to form a more densely packed band of filaments. In operation 5
04, the plurality of filaments may be heated at a first level of heat selected to carbonize the plurality of filaments and form the plurality of amorphous carbon fibers.
[0077] Next, the plurality of amorphous carbon fibers may be converted into a plurality of graphitic carbon fibers having a black color, with each of the plurality of graphitic carbon fibers having the plurality of distinct surfaces (operation
506). Operation 5
06 may be performed in a manner similar to operation 5
06, but the plurality of amorphous carbon fibers may be heated at a second level of heat that is higher than the first level of heat to cause graphitization.
[0078] Thereafter, a plurality of sizings may be applied to each graphitic carbon fiber of the plurality of graphitic carbon fibers (operation 5
08), with the process terminating thereafter. In operation 5
08, a different sizing may be applied to each different distinct surface of each graphitic carbon fiber. For example, without limitation, a first sizing may be applied to the top surfaces of the plurality of graphitic carbon fibers, while a second sizing may be applied to the bottom surfaces of the plurality of graphitic carbon fibers.
[0079] With reference now to
Figure 6, an illustration of a process for transforming a plurality of filaments into a graphitic carbon fiber is depicted in the form of a flowchart in accordance with an illustrative embodiment. The process illustrated in
Figure 6 may be implemented using fiber processing system
104 in
Figure 1 or fiber processing system
200 described in
Figure 2.
[0080] The process may begin by receiving a filament within a first oven (operation
600). A first level of heat is applied to the filament to transform the filament into an amorphous carbon fiber (operation
602).
[0081] Thereafter, the amorphous carbon fiber is received within a second oven (operation
604). A second level of heat is applied to the amorphous carbon fiber to transform the amorphous carbon fiber into a graphitic carbon fiber, the second level of heat being higher than the first level of heat (operation
606), with the process terminating thereafter.
[0082] With reference now to
Figure 7, an illustration of a process for applying sizings to a graphitic carbon fiber is depicted in the form of a flowchart in accordance with an illustrative embodiment. The process illustrated in
Figure 7 may be implemented using fiber processing system
104 in
Figure 1 or fiber processing system
200 described in
Figure 2.
[0083] The process may begin by applying a first sizing to a first surface of the graphitic carbon fiber using a first surface sizing applicator (operation
700). In operation
700, the first surface sizing applicator may take the form of, for example, without limitation, a sizing application roller, a sizing application spray, a sizing application brush, or some other type of application device that enables the first sizing to be applied to a single surface of the graphitic carbon fiber.
[0084] Next, a second sizing may be applied to a second surface of the graphitic carbon fiber using a second surface sizing applicator (operation
702), with the process terminating thereafter. In operation
702, the second surface sizing applicator may take the form of, for example, without limitation, a sizing application roller, a sizing application spray, a sizing application brush, a chemical bath, or some other type of application device that enables the first sizing to be applied to a different surface of the graphitic carbon fiber, without affecting the first sizing that has already been applied to the graphitic carbon fiber.
[0085] The flowcharts and block diagrams in the different depicted embodiments illustrate the design, architecture, and functionality of some possible implementations of apparatuses and methods in an illustrative embodiment. In this regard, each block in the flowcharts or block diagrams may represent a module, a segment, a function, and/or a portion of an operation or step.
[0086] In some alternative implementations of an illustrative embodiment, the function or functions noted in the blocks may occur out of the order noted in the figures. For example, in some cases, two blocks shown in succession may be executed substantially concurrently, or the blocks may sometimes be performed in the reverse order, depending upon the functionality involved. Also, other blocks may be added in addition to the illustrated blocks in a flowchart or block diagram.
[0087] Illustrative embodiments of the disclosure may be described in the context of aircraft manufacturing and service method
800 as shown in
Figure 8 and aircraft
900 as shown in
9. Turning first to
Figure 8, a flowchart of an aircraft manufacturing and service method is depicted in accordance with an illustrative embodiment. During pre-production, aircraft manufacturing and service method
800 may include specification and design
802 of aircraft
900 in
9 and material procurement
804.
[0088] During production, component and subassembly manufacturing
806 and system integration
808 of aircraft
900 in
9 takes place. Thereafter, aircraft
900 in
Figure 9 may go through certification and delivery
810 in order to be placed in service
812. While in service
812 by a customer, aircraft
900 in
Figure 9 is scheduled for routine maintenance and service
814, which may include modification, repair, refurbishment, and other maintenance or service.
[0089] Each of the processes of aircraft manufacturing and service method
800 may be performed or carried out by a system integrator, a third party, and/or an operator. In these examples, the operator may be a customer. For the purposes of this description, a system integrator may include, without limitation, any number of aircraft manufacturers and major-system subcontractors; a third party may include, without limitation, any number of vendors, subcontractors, and suppliers; and an operator may be an airline, a leasing company, a military entity, a service organization, and so on.
[0090] With reference now to
Figure 9, a block diagram of an aircraft is depicted in which an illustrative embodiment may be implemented. In this example, aircraft
900 is produced by aircraft manufacturing and service method
800 in
Figure 8 and may include airframe
902 with plurality of systems
904 and interior
906. Examples of systems
904 include one or more of propulsion system
908, electrical system
910, hydraulic system
912, and environmental system
914. Any number of other systems may be included. Although an aerospace example is shown, different illustrative embodiments may be applied to other industries, such as the automotive industry.
[0091] Apparatuses and methods embodied herein may be employed during at least one of the stages of aircraft manufacturing and service method
800 in
Figure 8. In particular, fiber processing system
104 described in
Figure 1 and fiber processing system
200 described in
Figure 2 may be used to manufacture carbon fibers
102 during any one of the stages of aircraft manufacturing and service method
800. For example, without limitation, these systems may be used to manufacture carbon fibers
102 for use in the fabrication of composites during at least one of specification and design
802, material procurement
804, component and subassembly manufacturing
806, system integration
808, routine maintenance and service
814, or some other stage of aircraft manufacturing and service method
800. The composites may be used in the assembly of any part of sub-part of aircraft
900, including airframe 9
02 and interior 9
06.
[0092] In one illustrative example, components or subassemblies produced in component and subassembly manufacturing
806 in
Figure 8 may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft
900 is in service
1 in
Figure 8. As yet another example, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during production stages, such as component and subassembly manufacturing
806 and system integration
808 in
Figure 8. One or more apparatus embodiments, method embodiments, or a combination thereof may be utilized while aircraft
900 is in service
812 and/or during maintenance and service
814 in
Figure 8. The use of a number of the different illustrative embodiments may substantially expedite the assembly of and/or reduce the cost of aircraft
900.
[0093] The present invention is also referred to in the following clauses which are not to be confused with the claims.
A1. A method for manufacturing a carbon fiber, the method comprising:
applying (402) pressure (124) to a filament (121) to change a cross-sectional shape (126) of the filament (121) and create a plurality of distinct surfaces (130) on the filament (121) ;
converting (404) the filament (121) into a graphitic carbon fiber (142) having the plurality of distinct surfaces (130); and
applying (406) a plurality of sizings (145) to the plurality of distinct surfaces (130) of the graphitic carbon fiber (142) in which the plurality of sizings (145) includes at least two different sizings.
A2. There is also provided, the method of paragraph A1, wherein applying (402) pressure (124) to the filament (121) comprises:
applying a pressure-forming force to the filament (121) to change the cross-sectional shape (126) of the filament (121) from a substantially circular shape to a flattened shape, thereby creating a top surface (131) and a bottom surface (132) for the filament (121).
A3. There is also provided, the method of paragraph A2, wherein applying (406) the plurality of sizings (145) comprises:
applying a first sizing (144) to a first surface of the graphitic carbon fiber (142); and
applying a second sizing (148) that is different from the first sizing (144) to a second surface of the graphitic carbon fiber (142).
A4. There is also provided, the method of any of paragraphs A1 to A3 further comprising:
extruding a polymer (118) through an opening of an output system (106) to form the filament (121).
A5. There is also provided, the method of paragraph A4, wherein extruding the polymer (118) comprises:
extruding a polyacrylonitrile polymer (122) from the opening of the output system (106) to form the filament (121), wherein the filament (121) has a white color.
A6. There is also provided, the method of any of paragraphs A1 to A5, wherein converting the filament (121) into the graphitic carbon fiber (142) comprises:
tensioning the filament (121) while applying a first level of heat (134) to the filament (121) to form an amorphous carbon fiber (136); and
tensioning the amorphous carbon fiber (136) while applying a second level of heat (140) to the amorphous carbon fiber (136) to form a graphitic carbon fiber (142).
A7. There is also provided, the method of paragraph A6, wherein tensioning the filament (121) comprises:
tensioning the filament (121) while applying a first level of heat (134) to the filament (121) using an oven to form an amorphous carbon fiber (136) having a gray color.
A8. There is also provided, the method of paragraph A7, wherein tensioning the amorphous carbon fiber (136) comprises:
tensioning the amorphous carbon fiber (136) while applying a second level of heat (140) to the amorphous carbon fiber (136) using an oven to form a graphitic carbon fiber (142) having a black color.
A9. There is also provided, the method of any of paragraphs A6 to A8, wherein tensioning the amorphous carbon fiber (136) comprises:
tensioning the amorphous carbon fiber (136) while applying a second level of heat (140) to the amorphous carbon fiber (136) using an oven to form a graphitic carbon fiber (142), wherein a middle interior portion of the graphitic carbon fiber (142) remains amorphous.
A10. There is also provided, the method of any of paragraphs A1 to A9, wherein applying the plurality of sizings (145) comprises:
applying a first sizing (144) to a first surface of the graphitic carbon fiber (142) using a first sizing (144) application roller; and
applying a second sizing (148) to a second surface of the graphitic carbon fiber (142) using a second sizing (148) application roller.
All. There is also provided, the method of any of paragraphs A1 to A10, wherein applying the pressure (124) to the filament (121) comprises:
applying pressure (124) to the filament (121) to change the cross-sectional shape (126) of the filament (121) from substantially circular to one of substantially oval, elliptical, and rectangular with rounded corners, thereby increasing an exposed surface area of the filament (121).
A12. There is also provided, the method of any of paragraphs A1 to All, wherein applying the pressure (124) to the filament (121) reduces a time needed to convert the filament (121) into the graphitic carbon fiber (142).
A13. There is also provided, the method of any of paragraphs A1 to A12, wherein applying the plurality of sizings (145) comprises:
applying a first sizing (144) to a first surface of the graphitic carbon fiber (142) using a sizing application roller (150); and
applying a second sizing (148) to a second surface of the graphitic carbon fiber (142) using a chemical bath (155).
A14. There is also provided, the method of any of paragraphs A1 to A13, wherein applying the plurality of sizings (145) comprises:
applying each sizing of the plurality of sizings (145) to a corresponding distinct surface of the plurality of distinct surfaces (130) of the graphitic carbon fiber (142) using at least one of a sizing application roller (150), a sizing application spray (152), a sizing application brush (154), or a chemical bath (155).
A15. There is also provided, the method of any of paragraphs A1 to A14, wherein applying the plurality of sizings (145) comprises:
applying at least the two different sizings to at least two distinct surfaces (130) simultaneously.
A16. There is also provided, the method of any of paragraphs A1 to A15, wherein applying the plurality of sizings (145) comprises:
applying at least two different sizings to different portions of a distinct surface of the plurality of distinct surfaces (130).
A17. There is also provided, the method of any of paragraphs A1 to A16, wherein applying the plurality of sizings (145) comprises:
applying a sizing to both a first surface and a second surface simultaneously.
A18. A portion of an aircraft assembled according to the method of any of paragraphs A1 to A17.
B1. A method for manufacturing a carbon fiber, the method comprising:
extruding a polyacrylonitrile polymer (122) through a plurality of openings (116) of an output system (106) to form a plurality of filaments (120);
flattening each filament of the plurality of filaments (120) using a roller system (108) to elongate a cross-sectional shape (126) of each filament (121) and create a plurality of distinct surfaces (130) on each filament (121);
converting the plurality of filaments (120) into a plurality of graphitic carbon fibers (142), with each of the plurality of graphitic carbon fibers (142) having the plurality of distinct surfaces (130); and
applying a plurality of sizings (145) to each graphitic carbon fiber (142) of the plurality of graphitic carbon fibers (142) in which the plurality of sizings (145) includes at least two different sizings.
B2. There is also provided, the method of paragraph B1, wherein converting the plurality of filaments (120) into a plurality of graphitic carbon fibers (142) comprises:
heating the plurality of filaments (120) at a first level of heat (134) to form a plurality of amorphous carbon fibers (135); and
heating the plurality of amorphous carbon fibers (135) at a second level of heat (140) to form the plurality of graphitic carbon fibers (142), wherein the second level of heat (140) is higher than the first level of heat (134).
B3. There is also provided, the method of paragraph B2 further comprising:
oxidizing, thermally, the plurality of filaments (120) at a lower level of heat than the first level of heat (134) prior to heating the plurality of filaments (120) at the first level of heat (134).
B4. There is also provided, the method of any of paragraphs B1 to B3, wherein applying the plurality of sizings (145) comprises:
applying a first sizing (144) to a top surface (131) of each of the plurality of graphitic carbon fibers (142); and
applying a second sizing (148) to a bottom surface (132) of each of the plurality of graphitic carbon fibers (142).
B5. There is also provided, the method of any of paragraphs B1 to B4, wherein applying the plurality of sizings (145) comprises:
applying each sizing of the plurality of sizings (145) to a corresponding distinct surface of the plurality of distinct surfaces (130) on each graphitic carbon fiber (142) of the plurality of graphitic carbon fibers (142) using at least one of a sizing application roller (150), a sizing application spray (152), a sizing application brush (154), or a chemical bath (155) .
B6. A portion of an aircraft assembled according to the method of any of paragraphs B1 to B6.
C1. An apparatus comprising:
a roller system (108) for applying pressure (124) to a filament (121) to change a cross-sectional shape (126) of the filament (121) and create a plurality of distinct surfaces (130) ;
a heat system (112) for converting the filament (121) into a graphitic carbon fiber (142); and
a plurality of surface sizing applicators (113) for applying a plurality of sizings (145) to the plurality of distinct surfaces (130) of the graphitic carbon fiber (142) in which the plurality of sizings (145) includes at least two different sizings.
C2. There is also provided, the apparatus of paragraph C1, wherein a surface sizing applicator in the plurality of surface sizing applicators (113) includes at least one of a sizing application roller (150), a sizing application spray (152), a sizing application brush (154), a chemical bath (155).
C3. There is also provided, the apparatus of paragraph C1 or C2 further comprising:
a tension system (110) for tensioning the filament (121) at least one of prior to heating the filament (121), while heating the filament (121), or after heating the filament (121).
C4. There is also provided, the apparatus of any of paragraphs C1 to C3, wherein the plurality of distinct surfaces (130) of the graphitic carbon fiber (142) comprises:
a top surface (131); and
a bottom surface (132).
C5. There is also provided, the apparatus of paragraph C4, wherein the plurality of sizings (145) comprises:
a first sizing (144) to be applied on the top surface (131); and
a second sizing (148) to be applied on the bottom surface (132).
C6. There is also provided, the apparatus of any of paragraphs C1 to C5, wherein the heat system (112) uses a first level of heat (134) to convert the filament (121) into an amorphous carbon fiber (136) and a second level of heat (140) to convert the filament (121) into a graphitic carbon fiber (142).
C7. There is also provided, the apparatus of paragraph C6, wherein the amorphous carbon fiber (136) has a gray color and the graphitic carbon fiber (142) has a black color.
C8. There is also provided, the apparatus of paragraph C6 or C7 wherein a middle interior portion of the graphitic carbon fiber (142) remains amorphous.
C9. There is also provided, the apparatus of any of paragraphs C1 to C8, wherein the filament (121) is comprised of a polyacrylonitrile polymer (122).
C10. There is also provided, the apparatus of any of paragraphs C1 to C9, wherein the roller system (108) comprises at least one roller having a powder coating to protect the filament (121) and to prevent the filament (121) from sticking to the roller system (108).
C11. There is also provided, the apparatus of any of paragraphs C1 to C10, wherein the heat system (112) comprises:
a first oven for heating the filament (121) at a first level of heat (134) to form an amorphous carbon fiber (136); and
a second oven for heating the filament (121) at a second level of heat (140) to form the graphitic carbon fiber (142).
C12. There is also provided, the apparatus of any of paragraphs C1 to C11 further comprising:
an output system (106) having an opening through which a polymer (118) is extruded to form the filament (121).
C13. Fabricating a portion of an aircraft using the apparatus of any of paragraphs C1 to C12.
[0094] The description of the different illustrative embodiments has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different illustrative embodiments may provide different features as compared to other desirable embodiments. The embodiment or embodiments selected are chosen and described in order to best explain the principles of the embodiments, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.