METHOD OF MANUFACTURING AN ADAPTABLE CARBON-FIBER BEAM

Abstract

Provided is a method of manufacturing an adaptable pre-cast resin-infused carbon-fiber beam, which method includes the steps of arranging a plurality of elongate carbon-fiber blocks side by side; arranging sheets to enclose the blocks and to extend over opposing faces of adjacent blocks; arranging the sheets to converge as an outwardly projecting elongate bead at a junction between adjacent blocks; and pulling on the elongate bead to inhibit resin flow between blocks during a resin infusion step. Also provided is a pre-cast adaptable carbon-fiber beam manufactured using that method; a method of manufacturing a wind turbine rotor blade; and a wind turbine rotor blade.

Claims

1. A pre-cast adaptable carbon-fiber beam, comprising: a plurality of resin-infused blocks, wherein at least one pair of adjacent blocks are joined by an elongate bead formed by sheets and are pivotable about the elongate bead.

2. The pre-cast adaptable carbon-fiber beam according to claim 1, wherein the sheets comprise at least one unidirectional carbon-fiber sheet arranged to enclose the carbon-fiber blocks.

3. The pre-cast adaptable carbon-fiber beam according to claim 1, wherein the sheets comprise at least one glass-fiber cover sheet arranged about the unidirectional carbon-fiber sheet.

4. The pre-cast adaptable carbon-fiber beam according to claim 1, wherein each block comprises a stack of at least two pultruded carbon strips.

5. The pre-cast adaptable carbon-fiber beam according to claim 1, wherein opposing faces of adjacent blocks subtend an angle in the range of 5 to 20.

6. The pre-cast adaptable carbon-fiber beam according to claim 1, comprising a wedge-shaped element arranged along an outside face of a block.

7. The pre-cast adaptable carbon-fiber beam according to claim 1, wherein the pre-cast adaptable carbon-fiber beam is manufactured by arranging the plurality of blocks side by side; arranging the sheets to enclose the blocks and to extend over opposing faces of the at least one pair of adjacent blocks; arranging the sheets to converge as an outwardly projecting elongate bead at a junction between the at least one pair of adjacent blocks; pulling on the elongate bead; and performing a resin infusion step; wherein the pulling on the elongate bead inhibits resin flow between blocks during the resin infusion step.

8. A rotor blade comprising: a number of pre-cast adaptable carbon-fiber beams in a transition region of the rotor blade, wherein at least one pre-cast adaptable carbon-fiber beam includes a plurality of resin-infused blocks, wherein at least one pair of adjacent blocks are joined by an elongate bead formed by sheets and are pivotable about the elongate bead.

9. The rotor blade according to claim 8, wherein the at least one pre-cast adaptable carbon-fiber beam is incorporated at a leading edge of the transition region.

10. The rotor blade according to claim 8, wherein the at least one pre-cast adaptable carbon-fiber beam is incorporated at the trailing edge of the transition region.

11. The rotor blade according to claim 8, wherein the rotor blade is manufactured by providing a rotor blade mold to receive a composite layup; providing the at least one pre-cast adaptable carbon-fiber beam including the plurality of resin-infused blocks, wherein the at least one pair of adjacent blocks are joined by the elongate bead formed by sheets and are pivotable about the elongate bead; incorporating the at least one pre-cast carbon-fiber beam in the composite layup; and adjusting the shape of the at least one pre-cast carbon-fiber beam according to the shape of the rotor blade mold.

Description

DETAILED DESCRIPTION

[0045] FIG. 1 shows a series of cross-sections through a wind turbine rotor blade 8, commencing with a cross-section 81 through the circular root region 80R and progressing to a cross-section 85 through an airfoil region. The shape of the rotor blade transitions in a complex manner from the initially circular shape, as indicated by cross-sections 81-84. This inboard part of the rotor blade is referred to as the transition region or shoulder region and must be dimensioned to withstand high bending moments during normal operation of the wind turbine and also during severe wind conditions. The usual approach is to make the rotor blade shell very thick in the transition region, but the added composite material increases the weight of the rotor blade. Alternatively, it is known to embed reinforcing structures of a lightweight but rigid material such as wood, but these structures are time-consuming and expensive to manufacture. In another approach, as shown the wireframe representation in FIG. 2, lightweight carbon-fiber beams 8C can be embedded in the transition region 80 of a rotor blade 8. However, pre-cast carbon-fiber beams 8C made of economical pultruded parts are rectangular in shape and therefore do not conform to the curved leading edge LE or the tapered trailing edge TE. Furthermore, the flat shape of such carbon-fiber beams 8C makes it difficult to place them in the composite layers during build-up of the rotor blade shell in the molding process.

[0046] FIG. 3 is a wireframe representation that illustrates a reinforced transition region 30 in an embodiment of the inventive wind turbine rotor blade 3. Here, lightweight shape-adaptable pre-cast carbon-fiber beams 1 are embedded in the transition region 30 of the rotor blade 3. Each pre-cast adaptable carbon-fiber beam 1 comprises several elongate blocks 1B connected by elongate hinges 1H so that the shape of the beam 1 can be adjusted to conform to the shape of the rotor blade shell during the shell molding procedure.

[0047] FIGS. 4-6 illustrate stages in the manufacture of such a pre-cast adaptable carbon-fiber beam 1. In FIG. 4, a unidirectional carbon-fiber sheet 11 is laid on a surface. Blocks 1B of pultruded carbon-fiber elements 10 are assembled, whereby sheets 12 of biaxial carbon-fiber material are arranged between stack layers. Each pultruded carbon-fiber element 10 can have a cross-section with dimensions in the order of 50 mm50 mm, and a length in the order of 20 m. The elements 10 are selected to form blocks with straight side faces or inclined side faces, as shown here. The smallest radius of curvature of the completed adaptable carbon-fiber beam 1 will be determined by the angles a subtended between the blocks 1B.

[0048] FIG. 5 shows a subsequent stage. Here, all sheet layers 11, 12 have been pushed downwards in the gaps between adjacent blocks 1B to form a bead or hinge 1H at the underside of the assembly. The diagram also shows two lateral tapering elements 1W which will later help the adaptable carbon-fiber beam to be incorporated in the composite layup of a rotor blade. The unidirectional carbon-fiber sheet 11 extends outward to one side, to serve as a connecting surface 110 for electrical connection to a rotor blade LPS.

[0049] FIG. 6 shows one approach to forming the hinges 1H at the junctions between adjacent blocks 1B. Here, the molding surface is a table 2 with sections shaped to form channels 200 that will receive a bundle of sheet material as well as an inflatable hose 20. In this diagram, the carbon beam assembly is shown to also include a glass-fiber sheet 13 enclosing the other components. The entire assembly can be arranged inside a vacuum bag in preparation for a VARTM procedure, as will be known to the skilled person. The molding surface 2 is also provided with a resin inlet/outlet pair (indicated only schematically) under each elongate block 1B. During VARTM, a vacuum pump 24 is used to draw in resin from a reservoir 25 through the resin inlets 22 and to draw out excess resin through the resin outlets 23.

[0050] On the left, the diagram shows an enlarged view of a channel 200 between table sections 20, showing the inflatable hose in the center of the sheet material bundle 11, 12, 13, prior to inflation. When the hose is inflated, as shown on the right, the sheet layers 11, 12, 13 are pulled taut and pressed together. As a result, during resin infusion, the bead 1H acts as a barrier to the resin, which is inhibited from entering the bead 1H. As a result, the bead 1H remains dry and, after curing, the blocks are freely pivotable about the hinge formed by the dry sheet material of the bead 1H along the underside of the cured beam. Even so, the layers 10 of each block stack are firmly fused together by the cured resin, and firmly fused to their enclosing sheet layers 11, 12. The pre-cast adaptable carbon-fiber beam 1 is therefore inherently rigid while being shape-adjustable. This is indicated in FIGS. 7-9, which illustrate shape adaptation of the inventive pre-cast adaptable carbon-fiber beam 1. The block structure on either side of a hinge 1H can pivot to some extent, as determined by the angle a subtended between adjacent blocks. FIG. 8 shows the smallest radius of curvature when all blocks are pivoted inwards to the greatest extent, allowing the pre-cast adaptable carbon-fiber beam 1 to assume an arcuate shape as indicated by the curved line C. FIG. 9 shows a perspective view of an embodiment of the inventive pre-cast adaptable carbon-fiber beam 1, showing the hinges 1H at the underside of the adaptable carbon-fiber beam 1 and blocks which have not (yet) been pivoted to their greatest extent. This curved pre-cast adaptable carbon-fiber beam I can be arranged in a leading-edge transition region of a rotor blade mound during the layup procedure, so that the cured rotor blade will exhibit given greater structural rigidity without increasing its mass. The reduced rotor blade mass and reduced mass moment can facilitate a favorably longer rotor blade length and a corresponding increase in energy production.

[0051] The adaptable carbon-fiber beam 1 is connected to a rotor blade LPS by the outwardly extending band 110 of the unidirectional carbon-fiber sheets 11. With this arrangement, it is possible to minimize the risk of flash-over during a lightning strike.

[0052] FIG. 10 illustrates a step in the manufacture of a wind turbine rotor blade. The diagram shows a lower mound half 3M, at a cross-section through the transition region. The diagram shows an embodiment of the inventive pre-cast carbon-fiber beam 1 on the left, near the trailing edge region. The pre-cast carbon-fiber beam 1 can adapt to the slight curvature in this region and can easily be embedded in the composite layup 3L of the lower rotor blade half. The diagram also shows another embodiment of the inventive pre-cast carbon-fiber beam 1 on the right, near the leading-edge region. The pre-cast carbon-fiber beam 1 can also easily adapt its shape to be embedded in the composite layup 3L in the rounded shape of the mound in this region. This leading-edge pre-cast carbon-fiber beam 1 is shown with a hinge positioned along the junction between the lower mound half 3M and an upper mound half (indicated by the dashed line) The upper portion of the pre-cast carbon-fiber beam 1 can be pivoted upward when the lower layup is complete.

[0053] FIG. 11 shows an alternative manner of forming the pre-cast carbon beam 1. The assembly is prepared as described above in FIG. 4 and FIG. 5 and comprises stacks of pultruded carbon elements and glass-fiber sheets 11, 12. Here, a thin rod 4 is used to bring the excess sheet material below the level of the molding surface 2 and, during the resin infusion step, tension is maintained as indicated by the arrows so that the sheet layers are pressed together to inhibit resin flow from the blocks 1B into the beads 1H. Instead of using a rod 4 as shown here, the bead 1H can be formed by clamping the sheet layers firmly together along their entire length. The only requirement at this stage is that the sheet layers 11, 12 are pressed against each other in such a way as to prevent liquid resin from passing from a block 1B into the bead 1H.

[0054] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0055] For the sake of clarity, it is to be understood that the use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or elements.