Composite element with acid cleavable fixing device

Abstract

A composite element (6), such as a wind turbine blade, is disclosed comprising a stack (20) of at least two fiber mats (13) consisting of oriented fibers (18) embedded in a matrix of a cured acid cleavable resin (14). The fibres (18) of each fibre mat (13) are fixed relative to each other by first fixing means (19) made of a first material, and the at least two fibre mats (13) are fixed relative to each other by second fixing means (16) made of a second material. The second material of the second fixture (16) is an acid cleavable material. The composite element (6) is highly recoverable by exposing the composite element (6) to an acid-containing release agent (11). The invention further relates to a method for producing such a composite element (6) and to a method for detaching such a composite element (6).

Description

Technical Field

[0001] This invention relates to a composite element, such as a wind turbine blade, comprising a stack of at least two fiber pads made of oriented fibers embedded in a cured resin matrix. The invention also relates to methods for manufacturing such a composite element and methods for disassembling such a composite element. Background Technology

[0002] At the end of their service life, composite structures (e.g., wind turbine blades) require disposal. This might involve, for example, dumping the composite structure (possibly after it has been cut into smaller parts) in a landfill. To minimize environmental impact, it is desirable to at least partially recycle composite structures. However, due to the composite nature of these structures, it is difficult to separate them into their original components, making proper recycling of the material difficult, or even impossible. For example, composite structures may include fibers arranged in a cured resin matrix (e.g., epoxy-based resin). Once cured, it is impossible to mechanically separate the fibers from the resin.

[0003] An existing method for recycling composite structures (e.g., epoxy composite structures) involves pulverizing or grinding the composite structure, followed by a separation process to mechanically separate the fibers from the resin material. However, fibers and resin materials recycled in this manner are often contaminated—the fibers are contaminated with the resin material, and vice versa. Furthermore, pulverization shortens the fibers, thus reducing their recycling value. Therefore, the recycled fibers and resin materials are unsuitable for recycling high-quality products.

[0004] Furthermore, in some composite structures, the fiber pad and / or the fibers within the fiber pad are secured relative to each other by suitable fastening devices (e.g., in the form of stitching yarn). Therefore, even if the fiber material and the cured resin material are separated, it may not be possible to recover clean and uncontaminated fibers from the recycled composite structure. Summary of the Invention

[0005] The purpose of embodiments of the present invention is to provide a highly recyclable composite element.

[0006] A further object of the present invention is to provide a method for manufacturing highly recyclable composite elements.

[0007] Another object of the present invention is to provide a method for disassembling composite elements, which allows for the recovery of clean and uncontaminated fibers from the composite elements.

[0008] According to a first aspect, the present invention provides a composite element comprising a stack of at least two fiber pads made of oriented fibers embedded in a cured acid-degradable resin matrix, wherein the fibers of each fiber pad are fixed relative to each other by a first fixing device made of a first material, and wherein the at least two fiber pads are fixed relative to each other by a second fixing device made of a second material, wherein the second material of the second fixing device is an acid-degradable material.

[0009] In this context, the term "composite element" should be interpreted as meaning a structure made of composite materials, which are materials that include suitable fibers embedded in a cured resin matrix.

[0010] Therefore, the composite element according to a first aspect of the invention comprises a stack of at least two fiber mats made of oriented fibers embedded in a cured resin matrix. In this context, the term "fiber mat" should be interpreted as meaning a substantially two-dimensional or sheet-like article that consists entirely or primarily of fibers. The fiber mat can be shaped, similar to the shaping of other sheet materials, by bending, twisting, or cutting, prior to curing of the matrix material. Thus, the fibers of the composite structure are provided as such substantially two-dimensional or sheet-like articles, rather than as loose fibers embedded in a cured resin matrix.

[0011] The cured resin matrix is ​​an acid-degradable resin. Therefore, when the composite element is exposed to a suitable acid (e.g., formic acid or acetic acid), the cured acid-degradable resin matrix will degrade in such a way that the matrix disintegrates and the fiber material and resin material separate. This will be described in further detail below.

[0012] As used herein, acid-degradable resin refers to a resin that, when cured, will disintegrate, for example by swelling or dissolution, upon exposure to a release agent comprising at least 25% by weight (wt%) of formic acid and / or acetic acid at a temperature between 20°C and 90°C. Examples of acid-degradable resins are amine-cured epoxy resins, such as Olin Airstone 760, Hexion RIMR 035C infused epoxy resin, and the Aditya Birla Recyclamine system. In other words, epoxy polymers based on amine-cured epoxy resins form a subclass of acid-degradable epoxy polymers.

[0013] The fibers of each fiber pad are secured relative to each other by a first fixing device made of a first material, and the at least two fiber pads are secured relative to each other by a second fixing device made of a second material. Thus, the fibers within a given fiber pad are secured relative to each other by the first fixing device to hold the fibers in place relative to each other and form the structure of the respective fiber pad. Similarly, the fiber pads in a stack are secured relative to each other by the second fixing device to hold the fiber pads in place relative to each other and form the structure of the stack of fiber pads. During the manufacture of the composite element, this helps to maintain the desired structure, shape, and composition of the fiber pad arrangement of the final composite element before, during, and after matrix formation (e.g., by resin infusion and curing).

[0014] The second material of the second fixing device is an acid-degradable material. Therefore, when the composite element is exposed to acid to decompose the cured resin matrix as described above, the material forming the second fixing device will also degrade. Consequently, the fixing device that holds the fiber pads in place relative to each other will dissolve or disintegrate along with the cured resin matrix, thereby releasing the fiber pads from each other. This allows the fiber pads to be easily recovered from the disintegrated matrix.

[0015] Therefore, the composite element is highly recyclable because the fibers of the fiber pad can be easily recycled in a clean and essentially uncontaminated form, making the fibers (potentially in the form of individual fiber pads) readily reusable in high-quality products.

[0016] The first material of the first fixing device can be an acid-degradable material. According to this embodiment, in addition to the second fixing device, the first fixing device will also pyrolyze and disintegrate when the composite element is exposed to acid. Therefore, the fibers within each fiber pad are also released from each other, allowing for easy recycling of the individual loose fibers and reuse as recycled fibers. Fibers recycled in this way are very clean and pure, and essentially undamaged, so they can be reused or recycled for high-quality products. For example, the recycling of glass fibers may involve melting the glass fibers to form new virgin fibers.

[0017] Alternatively, the first material of the first fixing device can be a material that is not acid-degradable. In this case, when the composite element is exposed to acid, the first fixing device will remain substantially intact, so that the individual fibers will remain fixed relative to each other within their respective fiber pads. Therefore, in this case, the fibers can be recycled in the form of fiber pads, rather than as loose fibers. The recycled fiber pads can be sorted by different types (e.g., separating fiber pads with glass fibers from those with carbon fibers) and reused as fiber pads. Alternatively, the recycled (and optionally sorted) fiber pads can then be exposed to another substance that breaks down the material of the first fixing device and allows for the recycling of loose fibers. Even when the composite material includes different types of fibers arranged in different fiber pads, individual portions of the same type of loose fibers can be recycled.

[0018] The second material of the second fixture can be the same as or similar to the material of the cured acid-degradable resin matrix. According to this embodiment, when the composite element is exposed to acid, the second fixture disintegrates simultaneously and in a similar manner to the cured resin matrix. Alternatively, the second material of the second fixture can be different from the material of the cured acid-degradable resin matrix. For example, this may cause the cured acid-degradable resin matrix to disintegrate faster than the second fixture, thereby allowing a controlled, stepwise recovery process and thus optionally facilitating further separation of material portions.

[0019] When the first material of the first fixture is also an acid-degradable material, the first material may be the same as or similar to the material of the cured acid-degradable resin matrix, or it may be made of a different material. The comments made above regarding the second fixture also apply here.

[0020] The cured acid-degradable resin matrix can be an epoxy-based resin, preferably an amine-cured epoxy-based resin. The inventors of this invention have discovered that suitable epoxy-cured resins are acid-degradable. Alternatively, the cured acid-degradable resin matrix can be of other types, not epoxy-based.

[0021] The first and / or second fixing devices can be in the form of stitching yarns. According to this embodiment, the individual fibers and / or individual fiber pads of the fiber pads are fixed relative to each other by stitching the individual fibers / fiber pads together with stitching yarns. This is a suitable and well-known way of fixing the individual fibers and / or fiber pads relative to each other when manufacturing composite elements. Conventionally, the stitching yarns are not acid-degradable and can, for example, comprise threads of glass fibers or acid-insensitive polymer materials. It has been found highly advantageous to replace conventional stitching yarns with acid-degradable stitching yarns because this means that methods currently used to manufacture composite elements can be readily applied to manufacture composite materials according to the invention. Acid-degradable stitching yarns can be extruded or spun, for example, from acid-degradable resins (e.g., amine-curable epoxy resins).

[0022] Alternatively, the first and / or second fixing devices can be other types, such as mechanical clamps or clips, like H-clamps similar to tag gun fasteners, adhesives, etc.

[0023] The oriented fibers of the fiber mat can be glass fiber or carbon fiber. Other types of fibers are also feasible, but glass fiber and carbon fiber are preferred because they allow for relatively easy further processing to reuse or recycle the fibers after separation from the matrix material. Furthermore, such fibers are suitable for composite elements, such as structural composite elements.

[0024] The composite element can be a wind turbine blade or a portion thereof. According to this embodiment, the wind turbine blade or a portion thereof is highly recyclable at the end of its service life, thereby improving the environmental impact of the wind turbine.

[0025] The composite element may include a third fastening device for permanently or temporarily attaching an article to the composite element. The third fastening device may be, for example, a clamp, screw, grip, hook, or hinge. The article may be, for example, a sensor, cable, or data cable. The composite element may include a third fastening device for permanently or temporarily attaching the composite element to the article. The article may be another composite material or mechanical structure. The third fastening device is made of a third material, wherein the third material of the third fastening device is an acid-degradable material.

[0026] According to a second aspect, the present invention provides a method for manufacturing a composite element, the method comprising the following steps: - Provides multiple oriented fibers and groups the oriented fibers into multiple fiber pads. - The oriented fibers of each fiber pad are fixed relative to each other by a first fixing device made of a first material. - Arrange the fiber mats adjacent to each other to form a stack of fiber mats. - The fiber mats in the stack of fiber mats are fixed relative to each other by a second fixing device made of a second material, wherein the second material of the second fixing device is an acid-degradable material. - Infusing acid-degradable resin into the stack of fiber pads, and - Curing the injected resin to form a composite element.

[0027] The composite element manufactured according to the second aspect of the invention can be a composite element according to the first aspect of the invention, and the above comments on the first aspect of the invention also apply here, and vice versa.

[0028] In the method according to a second aspect of the invention, a plurality of oriented fibers (e.g., glass fibers or carbon fibers) are first provided and grouped into a plurality of fiber mats. The fiber mats may include systematically oriented fibers, such as parallel, biaxial, or triaxially oriented fibers, or randomly oriented fibers.

[0029] Next, the oriented fibers of each fiber mat are secured relative to each other by a first fixing device made of a first material. Thus, the oriented loose fibers are secured relative to each other by the first fixing device, thereby forming the structure of the fiber mat, thereby allowing each fiber mat to be processed as a separate unit. This has already been described above with reference to the first aspect of the invention.

[0030] Next, the fiber mats formed as described above are arranged adjacent to each other to form a stack of fiber mats. Then, the fiber mats in the stack of fiber mats are fixed relative to each other by a second fixing device made of a second material that is acid-degradable. Thus, the fiber mats are now held in place relative to each other in the stack of fiber mats.

[0031] The acid-degradable resin is then infused into the stack of fiber pads, and the infused resin is cured to form a composite element. Thus, the first and second fixing devices are integrated into the composite element.

[0032] Therefore, the composite element obtained by the method according to the second aspect of the invention is highly recyclable because when the composite element is exposed to a suitable acid (e.g., formic acid), the cured acid can break down the resin matrix and the second fixing device, causing them to disintegrate. This has already been described above with reference to the first aspect of the invention.

[0033] The first material of the first fixing device can be an acid-degradable material. As described above with reference to the first aspect of the invention, this will cause the first fixing device to disintegrate when the composite element is exposed to a suitable acid, thereby allowing the recovery of loose fibers. Alternatively, the first material of the first fixing device can be of a non-acid-degradable type, in which case the fibers of the fiber pad remain fixed relative to each other when the composite element is exposed to a suitable acid, thereby allowing the fibers to be recovered in the form of a fiber pad.

[0034] The step of securing the oriented fibers of each fiber pad may include sewing the fibers together with stitching yarn, and / or the step of securing the fiber pads in a stack of fiber pads may include sewing the fiber pads together with stitching yarn. This has already been described above with reference to the first aspect of the invention. Using stitching yarn of a disintegrating, acid-degradable material is highly advantageous because it means that current methods for manufacturing composite elements can be used by replacing conventional stitching yarn with stitching yarn of a suitable acid-degradable material.

[0035] The present invention further provides a composite element that can be obtained by the method according to the second aspect of the invention, and as described above. Therefore, such a composite element is highly recyclable.

[0036] According to a third aspect, the present invention provides a method for disassembling a composite element comprising a stack of at least two fiber pads made of oriented fibers embedded in a cured acid-degradable resin matrix, wherein each fiber of each fiber pad is fixed relative to each other by a first fixing device made of a first material, and wherein the at least two fiber pads are fixed relative to each other by a second fixing device made of a second material, wherein the second material of the second fixing device is an acid-degradable material, the method comprising the following steps: - Expose the composite element to an acid-containing release agent to cause the composite element to disintegrate due to the degradation of the cured acid-based resin matrix and the second fixation device, and - Recover oriented fibers from disintegrated composite elements.

[0037] The composite element disassembled by the method according to the third aspect of the invention may be a composite element according to the first aspect of the invention and / or a composite element manufactured by the method according to the second aspect of the invention. Therefore, the above comments regarding the first and / or second aspects of the invention also apply here, and vice versa.

[0038] Specifically, the composite element comprises a stack of at least two fiber pads made of oriented fibers embedded in a cured acid-degradable resin matrix. Each fiber of each fiber pad is fixed relative to each other by a first fixing device made of a first material, and the at least two fiber pads are fixed relative to each other by a second fixing device made of a second material, which is an acid-degradable material.

[0039] In the method according to the third aspect, the composite element is initially exposed to an acid-containing release agent. Since both the cured resin matrix and the second fixing device are made of an acid-degradable material, this leads to the disintegration of the cured acid-degradable resin matrix (e.g., through swelling and cracking or dissolution) and the disintegration of the second fixing device. Consequently, the fibrous material separates from the resin material of the cured acid-degradable resin matrix, and the fibrous pads release from each other, causing the stack of fibrous pads to disintegrate.

[0040] The acid-releasing agent can be or may contain formic acid. Formic acid is readily available and inexpensive. Furthermore, formic acid is considered safe for humans and the environment. Finally, the inventors of this invention have discovered that formic acid is an effective releasing agent for epoxy resins used in certain relevant epoxy composite structures (e.g., specific wind turbine blades). Therefore, formic acid is a suitable, safe, and cost-effective choice for a releasing agent. Alternatively, the releasing agent may contain other suitable types of acids, such as acetic acid.

[0041] Finally, the oriented fibers are recovered from the disintegrated composite elements. As mentioned above, this can be easily accomplished because the disintegrated, cured acid can break down the resin matrix and the second fixation device. Therefore, the fibers are recovered in a simple manner, and the recovered fibers are clean and substantially pollution-free, making them ideal for reuse or recycling. Similarly, the disintegrated matrix resin can be collected as swollen powdered resin or dissolved resin fragments and recovered in a separate process stream.

[0042] The step of recovering oriented fibers from disintegrated composite elements may include recovering a fiber mat composed of oriented fibers. According to this embodiment, the oriented fibers of the fiber mat are held relative to each other by a first fixing device, and the complete fiber mat is recovered. This allows the fiber mat to be reused and processed as a unit.

[0043] Alternatively, the first material of the first fixing device can be an acid-degradable material, and the step of exposing the composite structure to an acid-containing release agent further causes the first fixing device to disintegrate. According to this embodiment, exposure to an acid-containing release agent also causes the first fixing device to disintegrate, thus the fibers of the individual fiber pads are no longer fixed relative to each other.

[0044] Therefore, according to this embodiment, the step of recovering oriented fibers from the disintegrated composite element may include recovering loose fibers, rather than recovering the fiber pad.

[0045] The composite element may include the third fixing device as described above. In this case, the method of disassembling the composite element may include the step of removing the article before or after exposing the composite element having the third fixing device to an acid-containing release agent. Since the third fixing device is acid-degradable, the third fixing device disintegrates together with the composite element, and a separate step of removing the third fixing device from the composite element is not required as part of the disassembly method.

[0046] In all aspects of the invention, it is highly preferred that the first fixing device, the second fixing device, and the cured acid-degradable resin matrix are distinct entities. Distinct entities herein refer to the fact that the first fixing device and the second fixing device each exist independently of the cured acid-degradable resin matrix prior to the provision of the matrix material for the acid-degradable resin used to form the composite element.

[0047] In some cases, the second material may have the same composition as the cured acid-degradable resin matrix. In these cases, the second fixing device should fix the individual fiber pads relative to each other before the acid-degradable resin forming the cured acid-degradable resin matrix is ​​provided. Attached Figure Description

[0048] The invention will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 It is a perspective view of a wind turbine. Figure 2 This is a perspective view of a composite element in the form of a wind turbine blade according to an embodiment of the present invention. Figures 3-5 The steps of a method for disassembling a composite element according to an embodiment of the present invention are shown. Figures 6-8 Various types of fiber pads are shown for use in composite elements according to various embodiments of the present invention, and Figure 9 and Figure 10 Stacks of various types of fiber pads are shown for use in composite elements according to various embodiments of the present invention. Detailed Implementation

[0049] Figure 1 This is a perspective view of a wind turbine 1, which includes a tower 2 and a nacelle 3 mounted on top of the tower 2. A rotor 4 with a hub 5 carries three wind turbine blades 6 rotatably mounted on the nacelle 3. Thus, wind acting on the wind turbine blades 6 causes the rotor 4 to rotate, and mechanical energy is converted into electrical energy by a generator (not shown) in a manner known per se.

[0050] When the wind turbine 1 or one or more components of the wind turbine 1 reach the end of their service life, it will be scrapped. Therefore, it is desirable to recycle the materials of the components to the greatest extent possible. In particular, the material (typically a composite material) of the wind turbine blade 6 can advantageously be fully or partially recycled. Thus, at least the wind turbine blade 6 can advantageously be manufactured and / or disassembled according to the methods of embodiments of the invention.

[0051] Figure 2 This is a perspective view of a composite element according to an embodiment of the present invention, in the form of a wind turbine blade 6. The wind turbine blade 6 extends longitudinally between a root end 7 and a tip end 8. A reinforcing web 9 extends longitudinally inside the wind turbine blade 6.

[0052] The wind turbine blade 6 comprises a stack of at least two fiber mats (fiber felts) made of oriented fibers (e.g., glass fibers or carbon fibers) embedded in a cured, acid-degradable resin matrix. The wind turbine blade 6 may include other components such as spars, metal mesh, sensors, connectors, etc. The fibers of each fiber mat are secured relative to each other by a first securing device made of a first material, and the at least two fiber mats are secured relative to each other by a second securing device made of a second material. The second material of at least the second securing device is an acid-degradable material. Therefore, when the wind turbine blade 6 is exposed to an acid-containing release agent, the cured, acid-degradable resin matrix and the second securing devices holding the fiber mats together will disintegrate. This makes the fibers easily recyclable, possibly in the form of fiber mats. Therefore, the wind turbine blade 6 is highly recyclable.

[0053] The first material of the first fixing device that holds the oriented fibers within their respective fiber pads can further be an acid-degradable material. In this case, when the wind turbine blade 6 is exposed to an acid-containing release agent, the first fixing device also disintegrates, and the loose fibers can then be easily recovered.

[0054] Figures 3-5 The method steps for disassembling a composite element 6 (e.g., in the form of a wind turbine blade or a portion thereof) according to an embodiment of the present invention are shown. Figure 3 In this process, the composite element 6 has been immersed in an acid-containing release agent 11 contained in container 12. The composite structure 6 includes a plurality of fiber pads 13 (five of which are shown in the figure), which are embedded in a cured acid-degradable resin matrix 14 and form a stack of fiber pads 13. The fiber pads 13 include oriented fibers, such as glass fibers or carbon fibers. In addition, the composite element 6 includes two spar caps 15 and a reinforcing web 9.

[0055] The oriented fibers of the fiber pads 13 are secured relative to each other by a first fastening device (not shown) made of a first material (e.g., in the form of sewing yarn or adhesive). Furthermore, each fiber pad 13 is secured relative to each other by a second fastening device 16 made of a second material (e.g., in the form of sewing yarn). The second material is an acid-degradable material.

[0056] The release agent 11 contains an acid, preferably formic acid, and acts on the composite element 6 in a manner that causes the composite element 6 to disintegrate. More specifically, the release agent 11 acts on the cured acid-degradable resin matrix 14 and the acid-degradable second fixation device 16 to cause their disintegration.

[0057] For example, the release agent 11 may cause the epoxy polymer of the resin 14 and the second fixing device 16 to swell, and this may cause the cured acid-degradable resin matrix 14 and the second fixing device 16 to disintegrate into swollen epoxy particles. This, in turn, releases the fiber pad 13, as well as the spar cap 15 and the reinforcing web 9, from the cured acid-degradable resin matrix 14, and releases the fiber pad 13 from each other. In other cases, the release agent may dissolve the resin 14.

[0058] exist Figure 4 In this process, the release agent 11 has acted on the composite element 6 for a sufficiently long time to cause the above-mentioned reference. Figure 3 The disintegration of the composite element 6 is described. In particular, it can be seen that the fiber pad 13 now floats freely in the mixture 17 of the release agent and the disintegrating resin. Therefore, the fiber pad 13 can be easily recovered from the mixture 17 of the release agent and the disintegrating resin in whole form, separated from each other, and retaining its original fiber orientation.

[0059] exist Figure 5 In this process, the reinforcing web has been recovered from the container containing the release agent 11. The spar cap 15 has moved upward toward the surface of the release agent 11 and the top of the container 12, while the mixture 17 of the release agent and disintegrating resin, as well as the released fiber pad 13, has moved downward toward the bottom of the container 12.

[0060] Figure 6 A fiber pad 13 is shown in a composite element according to an embodiment of the invention. The fiber pad 13 comprises a plurality of unidirectionally arranged (i.e., oriented) fiber bundles 18. The fiber bundles 18 are secured relative to each other by a first fastening device 19 in the form of stitching yarn. This ensures that the fiber bundles 18 are held in place relative to each other, so that the fiber pad 13 can be handled as a single unit.

[0061] The first fixing device 19 can be made of an acid-degradable material. In this case, during the disassembly of the composite element containing the fiber pad 13, the first fixing device 19 will disintegrate if exposed to a suitable acid-releasing agent, thereby allowing the fiber bundle 18 to be recovered in a substantially clean, uncontaminated, and undamaged state as part of the recycling process.

[0062] Figure 7 An alternative fiber pad 13 is shown in a composite element used in an embodiment of the invention. Figure 7 Fiber pad 13 and Figure 6 The fiber pad 13 is very similar, so it will not be described in detail here. Specifically, Figure 7 The fiber pad 13 includes a plurality of unidirectionally arranged fiber bundles 18, and the fiber bundles 18 are fixed relative to each other by a first fixing device 19. However, in Figure 7 In the fiber pad 13, the first fixing device 19 is in the form of an adhesive that holds the fiber bundles 18 together. Also in this case, the first fixing device 19 can be made of an acid-degradable material so that it disintegrates upon exposure to a suitable acid-releasing agent, thereby allowing the fiber bundles 18 to be recycled as part of a recycling process.

[0063] Figure 8 Another alternative fiber pad 13 is shown for use in a composite element according to an embodiment of the invention. (Compared to...) Figure 6 and Figure 7 Similar to fiber pad 13, Figure 8 The fiber pad 13 comprises multiple fiber bundles 18. However, in Figure 8 In the fiber pad 13, fiber bundles 18 are arranged in a triaxial pattern, i.e., in an oriented manner. The fiber bundles 18 are secured relative to each other by a first fixing device 19 along a zigzag path of the triaxial pattern of the fiber bundles 18. The first fixing device 19 may be, for example, as described above. Figure 6 The described form of the sewing yarn, or the above reference. Figure 7 The adhesive described is in the form of... In any case, in the same case, the first fixing device 19 can be made of an acid-degradable material.

[0064] It should be noted that, Figures 6-8 In each of the fiber pads 13 shown, a single fiber 18 may be used instead of the fiber bundle 18 shown.

[0065] Figure 9 A stack 20 of fiber pads 13 in a composite element according to an embodiment of the present invention is shown, with six fiber pads 13 shown in the figure. The fiber pads 13 are arranged adjacent to each other to form the stack 20. The fiber pads 13 may be, for example... Figures 6-8 Any of the fiber pads 13 shown in the diagram.

[0066] The fiber pads 13 are secured relative to each other by a second fastening device 16 in the form of stitching yarn. Thus, the fiber pads 13 are held in place relative to each other, thereby ensuring that the stack of fiber pads 13 20 can be handled as a single unit.

[0067] The second fixture 16 is made of an acid-degradable material. This ensures that during the disassembly of the composite element containing the fiber pad 13 stack 20, if the second fixture 16 is exposed to a suitable acid-releasing agent, it will disintegrate, thus allowing the fiber pad 13 to be recycled in a substantially clean, uncontaminated, and undamaged state as part of the recycling process.

[0068] Figure 10 An alternative stack 20 for use in a composite element according to an embodiment of the invention is shown, with six fiber pads 13 shown in the figure. The fiber pads 13 can be, for example... Figures 6-8 Any of the fiber pads 13 shown in the diagram.

[0069] Similar to Figure 9 The stacked body 20 of fiber pad 13, in Figure 10 In this arrangement, the fiber pads 13 are arranged adjacent to each other to form a stack 20 and are secured relative to each other by a second fixing device 16. However, in this case, the second fixing device 16 is in the form of multiple clamps, each clamp connecting two or more fiber pads 13 to each other.

[0070] In the same case, the second fixture 16 is made of an acid-degradable material so that it disintegrates upon exposure to a suitable acid-releasing agent, thereby allowing the fiber mat 13 to be recycled as part of the recycling process.

Claims

1. A composite element (6) comprising a stack (20) of at least two fiber pads (13) made of oriented fibers (18) embedded in a cured acid-degradable resin (14) matrix, wherein, The fibers (18) of each fiber pad (13) are fixed relative to each other by a first fixing device (19) made of a first material, and wherein the at least two fiber pads (13) are fixed relative to each other by a second fixing device (16) made of a second material, wherein the second material of the second fixing device (16) is an acid-degradable material.

2. The composite element (6) according to claim 1, wherein, The first fixing device (19), the second fixing device (16), and the cured acid-degradable resin (14) matrix are different entities.

3. The composite element (6) according to claim 1 or 2, wherein, The first material of the first fixed device (19) is an acid-degradable material.

4. The composite element (6) according to any one of the preceding claims, wherein, The second material of the second fixing device (16) is the same as or similar to the material of the cured acid-degradable resin (14) matrix.

5. The composite element (6) according to any one of the preceding claims, wherein, The cured acid-degradable resin (14) matrix is ​​an epoxy resin, preferably an amine-cured epoxy resin.

6. The composite element (6) according to any one of the preceding claims, wherein, The first fixing device (19) and / or the second fixing device (16) are in the form of sewing yarn.

7. The composite element (6) according to any one of the preceding claims, wherein, The fibers (18) of the fiber mat (13) are glass fibers or carbon fibers.

8. The composite element (6) according to any one of the preceding claims, wherein, The composite element (6) is a wind turbine blade or a part of a wind turbine blade.

9. The composite element (6) according to any one of the preceding claims further includes a third fixing device for at least temporarily attaching the article to the composite element (6) or at least temporarily attaching the composite element (6) to the article, wherein, The third fixture is made of a third material, wherein the third material of the third fixture is an acid-degradable material.

10. A method for manufacturing a composite element (6), the method comprising the following steps: - Provide multiple oriented fibers (18) and group the oriented fibers (18) into multiple fiber pads (13). - The oriented fibers (18) of each fiber pad (13) are fixed relative to each other by a first fixing device (19) made of a first material. - Arrange the fiber mats (13) adjacent to each other to form a stack (20) of fiber mats (13). - The fiber pads (13) in the stack (20) of fiber pads (13) are fixed relative to each other by a second fixing device (16) made of a second material, wherein the second material of the second fixing device (16) is an acid-degradable material. - Acid-degradable resin (14) is infused into the stack (20) of fiber pads (13), and - The injected resin (14) is cured to form a composite element (6).

11. The method according to claim 10, wherein, The first fixing device (19), the second fixing device (16), and the cured acid-degradable resin (14) matrix are different entities.

12. The method according to claim 10 or 11, wherein, The first material of the first fixed device (19) is an acid-degradable material.

13. The method according to any one of claims 10-12, wherein, The step of securing the oriented fibers (18) of each fiber pad (13) involves sewing the fibers (18) together with stitching yarn.

14. The method according to any one of claims 10-13, wherein, The step of fixing each fiber pad (13) in the stack (20) of fiber pads (13) includes sewing each fiber pad (13) together by sewing yarn.

15. A composite element (6) that can be obtained by the method according to any one of claims 10-14.

16. A method for disassembling a composite element (6), the composite element (6) comprising a stack (20) of at least two fiber pads (13) composed of oriented fibers (18) embedded in a cured acid-degradable resin (14) matrix, wherein, The fibers (18) of each fiber pad (13) are fixed relative to each other by a first fixing device (19) made of a first material, and wherein the at least two fiber pads (13) are fixed relative to each other by a second fixing device (16) made of a second material, wherein the second material of the second fixing device (16) is an acid-degradable material, the method comprising the following steps: - Expose the composite element (6) to an acid-containing release agent (11) to cause the composite element (6) to disintegrate due to the disintegration of the cured acid-degradable resin (14) matrix and the second fixing device (16), and - Recover oriented fibers (18) from the disintegrated composite element (6).

17. The method according to claim 16, wherein, The first fixing device (19), the second fixing device (16), and the cured acid-degradable resin (14) matrix are different entities. The step of recovering oriented fibers (18) from the disintegrated composite element (6) includes recovering the fiber mat (13) composed of oriented fibers (18).

18. The method according to claim 16 or 17, wherein, The first material of the first fixture (19) is an acid-degradable material, and the step of exposing the composite structure (6) to an acid-containing release agent (11) further causes the first fixture (19) to disintegrate.

19. The method according to claim 18, wherein, The step of recovering oriented fibers (18) from the disintegrated composite element (6) includes recovering loose fibers (18).

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