Injection repair of fatigue cracks in composite materials

Abstract

The present invention provides a system and method for repairing fatigue cracks in a multilayer composite (140). The method includes repairing a fatigue crack at a first interface between a first layer and a second layer of the multilayer composite. The method also includes repairing a fatigue crack at a second interface between a second layer and a third layer of the multilayer composite. The method further includes anchoring the second interface to the third layer of the multilayer composite to prevent fracture from the fatigue crack.

Description

Background Art

[0001] A turbine blade is a main element of a wind turbine for converting wind energy into electrical energy. A turbine blade typically consists of a suction side shell member and a pressure side shell member, which are joined together at a joint line along the leading edge and trailing edge of the blade. The joint line is generally formed by applying a suitable joint paste or compound along the joint line at a minimized joint width between the shell members.

[0002] Defects occur within the turbine blade either from the original manufacturing process or as a result of the operating conditions to which the blade is subjected. For example, fatigue crack defects within a multi-layer composite structure (such as a root bearing cylinder) in a turbine blade are very common, and these defects relax the turbine blade from its root bearing cylinder and cause it to separate from the rotor hub. Structurally, when the metal bearing cylinder at the root of the turbine blade wears, it can no longer carry the load of the rotating blade and can become relaxed. The rotating blade typically slips off the root bearing cylinder at the lowest point during the downward swing, impacts the root bearing cylinder during the upward swing, and causes an alternating cycle of tensile and compressive forces on the root bearing cylinder. As a result, a gap can develop between the blade and the root bearing cylinder. The root bearing cylinder firmly attached to the rotor hub can ultimately bend, release the blade, and cause catastrophic turbine damage.

[0003] [[ID=十三]]Existing solutions in the wind energy industry include completely discarding a wobbling blade and procuring a new replacement blade. Otherwise, a damaged blade may need to be disassembled, repair holes may need to be drilled into the damaged bearing cylinder, and the bearing cylinder may need to be treated with a bonding adhesive before being reinstalled. In that event, the internal ridges inside the damaged bearing cylinder are generally drilled out and removed, and the repair method completely depends on the strength of the newly introduced bonding adhesive.

[0004] Another common industrial solution for subsurface defects in blade laminates requires polishing the affected blade area and subsequent reapplication of the laminate material. The defect is removed by polishing / grinding the laminate layer until the defect is exposed. The laminate layer is then reapplied and ground smooth. Typically, an "over-laminate" layer is added to the repaired area for additional strength. However, this additional laminate layer extends above the planar surface of the surrounding blade area, thus disrupting the airflow across the blade and reducing aerodynamic performance. In addition, the polishing / over-laminate repair procedure requires extensive surface preparation and skill to apply the repair laminate material, followed by grinding, over-lamination, and painting, all of which are very laborious and time-consuming.

[0005] Fatigue crack defects are common in the wind power industry with respect to many different blade designs and / or types, and the transfer of load from metal to composite is a challenge. The wind turbine blade manufacturing industry is not able to satisfactorily address manufacturing defects and / or operating condition defects. In effect, wind turbine blade design and development has focused primarily on the wind turbine blade itself, rather than the root bearing cylinder. As a result, performance is affected, and wind turbine blades fail at the root bearing cylinder more frequently than they should.

[0006] Furthermore, blade defects typically require on-site repair to ensure the efficient operation of the wind turbine over its design life and power rating.

[0007] Therefore, this industry will benefit from improved repair procedures for wind turbine blades that are time-efficient, particularly suitable for on-site repairs, and result in consistent and structurally sound restorations. [Overview of the project] [Means for solving the problem]

[0008] Detailed explanation Various aspects or features of this disclosure are described with reference to the drawings, where similar reference numerals are used throughout to refer to similar elements. Numerous details are provided herein to provide a thorough understanding of this disclosure. However, it should be understood that certain aspects of this disclosure can be practiced without these specific details, or using other methods, components, materials, or equivalents. In other instances, well-known structures and devices are shown in block diagram form to facilitate the explanation of this disclosure.

[0009] Various implementations of the disclosed subject matter generally relate to apparatus, systems, and methods for the field of wind turbines, as well as methods, systems, and kits for repairing damaged root bearing cylinder wind turbine blades, and may offer improvements thereto. More specifically, the disclosed subject matter relates to a process for repairing fatigue cracks in composite laminated structures by utilizing an injection method for injecting a structural adhesive into cracked and porous composite laminates. In a non-limiting embodiment, the adhesive may be a self-etching thermoplastic adhesive useful in bonding to surfaces contaminated with leaks from oil or grease from hydraulic pitch systems. Furthermore, the thermoplastic adhesive may be heated and reheated and essentially "self-healed". In other words, if damage is found during post-repair inspection, a heat blanket may be applied, and the defective repair can be repaired again without the need to reinject new adhesive. The process also involves using the same method to inject cleaning chemicals and surface preparation chemicals to prepare several composite bonding surfaces for adhesive injection application.

[0010] In certain aspects of the subject matter disclosed, a method for repairing fatigue cracks in a multilayer composite is disclosed. The method includes repairing a fatigue crack at a first interface between a first layer and a second layer of the multilayer composite, and repairing a fatigue crack at a second interface between a second layer and a third layer of the multilayer composite. The method may also include anchoring the second interface to the third layer of the multilayer composite to prevent fracture from the fatigue crack.

[0011] A method for repairing fatigue cracks at a first interface between a first layer of a multilayer composite and a second layer of a multilayer composite may include drilling a first series of wash holes and a first series of drain holes extending from the outer surface of the composite to the first interface. The method may further include washing the first series of wash holes and a first series of drain holes with a high-pressure wash fluid and drying the first series of wash holes and a first series of drain holes with an air jet. The method may also include drilling a first series of filling holes extending from the outer surface of the composite to the first interface and arranging fluid injection ports within the first series of filling holes. The method may further include injecting crack repair fluid through the injection ports to fill the first series of filling holes and thermally curing the crack repair fluid deposited within the first series of filling holes.

[0012] Fatigue cracks at the second interface between the second and third layers of a multilayer composite can be repaired by drilling a second series of wash holes and a second series of drain holes extending from the outer surface of the composite to the second interface, washing the second series of wash holes and a second series of drain holes with a high-pressure wash fluid, and drying the second series of wash holes and a second series of drain holes with an air jet. Furthermore, a second series of filling holes may be drilled from the outer surface of the composite to the second interface, and fluid injection ports may be disposed within the second series of filling holes. The method may also include injecting a crack repair fluid through the injection ports to fill the second series of filling holes, and thermosetting the crack repair fluid deposited within the second series of filling holes. The second series of filling holes may be aligned and spaced apart from the first series of filling holes in a predetermined force transmission pattern.

[0013] Anchoring the second interface against fracture from composite fatigue cracks may include inclining some of the second series of filling holes laterally with respect to the first series of filling holes, and extending at least one of the inclined filling holes from the third layer through the second layer to the first layer.

[0014] The method may also include repairing fatigue cracks at a third interface between a third layer and a fourth layer of the multilayer composite, and anchoring the third interface to the fourth layer of the multilayer composite to prevent fracture from the fatigue cracks.

[0015] Repairing fatigue cracks at a third interface between a third layer and a fourth layer of a multilayer composite may include drilling a third series of wash holes and a third series of drain holes extending from the outer surface of the composite to the third interface, washing the third series of wash holes and a third series of drain holes with a high-pressure wash fluid, and drying the third series of wash holes and a third series of drain holes with an air jet. The method may further include drilling a third series of filling holes extending from the outer surface of the composite to the third interface, and arranging fluid injection ports within the third series of filling holes. The method may also include injecting crack repair fluid through the injection ports to fill the third series of filling holes, and thermosetting the crack repair fluid deposited within the third series of filling holes. The third series of filling holes may be aligned and spaced apart from a second series of filling holes in a predetermined force transmission pattern.

[0016] Anchoring a third interface against fracture from composite fatigue cracks may include inclining some of the third series of filling holes laterally with respect to the second series of filling holes, and extending at least one of the inclined third series of filling holes from the fourth layer through the third layer to the second layer.

[0017] In certain aspects of the subject matter disclosed, a wind turbine blade with a repaired root bearing cylinder is disclosed. The wind turbine blade may include a blade body with pressure and suction sides joined at the leading and trailing edges. The blade body may extend longitudinally from the root region to the tip region through a transition region, the transition region extending between the root region and the tip region. The blade body may be mechanically connected to the rotor hub through several root bearing cylinders disposed within the root region. The repaired root bearing cylinder may include a multilayer composite with a fatigue crack repaired at a first interface between a first layer of the multilayer composite and a second layer of the multilayer composite. Other fatigue cracks may be present that are repaired at a second interface between a second layer of the multilayer composite and a third layer of the multilayer composite. The second interface is anchored to the third layer of the multilayer composite.

[0018] During operation, fatigue cracks at the first interface between the first and second layers of the multilayer composite can be repaired by drilling a series of wash holes from the outer surface of the composite of the root bearing cylinder to the first interface. The wash holes can first be washed with a high-pressure wash fluid and then dried with an air jet. In addition, a series of drainage holes can be drilled from the outer surface of the composite to the first interface. Like the wash holes, the drainage holes can be washed with a high-pressure wash fluid and then dried with an air jet. In addition, a series of filling holes can be drilled from the outer surface of the composite to the first interface, and fluid injection ports can be provided within the filling holes. Crack repair adhesive fluid can be injected through the injection ports and deposited in the first series of filling holes. After being deposited in the first series of filling holes, the crack repair adhesive fluid can be thermocured.

[0019] In a similar structure, fatigue cracks at the second interface between the second and third layers of a multilayer composite can be repaired by drilling a second series of wash holes from the outer surface of the composite of the root bearing cylinder to the second interface. The second series of wash holes can first be washed with a high-pressure wash fluid and then dried with an air jet. A second series of drainage holes can be drilled from the outer surface of the composite to the second interface. Like the second series of wash holes, the second series of drainage holes can be washed with a high-pressure wash fluid and then dried with an air jet. In addition, a second series of filling holes can be drilled from the outer surface of the composite to the second interface, and fluid injection ports can be provided within the filling holes. Crack repair adhesive fluid can be injected through the injection ports and deposited within the second series of filling holes. After being deposited within the second series of filling holes, the crack repair adhesive fluid can be thermocured.

[0020] A second series of filling holes can be arranged and spaced apart from a first series of filling holes in a predetermined force transmission pattern. Furthermore, some of the second series of filling holes can be tilted laterally with respect to the first series of filling holes, extending from the third layer through the second layer to the first layer, and the second interface can be anchored to the third layer of the multilayer composite.

[0021] The wind turbine blade may contain more fatigue cracks that are repaired at the third interface between the third and fourth layers of the multilayer composite. The third interface may be anchored to the fourth layer of the multilayer composite.

[0022] In a similar structure, fatigue cracks repaired at the third interface between the third and fourth layers of a multilayer composite can be repaired by drilling a third series of wash holes from the outer surface of the composite of the root bearing cylinder to the third interface. The third series of wash holes can first be washed with a high-pressure wash fluid and then dried with an air jet. Furthermore, a third series of drainage holes can be drilled from the outer surface of the composite to the third interface. Like the third series of wash holes, the third series of drainage holes can be washed with a high-pressure wash fluid and dried with an air jet. In addition, a third series of filling holes can be drilled from the outer surface of the composite to the third interface, and fluid injection ports can be provided within the filling holes. Crack repair fluid can be injected through the injection ports and deposited within the third series of filling holes. After being deposited within the third series of filling holes, the crack repair fluid can be thermoset.

[0023] A third series of filling holes can be arranged and spaced apart from a second series of filling holes in a predetermined force transmission pattern. Furthermore, some of the third series of filling holes can be tilted laterally with respect to the second series of filling holes, extending from the fourth layer through the third layer to the second layer, and the third interface can be anchored to the fourth layer of the multilayer composite.

[0024] In one aspect of the subject matter disclosed, a repair kit for repairing a damaged root bearing cylinder within a wind turbine blade is disclosed. The repair kit may include a drilling template configured and arranged to advance around a multilayer composite. The drilling template may define drilling locations for a series of wash holes, drainage holes, and filling holes within the multilayer composite. The repair kit may also include a certain amount of crack repair fluid, which is suitable for repairing cracks within the multilayer composite, and an injector device configured and arranged to inject the crack repair fluid through the filling holes. [Brief explanation of the drawing]

[0025] The accompanying drawings, which are included to provide a further understanding of the disclosed subject matter, are incorporated in and constitute a part of this specification. The drawings also illustrate implementations of the disclosed subject matter and, together with the detailed description, explain the principles of the disclosed subject matter. No attempt is made to show structural details in more detail than may be necessary for a fundamental understanding of the disclosed subject matter and the various ways in which it may be practiced.

[0026] [Figure 1] FIG. 1 is an illustrative perspective view of a conventional wind turbine.

[0027] [Figure 2] FIG. 2 is an illustrative cross-sectional view of a damaged wind turbine rotor blade root bearing cylinder according to an embodiment of the present disclosure.

[0028] [Figure 3] FIG. 3 is an illustrative process overview of defect formation within a wind turbine rotor blade root bearing cylinder according to an embodiment of the present disclosure.

[0029] [Figure 4] FIG. 4 is an illustrative process overview of repairing a damaged wind turbine rotor blade root bearing cylinder according to an embodiment of the present disclosure.

[0030] [Figure 5] FIG. 5 is an illustrative cross-sectional view of a repaired wind turbine rotor blade root bearing cylinder according to an embodiment of the present disclosure.

[0031] [Figure 6] FIG. 6 is an illustrative process flow diagram of an injection repair of a composite fatigue crack according to an embodiment of the present disclosure.

[0032] [Figure 7] FIG. 7 is an illustrative defect summary in a cross-sectional view of a damaged wind turbine rotor blade root bearing cylinder according to an embodiment of the present disclosure.

[0033] [Figure 8A] Figure 8A is an illustrative top view of repairing a damaged wind turbine rotor blade root bearing cylinder according to one embodiment of the present disclosure.

[0034] [Figure 8B] Figure 8B is an illustrative front view of repairing a damaged wind turbine rotor blade root bearing cylinder according to one embodiment of the present disclosure, corresponding to the top view of Figure 8A.

[0035] [Figure 9] Figure 9 is an illustrative diagram of a perforation template according to one embodiment of the present disclosure.

[0036] [Figure 10A] Figure 10A is an illustrative top view of a Type C repair of a damaged wind turbine rotor blade root bearing cylinder according to one embodiment of the present disclosure.

[0037] [Figure 10B] Figure 10B is an illustrative front view of a Type C repair of a damaged wind turbine rotor blade root bearing cylinder, corresponding to the top view of Figure 10A, according to one embodiment of the present disclosure.

[0038] [Figure 11] Figure 11 shows an illustrative method for repairing a root bearing cylinder located within the root region of a wind turbine blade.

[0039] [Figure 12] Figure 12 illustrates an illustrative method for repairing fatigue cracks at the first interface between the first and second layers of a multilayer composite.

[0040] [Figure 13] Figure 13 illustrates an illustrative method for repairing fatigue cracks at the first interface between the first and second layers of a multilayer composite.

[0041] [Figure 14] Figure 14 illustrates an illustrative method for repairing fatigue cracks at the first interface between the first and second layers of a multilayer composite.

[0042] [Figure 15] Figure 15 is an illustrative diagram of a root bearing cylinder repair kit for damaged wind turbine blades. [Modes for carrying out the invention]

[0043] Figure 1 is an illustrative perspective view 100 of a conventional wind turbine 100. As shown, the wind turbine 100 may include a tower 112 with a nacelle 114 mounted thereon. The wind turbine 100 may also include a rotatable hub 118 (also referred to as a “rotor hub”) with several rotor blades 116 mounted thereon, which are connected to a main flange that pivots a main rotor shaft (not shown). The wind turbine power generation and control components are typically housed within the nacelle 114. The diagram in Figure 1 is provided for illustrative purposes only to place this disclosure in an exemplary field of use. It should be understood that this disclosure is not limited to any particular type of wind turbine configuration.

[0044] The wind turbine blade 116 typically includes a blade body 120 with pressure sides 122 and suction sides 124 that join at the leading edge 126 and trailing edge 128. The blade body 120 extends longitudinally through a transition region 136 from the root region 132 to the tip region 134, with the transition 136 extending between the root region 132 and the tip region 134. The blade body 120 is mechanically connected to the rotor hub 118 through several root bearing cylinders (described in more detail in relation to Figure 2-15 below) disposed within the root region 132 of the wind turbine blade 116. The root bearing cylinders can typically be fabricated from a multilayer composite structure. The multilayer composite structure may allow fatigue cracks to appear at several interfaces between some of the layers of the multilayer composite structure, and timely and on-the-fly repair of fatigue cracks can improve the life and operational efficiency of the wind turbine blade 116.

[0045] Figure 2 is an illustrative cross-sectional view of a damaged wind turbine rotor blade root bearing cylinder 140 according to one embodiment of the present disclosure. Referring to Figure 2, the root bearing cylinder 140 may include a pressure plate 142 used to mechanically connect the root bearing cylinder to the rotor hub 118 (Figure 1) using an exemplary end-threaded rod 144. The root bearing cylinder 140 may also include an outer bearing cylinder laminate 146, an inner bearing cylinder laminate 148, a bearing cylinder tail 152 with an inwardly chamfered core, and a bearing cylinder body 154. Oil deposits 156 may be found in the outer bearing cylinder laminate 146 or the inner bearing cylinder laminate 148, or in the space between the two laminates, or in the space between the inner bearing cylinder laminate 148 and the bearing cylinder body 154, due to fatigue wear and oil leakage that may be present in the hydraulic system of the wind turbine blade assembly. As is generally known, some wind turbines use a hydraulic system to pitch their blades, while others use an electric pitch system. The majority of affected blades have a hydraulic pitch system, and the hydraulic fluid in such a system tends to leak. As a result, the root bearing cylinder is coated with a deposit of leaked hydraulic fluid 156.

[0046] Figure 3 is an illustrative process overview 160 of defect formation within an exemplary root bearing cylinder 140 (Figure 2) according to one embodiment of the present disclosure. Due to sustained fatigue from the intermittent movement of the blade, several stressed areas 162 may exist within the outer bearing cylinder laminate 146 or the inner bearing cylinder laminate 148, or in the space between the two laminates, or in the space between the inner bearing cylinder laminate 148 and the bearing cylinder body 154. For example, when the blade is in the 6 o'clock position 164, the weight of the blade may exert a tensile force 166 on the root bearing cylinder 140, as shown in the enlarged view 168. Furthermore, when the blade is in the 12 o'clock position 172, the weight of the blade may exert a compressive force 174 on the root bearing cylinder 140, as shown in the enlarged view 176. Over time, accumulated oil 178 and wear may lead to failure at several bearing cylinder / fiber interfaces, as shown in the enlarged view 182.

[0047] Figure 4 is an illustrative process outline 190 for repairing a damaged wind turbine rotor blade root bearing cylinder according to one embodiment of the present disclosure. Referring to Figure 4, the accumulated oil and contaminants 192 can lead to damage at the connection from the bearing cylinder to the fiber, as shown in enlarged figure 194. The accumulated oil and contaminants 192 can be removed using a washing method with a specific cleaning solution, as shown in enlarged figure 198 196. Subsequently, an adhesive repair material can be injected into the cleaned area to repair and reinforce the damaged spot within the root bearing cylinder 140, as shown in enlarged figure 204 202.

[0048] Figure 5 is an illustrative cross-sectional view of a restored wind turbine rotor blade root bearing cylinder 210 according to one embodiment of the present disclosure. As shown in Figure 2, the root bearing cylinder 210 may include a pressure plate 142, a rod with end threads 144, an outer bearing cylinder laminate 146, an inner bearing cylinder laminate 148, a bearing cylinder tail 152 with a chamfered core, and a bearing cylinder body 154. The oil deposit 156 in Figure 2 has been drained and replaced with a clean adhesive deposit 212.

[0049] Figure 6 is an illustrative process flow diagram 220 for injection repair of composite fatigue cracks according to one embodiment of the present disclosure. The present disclosure provides a method for repairing fatigue cracks in a multilayer composite after defect detection and inspection, as in 222. Typically, depending on the type of defect, there may be three types of repairs, illustratively referred to as “Type A” as in 224, “Type B” as in 226, and “Type C” as in 228. The repaired wind turbine blade at the end of the Type A repair process 224, and / or Type B repair process 226, and / or Type C repair process 228 may be inspected and made operational as in 232.

[0050] To further elaborate, an exemplary Type A repair process 224 may be performed at a first interface between a first layer (typically a metal bearing cylinder) and a second layer (typically a glass wrapper) of the root bearing cylinder 140. Fatigue cracks may occur in several fracture areas localized to the first interface. Fatigue cracks at the first interface between the first and second layers of the root bearing cylinder 140 may be repaired by mapping and drilling a series of flush holes (also referred to as "Type A flush holes") from the outer surface of the root bearing cylinder 140 to the first interface, as shown in 234. The series of flush holes may first be flushed with a high-pressure flushing fluid and then dried with an air jet, as shown in 236. A series of fill holes (also referred to as "Type A fill holes") may be drilled from the outer surface of the root bearing cylinder 140 to the first interface, as shown in 236, and fluid injection ports may be provided within the fill holes, as shown in 242. Crack repair adhesive fluid may be injected through the injection ports and deposited within the fill holes, as shown in 244. After being deposited within the fill holes, the crack repair adhesive fluid may be thermocured, as shown in 246. In effect, the repair at the first interface transitions the fracture area from the first interface to the second interface.

[0051] Fatigue cracks may also occur in several other areas of failure, localized to the second interface between the second layer (glass wrapping) and the third layer (typically the pultruded body) of the root bearing cylinder 140. Fatigue cracks at the second interface can be repaired using a crack repair adhesive fluid. Repair at the second interface reinforces the second interface and anchors it to the third layer of the root bearing cylinder 140 to prevent failure from the fatigue cracks.

[0052] Referring back to Figure 6, an exemplary Type B repair 226 at the second interface may be performed by mapping and drilling a second series of flush holes (also referred to as "Type B flush holes") and a second series of fill holes extending from the outer surface of the root bearing cylinder composite to the second interface, as shown in 248. As in a Type A repair, the second series of flush holes and fill holes may be flushed with a high-pressure flushing fluid and subsequently dried with an air jet. Fluid injection ports may be provided within the fill holes, as shown in 252. Crack repair adhesive fluid may be injected through the injection ports and deposited within the second series of fill holes, as shown in 254. After the crack repair adhesive fluid has been deposited within the second series of fill holes, it may be thermo-cured, as shown in 256. The injection ports may then be withdrawn, as shown in 258, after the adhesive has cured.

[0053] Referring again to Figure 6, an exemplary Type C repair 228 may be performed with respect to a fatigue crack at a third interface between the third and fourth layers (typically glass laminates) of the root bearing cylinder 140. A third series of flush holes (also referred to as "Type C flush holes") and a third series of fill holes extending from the outer surface of the composite of the root bearing cylinder to the third interface may be mapped and drilled, as shown in 262. As in Type A and Type B repairs, the third series of flush holes and fill holes may be flushed with a high-pressure flushing fluid and subsequently dried with an air jet. Fluid injection ports may be provided within the fill holes, as shown in 264. Crack repair fluid may be injected through the injection ports and deposited within the third series of fill holes, as shown in 266. After being deposited within the third series of fill holes, the crack repair fluid may be thermocured, as shown in 268. The injection port can then be withdrawn, as shown in 272, after the adhesive has cured.

[0054] Figure 7 is an illustrative defect summary shown in a cross-sectional view 280 of a damaged wind turbine rotor blade root bearing cylinder 140 (Figure 2) according to one embodiment of the present disclosure. These figures represent root / tip and tip / root cross-sections. An exemplary type A repair 282, initially performed at the interface between the metal bearing cylinder 284 and the glass wrapper 286, may be crucial for restoring about 80% of the original strength. An exemplary type B repair 288 may then be performed at the interface between the glass wrapper 286 and the drawn body 292. The type B repair 288 may be constructed on top of the type A repair 282 such that a second series of filling holes (described in the context of Figure 6) are aligned and spaced apart from the first series of filling holes (Figure 6) in a predetermined force transmission pattern, allowing the first composite fatigue crack failure area to transition from the first interface to the second interface. Furthermore, some of the second series of filling holes are inclined laterally with respect to the first series of filling holes, extending from the third layer through the second layer to the first layer, and the second interface can be anchored to the third layer of the multilayer composite.

[0055] An exemplary Type C repair 294 may be a third and final repair performed at the interface between the pultruded body 292 and the glass laminate 296. The Type C repair 294 may be constructed on Type A repairs 282 and Type B repairs 292 such that a third series of fill holes (Figure 6) are arranged and spaced apart from a second series of fill holes (Figure 6) in a predetermined force transmission pattern, allowing a second composite fatigue crack failure area to transition from the second interface to the third interface. Furthermore, some of the third series of fill holes may be inclined laterally with respect to the second series of fill holes, extending from the fourth layer through the third layer to the second layer, allowing the third interface to be anchored to the fourth layer of the multilayer composite.

[0056] Figure 8A is an illustrative top view 300 of repairing a damaged wind turbine rotor blade root bearing cylinder 140 (Figure 2) according to one embodiment of the present disclosure. Figure 8B is an illustrative front view of repairing a damaged wind turbine rotor blade root bearing cylinder 140 (Figure 2), corresponding to the top view of Figure 8A. In general, the present disclosure provides a method for repairing fatigue cracks in a multilayer composite such as a root bearing cylinder 140. Referring back to Figure 8B, a first interface (282 in Figure 7) exists between a first layer (284 in Figure 7) and a second layer (286 in Figure 7) of the multilayer composite (280 in Figure 7). Fatigue cracks may occur in several fracture areas localized to the first interface 282. Fatigue cracks at the first interface 282 can be repaired using a crack repair adhesive fluid.

[0057] Furthermore, a second interface (Figure 7, 288) may exist between the second layer (Figure 7, 286) and the third layer (Figure 7, 292) of the multilayer composite (Figure 7, 280). Fatigue cracks may occur in several fracture regions localized to the second interface (Figure 7, 288). Fatigue cracks at the second interface (Figure 7, 288) can be repaired using a crack repair adhesive fluid. In effect, repair at the first interface (Figure 7, 282) transitions the fracture region from the first interface (Figure 7, 282) to the second interface (Figure 7, 288). Furthermore, repair at the second interface (Figure 7, 288) can reinforce the second interface and anchor it to the third layer (Figure 7, 296) of the multilayer composite, preventing failure from fatigue cracks.

[0058] Referring back to Figure 8A, the root bearing cylinder can be inspected by non-destructive testing / torque testing methods, and defective bearing cylinders can be identified. Once defective bearing cylinders are identified, exemplary drainage holes 302 (for Type A repair) and 312 (for Type B repair), drainage holes 304 (for Type A repair) and 314 (for Type B repair), and filling holes 306 (for Type A repair) and 316 (for Type B repair) can be mapped and drilled using a pre-designed and optionally 3D-printed drilling guide (also referred to as a “drill template” as described in detail in the context of Figure 9), which uses itself as a reference point away from the root bearing cylinder body. This ensures that the drilled holes are fabricated in appropriate locations corresponding to the spots most likely to be defective and the centers of localized damage areas. The drilling template can slide across the root bearing cylinder body and laminate and can help map the spots where the drainage holes, drainage holes, and filling holes can be drilled. The drilling template can also guide the drilling of holes perpendicular to the bearing cylinder body. Once the holes are mapped and drilled, an exemplary Zerk fitting 318 (Figure 8B) can be positioned within the drilled holes. The drilling bit used may typically be of an appropriate size for the Zerk fitting 318.

[0059] Exemplary perforations 302, 304, 306, 312, 314, 316, and equivalents may be flushed with a modified high-pressure washer and clean fluid until the exiting fluid appears clean. Optionally, compressed air may also be used to blow away any residual clean fluid from any cavities. The cleaning and flushing process may typically begin at the tip end of the wind turbine blade and proceed along the root end of the wind turbine blade, as there may be solid laminations behind the tip end that block the exit of the clean and flushing fluid.

[0060] As previously stated, the root bearing cylinder may be coated with leaked hydraulic fluid, and a cleaning fluid such as mineral spirits may need to be applied to clear the leaked hydraulic fluid. In effect, the cleaning fluid can treat the surface to which it is applied and prepare a chemically active surface. Operationally, wash holes and drain holes may be drilled after drilling, near cracks and microcracks, and the wash holes and drain holes may be washed with the cleaning fluid. The cleaning fluid is usually volatile and not easily flammable. Any remaining residual cleaning fluid may evaporate and disappear. In some embodiments, compressed air may be blown to facilitate the evaporation of any remaining cleaning fluid.

[0061] The scrubbing and drainage holes are typically scrubbed using a high-pressure scrubbing fluid, usually with a high-pressure washer, so that precisely oriented tips are inserted into the scrubbing and drainage holes. As the scrubbing process progresses, the contaminated waste solution exits through the drainage holes, and scrubbing continues until the solution is cleaner. Subsequently, the scrubbing and drainage holes are dried using compressed air jets precisely oriented into the individual holes. The scrubbing and drainage holes are then allowed to settle for a period of time to allow all cavities to dry completely from the scrubbing solution.

[0062] Optionally, a vacuum pump may be used on the root side to draw in flushing and cleaning fluid through it. The vacuum generated by the vacuum pump can effectively boil away any residual cleaning agents remaining in the cavity and completely dry the cavity. However, the vacuum has a limited pressure value of 14.7 psi, below the Zerk fitting pressure of several thousand psi. Vacuum suction is likely to be most effective when a complete seal is possible. Furthermore, if the repair is carried out under the tower, the drilled holes may be drilled in different directions along the bearing cylinder. Other alternative methods for generating flushing and cleaning pressure may also exist, such as using gas under pressure. In addition, threaded nozzles may be used for flushing, for cleaning after flushing, and for cleaning after the rotor blade bolts have been removed.

[0063] Referring back to Figures 8A and 8B, the washed and cleaned holes 302, 304, 306, 312, 314, and 316 can be filled with a structural adhesive applied from the tip side of the wind turbine blade to the root side of the wind turbine blade. In effect, the structural adhesive bonds the root bearing cylinder to the corresponding roving, as will be described in more detail below.

[0064] At times, it may be advantageous to repair the blade at its load-neutral position, either 3 o'clock or 9 o'clock, which provides a favorable load distribution. Typically, non-destructive testing and inspection methods may be performed before and after repair to assess the degree and condition of porosity and to determine how to adjust repair efforts for a better effect.

[0065] During operation, structural adhesives (also referred to as “adhesives”) may be injected into cracked laminates to repair wind turbine blade root bearing cylinders. In non-limiting embodiments, adhesives used in various implementations of the disclosed subject may be commercially available methyl methacrylate (MMA) 8120. This adhesive is self-etching, compatible with fatigue conditions, and effective on both metals and composites. MMA 8120 has low viscosity and does not need to be diluted to reach pressure-induced laminate cracks and microcracks. In addition to MMA 8120, other polymers such as epoxy, polyester, vinyl esters, polyurethane, and general urethanes may also be used to treat and repair composite fatigue cracks. Furthermore, other polymer compounds typically used in structural concrete repair may also be used to treat and repair composite fatigue cracks.

[0066] Structurally, it is more effective to distribute the weight load of the suspension blade with the internal ridges in place, rather than relying entirely on the shear strength of the adhesive or resin, whether or not they are in the commonly known 6 o'clock or 12 o'clock positions. The operation is safe, simple, and not complicated. Holes can be drilled into the damaged laminate, and adhesive can be injected into the holes. In this way, the damaged laminate can be restored to its original condition, if not better, by reintroducing mechanical connections that may have worn down over time. This is accomplished not by relying solely on the shear strength of the adhesive and resin, but rather by reinforcing the shear strength by distributing tensile and compressive loads across the ridges within the root bearing cylinder.

[0067] In Type B repairs (described in more detail below), offset filling holes are drilled to repair defects between the glass and the drawn molded body, and flushing may not be possible because cracks and microcracks may be too small for any clean fluid to access. Type C repairs (described in more detail below) may be performed for much smaller cavities, and the same structural methods may be used. However, the materials may need to be changed, and resin may be used instead of adhesive.

[0068] Figure 9 illustrates a drilling template 320 used to drill exemplary type A and type B wash holes, drain holes, and fill holes in Figures 8A and 8B, according to one embodiment of the present disclosure. Once a defective bearing cylinder is identified, wash holes can be mapped and drilled using a drilling template 320 that is referenced away from the body of the root bearing cylinder 140 (Figure 2). This ensures that the drilled holes are made in appropriate locations corresponding to the spots most likely to be defective and the centers of localized failure areas. The drilling template 320 may be configured and arranged to travel around the root bearing cylinder 140 and define drilling locations for wash holes, drain holes, and fill holes corresponding to centers of localized stress that could lead to fatigue concentration and eventual failure of the root bearing cylinder 140. The drilling template 320 may slide across the body of the root bearing cylinder and the laminate, helping to map spots to be drilled. The drilling template 320 can also guide the drilling of holes perpendicular to the bearing cylinder body. Once the holes are mapped and drilled, the Zerk fitting can be positioned within the filled holes. The drilling bit used can typically be of an appropriate size for the Zerk fitting.

[0069] Length 322 of the first series of holes on the exemplary first root bearing cylinder, length 324 of the second series of holes on the exemplary first root bearing cylinder, length 326 of the first series of holes on the exemplary second root bearing cylinder, length 328 of the second series of holes on the exemplary second root bearing cylinder (i.e., the longer of the two planar dimensions), total length of the template (i.e., the longer of the two planar dimensions) 332, total width of the template (i.e., the shorter of the two planar dimensions) 334, furthest hole from the baseline The pre-configured dimensions 320 of the drilling template, such as the distance 336 from the baseline to the exemplary intermediate hole 338, the distance 342 from the baseline to the nearest hole 342, the distance 344 between two rows of holes corresponding to two different bearing cylinders, the distance 346 between two rows of holes corresponding to one exemplary bearing cylinder, the distance 348 from the side line to the first row of holes 348, the distance 352 from the side line to the second row of holes 352, and equivalents, can be optimized by trial and error and / or parameterized in terms of the original dimensions of the bearing cylinder. The drilling pattern, the distance between filling holes, and the adhesive injection mechanism affect the performance and effectiveness of the repair. In the exemplary setting, four holes are drilled 80 mm apart.

[0070] Figure 10A is an illustrative top view 380 of an exemplary Type C repair of a damaged wind turbine rotor blade root bearing cylinder according to one embodiment of the present disclosure. Figure 10B is an illustrative front view of a Type C repair of a damaged wind turbine rotor blade root bearing cylinder, corresponding to the top view of Figure 10A. Referring to Figure 10B, a third interface (294 in Figure 7) may exist between a third layer of the multilayer composite (292 in Figure 7) and a fourth layer of the multilayer composite (296 in Figure 7). Fatigue cracks may occur in several fracture areas localized to the third interface 294. Fatigue cracks at the third interface 294 can be repaired using a crack repair fluid. A third series of flush holes (also referred to as “Type C flush holes”) 382 may be marked and drilled so that the flush holes 382 extend from the outer surface of the composite to the third interface. A third series of drainage holes 384 can be marked and drilled so that the drainage holes 384 extend from the outer surface of the composite to the third interface.

[0071] Referring back to Figures 11A and 11B, the root bearing cylinders can be inspected by non-destructive testing / torque testing methods, and defective bearing cylinders can be identified. Once defective bearing cylinders are identified, exemplary wash holes 382 (for Type C repair), drain holes 384 (for Type C repair), and filling holes 386 (for Type C repair) can be pre-designed and optionally mapped and drilled using a 3D printed drilling template 320 (Figure 9). Wash holes 382 and drain holes 384 can be washed with a high-pressure wash fluid. Subsequently, wash holes 382 and drain holes 384 can be dried using air jets and allowed to settle over a time period.

[0072] The filling holes 386 may be marked and drilled so that they extend from the outer surface of the composite to the third interface. Fluid injection ports may be provided within the third series of filling holes 386. Crack repair fluid (structural adhesive) may be injected through the injection ports until the filling holes 386 are completely filled with the crack repair fluid. The crack repair fluid deposited within the third series of filling holes may be thermally cured over a predetermined time period.

[0073] In effect, repair at the third and final interface 294 can reinforce the third interface 294, anchor it to the fourth layer (glass laminate) 296, and prevent failure from fatigue cracks. Specifically, some of the third series of filling holes can be deployed in a direction inclined laterally to the third interface, such that the inclined filling holes extend from the fourth layer to the third layer as anchoring supports. The perforations and filling holes 386 extending through the pultruded body into the metal bearing cylinder can structurally function as anchoring rods reinforcing the third interface. The adhesive material is dispensed into a grease gun using a glue gun.

[0074] Figure 11 shows an illustrative method 400 for repairing a root bearing cylinder 140 (Figure 2) located within the root region of a wind turbine blade. The root bearing cylinder 140 may typically include a multilayer composite with a fatigue crack repaired at a first interface between a first and second layer of the multilayer composite, as shown in 402. Other fatigue cracks may also be present, repaired at a second interface between a second and third layer of the multilayer composite, as shown in 404. The repair effectively transitions the composite fatigue crack failure area from the first interface to the second interface, which is then anchored to the third layer of the multilayer composite, as shown in 406.

[0075] Figure 12 shows an illustrative method 420 for repairing a fatigue crack at a first interface between a first and second layer of an exemplary root bearing cylinder 140 (Figure 2). The fatigue crack at the first interface can be repaired by drilling a series of wash holes, drain holes, and fill holes from the outer surface of the composite to the first interface, as shown in 422. The wash holes and drain holes may first be washed with a high-pressure wash fluid, as shown in 424, and then dried with an air jet, as shown in 426. Furthermore, fluid injection ports may be provided within the fill holes, as shown in 428. Crack repair fluid may be injected through the injection ports and deposited in the fill holes, as shown in 432. After being deposited in the fill holes, the crack repair fluid may be thermocured, as shown in 434.

[0076] Figure 13 shows an illustrative method 460 for repairing a fatigue crack at the second interface between the third and second layers of an exemplary root bearing cylinder 140 (Figure 2). The fatigue crack at the second interface can be repaired by drilling a second series of wash holes, drain holes, and fill holes from the outer surface of the composite to the second interface, as shown in 462. The second series of wash holes and drain holes may first be washed with a high-pressure wash fluid, as shown in 464, and then dried with an air jet, as shown in 466. Furthermore, fluid injection ports may be provided within the second series of fill holes, as shown in 468. Crack repair fluid may be injected through the injection ports and deposited within the second series of fill holes, as shown in 472. After being deposited within the second series of fill holes, the crack repair fluid may be thermocured, as shown in 474.

[0077] A second series of filling holes is arranged and spaced apart from the first series of filling holes in a predetermined force transmission pattern, allowing the fatigue crack failure region of the first composite to transition from the first interface to the second interface. Furthermore, some of the second series of filling holes are inclined laterally with respect to the first series of filling holes, extending from the third layer through the second layer to the first layer, and can be anchored at the second interface to the third layer of the multilayer composite.

[0078] Wind turbine blades may contain more fatigue cracks that are repaired at a third interface between the third and fourth layers of the multilayer composite. This repair transitions the composite fatigue crack failure region from the second interface to the third interface, which is then anchored to the fourth layer of the multilayer composite.

[0079] Figure 14 shows an illustrative method 480 for repairing a fatigue crack at the third interface between the third and fourth layers of an exemplary root bearing cylinder 140 (Figure 2). The fatigue crack at the third interface can be repaired by drilling a third series of wash holes, drain holes, and fill holes from the outer surface of the composite to the first interface, as shown in 482. The third series of wash holes and drain holes may first be washed with a high-pressure wash fluid, as shown in 484, and then dried with an air jet, as shown in 486. Furthermore, fluid injection ports may be provided within the third series of fill holes, as shown in 488. Crack repair fluid may be injected through the injection ports and deposited within the third series of fill holes, as shown in 492. After being deposited within the third series of fill holes, the crack repair fluid may be thermocured, as shown in 494.

[0080] A third series of filling holes is arranged and spaced apart from a second series of filling holes in a predetermined force transmission pattern, allowing the fatigue crack failure region of the second composite to transition from the second interface to the third interface. Furthermore, some of the third series of filling holes are inclined laterally with respect to the second series of filling holes, extending from the fourth layer through the third layer to the second layer, allowing the third interface to be anchored to the fourth layer of the multilayer composite.

[0081] Figure 15 is an illustrative diagram 500 of a root bearing cylinder repair kit 502 for a damaged wind turbine blade. The repair kit 502 may include a drilling template 504 configured and arranged to progress around a multilayer composite. The drilling template 504 may define drilling locations for a series of wash holes, drain holes, and filling holes within the multilayer composite. The repair kit 502 may also include a wash gun 506 suitable for washing the wash holes and drain holes, and an air dryer 508 for drying the wash holes and drain holes. The air dryer 508 may provide a directed supply of dry compressed air applied to the cracked cavity through a mechanical nozzle that focuses air into the cavity, forcing the evaporation of solvents, clean fluids, and any contaminants that may affect the bonding ability in subsequent bonding steps.

[0082] The repair kit 502 may also include a crack repair fluid 512 in an amount suitable for repairing cracks in a multilayer composite, and an injector device 514 configured and arranged to inject the crack repair fluid through a filling hole. The crack repair fluid 512 may be a self-etching adhesive that also provides a chemical bond that may be stronger than the original design, while allowing surface preparation of the composite. The injector device 514 may be a drilling device designed to produce injection bore holes that fit to specified dimensions without tearing the composite laminate, and to ensure that the holes are positioned at specified angles and pitches relative to the blade surface. The kit 502 may optionally include an instruction manual 516 that describes the operation and handling of the kit to the intended user of the kit 502.

[0083] However, the repair method described above is not limited to wind turbine blade root bearing cylinders and can generally be applied to fatigue / laminate crack repair in any composite. The adhesive can be injected under pressure and / or in a predetermined volume to repair the cracked laminate and restore the laminate to its nominal strength. The adhesive may be self-etching and acidic, so that it bakes the surface to which it is applied, improving surface adhesion. Firstly, several pores are prepared, and a surfactant is injected into the pores as a dispersant to flush out any contaminants remaining in any cavities. Furthermore, the adhesive may be heated for rebonding. In some embodiments, a resin may be used instead of the adhesive to reconnect the laminate layers. A predetermined level of pressure may be applied to allow the adhesive to find its pathway into the cracks and microcracks in the laminate and restore the manufacturing defect.

[0084] The above description includes numerous specific details, such as resource partitioning / sharing / replication implementations, types and interrelationships of system components, and logical partitioning / integration options, to provide a more thorough understanding. However, embodiments disclosed herein may be practiced without such specific details. In other cases, control structures, logical implementations, opcodes, means for defining operands, and complete software instruction sequences are not shown in detail, as those skilled in the art will be able to implement those described without excessive experimentation using the included description.

[0085] In this specification, references such as "one implementation," "an implementation," and "an example implementation" indicate that the implementation described may include certain features, structures, or characteristics, but not all implementations necessarily include those specific features, structures, or characteristics. Furthermore, such phrases do not necessarily refer to the same implementation. In addition, when certain features, structures, and / or characteristics are described in relation to an implementation, a person skilled in the art will understand that this may affect such features, structures, and / or characteristics in relation to other implementations, whether explicitly stated or not.

[0086] For example, a diagram (one or more) illustrating a flow diagram sometimes refers to a diagram (one or more) illustrating a block diagram, and vice versa. Alternative implementations discussed with reference to a diagram (one or more) illustrating a block diagram, whether explicitly stated or not, also apply to implementations discussed with reference to a diagram (one or more) illustrating a flow diagram, and vice versa. At the same time, the scope of this explanation includes implementations other than those discussed with reference to block diagrams for the purpose of implementing flow diagrams, and vice versa.

[0087] The detailed description and claims may use the term “coupled” in conjunction with its derivatives. “Coupled” is used to indicate two or more elements that may or may not be in direct physical or electrical contact with each other, cooperate with each other, or interact with each other.

[0088] The flowchart in the figure illustrates a specific sequence of operations performed by a particular implementation, but such an order is illustrative and not limiting (for example, alternative implementations may perform operations in a different order, combine operations, perform operations in parallel, or overlap operations so that they are partially parallel).

[0089] While the above description includes several illustrative implementations, the present invention is not limited to the implementations described and can be practiced with modifications and alternative forms in the spirit and scope of the appended claims. This description is therefore illustrative and not restrictive.

Claims

1. A method for repairing fatigue cracks in a multilayer composite, wherein the method is To repair fatigue cracks at the first interface between the first layer of the multilayer composite and the second layer of the multilayer composite, To repair fatigue cracks at the second interface between the second layer and the third layer of the multilayer composite, The second interface is anchored to the third layer of the multilayer composite to prevent failure due to fatigue cracks. Methods that include...

2. Repairing fatigue cracks at the first interface between the first layer and the second layer of the multilayer composite is To drill a first series of wash holes extending from the outer surface of the composite to the first interface, Drilling a first series of drainage holes extending from the outer surface of the composite to the first interface, The first series of wash holes and the first series of drain holes are washed using a high-pressure washing fluid, The first series of wash holes and the first series of drain holes are dried using air jets, Drilling a first series of filling holes extending from the outer surface of the composite to the first interface, The first series of filling holes is provided with a fluid injection port, Injecting crack repair fluid through the injection port to fill the first series of filling holes, The crack repair fluid deposited in the first series of filling holes is to be thermally cured. The method according to claim 1, including the method described in claim 1.

3. Repairing fatigue cracks at the second interface between the second layer and the third layer of the multilayer composite is To drill a second series of wash holes extending from the outer surface of the composite to the second interface, Drilling a second series of drainage holes extending from the outer surface of the composite to the second interface, The second series of wash holes and the second series of drain holes are washed using a high-pressure washing fluid, Drying the second series of wash holes and the second series of drain holes using air jets, Drilling a second series of filling holes extending from the outer surface of the composite to the second interface, The fluid injection port is provided within the second series of filling holes, Injecting crack repair fluid through the injection port to fill the second series of filling holes, The crack repair fluid deposited in the second series of filling holes is to be thermally cured. The method according to claim 2, including the method described in claim 2.

4. The method according to claim 3, further comprising arranging and spacing a second series of filling holes relative to a first series of filling holes in a predetermined force transmission pattern.

5. Anchoring the second interface against failure from composite fatigue cracks is At least one of the second series of filling holes is inclined laterally with respect to the first series of filling holes, Extending at least one of the inclined holes in the second series of filling holes from the third layer through the second layer to the first layer The method according to claim 3, including the method described in claim 3.

6. To repair fatigue cracks at the third interface between the third layer and the fourth layer of the multilayer composite, The third interface is anchored to the fourth layer of the multilayer composite to prevent failure due to fatigue cracks. The method according to claim 1, further comprising:

7. Repairing the fatigue crack at the third interface between the third layer and the fourth layer of the multilayer composite is To drill a third series of wash holes extending from the outer surface of the composite to the third interface, Drilling a third series of drainage holes extending from the outer surface of the composite to the third interface, The third series of wash holes and the third series of drain holes are washed using a high-pressure washing fluid, The third series of wash holes and the third series of drain holes are dried using air jets, Drilling a third series of filling holes extending from the outer surface of the composite to the third interface, The fluid injection port is provided within the third series of filling holes, The crack repair fluid is injected through the injection port to fill the third series of filling holes, The crack repair fluid deposited in the third series of filling holes is to be thermally cured. The method according to claim 6, including the method described in claim 6.

8. The method according to claim 7, further comprising arranging and spacing the third series of filling holes relative to the second series of filling holes in a predetermined force transmission pattern.

9. Anchoring the third interface against failure from composite fatigue cracks is At least one of the third series of filling holes is inclined laterally with respect to the second series of filling holes, Extending at least one of the third series of filling holes that is inclined from the fourth layer through the third layer to the second layer The method according to claim 7, including the method described in claim 7.

10. These are wind turbine blades, The blade body comprises a pressure side and a suction side joined at the leading edge and trailing edge, the blade body extends longitudinally from the root region to the tip region through a transition region, and the transition region extends between the root region and the tip region. The blade body is mechanically connected to the rotor hub through a repaired root bearing cylinder disposed within the root region, and the repaired root bearing cylinder comprises a multilayer composite. The aforementioned multilayer composite is A first plurality of fatigue cracks that are repaired at the first interface between the first layer of the multilayer composite and the second layer of the multilayer composite, A second plurality of fatigue cracks are repaired at the second interface between the second layer of the multilayer composite and the third layer of the multilayer composite. Includes, The second interface is anchored to the third layer of the multilayer composite, and is a wind turbine blade.

11. The first plurality of fatigue cracks that are repaired at the first interface between the first layer and the second layer of the multilayer composite are A first series of wash holes drilled from the outer surface of the composite to the first interface, wherein the first series of wash holes are washed with a high-pressure wash fluid and dried with an air jet, A first series of drainage holes drilled from the outer surface of the composite to the first interface, wherein the first series of drainage holes are washed with a high-pressure washing fluid and dried with an air jet, A first series of filling holes drilled from the outer surface of the composite to the first interface, A plurality of fluid injection ports are disposed within the first series of filling holes, A crack repair fluid is injected through the injection port and deposited in the first series of filling holes, wherein the crack repair fluid is thermally cured after being deposited in the first series of filling holes. A wind turbine blade according to claim 10, comprising the features described above.

12. The second plurality of fatigue cracks that are repaired at the second interface between the second layer and the third layer of the multilayer composite are A second series of wash holes drilled from the outer surface of the composite to the second interface, wherein the second series of wash holes are washed with a high-pressure wash fluid and dried with an air jet, A second series of drainage holes drilled from the outer surface of the composite to the second interface, wherein the second series of drainage holes are washed with a high-pressure washing fluid and dried with an air jet, A second series of filling holes drilled from the outer surface of the composite to the second interface, A plurality of fluid injection ports are disposed within the second series of filling holes, A crack repair fluid is injected through the injection port and deposited in the second series of filling holes, wherein the crack repair fluid is thermally cured after being deposited in the second series of filling holes. A wind turbine blade according to claim 10, comprising the features described above.

13. The wind turbine blade according to claim 12, wherein the second series of filling holes are arranged and spaced apart from the first series of filling holes in a predetermined force transmission pattern.

14. The wind turbine blade according to claim 12, wherein at least one of the second series of filling holes is inclined laterally with respect to the first series of filling holes, extends from the third layer through the second layer to the first layer, and anchors the second interface to the third layer of the multilayer composite.

15. The wind turbine blade according to claim 10, further comprising a third plurality of fatigue cracks repaired at a third interface between the third layer of the multilayer composite and the fourth layer of the multilayer composite, wherein the third interface is anchored to the fourth layer of the multilayer composite.

16. The third plurality of fatigue cracks that are repaired at the third interface between the third layer and the fourth layer of the multilayer composite are A third series of wash holes drilled from the outer surface of the composite to the third interface, wherein the third series of wash holes are washed with a high-pressure wash fluid and dried with an air jet, A third series of drainage holes drilled from the outer surface of the composite to the third interface, wherein the third series of drainage holes are washed with a high-pressure washing fluid and dried with an air jet, A third series of filling holes drilled from the outer surface of the composite to the third interface, A third set of fluid injection ports are disposed within the third series of filling holes, A crack repair fluid injected through the injection port and deposited in the third series of filling holes, wherein the crack repair fluid is thermally cured after being deposited in the third series of filling holes. The wind turbine blade according to claim 15, comprising:

17. The wind turbine blade according to claim 16, wherein the third series of filling holes are arranged and spaced apart from the second series of filling holes in a predetermined force transmission pattern.

18. The wind turbine blade according to claim 16, wherein at least one of the third series of filling holes is inclined laterally with respect to the second series of filling holes, extends from the fourth layer through the third layer to the second layer, and anchors the third interface to the fourth layer of the multilayer composite.

19. It's a kit, A perforation template configured and arranged to advance around a multilayer composite, wherein the perforation template defines perforation locations for a plurality of wash holes, drainage holes, and filling holes within the multilayer composite, A certain amount of crack repair fluid suitable for repairing cracks in the multilayer composite, An injector device and an injector device configured and arranged to inject the crack repair fluid through the filling hole. A kit that includes the following:

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