Wind turbine blades with cellular structures and methods for manufacturing wind turbine blades using cellular structures

Abstract

A wind turbine blade (24) of a wind turbine (12) including a shell (36) having a sidewall (40). The sidewall (40) including an outer skin (50) of a first composite, an inner skin (52) of a second composite, a cellular structure (56) including a plurality of walls (70) defining a plurality of cells (76). The cellular structure (56), including an outer wall (90), an inner wall (80), and a mid portion (98), between the outer skin (50) and the inner skin (52). A first composite layer (96) including the outer wall (90) and a matrix (94) of the first composite. A second composite layer (86) including the inner wall (80) and a matrix (84) of the second composite. Cells (76) in the mid portion (98) of the cellular structure (56) are closed cells. A method for manufacturing a wind turbine blade (24) including admitting a resin (130) to impregnate into fiber layers (110, 114). The resin (130) penetrates the cellular structure (56) to form composite layers (86, 96).

Description

[0001] WIND TURBINE BLADES WITH CELLULAR STRUCTURES AND METHODS FOR MANUFACTURING WIND TURBINE BLADES USING CELLULAR STRUCTURES

[0002] Technical Field

[0003] This application relates generally to wind turbines, and more particularly, relates to wind turbine blades having a composite construction and including a cellular structure and to methods of manufacturing composite wind turbine blades.

[0004] Background

[0005] Wind turbines are used to produce electrical energy using a renewable resource and without combusting a fossil fuel. A wind turbine converts kinetic energy from the wind into electrical power. A wind turbine installation includes a foundation, a tower supported by the foundation, and an energy generating unit positioned atop of the tower. The energy generating unit typically includes one or more nacelles to house several mechanical and electrical components, such as a generator, gearbox, and main bearing, and the wind turbine also includes a rotor operatively coupled to the components in the nacelle through a main shaft extending from the nacelle. Single rotor wind turbines and multirotor wind turbines (which may have multiple nacelles) are known, but for the sake of efficiency, the following description refers to single rotor designs. The rotor, in turn, includes a central hub and a plurality of blades extending radially therefrom and configured to interact with the wind to cause rotation of the rotor. The rotor is supported on the main shaft, which is either directly or indirectly operatively coupled with the generator which is housed inside the nacelle. Consequently, as wind forces the blades to rotate, electrical energy is produced by the generator. Wind power has seen significant growth over the last few decades, with many wind turbine installations being located both on land and at offshore locations.

[0006] Generally, electrical energy production from a wind turbine increases with the size of the wind turbine. Therefore, modem multi-megawatt wind turbines are massive structures and the trend toward larger structures continues. These massive structures are assembled from component parts. As such, many wind turbines have their various component parts delivered in separate pieces to the site of the wind turbine installation. For example, the wind turbine tower, whichmay be formed by several tower sections, may be delivered to the installation site. The nacelle may be delivered to the installation site and mounted on the tower following its assembly. Lastly, the wind turbine blades, themselves being quite massive in size, have been conventionally transported individually to the installation site. Each wind turbine blade is separately raised and secured to a rotor hub normally via a pitch bearing, whereby the load from the wind turbine blade is transferred to the rotor hub.

[0007] Each wind turbine blade interacts with the wind to generate mechanical rotation of the rotor. Rotation is converted into electrical energy. To that end, the blades move through the ambient environment, typically at high speed and carry significant structural loads by which a rotor is rotated. Rotation of the rotor drives the generator.

[0008] A wind turbine blade is a shell that defines a generally hollow core. The shell forms the aerodynamic foil shape of the blade and is often a layered assembly of fiber composite, aluminum, or similar material with an outer skin defined by one or more coatings (polymeric elastomers, paint, etc.). The outer skin may be defined by several different layers, including at least an outermost topcoat, a second layer underneath the outermost topcoat, and a third layer underneath the second layer. While being largely hollow, wind turbine blades may also include one or more shear webs that traverse the generally hollow core and are coupled to spar caps. The shear webs and spar caps enable the shell to resist flap and edgewise loading during use of the blade.

[0009] Wind turbine blades are typically produced by a manually intensive production process performed at a centralized site. In one such process, two large-scale moulds must first be produced. The moulds define the shape of the wind turbine blade. Each mould forms approximately one half of the shell so that the moulds have a clam-shell type configuration.

[0010] Once the moulds are manufactured, a laminate structure that forms the shell of the wind turbine blade is produced in each mould by building a fiber-resin composite. Vacuum may be utilized to infuse a fabric, such as a glass fiber or carbon fiber fabric, with resin. The resin is then cured. The cured fiber-resincomposite structure conforms to the mould to form one-half of the shell. The two moulds (i.e., the two shell halves in their respective moulds) are then brought together. Once the two shell halves are bonded together to form the blade shell, the moulds are separated, and the blade shell is demoulded. Once the shell is demoulded, the blade is finished. Finishing may include trimming any excess material from the shell, such as along a seam, and adding one or more coatings to the exterior of the shell. Given the trend to larger blades further improvements in the blades and methods of manufacture are desirable.

[0011] Accordingly, there is a need for improved wind turbine blades and methods for manufacturing wind turbine blades that provide for an improved wind turbine blade.

[0012] Summary

[0013] A wind turbine blade and method for manufacturing a wind turbine blade are described herein. In one aspect of the invention, the wind turbine blade includes a blade part constructed with a cellular structure. The cellular structure may be 3D printed. The invention addresses many of the drawbacks with conventional wind turbine blades and manufacturing practices. In an exemplary embodiment, there is a wind turbine blade configured to be mounted to a hub of a wind turbine. The wind turbine blade includes a blade part having a sidewall. The sidewall includes (i) an outer skin of a first composite including a first reinforcement phase and a first matrix, (ii) an inner skin of a second composite including a second reinforcement phase and a second matrix, and (iii) a cellular structure including a plurality of walls defining a plurality of cells. The cellular structure is between the outer skin and the inner skin. The cellular structure includes an outer wall, an inner wall, and a mid portion between the outer wall and inner wall. The sidewall further includes (iv) a first composite layer including one or more of the plurality of walls, including the outer wall, and the first matrix, (v) a second composite layer including one or more of the plurality of walls, including the inner wall, and the second matrix, and (vi) one or more cells in the mid portion of the cellular structure being closed cells.

[0014] Embodiments of the invention advantageously include cellular structures in which one or more of the plurality of walls permit a limited, controlled amount ofresin infiltration into selected cells during manufacturing. Resin infiltration into the cellular structure is limited by one or more of the walls of the cellular structure. Overall, the cellular structure may hydraulically lock off a portion of the cells, such as the cells in a mid portion of the cellular structure, from infiltration of resin. By this hydraulic-lock-off effect, selected portions of the cellular structure lack resin. These portions therefore are not filled with resin. Unlike the prior art in which resin infiltration or uptake leads to full infiltration and a heavier blade, in embodiments of the invention, the infiltration of the resin is limited to selected portions of the cellular structure. Comparatively, shells made according to embodiments of the invention can have relatively thinner sidewalls. Additional advantages include tailoring resin distribution in the cellular structure to modify mass distribution in the wind turbine blade. Modifying the mass distribution may be used to change a balance point of the blade.

[0015] In an exemplary embodiment, a density of the plurality of cells in the mid portion is less than a density of the plurality of cells at one or both the inner wall and the outer wall. As an example, the density at the mid portion is 25% to 75% less than the density at one or both the inner wall and the outer wall.

[0016] In an exemplary embodiment, each of the plurality of cells have a length and a width to define an area in a cross section of the sidewall, and one or more of the plurality of outer cells adjacent the outer wall and / or one or more of the plurality of inner cells adjacent the inner wall are smaller in area than the area of one or more of the plurality of cells in the mid portion of the cellular structure.

[0017] In an exemplary embodiment, the mid portion of the cellular structure is free of the first matrix and is free of the second matrix.

[0018] In an exemplary embodiment, (i) the outer wall and one or more of the plurality of walls define a plurality of outer cells adjacent the outer wall and the first composite layer further includes one or more of the plurality of outer cells, and / or (ii) the inner wall and one or more of the plurality of walls define a plurality of inner cells adjacent the inner wall and the second composite layer further includes one or more of the plurality of inner cells.In an exemplary embodiment, the plurality of outer cells adjacent the outer wall and / or the plurality of inner cells adjacent the inner wall is filled with the first matrix and the second matrix, respectively.

[0019] In an exemplary embodiment, each of the plurality of cells of the cellular structure is a closed cell.

[0020] In an exemplary embodiment, the plurality of inner cells are not in fluid communication with the plurality of outer cells.

[0021] In an exemplary embodiment, neither the plurality of inner cells nor the plurality of outer cells is in fluid communication with the plurality of cells in the mid portion of the cellular structure.

[0022] In an exemplary embodiment, the first matrix is a first resin and the second matrix is a second resin, and the first resin is the same material as the second resin.

[0023] In an exemplary embodiment, the blade part is a shell and the sidewall extends between a root end and a tip of the blade.

[0024] According to one aspect of the invention, there is a method for manufacturing a wind turbine blade part for a wind turbine blade. The method includes placing one or more fiber layers on a surface of a mould and placing one or more cellular structures on the one or more fabric layers. The one or more cellular structures include a plurality of walls defining a plurality of cells. The cellular structure includes an outer wall, an inner wall, and a mid portion between the outer wall and inner wall. One or more cells of the plurality of cells in the mid portion are closed cells. The method further includes placing another one or more fiber layers on the inner wall of the one or more cellular structures, creating a vacuum region surrounding the another one or more fiber layers, the cellular structure, and the one or more fiber layers, and admitting a resin into the vacuum region whereby the another one or more fiber layers (i.e. , inner one or more fiber layers) and the one or more fiber layers (i.e., outer one or more fiber layers) are impregnated with the resin. During admitting, the resinpenetrates the cellular structure at the outer wall, and the resin penetrates the cellular structure at the inner wall. The method further includes curing the resin to form a first composite layer including the outer wall and a first matrix of the cured resin and a second composite layer including the inner wall and a second matrix of the cured resin.

[0025] In an exemplary embodiment, prior to placing, the method further includes 3D printing the cellular structure. 3D printing includes printing the plurality of cells so that a density of the plurality of cells in a mid portion of the cellular structure between the outer wall and the inner wall is less than a density of the plurality of cells at one or both the inner wall and the outer wall. For example, 3D printing includes printing the cellular structure wherein the density at the mid portion is 25% to 75% less than the density at one or both the inner wall and the outer wall.

[0026] In an exemplary embodiment, during 3D printing, each of the plurality of cells has a length and a width to define an area in a cross section of the sidewall, and one or more of the plurality of cells adjacent the outer wall and / or one or more of the plurality of cells adjacent the inner wall are smaller in area than the area of one or more of the plurality of cells in the mid portion of the cellular structure.

[0027] In an exemplary embodiment, during 3D printing, (i) the outer wall and one or more of the plurality of walls define a plurality of cells adjacent the outer wall and wherein after curing, the first composite layer further comprises one or more of the plurality of cells adjacent the outer wall, and (ii) the inner wall and one or more of the plurality of walls define a plurality of cells adjacent the inner wall and wherein after curing, the second composite layer further includes one or more of the plurality of cells adjacent the inner wall. For example, following admitting, the one or more of the plurality of outer cells adjacent the outer wall and / or the one or more of the plurality of inner cells adjacent the inner wall is filled with the resin.

[0028] In an exemplary embodiment, during printing, each of the plurality of cells in the mid portion of the cellular structure is a closed cell.In an exemplary embodiment, during admitting, the plurality of cells along the mid portion of the cellular structure is free of the resin.

[0029] In an exemplary embodiment, the mould is sized and shaped for moulding a shell for a wind turbine blade and following curing, the shell is removed from the mould.

[0030] Brief Description of the Drawings

[0031] Various additional features and advantages of the invention will become more apparent to those of ordinary skill in the art upon review of the following detailed description of one or more illustrative embodiments taken in conjunction with the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the general description given above and the detailed description given below, serve to explain the one or more embodiments of the invention.

[0032] Fig. 1 is an elevation view of a wind turbine including a plurality of blades, the blades being in accordance with one embodiment of the invention.

[0033] Fig. 2 is a cross sectional view of a wind turbine blade according to one embodiment taken along section line 2-2 of Fig. 1.

[0034] Fig. 3 is an enlarged view of the encircled area 3 in Fig. 2.

[0035] Fig. 3A is an enlarged partial view of encircled area 3A in Fig. 3.

[0036] Fig. 3B is an enlarged partial view of encircled area 3B in Fig. 3.

[0037] Fig. 4 is cross-sectional view of one stage of a manufacturing process for manufacturing a wind turbine blade according to one embodiment of the invention.

[0038] Fig. 4A is an enlarged view of the encircled area 4A in Fig. 4.Fig. 5 is cross-sectional view of one stage of a manufacturing process for manufacturing a wind turbine blade according to one embodiment of the invention.

[0039] Fig. 5A is an enlarged view of the encircled area 5A in Fig. 5.

[0040] Detailed Description

[0041] To those and other ends and with reference to Figs. 1, 2, and 3, a wind turbine 12 is shown and includes a tower 14, a nacelle 16 disposed at the apex of the tower 1 , and a rotor 20 operatively coupled to a generator (not shown) housed inside the nacelle 16. The rotor 20 of the wind turbine 12 includes a central hub 22 and a plurality of wind turbine blades 24 that project outwardly from the central hub 22 at locations circumferentially distributed around the hub 22. As shown, the rotor 20 includes three wind turbine blades 24, but the number of blades 24 may vary from one wind turbine to another. Each wind turbine blade 24 is elongated and includes a root end 26, which is configured to be coupled to the central hub 22 when mounted to the rotor 20, and a tip end 30 longitudinally opposite to root end 26. The wind turbine blades 24 are configured to interact with air flow to produce lift that causes the rotor 20 to spin generally within a plane defined by the wind turbine blades 24. As the rotor 20 spins, the wind turbine blades 24 pass through the air with a leading edge 32 first contacting the air during normal rotation of the rotor 20 and forming an initial contact point of an airfoil, and a trailing edge 34 at an end of the airfoil.

[0042] Exemplary embodiments of the wind turbine blade 24 are composites structures that are constructed with one or more cellular structures, described below. Advantageously, the cellular structure reduces the mass of the wind turbine blade 24 to less than a comparable wind turbine blade constructed with materials, such as polyethylene terephthalate (PET) or balsa wood, while maintaining or improving strength of the wind turbine blade 24. Referring to Figs. 1 and 2, because the wind turbine 12 is utilized to produce electrical power, the wind turbine blades 24 are exposed to significant and sustained environmental and / or structural loading. Each wind turbine blade 24 isdesigned to endure the loads experienced during operation of the wind turbine 12 while also permitting efficient generation of energy across all wind speeds.

[0043] With reference to Fig. 2, a shell 36 is a generally tubular structure and defines an aerodynamic foil shape of one or more blades 24 shown in Fig. 1. The shell 36 includes a sidewall 40 that circumscribes a generally hollow interior in cross section. The sidewall 40 is a composite. Composites are engineered materials composed of at least two different materials. One of the materials forms a matrix phase and another material forms a reinforcement phase distributed in the matrix phase. Generally, the matrix phase is continuous, but embodiments of the invention are not limited to matrix phases being continuous. The reinforcement phase may be continuous or discontinuous. Further, composites may include additional phases and for that reason, embodiments of the invention are not limited to the presence of only two phases. Specifically, and without limitation, embodiments of the invention contemplate sidewalls 40 of three, four, and more phases.

[0044] In that regard, in the embodiment shown, the sidewall 40 may be visually divided into three general layers 42, 44, and 46. The layers 42, 44, 46 may each include different materials. As such, each of the layers 42, 44, 46 on its own may include a composite. While the sidewall 40 is shown in Fig. 2 as having well-defined visual boundaries between the outer layer 42 and the core 46 and between the inner layer 44 and the core 46 and so have a sandwichtype configuration, embodiments of the invention may not appear with three well-defined layers. Rather, embodiments of the invention include the sidewall 40 having a transition in material from a material of the outer layer 42 to a different material of the core 46 to yet another material of the inner layer 44.

[0045] In the exemplary embodiment, the outer layer 42 forms an exterior surface 48 of the shell 36. The exterior surface 48 of the shell 36 interacts with the environment. The outer layer 42 may be formed in whole or in part of an outer skin 50. The outer skin 50 is a composite of a reinforcement phase in a matrix phase, such as fiberglass in a resin matrix, and the outer skin 50 may extend the entirety of the perimeter of the shell 36 shown in Fig. 2. The outer skin 50, however, may not be continuous around the entire perimeter. That is, the outerskin 50 may include discontinuities, such as at mould seams, where the reinforcement phase and the matrix material end. The outer skin 50 forms a portion of the load-bearing structure of the shell 36. Although not shown, the outer layer 42 may include one or more coatings, such as paint coatings, (not shown) on the outer skin 50 primarily for improving the weatherability of the shell 36.

[0046] With continued reference to Fig. 2, the inner layer 44 may be formed in whole or in part of an inner skin 52. The inner layer 44 defines the generally hollow interior of the shell 36 by an interior surface 58. The inner skin 52 is a composite of a reinforcement phase in a matrix phase. For example, the inner skin 52 may be a composite of fiberglass in a resin matrix. In one embodiment, the composite of the inner skin 52 is the same composite as the composite of the outer skin 50. Alternatively, the inner skin 52 may be a different composite than the composite of the outer skin 50. The inner skin 52 may extend the entirety of the inner perimeter of the shell 36. Similar to the outer skin 50, the inner skin 52 may not be continuous around the entire perimeter. As an example, the inner skin 52 may include discontinuities at mould seams caused by the method by which the shell 36 is manufactured. The inner skin 52 forms a portion of the load-bearing structure of the shell 36.

[0047] According to exemplary embodiments of the invention, the core 46 is between the outer layer 42 and the inner layer 44. In the embodiment shown, the core 46 may be bonded, such as chemically and / or mechanically, to one or both the outer skin 50 and the inner skin 52. Collectively, the outer skin 50, the inner skin 52, and the core 46 form a layered composite structure that generally defines a load-bearing member of the shell 36 for transferring wind loading to the hub 22. The layered composite structure may also be referred to as a sandwich panel.

[0048] With reference to Figs. 2 and 3, according to embodiments of the invention, core 46 includes a cellular structure 56. As shown, the core 46 may include a plurality of cellular structures 56 arranged between the inner layer 44 and outer layer 42 around the circumference of the shell 36. In one embodiment, the shell 36 also includes one or more spar caps 60. The spar caps 60 may space oneof the cellular structures 56 apart from other cellular structures 56 in the core 46. As an example, and with reference to Fig. 2, there are two spar caps 60 that are arranged on opposite sides of the shell 36. The spar caps 60 space a first and second cellular structures 62a, 62b proximate the leading edge 32 from a third cellular structure 64 and a fourth cellular structure 66 that extend from the spaced-apart spar caps 60 toward the trailing edge 34 of the wind turbine blade 24. While four cellular structures 62a, 62b, 64, 66 are shown in Fig. 2, embodiments of the invention are not limited to four cellular structures 56 as more or fewer cellular structures 56 may be utilized between the outer skin 50 and the inner skin 52. Any arrangement of the cellular structures 56 in the core 46 may depend on the design of the blade 24 and particularly its designed load carrying capacity, the composites of the inner skin 52, and the outer skin 50 to name a few.

[0049] With continued reference to Fig 2, while being largely hollow, the shell 36 may also include one or more shear webs 68 that traverse the generally hollow shell 36 and support spar caps 60. In the exemplary embodiment shown, the shear web 68 divides hollow interior of the shell 36 into two volumes 78. The shear webs 68 and spar caps 60 enable the shell 36 to resist flap and edgewise loading during operation of the wind turbine 12. Embodiments of the shell 36 are not limited to the presence and / or arrangement of the spar caps 60 and shear web 68 shown.

[0050] In an exemplary embodiment and with reference to Figs. 3 and 3A, the cellular structure 56 forms the core 46 between the inner skin 52 and the outer skin 50 of the shell 36. The cellular structure 56 is configured to strengthen the shell 36. In that regard, the cellular structure 56 includes a plurality of walls 70 that distribute loads between the inner skin 52 and outer skin 50. In one embodiment, the walls 70 extend from an outer edge 72 to an inner edge 74 of the cellular structure 56 and so are largely continuous between the edges 72, 74. As shown, the walls 70 form a plurality of individual cells 76 that may have regular, predefined shapes, such as triangular or rectangular. Further, the predefined shapes may be closed shapes.In an exemplary embodiment and with reference to Figs. 3 and 3A, an inner wall 80 defines the inner edge 74 of the cellular structure 56. The inner wall 80 and walls 70 define a plurality of inner cells 82 adjacent the inner edge 74 of the cellular structure 56. A material 84 (shown shaded in Figs. 3 and 3A) forming a portion of the inner skin 52 extends into the plurality of inner cells 82 of the cellular structure 56 and into contact with inner walls 70. As an example, a matrix phase 84, such as a cured resin, that forms the composite of the inner skin 52 at least partially extends into the individual ones of the inner cells 82. The overlap of the matrix phase 84 and the walls 70 and 80 of the cellular structure 56 forms a composite layer 86 extending toward the outer skin 50. In one embodiment, the composite layer 86 consists of the material of the cellular structure 56 and the matrix phase 84. The composite layer 86 advantageously interlocks the cellular structure 56 to the inner skin 52.

[0051] Further, according to one embodiment, the matrix phase 84 of the inner skin 52 and the cellular structure 56 may not overlap beyond the inner cells 82 adjacent the inner edge 74. The matrix phase 84 may completely fill the inner cells 82 in the composite layer 86, but embodiments of the invention are not limited to the complete filling of any single inner cell 82 adjacent the edge 74. While not shown, some cells 76 in the cellular structure 56 may only be partially filled with the matrix phase 84. Further, while the composite layer 86 is shown as a single layer of inner cells 82 and the matrix phase 84, embodiments of the invention are not limited to a specific number of cells forming the composite layer 86. The number of cells and location of cells that are filled with the matrix phase 84 may be controlled by controlling a relative thickness of the walls 70 and 80 with relatively thinner walls permitting filling of resin during manufacturing, described below. According to exemplary embodiments, the matrix phase 84 extends to less than one-half of a height H (Fig. 3) of the cellular structure 56. By way of example and not limitation, the continuous phase 84 extends to 25% or less of the height H. By way of further example, less than 25% of the total volume of the cells 76 are filled with the continuous phase 84, and as an additional example, less than 10% of the total volume of cells 76 is filled with the continuous phase 84.With reference to Fig. 3B, a similar composite layer may exist between the outer skin 50 and the cellular structure 56 in addition to or as an alternative to the composite layer 86 between the inner skin 52 and the cellular structure 56. More specifically, in the exemplary embodiment, an outer wall 90 of the cellular structure 56 defines the outer edge 72 of the cellular structure 56. The outer wall 90 and walls 70 define a plurality of outer cells 92 adjacent the outer edge 72. A material 94 (shown shaded in Figs. 3 and 3B) forming a portion of the outer skin 50 extends into the plurality of outer cells 92 of the cellular structure 56 and into contact with the inner walls 70. As an example, a matrix phase 94, such as a cured resin, that forms the composite of the outer skin 50 at least extends into the individual ones of the outer cells 92. The overlap of the matrix phase 94 and the walls 70 and 90 of the cellular structure 56 forms a composite layer 96 extending toward the inner skin 52. In one embodiment, the composite layer 96 consists of the material of the cellular structure 56 and the matrix phase 94. The composite layer 96 advantageously interlocks the cellular structure 56 to the outer skin 50.

[0052] Further, the matrix phase 94 of the outer skin 50 and the cellular structure 56 may not overlap beyond the outer cells 92 adjacent the outer edge 72. The matrix phase 94 may completely fill the outer cells 92 in the composite layer 96, but embodiments of the invention are not limited to the complete filling of any single outer cell 92 adjacent the edge 72. As shown, some cells 76 in cellular structure 56 may only be partially filled with matrix phase 94. Further, while the composite layer 96 is shown as a single layer of outer cells 92 and the matrix phase 94, embodiments of the invention are not limited to a specific number of cells forming the composite layer 96. According to exemplary embodiments, the matrix phase 94 extends to less than one-half of a height H (Fig. 3) of the cellular structure 56. By way of example and not limitation, the matrix phase 94 extends to 25% or less of the height H. By way of further example, less than 25% of the total volume of the cells 76 are filled with the matrix phase 94, and as an additional example, less than 10% of the total volume of cells 76 is filled with the matrix phase 94.

[0053] Referring to Fig. 3, a mid portion 98 of the cellular structure 56 in between the composite layers 86, 96 is free of the matrix 84 and is free of the matrix 94,respectively. Instead of matrix 84, 94, the mid portion 98 includes cells 76 that are closed and may therefore contain a gas. In an exemplary embodiment in which one or more of the cells 76 is a closed cell, the inner cells 82 are not in fluid communication with the outer cells 92. Further, neither the inner cells 82 nor the outer cells 92 are in fluid communication with the cells 76 in the mid portion 98 of the cellular structure 56.

[0054] As shown in the exemplary embodiment of Figs. 3, 3A, and 3B, the relative size of the individual cells 76 varies from the outer edge 72 to the inner edge 74. Stated another way, a density (i.e., the number of cells 76 per unit volume of the cellular structure 56) of the cells 76 in the mid portion 98 of the cellular structure 56 is less than the density of cells 82, 92 at one or both edges 72, 74 adjacent the inner wall 80 and the outer wall 90, respectively. For example, the density in the mid portion 98 of the cellular structure 56 is in a range of 3,000 cells per cubic meter to 5,000 cells per cubic meter and the density for cells 76 at walls 80, 90 (i.e., at edges 72, 74) is 25% to 75% greater than the density at the mid portion 98. By way of further example only and not limitation the density in at one or both edges 72, 74 is 40% to 60% greater than the density of the mid portion 98.

[0055] Further, with respect to the cross section shown, walls 70 define closed cells 76 in which the walls 70 enclose a fixed volume. This is in contrast with an open cell in which walls do not enclose a volume. In the exemplary embodiment, the closed shapes in cross section include triangles or rectangles of varying size and encompassing varying areas. An area of each cell 76 may be defined by individual lengths and widths of the walls 70 in the plane of the figure. In the exemplary embodiment, the relative variation in area is generally from closed shapes having smaller areas at or near the edges 72, 74 to closed shapes having larger areas at about the mid portion 98 of the cellular structure 56 between the edges 72, 74. The composite layers 86, 96 therefore generally include relatively small, closed cells 76. By way of example, in cross section, individual cells 76 vary in dimension from 2 mm to 2.5 mm at the edges 72, 74 to 8 mm to 10 mm at a mid portion of the cellular structure 56. By way of additional example, inner cells 82 and / or outer cells 92 may be up to 50%smaller in area or up to 80% smaller in area than the area of cells 76 at a mid portion 98 of the cellular structure 56.

[0056] While not shown, a depth dimension (i.e., a dimension perpendicular to the page) of the walls 70 may approximate the length and width dimensions of the cells 76 shown in Fig. 3. With the length, width, and depth dimensions being proportional with one another, a volume distribution of the cells 76 may be similar to the area distribution of cells 76 shown. That is, the cells 76 form closed volumetric shapes and the volume of individual cells 76 at or near mid portion 98 of the cellular structure 56 is generally greater than a volume of the individual cells 82, 92 at or near the edges 72, 74 of the cellular structure 56. Advantageously, with the distribution in density according to area or to volume of the size of individual ones of the closed cells 76, the cellular structure 56 may be designed to reduce weight of the shell 36 while also providing for increased strength in the regions of the composite layers 86, 96. Embodiments of the invention are not limited to this arrangement. For example, the cellular structure 56 could have a uniform size distribution of closed shapes so that the cells 82, 92 of composite layers 86, 96, respectively, do not vary in area relative to the unfilled cells 76 of the cellular structure 56.

[0057] With reference to Figs. 4 and 5, a blade manufacturing system 100 forms the shell 36 (Fig. 3). In the exemplary manufacturing system 100, the shell 36 is manufactured in shell halves 102. For simplicity, only one half 102 is shown and described. Manufacturing the other half (not shown) of the shell 36 is similar to that shown with respect to the half 102, described below. Generally, the moulding process for the shell 36 includes preparing a lay-up of multiple layers of material into a shaped surface defined by the mould, applying vacuum to the lay-up, impregnating the lay-up with resin, and curing of the shell 36.

[0058] More specifically, the shell manufacturing system 100 utilizes a shell mould 104 by which the shell half 102 is constructed. While Fig. 4 depicts a cross section of the mould 104, the mould 104 extends longitudinally in a spanwise direction perpendicular to the plane of the page. The mould 104 is suitably-shaped for forming the shell half 102 of the wind turbine blade 24. A surface 106 of the mould 104 exhibits a concave curvature in a chordwise direction, correspondingto the curvature of the aerodynamic profile of the blade 24 to be formed in the mould 104. Once formed, the shell halves 102 are subsequently bonded together to form the shell 36. Embodiments of the invention are not limited to the system 100 shown. Other moulding operations may be utilized to manufacture the shell 36, for example, a single mould may be utilized to form the shell 36.

[0059] Referring to Figs. 4 and 4A, in the exemplary embodiment, shell half 102 is formed in the mould 104. To that end, one or more fiber layers 110 are arranged on the mould surface 106 to form the outer layer 42 of the shell 36. Exemplary fiber layers 110 include a glass fabric or another fiber type capable of forming a reinforcement phase of a composite.

[0060] At least one cellular structure 56 is then arranged on top of the fiber layer(s) 110. By way of example, two cellular structures, labelled 62a and 64, are shown in Figs. 4 and 5 though many more cellular structures 56 may be distributed along the length of the mould 104. Each of the cellular structures 62a, 64 may be formed by additive manufacturing (also referred to as 3D printing). Additive manufacturing may include a layering process, such as VAT photopolymerization, stereo lithography (SL), digital light processing (DLP), selective laser sintering (SLS), selective laser melting (SLM), electron beam melting (EBM), binder jetting, material jetting, direct metal layer sintering (DMLS), or fused deposition modeling (FDM). These processes utilize computer-controlled deposition of individual layers of material based on a computer model of the cellular structure 62a, 64. The deposited layers are based on discrete cross sections of the computer model as determined by slicing the model into a finite number of individual model layers. Each virtual model layer is then produced by depositing a layer of material from a 3D printer. Exemplary materials for printing the cellular structures 56 include thermoplastic polymers. By way of specific example, the cellular structures 56 may be made by printing with a thermoplastic polymer NEAT (e.g., Acrylonitrile Styrene Acrylate (ASA), Polyethylene Terephthalate Glycol-modified (PETG), PSA, polycarbonate (PC), etc.), with a thermoplastic polymer with a filler (e.g., short glass or carbon fiber, basalt, glass spheroids, etc.), or with a thermosetting polymer (e.g., epoxy, vitrimer, photo-reactive polymer, Poly(methylmethacrylate) (PMMA), etc.) from a virtual model. By constructing each layer, one layer on a preceding layer, the 3D printer forms the cellular structures 62a, 64. Advantageously, 3D printing permits deposition of walls 70 to form cells 76 (see e.g., Fig. 3) according to a predetermined wall thickness and a predetermined size and density of cells 76. Exemplary dimensions and densities are described above.

[0061] The cells 76 may be printed as closed cells in which the walls 70 enclose a volume of void space, which may contain a gas, such as air. The walls 70 therefore prohibit entry and exit of fluid from the cell 76. Further the walls 70 may be constructed with differing thickness. As an example, the walls 80 and 90 at the edges 72, 74 of the cellular structure 56 may be tailored to permit penetration of resin into the cellular structure 56 during impregnation of the layup with resin, described below. However, the walls 70 in the interior of the cellular structure 56 may prohibit penetration of resin. Predetermining the relative wall thickness, cell sizes, and closed nature of the cells 76 in the cellular structure 56 may be advantageous in controlling the formation of the composite layers 84 and 94. Alternatively, the cellular structures 62a, 64 may be formed by a separate moulding operation. In this regard, the manufacturing system may include at least one mould or forming technique (i.e., not 3D printing) configured to form the cellular structures 62a, 64.

[0062] A second fiber layer 112 may be arranged on top of the fiber layer(s) 110 to form the spar cap 60. By way of example, the second fiber layer 112 may be the same as the first fiber layer 110 or be a different fabric. As examples, the fiber layer 112 may be a pultruded strip, a woven glass fabric, a carbon fiber fabric or another fiber type capable of forming a reinforcement phase of a composite. As shown, the fiber layer 112 spaces cellular structure 62a apart from cellular structure 64 to form the core 46 of the shell 36. The arrangement of the cellular structures 62a, 64 and the fiber layer 112 may depend on the structural requirements of the blade 24 and so may vary from that shown. For example, the layer 112 may not be present. Further, other structures, such as additional fiber layers 112 for additional spar caps, may be arranged on the fiber layer(s) 110.Referring now to Fig. 5, once the fiber layer(s) 110 and the cellular structures 62a, 64 have been arranged in the mould 104, one or more further layers of fiber 114 are arranged on top of the intermediate layer 46. By way of example, the fiber layer 114 may be the same as the first fiber layer 110 or be a different fabric. This lay-up comprising the layers 110, layers 112, layers 114, and cellular structure 56 is then covered with vacuum-bagging film 120, which is sealed against the mould flange 122 using sealing tape 124. A vacuum is created in the sealed region defined between the vacuum-bagging film 120 and the mould surface 106 by a vacuum pump 126. Once a vacuum is achieved, a resin 130 from resin source is admitted into the sealed region via the resin inlet channel 132. Under vacuum assistance, the resin 130 flows out of the resin inlet channel 132 through the lay-up, particularly into and through layers 110, 112, and 114. In one embodiment, admitting the resin into the vacuum region may be according to a Vacuum Assisted Resin Transfer Moulding (VARTM) process.

[0063] With reference to Fig. 5A, the resin 130 flows from the source to void space between the film 120 and the cellular structure 56 as defined by the fiber layer 114, and the resin 130 flows from the source to void space between the mould surface 106 and the cellular structure 56 defined by the fiber layer 110. This is generally indicated by arrows 134 in Fig. 5A.

[0064] In addition to general flow according to arrows 134, which is generally parallel to the mould surface 106 and by which the fiber layers 110, 114 are impregnated with resin 130, the resin 130 also penetrates the cellular structure 56 at cells 82, 92 at the edges 72, 74, respectively (see Fig. 3, 3A, and 3B). With the aid of vacuum, the resin 130 may penetrate through the wall 80 and / or the wall 90 and selected walls 70 in the cellular structure 56 to fill cells 82, 92 proximate the edges 72, 74. In addition to the flow direction 134, the resin 130 therefore has a flow direction inwardly (i.e., transversally relative to the mould surface 106) according to arrows 136 into the cellular structure 56.

[0065] The resin 130, however, does not flow through the cellular structure 56. That is, the resin 130 does not flow from the edge 72 to the edge 74 or vice versa across the height H of the cellular structure 56. Rather, resin 130 penetrationinto the cellular structure 56 is limited to selected cells 82, 92 at or near the edges 72, 74. The closed nature of the cells, particularly the cells 76 in the mid portion 98 of the cellular structure 56, prohibits cross flow of the resin 130 through the cellular structure 56. The cellular structure 56 may hydraulically lock off the closed cells 76 in the interior of the cellular structure 56 after the resin penetrates cells 82, 92 at or near the edges 72, 74. There is therefore a sufficient number of closed cells 76 along the mid portion 98 of the cellular structure 56 to act as a barrier to resin flow across the cellular structure 56. For this reason, cells 76 in the mid portion 98 of the cellular structure 56 are not filled during impregnation. Consequently, an interior portion of the cellular structure 56 is free of resin 130 following the impregnation process. This is shown in Figs. 3, 3A, and 3B in which interior cells 76 are free of resin 130. After curing, by this limited impregnation of the cellular structure 56 to a predetermined depth along the edges 72, 74, the composite layers 84 and 94 are formed and the outer skin 50 and inner skin 52 are bonded to the cellular structure 56.

[0066] While the present invention has been illustrated by the description of various embodiments thereof, and while the embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. Thus, the various features discussed herein may be used alone or in any combination, including with any type of single rotor or multi rotor wind turbine. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the invention as defined in the claims.

Claims

CLAIMS1. A wind turbine blade (24) configured to be mounted to a hub (22) of a wind turbine (12), comprising:a blade part having a sidewall (40), the sidewall (40) comprising:(i) an outer skin (50) of a first composite comprising a first reinforcement phase and a first matrix,(ii) an inner skin (52) of a second composite comprising a second reinforcement phase and a second matrix,(iii) a cellular structure (56) including a plurality of walls (70) defining a plurality of cells (76), the cellular structure (56) including an outer wall (90), an inner wall (80), and a mid portion (98) between the outer wall (90) and inner wall (80), the cellular structure (56) being between the outer skin (50) and the inner skin (52),(iv) a first composite layer (96) comprising one or more of the plurality of walls (70), including the outer wall (90), and the first matrix (94),(v) a second composite layer (86) comprising one or more of the plurality of walls (70), including the inner wall (80), and the second matrix (84), and(vi) one or more cells (76) in the mid portion (98) of the cellular structure (56) being closed cells.

2. The wind turbine blade (24) of claim 1, wherein a density of the plurality of cells (76) in the mid portion (98) is less than a density of the plurality of cells (76) at one or both the inner wall (80) and the outer wall (90).

3. The wind turbine blade (24) of claim 2, wherein the density of cells (76) at one or both the inner wall (80) and the outer wall (90) is 25% to 75% greater than the density at the mid portion (98).

4. The wind turbine blade (24) of any preceding claim, wherein each of the plurality of cells (76) have a length and a width to define an area in a cross section of the sidewall (40), andwherein one or more of the plurality of cells (76) adjacent the outer wall (90) and / or one or more of the plurality of cells (76) adjacent the inner wall (80) are smaller in area than the area of one or more of the plurality of cells (76) in the mid portion (98) of the cellular structure (56).

5. The wind turbine blade (24) of any preceding claim, wherein the mid portion (98) of the cellular structure (56) is free of the first matrix (94) and is free of the second matrix (84).

6. The wind turbine blade (24) of any preceding claim, wherein(i) the outer wall (90) and one or more of the plurality of walls (70) define a plurality of outer cells (92) adjacent the outer wall (90) and wherein the first composite layer (96) further comprises one or more of the plurality of outer cells (92), and / or(ii) the inner wall (80) and one or more of the plurality of walls (70) define a plurality of inner cells (82) adjacent the inner wall (80) and wherein the second composite layer (86) further comprises one or more of the plurality of inner cells (82).

7. The wind turbine blade (24) of claim 6, wherein the plurality of outer cells (92) and / or the plurality of inner cells (82) is filled with the first matrix and the second matrix, respectively.

8. The wind turbine blade (24) of any preceding claim, wherein each of the plurality of cells (76) of the cellular structure (56) is a closed cell.

9. The wind turbine blade (24) of any preceding claim, wherein the first matrix (94) is a first resin and the second matrix (84) is a second resin, and wherein the first resin is the same material as the second resin.

10. The wind turbine blade (24) of any preceding claim, wherein the blade part is a shell (36) and the sidewall (40) extends between a root end (26) and a tip (30) of the blade (24).

11. A method for manufacturing a wind turbine blade part for a wind turbine blade (24), the method comprising:placing one or more fiber layers (110) on a surface (106) of a mould (104);placing one or more cellular structures (56) on the one or more fiber layers (110), the one or more cellular structure (56) including a plurality of walls (70) defining a plurality of cells (76), the cellular structure (56) including an outer wall (90), an inner wall (80), and a mid portion (98) between the outer wall (90) and inner wall (80), one or more cells (76) of the plurality of cells (76) in the mid portion (98) being closed cells;placing another one or more fiber layers (114) on the inner wall (80) of the one or more cellular structures (56);creating a vacuum region surrounding the one or more fiber layers (110), the cellular structure (56), and the another one or more fiber layers (114);admitting a resin (130) into the vacuum region whereby the one or more fiber layers (110) and the another one or more fiber layers (114) are impregnated with the resin (130),wherein during admitting, the resin (130) penetrates the cellular structure (56) at the outer wall (90), and the resin (130) penetrates the cellular structure (56) at the inner wall (80); andcuring the resin (130) to form a first composite layer (96) including the outer wall (90) and a first matrix (94) of the cured resin and a second composite layer (86) including the inner wall (80) and a second matrix (84) of the cured resin.

12. The method of claim 11, wherein prior to placing, the method further comprises:3D printing the cellular structure (56), wherein 3D printing includes printing the plurality of cells (76) so that a density of the plurality of cells (76) in a mid portion (98) of the cellular structure (56) between the outer wall (90) and the inner wall (80) is less than a density of the plurality of cells (76) at one or both the inner wall (80) and the outer wall (90).

13. The method of claim 12, wherein 3D printing includes printing the cellular structure (56) wherein the density at one or both the inner wall (80) and the outer wall (90) is 25% to 75% greater than the density at the mid portion (98).

14. The method of any of claims 12 or 13, wherein, during 3D printing, each of the plurality of cells (76) has a length and a width to define an area in a cross section of the sidewall (40), andwherein one or more of the plurality of cells (76) adjacent the outer wall (90) and / or one or more of the plurality of cells (76) adjacent the inner wall (80) are smaller in area than the area of one or more of the plurality of cells (76) in the mid portion (98) of the cellular structure (56).

15. The method of any of claims 11 to 14, wherein during 3D printing,(i) the outer wall (90) and one or more of the plurality of walls (70) define a plurality of outer cells (92) adjacent the outer wall (90) and wherein after curing, the first composite layer (96) further comprises one or more of the plurality of outer cells (92) adjacent the outer wall (90), and(ii) the inner wall (80) and one or more of the plurality of walls (70) define a plurality of inner cells (82) adjacent the inner wall (80) and wherein after curing, the second composite layer (86) further comprises one or more of the plurality of inner cells (82) adjacent the inner wall (80).

16. The method of claim 15, wherein following admitting the resin, the one or more of the plurality of outer cells (92) and / or the one or more of the plurality of inner cells (82) is filled with the resin (130).

17. The method of any of claims 11-16 wherein during printing, each of the plurality of cells (76) in the mid portion (98) of the cellular structure (56) is a closed cell.

18. The method of any of claims 11-17, wherein during admitting the resin, the plurality of cells (76) along the mid portion (98) of the cellular structure (56) is free of the resin (130).

19. The method of any of claims 11-18, wherein the mould (104) is sized and shaped for moulding a shell (36) for a wind turbine blade and wherein following curing, the shell (36) is removed from the mould (104).

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