A structural design method for efficiently inhibiting delamination and degumming failure of fan blades

Abstract

The application discloses a structural design method for efficiently inhibiting delamination and degumming failure of a fan blade. The fan blade structure comprises upper and lower skins, a middle core layer structure and continuous fiber bundles connecting the two side skins and the core layer. The middle core layer structure comprises discontinuous grid plates, hollow tubes and chamfers at both ends of the hollow tubes, which can increase the contact area of the skins and the core layer, increase the bonding force between the two, enhance the local buckling stability of the skin and core layer structure and reduce the delamination failure possibility of the material. The fiber bundles have a pre-tension stress and are connected to the upper and lower skins through the hollow tube structure of the core layer and form a mechanical engagement force between the skin and the core layer, thereby effectively inhibiting the degumming failure between the skin and the core layer.

Description

[0001] Areas involved

[0002] This invention belongs to the field of wind power engineering structures and relates to a structural design method for efficiently suppressing delamination and degumming failure of wind turbine blades. Background Technology

[0003] Wind power is a leading renewable energy source and an important way to achieve my country's carbon emission targets. To improve the power generation efficiency of wind turbines, the blades, as the only structural component that directly collects wind energy, have grown to over 100 meters in length. Traditional 100-meter-class large wind turbine blades are manufactured using a multi-body molding method, where the upper and lower skins and the intermediate continuous grid core layer are first formed separately through fiber layup and vacuum infusion, and then connected by structural adhesive. However, due to the ultra-high aspect ratio and significant thin-walled characteristics of the continuous grid core layer, the interfacial adhesion between the core layer structure and the skin is weak, and both are prone to large out-of-plane buckling deformation, generating additional shear stress. Therefore, the skin and core grid of traditional wind turbine blades are prone to delamination failure; and the interface between the skin and the core layer is prone to debonding failure, resulting in a blade's actual service life being far less than expected, causing huge economic losses. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a structural design method for efficiently suppressing delamination and degumming failure of wind turbine blades, which solves the delamination failure problem of the traditional blade skin and core layer, as well as the degumming failure problem between the skin and core layer.

[0005] This invention provides a structural design method for efficiently suppressing delamination and degumming failure of wind turbine blades. The wind turbine blade structure includes upper and lower skins, a middle core layer structure, and a continuous fiber bundle connecting the skin and the core layer.

[0006] Furthermore, the intermediate core layer structure consists of hollow tubes and discontinuous grid plates. The hollow tubes are connected end to end along the blade length direction through the grid plates, but are not connected along the blade width direction.

[0007] Furthermore, the diameter of the hollow tube centerline is not greater than the length of the grid plate, that is, the ratio of the hollow tube diameter to the distance between two adjacent hollow tubes is not greater than 0.5. This can ensure that the local buckling stability of the discontinuous grid plate of the skin and core layer is in the best state.

[0008] Furthermore, the hollow tube can be a hollow tube with a constant cross-section or a hollow tube with a variable cross-section.

[0009] Furthermore, the upper and lower ends of the hollow tube are connected to the upper and lower side skins through a chamfered structure, and the chamfer diameter is not less than 1.5 times the diameter of the center line of the hollow tube. This can ensure that the chamfer fully supports the panel and skin, and can also significantly reduce the stress concentration at the connection between the chamfer and the panel and skin.

[0010] Furthermore, the fiber bundle passes through the hollow tube of the core layer and is connected to the positioners at corresponding positions in the upper and lower skins.

[0011] Furthermore, the fiber bundle is continuous from the tail of the blade to the root of the blade.

[0012] Furthermore, the fiber bundle has pre-tension stress, which forms pre-compression stress on the connected core layer and skin.

[0013] Furthermore, the fiber bundle is composed of several layers of fiber cloth or fiberboard, the number of which depends on the mechanical requirements of the blade.

[0014] Furthermore, the material composition of the wind turbine blades includes, but is not limited to, a series of materials such as carbon fiber composites, glass fiber composites, and aramid fiber composites.

[0015] As described above, the structural design method of the present invention for efficiently suppressing delamination and degumming failure of wind turbine blades has the following beneficial effects:

[0016] 1) This invention can enhance the out-of-plane buckling stability of wind turbine blade skin and effectively suppress delamination failure of the horizontally laid fibers in the skin. Traditional wind turbine blade skins are supported by a thin-walled grating plate in the core layer, which makes the skin prone to out-of-plane instability deformation. The resulting out-of-plane shear force severely weakens the bonding performance between the fiber layups, leading to delamination failure. However, this invention, by setting a hollow tube in the blade core layer and its chamfered ends, significantly enhances the constraint on the out-of-plane deformation of the skin, thereby improving the local buckling stability of the skin under pressure and reducing out-of-plane deformation during instability, thus effectively suppressing delamination failure of the horizontally laid fibers in the skin.

[0017] 2) This invention can improve the out-of-plane shear buckling stability of the core layer grid of wind turbine blades and effectively suppress the delamination failure of the vertical lay-up fibers in the core layer grid. Traditional wind turbine blade core layers use continuous grids with extremely high aspect ratios, resulting in weak shear buckling stability. This invention uses discontinuous grid plates connected sequentially by thin-walled tubes, thereby reducing the aspect ratio of the grids, enhancing the boundary constraints of the discontinuous grids, improving the local shear buckling stability of the core layer grid, and reducing the out-of-plane deformation when the core layer grid becomes unstable. This effectively suppresses the delamination failure of the vertical lay-up fibers in the core layer.

[0018] 3) This invention can improve the adhesion between the core layer and the skin of wind turbine blades, effectively suppressing delamination failure. Traditional blade core layer grids are characterized by thin walls, resulting in a very limited contact area with the skin and thus weak adhesion. However, the core layer structure of this invention, through its hollow tube and chamfered ends, significantly increases the contact area with the skin, thereby improving the adhesion between the core layer and the skin interface.

[0019] 4) This invention can create a mechanical interlocking force between the core layer and the skin of the wind turbine blade, further suppressing debonding failure. Traditional wind turbine blades rely solely on adhesive bonding between the core layer and the skin. However, this invention utilizes the proposed hollow tube structure for the core layer, applying pre-compression stress between the core layer and the panel through fiber bundles passing through the hollow tube. This mechanical force can further suppress debonding failure of the wind turbine blade core layer and skin. Attached Figure Description

[0020] Figure 1 This invention provides an overall perspective view of the wind turbine blade structure and a perspective view of its core layer cross-section.

[0021] Figure 2 for Figure 1 A three-dimensional cross-sectional view of the wind turbine blade structure shown in the figure;

[0022] Figure 3 for Figure 2 A three-dimensional view of the core layer structure of the wind turbine blade shown in the figure;

[0023] Figure 4 for Figure 2 The diagram shows a plan view of the fiber bundle distribution on the wind turbine blades (side view, viewed along the direction indicated by arrow 6);

[0024] Figure 5 for Figure 2 The diagram shows the principle of skin buckling stability enhancement of the wind turbine blade structure compared to the traditional blade structure (partial plan view, side view, viewed along the direction indicated by arrow 6);

[0025] Figure 6 for Figure 2 The diagram shows the principle of core layer shear buckling stability enhancement of the wind turbine blade structure compared to the traditional blade structure (partial plan view, side view, viewed along the direction indicated by arrow 6);

[0026] Figure 7 Detailed drawing of rounded corners, with Figure 2 Taking the interface between the upper skin and the core layer as an example (partial plan view, side view, viewed in the direction indicated by arrow 6);

[0027] Figure 8 Detailed diagram of the inverted elliptical angle, with Figure 2Taking the interface between the upper skin and the core layer as an example (partial plan view, side view, viewed in the direction indicated by arrow 6);

[0028] Figure 9 for Figure 2 The diagram shows the position of the fiber bundles on the upper and lower sides of the wind turbine blade before the skin and core structure are joined together.

[0029] Figure 10 for Figure 2 The diagram shows the fiber bundle positions when the upper and lower skins and core structure of the wind turbine blade are fully joined.

[0030] Figure 11 for Figure 7 The side and bottom views of the prefabricated component with rounded corners are shown.

[0031] Explanation of reference numerals in the attached figures

[0032] 1- Upper skin of the wind turbine blade; 101- Buckling instability region of conventional wind turbine blade skin; 102- Buckling instability region of the wind turbine blade skin of the present invention; 1(i)- Embedded locator in the upper panel corresponding to the i-th hollow tube; 2- Lower skin of the wind turbine blade; 2(i+1)- Embedded locator in the lower panel corresponding to the i-th hollow tube; 3- Core structure of the wind turbine blade; 31- Hollow tube; 32- Discontinuous grating plate; 321- Buckling instability region of continuous grating plate in the core layer of conventional wind turbine blade; 322- Buckling instability region of discontinuous grating plate in the core layer of the wind turbine blade of the present invention. 33- Chamfer between core layer and upper skin; 331- Rounded corner between core layer and upper skin; 3311- Rounded corner side view; 3312- Rounded corner bottom view; 3313- Rounded corner base (for insertion into hollow tube); 332- Chamfered elliptical corner between core layer and upper skin; 34- Chamfer between core layer and lower skin; 4- Continuous fiber bundle; 5- Along the length of the fan blade, where the arrow points from the blade tip to the blade root; 6- Along the width of the fan blade, where the arrow points from the windward side to the leeward side. Detailed Implementation

[0033] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0034] It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to provide a clear understanding of the invention. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness or purpose of the invention, should still fall within the scope of the disclosed technical content. Furthermore, terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0035] Combination Figures 1 to 11 As shown, this invention provides a structural design method for efficiently suppressing delamination and degumming failure of wind turbine blades. In this embodiment, it includes upper and lower skins (1, 2), a hollow tube (31)-grid (32)-bevel (33, 34) core layer structure connected to the upper and lower skins, and prestressed fiber bundles (4) passing through the hollow tubes. Specifically:

[0036] First, the upper and lower blade skins (1, 2) are prepared by horizontal fiber layup and vacuum resin infusion. Fiber cloth positioners (1(1), 1(2), 1(3)…1(i)…1(n); 2(2), 2(4), 2(6)…2(i+1)…2(n+1); where n depends on the number of hollow tubes along the blade length direction) are pre-embedded at the skin position corresponding to each hollow tube. The positioners are square or round tubes prefabricated using fiber composite materials or metals.

[0037] Secondly, the core layer of the hollow tube (31)-grid (32) is prepared by vertical fiber layup and vacuum resin infusion. A prefabricated chamfer structure (3311, 3312) using the same fiber composite material as the skin and core layer is used. After applying structural adhesive to the bottom (3313), it is inserted into the hollow tube (31), forming adhesive bonding and mechanical interlocking between the chamfer and the hollow tube. The ratio of the hollow tube diameter to the length of the discontinuous grid plate is not greater than 1, and the ratio of the chamfer diameter to the hollow tube diameter is not less than 1.5. This ensures optimal out-of-plane buckling stability of the skin and core grid, significantly increases the bonding force at the interface between the skin and the core layer, and reduces the degree of interface stress concentration.

[0038] The third step takes the 31(i) hollow tube as an example. One end of a long fiber bundle (4) composed of several layers of fiber cloth is fixed to positioner 1(i) on the upper skin of the wind turbine blade, passes through the corresponding hollow tube (31(i)), and connects to positioner 2(i+1) on the lower skin. The fiber bundle passes through positioner 2(i+1) on the lower skin to the 31(i+1) hollow tube, then passes through the 31(i+1) hollow tube again and connects to positioner 1(i+2) on the upper skin. This process continues until the fiber bundle passes through the nth tube at the blade root and is pulled out from the blade root.

[0039] Fourth, structural adhesive is pre-applied at the corresponding positions of the upper and lower skins (1 and 2) of the blade, the core layer (including hollow tube 31, discontinuous grid 32, and chamfers 33 and 34), and the positioners (1(i); 2(i+1)). The upper and lower skins of the wind turbine blade are then joined with the core layer structure, and continuous fiber bundles (4) are tensioned while joining. After joining is completed, the skin and core layer structure are fixed, and the fiber bundles are continued to be tensioned to generate pre-tension stress inside, thereby generating pre-compression stress at the interface between the skin and the core layer.

[0040] Finally, allow sufficient time for the structural adhesive to cure and form a complete blade.

[0041] In another embodiment of the present invention, the hollow tube may have a variable cross-section.

[0042] In another embodiment of the present invention, the chamfer is a rounded corner (331) or an elliptical corner (332), and the chamfer diameter (or major axis) is adjustable within a range not less than the diameter of the hollow tube.

[0043] In another embodiment of the present invention, a series of composite materials, including but not limited to carbon fiber composite materials, glass fiber composite materials, and basalt fiber composite materials, may be used.

[0044] In another embodiment of the present invention, the diameter of the hollow tube is adjustable within a range not exceeding the length of the grid sheet.

[0045] In another embodiment of the present invention, the amount of fiber cloth or fiberboard required for the fiber bundle can be determined according to mechanical requirements.

[0046] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A structural design method for efficiently suppressing delamination and debonding failure of a fan blade, characterized by: The wind turbine blade structure includes upper and lower side skins (1, 2), a middle core structure (3), and a continuous fiber bundle (4) that connects the two side skins and the middle core structure and has pre-tension stress. The middle core structure is composed of a hollow tube (31) and a discontinuous grid plate (32). The hollow tube is connected end to end along the blade length direction (5) through the grid plate, but not along the blade width direction (6). The continuous fiber bundle passes through the hollow tube of the middle core structure and is connected to the positioner at the corresponding position in the upper and lower side skins, and forms a pre-compression stress between the connected skin and the middle core structure.

2. The structural design method for efficiently suppressing delamination and debonding failure of a fan blade according to claim 1, characterized in that: The diameter of the center line of the hollow tube (31) is not greater than the length of the grid plate (32), that is, the ratio of the diameter of the hollow tube to the distance between two adjacent hollow tubes is not greater than 0.

5.

3. The structural design method for efficiently suppressing delamination and degumming failure of wind turbine blades according to claim 1, characterized in that: The hollow tube (31) is a variable cross-section hollow tube.

4. The structural design method for efficiently suppressing delamination and degumming failure of wind turbine blades according to claim 1, characterized in that: The upper and lower ends of the hollow tube (31) are connected to the upper and lower side skins (1, 2) through chamfered structures (33, 34), and the chamfer diameter is not less than 1.5 times the diameter of the center line of the hollow tube. The chamfered structure is prefabricated using the same fiber composite material as the skin and intermediate core structure (3). After applying structural adhesive to its bottom, it is inserted into the hollow tube, forming adhesive bonding and mechanical interlocking force between the chamfer and the hollow tube.

5. The structural design method for efficiently suppressing delamination and degumming failure of wind turbine blades according to claim 1, characterized in that: The continuous fiber bundle (4) is continuous from the tail of the blade to the root of the blade. One end of the bundle is fixed to the 1(i) locator of the upper skin (1) and is alternately inserted in the order of the 31(i) hollow tube, the 2(i+1) locator of the lower skin (2), the 31(i+1) hollow tube and the 1(i+2) locator of the upper skin, and so on, until it passes through the nth hollow tube at the root of the blade and is pulled out from the root of the blade. The continuous fiber bundle is tensioned during and after the upper and lower skins and the intermediate core structure (3) are joined together.

6. The structural design method for efficiently suppressing delamination and degumming failure of wind turbine blades according to claim 1, characterized in that: The continuous fiber bundle (4) is composed of several layers of fiber cloth or fiberboard, the number of which is determined according to the mechanical requirements of the blade.

7. The structural design method for efficiently suppressing delamination and degumming failure of wind turbine blades according to claim 1, characterized in that: The material composition of the wind turbine blades includes, but is not limited to, carbon fiber composites, glass fiber composites, and aramid fiber composites.

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