Fabric of yarns having at least one epoxy-compatible group and / or epoxy-reactive group and method of manufacture

Abstract

The fabric (20) comprises: i) a first fibrous layer (21, 22, 23, 24) and a second fibrous layer (21, 22, 23, 24), wherein the first fibrous layer (21, 22, 23, 24) and the second fibrous layer (21, 22, 23, 24) are superimposed on one another; and ii) a yarn (25) wherein the yarn (25) extends through the first fibrous layer (21, 22, 23, 24) and the second fibrous layer (21, 22, 23, 24), thereby securing the first fibrous layer (21, 22, 23, 24) to the second fibrous layer (21, 22, 23, 24). The yarn (25) is made of a synthetic material or comprises a synthetic material, in particular a thermoplastic material, having at least one epoxy-compatible group and / or epoxy-reactive group.

Description

Field of the Invention

[0001] The present invention relates to a fabric having a first layer, a second layer and yarns, and a composite element including the fabric. In addition, the present invention relates to a wind turbine including at least one composite element having the fabric. In addition, the present invention relates to a method for manufacturing a fabric.

[0002] Thus, the present invention may relate to the technical field of manufacturing composite elements including fabrics, particularly composite elements for wind turbines. Background Art

[0003] Composite elements, particularly wind turbine blades, are reinforced with glass and carbon non-crimp fabrics (or NCF). Such fabrics are made by stacking different fiber layers on top of each other and then fixing them by means of yarns extending through the layers.

[0004] In the prior art, the yarns used to fix the fiber layers are mainly made of polyester. The disadvantage of such yarns is that they are made of a thermoplastic material that is incompatible with the thermosetting resin used to produce the composite element. This incompatibility can lead to material failures such as microcracks, which can in turn accelerate the fatigue of the composite element. This can occur particularly when the composite element is subjected to cyclic stresses, such as the composite element of a wind turbine blade.

[0005] Figure 5 This material failure effect of a conventional composite element is shown. At the start of cyclic loading, microcracks 51 appear around the sewing yarn filaments 52 at the interface between the non-crimp fabric and the thermosetting material 53. Through continuous cyclic loading, the number and size of the microcracks 51 increase continuously, leading to fatigue failure of the material (as the number of cycles increases, the residual strength continuously decreases). Summary of the Invention

[0006] It may be desirable to manufacture composite elements, particularly composite elements for wind turbines, in an efficient and robust manner.

[0007] A fabric, a composite element, a wind turbine and a manufacturing method are described.

[0008] According to a first aspect of the present invention, a fabric is described that includes a first fiber layer and a second fiber layer, wherein the first fiber layer and the second fiber layer are stacked on top of each other.

[0009] According to a first aspect, the fabric further comprises a yarn which extends through the first fibrous layer and the second fibrous layer so as to fix the first fibrous layer to the second fibrous layer. The yarn is made of or comprises a synthetic material, in particular a plastic material such as a thermoplastic material, which synthetic material has at least one epoxy compatibility group and / or a group reactive to epoxy.

[0010] According to a second aspect of the invention, there is described a composite element, in particular a wind turbine blade, which comprises at least one fabric, in particular a fabric according to the first aspect of the invention.

[0011] According to a third aspect of the invention, there is described a wind turbine having at least one composite element, in particular a composite element according to the second aspect of the invention.

[0012] According to a fourth aspect of the invention, there is provided a method of manufacturing a fabric. The method comprises the steps of: i) placing a first fibrous layer on top of a second fibrous layer, ii) providing a yarn, and iii) stitching the yarn through the first fibrous layer and the second fibrous layer so as to fix the first fibrous layer and the second fibrous layer with at least one yarn, iv) wherein the yarn is made of or comprises a synthetic material, in particular a thermoplastic material, having at least one epoxy compatibility group and / or a group reactive to epoxy.

[0013] According to a fifth aspect of the invention, there is described the use (method of use) of a turbine blade made of a material comprising at least one epoxy compatibility group and / or a group reactive to epoxy as a starting material for manufacturing a yarn comprising at least one epoxy compatibility group and / or a group reactive to epoxy.

[0014] According to a sixth aspect of the invention, there is described the use (method of use) of a yarn which comprises or consists of a (thermoplastic) material having at least one epoxy compatibility group and / or a group reactive to epoxy for fixing fibrous layers which respectively comprise or consist of a further (thermoplastic) material having at least one further epoxy compatibility group and / or a group reactive to epoxy.

[0015] According to a further aspect of the invention, there is described a yarn for fixing fibrous layers of a fabric, wherein the yarn comprises or consists of a synthetic material comprising at least one epoxy compatibility group and / or a group reactive to epoxy, in particular wherein the yarn is (at least partially) made of recycled wind turbine blade material.

[0016] In the context of the present application, an "epoxy-compatible group" is a chemical group that does not react with epoxy resin but can be assimilated by the epoxy resin matrix.

[0017] On the other hand, a "group reactive to epoxy" is a group that can undergo a chemical reaction with epoxy resin to form a chemical bond.

[0018] In the context of the present application, the term "fabric" may refer to a fabric including different fiber layers of different or the same materials stacked on one another.

[0019] The fabric can be, for example, a non-crimp fabric. In a non-crimp fabric, the fibers of different layers are not intertwined with each other but are stacked on one another and then stitched together with sewing yarns.

[0020] Non-crimp fabrics are known in the art to be suitable for absorbing cyclic loads and do not exhibit fluctuations due to the arrangement of different layers of the non-crimp fabric.

[0021] Other types of fabrics, such as meshes, veils, fiber stacks, and semi-finished textiles, are also fabrics according to the present invention.

[0022] The fabric can be unidirectional when all fiber layers are arranged in such a way that the fibers of different layers are parallel to each other in one direction.

[0023] The fabric can also be multi-directional, which means that different layers and their respective fibers are arranged along different main extension directions.

[0024] For example, the fabric can also be bi-directional, which means that the fiber layers are arranged in such a way that the fibers of different fiber layers have two main extension directions, where preferably, the condition is that the two directions are orthogonal to each other.

[0025] According to another example, a triaxial fabric having three main extension directions can be provided, preferably having relative angles of -45°, 0°, and 45° with each other.

[0026] According to yet another example, a four-axis fabric can be provided, and the relative angles between the main extension directions are preferably -90°, -45°, 0°, 45°, and 90°.

[0027] In the context of the present disclosure, the term "yarn" may particularly refer to a thread used to fix different fiber layers to each other, which can be a monofilament or a multifilament. Preferably, the yarn is made of a thermoplastic material or includes a thermoplastic material so that the procedures known in the prior art can be used with the yarn. Preferably, the yarn includes a synthetic material, such as a (thermoplastic) plastic material. In one example, the main extension direction of the yarn in the fabric is (substantially) perpendicular to the (one or more) main extension directions of the fibers of the fiber layer.

[0028] According to an exemplary embodiment, the present invention can be based on the idea that when using a yarn having at least one epoxy-compatible group and / or a group reactive to epoxy to fix together the fiber layers of a fabric, the fabric can be provided in an efficient and strong manner.

[0029] Such a fabric can significantly improve the compatibility between the yarn, the fiber layer, and the mold material (such as a thermosetting material, especially an epoxy resin) used for manufacturing composite elements, particularly wind turbine blades.

[0030] Surprisingly, the inventors have found that excellent compatibility can be achieved when the yarn contains at least one epoxy group.

[0031] By including at least one epoxy-compatible group and / or a group reactive to epoxy in the yarn, the mold material (usually a resin that itself contains epoxy groups and / or other groups having high compatibility with epoxy-compatible groups and / or groups reactive to epoxy) can improve the adhesion to the fabric during the curing process of the mold resin. Thereby, the quality of the finished product and the manufacturing method can be improved, and the production efficiency can be increased.

[0032] In particular, the use of epoxy-compatible groups and / or groups reactive to epoxy helps to overcome the incompatibility existing between the yarn (preferably a thermoplastic material) and the resin (usually a thermosetting material). Generally, material differences and incompatibilities can lead to material failures, such as microcracks in the finished product, which may shorten the service life of the composite element itself.

[0033] Nevertheless, by using epoxy-compatible groups and / or groups reactive to epoxy in the yarn, a firm bond can be formed between the fabric and the mold resin forming the composite element, and the number of microcracks at the boundary between the fabric and the resin can be minimized.

[0034] Without being bound by a particular theory, it is currently assumed that during the resin curing process, the epoxy-compatible groups and / or groups reactive to epoxy promote interactions at least in part of the yarn, thereby causing the yarn to dissolve and / or react with the resin matrix.

[0035] Therefore, by the present invention, due to the presence of epoxy-compatible and / or epoxy-reactive groups, a fabric showing a higher affinity for the resin forming the composite element can be used, especially for wind turbines.

[0036] When compared with composite elements known in the prior art, the resulting composite can exhibit improved mechanical properties and a longer service life.

[0037] In a preferred embodiment, wind turbine blades or parts thereof are recycled to provide starting materials for the production of yarns. Specifically, when the resin material of the wind turbine blade contains epoxy-compatible groups and / or groups reactive to epoxy, the yarns of the present invention can be produced in a cost-saving and environmentally friendly manner directly.

[0038] Exemplary embodiments According to one embodiment of the present invention, the thermoplastic material is made from recycled ketal or acetal-based resin.

[0039] According to one embodiment of the present invention, the yarn is a monofilament yarn. A monofilament yarn is a yarn having only one material thread, thus simplifying the manufacturing process.

[0040] The monofilament yarn may have a thickness preferably from 10 µm to 400 µm.

[0041] Alternatively, the yarn may be a multifilament yarn. A multifilament yarn comprises at least two, preferably three or more threads braided or wound together to form a yarn. The multifilament yarn is superior to the monofilament yarn because it has better properties such as high elongation, plasticity, permeability, etc.

[0042] Each thread of the multifilament yarn preferably has a thickness of 1 µm to 400 µm, more preferably 10 µm to 40 µm. Thus, the multifilament yarn is thinner than the monofilament yarn, and therefore makes the multifilament yarn more suitable for fabric manufacturing.

[0043] According to one embodiment of the present invention, the first fiber layer and / or the second fiber layer comprises or is made of at least one of glass fiber, carbon, basalt fiber, natural fiber or synthetic fiber.

[0044] Such fibers are commonly used in the production process of composite elements, thus allowing the use of well-known fibers and materials in the production of composite elements according to the present invention.

[0045] As already explained above, the fabric can be multi-axial, particularly bi-axial, tri-axial or quad-axial.

[0046] Specifically, the fabric is bi-axial, and the fiber layers are placed at an angle to each other, particularly where the angle is between 0° and 90°.

[0047] In addition, the fabric can be tri-axial, and the fiber layers are placed at an angle to each other, particularly the angle is between -45° and 45°.

[0048] In addition, the fabric can be quad-axial, and the fiber layers are placed at an angle to each other, particularly the angle is between -90° and 90°.

[0049] According to an embodiment of the present invention, a yarn is stitched through a first fiber layer and a second fiber layer, wherein the stitch is at least one of a warp stitch, a Trickot stitch, and a Trickot-warp stitch.

[0050] A warp stitch is defined as a stitch that forms a straight line or path when fixing different fiber layers together.

[0051] A Trickot stitch is defined as a stitch that forms a zig-zag path when fixing different fiber layers together. In other words, a Trickot stitch includes a first step in a first direction and a second step in a second direction different from the first direction (especially orthogonal to the first direction).

[0052] A Trickot-warp stitch is defined as a stitch having the following: a first straight step, a first diagonal step along a first diagonal direction, a second straight step along the same direction as the first straight step, and a second diagonal step along a direction between the directions of the first and second straight steps and the first diagonal direction. The second diagonal direction is preferably orthogonal to the first diagonal direction.

[0053] Trickot stitches, especially Trickot-warp stitches, are beneficial for imparting more stiffness and stability to the fabric.

[0054] According to another embodiment, the synthetic material (especially a thermoplastic material) of the yarn is made of or includes a recycled material having at least one epoxy compatibility group and / or a group reactive to epoxy, especially wherein the yarn (at least partially) is made of recycled wind turbine blade material.

[0055] In this way, used or waste materials in composite elements (especially wind turbine blades) can be recycled, thus providing an environmentally friendly and material-saving method for manufacturing yarns.

[0056] According to an embodiment, therefore, used wind turbine blades and their materials can be used to manufacture a yarn, which is preferably made of a thermosetting material, especially a resin, which already has an epoxy compatibility group and / or a group reactive to epoxy.

[0057] Therefore, according to an embodiment, providing the yarn further includes a recycled material, especially a material from turbine blades, which includes at least one epoxy compatibility group and / or a group reactive to epoxy, for manufacturing the yarn.

[0058] According to another embodiment, a method for manufacturing a yarn using materials from recycled composite elements (especially wind turbine blades) is described.

[0059] According to another embodiment, the composite element further comprises: a thermosetting material, in particular a resin (thermosetting resin) that at least partially encapsulates (in particular fully encapsulates) the fabric. Preferably, the resin comprises at least one epoxy-compatible group and / or a group that is reactive towards epoxy, and / or (comprising at least one epoxy-compatible group and / or a group that is reactive towards epoxy) is compatible with at least one epoxy-compatible group and / or a group that is reactive towards epoxy.

[0060] According to another embodiment, a method of manufacturing a composite element is described, the method comprising: at least partially encapsulating the fabric (as described above) in a mold material (in particular a thermosetting material / resin). This can bring the following advantages: a high compatibility can be achieved between the epoxy-compatible group and / or the group that is reactive towards epoxy of the yarn (fabric) and the mold material.

[0061] The above and other aspects of the present invention will be apparent from the examples of the embodiments described below and will be illustrated with reference to the examples of the embodiments. The present invention will be described in more detail below with reference to the examples of the embodiments, but the present invention is not limited thereto. Brief Description of the Drawings Figure 1 A wind turbine according to an exemplary embodiment of the present invention is schematically shown.

[0063] Figure 2 A fabric according to an exemplary embodiment of the present invention is shown.

[0064] Figures 3a, 3b, and 3c show simplified representations of a warp stitch, a Trickot stitch, and a Trickot-warp stitch according to an exemplary embodiment of the present invention.

[0065] Figure 4 A simplified diagram of manufacturing a fabric according to an exemplary embodiment of the present invention is shown.

[0066] Figure 5 A diagram showing the effect of using a yarn according to the prior art in the fabric of a composite element is shown.

[0067] Detailed description of the drawings What is shown in the figures is only schematic. It should be noted that in different figures, similar or identical elements or features are provided with the same reference numerals, or with reference numerals that differ only in the leading digit from the corresponding reference numerals. In order to avoid unnecessary repetition, elements or features that have been elucidated with respect to previously described embodiments will not be repeated in the subsequent parts of the specification.

[0068] In addition, spatial relative terms such as "front" and "rear", "upper" and "lower", "left" and "right", etc. are used to describe the relationship between the elements shown in the figure and another element. Therefore, these spatial relative terms can be applied to usage directions different from the directions shown in the figure. Obviously, all these spatial relative terms only refer to the directions shown in the figure for the sake of description and are not necessarily restrictive, because the device according to the embodiments of the present invention can adopt directions different from those shown in the figure when in use.

[0069] Figure 1 The wind turbine 1 is shown. The wind turbine 1 includes a tower 2 which is mounted on a base (not shown in the figure). A nacelle 3 is mounted on the top of the tower 2. The wind turbine 1 further includes a rotor 4 which has two, three or more blades 5 (in Figure 1 the perspective shown, only two blades 5 are visible). The rotor 4 is rotatable about a longitudinal rotation axis Y which coincides with the axial direction (also referred to as Y). Unless otherwise specified, the terms "axial", "radial" and "circumferential" hereinafter are all based on the longitudinal axis Y. The blades 5 extend radially with respect to the rotation axis Y in the radial direction R. The wind turbine 1 includes a permanent magnet generator 6. According to other feasible embodiments of the present invention (not shown in the drawings), the present invention can be applied to other types of motor designs, such as induction motors, synchronous motors, etc. The rotor 4 is rotationally coupled to the permanent magnet generator 6 by a rotatable main shaft 7. The rotatable main shaft 7 extends along the rotation axis Y. The rotor 4 can also be directly rotationally coupled to the permanent magnet generator 6 (direct drive generator configuration). The permanent magnet generator 6 includes a stator 8 and a rotor 9. The rotor 9 is rotatable relative to the stator 8 about the rotation axis Y. The rotor 9 is located radially outside the stator 8 and is rotatable about the rotation axis Y. However, the present invention can also include embodiments not shown, in which the rotor 9 is located radially inside the stator 8. A circumferential air gap 10 is provided between the stator 8 and the rotor 9.

[0070] Each of the three or more blades 5 includes a composite material element having a fabric 20. The manufacture of the composite material element is described in detail below.

[0071] As described above, the fabric can be a non-crimp fabric, a mesh, a veil, a fiber stack, and a semi-finished textile. Other types of fabrics can also be included within the scope of the present invention.

[0072] Figure 2 The fabric 20 according to an embodiment of the present invention is shown. The fabric 20 includes a first fiber layer 21, a second fiber layer 22, a third fiber layer 23, another second fiber layer 22, a fiber layer 24, and a yarn 25 from top to bottom.

[0073] The first fiber layer 21 includes fibers 211 having a first extension direction, the second fiber layer 22 includes fibers 221 having a second extension direction, the third fiber layer 23 includes fibers 231 having a third extension direction, and the fourth fiber layer 24 includes fibers 241 having a fourth extension direction.

[0074] The first extension direction has a relative angle of 0°. The second extension direction has an angle of 90° relative to the first extension direction. The third extension direction has an angle of 45° relative to the first extension direction, and the fourth extension direction has an angle of -45° relative to the first extension direction.

[0075] Thus, the fabric 20 according to Figure 2 has five fiber layers and is four-axis.

[0076] The fibers 211, 221, 231, 241 constituting the layers 21, 22, 23, 24 can be carbon fibers, glass fibers, natural fibers, or synthetic fibers. The layers 21, 22, 23, 24 can be of the same material or different materials.

[0077] The layers 21, 22, 23, 24 are stacked on top of each other but not woven with each other, thus providing a basis for the fabric 20.

[0078] Yarn 25 extends through the first, second, third, and fourth layers 21, 22, 23, 24 and thereby secures them, thus providing a fabric according to an embodiment of the present invention.

[0079] Yarn 25 can be implemented as a monofilament yarn or a multifilament yarn.

[0080] Figures 3a, 3b, and 3c show simplified representations of a warp stitch, a Trickot stitch, and a Tricot-warp stitch according to an exemplary embodiment of the present invention.

[0081] Figure 3a shows a warp stitch. Here, when securing the different fiber layers together, the yarn 25 forms a straight line or path along the first stitch direction 31.

[0082] Figure 3b shows a Trickot stitch. Here, when securing the different fiber layers 21, 22, 23, 24 together, the yarn 25 forms a zigzag path. In other words, i) in the first step, the yarn 25 passes through the fiber layers 21, 22, 23, 24 for the first time along the first diagonal stitching direction 32; then, ii) in the second step, the yarn 25 passes through the fiber layers 21, 22, 23, 24 for the second time along a second diagonal direction 33 different from the first stitching direction 32. In Figure 3b, the second diagonal stitching direction 33 is orthogonal to the first diagonal stitching direction 32.

[0083] Figure 3c shows a Trickot-warp stitch. Here, the yarn 25 first passes through the fiber layers 21, 22, 23, 24 in a first stitching direction 31. In a second step, the yarn 25 passes through the fiber layers 21, 22, 23, 24 in a first diagonal stitching direction 32 in a first diagonal step. In a third step, the yarn 25 passes through the fiber layers 21, 22, 23, 24 in the first stitching direction 31 in a second straight step. In a fourth (and final) step, the yarn 25 passes through the fiber layers 21, 22, 23, 24 in a second diagonal stitching direction 33 in a second diagonal step.

[0084] Figure 4 Shows a simplified diagram of the fabric 20 according to an exemplary embodiment of the present invention. The reference numerals may refer to the above figures.

[0085] In a first step S1, the fiber layers 21, 22, 23, 24 are provided.

[0086] In a second step S2, the fiber layers 21, 22, 23, 24 are stacked on top of each other.

[0087] Meanwhile, in step S3, the yarn 25 is manufactured. The yarn 25 can be manufactured by methods known in the prior art, for example, by melt spinning of the materials constituting the yarn 25.

[0088] The yarn 25 contains at least one epoxy-compatible group and / or a group reactive to epoxy to make it compatible with the material of a composite element, such as the wind turbine blade 5.

[0089] In addition, the yarn 25 can be a monofilament or multifilament yarn, which means it is formed by one thread or multiple threads woven or interlaced with each other.

[0090] Preferably, the yarn 25 is made from used or discarded wind turbine blades. In this case, the used or discarded wind turbine blades can be recycled by providing yarn material.

[0091] In step S4, the yarn 25 passes through the fiber layers 21, 22, 23, 24 and is stitched, preferably by a warp stitch, a Trickot stitch, or a Trickot-warp stitch, to fix the fiber layers 21, 22, 23, 24 to each other.

Claims

1. A fabric (20), comprising: a first fiber layer (21) and a second fiber layer (22), wherein the first fiber layer (21) and the second fiber layer (22) are stacked on top of each other; and a yarn (25), wherein the yarn (25) extends through the first fiber layer (21) and the second fiber layer (22), thereby fixing the first fiber layer (21) to the second fiber layer (22), wherein the yarn (25) is made of or comprises a synthetic material, in particular a thermoplastic material, which has at least one epoxy compatibility group and / or a group reactive to epoxy.

2. The fabric (20) according to claim 1, wherein the thermoplastic material is particularly made of a recycled ketal-based resin or an acetal-based resin.

3. The fabric (20) according to claim 1 or 2, wherein the yarn (25) is a monofilament yarn, particularly wherein the monofilament yarn has a thickness of 10 μm to 400 μm.

4. The fabric (20) according to claim 1 or 2, wherein the yarn (25) is a multifilament yarn, particularly wherein the multifilament yarn has at least two filaments, more particularly wherein each filament has a thickness of 1 μm to 40 μm.

5. The fabric (20) according to any one of claims 1 to 4, wherein the first fiber layer (21) and / or the second fiber layer (22) comprises or is made of at least one of glass fiber, carbon fiber, natural fiber or synthetic fiber.

6. The fabric (20) according to any one of claims 1 to 5, wherein the fiber layers (21) are placed at an angle to each other, particularly wherein the angle is between 0° and 90°.

7. The fabric (20) according to any one of claims 1 to 6, wherein the yarn (25) is stitched through the first fiber layer (21) and the second fiber layer (22), and the stitch is at least one of a warp stitch, a Trickot stitch and a Trickot-warp stitch.

8. The fabric (20) according to any one of claims 1 to 7, wherein the synthetic material of the yarn (25), particularly the thermoplastic material, is made of or comprises a recycled material having at least one epoxy compatibility group and / or a group reactive to epoxy, particularly a material from recycled wind turbine blade material (5).

9. A composite element, particularly a turbine blade (5) or a part thereof, comprising at least one fabric (20) according to any one of claims 1 to 8.

10. The composite material element according to claim 9, further comprising: a resin at least partially encapsulating the fabric (20), particularly wherein the resin comprises at least one epoxy compatibility group and / or a group reactive to epoxy and / or is compatible with at least one epoxy compatibility group and / or a group reactive to epoxy.

11. A wind turbine (1), comprising at least one composite element according to claim 9 or 10.

12. A method of manufacturing a fabric (20), the method comprising: placing a first fiber layer (21) on top of a second fiber layer (22), providing a yarn (25), and The yarn (25) is passed through and stitched to the first fiber layer (21) and the second fiber layer (22), thereby fixing the first fiber layer (21) and the second fiber layer (22) using at least one yarn (25). wherein the yarn (25) is made of or comprises a synthetic material, in particular a thermoplastic material, which has at least one epoxy-compatible group and / or a group reactive to epoxy.

13. The method according to claim 12, wherein providing the yarn (25) further comprises:[[]] recycled material, in particular material from the turbine blade material (5), which material comprises at least one epoxy-compatible group and / or a group reactive to epoxy, to manufacture the yarn (25).

14. Using a turbine blade (5) made of a material comprising at least one epoxy-compatible group and / or a group reactive to epoxy as a starting material to manufacture a yarn (25) comprising said at least one epoxy-compatible group.

15. Using the yarn (25) to fix fiber layers (21, 22, 23, 24), the yarn comprising or consisting of a synthetic material, in particular a thermoplastic material, having at least one epoxy-compatible group and / or a group reactive to epoxy, the fiber layers (21, 22, 23, 24) respectively comprising or consisting of another synthetic material, in particular a thermoplastic material, having at least one additional epoxy-compatible group and / or a group reactive to epoxy.

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