A method of preparing fibre reinforcing material

Abstract

In a first aspect of the present invention there is provided a method of preparing fibre reinforcing material from a wind turbine blade The method comprises providing a used wind turbine blade, the blade extending longitudinally between a root end and a tip end and comprising a blade shell. The used blade further comprising a longitudinally-extending spar structure configured to support the shell. The spar structure is at least partially formed of a fibre reinforced composite material comprising a plurality of longitudinally-extending reinforcing fibres oriented such that a fibre direction of each reinforcing fibre is substantially parallel to a longitudinal axis of the blade. The method further comprises separating a fibre reinforced composite body from the used wind turbine blade. The fibre reinforced composite body comprises a plurality of longitudinally-extending reinforcing fibres. The method further comprises fragmenting the fibre reinforced composite body into a plurality of fibre elements. Each fibre element comprises at least one longitudinally extending reinforcing fibre, and each fibre element extends longitudinally in a direction substantially parallel to the fibre direction of the respective at least one longitudinally extending reinforcing fibre.

Description

[0001] A METHOD OF PREPARING FIBRE REINFORCING MATERIAL

[0002] Technical field

[0003] The present invention relates generally to wind turbine blades and more particularly to a method of preparing fibre reinforcing material from a wind turbine blade.

[0004] Modern wind turbine blades typically include a substantially hollow outer shell supported by one or more spar structures. The shell and spar structures may be formed, at least partially, of composite materials because of their advantageous strength to weight ratio. For example, a longitudinally-extending spar structure may include one or more longitudinally-extending spar caps configured to take up bending loads experienced by the blade in use. Accordingly, such spar caps may include a plurality of longitudinally- extending reinforcing fibres to provide the requisite stiffness to the spar cap. However, reinforcing fibres, such as carbon fibres for example, may be relatively difficult and expensive to manufacture.

[0005] Blade design practices typically mean that structural components of the wind turbine blade are designed with a safety factor that results in the structural components being capable of withstanding loads far greater than the loads actually experienced by said components in use. Accordingly, the reinforcing fibres of the spar structure may have a projected lifetime that is far greater than the lifetime of the wind turbine blade, for example. This means that when a blade is decommissioned at the end of its life, the reinforcing fibres may still be perfectly functional.

[0006] Further, in some cases a wind turbine blade may be decommissioned as a result of damage which doesn’t affect the spar structure or reinforcing fibres. Accordingly the reinforcing fibres may be perfectly functional despite the blade as a whole being decommissioned. The same may apply to reinforcing fibres in test blades or blade parts disposed of as a result of manufacturing errors or transport damage before being used.

[0007] It follows that there is the possibility of reusing the reinforcing fibres previously included in a wind turbine blade in new applications. It is against this background that the present invention has been developed. \N0 2021 / 191296 discloses a method of preparing a wind turbine blade for recycling by sectioning into wind turbine blade parts and crushing and / or grinding each wind turbine blade part separately.

[0008] Summary

[0009] In a first aspect of the present invention there is provided a method of preparing fibre reinforcing material from a wind turbine blade. The method comprises providing a used wind turbine blade, the blade extending longitudinally between a root end and a tip end and comprising a blade shell. The used blade further comprising a longitudinally-extending spar structure configured to support the shell. The spar structure is at least partially formed of a fibre reinforced composite material comprising a plurality of longitudinally-extending reinforcing fibres oriented such that a fibre direction of each reinforcing fibre is substantially parallel to a longitudinal axis of the blade. The method further comprises separating a fibre reinforced composite body from the used wind turbine blade. The fibre reinforced composite body comprises a plurality of longitudinally-extending reinforcing fibres. The method further comprises fragmenting the fibre reinforced composite body into a plurality of fibre elements. Each fibre element comprises at least one longitudinally extending reinforcing fibre, and each fibre element extends longitudinally in a direction substantially parallel to the fibre direction of the respective at least one longitudinally extending reinforcing fibre.

[0010] In some examples, the used wind turbine blade may be a decommissioned wind turbine blade that has reached the end of its service lifetime. Alternatively, in some other examples the used wind turbine blade may be a decommissioned wind turbine blade that is damaged. Alternatively, the used wind turbine blade may be a blade production waste fraction element. Further still, in some other examples the used wind turbine blade may be a test blade. It will be appreciated that in each of these examples, as described previously by way of background, the reinforcing fibres may be perfectly functional despite the blade as a whole being decommissioned or disposed of.

[0011] The spar structure may comprise one or more spar caps. Accordingly, the fibre reinforced composite body may be at least part of a spar cap, and the longitudinally-extending reinforcing fibres may be reinforcing fibres of the spar cap. Spar caps may comprise a plurality of substantially unidirectional reinforcing fibres in a highly organised arrangement. Accordingly, the fibre reinforced composite body may comprise a plurality of substantially unidirectional reinforcing fibres in a highly organised arrangement. It follows that the method may be particularly advantageous for preparing fibre reinforcing material from a wind turbine blade spar cap.

[0012] In some preferred examples, the longitudinally-extending reinforcing fibres may be carbon fibres, and the spar structure may therefore be at least partially formed of a carbon fibre reinforced composite material. Accordingly, in some examples the spar cap may be at least partially formed of a carbon fibre reinforced composite material, such as carbon fibre reinforced plastic (CFRP). It follows that the fibre reinforced composite body separated from the used wind turbine blade may comprise carbon fibres, and the fibre reinforced composite body may be a carbon fibre reinforced composite body. Accordingly, the examples of methods described herein may be utilised for preparing carbon fibre reinforcing material, in particular longitudinally-extending carbon reinforcing fibres, from a used wind turbine blade, and more particularly from a used wind turbine blade spar cap.

[0013] In some examples, the spar structure may be bonded to an internal surface of the blade shell. Accordingly, separating a fibre reinforced composite body from the used wind turbine blade may comprise separating the fibre reinforced composite body from an internal surface of the blade shell, for example by cutting or chemically separating an adhesive layer bonding the spar structure to the internal surface.

[0014] For example, the spar structure may be bonded to an internal surface of the blade shell by an epoxy-based resin or adhesive. Separating the fibre reinforced composite body from the used wind turbine blade may therefore comprise applying a dissociation fluid to the bond between the spar cap and internal surface of the blade shell to at least partially degrade the epoxy-based resin or adhesive. In such an example, the dissociation fluid may be a swelling fluid. Such a method may be particularly applicable to examples wherein the epoxy-based resin or adhesive is an amine cured epoxy. In some examples, the swelling fluid may comprise formic acid.

[0015] In some other examples, the spar cap may be bonded to the internal surface of the blade shell by a chemically disassembleable resin such as Aditya Birla Recyclamine. In such an example, application of the dissociation fluid to the bond between the spar cap and internal surface of the blade shell may chemically disassemble the resin to thereby facilitate separating a fibre reinforced composite body from the used wind turbine blade.

[0016] Alternatively, in some examples, the spar structure may be integrated in the blade shell such that a portion of the blade shell overlaps at least a portion of the spar structure. In such an example, separating the fibre reinforced composite body from the used wind turbine blade, for example by cutting, may comprise separating at least part of the spar structure and the overlapping portion of the blade shell from the remainder, i.e. a main portion, of the blade shell. Accordingly in some examples the fibre reinforced composite body may comprise at least part of a spar cap and at least part of an overlapping portion of the blade shell.

[0017] Alternatively, in some other examples, the spar structure may be at least partially integrated in the blade shell. In such an example, separating the fibre reinforced composite body from the used wind turbine blade may comprise separating the fibre reinforced composite body from the blade shell. For example, the spar structure may comprise one or more spar caps that are integrated in the blade shell. Separating the fibre reinforced composite body from the used wind turbine blade may therefore comprise separating at least part of a spar cap from the blade shell.

[0018] In some examples, separating the fibre reinforced composite body from the used wind turbine blade may comprise cutting at least part of the spar structure from the blade shell. For example, the method may comprise cutting through laminate layers of the blade shell to release at least a portion of the spar cap to thereby obtain a separate fibre reinforced composite body. Alternatively, separating the fibre reinforced composite body from the used wind turbine blade may comprise a chemical separation process as described previously with reference to examples of spar caps bonded to the blade shell. In such an example, a dissociation fluid may be applied to the blade shell to at least partially degrade, for example swell, an epoxy matrix material in the blade shell and thereby release the spar cap from the blade shell to obtain a separate fibre reinforced composite body.

[0019] In some examples fragmenting the fibre reinforced composite body into a plurality of fibre elements may comprise splitting the fibre reinforced composite body longitudinally in a direction substantially parallel to the fibre direction of the reinforcing fibres in the composite body. For example, splitting the fibre reinforced composite body may comprise driving a blade or splitting wedge through the fibre reinforced composite body to split the fibre reinforced composite body apart into separate fibre elements each comprising at least one longitudinally-extending reinforcing fibre. A splitting method may be advantageous for obtaining fibre elements in which as many of the reinforcing fibres maintain as great a length as possible because the fibre reinforced composite body is split in line with the fibre direction, meaning the reinforcing fibres are not damaged and maintain their full length. In some examples, the fibre reinforced composite body may comprise a plurality of layers of fibre reinforced composite pultrusions attached together in a stack. Splitting the fibre reinforced composite body may therefore comprise splitting a pultrusion of the stack into a plurality of fibre elements. The pultrusion may comprise a plurality of substantially unidirectional, longitudinally-extending reinforcing fibres in a highly organised, or regimented, arrangement. The strength of bond between fibres in the pultrusion, i.e. a matrix strength, may be relatively low compared to the strength of the fibres themselves, and the fibre reinforced composite body may therefore be split relatively easily by longitudinally splitting through a pultrusion.

[0020] Further, such a splitting method may be particularly advantageous in examples wherein the fibre reinforced composite body comprises one or more fibre interlayers between adjacent layers of fibre reinforced composite pultrusions in the stack. For example a fibre interlayer may comprise biaxial fibre material. Accordingly, a region between adjacent pultrusions in the stack may be more resistant to longitudinal splitting than the pultrusions themselves. It follows that splitting one or more pultrusions in a direction substantially parallel to the fibre direction of the reinforcing fibres in the respective pultrusion(s) may therefore be preferable, compared to splitting through the interlayer, in some examples.

[0021] In some examples wherein the fibre reinforced composite body comprises a plurality of layers of fibre reinforced composite pultrusions attached together in a stack, splitting the fibre reinforced composite body may comprise splitting a plurality of pultrusions in the stack such that the fibre reinforced composite body is fragmented into a plurality of fibre elements each comprising a plurality of reinforcing fibres from a plurality of pultrusions. For example, each pultrusion in the stack may have an upper surface and a lower surface, and the pultrusions may be arranged on top of one another in the stack such that upper and lower surfaces of adjacent pultrusions are attached together. The fibre reinforced composite body may be split longitudinally by a blade or splitting wedge oriented orthogonally to the upper and lower surfaces of the pultrusions. The resultant fibre elements may therefore comprise a stack of portions of a plurality of different pultrusions.

[0022] Further, in some examples the stack of pultrusions may comprise an interlayer of adhesive or resin between adjacent pultrusions. Optionally, such a stack may comprise fibre reinforcing material between adjacent pultrusions. Splitting the fibre reinforced composite body may comprise splitting the adjacent pultrusions and the respective interlayer therebetween such that the fibre reinforced composite body is fragmented into a plurality of fibre elements each comprising reinforcing fibres from a plurality of adjacent pultrusions and a portion of the respective interlayer therebetween. Accordingly, the resultant fibre elements may comprise a stack of portions of a plurality of different pultrusions and a portion of the respective interlayer, optionally including fibre reinforcing material, between the adjacent pultrusions.

[0023] In some examples, the fibre reinforced composite body may comprise a plurality of layers of fibre reinforced composite pultrusions attached together in a stack, and splitting the fibre reinforced composite body may comprise splitting at least one pultrusion apart from an adjacent pultrusion in the stack. For example, the fibre reinforced composite body may be split longitudinally by a blade or splitting wedge aligned with an interlayer or an interface between adjacent pultrusions in the stack. Accordingly, in such an example a fibre element may comprise reinforcing fibres from a single pultrusion.

[0024] In some examples, fragmenting the fibre reinforced composite body may comprise cutting the fibre reinforced composite body along a cutting axis that is substantially parallel to the fibre direction of the reinforcing fibres in the composite body. For example, the method may comprise cutting the fibre reinforced composite body with a bandsaw or a circular saw in some examples, such a method may facilitate use of standard, existing tools in a blade manufacturing and / or recycling facility.

[0025] In some examples, each fibre element may comprise at least one reinforcing fibre embedded in a polymer matrix material. Accordingly, each fibre element may be a composite component in some examples. For example, each fibre element may comprise at least a portion of at least one fibre reinforced composite pultrusion in some examples, it follows that each fibre element may include a plurality of substantially unidirectional longitudinally-extending reinforcing fibres.

[0026] In some examples, the method may further comprise attaching a plurality of fibre elements together to form a compound fibre element comprising a plurality of reinforcing fibres. In such an example, the fibre elements may preferably be attached to one another such that the fibre direction of the reinforcing fibre(s) in each fibre element is substantially parallel to the fibre direction of the reinforcing fibre(s) in each other fibre element of the compound fibre element. Accordingly, the compound fibre element may comprise a plurality of substantially unidirectional longitudinally-extending reinforcing fibres. In some examples, the blade shell may comprise a blade shell polymer resin matrix. In such an example, separating the fibre reinforced composite body from the used wind turbine blade may comprise applying a dissociation fluid to the blade shell to at least partially degrade the blade shell polymer resin matrix. Thereby, the fibre reinforced composite body may be released from the used wind turbine blade or the bond between the blade shell and the fibre reinforced composite body may be weakened and thereby facilitate release of the fibre reinforced composite body from the used wind turbine blade.

[0027] In some examples, the fibre reinforced composite body may comprise reinforcing fibres fixed in a polymer resin matrix. In such an example, fragmenting the fibre reinforced composite body may comprise applying a dissociation fluid to the fibre reinforced composite body to at least partially degrade the polymer resin matrix and thereby release one or more reinforcing fibres from the polymer resin matrix. It will be appreciated that in such an example, the fibre reinforced composite body may be fragmented into a plurality of fibre elements where each fibre element is an individual reinforcing fibre.

[0028] In such examples, the dissociation fluid may be a swelling fluid. For example, the fibre reinforced composite body may comprise reinforcing fibres embedded in a thermoset epoxy matrix having a cross-linked network structure, and the swelling fluid may swell the thermoset epoxy matrix in the fibre reinforced composite body. Such a method may be particularly applicable to examples wherein the thermoset epoxy matrix is an amine cured epoxy. In some examples, the swelling fluid may comprise formic acid.

[0029] In some other examples, the fibre reinforced composite body may comprise reinforcing fibres embedded in a chemically disassembleable resin such as Aditya Birla Recyclamine. In such an example, application of the dissociation fluid to the fibre reinforced composite body may chemically disassemble the resin to thereby release the one or more reinforcing fibres.

[0030] In some examples, the fibre reinforced composite body may comprise a plurality of layers of fibre reinforced composite pultrusions attached together in a stack, and fragmenting the fibre reinforced composite body may comprise applying a dissociation fluid to a joint region between adjacent pultrusions to separate the adjacent pultrusions from one another.

[0031] For example, the fibre reinforced composite pultrusions may be attached together by an epoxy-based resin or adhesive between adjacent pultrusions. Applying the dissociation fluid to the joint region may therefore at least partially degrade the epoxy-based resin or adhesive to thereby facilitate separation of the pultrusions. Again in such an example, the dissociation fluid may be a swelling fluid. For example, the fibre reinforced composite pultrusions may be attached together by an epoxy matrix material having a cross-linked network structure, and the swelling fluid may swell the epoxy matrix material to facilitate separating the fibre reinforced composite pultrusions. Such a method may be particularly applicable to examples wherein the epoxy matrix material is an amine cured epoxy. In some examples, the swelling fluid may comprise formic acid.

[0032] In some other examples, the fibre reinforced composite pultrusions may be attached together in the stack by a chemically disassembleable resin such as Aditya Birla Recyclamine. In such an example, application of the dissociation fluid to the joint region between adjacent pultrusions may chemically disassemble the resin to thereby facilitate separating the fibre reinforced composite pultrusions.

[0033] In some examples, the method may further comprise coiling a fibre element after fragmenting the fibre element from the fibre reinforced composite body. Accordingly, the fibre element may be reconfigured into a coil or spool for transporting or storing the fibre element after the fibre element is fragmented from the fibre reinforced composite body. Transporting and / or storing the fibre element as a coil advantageously maintains the structural integrity of the reinforcing fibres in the fibre element whilst reducing the size or footprint of the fibre element for easier handling and more space-efficient storage. It will be appreciated that in some examples, fibre element may be a composite component, such as a portion of one or more fibre reinforced composite pultrusions. Accordingly, the method may comprise coiling such a composite component. Further, it will be appreciated that in some examples, fibre element may be part of a compound fibre element. Accordingly, the method may comprise coiling a compound fibre element comprising a plurality of fibre elements. In some other examples, as described previously, the fibre elements may each be an individual reinforcing fibre. Accordingly, the method in such an example may comprise coiling or spooling one or more individual reinforcing fibres.

[0034] In some examples the fibre elements may be coiled into a coil, or onto a spool, having a diameter of more than 1 m, preferably more than 1.5 m, more preferably more than 2 m. This helps to ensure that the structural integrity of the reinforcing fibre(s) of the respective fibre element is maintained without introducing kinks or other discontinuities such that the reinforcing fibres maintain their longitudinal stiffness. In some examples, the plurality of fibre elements may each be at least 15 m, preferably at least 25 m, and more preferably at least 35 m in length. It follows that the method may advantageously comprise fragmenting the fibre reinforced composite body into fibre elements comprising reinforcing fibres that are at least 15 m, preferably at least 25 m, and more preferably at least 35 m in length. In some examples the plurality of fibre elements may comprise one or more fibre elements having a length of at least 50 m, preferably at least 60 m, more preferably at least 70 m. Accordingly the method may advantageously comprise fragmenting the fibre reinforced composite body into one or more fibre elements comprising reinforcing fibres that are at least at least 50 m, preferably at least 60 m, more preferably at least 70 m in length.

[0035] In some examples, the method may further comprise reactivating a fibre element after fragmenting the fibre element from the fibre reinforced composite body. Reactivating a fibre element may be particularly applicable to examples wherein the fibre element is a composite component comprising at least one reinforcing fibre embedded in a polymer matrix material. For example, reactivating a fibre element may comprise grinding at least a portion the fibre element to increase the surface roughness thereof to improve adhesion of a resin or adhesive to the fibre element in a subsequent manufacturing process involving the fibre element. In some other examples, reactivating the fibre element may additionally or alternatively include subjecting the fibre element to a chemical etching process, or application of a primer or sizing to the fibre element. In some examples, reactivating a fibre element may comprise submitting the fibre element to a dissociation fluid for example to facilitate removal of chemically disassemblable resin e.g. in residual adhesive or blade shell polymer matrix; cleaning or roughening of the polymer resin matrix of the fibre element; or cleaning a surface of reinforcing fibres.

[0036] In some examples, the method may further comprise applying a resin to a fibre element and optionally curing the resin. For example, as previously described, each fibre element may be a composite component comprising at least one reinforcing fibre embedded in a polymer matrix material. During the process of fragmenting the fibre reinforced composite body into a plurality of fibre elements, the polymer resin matrix material of the fibre element may be chipped or splintered. Accordingly, any such damaged polymer resin matrix material may be replaced by applying a resin to a fibre element and curing the resin.

[0037] Alternatively, in some examples each fibre element may be an individual reinforcing fibre, as previously described. Accordingly, applying a resin to the fibre element may comprise coating a reinforcing fibre in resin, such as a thermoset polymer resin. For example, the resin may be applied to the fibre element, i.e. the reinforcing fibre, in a pultrusion process wherein the fibre element is coated in resin and pulled through a die to form a new fibre reinforced composite pultrusion.

[0038] In another aspect of the present invention there is provided a method of making a wind turbine blade. The method comprises preparing fibre reinforcing material according to the method described in any of the examples herein. The method further comprises arranging one or more layers of blade shell materials in a mould, and arranging one or more fibre elements in the mould. The method further comprises supplying resin to the blade shell materials and fibre element(s) in the mould. The method further comprises at least partially curing the resin to thereby integrate the one or more fibre elements with the one or more layers of blade shell materials.

[0039] In some examples, the one or more layers of blade shell materials may comprise plies of fibre reinforcing material such as biaxial glass fibre reinforcing material or chopped strand mats. In some examples, the one or fibre elements may be composite components comprising at least one reinforcing fibre embedded in a cured polymer matrix material. Accordingly, the fibre elements may be pre-manufactured composite components in relation to the method of making the wind turbine blade. In some examples, the fibre elements may be part of a compound fibre element, and the method may comprise arranging a compound fibre element in the mould.

[0040] In some other examples, the one or more fibre elements may be individual reinforcing fibres that are arranged in the mould as part of a pultrusion. For example, in an example where the fibre elements are individual reinforcing fibres, the fibre elements may be remanufactured into new pultrusions, and such pultrusions may then be arranged in the mould to form at least part of a new wind turbine blade.

[0041] Brief description of the drawings

[0042] Examples of the present invention will now be described by way of non-limiting example only, with reference to the accompanying figures, in which:

[0043] Figure 1 is a schematic exploded view of a used wind turbine blade;

[0044] Figure 2 is a schematic perspective view of an example of a spar cap;

[0045] Figure 3 shows a fibre reinforced composite body separated from the blade; Figure 4 shows an example of cutting the fibre reinforced composite body into a plurality of fibre elements;

[0046] Figures 5 to 7 show examples of splitting the fibre reinforced composite body into a plurality of fibre elements;

[0047] Figure 8 shows an example of fragmenting the fibre reinforced composite body by applying a dissociation fluid to a joint region between pultrusions of the fibre reinforced composite body;

[0048] Figure 9 shows a plurality of cross-sectional views of examples of a compound fibre element formed of a plurality of fibre elements attached together;

[0049] Figure 10 shows an example of submerging a fibre reinforced composite body in dissociation fluid to release a plurality of reinforcing fibres; and

[0050] Figure 11 shows a fibre element arranged in a coil for transport and / or storage.

[0051] Detailed description

[0052] Figure 1 shows a schematic exploded view of an example of a used wind turbine blade 10. For example, the blade 10 may be a decommissioned wind turbine blade that has reached the end of its service life. The blade 10 extends longitudinally between a root end 12 and a tip end 14. As shown in Figure 1 , in some examples the blade 10 may comprise a first half shell 16a and a second half shell 16b. The first and second half shells 16a, 16b may be joined together to form a blade shell 18 which defines an aerodynamic contour and is configured to capture energy from wind incident on the blade 10 in use.

[0053] The blade 10 further comprises a longitudinally-extending spar structure 20 configured to support the blade shell 18. For example, the spar structure may include a shear web 22 arranged between longitudinally-extending spar caps 24 configured to take up bending loads experienced by the blade 10 in use. Whilst the example of a wind turbine blade 10 shown in Figure 1 comprises a single spar structure 20, it should be appreciated that in some examples the blade 10 may comprise a plurality of spar structures 20. Similarly, whilst the example shown in Figures 1 comprise a single spar cap 24 associated with each half shell 16a, 16b, in some other examples the blade 10 may comprise a plurality of spar caps 24 associated with each half shell 16a, 16b. In some examples, the spar structure 20 may be at least partially integrated in the blade shell 18. For example, each spar cap 24 may be embedded within a respective half shell 16a, 16b, for example by integrating the spar cap 24 with a plurality of laminate layers during manufacture of the half shell 16a, 16b. In some other examples, the spar caps 24 may be bonded to an interior surface of the respective half shell 16a, 16b.

[0054] With additional reference to Figure 2, which shows overview of an example of a spar cap 24 and a detail view of the same, the spar structure 20 is at least partially formed of a fibre reinforced composite material comprising a plurality of longitudinally-extending reinforcing fibres 26 oriented such that a fibre direction F of each reinforcing fibre 26 is substantially parallel to a longitudinal axis L of the blade 10. The spar cap 24 shown in Figure 2, which may form part of the spar structure 20 in some examples, is formed of a fibre reinforced composite material comprising a reinforcing fibres 26 as described above. As shown in Figure 2, the spar structure 20, in this example the spar cap 24, may comprise a plurality of layers of fibre reinforced composite pultrusions 28 arranged in a stacked configuration.

[0055] As will now be described in more detail with reference to the remaining figures, fibre reinforcing material of the used wind turbine blade 10 may be prepared for a new application in accordance with examples of the method described herein.

[0056] Figure 3 shows a fibre reinforced composite body 30 comprising a plurality of longitudinally-extending reinforcing fibres 26. The method includes separating such a fibre reinforced composite body 30 from the used wind turbine blade 10. For example, as previously described, the spar structure 20 may be at least partially integrated in the blade shell 18. Accordingly, separating the fibre reinforced composite body 30 from the used wind turbine blade 10 may involve separating the fibre reinforced composite body 30 from the blade shell 18. In some examples, such a process may involve cutting at least part of the spar structure 20, such as at least part of the spar cap 24, from the blade shell 18.

[0057] In some preferred examples the fibre reinforced composite body 30 may comprise an entire spar cap 24, and the method may therefore involve separating a spar cap 24 from the used blade 10. Alternatively, the fibre reinforced composite body 30 may comprise a portion of the spar structure 20, such as a portion of the spar cap 24, as shown in Figure 3. It follows that the fibre reinforced composite body 30 may therefore comprise a plurality of layers of fibre reinforced composite pultrusions 28 attached together in a stack 32, in some examples. Preparing fibre reinforcing material in a method according to examples of the present invention includes fragmenting the fibre reinforced composite body 30 into a plurality of fibre elements 34 as will now be described with reference to Figures 4 to 10. It should be understood that the various examples of fragmenting the fibre reinforced composite body 30 described with reference to Figures 4 to 10 each result in fibre elements 34 comprising at least one longitudinally extending reinforcing fibre 26, and each fibre element 34 extends longitudinally in a direction substantially parallel to the fibre direction F of the respective at least one longitudinally extending reinforcing fibre 26.

[0058] As shown in Figure 4, in some examples, fragmenting the fibre reinforced composite body 30 may involve cutting the fibre reinforced composite body 30 along a cutting axis C that is substantially parallel to the fibre direction F of the reinforcing fibres 26 in the fibre reinforced composite body 30. For example, such a cutting process may be performed using a circular saw 36 or band saw in some examples.

[0059] Spar structures typically has a main surface that follows the shape of the blade shell. Blade shell curves between the leading edge and the trailing edge and hence, and even if the spar structure only follows a part of the shell between the leading edge and the trailing edge, the main surface of the spar structure also curves slightly from the edge of the main surface towards the leading edge to the edge towards the trailing edge. Cutting or otherwise splitting the fibre reinforced composite body 30 in a plane parallel to the fibre direction and orthogonal to a main surface of a spar structure or pultruded members of a spar structure was found to be highly advantageous as it allowed for preparation of straight cuts of the spar structure into almost identical fibre elements 34 being slices of layers of spar structure. This allowed for very predictable and uniform properties of fibre elements. An example of the structure of such a fibre element 34 is shown in upper right corner of Figure 9.

[0060] Alternatively, the fibre reinforced composite body 30 may be fragmented into a plurality of fibre elements 34 in a splitting process, as shown in Figures 5 to 7. A splitting process may be particularly beneficial in examples wherein the fibre reinforced composite body 30 comprises a plurality of layers of fibre reinforced composite pultrusions 28 attached together in a stack 32, as shown in Figures 5 to 7. The splitting process preferably involves splitting the fibre reinforced composite body 30 longitudinally in a direction substantially parallel to the fibre direction F of the reinforcing fibres 26 in the composite body 30. For example, a blade or splitting wedge 38 may be driven into and through the stack 32 to fragment the fibre reinforced composite body 30 into a plurality of fibre elements 34. Examples of splitting method will now be described with reference to Figures 5 to 7.

[0061] For example, as shown in Figure 5, the splitting process may comprise splitting at least one pultrusion 28 apart from an adjacent pultrusion 28 in the stack 32. As such, a tip 40 of the blade or splitting wedge 38 may be aligned with an interface between adjacent pultrusions 28 in the stack 32 to thereby split a pultrusion 28 apart from an adjacent, i.e. neighbouring, pultrusion 28.

[0062] However, in some examples, the stack 32 may include an interlayer 42 between adjacent pultrusions 28 in the stack 32. Such an interlayer 42 may include adhesive and / or fibre reinforcing material that may be tough to split between the adjacent pultrusions 28. Accordingly, with reference to Figure 6, in some examples the splitting process may comprise splitting a pultrusion 28 of the stack 32 into a plurality of fibre elements 34. For example, the blade or splitting wedge 38 may therefore be aligned with a pultrusion 28 to split through the pultrusion 28. For example, a matrix strength bonding the reinforcing fibres 26 of the pultrusion 28 together may be significantly lower than the strength of the interlayer 42. Splitting through the pultrusions 28 may therefore be preferable in some examples.

[0063] In some other examples, as shown in the schematic plan view of Figure 7, the splitting process may involve splitting a plurality of pultrusions 28 in the stack 32 at the same time. For example the tip 40 of the blade or splitting wedge 38 may extend across a plurality of the stacked pultrusions 28 such that multiple pultrusions 28 are split in the same splitting operation. In such examples the fibre reinforced composite body 30 may be fragmented into a plurality of fibre elements 34 which each comprise a plurality of reinforcing fibres 26 from a plurality of pultrusions 28.

[0064] Such a splitting process may also be applicable to examples wherein the stack 32 comprises and an interlayer 42 of adhesive or resin, and optionally fibre reinforcing material, between adjacent pultrusions 28. It follows that in such an example the fibre reinforced composite body 30 may be fragmented into a plurality of fibre elements 34 each comprising reinforcing fibres 26 from a plurality of adjacent pultrusions 28 and a portion of the respective interlayer 42 between said adjacent pultrusions 28. Cross-sectional views of examples of fibre elements 34 resulting from such a splitting process are also shown in Figure 7. Reference is now made to the cross-sectional view of Figure 8 which shows another example of a fibre reinforced composite body 30 comprising a stack 32 of fibre reinforced composite pultrusions 28 attached together. The stack 32 may comprise a joint region 44 at which adjacent pultrusions 28 are attached to one another. For example, the pultrusions 28 may be attached via an epoxy-based resin or adhesive in the joint region 44. Fragmenting the fibre reinforced composite body 30 may involve applying a dissociation fluid 46 to the joint region 44 to facilitate separating the adjacent pultrusions 28 from one another.

[0065] It will be appreciated that each of the methods of fragmenting the fibre reinforced composite body 30 described with reference to Figures 5 to 8 may result in a plurality of fibre elements 34 each comprising at least one reinforcing fibre 26 embedded in a polymer matrix material. For example each fibre element 34 may comprise part of a fibre reinforced composite pultrusion 28. Accordingly, the fibre elements 34 in such examples may be composite components.

[0066] Figure 9 shows cross-sectional views of a plurality of examples of compound fibre elements 48 which may be formed by combining fibre elements 34 following fragmentation from a fibre reinforced composite body 30. In examples comprising attaching a plurality of fibre elements 34 together to form a compound fibre element 48, the fibre elements 34 are preferably arranged such that the fibre direction F of the reinforcing fibre(s) 26 in each fibre element 34 is substantially parallel to the fibre direction F of the reinforcing fibre(s) 26 in each other fibre element 34 of the compound fibre element 48. It will be appreciated that the fibre direction F of the reinforcing fibres 26 shown in the cross-sectional views in Figure 9 extends into the plane of the page in Figure 9.

[0067] Referring now to Figure 10, in some examples the fibre reinforced composite body 30 may comprise reinforcing fibres 26 fixed in a polymer resin matrix 50 (the reinforcing fibres 26 extend into the plane of the page in Figure 10). In such an example the reinforcing fibres 26 may be part of a respective pultrusion 28, as described previously, or in some examples the reinforcing fibres 26 may simply be fixed in a polymer resin matrix 50 without necessarily being part of a pultrusion 28. Irrespective of whether the reinforcing fibres 26 are part of a pultrusion 28 or not, the method may comprise fragmenting the fibre reinforced composite body 30 by applying a dissociation fluid 46 to the fibre reinforced composite body 30. For example, as shown in Figure 10, the fibre reinforced composite body 30 may be at least partially submerged in bath or container 52 of dissociation fluid 46. Accordingly, the dissociation fluid 46 may at least partially degrade the polymer resin matrix 50 in such an example to thereby release one or more reinforcing fibres 26 from the polymer resin matrix 50. It will be appreciated that in such an example, each released reinforcing fibre 26 may constitute a fibre element 34.

[0068] With reference to Figure 11 , after fragmenting the fibre reinforced composite body 30 into a plurality of fibre elements 34 as described previously with reference to Figures 4 to 10, the method may comprise coiling a fibre element 34. Storing and transporting a fibre element 34 in a coil 54 may be advantageous for both preserving the structural integrity of the reinforcing fibres 26 and reducing the overall footprint of the fibre element 34 for ease of handling and storage.

[0069] Whilst not shown in the accompanying figures, in some examples the method may additionally include reactivating a fibre element 34, for example by grinding a surface of the fibre element 34, after fragmenting the fibre element 34 from the fibre reinforced composite body 30. Other examples of reactivating a fibre element 34 may involve adding a primer or sizing, and / or treating a surface of the fibre element 34 with a dissociation fluid.

[0070] Such reactivation may be beneficial for improving adhesion of a resin or adhesive to the fibre element 34 in a subsequent manufacturing process. It follows that the method may include applying a resin to a fibre element 34 and optionally curing the resin in some examples, though it should be understood that such a method step is not necessarily dependent on previously reactivating the fibre element 34.

[0071] Examples of steps in a method for preparing fibre reinforcing material from a wind turbine blade 10 have been described with reference to Figures 4 to 11. Whilst not shown in the accompanying figures, in some examples a method of making a new wind turbine blade may include using one or more fibre elements 34 prepared in accordance with an example of the method described previously. For example, to manufacture a new wind turbine blade, one or more fibre elements 34 may be arranged in a mould. Further, one or more layers of blade shell materials may be arranged in the mould and resin may be supplied to the blade shell materials and the fibre elements 34 in the mould. It follows that the resin may then be at least partially cured to thereby integrate the one or more fibre elements 34 with the one or more layers of blade shell materials.

[0072] Many modifications may be made to the examples described above without departing from the scope of the present invention as defined in the accompanying claims. Further, it will be appreciated that features described in relation to each of the examples above may be readily combined with features described with reference to other examples without departing from the scope of the invention as defined by the following claims.

Claims

CLAIMS:

1. A method of preparing fibre reinforcing material from a wind turbine blade, the method comprising: providing a used wind turbine blade (10), the blade extending longitudinally between a root end (12) and a tip end (14), the blade comprising a blade shell (18) and a longitudinally-extending spar structure (20) configured to support the shell (18), the spar structure (20) being at least partially formed of a fibre reinforced composite material comprising a plurality of longitudinally-extending reinforcing fibres (26) oriented such that a fibre direction F of each reinforcing fibre is substantially parallel to a longitudinal axis L of the blade; separating a fibre reinforced composite body (30) from the used wind turbine blade (10), the fibre reinforced composite body (30) comprising a plurality of longitudinally-extending reinforcing fibres (26); fragmenting the fibre reinforced composite body (30) into a plurality of fibre elements (34), each fibre element (34) comprising at least one longitudinally extending reinforcing fibre (26), and each fibre element (34) extending longitudinally in a direction substantially parallel to the fibre direction F of the respective at least one longitudinally extending reinforcing fibre (26).

2. The method of claim 1, wherein the spar structure (20) is at least partially integrated in the blade shell (18), and wherein separating the fibre reinforced composite body (30) from the used wind turbine blade (10) comprises separating the fibre reinforced composite body (30) from the blade shell (18).

3. The method of claim 1 or claim 2, wherein separating the fibre reinforced composite body (30) from the used wind turbine blade (10) comprises cutting at least part of the spar structure (20) from the blade shell (18).

4. The method of any preceding claim, wherein fragmenting the fibre reinforced composite body (30) into a plurality of fibre elements (34) comprises splitting the fibre reinforced composite body (30) longitudinally in a direction substantially parallel to the fibre direction F of the reinforcing fibres (26) in the fibre reinforced composite body (30).

5. The method of claim 4, wherein the fibre reinforced composite body (30) comprises a plurality of layers of fibre reinforced composite pultrusions (28) attachedtogether in a stack (32), and wherein splitting the fibre reinforced composite body (30) comprises splitting a pultrusion of the stack into a plurality of fibre elements (34).

6. The method of claim 4 or claim 5, wherein the fibre reinforced composite body (30) comprises a plurality of layers of fibre reinforced composite pultrusions (28) attached together in a stack (32), and wherein splitting the fibre reinforced composite body (30) comprises splitting a plurality of pultrusions in the stack such that the fibre reinforced composite body (30) is fragmented into a plurality of fibre elements (34) each comprising a plurality of reinforcing fibres (26) from a plurality of pultrusions.

7. The method of claim 6, wherein the stack (32) comprises an interlayer (42) of adhesive or resin and optionally fibre reinforcing material between adjacent pultrusions (28), and wherein splitting the fibre reinforced composite body (30) comprises splitting the adjacent pultrusions and the respective interlayer (42) therebetween such that the fibre reinforced composite body (30) is fragmented into a plurality of fibre elements (34) each comprising reinforcing fibres (26) from a plurality of adjacent pultrusions and a portion of the respective interlayer (42) therebetween.

8. The method of claim 4, wherein the fibre reinforced composite body (30) comprises a plurality of layers of fibre reinforced composite pultrusions (28) attached together in a stack (32), and wherein splitting the fibre reinforced composite body (30) comprises splitting at least one pultrusion apart from an adjacent pultrusion in the stack (32).

9. The method of any of claims 1 to 3, wherein fragmenting the fibre reinforced composite body (30) comprises cutting the fibre reinforced composite body (30) along a cutting axis C that is substantially parallel to the fibre direction F of the reinforcing fibres (26) in the fibre reinforced composite body (30).

10. The method of any preceding claim, wherein each fibre element (34) comprises at least one reinforcing fibre (26) embedded in a polymer matrix material.

11. The method of claim 10, further comprising attaching a plurality of fibre elements (34) together to form a compound fibre element (48) comprising a plurality of reinforcing fibres (26), wherein the fibre elements (34) are attached to one another such that the fibre direction F of the reinforcing fibre(s) (26) in each fibre element (34) is substantiallyparallel to the fibre direction F of the reinforcing fibre(s) (26) in each other fibre element (34) of the compound fibre element (48).

12. The method of any of the claims 1 to 3, wherein the blade shell (18) comprises a blade shell polymer resin matrix, and wherein separating the fibre reinforced composite body (30) from the used wind turbine blade (10) comprises applying a dissociation fluid (46) to the blade shell (18) to at least partially degrade the blade shell polymer resin matrix.

13. The method of any of claims 1 to 3, wherein the fibre reinforced composite body (30) comprises reinforcing fibres (26) fixed in a polymer resin matrix (50), and wherein fragmenting the fibre reinforced composite body (30) comprises applying a dissociation fluid (46) to the fibre reinforced composite body (30) to at least partially degrade the polymer resin matrix and thereby release one or more reinforcing fibres (26) from the polymer resin matrix.

14. The method of any of claims 1 to 3, wherein the fibre reinforced composite body (30) comprises a plurality of layers of fibre reinforced composite pultrusions (28) attached together in a stack (32), and wherein fragmenting the fibre reinforced composite body (30) comprises applying a dissociation fluid (46) to a joint region (44) between adjacent pultrusions to separate the adjacent pultrusions from one another.

15. The method of any preceding claim, further comprising coiling a fibre element (34) after fragmenting the fibre element (34) from the fibre reinforced composite body (30).

16. The method of any preceding claim, further comprising reactivating a fibre element (34) after fragmenting the fibre element (34) from the fibre reinforced composite body (30).

17. The method of any preceding claim, further comprising applying a resin to a fibre element (34) and optionally curing the resin.

18. A method of making a wind turbine blade, the method comprising: preparing fibre reinforcing material according to the method of any preceding claim;arranging one or more layers of blade shell materials in a mould; arranging one or more fibre elements (34) obtained by the method of any preceding claim in the mould; supplying resin to the blade shell materials and fibre element(s) (34) in the mould; and at least partially curing the resin to thereby integrate the one or more fibre elements (34) with the one or more layers of blade shell materials.

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