Patent Application
20250100237
The present application claims priority from European patent application EP 22159824.6 “Mold assembly for infusing a spar cap and related methods” filed on Mar. 2, 2022.
The present disclosure relates to mold assemblies for infusing a spar cap comprising a stack of pultruded plates, and methods for infusing the same.
Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation generates a torque that is normally transmitted through a rotor shaft to a generator, either directly (“directly driven”) or through the use of a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid.
In order to extract more energy from the wind, the size of the rotor diameter is increased by increasing the dimensions of the wind turbine blades. The larger size of the blades introduces higher physical loads to the blade and related components. Wind turbine rotor blades generally comprise a body shell formed by two shell haves of a composite material. The body shell is relatively lightweight and has structural properties that are not designed to withstand the bending moments and other loads acting on the blade during operation. To improve the structural properties of the rotor blade such as stiffness and strength, the blade is generally reinforced with structural components, e.g. one or more spar caps at the suction and pressure side of the blade with a shear web connecting them.
The spar caps can be manufactured using several materials such as glass fiber laminate composites and carbon fiber laminate composites. Modern spar caps may be manufactured using pultruded composites, particularly carbon fiber based pultruded composites. Composites manufactured by pultrusion may have a constant cross-section that can be easily stacked to form a larger composite part. They may be referred to as pultruded “plates”. A plurality of pultruded plates may be stacked and infused together in a mold to form a larger (i.e. longer, thicker, wider) composite part, e.g. a spar cap.
Due to the benefits of using pultruded plates for the manufacture of composite parts in terms of cost and others, the industry is developing new approaches to integrate them in composite manufacturing processes. Known approaches include the placement of pultruded plates in a mold to later infuse them. However, the pultruded plates may be difficult to align with respect to each other and to the mold, and this may lead to imperfections in the final product. To mitigate the aforementioned misalignments, a considerable amount of manual labor is required, which leads to an increase in the average cost of the composite part and a reduction in the overall composite manufacture throughput.
Further, approaches known in the art employ supports located in the mold to guide the pultruded plates coming from, for example, a lifting device, such as a crane or similar. After resin infusion and unmolding, the resin infused stack of pultruded plates may need to be treated by qualified operators to improve the quality of the product and e.g. remove excess resign. This results in a time-consuming and complex task that requires manual labor and hinders the production rate and quality of the final product.
The present disclosure provides examples of assemblies and methods that at least partially overcome some of the drawbacks of existing molds for spar cap manufacturing and methods for manufacturing spar caps comprising pultrusion plates.
In a first aspect, a mold assembly is provided. The mold assembly is configured for manufacturing a spar cap comprising a stack of pultruded plates. The mold assembly comprises a mold surface having a longitudinal direction and a transverse direction, and at least two sidewalls. The sidewalls are arranged substantially in the longitudinal direction. Further, at least one of the sidewalls is configured to be adjusted along a transverse direction of the mold surface.
According to this first aspect, the mold assembly allows placement of the pultruded plates relative to the mold surface and to align the pultruded plates by adjusting the position of at least one sidewall along a transverse direction. Therefore, the mold assembly considerably reduces manual supervision and labor during the positioning and alignment of the pultruded plates. This results in a, at least, partially automatized process with high reproducibility. At the same time, it brings down production costs and increases the production rate of composite parts. Moreover, a draft angle which is usually employed for placement of the pultruded plates and for unmolding of the resin infused component may be reduced or eliminated. There will thus be less excess of resin on the side of the components, requiring less labor afterwards.
Further, the fact that at least one sidewall can be adjusted allows the use of the same mold assembly for pultruded plates of different dimensions. Further, said sidewall aids on the unmolding step after resin infusion, e.g. the sidewall may be move away from the spar cap to ease the collection of the same.
In another aspect, a method for manufacturing a spar cap comprising a stack of pultruded plates is provided. The method comprises laying the stack of pultruded plates between a first and a second sidewall on a mold surface. Further, the method comprises infusing the stack of pultruded plates with resin and unmolding the infused stack of pultruded plates from the mold. Additionally, at least one of the sidewalls is adjusted along the transverse direction relative to the stack of pultruded plates at least after the laying or prior the unmolding of the stack of pultruded plates.
According to this aspect, the method allows placing the stack of pultruded plates in a mold and then displacing a sidewall relative to the stack of pultruded plates. Thus, the alignment of the pultruded plates can occur during the translation of the sidewall. Further, the fact that a sidewall can be moved allows manufacturing spar cap with different dimensions, e.g. widths and can reduce the draft angle usually employed for unmolding. The sidewall(s) can be translated after infusing the stack of pultruded plates with resin, which simplifies considerably the unmolding process and reduces the risk of damaging the spar cap during extraction.
Throughout this disclosure, the terms “pultruded composites”, “pultruded plates”, “pultrusions” or similar terms are generally used to define reinforced materials (e.g. fibers or woven or braided strands) that are impregnated with a resin and pulled through a heated die such that resin cures.
Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which:
Reference now will be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation only, not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.
The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 may be constant along the entire root area 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.
A shoulder 40 of the blade 10 is defined as the position, where the blade 10 has its largest chord length. The shoulder 40 is typically provided at the boundary between the transition region 32 and the airfoil region 34.
It should be noted that the chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub. The wind turbine blade 10 comprises a blade shell comprising two blade shell parts or half shells, a first blade shell part 24 and a second blade shell part 26, typically made of fiber-reinforced polymer. The wind turbine blade 10 may comprise additional shell parts, such as a third shell part and/or a fourth shell part. The first blade shell part 24 is typically a pressure side or upwind blade shell part. The second blade shell part 26 is typically a suction side or downwind blade shell part. The first blade shell part 24 and the second blade shell part 26 are fastened together with adhesive, such as glue, along bond lines or glue joints 28 extending along the trailing edge 20 and the leading edge 18 of the blade 10. Typically, the root ends of the blade shell parts 24, 26 has a semi-circular or semi-oval outer cross-sectional shape.
In the illustrated example, only one of the sidewalls 221 can be adjusted, but in other examples both sidewalls 221, 222 could be adjustable. Note that in the present example the stack of pultruded plates 211 has been illustrated elevated with respect to the mold surface 210, as if the stack of pultruded plates 211 was still descending down to the mold 200. Once the pultruded plates 211 have been positioned in the mold, the (final) adjustment of the sidewalls of the mold may occur.
Also referring to
In examples, the sidewalls of the mold may be substantially parallel to each other i.e. the draft angle may be 0°. After resin infusion, the adjustable sidewall(s) may be displaced in the transverse direction to allow unmolding.
In examples, at least one of the sidewalls 211 may comprise a sliding element configured to slide along the guide 225 in the transverse direction. The sliding element and guide 225 may define a low friction coupling to promote a smooth adjustment. Besides, said sidewalls 211 may also comprise a clamping or fixing element to secure the position of the sidewall 211 along the guide, as for example a locking lever. The clamping (or fixing) element may be manual or automatic.
In further examples, the mold assembly 200 may further comprise a drive unit configured to adjust at least one of the sidewalls 221 along the transverse direction. The drive unit may be operated autonomously or by a qualified operator. The drive unit may comprise pneumatic, and/or hydraulic, and/or electronic components, such as for example, pistons, pumps, encoders, stepper motors, and others. Thus, the drive unit may displace the sidewalls 221, 222 prior to laying the stack of pultruded plates to provide more room for the descent of the same. In other examples, the drive unit may displace the sidewalls 221, 222 after laying the stack of pultruded plates to secure them and align them relative to each other and to the mold 220. Additionally, the mold assembly 200 may comprise a sensor unit configured to determine the pressure exerted by at least one of the sidewalls 221, 222 to the stack of pultruded plates 211. The sensor unit may feed the driver so that it stops the displacement after reaching a giving pressure threshold. Additionally, the sensor unit may also comprise a processing and control unit that process the data from the sensor and provides controlling parameters to the driver.
In alternative examples, adjusting the sidewall(s) may be a manual process.
Additionally,
The receptacles 224 and corresponding fasteners 223 may provide a threaded connection, but other couplings can also be employed. In some examples, the sidewalls 221, 222 may have elongated holes to receive the sidewall fasteners 223. The elongated holes may provide a variable positioning of the sidewall 211 with respect to the mold surface 210. In other examples, the receptacles in the mold 220 may be elongated and the fasteners 223 may be introduced in them at a desired transverse position.
Note that although the sidewalls 221, 222 have been represented as L profiles, these may have any other suitable cross-section.
In examples, the infused stack 201 comprises a plurality of pultruded plates 211 infused with resin. The stack of pultruded plates 211 may comprise carbon fiber, glass fiber, aramid fiber or other suitable fibers. Besides, the infused stack of pultruded plates 201 may comprise epoxy resin, polyester resin, vinylester resin or other suitable resins.
As illustrated in
In both these examples, the draft angle of the sidewalls may have been 0° or close to 0°. Resin build-up on the sides of the stacks may thus be avoided. This can reduce the weight of the product and can also reduce the need for post-processing. Additionally, a draft angle of 0° or close to 0° may also reduce the cost of other components adjacent to the pultrusion stack 201. For example, core panels that are configured to be assembled next to the pultrusion stack 201 may be cut with straight angles that substantially match the sidewalls of the pultrusion stack 201. This may result in a faster and cheaper manufacturing process.
In some examples, the infused pultrusion stacks 201 may be obtained by a method that will be further discussed in relation with
During method 300 at least one of the sidewalls 221, 222 may adjusted along the transverse direction relative to the stack of pultruded plates 211. This may take place at least after the laying 301 of the pultruded plates 211 or prior the unmolding 303 of the stack of pultruded plates 211.
The adjustment of at least one of the sidewalls 221, 222 may be done according to any of the examples herein previously illustrated.
As previously discussed, the fact that at least one of the sidewalls 221, 222 is adjusted along the transverse direction greatly simplifies the placement of the stack of pultruded plates 211 (both by potentially guiding the descent and by providing more room for the plates) and the unmolding. In fact, in some examples adjusting at least one of the sidewalls 221, 222 is performed by displacing said sidewall 221, 222 in the transverse direction and subsequently fastening said sidewall 221, 222 to a receptacle in the mold 220 prior to infusing 302 the stack of pultruded plates 211 with resin.
In some examples, the method 300 comprises laying 301 the stack of pultruded plates 211 substantially adjacent to the first sidewall 222, the first sidewall 222 being fixed in the mold 220, and the method 300 further comprises adjusting the second sidewall 221 in the transverse direction to contact the stack of pultruded plates 211. This results in an improved alignment of the pultruded plates 211 and therefore increases the quality of the final product. Additionally, the sidewalls 221, 222 may define a draft angle smaller than 1 degree, specifically smaller than 0.5 degrees, more specifically a draft angle of approximately 0 degrees. This draft angle limits the accumulation of resin between the sidewall 221, 222 and the lateral surfaces of the pultruded plates 211, which reduces considerably the amount of post-molding surface treatment that may be required. In other examples, the sidewalls 221, 222 may be fixed in the mold at a given location and defining a large draft angle to ease the guiding of the stack of pultruded plates 211. Then, prior to infusing 302, the draft angle may be reduced by rotating a sidewall surface 226.
In examples, the sidewalls 221, 222 may be substantially parallel to each other. Since the mold 220 may have a curved geometry and the sidewalls 221, 222 may be displaced along the surface of the mold 210, the sidewalls 221, 222 may be further adjusted by rotating a sidewall surface 226 configured to contact the stack of pultruded plates 211. The rotation of the sidewall surface 226 may be about the longitudinal direction of the mold surface 210.
As discussed with respect to
In yet a further aspect of the present disclosure, a wind turbine blade is provided. The wind turbine blade comprises a shear web and spar caps, wherein the spar caps comprise an infused stack of pultruded plates 201 according to any of the examples illustrated herein, and/or manufactured according to any of the examples illustrated herein. The upwind and downwind shell of the wind turbine blade may be made e.g. in accordance with the process illustrated in
Note that some of the technical features described in relation with the mold assembly 200 and infused pultrusion stack 201 can be included in the method 300 for manufacturing a spar cap, and vice versa.
Even though in all the depicted examples, the pultruded plates 211 are shown as thin, wide and long plates, which are stacked on top of each other, it is noted that this is done for illustration purposes only. I.e. in any of the depicted examples, a single pultruded plate 211 may in reality comprise a plurality of plates (or “strips”) next to each other.
This written description uses examples to disclose the present teaching, including the preferred embodiments, and also to enable any person skilled in the art to practice it, including making and using any devices or systems and performing any incorporated methods. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspects, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22159824.6 | Mar 2022 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/055149 | 3/1/2023 | WO |
