WO2026019455A1 - Fibre de carbone non circulaire pour une résistance à la compression spécifique au coût - Google Patents

Fibre de carbone non circulaire pour une résistance à la compression spécifique au coût

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Publication number
WO2026019455A1
WO2026019455A1 PCT/US2025/019192 US2025019192W WO2026019455A1 WO 2026019455 A1 WO2026019455 A1 WO 2026019455A1 US 2025019192 W US2025019192 W US 2025019192W WO 2026019455 A1 WO2026019455 A1 WO 2026019455A1
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WO
WIPO (PCT)
Prior art keywords
carbon fiber
circular
lobes
fiber
fibers
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/US2025/019192
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English (en)
Inventor
Brandon Lee ENNIS
Robert E. NORRIS, Jr.
Ryan James CLARKE
Ernesto CAMAREN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
National Technology and Engineering Solutions of Sandia LLC
UT Battelle LLC
Original Assignee
National Technology and Engineering Solutions of Sandia LLC
UT Battelle LLC
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Application filed by National Technology and Engineering Solutions of Sandia LLC, UT Battelle LLC filed Critical National Technology and Engineering Solutions of Sandia LLC
Publication of WO2026019455A1 publication Critical patent/WO2026019455A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
    • C08J5/0405—Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres
    • C08J5/042—Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres with carbon fibres
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/06—Fibrous reinforcements only
    • B29C70/10—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/08—Blades for rotors, stators, fans, turbines or the like, e.g. screw propellers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/12—Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/10—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer characterised by a fibrous or filamentary layer reinforced with filaments
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/253—Formation of filaments, threads, or the like with a non-circular cross section; Spinnerette packs therefor

Definitions

  • the present invention is directed to improved carbon fibers.
  • the present invention is directed to optimized non-circular carbon fiber geometries and sizes for use in carbon fiber reinforced polymers.
  • Carbon fiber reinforced polymers are among materials with the highest massspecific strength and stiffness available. When considering its mechanical performance, it is obvious why carbon fiber usage is dominant in many fields. Carbon fiber materials to date have predominantly been developed for optimal tensile performance for use in the aerospace industry. The considerations of mass and cost also drive material selection for wind turbine blades, which are exceeding 100-meters in blade length. Many industries have relied upon the development of improved fiber composite materials. For example, the automotive, aircraft, defense, recreational, container and wind industries have relied upon improvements of strength, flexibility and cost to improve their products. The global commercialization of the wind industry has relied upon, and furthered, the development of composite materials to enable blade mass and cost reductions.
  • the material modulus and compressive strength typically drive the material requirements in the main structural element, the blade spar cap, and not tensile strength.
  • the spar cap component is essentially an internal beam spanning the blade length that provides the majority of the downstream structural resistance to wind loads. Due to the cantilevered nature of wind blades with distributed aerodynamic loads, the spar cap component acts as a beam in bending with similar magnitude compressive and tensile loads on the opposing blade surfaces. The similar maximum compressive and tensile loads combined with the lower compressive resistance of fiber-reinforced polymers results in the compressive strength being the controlling material strength for spar caps.
  • a metric that is useful for material assessment in wind turbine blade spar caps is the costspecific compressive strength, particularly for materials with similar moduli. Increasing the cost-specific compressive strength of carbon fibers having a similar modulus will increase the value of that material for wind turbine spar caps and reduce the system LCOE.
  • the disclosure is directed to optimized fiber geometries for use in carbon fiber reinforced polymers with increased compressive strength per unit cost.
  • the disclosed fiber geometries reduce the material processing costs as well as increase the compressive strength.
  • the disclosed materials include non-circular carbon fiber geometries with lobes.
  • the fibers may include three or more lobes.
  • the fibers may include three, four, six or eight lobes.
  • the lobes (1 ) reduce the diffusion thickness to enable higher throughput and lower costs during production and (2) increase the perimeter and area moment of inertia for a given fiber area.
  • the noncircular lobed carbon fibers also have lower energy costs and emissions during carbon fiber conversion when compared to prior art circular fibers.
  • the non-circular fibers may be used in the automotive, aircraft, defense, recreational, container and wind industries to improve strength, durability and cost.
  • a carbon fiber tow includes a plurality of non-circular carbon fibers.
  • a carbon fiber shape of the non-circular carbon fibers includes extensions in an outer surface to create a lobed geometry.
  • the lobed geometry includes at least three lobes extending from the circumferential core of the non-circular carbon fibers and each of non-circular carbon fibers in the carbon fiber tow has a carbon fiber cross-sectional area equal to or greater than 41 micron 2 (pm 2 ).
  • cross-sectional areas equal to or greater than 41 pm 2 is based on the finding that conversion energy costs and emissions can be reduced by the adoption of non-circular carbon fiber geometries of three, four, six or eight lobes for increased fiber cross-sectional areas equal or to or greater than 41 pm 2 .
  • the non-circular carbon fibers have a cross-sectional area of between 41 pm 2 and 200 pm 2 . In an embodiment, the non-circular carbon fibers have a cross-sectional area of between 41 pm 2 and 140 pm 2 . In another embodiment, the non-circular carbon fibers have a cross-sectional area of between 41 pm 2 and 100 pm 2 . In another embodiment, the non-circular carbon fibers have a cross-sectional area of between 100 m 2 and 140 pm 2 . These cross-sectional areas provide unexpected cost effective compressive structural strength.
  • a carbon fiber composite in another embodiment, includes a matrix material and a plurality of non-circular carbon fibers embedded in the matrix material.
  • the matrix material may be polymers including thermoset, thermoplastic, or vitrimer resin systems. Some common thermoset resins include epoxies, polyolefins, vinylesters, and polyurethanes.
  • the matrix may be carbon or silicon carbide.
  • the matrix may be formed of graphite or carbon nano-particles.
  • the carbon fiber shape of the non-circular carbon fibers includes extensions or lobes in an outer surface to create a lobed geometry.
  • the lobed geometry includes at least three lobes extending from a core of the non-circular carbon fibers.
  • the core may be circumferential.
  • the number of lobes in the non-circular carbon fibers may be three lobes, four lobes, six lobes, or eight lobes.
  • the lobes allow the fibers to have a smaller diffusion thickness per area, higher perimeter per area, and increase the fiber area moment of inertia compared to circular fibers.
  • the lobes can also enhance the composite compressive strength and enable fiber nesting to arrest crack growth and improve damage tolerance of the composite.
  • a structure in another embodiment, includes a plurality of non- circular carbon fibers embedded within the matrix material.
  • the geometry of the non- circular carbon fibers is discussed above.
  • the structure may be but is not limited to wind turbine blades and wind turbine components, automotive structures, recreational equipment, recreational equipment, and related to defense applications.
  • the structure may be a wind turbine blade or a portion of a wind turbine blade.
  • a wind turbine blade is disclosed that includes a carbon fiber composite including a matrix material and a plurality of non-circular carbon fibers as disclosed above embedded within the matrix material.
  • a carbon fiber tow that includes a plurality of non-circular carbon fibers, wherein a carbon fiber shape of the non- circular carbon fibers includes extensions in an outer surface to create a lobed geometry.
  • the lobed geometry is selected from the group consisting of three lobes, four lobes, six lobes and eight lobes extending from a circumferential core of the non-circular carbon fibers and each of the plurality of non-circular carbon fibers in the carbon fiber tow has a carbon fiber cross-sectional area greater than 41 micron 2 .
  • a carbon fiber composite that includes a matrix material and a plurality of non-circular carbon fibers embedded in the matrix material, wherein a carbon fiber shape of the non-circular carbon fibers includes extensions in an outer surface to create a lobed geometry.
  • the lobed geometry is selected from the group consisting of three lobes, four lobes, six lobes and eight lobes extending from a circumferential core of the non-circular carbon fibers and each of the plurality of non-circular carbon fibers in the carbon fiber composite has a carbon fiber cross-sectional area greater than 41 micron 2 .
  • a wind turbine blade includes a carbon fiber composite comprising a matrix material and a plurality of non-circular carbon fibers embedded within the matrix material.
  • the carbon fiber shape of the non-circular carbon fibers includes extensions in an outer surface to create a lobed geometry and the lobed geometry is selected from the group consisting of three, four, six and eight lobes extending from a circumferential core of the non-circular carbon fibers.
  • Each of the plurality of non-circular carbon fibers in the carbon fiber composite has a carbon fiber cross-sectional area greater than 41 micron 2 .
  • FIG.1 illustrates a wind turbine according to an embodiment of the invention.
  • FIG. 2 shows normalized fitness values as a proxy for cost-specific compressive performance versus the number of lobes according to an embodiment of the disclosure.
  • FIG. 3A illustrates the cross-sectional geometry of a three lobe carbon fiber geometry according to an embodiment of the disclosure.
  • FIG. 3B illustrates the cross-sectional geometry of a four lobe carbon fiber geometry according to an embodiment of the disclosure.
  • FIG. 3C illustrates the cross-sectional geometry of a six lobe carbon fiber geometry with alternating lobe length/height according to an embodiment of the disclosure.
  • FIG. 3D illustrates the cross-sectional geometry of an eight lobe carbon fiber geometry with alternating lobe length/height according to an embodiment of the disclosure.
  • FIG. 4 shows performance parameters of the exemplary geometries from FIGS. 3A-3D relative to a circular fiber having the same cross-sectional area according to an embodiment of the disclosure.
  • FIG. 5 illustrates an exemplary fiber packing arrangement of multiple three lobe carbon fiber geometries in a composite.
  • FIG. 6 is a plot of compressive strength test averages versus effective fiber diameter for two distinct precursor systems (Dolan and Kaltex) in two composite test forms (unidirectional [0] and cross-ply [0/90]). This figure illustrates a positive correlation between increased fiber size and/or area moment of inertia and improved compressive strength.
  • FIG. 7A shows numerical predictions of compressive strength for a fiber diameter of 7.2 microns and a fiber that has twice the diameter of 14.4 microns as a function of initial fiber misalignment angle.
  • FIG. 7B is a plot of the compressive strength percent difference of the larger diameter fiber based on predictions in FIG. 7A with improvements of 2.5% to 4.5%. The numerical results for improvement in compressive strength with fiber size underpredict the trends observed from the test results in FIG. 6.
  • FIG. 8A is a plot of the fiber area moment of inertia variation with fiber cross- sectional area to compare a circular fiber with the exemplary three lobe and exemplary six lobe fibers from FIG. 3A and 3C, revealing the improvement in this property for the non-circular fibers.
  • FIG. 8B is a plot of the fiber perimeter divided by its area variation with fiber cross- sectional area to compare a circular fiber with the exemplary three lobe and exemplary six lobe fibers from FIG. 3A and 3C, revealing the improvement in this property for the non-circular fibers.
  • the interfacial area for a fiber is the product of the fiber perimeter and its length.
  • this figure illustrates that the total interfacial area in the composite is decreased as fibers of any specific geometry are increased in size.
  • the non-circular fibers enable the same or higher total interfacial area in a composite while using fibers with larger cross-sectional areas (horizontal dashed line as a reference).
  • FIG. 8C is a plot of the fiber diffusion thickness during oxidation variation with fiber cross-sectional area to compare a circular fiber with the exemplary three lobe and exemplary six lobe fibers from FIG. 3A and 3C, revealing the improvement in this property for the non-circular fibers. Reducing the diffusion thickness reduces the required residence time during the oxidation stage of carbon fiber conversion (FIG. 9).
  • the non- circular fibers enable the same or lower diffusion thickness while using fibers with larger cross-sectional areas (horizontal dashed line as a reference).
  • FIG. 8D is a plot of the required residence time during oxidation variation with fiber cross-sectional area to compare a circular fiber with the exemplary three lobe and exemplary six lobe fibers from FIG. 3A and 3C, revealing the improvement in this property for the non-circular fibers. Reducing the required residence time during the oxidation stage of carbon fiber conversion (FIG. 9) increases production throughput and reduce carbon fiber costs.
  • FIG. 9 illustrates the major sequential steps in carbon fiber conversion as used in the cost model to predict cost trends with carbon fiber geometry.
  • FIG. 10 is a plot of the carbon fiber material cost estimates as a function of fiber diffusion thickness and cross-sectional area.
  • Non-circular fiber geometries have lower diffusion thickness values and follow distinct lines within the sampled space. The cost curves are shown for the exemplary three lobe and exemplary six lobe fibers from FIG. 3A and 3C relative to a circular fiber (having the highest possible diffusion thickness for a given area representing the upper bound in this plot).
  • FIG. 11 is a plot of the carbon fiber material cost versus the fiber cross-sectional area for the exemplary profiles from FIG. 3 compared with a circular fiber. The diamond markers reveal the numerical minimum of each shape’s cost curve. It is apparent from this figure that the non-circular geometries reduce the cost relative to circular geometries while also enabling the cost-effectiveness of carbon fibers with large cross-sectional areas.
  • FIG. 12 is a plot of the energy costs during carbon fiber conversion versus the fiber cross-sectional area for the exemplary profiles from FIG. 3 compared with a circular fiber.
  • the diamond markers reveal the numerical minimum of each shape’s cost curve.
  • the energy costs have associated emissions, and the figure illustrates how the noncircular carbon fiber geometries can have reduced energy costs and associated emissions beyond 41 pm 2 carbon fiber cross-sectional areas whereas the quantities increase beyond this value for circular fibers.
  • the invention includes carbon fiber cross-sectional shapes for carbon fiber reinforced polymers that provide cost-specific compressive strength of a carbon fiber composite structure.
  • the carbon fiber composite is used in wind turbine blades.
  • the disclosed carbon fiber shapes include extensions that extend away from a circumferential core of the carbon fiber to create lobed geometries.
  • the disclosed carbon fiber shapes include a periodic oscillation in their outer surface to create the lobed geometries.
  • the extensions that create the lobed geometries include lobes that are all the same size, alternating sized lobes or lobes of multiple varying sizes. These carbon fiber shapes are also described as “lobed noncircular carbon fibers” herein.
  • the carbon fiber composites disclosed herein have lobed non-circular carbon fibers embedded in a polymer matrix. The composite has improved compressive strength compared to prior art circular carbon fibers.
  • lobes are extensions that extend away from a circumferential core of the carbon fiber.
  • the “circumferential core”, as defined herein, is the central portion of the carbon fiber. While the circumferential core is shown as circular herein, other shapes, such as squares, triangles, or ovals, are within the scope of the current invention.
  • lobes are perturbations of material extending away from the circumferential core.
  • the minimum lobe height of each lobe is at least 10% of the diameter of the circumferential core of the noncircular carbon fiber.
  • a lobed geometry includes a plurality of lobes.
  • the carbon fiber composite disclosed herein includes large diameter lobed noncircular fibers that increase compressive strength while also being cost effective compared to prior art circular carbon fibers. Lobed non-circular carbon fibers have a higher area moment of inertia at a much lower cost than circular carbon fibers. This also allows the carbon fibers to be straighter, with less misalignment than prior art circular carbon fibers.
  • Composites including the lobed non-circular fibers disclosed herein may be interlocking, resulting in better damage tolerance than circular carbon fibers. Water absorption is also slowed down, so degradation decreases with lobed non-circular fibers in certain applications especially where water absorption is prevalent. Lobed non-circular fibers also have lower emissions than circular carbon fibers with the same cross-sectional area.
  • the non-circular carbon fibers with extensions in their outer surface have at least three lobes. Any of the lobes in the non-circular carbon fibers may have the same or different amplitude than other lobes in the same non-circular carbon fiber.
  • the non-circular carbon fibers with extensions in their outer surface have three, four, six or eight lobes.
  • the lobes in the three- lobe embodiment are all the same and equidistant from each other. In other embodiments, the lobes may not be equidistant from each other. In other embodiments, the three lobes may all have a different amplitude, or one of the three lobes may have a different amplitude than the other two lobes.
  • the lobes in the four-lobe embodiments are equidistant from each other and may either be all the same or alternating in height/length such that there are two sets of two different sized lobes. In some embodiments, the angular orientation of the lobes could be symmetric or variable (for each geometry).
  • the lobes in the six-lobe and eight lobe embodiments are equidistant from each other and preferably each include two lobe types, each of a different height/length, which alternate with each other.
  • the lobes in the six- lobe or eight-lobe embodiments all have the same height/length.
  • the alternating lobes in the four, six or eight lobe embodiments have variable amplitude (height/length).
  • the non-circular carbon fibers are used in turbine blade structures.
  • the invention includes carbon fiber composites including the non-circular carbon fibers described herein within a matrix.
  • the composite may be made of unidirectional carbon fibers, multi-axial carbon fibers, or a combination of unidirectional carbon fiber and multi-axial carbon fiber.
  • the unidirectional carbon fibers and multi-axial carbon fibers may be continuous carbon fibers with a long length or discontinuous carbon fibers with a short length.
  • the non-circular carbon fibers may all have the same non-circular shapes, or the non-circular carbon fibers within the matrix (or within a carbon fiber tow) may have more than one of the non-circular carbon fiber shapes disclosed herein.
  • tows formed of the disclosed carbon fibers may include multiple fiber types in one fiber-reinforced polymer (FRP) composite.
  • FRP fiber-reinforced polymer
  • carbon fiber composites include long length, continuous lobe-shaped non-circular carbon fibers aligned in the same direction. In other embodiments, the carbon fiber composites include long length, continuous lobe-shaped non-circular carbon fibers aligned in two or more directions. In other embodiments, the carbon fiber composites include short length, discontinuous lobe-shaped non-circular carbon fibers aligned in one or more directions or aligned randomly. [0051]
  • the lobe-shaped carbon fibers described herein have a combination of a larger area moment of inertia and perimeter at a given cross-sectional area than conventional circular carbon fibers and produce a higher composite compressive strength. Compressive strength of carbon fiber composites can be further increased with carbon fiber size.
  • the lobe-shaped carbon fibers described herein also are significantly more cost effective than circular carbon fibers at higher carbon fiber areas (pm 2 ).
  • the three lobe and six lobe carbon fibers described herein have lower carbon fiber conversion costs than conventional circular carbon fibers, and larger three-lobe and six-lobe carbon fibers are not cost-prohibitive, unlike the costs for larger conventional circular carbon fibers.
  • Three- lobe and six-lobe carbon fibers result in manufacturing cost improvements and promising fiber packing.
  • the non-circular carbon fibers have a cross-sectional area of between 41 pm 2 and 200 pm 2 . In an embodiment, the non-circular carbon fibers have a cross-sectional area of between 41 pm 2 and 140 pm 2 . In another embodiment, the non-circular carbon fibers have a cross-sectional area of between 41 pm 2 and 100 pm 2 . In another embodiment, the non-circular carbon fibers have a cross-sectional area of between 60 pm 2 and 140 pm 2 . These cross-sectional areas provide unexpected cost effective compressive structural strength for three, four, six and eight lobe non-circular cross-sectional carbon fibers.
  • the carbon fiber tow count is greater than or equal to 6 k. In other embodiments, the carbon fiber tow counts are greater than or equal to 24 k. In other embodiments, the carbon fiber tow counts are greater than or equal to 50 k. In some embodiments, the carbon fiber tow count may be as between 50 k and 475 k.
  • Non-circular fibers produce an opportunity to realize the compressive strength improvements of larger carbon fibers without the negative cost consequences of using circular fibers. This is accomplished through reducing the diffusion thickness parameter when using non-circular fibers.
  • the non-circular carbon fibers with carbon fiber areas between 41 pm 2 and 200 pm 2 disclosed herein have decreased energy costs during carbon fiber conversion. There is an unexpected trend where the energy cost decreases as the carbon fiber area increases forthree-lobed, four-lobed, six-lobed and eight-lobed non-circular carbon fibers. Other energy related parameters, for example emissions, are also decreased as the carbon fiber area increases for three-lobed, four-lobed, six-lobed and eight-lobed non- circular carbon fibers.
  • FIG. 1 illustrates a wind turbine 100 according to an embodiment of the disclosure.
  • the wind turbine 100 includes three wind turbine blades 101 attached to a nacelle 103 or hub, which is attached to a tower 105. While FIG. 1 shows three blades 101 , any suitable number of blades 101 , such as, but not limited to two, four or five blades 101 may be used. It should be noted that FIG. 1 is not drawn to scale.
  • the wind turbine blades 101 include a matrix of lobed non-circular carbon fibers, the cross-sections of various embodiments of which are shown in FIGS. 3A-3D (see discussion of FIGS 3A-3D below).
  • the matrix includes a plurality of three-lobed non-circular carbon fibers, four-lobed non-circular carbon fibers, six-lobed non-circular carbon fibers or eight-lobed non-circular carbon fibers.
  • the non-circular carbon fibers have a cross-sectional area of between 41 pm 2 and 200 pm 2 . In an embodiment, the non-circular carbon fibers have a cross-sectional area of between 41 pm 2 and 140 pm 2 . In another embodiment, the non-circular carbon fibers have a cross-sectional area of between 41 pm 2 and 100 pm 2 . In another embodiment, the non-circular carbon fibers have a cross-sectional area of between 100 pm 2 and 140 pm 2 . These cross-sectional areas provide unexpected cost effective compressive structural strength for three, four, six and eight lobe non-circular cross-sectional carbon fibers.
  • the non-circular cross-sectional fiber shapes disclosed herein have been found to provide the highest fitness performance. If the fiber packing factor constraint is ignored, only two fitness factors were considered (normalized by fiber production costs). Fitness 1 only cares about the area moment of inertia. Fitness Values combines weights the area moment of inertia and the fiber perimeter. The disclosed fibers provide for effective area moment of inertia for fitness function (which does not penalize for fiber packing factor).
  • FIG. 2 shows the distribution of fitness results when using the penalized FPF approach with a 68% target.
  • the best performing shapes when penalizing FPF calculations have three, four, six, or eight lobes. Shapes with five, seven, and nine lobes do not perform as well due to the lower fiber packing factor values that must fit within the circular geometrical element which does not have an idealized perfect packing.
  • FIG. 2 illustrates this trend where five, seven, and nine lobe shapes always have a lower area moment of inertia for a given maximum fiber packing factor.
  • the normalized performance “fitness” values are highest for shapes with a high cost-specific area moment of inertia.
  • the optimal shapes are those that move the most area furthest from the shape center.
  • Fitness 1 values are therefore highest for shapes with an even number of lobes where the alternating peaks are removed R to 0 as these shapes can have long, narrow lobes.
  • Calculating the fitness objective functions using the minimum area moment of inertia compared to the effective area moment of inertia removes the Fitness 1 peak for two- lobed shapes due to the asymmetric area moment of inertia of these shapes with asymmetric lobe heights.
  • the Fitness 2 values include the effect of shape perimeter in estimating compressive strength of the composite. Based on this approach, there is nearly a direct correlation between number of lobes and shape fitness performance as the higher-lobed shapes have associated higher perimeters.
  • FIGS. 3A-3D show dimensions for exemplary 3, 4, 6 and 8 lobe fibers. These exemplary fibers with these numbers of lobes have shown the best performance for increasing fiber area moment of inertia and perimeter at reduced costs relative to circular fibers while enabling efficient fiber packing arrangements to yield high fiber volume fraction composites.
  • the three-lobe (see FIG. 3A) and six-lobe (see FIG. 3C) shapes are the best performers. If there is nesting of the fiber lobes for the fiber packing factor estimate, the two-lobe shape or another shape may be a better performer if they nest properly.
  • FIG. 4 shows various performance metrics for non-circular carbon fiber geometries with three, four, six, and eight lobes compared with a circular fiber of the same cross- sectional area.
  • the values are normalized to those for the reference 7.2 micron diameter circle to illustrate why they are optimal over a circular fiber with the same cross-sectional area.
  • Each of the shapes have a higher area moment of inertia and perimeter compared to the circle, and a lower cost (because of the shorter diffusion pathway for oxidation).
  • the six-lobe and eight-lobe shapes both have the highest perimeter (FIG. 4) meaning these shapes would be more optimal if the composite compressive strength is more correlated to the interfacial area than was assumed.
  • the three-lobe and four-lobe shapes have the lowest cost, but also have lower area moments of inertia than the six- lobe (FIG. 4) shape.
  • the eight-lobe (FIG. 4) shape would perform higher overall but does not achieve the fiber packing factor target and is penalized at the idealized prediction.
  • the three and six lobe fibers Compared to the circular fiber, the three and six lobe fibers have a 50-60% higher area moment of inertia, 40-80% increased perimeter, and a 30% reduction in the fiber cost (see FIG. 4).
  • Optimal fiber shapes have been identified as those with the greatest potential to maximize the cost-specific compressive strength of carbon fiber composites based on the analysis approach within the previous section.
  • the selected optimal shapes focus primarily on fitness functions which penalize based on fiber packing factor predictions. These two fitness calculations are considered the most relevant for wind turbine blades due to the importance of the fiber volume fraction at reducing blade weight and cost.
  • Unknowns in the objective formulation prevent a singular optimal shape from being identified by this analysis. These unknowns include the area moment of inertia that drives composite performance, minimum or effective, as well as the quantitative relationship between the fiber-resin interfacial area and resulting compressive strength.
  • FIG. 3A shows a three-lobed carbon fiber geometry.
  • the three-lobed fibers include three lobes 310 equidistant from each other and having the same shape and amplitude (height/length).
  • FIG. 3B shows a four-lobed geometry, where the lobes 320 are all the same length. While three-lobed shapes and six-lobed shapes perform best for higher fiber volumes in applications like wind turbine blades, in applications where the user wants a lower fiber volume fraction, the four-lobed shapes with all the same size lobes or alternating lobes may perform better.
  • FIG. 3C shows an alternating six-lobed carbon fiber geometry.
  • the alternating lobes have variable amplitude (height/length).
  • the alternating six-lobed carbon fiber geometry includes three lobes 330 and three lobes 340 having a different length than the three lobes 330.
  • the lobes alternate around a circumferential core of the six-lobed carbon fiber.
  • FIG. 3D shows an alternating eight-lobed carbon fiber geometry.
  • the alternating eight-lobed carbon fiber geometry includes four lobes 350 and four lobes 360 having a different length than the four lobes 350.
  • the lobes alternate around a circumferential core of the eight-lobed carbon fiber.
  • the three-lobe shape (FIG. 3A) does not depend on the effective area moment of inertia and performs comparably regardless of including perimeter effects or not in the fitness calculation. This shape also has thicker lobes which benefit the qualitative considerations related to manufacturing, resin wetting, and lobe durability. Additionally, it is considered the most likely to achieve its fiber packing factor estimate due to the I ikelihood of adjacent fibers nesting well between lobes.
  • FIG. 5 illustrates an exemplary fiber packing arrangement considered for the three lobe shape. Oftentimes, the fiber volume fraction controls what the base-shape is. A fiber volume fraction 0.68 was targeted for all shapes and all fiber packing arrangements.
  • the area of the generated shape is normalized to the baseline fiber by the variable h.
  • the three-lobe and six-lobe fibers are predicted with compressive strength increases of 6-10% for a reference fiber alignment distribution.
  • the increased area moment of inertia for the non-circular carbon fiber geometries is hypothesized to relate to improved fiber alignment.
  • the sensitivity of these improvements is calculated for a 10% improvement in fiber alignment (as quantified by the standard deviation of the fiber angle distribution) which increases the compressive strength improvement to 10-14%.
  • the longitudinal compressive strength of unidirectional composites can be improved using non-circular fibers including, but not limited to, six-lobe and three-lobe shaped carbon fibers. These non-circular fibers also provide cost reductions on the order of 30%.
  • the three-lobe and six-lobe fibers have a 52% and 62% increase in the area moments of inertia relative to a circular fiber of the same cross-sectional area. This increased area moment of inertia results in a higher bending resistance and may contribute to reduced fiber waviness and improved alignment during composite manufacturing.
  • Non-circular fibers can reduce manufacturing costs by up to 30%.
  • the results herein show that six-lobed fibers can improve strength from 10% to 13% and three-lobed fibers can be 6% to 9% stronger than circular fibers. These strength improvements can be further augmented with increased fiber alignment resulting from the lobed non-circular carbon fibers with higher area moments of inertia and bending resistance.
  • FIG. 6 shows that carbon fiber systems with increasing size illustrate a favorable correlation for compressive performance, which is not predicted from a micromechanical failure model (FIG. 7A and FIG. 7B).
  • the manufacturing and mechanical test results show that alterations to fiber geometry can be used to produce improvements of the compressive strength of carbon fiber reinforced polymers.
  • Non-circular carbon fiber geometries such as multi-lobed geometries or asymmetric fibers.
  • Non-circular carbon fibers enable increases in the fiber area moment of inertia while maintaining diffusion thicknesses in ranges like those for commercial fibers, resulting in similar production line speeds.
  • the non-circular geometry also increases the wetted perimeter of the fiber over more circular fibers having the same total cross-sectional area, thereby potentially providing opportunity to increase interfacial adhesion.
  • Non-circular carbon fiber materials for cost-driven industries permit the opportunity to reduce the processing costs and increase compressive strength.
  • Examples of non- circular carbon fiber geometries are discussed herein and shown in FIGS. 3A-3D. These geometries relate to composite compressive strength and decreasing the carbon conversion costs. More specifically, these geometries offer enhancements in cost- effective compressive strength of carbon fiber composites.
  • This invention determines and evaluates the relationship between carbon fiber size or, more broadly, the shape area moment of inertia to compressive strength and material cost to identify optimal carbon fiber sizes and geometries for fiber reinforced polymer composites in wind turbine blades and other applications.
  • One textile acrylic fiber is a fiber product manufactured by Kaltex which is produced in very large tows of 457,000 filaments.
  • the wet spinning process employed by Kaltex naturally yields a fiber that is highly non-circular and frequently characterized as a “kidney bean” shape.
  • the Kaltex fibers were also included in the fiber size comparison in FIG. 6.
  • Carbon fiber geometries with higher area moments of inertia can increase compressive performance. These materials are all based on polyacrylonitrile (PAN) precursors.
  • PAN polyacrylonitrile
  • the commercial baseline carbon fiber systems were tested to provide a set of known references for the experimental carbon fiber systems.
  • the set of textile acrylic fiber systems from suppliers Dolan and Kaltex were used to assess the impact of varying the size of the carbon fiber within consistent precursor systems.
  • the compressive test data are presented in FIG. 6 for the unidirectional [0] coupon tests as well as the cross-ply [0/90] coupon tests using the backout factor from Equation 11 .
  • the unidirectional compressive strength data are normalized to a 60% fiber volume fraction for a more direct comparison according to Equation 12. While the compressive strength is not perfectly linear with fiber volume fraction, this estimation is appropriate for the minor variations in fiber volume fraction associated with the test data.
  • model parameters were taken from Camarena et al., Development of a compressive failure model for carbon fiber composites and associated uncertainties, 2021 , herein incorporated by reference in its entirety.
  • FIG. 7A The compressive strength prediction as a function of initial fiber misalignment for the reference and increased diameter fibers are shown in FIG. 7A.
  • the larger diameter fiber is predicted to outperform the baseline, however, with only a 2.5% to 4.5% increase in compressive strength for initial misalignments up to 3 degrees for the larger fiber as seen in FIG. 7B.
  • the textile-grade carbon fiber systems show that there is a correlation between compressive strength and fiber size. This was observed across two precursor systems with somewhat circular and kidney-bean shape fibers. It is considered this relationship is primarily driven by increases in fiber area moment of inertia. Increasing carbon fiber size for circular carbon fibers is cost-prohibitive. However, since lobed fiber shapes can increase area moment of inertia without increases in cross-sectional area, these shapes are beneficial for cost-effective non-circular carbon fibers.
  • the cost of carbon fiber has a strong dependency on the conversion processing speed which is limited by the required oxidation time for the precursor, related to the radius (diffusion thickness of the precursor fibers) to a power between 1.5 to 2.
  • the required oxidation time for the precursor related to the radius (diffusion thickness of the precursor fibers) to a power between 1.5 to 2.
  • Alternative shapes enable variation from these fixed relationships.
  • FIG. 8A shows a graph of fiber geometry and processing trends for circular 1 , three-lobe 10 and six-lobe 14 carbon fibers, the shapes of which are shown in FIGS. 3A and 3C, respectively.
  • the perimeter per area is lower for the circular fiber than both the three-lobe (FIG. 3A) and six-lobe (FIG. 3C) fibers.
  • FIG. 8D shows that the oxidation residence time for the circular fibers increases significantly as carbon fiber area increase for the circular fiber. While the residence time also increases for the three- lobe and six-lobe fibers, it increases at a much slower rate for both of these non-circular fiber shapes.
  • FIG. 8A shows the area moment of inertia (microns 4 ) versus carbon fiber area for circular carbon fibers, three-lobed carbon fibers (FIG. 3A) and six-lobed carbon fibers (FIG. 3C).
  • the area moment of inertia is higher for both the three-lobe and six-lobe fibers compared to the circular fiber.
  • the larger cross-sectional area produces an even larger area moment of inertia for the three-lobe and six-lobe non- circular carbon fiber shapes, producing compounding benefits for improved fiber alignment in composites and increased compressive strength.
  • FIG. 8C shows diffusion thickness (microns) versus carbon fiber area.
  • the diffusion thickness is the geometry characteristic that controls the required oxidation residence time.
  • the lower diffusion thickness of the three-lobe and six-lobe shapes enables higher throughput and resulting lower cost.
  • Cost modeling was performed for circular fibers, three-lobed non-circular fibers (FIG. 3A) and six-lobed non-circular fibers (FIG. 3C).
  • the cost modeling considered raw materials, precursor manufacturing, and carbon fiber conversion.
  • the cost of converting the PAN-based precursor to carbon fiber is estimated using a carbon fiber conversion cost model.
  • the cost model accounts for the capital, labor, energy, and material costs according to the major process steps depicted in FIG. 9.
  • the process steps include precursor, pre-treatment, oxidation, low temperature carbonization furnace (LT), high temperature carbonization furnace (HT), surface treatment, sizing, and post-processing steps (winding, inspection, and shipping). Effluent occurs during the oxidation, LT, and HT steps. The effluent is dealt with during abatement.
  • the baseline conversion cost model assumptions represent a $58MM installed capital costs with a 15-year life expectancy, a 3 m roller width, 810 m of heated oxidation furnace length, continuous operation with a plant availability of 82%, and a mechanical yield of 95% and chemical yield of 48%. Additional assumptions and commercial reference cost estimation values used for calibration in this analysis are provided in Ennis et al., Optimized carbon fiber composites in wind turbine blade design. Technical Report (SAND2019-14173), Sandia National Laboratories, November 2019, herein incorporated by reference in its entirety.
  • the carbon fiber cost model is used to estimate the conversion costs for variable carbon fiber geometry and tow specifications. Carbon fiber throughput is controlled by the required residence time during oxidation. For the baseline commercialgrade carbon fiber, the oxidation time is estimated at 90 min compared of 1 .5 min for the low temperature (LT) and high temperature (HT) carbonization furnaces. Based on this convention, the time during oxidation is treated as the rate controlling stage for carbon fiber production in the model assuming a fixed oxidation furnace length of 810 m. The required oxidation residence time is related the fiber diffusion thickness according to Equation 16. The line speed during conversion is then calculated as the heated length in the oxidation furnace divided by required residence time. The length of the LT and HT furnaces are then modified for this line speed assuming a fixed requirement of 90 sec residence time, independent of the variable carbon fiber specifications. 6.23 X t diffusion (16)
  • the resulting carbon fiber cost is the summation of conversion costs and precursor costs as shown in Equation 22. Precursor cost contributions were estimated at 45% of carbon fiber costs for a commercial-grade, PAN-based carbon fiber where processing yields require 2.2 kg of precursor for every 1 kg of carbon fiber.
  • FIG. 10 shows total carbon fiber costs [USD/kg], including precursor costs, for a 50 k tow count.
  • the circular reference fiber 1 is approximately 40 pm 2 and is shown by the O in the figure.
  • the six-lobe carbon fiber (FIG. 3C) is shown a short-long dashed line, while the three- lobe carbon fiber (FIG. 3A) is shown as a constant dashed line.
  • both the three lobed and six lobed carbon fiber shapes have a significantly lower cost than the circular fibers.
  • FIG. 11 shows a summary of the carbon fiber costs for 50 k tow counts, including precursor costs, for the circular prior art fibers, the three-lobed fibers (FIG. 3A) and the six-lobed fibers (FIG. 3C), as well as the carbon fiber costs at 50k tow count for the four-lobed (FIG. 3B) and eight-lobed (FIG. 3D) carbon fibers. While 40 pm 2 is used as the reference circular fiber area (Zoltek PX-35, 50K tow), this is considered large in the industry.
  • the energy costs during carbon conversion for three- lobed, six-lobed, eight-lobed and four-lobed carbon fibers are significantly lower than the carbon fiber costs for circular carbon fibers for all carbon fiber areas at a 50 k tow count.
  • Minimum emission levels occur at higher cross-sectional areas for the multi-lobed carbon fibers, with numerical minima shown by the black markers for each shape. Consequently, there is a lower energy demand during carbon fiber production for the lobed geometries. This reduces the cost and associated production emissions.
  • Three-lobed carbon fibers have a carbon fiber area greater than 40 pm 2 in one embodiment of the invention. In other embodiments of the invention, three-lobed carbon fibers have a carbon fiber area greater than or equal to 41 pm 2 and equal to or less than 200 pm 2 . In another embodiment, three-lobed carbon fibers have a carbon fiber area of at least 50 pm 2 . Three-lobed carbon fibers have a carbon fiber area of at least 60 pm 2 in one embodiment of this invention. Three-lobed carbon fibers have a carbon fiber area of at least 80 pm 2 in another embodiment of this invention. Three-lobed carbon fibers have a carbon fiber area of at least 100 pm 2 in another embodiment of this invention. Three-lobed carbon fibers have a carbon fiber area of at least 140 pm 2 in another embodiment of this invention. These sizes provide cost effective compressive strength and reduced energy costs and emissions for the non-circular carbon fibers.
  • Six-lobed carbon fibers have a carbon fiber area greater than 40 pm 2 in one embodiment of the invention. In other embodiments of the invention, six-lobed carbon fibers have a carbon fiber area equal to 41 pm 2 and equal to or less than 200 pm 2 . In another embodiment, six-lobed carbon fibers have a carbon fiber area of at least 50 pm 2 . Six-lobed carbon fibers have a carbon fiber area of at least 60 pm 2 in one embodiment of this invention. Six-lobed carbon fibers have a carbon fiber area of at least 80 pm 2 in another embodiment of this invention. Six-lobed carbon fibers have a carbon fiber area of at least 100 pm 2 in another embodiment of this invention. Six-lobed carbon fibers have a carbon fiber area of at least 140 pm 2 in another embodiment of this invention. These sizes provide cost effective compressive strength and reduced energy costs and emissions for the non-circular carbon fibers.

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Abstract

Pour l'énergie éolienne et d'autres industries axées sur les coûts, le coût des matériaux en fibre de carbone est souvent prohibitif pour son adoption et la résistance à la compression est un facteur presque aussi important que la résistance à la traction. Des géométries de fibres de carbone non circulaires optimisées destinées à être utilisées dans des polymères renforcés par des fibres de carbone ont été développées pour augmenter la résistance à la compression par coût unitaire. Des analyses ont été effectuées pour identifier des géométries de fibres qui ont été montrées réduire les coûts de traitement de matériau ainsi qu'augmenter la résistance à la compression. Ces études ont identifié des géométries de fibres de carbone non circulaires comportant trois lobes ou plus qui (1) réduisent l'épaisseur de diffusion afin d'augmenter le débit et de réduire les coûts pendant la production et (2) augmentent le périmètre et le moment d'inertie de surface pour une surface de fibre donnée. Des composites utilisant des géométries de fibres de carbone non circulaires à lobes avec une aire en coupe transversale de fibre de carbone supérieure à 41 microns2 offrent des alternatives économiques tout en augmentant également la résistance à la compression.
PCT/US2025/019192 2024-07-16 2025-03-10 Fibre de carbone non circulaire pour une résistance à la compression spécifique au coût Pending WO2026019455A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5154908A (en) * 1985-09-12 1992-10-13 Clemson University Carbon fibers and method for producing same
US5910456A (en) * 1995-01-09 1999-06-08 Toray Industries, Inc. Prepregs and carbon fiber-reinforced composite materials
US20070128404A1 (en) * 2005-12-06 2007-06-07 Invista North America S.Ar.L. Hexalobal cross-section filaments with three major lobes and three minor lobes
US20180346668A1 (en) * 2015-03-06 2018-12-06 Toray Industries, Inc. Sizing agent coated carbon fiber, method for producing sizing agent coated carbon fiber, carbon fiber reinforced composite material, and method for producing carbon fiber reinforced composite material
US20200283932A1 (en) * 2019-03-04 2020-09-10 University Of Kentucky Research Foundation Method of making polyacrylonitrile based carbon fibers and polyacrylonitrile based carbon fiber fabric

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5154908A (en) * 1985-09-12 1992-10-13 Clemson University Carbon fibers and method for producing same
US5910456A (en) * 1995-01-09 1999-06-08 Toray Industries, Inc. Prepregs and carbon fiber-reinforced composite materials
US20070128404A1 (en) * 2005-12-06 2007-06-07 Invista North America S.Ar.L. Hexalobal cross-section filaments with three major lobes and three minor lobes
US20180346668A1 (en) * 2015-03-06 2018-12-06 Toray Industries, Inc. Sizing agent coated carbon fiber, method for producing sizing agent coated carbon fiber, carbon fiber reinforced composite material, and method for producing carbon fiber reinforced composite material
US20200283932A1 (en) * 2019-03-04 2020-09-10 University Of Kentucky Research Foundation Method of making polyacrylonitrile based carbon fibers and polyacrylonitrile based carbon fiber fabric

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