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EP-4295030-B1 - CHAMFERED STRIP AND BEAM FOR A SPAR CAP OF A WIND TURBINE BLADE

EP4295030B1EP 4295030 B1EP4295030 B1EP 4295030B1EP-4295030-B1

Inventors

  • NIELSEN, MOGENS
  • SUN, WEI

Dates

Publication Date
20260506
Application Date
20220303

Claims (13)

  1. A wind turbine blade (10) of a wind turbine comprising a strip (50) for a spar cap of a wind turbine blade, wherein the strip (50) is made from a composite material comprising a matrix and a reinforcement, wherein the strip (50) comprises a first end region (51) and a second end region (52) connected to one another in a longitudinal direction (D) of the strip (50) by an intermediate region (53), wherein the intermediate region (53) comprises two mutually opposed longitudinally extending and parallel disposed intermediate surfaces (54, 55), wherein a thickness (T) of the strip (50) is determinable perpendicular to the two intermediate surfaces (54, 55) and a width (W) of the strip (50) is determinable perpendicular to the longitudinal direction (D) of the strip (50) and perpendicular to the thickness (T) of the strip (50), wherein the strip (50) is chamfered in at least one of the first and the second end regions (51, 52), wherein in the at least one chamfered end region (51, 52) the strip (50) is simultaneously chamfered along the width (W) and the thickness (T) in the longitudinal direction (D), wherein the at least one chamfered end region (51, 52) has a first edge (56) at the intermediate region (53) and a second edge (57) at its free end (58), wherein the first edge (56) and the second edge (57) are substantially parallel to one another, characterized in that a width chamfer angle (α) is determinable between the first edge (56) of the strip and the longitudinal direction (D), extending beyond the free end (58), wherein the width chamfer angle α is different from 90°, and wherein the first edge (56) is an edge between the intermediate region (53) and the chamfered end region (51).
  2. The wind turbine blade (10) according to claim 1, wherein the width chamfer angle (α) of the chamfer of the at least one chamfered end region (51, 52) determinable between the first edge (56) and the longitudinal direction (L) is within the range of 30° to 60°.
  3. The wind turbine blade (10) according to any of the previous claims, wherein a thickness chamfer angle (β) of the chamfer of the at least one chamfered end region (51, 52) determinable between a bottom intermediate surface (55) of the intermediate surfaces (54, 55) and a chamfered surface (59) of the chamfered end region (51, 52) is in the range of 0.2° to 5°.
  4. The wind turbine blade (10) according to any of the previous claims, wherein the reinforcement of the composite material comprises unidirectional fibers arranged in the longitudinal direction (D) of the strip (50).
  5. The wind turbine blade (10) according to any of the previous claims, wherein the composite material is a fiber-reinforced plastic, in particular a carbon fiber-reinforced plastic.
  6. The wind turbine blade (10) according to any of the previous claims, wherein the strip (50) is a pultruded part.
  7. Beam (40) for a spar cap (31) of a wind turbine blade (10), the beam (40) comprising at least two strips (50) according to any of the previous claims, the strips (50) being joined to each other such that they extend in parallel along a common longitudinal direction (D) of the strips (50) and the beam (40).
  8. Beam (40) according to claim 7, wherein the at least two strips (50) are located at outer longitudinal sides (41, 42) of the beam (40) and their chamfered end regions (51, 52) are chamfered towards each other along their width (W) and in the common longitudinal direction (D).
  9. Beam (40) according to claim 8, wherein the width of the beam (40) decreases in the longitudinal direction (D) towards its free end (44).
  10. Beam (40) according to claim 8 or 9, wherein at least two of the chamfered end regions (51, 52) of the strips (50) are different from one another.
  11. Beam (40) according to any of claims 7 to 10, wherein at least one further strip (60) is disposed in between the at least two strips (50), wherein that further strip (60) is not chamfered along its width (W).
  12. Spar cap (31) for a wind turbine blade (10), the spar cap (31) having at least two beams (40) according to any one of claims 7 to 11 stacked on top of one another as layers of the spar cap (31).
  13. Method for machining a strip (50) according to any of claims 1 to 6, whereby the method comprises cutting off a portion from the at least one chamfered end region (51, 52) in the strip (50) in a single cutting step such that the at least one chamfered end region (51, 52) is machined.

Description

The invention is directed at a strip for a spar cap of a wind turbine blade, wherein the strip is made from a composite material. Further, the invention is directed at a beam for the spar cap having two or more of these strips. Also, the invention is directed at a spar cap having two or more of these beams and a wind turbine blade having one or more of these spar caps. Wind turbine blades must be able to efficiently convert wind into a spinning movement of the wind turbine blades, so that the energy of the wind can be converted into rotary mechanical movement of a rotor to which the wind turbine blades are attached. Dimensions of wind turbines and wind blades are ever increasing, and consequently are increasing the challenges to overcome during the manufacturing processes of such wind turbine rotor blades. EP 3 549 752 A1 describes a spar cap of a wind turbine rotor blade consisting of pultruded unidirectional fibrous composite strips. WO 2015/070876 A1 describes a strip of fibre-reinforced polymeric material for a longitudinal reinforcing structure of a wind turbine blade. It is preferable, to use materials having a high specific modulus (elastic modulus per mass density of a material), also known as stiffness to weight ratio, in wind turbine blades to deal with the square-cube law governing the scaling of wind turbine blades. Therefore, composite materials such as carbon fiber-reinforced plastic having a high specific modulus are commonly used in wind turbine blades. Generally, strips made from composite material, such as carbon, may be applied in the manufacturing of a pre-casted spar cap so as to form a rectangular parallelepiped geometry. The strips are typically chamfered at both ends during manufacture to ensure a smooth thickness reduction and also a smooth stiffness transition to interfaces, which for example may be made from unidirectional glass plies and be provided at the end of beam. Without chamfering the strips at these locations, a significant shear stress transfer between different layers of strips in the spar cap may create cracks and delamination in-between the layers of strips and in between the strips and the interfaces, and eventually lead to a failure of the wind turbine blade. FIG. 3 shows a perspective view on a portion of a spar cap 31 according to the prior art. The upper illustration in FIG. 3 shows an exploded view of two beams 40.1, 40.2 joined on top of each other so as to form the spar cap 31 seen in the bottom illustration of FIG. 3. An upper beam 40.1 of the two beams 40.1, 40.2 has three strips 50.1, 50.2, 50.3 made from a composite material and joined with each other along their longitudinal extension. Each of the strips 50.1, 50.2, 50.3 has a chamfered end region 51.1, 51.2, 51.3. These end regions 51.1, 51.2, 51.3 are located at free ends of the strips 50.1, 50.2, 50.3. The chamfer in these end regions 51.1, 51.2, 51.3 is provided along its thickness. A lower beam 40.2 of the two beams 40.1, 40.2 has the same chamfer design as the top beam 40.1. The direction of the chamfer of the chamfered end regions 51.1...51.6 of the strips 50.1...50.6 is unified in the longitudinal direction of the spar cap 31. The chamfered end regions 51.1...51.6 of adjacent strips 50.1...50.6 start and end at respectively the same length position of the strips 50.1...50.6. The design of the spar cap in the state of the art can only be changed in a very limited way to further improve the above-mentioned shear stress transfer and further optimize other areas for improvement, such as areas relating to design and mass of the spar cap, for example. Thus, there is still a need for a design of a spar cap and components thereof, in particular strips and beams, which provides improved stress distribution and design options at little manufacturing costs. This problem is solved by the subject-matter of the claims. Therefore, this object is solved by a wind turbine blade of a wind turbine comprising a strip for a spar cap of a wind turbine according to claim 1, a beam according to claim 7, a spar cap according to claim 12 and a method for machining a strip according to claim 13. Further details of the invention unfold from the other claims as well as the description and the drawings. Thereby, the features and details described in connection with the strip of the invention apply in connection with the beam according to the invention, the spar cap of the invention, the wind turbine blade of the invention and the method of the invention as well as the other way around, so that regarding the disclosure of the individual aspects of the invention it is or can be referred to one another. According to a first aspect of the invention, the problem is solved by a strip for a spar cap of a wind turbine blade. The strip is made from a composite material comprising a matrix and a reinforcement. The strip comprises a first end region and a second end region connected to one another in a longitudinal direction of the strip