A fan blade core material and a design method thereof

Abstract

The application discloses a fan blade core material and a design method thereof. The core material comprises a foam plate, glass fiber bundles, resin and a skin. The glass fiber bundles are embedded in the foam plate at preset embedding angles and penetrate through opposite two surfaces of the foam plate, and the glass fiber bundles are spaced apart by a preset distance. The resin is vacuum injected into the aperture of each glass fiber bundle and is tightly connected with the glass fiber bundle. The skin is arranged at the opposite two surfaces of the foam plate and is bonded with the glass fiber bundle. In the foam core material, the glass fiber is embedded into the high-performance foam core material at multiple angles. The glass fiber penetrates through the foam structure to form a three-dimensional network structure, which can improve the limitation of the Z-Pin structure in edge contour reinforcement, improve the shearing and bearing capacity of the sandwich structure, and also can retain the advantages of the stitched reinforced sandwich structure, such as simple manufacturing process, convenient operation and good surface-core bonding performance.

Description

Technical Field

[0001] This invention relates to the technical field of wind turbine blades, and in particular to a wind turbine blade core material and its design method. Background Technology

[0002] With the gradual maturation of onshore wind power and the booming development of offshore wind power, how to reduce the cost and weight of wind turbine blades has become a major theme in wind turbine blade research. The main contributions to weight reduction in blades come from new processes and materials. Weight reduction relies heavily on new blade materials, which represent a crucial direction for future cost reduction. For both onshore and offshore blades, resins, fiberglass, and various auxiliary materials have already achieved mass production, while the use of high-performance foams such as PET and PVC to replace balsa wood is only beginning to be used in some areas of blades.

[0003] Traditional core material structures suffer from poor interfacial bonding between the skin and core, and low core strength, resulting in low Z-axis strength, stiffness, and impact damage tolerance. This severely limits the application of composite core material structures in load-bearing structures. Z-axis reinforcement technology is an effective reinforcement solution proposed to address the shortcomings of traditional foam sandwich composites in areas such as face / core debonding and shear performance. As the preparation process of Z-axis reinforced foam sandwich composites matures and research into their structure and properties deepens, market acceptance of this structure is increasing. Therefore, replacing balsa wood with high-performance foam core materials through Z-axis reinforcement technology is particularly important for achieving blade weight reduction and improving the modulus of existing core materials. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a wind turbine blade core material and its design method. This method involves pre-embedding glass fibers into a high-performance foam core material at multiple angles. The glass fibers penetrate the foam structure to form a three-dimensional network structure, which improves the limitations of Z-Pin structures in edge contour reinforcement, enhances the shear and load-bearing capacity of sandwich structures, and retains the advantages of stitch-reinforced sandwich structures, such as simple manufacturing process, convenient operation, and good face-core bonding performance.

[0005] The present invention is achieved through the following technical solution: a wind turbine blade core material, comprising a foam board, glass fiber bundles, resin and a skin; the glass fiber bundles are embedded in the foam board at a preset pre-embedded angle and penetrate through the opposite sides of the foam board, and the glass fiber bundles are spaced apart by a preset distance; the resin is vacuum-injected into the pores of each glass fiber bundle and forms a tight connection with the glass fiber bundle; the skin is respectively disposed on the opposite sides of the foam board and is bonded to the glass fiber bundle.

[0006] Furthermore, the glass fiber bundle is an untwisted glass fiber yarn.

[0007] Furthermore, the cross-sectional shape of the pores of the glass fiber bundle is elliptical, circular, or rectangular.

[0008] Furthermore, the distance between each glass fiber bundle is 20-30 mm.

[0009] Furthermore, the adjacent transverse rows of pre-embedded glass fiber bundles alternate at 180°.

[0010] Furthermore, the foam board is a PET high-performance foam board or a PVC high-performance foam board.

[0011] The present invention provides a design method for the above-mentioned wind turbine blade core material, comprising the following steps:

[0012] S1. Based on the stress characteristics of the wind turbine blades, perform finite element analysis on the wind turbine blade model to determine the design requirements for the wind turbine blade core material;

[0013] S2. Prepare wind turbine blade core material samples. Cut the wind turbine blade core material samples into shear test pieces and fatigue test pieces.

[0014] S3. Perform shear performance verification tests on the shear test specimen and fatigue bending verification tests on the fatigue test specimen to verify the shear performance and fatigue bending performance of the wind turbine blade core material.

[0015] Furthermore, step S1 includes the following steps:

[0016] Based on the stress characteristics of wind turbine blades, finite element analysis is performed on a full-size wind turbine blade model. According to the DNV-GL specification, failure verification analysis is conducted on the leading and trailing edge analysis positions of the blades based on ultimate loads and fatigue loads. Ultimate design and fatigue design loads for component-level testing are derived as input design requirements for component-level testing.

[0017] Furthermore, step S2 includes the following steps:

[0018] S201. Determine the shape and size of the wind turbine blade core material sample according to the design requirements obtained in step S1;

[0019] S202. Using the parametric finite element analysis method, with the glass fiber bundles arranged at a preset spacing, the pre-embedded angle of the glass fiber bundles is changed to obtain the optimal pre-embedded angle ratio.

[0020] S203. According to the preset spacing and the optimal pre-embedding angle ratio, the glass fiber bundles are pre-embedded into the foam board to obtain the core material preform.

[0021] S204. Lay the permeable and easily cut glass fiber fabric flat, close and wrinkle-free on the core material preform, and constrain the glass fiber bundles pre-embedded in step S203 within the glass fiber fabric.

[0022] S205. The core material preform is cured by vacuum infusion resin molding process to obtain a wind turbine blade core material sample. The obtained wind turbine blade core material sample is cut into shear test pieces and fatigue test pieces.

[0023] Furthermore, step S3 includes the following steps:

[0024] Test the out-of-plane shear modulus effect, out-of-plane shear strength effect, and adhesion of the shear test specimen. Repeat the above shear performance test at least 6 times to meet the design certification requirements.

[0025] The fatigue test specimen is loaded to ensure that the fatigue damage of the obtained fatigue test specimen is closer to the fatigue failure caused by the target load;

[0026] The fatigue test load is calculated using the following formula:

[0027] F text ≥F equivalent ·γ nf ·γ sf ·γ ef ;

[0028] Among them, F text For fatigue testing load; F equivalent The equivalent force under design damage is related to the number of load cycles; γ nf γ is the load enhancement factor for the local fatigue bending test of the full-size blade, taken as 1.15; sf The coefficient of variation for the full-size blade fatigue bending test is taken as 1.1; γ ef The error compensation factor for the fatigue formula in the full-size blade fatigue bending test is set to 1.05.

[0029] The SN curve of the fatigue test specimen is tested, the number of load cycles is recorded, the signal used for blade testing and the measurement position of the fatigue test are controlled, and the SN curve with a 95% confidence interval is obtained by statistical processing for each fatigue test series, thus completing the fatigue bending performance verification.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] 1. This invention can combine glass fiber bundles pre-embedded in foam with the upper and lower skins at different angles, pore sizes and densities according to the shape requirements of the blade, so as to achieve customized processing of the blade core material;

[0032] 2. Pre-embedded glass fiber bundles replace the grooving of foam boards, reducing the grooving process and high processing costs. While providing flow channels for vacuum resin infusion, the resin in the holes cures and forms a riveting-like structure with the pre-embedded glass fiber bundles, which enhances the adhesion strength between the fiberglass and the core material.

[0033] 3. By pre-embedding glass fiber to connect the skin, its curing can effectively improve the adhesion between the skin and the foam core of the reinforced core material composite material, and prevent the skin and core material from peeling off prematurely. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the core material of a wind turbine blade.

[0035] Figure 2 This is a cross-sectional view of the core material of a wind turbine blade.

[0036] Figure 3 This is a cross-sectional view of the structure of a glass fiber bundle.

[0037] Figure 4 A schematic diagram of a structure in which glass fiber bundles are pre-embedded in two adjacent horizontal rows, alternating at 180°.

[0038] Figure 5 This is a schematic diagram of the manufacturing process of wind turbine blade core material.

[0039] Figure 6 This is a schematic diagram of the shear performance test.

[0040] Figure 7 This is a schematic diagram of a fatigue bending test. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments.

[0042] Example 1

[0043] See Figures 1 to 4 As shown, the core material of the wind turbine blade provided in this embodiment includes a foam board, glass fiber bundles, resin, and skin.

[0044] Multiple glass fiber bundles are embedded in the foam board at preset angles, penetrating both opposite sides of the foam board, with a 20mm spacing between each bundle. The glass fiber bundles are untwisted glass fiber yarn, which is easily impregnated with resin, easily flattened, and easily removes air bubbles, resulting in better adhesion to the skin. The resin is vacuum-injected into the pores of each glass fiber bundle, forming a tight bond. The skin is located on both opposite sides of the foam board and bonded to the glass fiber bundles. The pore cross-sectional shape of the glass fiber bundles is elliptical, circular, or rectangular. Adjacent horizontal rows of embedded glass fiber bundles alternate at 180°. The foam board is a PET high-performance foam board or a PVC high-performance foam board. The pre-embedded angle of the glass fiber bundle is 0 / 90°, ±30°, ±45°, ±60° or ±75°. The material has the best in-plane compressive performance at 0 / 90° and the best shear performance at ±45°. Core materials with different pre-embedded glass fiber angles are prepared according to the different performance requirements of each region of the leading and trailing edges of the wind turbine blade.

[0045] The adjacent horizontal rows of pre-embedded glass fiber bundles alternate at 180°: the pre-embedded entry and exit angles are ∠1=∠2, the pre-embedded angles are ∠1=∠4, ∠4+∠3=180°, and the glass fiber bundle transition angle is ∠2+∠3=180°.

[0046] See Figures 5 to 7 As shown, the design method for the wind turbine blade core material provided in this embodiment includes the following steps:

[0047] S1. Based on the stress characteristics of the wind turbine blades, perform finite element analysis on the wind turbine blade model to determine the design requirements for the wind turbine blade core material, including the following steps:

[0048] Based on the stress characteristics of wind turbine blades, finite element analysis is performed on a full-size wind turbine blade model. According to the DNV-GL specification, failure verification analysis is conducted on the leading and trailing edge analysis positions of the blades based on ultimate loads and fatigue loads. Ultimate design and fatigue design loads for component-level testing are derived as input design requirements for component-level testing.

[0049] S2. Prepare wind turbine blade core material samples. Cut the wind turbine blade core material samples into shear test pieces and fatigue test pieces, including the following steps:

[0050] S201. Determine the shape and size of the wind turbine blade core material sample according to the design requirements obtained in step S1;

[0051] S202. Using the parametric finite element analysis method, with the glass fiber bundles arranged at a preset spacing, the pre-embedded angle of the glass fiber bundles is changed to obtain the optimal pre-embedded angle ratio.

[0052] S203. According to the preset spacing and the optimal pre-embedding angle ratio, the glass fiber bundles are pre-embedded into the foam board to obtain the core material preform.

[0053] S204. Lay the permeable and easily cut glass fiber fabric flat, close and wrinkle-free on the core material preform, and constrain the glass fiber bundles pre-embedded in step S203 within the glass fiber fabric.

[0054] S205. The core material preform is cured by vacuum infusion resin molding process to obtain a wind turbine blade core material sample. The obtained wind turbine blade core material sample is cut into shear test pieces and fatigue test pieces.

[0055] S3. Perform shear performance verification tests on the shear test specimen and fatigue bending verification tests on the fatigue test specimen to verify the shear performance and fatigue bending performance of the wind turbine blade core material, including the following steps:

[0056] By introducing glass fiber bundles into the foam board, the glass fiber bundles exposed on the foam surface are embedded in the skin during layup, connecting the core material with the upper and lower skins as one unit, improving the bonding performance between the skin and the core material. The resulting truss structure can withstand shear and compressive loads, and the foam also provides lateral support for the stability of the glass fiber bundles. The out-of-plane shear modulus effect, out-of-plane shear strength effect, and adhesion of the shear test specimen are tested. The above shear performance tests are repeated for no less than 6 times to meet the design certification requirements.

[0057] Under bending and axial pressure F, composite structures are prone to instability. Instability failure always occurs at the compression site before the material reaches compressive strength. By pre-embedding glass fiber bundles inside the core material for reinforcement, the glass fiber bundles are combined with the skin to improve the integrity of the adhesive surface to resist buckling. The fatigue test specimen is loaded to ensure that the fatigue damage of the obtained fatigue test specimen is closer to the fatigue failure caused by the target load, where l1 is the support span and l2 is the loading span.

[0058] The fatigue test load is calculated using the following formula:

[0059] F text ≥F equivalent ·γ nf ·γ sf ·γ ef ;

[0060] Among them, F text For fatigue testing load; F equivalent For equivalent force under design damage; γ nf γ is the load enhancement factor for the local fatigue bending test of the full-size blade, taken as 1.15; sfThe coefficient of variation for the full-size blade fatigue bending test is taken as 1.1; γ ef The error compensation factor for the fatigue formula in the full-size blade fatigue bending test is set to 1.05.

[0061] The SN curve of the fatigue test piece needs to be tested, the number of load cycles needs to be recorded, the signal used for blade testing and the measurement position of the fatigue test need to be controlled, and the SN curve with a 95% confidence interval needs to be obtained by statistical processing for each fatigue test series, thus completing the fatigue bending performance verification.

[0062] Example 2

[0063] Unlike Example 1, the glass fiber bundles are spaced 30 mm apart.

[0064] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, any changes made in accordance with the shape and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A design method for the core material of a wind turbine blade, characterized in that: The core material of the wind turbine blade includes a foam board, glass fiber bundles, resin, and a skin. Multiple glass fiber bundles are embedded in the foam board at preset angles, penetrating both opposite sides of the foam board, and spaced at preset distances. The resin is vacuum-injected into the pores of each glass fiber bundle, forming a tight connection with it. The skin is located on both opposite sides of the foam board and is bonded to the glass fiber bundles. Adjacent transverse rows of embedded glass fiber bundles alternate at 180°. This design method includes the following steps: S1. Based on the stress characteristics of the wind turbine blades, perform finite element analysis on the wind turbine blade model to determine the design requirements for the wind turbine blade core material; S2. Prepare wind turbine blade core material samples. Cut the wind turbine blade core material samples into shear test pieces and fatigue test pieces. S3. Conduct shear performance verification tests on the shear test specimens and fatigue bending verification tests on the fatigue test specimens to verify the shear performance and fatigue bending performance of the wind turbine blade core material; test the out-of-plane shear modulus effect, out-of-plane shear strength effect, and adhesion of the shear test specimens, and repeat the shear performance test no less than 6 times to meet the design certification requirements. The fatigue test specimen is loaded to ensure that the fatigue damage of the obtained fatigue test specimen is closer to the fatigue failure caused by the target load; The fatigue test load is calculated using the following formula: F text ≥F equivalent ·c nf ·c sf ·c ef ; Among them, F text For fatigue testing load; F equivalent The equivalent force under design damage is related to the number of load cycles; γ nf γ is the load enhancement factor for the local fatigue bending test of the full-size blade, taken as 1.15; sf The coefficient of variation for the full-size blade fatigue bending test is taken as 1.1; γ ef The error compensation factor for the fatigue formula in the full-size blade fatigue bending test is set to 1.

05. The SN curve of the fatigue test specimen is tested, the number of load cycles is recorded, the signal used for blade testing and the measurement position of the fatigue test are controlled, and the SN curve with a 95% confidence interval is obtained by statistical processing for each fatigue test series, thus completing the fatigue bending performance verification.

2. The design method for a wind turbine blade core material according to claim 1, characterized in that: The glass fiber bundle is an untwisted glass fiber yarn.

3. The design method for a wind turbine blade core material according to claim 1, characterized in that: The cross-sectional shape of the glass fiber bundle is elliptical, circular, or rectangular.

4. The design method for a wind turbine blade core material according to claim 1, characterized in that: The distance between each glass fiber bundle is 20-30mm.

5. The design method for a wind turbine blade core material according to claim 1, characterized in that: The foam board is a PET high-performance foam board or a PVC high-performance foam board.

6. The design method for a wind turbine blade core material according to claim 1, characterized in that, Step S1 includes the following steps: Based on the stress characteristics of wind turbine blades, finite element analysis is performed on a full-size wind turbine blade model. According to the DNV-GL specification, failure verification analysis is conducted on the leading and trailing edge analysis positions of the blades based on ultimate loads and fatigue loads. Ultimate design and fatigue design loads for component-level testing are derived as input design requirements for component-level testing.

7. The design method for a wind turbine blade core material according to claim 1, characterized in that, Step S2 includes the following steps: S201. Determine the shape and size of the wind turbine blade core material sample according to the design requirements obtained in step S1; S202. Using the parametric finite element analysis method, with the glass fiber bundles arranged at a preset spacing, the pre-embedded angle of the glass fiber bundles is changed to obtain the optimal pre-embedded angle ratio. S203. According to the preset spacing and the optimal pre-embedding angle ratio, the glass fiber bundles are pre-embedded into the foam board to obtain the core material preform. S204. Lay the permeable and easily cut glass fiber fabric flat, close and wrinkle-free on the core material preform, and constrain the glass fiber bundles pre-embedded in step S203 within the glass fiber fabric. S205. The core material preform is cured by vacuum infusion resin molding process to obtain a wind turbine blade core material sample. The obtained wind turbine blade core material sample is cut into shear test pieces and fatigue test pieces.

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