Patent Description:
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 into the blade and related components. Wind turbine rotor blades generally comprise a body shell formed by two shell halves of a composite material, e.g. glass fiber composites. The body shell is relatively lightweight and has structural properties that are not designed to withstand all 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 body shell is generally reinforced with structural components, e.g. spar caps at the suction and pressure side of the blade with one or more shear webs connecting them. The spar cabs may also be called "main laminate" or "spar cap laminate" of the wind turbine blade. These terms may be used interchangeably throughout the present disclosure.

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. Composites manufactured by pultrusion may have a constant cross-section that can be easily stacked to form a larger composite part. Therefore, 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 pultrusions 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 stacks 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.

Other approaches known in the art employ intermediate or temporary supports located in the mold to receive and hold the pultruded plates delivered by a lifting device, such as a crane or similar. Then, the temporary supports are carefully removed, and the pultruded plates are lowered to the mold. This process should be carefully done in an attempt to maintain the alignment of the pultruded plates as much as possible, which is complicated to achieve along the entire length of the pultruded plates. In the case of a wind turbine blade for example, the length of the spar cap may be more than <NUM> meters, more than <NUM> meters or even more than <NUM> meters long. As indicated, these approaches are prone to misalignments between pultruded plates, and also require considerable amount of manual labor to achieve a final composite product of acceptable quality. <CIT> discloses a method for manufacturing a turbine blade comprising placing a stack of pultruded plates and a fiber mat in a mold.

Accordingly, there is a need for improved methods and systems for manufacturing composite parts comprising pultruded plates that mitigates the alignment issues associated with known approaches.

The present disclosure provides examples of assemblies and methods that at least partially overcome some of the drawbacks of existing composite molds and methods for manufacturing composite parts comprising pultrusion plates.

In a first aspect, a mold assembly is provided. The mold assembly is configured for manufacturing a composite part comprising a stack of pultruded plates and a fiber mat. The mold assembly comprises a mold surface, at least one fiber mat tensioner. The mold surface defines a longitudinal direction and a transverse direction. Further, the at least one fiber mat tensioner is configured to provide tension to the fiber mat, so that the fiber mat can hold the stack of pultruded plates at a distance from the mold.

According to this first aspect, the mold assembly allows placing and aligning the pultruded plates relative to the mold surface and can considerably reduce the need for manual supervision and labor during the manufacture of a composite part. This results in an, at least partially, automatized process with high reproducibility. At the same time, it can bring down production costs and increase the production rate of composite parts. Further, the simplicity of the mold assembly allows to both, replace an existing fiber mat or install a new fiber mat, for example in situations wherein more than one stack of pultruded plates are to be placed. Besides, the need for multiple temporary supports along the length of the mold can be reduced. Further, these can be easily mounted and dismounted from the mold assembly without interfering with the alignment of the pultruded plates.

In another aspect, a method for manufacturing a composite part is provided. The composite part comprises a stack of pultruded plates and one or more fiber mats, both having a longitudinal direction and a transverse direction. The method comprises providing tension to the fiber mats, placing the stack of pultruded plates on the tensioned fiber mats, and descending the fiber mats and the stack of pultruded plates to a mold.

According to this second aspect, the method allows placing the stack of pultruded plates on top of a fiber mat or multiple fiber mats before contacting a mold. Thus, the alignment of the pultruded plates can take place away from the mold, to later descend the fiber mat and the pultruded plates down to reach the mold. The fact that the fiber mat acts as an intermediate component between the pultruded plates and the mold allows to precisely locate pultruded plates in molds of different shapes and dimensions, i.e. with a narrow inner geometry. The fiber mat can at least partially adopt the geometry of the mold while descending, and it can provide a controlled descent down to the inner surface of the mold.

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.

Throughout the present disclosure, the term "fiber mat" may be understood as encompassing any piece of cloth of fabric comprising fibers. The fibers may be arranged in strands or rovings. The fiber may be natural or synthetic fibers and particularly may be any type of fiber suitable for fiber reinforced composites, and more particularly may be glass fibers or carbon fibers. The fibers may have a variety of different orientations e.g. the fiber mats may be uniaxial, biaxial, multi-axial or different. The fibers may be woven with different types of weaves or may be unwoven.

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.

<FIG> illustrates a conventional modern upwind wind turbine <NUM> according to the so-called "Danish concept" with a tower <NUM>, a nacelle <NUM> and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub <NUM> and three blades <NUM> extending radially from the hub <NUM>, each having a blade root <NUM> nearest the hub and a blade tip <NUM> furthest from the hub <NUM>.

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. prebent), 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 <NUM> comprises a blade shell comprising two blade shell parts or half shells, a first blade shell part <NUM> and a second blade shell part <NUM>, typically made of fiber-reinforced polymer. The wind turbine blade <NUM> may comprise additional shell parts, such as a third shell part and/or a fourth shell part. The first blade shell part <NUM> is typically a pressure side or upwind blade shell part. The second blade shell part <NUM> is typically a suction side or downwind blade shell part. The first blade shell part <NUM> and the second blade shell part <NUM> are fastened together with adhesive, such as glue, along bond lines or glue joints <NUM> extending along the trailing edge <NUM> and the leading edge <NUM> of the blade <NUM>. Typically, the root ends of the blade shell parts <NUM>, <NUM> has a semi-circular or semi-oval outer cross-sectional shape.

<FIG> is a schematic diagram illustrating a cross sectional view of an exemplary wind turbine blade <NUM>, e.g. a cross sectional view of the airfoil region of the wind turbine blade <NUM>. The wind turbine blade <NUM> comprises a leading edge <NUM>, a trailing edge <NUM>, a pressure side <NUM>, a suction side <NUM> a first spar cap <NUM>, and a second spar cap <NUM>. The wind turbine blade <NUM> comprises a chord line <NUM> between the leading edge <NUM> and the trailing edge <NUM>. The wind turbine blade <NUM> comprises shear webs <NUM>, such as a leading edge shear web and a trailing edge shear web. The shear webs <NUM> could alternatively be a spar box with spar sides, such as a trailing edge spar side and a leading edge spar side. The spar caps <NUM>, <NUM> may comprise carbon fibers while the rest of the shell parts <NUM>, <NUM> may comprise glass fibers.

<FIG> is a schematic diagram illustrating an exemplary mold system for molding a blade shell of a wind turbine blade. The mold system <NUM> comprises a first mold <NUM> and a second mold <NUM>. The first mold <NUM> is configured for manufacturing a first blade shell part of a wind turbine blade, such as an upwind shell part of the wind turbine blade (forming the suction suction). The second mold <NUM> is configured for manufacturing a second blade shell part of the wind turbine blade, such as a downwind shell part of the wind turbine blade (forming the pressure surface).

<FIG> schematically illustrates a top perspective view of a mold assembly <NUM> according to one example. The mold assembly <NUM> is configured for manufacturing a composite part <NUM> comprising a stack of pultruded plates <NUM> and a fiber mat <NUM>. Note that only the edges of the fiber mat have been illustrated, and these are represented with broken lines. The mold assembly <NUM> comprises a mold <NUM> having a longitudinal direction and a transverse direction. Further, the mold assembly <NUM> comprises at least one fiber mat tensioner <NUM> configured to provide tension to the fiber mat <NUM> to hold the stack of pultruded plates <NUM> at a distance from the mold <NUM>. In the present example, the mold assembly <NUM> comprises a plurality of fiber mat tensioners <NUM>, each comprising a roller as an actuator. The roller rolls and unrolls the fiber mat and provides tension to the fiber mat <NUM> in the transverse direction. The rollers in <FIG> are distributed in pairs, one at each side of the mold <NUM>. Doing so, each pair of rollers may also control the local position of the stack of pultruded plates <NUM> across the transverse direction; i.e. rolling the fiber mat <NUM> on one side while unrolling the fiber mat <NUM> on the other side.

In some examples, the mold assembly <NUM> may comprise a fiber mat tensioner <NUM> with other actuators such as a gripper, a plier, a chuck, or others to modify the distance of the fiber mat <NUM> and the stack of pultruded plates <NUM> to the mold <NUM>. Besides, the fiber mat tensioner <NUM> may comprise a combination of actuators to provide a more versatile control of the fiber mat <NUM>.

Further, the fiber mat tensioner <NUM> may also comprise one or more drives to drive and control the actuators, such as e.g. an electric motor. The drive may be configured to control the actuators independently from each other, in a synchronous manner, or all together with a single command sequence. The fiber mat rollers, or other actuators, may be distributed along the length of the mold in one or both sides of the mold. Further, the fiber mat rollers may have a substantially shorter length than length of the mold <NUM> or the fiber mat <NUM>, or may extend substantially along the entire length of the mold <NUM>. A plurality of shorter rollers may allow adjusting the descent following different sequences, if driven by an appropriate drive.

Although <FIG> illustrates an example wherein the pultruded plates are held by a single fiber mat <NUM>, other configurations are also possible. Even though a single fiber mat <NUM> is shown, it should be clear that this fiber mat <NUM> may comprise a stack of a plurality of fiber mats.

Moreover, a plurality of fiber mats may be located across the mold <NUM> at different longitudinal positions along the mold. Each fiber mat may be located substantially next to each other, or they may be separated from each other at a distance. For example, the mold assembly of <FIG> may include three fiber mats, one associated with each pair of fiber mat tensioners <NUM>. Thus, a pair of fiber mat tensioners <NUM> may adjust the tension of the fiber mat, and therefore distance of the pultruded plates to the mold <NUM>, independently from the others. Further, different types of fiber mats <NUM> may be used at different locations due to, for example, a desired increase in stiffness of the composite part. In examples, a first fiber mat may be a biaxial fiber mat and a second fiber mat may be a triaxial fiber mat, or a first fiber mat may be a carbon fiber mat and a second fiber mat may be a glass fiber mat.

In a later production step, the pultruded plates and the one or more fiber mats may be infused with resin e.g. epoxy resin. After curing, the composite part is obtained, wherein the fiber mats form an integral part of the composite part providing strength and stiffness. The use of fiber mats (material, weight, thickness, type) may thus be optimized along the composite part.

Additionally, <FIG> also illustrates that the mold assembly <NUM> may further comprise at least two sidewalls <NUM>, <NUM> substantially arranged in the longitudinal direction. The flanges <NUM>, <NUM> may be configured to passively guide the descent of the fiber mat <NUM> and the stack of pultruded plates <NUM>.

Further, the actuators of the mold assembly <NUM> may also comprise a clamping unit to grip and translate each end of the fiber mat <NUM> in the transverse direction relative to the mold <NUM>. In these examples, the width of the fiber mat <NUM> (in the transverse direction) may be substantially reduced, since the clamping unit may move towards the central region of the mold <NUM> while descending and towards the lateral regions of the mold <NUM> while ascending.

<FIG> illustrate different moments in a process using a mold assembly according to the present invention through the plane A-A' illustrated in <FIG>.

<FIG> illustrates a mold assembly <NUM> further comprising a fiber mat <NUM> and a stack of pultruded plates <NUM>. As previously discussed, the fiber mat <NUM> may be biaxial or triaxial, and the stack of pultruded plates <NUM> may comprise carbon fiber plates, glass fiber plates or a combination of the same.

The mold assembly <NUM> in <FIG> is in a first moment, wherein the fiber mat <NUM> has been tensioned by the fiber mat tensioners <NUM>. This tension provided by the tensioners <NUM> is sufficient to withstand the weight of the stack of pultruded plates <NUM> above the mold <NUM> at a given distance from the same. Once it is verified that the pultruded plates <NUM> are aligned, the fiber mat tensioners <NUM>, may adjust the tension provided to start the descent of the fiber mat <NUM> and pultruded plates <NUM>. In the illustrated example, this may be achieved by unrolling the actuators. If the actuators are unrolled at the same rate, the pultruded plates <NUM> will descend substantially vertically down to the mold. This considerably reduces the risk of misalignment during the lay-up process and, consequently, it reduces the manual labor required.

The mold assembly <NUM> in <FIG> is in a second moment, wherein the fiber mat <NUM> has been at least partially released from the fiber mat tensioners <NUM>. In this configuration, the stack of pultruded plates <NUM> are already resting on the mold <NUM>, with a fiber mat <NUM> as an intermediate layer. During the descent, the flanges <NUM>, <NUM> may be used as a reference to guide the pultruded plates <NUM>.

The mold assembly <NUM> in <FIG> may be configured for manufacturing a wind turbine blade shell component comprising a spar cap and a fiber mat <NUM>.

Even though in all the depicted examples, the pultruded plates <NUM> 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. in any of the depicted examples, a single pultruded plate <NUM> may in reality comprise a plurality of plates (or "strips") next to each other.

<FIG> is a flow diagram of an example of a method <NUM> for manufacturing a composite part. The composite part comprises a stack of pultruded plates <NUM> and a fiber mat <NUM>, and both the stack of pultruded plates <NUM> and the fiber mat <NUM> have a longitudinal direction and a transverse direction. In particular, <FIG> shows that the method <NUM> comprises, at block <NUM>, providing tension to the fiber mat <NUM>. Further, the method <NUM>, at block <NUM>, comprises placing the stack of pultruded plates <NUM> on the tensioned fiber mat <NUM>. Besides, the method <NUM> also comprises, at block <NUM>, descending the fiber mat <NUM> and stack of pultruded plates <NUM> to a mold <NUM>.

According to this aspect, the method <NUM> allows to place the stack of pultruded plates <NUM> on an intermediate layer, i.e. the fiber mat <NUM>. The fiber mat <NUM> allows positioning the stack of pultruded plates with lifting equipment, and considerably reducing dimensional restrictions. Thus, once the stack of pultruded plates <NUM> are received and held by the fiber mat <NUM>, both the fiber mat <NUM> and the stack of pultruded plates <NUM> can descend down to the mold <NUM>. Again, since the fiber mat <NUM> can at least partially adopt the geometry of the mold <NUM>, misalignments during the descent are considerably reduced.

In some examples, providing tension to the fiber mat <NUM> may be carried out by pulling the fiber mat <NUM> over the mold <NUM>, either directly against the lateral edges of the mold <NUM> or against a guide, i.e. sidewall, placed in the mold <NUM>.

In examples, the method <NUM> may also comprise infusing the fiber mat <NUM> and stack of pultruded plates <NUM> with resin. To infuse the resin, vacuum may be used, e.g. in a VARTM process (Vacuum Assisted Resin Transfer Molding). A vacuum bag may be used.

Additionally, the method <NUM> may also include aligning the stack of pultruded plates <NUM> between at least two sidewalls located in the mold <NUM>. The sidewalls may form part of the mold for a subsequent resin infusion. Alignment may be done by an actuator such as a roller, a chuck, a gripper or other. In case of having rolling elements, the alignment of the stack of pultruded plates <NUM> may be achieved by adjusting the rolling and unrolling rates of the rolling elements, as previously discussed in relation to the mold assembly <NUM>. In alternative examples, the rollers may be used as guiding devices, i.e. the tension is applied by an actuator, and one or more rollers are used to guide the fiber mat over the mold.

If other actuators such as grippers are used, the actuators may translate the fiber mat <NUM>, and pultrusion plates <NUM> on it, along the transverse direction of the mold <NUM>. Therefore, in examples, descending the fiber mat <NUM> and stack of pultruded plates <NUM> may comprise at least partially releasing the fiber mat <NUM> from a fiber mat holder.

The method <NUM> may also comprise trimming the fiber mat <NUM> along the longitudinal direction. Trimming may be carried out manually by qualified operators, semi-automatically or in a fully automatized process. Additionally, the trimming operation may be done prior to infusing the fiber mat <NUM> and stack of pultruded plates <NUM> with resin.

In some examples, alternatively or additionally to the trimming, the method <NUM> may comprise folding the extra width of the fiber mat <NUM> on top of the stack of pultruded plates <NUM>.

In some examples, descending the fiber mat <NUM> and the stack of pultruded plates <NUM> comprises descending a first portion of the fiber mat <NUM> and the stack of pultruded plates <NUM> at a first point in time and descending a second portion of the fiber mat <NUM> and the stack of pultruded plates <NUM> at a second point in time. This can be achieved, for example, by assigning a descend command to an actuator (or a pair of actuators as discussed in <FIG>), while the remaining actuators do not modify their state or modify their state at a different rate. Thus, once a portion of the fiber mat <NUM> is descending, a second actuator may start the descent of the associated portion of the fiber mat <NUM>. Note that the same applies in case of having multiple fiber mats <NUM> distributed in different locations along the longitudinal direction of the pultrusion stack <NUM>.

<FIG> is a flow diagram of an example of a method <NUM> for manufacturing a spar cap of a wind turbine blade. The spar cap component comprises a stack of pultruded plates <NUM> and a fiber mat <NUM>, and both the stack of pultruded plates <NUM> and the fiber mat <NUM> have a longitudinal direction and a transverse direction. In particular, <FIG> shows that the method <NUM> according to this example comprises, at block <NUM>, providing tension to the fiber mat <NUM>. Further, the method comprises placing the stack of pultruded plates <NUM> on the tensioned fiber mat <NUM> at block <NUM>. The method <NUM> also comprises, at block <NUM>, descending the fiber mat <NUM> and stack of pultruded plates <NUM> to a mold.

The stack of pultruded plates <NUM> may comprise additional layers of material such as layers of interlayer material, i.e. glass or carbon fiber fabrics, hybrid fabrics or suitable fiber veils, between pultruded plates. Additionally, the stack of pultruded plates <NUM> may also comprise components of a lightning protection system such as a network of conductors. Further, in some examples, an additional layer may be used to cover top, bottom and side surfaces of the stack of pultruded plates <NUM>. This additional layer may be a biaxial glass or carbon fiber, a chop strand mat (CSM) or any other suitable material.

Claim 1:
A method (<NUM>) for manufacturing a composite part (<NUM>) comprising a stack of pultruded plates (<NUM>) and a fiber mat (<NUM>), the stack of pultruded plates (<NUM>) and the fiber mat (<NUM>) having a longitudinal direction and a transverse direction, the method (<NUM>) characterized in comprising:
providing (<NUM>) tension to the fiber mat (<NUM>);
placing (<NUM>) the stack of pultruded plates (<NUM>) on the tensioned fiber mat (<NUM>); and
descending (<NUM>) the fiber mat (<NUM>) and stack of pultruded plates (<NUM>) to a mold (<NUM>).