Patent Description:
Wind power provides a clean and environmentally friendly source of energy. Wind turbines usually comprise a tower, generator, gearbox, nacelle, and one or more rotor blades. The wind turbine blades capture kinetic energy of wind using known airfoil principles. Modern wind turbines may have rotor blades that exceed <NUM> meters in length.

Wind turbine blades are usually manufactured by forming two shell parts or shell halves from layers of woven fabric or fibre and resin. Spar caps, which are also called main laminates, are placed or integrated in the shell halves and may be combined with shear webs or spar beams to form structural support members. Spar caps or main laminates may be joined to, or integrated within, the inside of the suction side and pressure side halves of the shell.

As the size of wind turbine blades increases, various challenges arise from such blades being subjected to increased forces during operation, requiring improved reinforcing structures. In some known solutions, pultruded fibrous strips of material are used. Pultrusion is a continuous process in which fibres are pulled through a supply of liquid resin and then heated in an open chamber where the resin is cured. Such pultruded strips can be cut to any desired length.

<CIT> discloses a shaping device for producing a T-rod for a rotor blade of a wind turbine, which has a web support section and at least one T-shaped web foot section provided at one end of the web support section, wherein the shaping device comprises a main shape and at least one insert.

<CIT> discloses a fixing device for fixating a segment of a wind turbine blade to a mold, wherein the blade segment has a fixating portion. The fixing device comprises: a first portion for removably fixating the blade segment at its fixating portion to the mold and a second portion for fixating the fixing device to the mold.

<CIT> discloses a method for manufacturing a composite material article, comprising providing a mould, placing at least one layer of bulk fiber material on the mould, placing, at an edge of the bulk fiber material layer, a flange element partially overlapping the bulk fiber material layer, and partially extending so as to form a flange, and curing bulk resin on the mould.

<CIT> relates to a method of manufacturing an aerodynamic shell part for a wind turbine blade, comprising providing a first mould part, laying up fibre-reinforcement material and optionally also sandwich core material in the first mould, arranging one or more inserts having an exterior shape corresponding to at least sides of the recess of the aerodynamic shell part, and supplying resin to said fibre-reinforcement material and optional sandwich core material.

However, the manufacturing of large reinforcing structures, such as spar caps, can be challenging. In particular, many limitations still exist in the ability to stay within required tolerances during known processes for manufacturing spar caps. Also, some known spar cap moulding methods are quite tedious and ineffective, and may result in undesired damage to the pultruded elements when demoulding the spar cap from the spar cap mould. Other potential problems include wrinkle formation, unsatisfactory resin impregnation or air pockets formed during known moulding processes for forming spar caps.

It is therefore an object of the present invention to provide an improved method of manufacturing a spar cap for a wind turbine blade, which is more efficient and less time-consuming.

It is another object of the present invention to provide an improved method of manufacturing a spar cap for a wind turbine blade, which leads to less damage of the spar cap.

It is another object of the present invention to provide an improved method of manufacturing a spar cap for a wind turbine blade that minimises wrinkle formation, unsatisfactory resin impregnation or air pockets formed during the manufacturing process.

It has been found that one or more of the aforementioned objects can be obtained by providing a method of manufacturing a fibre-reinforced spar cap for a wind turbine blade, the method comprising the steps of providing a mould, fastening a first guide member and a second guide member to the mould for providing a moulding cavity in between the first and second guide members, arranging a fibre material within the moulding cavity, such that a first gap is provided between the fibre material and the first guide member, and a second gap is provided between the fibre material and second guide member, placing a vacuum foil over the fibre material and the first and second guide members, such that the vacuum foil extends into the first and second gap, inserting a first insert into the first gap on top of the vacuum foil, inserting a second insert into the second gap on top of the vacuum foil, infusing resin into the fibre material to form a fibre-reinforced polymer, curing the resin-infused fibre material to form the fibre-reinforced spar cap, removing the first and second inserts and the vacuum foil, and demoulding the fibre-reinforced spar cap from the mould.

It was found that this solution allows for less tight tolerance requirements for the mould and the guide members, leading to faster production cycles and easier handling. In particular, it was found that the method of the present invention results in a considerably facilitated demoulding step of the spar cap, thus reducing damage to the spar cap.

The wind turbine blade usually has 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. Usually, one or more spar caps can be installed in the pressure side shell half and in the suction side shell half of the blade, and a flapwise extending shear web can be arranged in between the opposing spar caps of the two shell halves. Usually, the pressure side shell half and the suction side shell half are manufactured over the entire length of the wind turbine blade, i.e. over their entire final length. The pressure side shell half and the suction side shell half will typically be adhered or bonded to each other near the leading edge and near the trailing edge. Each shell half may comprise longitudinally/spanwise extending spar caps, also called main laminates, preferably comprising reinforcement fibres such as glass fibres, carbon fibres, aramid fibres, metallic fibres, such as steel fibres, or plant fibres, or mixtures thereof. The shell halves will typically be produced by infusing a fibre lay-up of fibre material with a resin such as epoxy, polyester or vinyl ester. The spar caps or main laminates are usually affixed to the inner faces of the shell halves.

Typically, the spar cap, or the fibre material arranged in the spar cap mould prior to resin infusion, has a longitudinally extending top surface and an opposing longitudinally extending bottom surface, and first and second longitudinally extending lateral surfaces. The distance between the top and bottom surface usually defines the thickness of the spar cap. The top and bottom surfaces of the spar cap are typically vertically separated, whereas the first and the second lateral surfaces are transversely separated. The spar cap can have the shape of a rectangular plate or a slab. The spar cap usually has a rectangular shaped cross-section when sectioned normally to the longitudinal or spanwise extension.

It is preferred that the spar cap of the present invention comprises a plurality of strips of pultruded fibre material, extending generally in a longitudinal/spanwise direction of the spar cap. The pultruded strips of the spar cap preferably have a length of at least <NUM> meters, such as at least <NUM> meters, or at least <NUM> meters. In some embodiments, each strip contains a carbon fibre material. In other embodiments, each strip contains a glass fibre material. In other embodiments, each strip contains a glass fibre material and a carbon fibre material. In some embodiments, the strips may not contain any polymer when laying up the strips in the spar cap mould.

The mould is typically a spar cap mould having an upper surface including a moulding surface. Usually, the mould will extend along a longitudinal direction, with a length of at least <NUM> meters. The mould may be made of or comprise a composite material and/or may comprise a metal material. The first guide member and the second guide member are fastened, preferably releasably fastened, to the mould for providing a moulding cavity in between the first and second guide members. The first guide member may extend in the longitudinal direction of the mould closer to a first edge of the mould, and the second guide member may extend in the longitudinal direction of the mould closer to the second edge of the mould. It is preferred that the first and second guide members extend along the longitudinal direction of the mould, substantially parallel to each other. For example, the first guide member may extend along a first lateral edge of the spar cap or fibre material, the first lateral edge of the spar cap or fibre material facing the trailing edge of the blade when arranged in the blade shell, and the second guide member may extend along a second lateral edge of the spar cap or fibre material, the second lateral edge of the spar cap or fibre material facing the leading edge of the blade when arranged in the blade shell. In a preferred embodiment, the first guide member and the second guide member are guide rails.

In a preferred embodiment, each guide member comprises an upstand, such as an upright structure or substantially vertically extending structure, forming the longitudinally extending guide surface. In a preferred embodiment, each of the guide members has a substantially L-shaped cross section, or a skewed or compressed L-shaped cross section. In another preferred embodiment, the guide members have a triangular cross section. In other embodiments, the guide members have a prism cross section. It is preferred that each guide member has substantially horizontal section, which can be fastened to the mould, and a substantially vertical section extending from the mould in a substantially vertical or upward direction. In other embodiments, each of the guide members has a triangular cross section.

In a preferred embodiment, the first and second guide members extend along the longitudinal direction of the mould, preferably substantially parallel to the lateral edges of the mould. Thus, it is preferred that the first and second guide members extend along substantially the entire length of the mould, and preferably along substantially the entire length of the spar cap. In some embodiments, the insert may have a length of at least <NUM> meters, such as at least <NUM> meters or at least <NUM> meters. In a preferred embodiment, the first and second guide members are bolted to the mould. Thus, one or more bolts can be inserted into each guide member, preferably extending into receiving holes in the mould. In other embodiments, the guide members can be fastened to the mould by one or more screws, adhesives, snap connections, or other fastening means.

In a preferred embodiment, the transverse distance between the first and second guide members is at least <NUM> metre, such as at least <NUM> metres or at least <NUM> meters. Usually, the transverse distance between the two guide members at the moulding surface should accommodate more than the width of the spar cap to be manufactured, such as at least an additional <NUM>% or an additional <NUM>% as compared to the width of the spar cap or fibre material arranged in between the guide members.

A fibre material is arranged within the moulding cavity, usually in between and along the first and second guide members, such that a first gap is provided between the fibre material and the first guide member, preferably at the moulding surface, and a second gap is provided between the fibre material and second guide member, preferably at the moulding surface. It is preferred that the respective gaps increase in width when moving from the moulding surface in an upward directions. Thus, the respective gaps may be substantially V-shaped or substantially wedge-shaped. In some embodiments, the transverse distance between the fibre material and the respective guide member is between <NUM> and <NUM>, preferably between <NUM> and <NUM>, at the moulding surface. The transverse distance between the fibre material and the respective guide member preferably increases when moving upwardly from the moulding surface. At the top surface of the fibre material, the transverse distance between the fibre material and the respective guide member is preferably between <NUM> and <NUM>, such as between <NUM> and <NUM>.

The fibre material may comprise dry fiber fabrics, prepreg fiber materials and/or pultruded rods or strips of fibre material, such as one or more strips of carbon fibre pultrusions. In a preferred embodiment, the fibre material comprises a plurality of strips of fibre material arranged into adjacent stacks of strips. Each stack of strips may comprise <NUM>-<NUM>, such as <NUM>-<NUM> strips, e.g. strips of pultruded fibre material, successively arranged on top of each other. Thus, each stack will usually extend in a longitudinal/spanwise direction of the spar cap. In a preferred embodiment, the strips comprise pultruded strips, preferably pultruded strips comprising a fibre material, preferably carbon fibres.

In a preferred embodiment, the first guide member comprises a longitudinally extending guide surface, and the second guide member comprises a longitudinally extending guide surface facing the guide surface of the first guide member, the guide surface of the first guide member diverging from the guide surface of the second guide member in an upward direction. It is thus preferred that the respective guide surfaces together form a funnel shape towards the moulding surface. In other words, the guide surface of the first guide member may diverge from the guide surface of the second guide member in an upward direction, the planes in which the respective guide surfaces <NUM>, <NUM> lie forming an angle. Said angle is preferably not larger than <NUM>°, more preferably not larger than <NUM>°.

In a preferred embodiment, the spar cap has first and second longitudinally extending lateral surfaces, wherein the first guide member comprises a longitudinally extending guide surface forming an acute angle with the first lateral surface of the spar cap, and wherein the second guide member comprises a longitudinally extending guide surface forming an acute angle with the second lateral surface of the spar cap. Said respective acute angles are preferably not larger than <NUM>°.

A vacuum foil is placed over the fibre material and the first and second guide members, such that the vacuum foil extends into the first and second gap. Thus, the vacuum foil is preferably arranged between the guide members and the fibre material, held in place by the inserts. The vacuum foil may be any vacuum-tight film. Lateral sealing of the moulding cavity can be ensured by applying an adhesive film or roll at the side of the mould, such as tacky tape.

A first insert is inserted into the first gap on top of the vacuum foil, and a second insert is inserted into the second gap on top of the vacuum foil. Thus, typically the vacuum foil will be pushed into the respective gaps when inserting the inserts, such that the inserts are placed above the vacuum foil, i.e. outside of the moulding cavity into which resin is infused. It is particularly preferred the first and second inserts are rigid inserts. The inserts are preferably wedge-shaped, i.e. tapering to a thin edge at one end thereof. The inserts can be made of a polymer material, e.g. a polymer material comprising silicone. In one embodiment, the inserts are <NUM>-d printed. In a preferred embodiment, each insert comprises a silicone material. In a preferred embodiment, each insert comprises high density polyethylene (HDPE) and a silicone material. In a preferred embodiment, the insert is substantially wedge-shaped. In a preferred embodiment, the insert has a triangular cross section or a trapezoid cross section. Thus, in some embodiments, the insert may have a length of at least <NUM> meters, such as at least <NUM> meters or at least <NUM> meters, with a triangular or trapezoid cross section. In a preferred embodiment, the inserts extend along substantially the entire length of the spar cap. It is preferred that the insert tapers towards one end as seen in its cross section. The tapered end of the insert is preferably the end that is inserted into the gap.

In a preferred embodiment, the first insert is squeezed into the first gap, and the second insert is squeezed into the second gap. This will typically be done by a substantially vertical, downward movement of the rigids into the respective gap. Advantageously, thereby the vacuum foil is squeezed into the respective gaps.

Resin, for example an epoxy resin, is infused into the fibre material to form a fibre-reinforced polymer, followed by curing the resin-infused fibre material to form the fibre-reinforced spar cap, and removing the first and second inserts and the vacuum foil. The resin infusion is step is preferably performed by Vacuum Assisted Resin Transfer Moulding (VARTM), wherein the vacuum foil or vacuum bag is arranged on top of the fibre material, sealing against the mould, thereby forming a mould cavity containing the fibre material of the spar cap. Resin inlets and vacuum outlets can be connected to the mould cavity. Typically, the mould cavity is evacuated via the vacuum outlets so as to form negative pressure in the mould cavity. In a preferred embodiment, this is done prior to the step of inserting the first and second inserts into the respective gap. This helps consolidating the fibre material and sucking the vacuum foil into the gaps. Once the inserts are inserted, liquid resin can be supplied typically via resin inlets. The resin can thus be forced into the mould cavity due to the pressure differential and impregnates the fibre material of the spar cab. When the fibre material has been fully impregnated, the resin is cured in order to form the final spar cap.

Then, the fibre-reinforced spar cap can be demoulded from the mould. The demoulding step can be carried out particularly efficiently when the guide surface of the first guide member diverges from the guide surface of the second guide member in an upward direction, creating a funnel-shaped upwardly open space, from which the spar cap can be demoulded without substantial damage.

In another aspect, the present invention relates to a mould assembly for manufacturing a fibre-reinforced spar cap for a wind turbine blade, the mould assembly comprising a mould, a first guide member comprising an upstand and a second guide member comprising an upstand, the first and second guide members being fastened to the mould for providing a moulding cavity in between the first and second guide members, a fibre material arranged within the moulding cavity, such that a first gap is provided between the fibre material and the first guide member, and a second gap is provided between the fibre material and second guide member, a vacuum foil placed over the fibre material and the first and second guide members, such that the vacuum foil extends into the first and second gap, a first wedge-shape insert for insertion into the moulding cavity, wherein the first wedge-shape insert is inserted into the first gap on top of the vacuum foil, and a second wedge-shape insert for insertion into the moulding cavity, wherein the second wedge-shape insert is inserted into the second gap on top of the vacuum foil. The mould, the first and second guide members and the first and second wedge-shaped inserts may have the same properties as discussed in the above-recited embodiments and examples.

In particular, each of the guide members may have a substantially L-shaped cross section, or a skewed or compressed L-shaped cross section. In another preferred embodiment, the guide members have a triangular cross section. In other embodiments, the guide members have a prism cross section. It is preferred that each guide member has substantially horizontal section, which can be fastened to the mould, and a substantially vertical section extending from the mould in a substantially vertical or upward direction. In other embodiments, each of the guide members has a triangular cross section. In a preferred embodiment, the first and second guide members extend along the longitudinal direction of the mould, preferably substantially parallel to the lateral edges of the mould. Thus, it is preferred that the first and second guide members extend along substantially the entire length of the mould, and preferably along substantially the entire length of the spar cap. In some embodiments, the insert may have a length of at least <NUM> meters, such as at least <NUM> meters or at least <NUM> meters. In a preferred embodiment, the first and second guide members are bolted to the mould. Thus, one or more bolts can be inserted into each guide member, preferably extending into receiving holes in the mould. In other embodiments, the guide members can be fastened to the mould by one or more screws, adhesives, snap connections, or other fastening means.

In a preferred embodiment, each insert comprises a silicone material. In a preferred embodiment, each insert comprises high density polyethylene (HDPE) and a silicone material. In a preferred embodiment, the insert is substantially wedge-shaped. In a preferred embodiment, the insert has a triangular cross section or a trapezoid cross section. Thus, in some embodiments, the insert may have a length of at least <NUM> meters, such as at least <NUM> meters or at least <NUM> meters, with a triangular or trapezoid cross section. It is preferred that the insert tapers towards one end as seen in its cross section.

In another aspect, the present invention relates to a wind turbine blade comprising a spar cap according to the present invention. In another aspect, the present invention relates to a method of manufacturing a wind turbine 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, the method comprising the steps of manufacturing one or more spar caps according to the method of the present invention, arranging a plurality of blade components in a blade mould, assembling the one or more spar caps in the blade mould relative to the plurality of blade components, the spar cap comprising a plurality of strips of fibre material arranged into adjacent stacks of strips, and infusing resin into the one or more spar caps and the plurality of blade components to form a wind turbine blade shell part.

All features and embodiments discussed above with respect to the method of manufacturing a fibre-reinforced spar cap of the present invention likewise apply to the mould assembly, to the spar cap, and to the method of manufacturing a wind turbine blade of the present invention, and vice versa.

According to another aspect, the present invention relates to a wind turbine blade obtainable by the method according to the present invention.

As used herein, the term "spanwise" is used to describe the orientation of a measurement or element along the blade from its root end to its tip end. In some embodiments, spanwise is the direction along the longitudinal axis and longitudinal extent of the wind turbine blade.

As used herein, the term "longitudinal" generally means a direction running parallel to the maximum linear dimension, typically the longitudinal axis, of, for example the spar cap or the spar cap mould. The longitudinal direction of the spar cap usually coincides with the spanwise direction of the blade, when the spar cap is arranged within the blade.

The invention is explained in detail below with reference to an embodiment shown in the drawings, in which.

<FIG> illustrates a conventional modern upwind wind turbine 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> farthest from the hub <NUM>. The rotor has a radius denoted R.

<FIG> shows a schematic view of a wind turbine blade <NUM>. The wind turbine blade <NUM> has the shape of a conventional wind turbine blade and comprises a root region <NUM> closest to the hub, a profiled or an airfoil region <NUM> farthest away from the hub and a transition region <NUM> between the root region <NUM> and the airfoil region <NUM>.

<FIG> also illustrates the longitudinal extent L, length or longitudinal axis of the blade.

The blade is typically made from a pressure side shell part <NUM> and a suction side shell part <NUM> that are glued to each other along bond lines at the leading edge <NUM> and the trailing edge of the blade <NUM>.

<FIG> shows a schematic view of a cross section of the blade along the line I-I shown in <FIG>. As previously mentioned, the blade <NUM> comprises a pressure side shell part <NUM> and a suction side shell part <NUM>. The pressure side shell part <NUM> comprises a spar cap <NUM>, also called a main laminate, which constitutes a load bearing part of the pressure side shell part <NUM>. The spar cap <NUM> comprises a plurality of fibre layers <NUM> mainly comprising unidirectional fibres aligned along the longitudinal direction of the blade in order to provide stiffness to the blade. The suction side shell part <NUM> also comprises a spar cap <NUM> comprising a plurality of fibre layers <NUM>. The pressure side shell part <NUM> may also comprise a sandwich core material <NUM> typically made of balsawood or foamed polymer and sandwiched between a number of fibre-reinforced skin layers. The sandwich core material <NUM> is used to provide stiffness to the shell in order to ensure that the shell substantially maintains its aerodynamic profile during rotation of the blade. Similarly, the suction side shell part <NUM> may also comprise a sandwich core material <NUM>.

The spar cap <NUM> of the pressure side shell part <NUM> and the spar cap <NUM> of the suction side shell part <NUM> are connected via a first shear web <NUM> and a second shear web <NUM>. The shear webs <NUM>, <NUM> are in the shown embodiment shaped as substantially I-shaped webs. The first shear web <NUM> comprises a shear web body and two web foot flanges. The shear web body comprises a sandwich core material <NUM>, such as balsawood or foamed polymer, covered by a number of skin layers <NUM> made of a number of fibre layers. The blade shells <NUM>, <NUM> may comprise further fibre-reinforcement at the leading edge and the trailing edge. Typically, the shell parts <NUM>, <NUM> are bonded to each other via glue flanges.

<FIG> illustrate various steps of the method of the present invention. As seen in <FIG> and <FIG>, a first guide member <NUM> and a second guide member <NUM>, each having a substantially L-shaped cross section, are fastened to the moulding surface <NUM> of a mould <NUM>. This can be advantageously be done by using bolts <NUM>, as shown in the cross sectional view of <FIG>. The guide members <NUM>, <NUM> comprise respective upstands <NUM>, <NUM> forming respective longitudinally extending guide surface <NUM>, <NUM>. A moulding cavity <NUM> is provided in between the first and second guide members <NUM>, <NUM>. The first guide member <NUM> comprises a longitudinally extending guide surface <NUM>, and the second guide member <NUM> comprises a longitudinally extending guide surface <NUM> facing the guide surface <NUM> of the first guide member <NUM>. As best seen in <FIG>, the guide surface <NUM> of the first guide member diverges from the guide surface <NUM> of the second guide member in an upward direction, the planes in which the respective guide surfaces <NUM>, <NUM> lie forming an angle α.

As illustrated in <FIG> and <FIG>, a fibre material <NUM> is placed within the moulding cavity <NUM>, such that a first gap <NUM> is provided between the fibre material <NUM> and the first guide member <NUM>, and a second gap <NUM> is provided between the fibre material <NUM> and the second guide member <NUM>. As seen in <FIG>, the fibre material comprises a plurality of strips <NUM> of fibre material arranged into adjacent stacks of strips, such as pultruded fibre strips. As best seen in <FIG>, the fibre material <NUM> or the final spar cap <NUM> has first and second longitudinally extending lateral surfaces 41a, 41b, wherein the first guide member <NUM> comprises a longitudinally extending guide surface <NUM> forming an acute angle β1 with the first lateral surface 41a of the spar cap, and wherein the second guide member <NUM> comprises a longitudinally extending guide surface <NUM> forming an acute angle β2 with the second lateral surface 41b of the spar cap.

As illustrated in <FIG>, a vacuum foil <NUM> is placed over the fibre material <NUM>/<NUM> and the first and second guide members <NUM>, <NUM>, such that the vacuum foil <NUM> extends into the first and second gap <NUM>, <NUM>. For better visibility, the vacuum foil is omitted in the perspective view in <FIG>. A first wedge-shaped insert <NUM> is inserted into the first gap <NUM> on top of the vacuum foil, and a second wedge-shaped insert <NUM> is inserted into the second gap <NUM> on top of the vacuum foil. This can be done by squeezing the first insert <NUM> into the first gap, and by squeezing the second insert <NUM> into the second gap. As seen in <FIG>, the first and second guide members <NUM>, <NUM> and the first and second inserts <NUM>, <NUM> extend along substantially the entire length Ls of the spar cap <NUM>.

Then, resin is infused into the fibre material to form a resin-infused fibre material, the resin is cured to form the fibre-reinforced spar cap <NUM>. Subsequently, the first and second inserts <NUM>, <NUM> and the vacuum foil <NUM> can be removed and the fibre-reinforced spar cap <NUM> can be demoulded from the mould <NUM>.

Claim 1:
A method of manufacturing a fibre-reinforced spar cap (<NUM>) for a wind turbine blade, the method comprising the steps of:
providing a mould (<NUM>),
fastening a first guide member (<NUM>) and a second guide member (<NUM>) to the mould for providing a moulding cavity (<NUM>) in between the first and second guide members,
arranging a fibre material (<NUM>) within the moulding cavity, such that a first gap (<NUM>) is provided between the fibre material and the first guide member, and a second gap (<NUM>) is provided between the fibre material and second guide member,
placing a vacuum foil (<NUM>) over the fibre material and the first and second guide members, such that the vacuum foil (<NUM>) extends into the first and second gap (<NUM>, <NUM>),
inserting a first insert (<NUM>) into the first gap (<NUM>) on top of the vacuum foil,
inserting a second insert (<NUM>) into the second gap (<NUM>) on top of the vacuum foil,
infusing resin into the fibre material to form a resin-infused fibre material,
curing the resin-infused fibre material to form the fibre-reinforced spar cap (<NUM>),
removing the first and second inserts (<NUM>, <NUM>) and the vacuum foil (<NUM>), and
demoulding the fibre-reinforced spar cap from the mould.