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EP-3693156-B1 - A METHOD OF MANUFACTURING A WIND TURBINE BLADE

EP3693156B1EP 3693156 B1EP3693156 B1EP 3693156B1EP-3693156-B1

Inventors

  • NIELSEN, LARS
  • Jespersen, Klavs

Dates

Publication Date
20260506
Application Date
20190207

Claims (12)

  1. A method of manufacturing a wind turbine blade, the blade having a profiled contour including a pressure side and a suction side, and a leading edge and a trailing edge with a chord having a chord length extending therebetween, the wind turbine blade extending in a spanwise direction between a root end and a tip end, said method comprising: - providing a mould (66), - arranging one or more layers of fibre material in the mould for providing an outer shell part (70), - injecting the one or more layers of fibre material with a curable resin, and - curing the resin to obtain an outer shell part (70), - arranging a resin flow medium (76) on top of at least part of the outer shell part (70) followed by one or more layers of fibre material for forming a load-carrying structure (74), - injecting the resin flow medium (76) and the one or more layers of fibre material for forming a load-carrying structure with a curable resin, and - curing the resin to adhere the outer shell part (70) to the load-carrying structure (74) to obtain a shell half of a wind turbine blade wherein the resin flow medium (76) comprises a curing inhibitor.
  2. A method according to claim 1, wherein the curing inhibitor covers at least a first part of the outer surface of the resin flow medium.
  3. A method according to any of the preceding claims, wherein the resin flow medium further comprises a curing promoter and wherein the curing promoter covers at least a second part of the outer surface of the resin flow medium, which is different from the first part.
  4. A method according to any of the preceding claims, wherein the curing inhibitor is uniformly coated on the surface of the resin flow medium.
  5. A method according to any of the preceding claims, wherein the thickness of the resin flow medium varies spatially across the resin flow medium.
  6. A method according to any of the preceding claims, wherein the curing inhibitor concentration varies spatially across the resin flow medium.
  7. A method according to any of the preceding claims, wherein the curing inhibitor concentration varies within one or more layers of the resin flow medium.
  8. A method according to any of the preceding claims, wherein the curing promoter comprise a transition metal such as cobalt, manganese, iron or copper or mixtures thereof.
  9. A method according to any of the preceding claims, wherein the curing inhibitor is a primary antioxidant (radical scavenger).
  10. A method according to any of the preceding claims, wherein the resin is a styrene based resin or polyester based resin comprising styrene, such as an unsaturated polyester.
  11. A method according to any of the preceding claims, wherein the curing of the resin is performed without external heating.
  12. A wind turbine blade obtainable by the method of any of claims 1-11.

Description

Field of the invention The present invention relates to a method of manufacturing a wind turbine blade resulting in fewer manufacturing defects using a two-step curing process and a resin flow medium comprising an inhibitor. The first curing step forms an outer shell part followed by a second curing step forming a load carrying structure, wherein the second curing step utilizes a resin flow medium coated with a cure inhibitor. Background of the invention The rotor blades of modern wind turbines capture kinetic wind energy by using sophisticated blade design created to maximise efficiency. A major trend in wind turbine development is the increase in size to reduce the leveraged cost of energy. There is an increasing demand for large wind blades which may exceed 80 metres in length and 4 metres in width. The blades are typically made from a fibre-reinforced polymer material and comprise a pressure side shell half and a suction side shell half. The cross-sectional profile of a typical blade includes an airfoil for creating an air flow leading to a pressure difference between both sides. The resulting lift force generates torque for producing electricity. The shell halves of wind turbine blades are usually manufactured using blade moulds. First, a blade gel coat or primer is applied to the mould. Subsequently, fibre reinforcement and/or fabrics are placed into the mould followed by resin infusion. The resulting shell halves are assembled by being glued or bolted together substantially along a chord plane of the blade. In most cases, wind turbine rotor blades are made in large parts, e.g., as two aeroshells with a load-carrying box (spar) or internal webs that are then bonded together. Vacuum infusion or VARTM (vacuum assisted resin transfer moulding) is one method, which is typically employed for manufacturing composite structures, such as wind turbine blades comprising a fibre-reinforced matrix material. During the manufacturing process, liquid polymer, also called resin, is filled into a mould cavity, in which fibre material has been arranged, and where a vacuum is generated in the mould cavity hereby drawing in the polymer. The polymer can be thermoset plastic or thermoplastics. Typically, uniformly distributed fibres are layered in a first rigid mould part, the fibres being rovings, i.e. bundles of fibres arranged in mats, felt mats made of individual fibres or unidirectional or woven mats, i.e. multi-directional mats made of fibre rovings, etc. In order to form a laminate that is thick by the root and gradually becomes thinner towards the tip, most plies run from the root only partly toward the tip. A second mould part, which is often made of a resilient vacuum bag, is subsequently placed on top of the fibre material and sealed against the first mould part in order to generate a mould cavity. By generating a vacuum, typically 80 to 95% of the total absolut vacuum, in the mould cavity between the first mould part and the vacuum bag, the liquid polymer can be drawn in and fill the mould cavity with the fibre material contained herein. Resin transfer moulding (RTM) is another manufacturing method, which is similar to VARTM. In RTM the liquid resin is not drawn into the mould cavity due to a vacuum generated in the mould cavity. Instead the liquid resin is forced into the mould cavity via an overpressure at the inlet side. Currently, vacuum assisted resin transfer molding (VARTM) is the most common manufacturing method for manufacturing of wind turbine rotor blades. When producing large blades, the main laminate gets proportionally larger, also in terms of its overall volume. Since such parts usually have a comparatively low thickness towards their edges this may lead to problems during curing. In particular, this may lead to undesired differences in curing temperatures within the main laminate. Thinner parts of the element may not receive significant exotherm heat, thus not heating up as much as thicker, central parts of the reinforcing element. This may lead to manufacturing defects within the part as the degree and timing of shrinkage during the curing process may vary spatially, i.e. the degree and timing of shrinkage in the thicker parts may be different from the degree and timing of shrinkage in the edge portions. Thus, manufacturing defects may arise during curing due to volume shrinkage of the cured resin. This is especially a problem with styrene-based resins, such as unsaturated polyester resins mixed with styrene, which undergo a significant volume shrinkage. The shrinkage will be evident as deformation, internal stress or cracks in the laminate after curing and demolding. Furthermore, it may be a challenge to avoid the formation of wrinkles at double-curved areas and at areas with un-wetted fibers where air bubbles can be entrapped in the bondlines. A major issue may also be that many of these damage modes are not easily detectable since the damage do not necessarily originate from the external sur