Woven fabric, vacuum-induced resin infusion process, and fiber-reinforced composite

Abstract

The invention relates to a woven fabric for manufacturing fiber reinforced composites having an areal weight of 100 g / m 2 to 200 g / m 2 and comprising unidirectional reinforcing fibers, carbon fibers and flow channel forming elements arranged in the warp direction and / or the weft direction and optionally additives. The flow channel forming elements are crisscross arranged with respect to the reinforcing fibers and carbon fibers to form flow channels at the sides of the flow channel forming elements. Furthermore, the invention relates to a vacuum induced resin infusion process for forming a fiber reinforced composite from such a woven fabric and to the fiber reinforced composite.

Description

[0001] This invention relates to woven fabrics for manufacturing fiber-reinforced composite materials, having an area weight of 100 g / m². 2 Up to 200g / m 2 The material comprises unidirectional reinforcing fibers, carbon fibers, and flow channel forming elements arranged along the warp and / or weft directions, as well as optional additives. The flow channel forming elements are arranged transversely relative to the reinforcing fibers and carbon fibers to form flow channels on the sides of the flow channel forming elements. Furthermore, the present invention relates to a vacuum-induced resin infusion process for forming fiber-reinforced composites from such woven fabrics, and to said fiber-reinforced composites.

[0002] The market demand for wind turbine rotor blades involves placing fabric between the pultruded carbon profiles of the blade's sparsity structure. The fabric doesn't necessarily need to play a significant role in providing stiffness or other mechanical properties to the blade, but it does need to conduct electricity in different directions. This is to provide conductive paths for, for example, lightning current protection devices, as described in Madsen S., Caroni, L., Lightning exposure of Carbon Fiber Composites in wind turbineblades, Proceedings of the Nordic Insulation Symposium DOI:10.5324 / nordis.v0i24.2293. Furthermore, lateral permeability (based on the permeability constant K22) is required to ensure good wetting and venting between the carbon laminates of the sparsity cap.

[0003] Alternatively, the main spars can be made of a hybrid glass / carbon unidirectional (UD) fabric or a hybrid UD pultruded laminate instead of a pultruded carbon laminate, but in this case, the primary purpose of the intermediate fabric remains unchanged.

[0004] The use of flow-promoting fabrics in composite materials is well-known, and various solutions exist. US5484642 teaches the use of woven fabrics with a basic circular thread composed of helically twisted multifilament yarns to form flow channels. Similarly, WO 2020 / 182908 A1 teaches the use of unreinforced twisted multifilament yarns with a modulus less than 10 GPa in stitch-reinforcing materials used to form resin flow channels. However, EP 3 174 704 A1 describes the use of an infusion-promoting layer in wind turbine blades, which is a fabric comprising multiple twisted yarns.

[0005] Existing conductive solutions for intermediate fabrics on the market: 150g / m 2The layered, low-weight carbon biaxial fabric (e.g., CARBON BIAX 300 45 / 45) is used. In this case, the main flowability is achieved by using tex sewing thread in the biaxial fabric to ensure sufficient free thickness between the laminates. The disadvantages of using this carbon biaxial fabric are obvious because of the large amount of carbon fiber in these directions of the blade spars. Regarding conductivity, the large amount of carbon fiber results in such high conductivity that it completely exceeds the necessary requirements for this rotor blade. Furthermore, this solution has a higher weight and results in higher production costs.

[0006] Furthermore, EP 3 419 816 A1 teaches the use of flow layers interleaved with dry-reinforced stacks. These flow layers may comprise filaments or bundles of a conductive second material. However, they teach that the second material be positioned at an angle of 15 to 75 degrees relative to the transverse direction to ensure good electrical contact. However, this arrangement is difficult to manufacture, and in practice, the second material needs to be added in a second step.

[0007] Therefore, the object of the present invention is to provide a fiber-reinforced composite material based on woven fabric that has reduced weight and sufficient electrical conductivity, and is easy to manufacture and inexpensive.

[0008] This problem is solved by the woven fabrics having the features of this application, the vacuum-induced resin infusion process of this application, and the fiber-reinforced composite materials of this application. Further embodiments mention preferred embodiments.

[0009] According to the present invention, a woven fabric for manufacturing fiber-reinforced composite materials is provided, having an area weight of 50 g / m². 2 Up to 300g / m 2 and includes or constitutes:

[0010] a) 30% to 75% by weight of unidirectional reinforcing fibers arranged along the warp and / or weft directions (preferably along the warp direction), wherein the reinforcing fibers are selected from glass fibers, ceramic fibers, and combinations thereof.

[0011] b) 20% to 50% by weight of conductive fibers arranged along the warp and / or weft directions.

[0012] c) 2% to 10% by weight of flow channel forming elements arranged along the warp and / or weft directions (preferably arranged along the weft direction), and

[0013] d) At least one additive, ranging from 0% to 5% by weight (optionally 0% by weight of at least one additive, i.e., no additive),

[0014] The total weight of components a)) to d) is 100.

[0015] The flow channel forming elements are substantially transversely arranged relative to the reinforcing fibers and conductive fibers to form flow channels on the sides of the flow channel forming elements. In the context of this invention, the substantially transverse arrangement of the reinforcing fibers and conductive fibers means that the fibers are arranged at an angle of 75° to 105°, preferably 80° to 100°, and more preferably 85° to 95°. In a particularly preferred embodiment, the reinforcing fibers and conductive fibers are transversely arranged relative to each other.

[0016] This invention is based on the idea that, in addition to using conductive fibers such as carbon fiber, other materials are used to replace conductive fibers. These fibers unexpectedly allow for a synergistic effect of good flow properties, sufficient conductivity, good processability of woven fabrics, and good interlaminar shear properties.

[0017] Preferably, the areal weight of the woven fabric is 70 g / m². 2 Up to 250g / m 2 Preferably 100g / m 2 Up to 200g / m 2 .

[0018] Preferably, the flow channel forming element is selected from polymer monofilaments (polymer monofilament yarn), more preferably from polyethylene terephthalate (PET), polypropylene, polybutylene terephthalate, polyamide (PA), and combinations thereof.

[0019] According to a preferred embodiment, the diameter of the flow channel forming element is 50 μm to 350 μm, preferably 120 μm to 200 μm.

[0020] Preferably, the distance between the flow channel forming elements is 2 mm to 8 mm, more preferably 3 mm to 5 mm.

[0021] The flow channel forming element preferably comprises a bundle of at least one and at most five monofilaments.

[0022] The reinforcing fiber is preferably flat glass fiber. Preferably, the diameter of the reinforcing fiber is 4µm to 30µm, more preferably 10µm to 20µm. Furthermore, the reinforcing fiber is preferably present as roving in the woven fabric.

[0023] Preferably, the conductive fiber is selected from carbon fiber, recycled carbon fiber, metal wire, glass yarn wound with metal wire, metal-coated synthetic yarn such as polyamide, polyester, polypropylene or other synthetic yarn, and combinations thereof. The diameter of the conductive fiber is preferably from 4 μm to 30 μm, more preferably from 5 μm to 20 μm, and even more preferably from 6 μm to 10 μm. The carbon fiber is preferably recycled carbon fiber. Furthermore, preferably, the conductive fiber is present as roving.

[0024] Preferably, the additive is an adhesion promoter to optimize the adhesion between the fabric and the resin used subsequently. Additionally, bicomponent / low-melting-point yarns can also be used to increase fabric stability by creating adhesion between the longitudinal and transverse fiber directions.

[0025] According to a preferred embodiment, the woven fabric comprises or consists of

[0026] a) 40% to 70% by weight of unidirectional reinforcing fibers arranged along the warp and / or weft directions (preferably along the warp direction),

[0027] b) 25% to 45% by weight of carbon fibers arranged along the warp direction and

[0028] c) 3% to 8% by weight of flow channel forming elements arranged along the warp and / or weft directions (preferably arranged along the weft direction),

[0029] d) At least one additive, ranging from 0% to 5% by weight (optionally 0% by weight of at least one additive, i.e., no additive),

[0030] The total weight of components a) to d) is 100.

[0031] The resistivity of the woven fabric measured on a 12cm×12cm sample in the warp and / or weft directions is preferably <20 ohm, preferably <10 ohm, and more preferably <5 ohm.

[0032] According to the present invention, a vacuum-induced resin infusion process for forming fiber-reinforced composite materials is also provided, the process comprising or consisting of the following steps:

[0033] a) Provide a woven fabric according to the invention.

[0034] b) Encapsulating the woven fabric within a substantially airtight housing, having at least one means for applying a vacuum and at least one means for supplying a curable resin to the housing.

[0035] c) Applying a vacuum to the casing using at least one device for applying a vacuum and at least one other device.

[0036] d) Introducing the curable resin through at least one device for supplying the curable resin to the casing, and

[0037] e) Curing the resin to form a fiber-reinforced composite material.

[0038] Preferably, at least one device for applying a vacuum and at least one device for supplying curable resin to the housing are located on opposite sides of the housing.

[0039] According to the present invention, a fiber-reinforced composite material is also provided, comprising the woven fabric as described above and an infused and cured resin.

[0040] Referring to the following figures and embodiments, the subject matter according to the invention is intended to be explained in more detail, without intending to limit the subject matter to the specific embodiments shown herein.

[0041] Figure 1 This is a graph showing the flow rate of the fabric in Comparative Example 1.

[0042] Figure 2 This is a graph showing the flow rate of the fabric in Comparative Example 2.

[0043] Figure 3 This is a graph showing the flow rate of the fabric in Example 1.

[0044] Figure 4 This is a top view of the fabric according to the present invention.

[0045] Figure 5 This is a graph showing the flow rate of the fabric in Example 2.

[0046] Comparative Example 1

[0047] Starting with a glass warp fabric, its transverse flow properties are first evaluated. Carbon fiber is not included at this stage.

[0048] The test fabric (TEST2599) has the following structure:

[0049] Woven pattern: Plain weave

[0050] Table 1 mentions the fibers used in Comparative Example 1.

[0051] Table 1

[0052]

[0053] The total weight of the fabric is 152g / m². 2 .

[0054] Injection device

[0055] The infusion performance was tested using the following apparatus:

[0056] • The dimensions of the precast component are 400mm × 600mm (width × length).

[0057] • Test 10 layers in a 90° direction (weft direction = K22)

[0058] Resin system

[0059] Use the following resins and initiators:

[0060] Resin: Ashland AME 6001 INF-135 (VE)

[0061] Initiator: Norox MCP-75 1.5%

[0062] result

[0063] Figure 1 The relationship between the flow rate of the fabric in Comparative Example 1 and the flow distance versus time is shown. It was observed that the fabric in Comparative Example 1 exhibited excessively high flow rates. Therefore, it was concluded that the diameter of the monofilament yarn used for flow enhancement must be reduced.

[0064] Comparative Example 2

[0065] Further infusion was performed to optimize flow properties and resin consumption. Flow properties were tested using monofilaments with diameters of 0.25 mm and 0.14 mm. The next fabric was made using smaller filament diameters.

[0066] The second test fabric (TEST2582) has the following structure:

[0067] Woven pattern: Plain weave

[0068] Table 2 mentions the fibers used in Comparative Example 2.

[0069] Table 2

[0070]

[0071] The total weight of the fabric is 123g / m². 2 .

[0072] Injection device

[0073] The infusion apparatus and other parameters are the same as those in the first infusion apparatus (Comparative Example 1).

[0074] result

[0075] Figure 2 The relationship between the flow rate of the fabric in the preliminary test and the flow distance and time is shown. It was observed that the fabric of Comparative Example 2 had a lower flow rate than that of Comparative Example 1; however, its flow rate was still too high. Therefore, it is still necessary to reduce the flow rate.

[0076] Example 1

[0077] In further experiments, carbon fiber was used in the weft direction.

[0078] The carbon fiber in the weft direction was chosen to be 3K because it has the same tex as the warp direction. Using a higher tex would create a raised effect on the fabric. The weft monofilament area weight is only 5g / m². 2It should provide sufficient stability for the fabric and, together with the additional carbon, provide infusibility.

[0079] The test fabric ((TEST3010)) has the following structure:

[0080] Woven pattern: Plain weave

[0081] Table 3 mentions the fibers used in Example 1.

[0082] Table 3

[0083]

[0084] The total weight of the fabric is 123g / m². 2 .

[0085] Injection device

[0086] The infusion apparatus and other parameters were the same as those in Comparative Examples 1 and 2.

[0087] result

[0088] Compared to the comparative example, the fabric's permeability was improved. 27% of the fabric weight (36 g / m²) 2 ) refers to carbon fibers arranged along the weft direction.

[0089] Example 2

[0090] Further experiments were conducted with monofilaments of different diameters. When using a fiber diameter of 140µm, a suitable flow regime was estimated to be achieved (50cm width, approximately 10 minutes). In this case, carbon (3K) was also added in both the warp and weft directions. Adding carbon in the warp direction did not appear to have a significant impact on the fabric's flow properties. The carbon fibers in the weft direction increased the fabric thickness, thereby enhancing flowability.

[0091] The test fabric (TEST2915) has the following structure:

[0092] Woven pattern: Plain weave

[0093] Table 4 mentions the fibers used in Example 2.

[0094] Table 4

[0095]

[0096] The total weight of the fabric is 136g / m². 2 .

[0097] Injection device

[0098] The infusion performance was tested using the following apparatus:

[0099] • The dimensions of the precast component are 400mm × 600mm (width × length).

[0100] • Test 10 layers in a 90° direction (weft direction)

[0101] Fabric structure such as Figure 4 As shown.

[0102] Resin system

[0103] Use the following resins and initiators:

[0104] Resin: Ashland AME 6001 INF-135 (VE)

[0105] Initiator: Norox MCP-75 1.5%

[0106] result

[0107] The infusion results were quite surprising because it was fast enough and the fabric's area weight was remarkably low (136 g / m²). 2 (See also) Figure 5 ).

[0108] The desired level of infusibility was achieved, and the material's conductivity was found to be within the target range. Conductivity can be adjusted quite easily by replacing the warp glass rovings with carbon fibers or the weft monofilaments with carbon fibers. Changes in the warp yarns have little effect on flow properties, while changes in the weft yarns must be evaluated on a case-by-case basis.

Claims

1. A woven fabric for manufacturing fiber-reinforced composite materials, having an area weight of 50 g / m². 2 Up to 300g / m 2 and includes or constitutes a) 30% to 75% by weight of unidirectional reinforcing fibers arranged along the warp and / or weft directions, wherein the reinforcing fibers are selected from glass fibers, ceramic fibers, and combinations thereof. b) 20% to 50% by weight of conductive fibers arranged along the warp and / or weft directions. c) 2% to 10% by weight of flow channel forming elements arranged along the warp and / or weft directions, wherein the flow channel forming elements are selected from monofilament yarn, glass yarn, carbon yarn, twisted yarn, covered yarn, and combinations thereof, and d) At least one additive, ranging from 0% to 5% by weight. The total amount of components a) to d) is 100% by weight, and The flow channel forming elements are basically arranged transversely relative to the reinforcing fibers, and flow channels are formed on the sides of the flow channel forming elements.

2. The woven fabric according to claim 1, Its features are, The area weight of the woven fabric is 70 g / m². 2 Up to 250g / m 2 .

3. The woven fabric according to claim 1, Its features are, The area weight of the woven fabric is 100 g / m². 2 Up to 200g / m 2 .

4. The woven fabric according to claim 1 or 2, Its features are, The flow channel forming element is selected from polymer monofilaments.

5. The woven fabric according to claim 1 or 2, Its features are, The flow channel forming element is selected from polyethylene terephthalate (PET), polypropylene, polybutylene terephthalate, polyamide (PA), and combinations thereof.

6. The woven fabric according to claim 1 or 2, Its features are, The diameter of the flow channel forming element is from 50 μm to 350 μm.

7. The woven fabric according to claim 1 or 2, Its features are, The diameter of the flow channel forming element is 120 μm to 200 μm.

8. The woven fabric according to claim 1 or 2, Its features are, The distance between the flow channel forming elements is 2mm to 8mm.

9. The woven fabric according to claim 1 or 2, Its features are, The distance between the flow channel forming elements is 3mm to 5mm.

10. The woven fabric according to claim 1 or 2, Its features are, The flow channel forming element comprises a bundle of at least one and at most five monofilaments.

11. The woven fabric according to claim 1 or 2, Its features are, The diameter of the reinforcing fibers ranges from 4µm to 30µm, and the reinforcing fibers exist as rovings.

12. The woven fabric according to claim 1 or 2, Its features are, The diameter of the reinforcing fibers is 10µm to 20µm, and the reinforcing fibers exist as rovings.

13. The woven fabric according to claim 1 or 2, Its features are, The conductive fibers are selected from carbon fiber, recycled carbon fiber, metal wire, glass yarn wound with metal wire, metal-coated synthetic yarn, and combinations thereof. The diameter of the conductive fibers ranges from 4µm to 30µm.

14. The woven fabric according to claim 1 or 2, Its features are, The conductive fibers are selected from carbon fiber, recycled carbon fiber, metal wire, glass yarn wound with metal wire, metal-coated synthetic yarn, and combinations thereof. The diameter of the conductive fibers ranges from 5µm to 20µm.

15. The woven fabric according to claim 1 or 2, Its features are, The conductive fibers are selected from carbon fiber, recycled carbon fiber, metal wire, glass yarn wound with metal wire, metal-coated synthetic yarn, and combinations thereof. The diameter of the conductive fibers ranges from 6µm to 10µm.

16. The woven fabric according to claim 13, Its features are, Synthetic yarn is polyamide synthetic yarn, polyester synthetic yarn, polypropylene synthetic yarn or other synthetic yarn.

17. The woven fabric according to claim 1 or 2, Its features are, The conductive fiber exists as roving.

18. The woven fabric according to claim 1 or 2, Its features are, Additives are selected from • At least one adhesion promoter, as a coating for the fabric, to optimize the adhesion between the fabric and the resin used subsequently. • At least one bicomponent yarn used for the mechanical connection between transversely and longitudinally oriented fibers, and • Its combination.

19. The woven fabric according to claim 1 or 2, Its features are, Woven fabrics include or consist of a) 40% to 70% by weight of unidirectional reinforcing fibers arranged along the warp and / or weft directions. b) 25% to 45% by weight of carbon fibers arranged along the warp and / or weft directions and c) 3% to 8% by weight of flow channel forming elements arranged along the warp and / or weft directions. The total amount of components a) to d) is 100 by weight.

20. The woven fabric according to claim 1 or 2, Its features are, The resistivity of the woven fabric measured in the warp and / or weft directions on a 12cm×12cm sample is < 20 ohm.

21. The woven fabric according to claim 1 or 2, Its features are, The resistivity of the woven fabric measured in the warp and / or weft directions on a 12cm×12cm sample is < 10 ohm.

22. The woven fabric according to claim 1 or 2, Its features are, The resistivity of the woven fabric measured in the warp and / or weft directions on a 12cm×12cm sample is < 5 ohm.

23. A vacuum-induced resin infusion process for forming fiber-reinforced composite materials, comprising the following steps: a) Providing a woven fabric according to any one of claims 1 to 22, b) Encapsulating the woven fabric within a substantially airtight housing, having at least one means for applying a vacuum and at least one means for supplying a curable resin to the housing. c) Applying a vacuum to the casing using at least one device for applying a vacuum and at least one other device. d) Introducing the curable resin through at least one device for supplying the curable resin to the casing, and e) Curing the resin to form a fiber-reinforced composite material.

24. The process according to claim 23, Its features are, At least one device for applying a vacuum and at least one device for supplying curable resin to the housing are located on opposite sides of the housing.

25. A fiber-reinforced composite material comprising a woven fabric according to any one of claims 1 to 22 and a resin that has been infused and cured.

Images