Methods of manufacturing an impregnated metal insert

Abstract

Method of manufacturing an impregnated metal insert for a wind turbine blade root, the insert comprising an outer surface and an open end adapted to receive a fastening element for attachment to a wind turbine rotor hub, wherein the method comprises covering the insert outer surface with one or more resin pre impregnated fiber layers, and heating for curing such that a resin impregnated fiber layer adheres to the outer surface of the insert. The disclosure is further related to the method of manufacturing a portion of a wind turbine blade.

Claims

1. A method of manufacturing a portion of a wind turbine blade, the method comprising: providing one or more fiber layers in a mold for forming the blade portion, forming a plurality of pre impregnated metal inserts by providing a metal insert comprising an outer surface and an open end adapted to receive a fastener for attachment to a wind turbine rotor hub, covering the outer surface of the metal insert with one or more resin pre impregnated fiber layers, and heating for curing such that at least one of the resin pre impregnated fiber layers adheres to the outer surface of the metal insert, arranging the plurality of pre impregnated metal inserts on top of the fiber layers at a blade root portion of the mold; wherein the pre impregnated metal inserts are heated for curing prior to being arranged on top of the fiber layers at the blade root portion of the mold; providing further fiber layers on top of the pre impregnated metal inserts, infusing a resin into the mold, and curing the resin such that the pre impregnated metal inserts are joined to the fiber layers.

2. The method of claim 1, wherein the resin impregnated fiber layer adhered to the outer surface of the pre impregnated metal insert has a thickness in the range of 1 cm to less than 3 cm.

3. The method of claim 1, wherein the step of forming a plurality of pre impregnated metal inserts further comprises heating the metal insert by application of electricity to the metal insert to facilitate curing.

4. The method of claim 1, wherein the pre impregnated metal insert further comprises a closed end opposite to the open end, Wherein the closed end is straight.

5. The method of claim 4, wherein the pre impregnated metal insert is cylindrical.

6. A method of manufacturing a wind turbine blade, the wind turbine blade comprising a blade root portion for coupling to a hub or extender of a wind turbine, the method comprising: providing one or more fiber layers in a mold for forming the blade portion, forming a plurality of pre impregnated metal inserts by providing a metal insert comprising an outer surface and an open end adapted to receive a fastener for attachment to a wind turbine rotor hub, covering the outer surface of the metal insert with one or more resin pre impregnated fiber layers, and heating for curing such that at least one of the resin pre impregnated fiber layers adheres to the outer surface of the metal insert, arranging the plurality of pre impregnated metal inserts on top of the fiber layers at a blade root portion of the mold; wherein the pre impregnated metal inserts are heated for curing prior to being arranged on top of the fiber layers at the blade root portion of the mold; providing further fiber layers on top of the pre impregnated metal inserts, infusing a resin into the mold, and curing the resin such that the pre impregnated metal inserts are joined to the fiber layers, wherein the pre impregnated metal inserts are embedded in the blade root portion in a direction parallel to that of a longitudinal axis of the blade.

7. A method of manufacturing a portion of a wind turbine blade, the method comprising: providing one or more fiber layers in a mold for forming the blade portion, forming a plurality of pre impregnated metal inserts by providing a metal insert comprising an outer surface and an open end adapted to receive a fastener for attachment to a wind turbine rotor hub, covering the outer surface of the metal insert with one or more resin pre impregnated fiber layers, and heating, for curing such that at least one of the resin pre impregnated fiber layers adheres to the outer surface of the metal insert, arranging the plurality of pre impregnated metal inserts on top of the fiber layers at a blade root portion of the mold; providing further fiber layers on top of the pre impregnated metal inserts, infusing a resin into the mold, curing the resin such that the pre impregnated metal inserts are joined to the fiber layers; and wherein the step of forming a plurality of pre impregnated metal inserts further comprises covering the resin pre impregnated fiber layers with a peel ply layer before heating for curing, and removing the peel ply layer after heating for curing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Particular embodiments of the present invention will be described in the following by way of non-limiting examples, with reference to the appended drawings, in which:

(2) FIG. 1 shows a cross-sectional view of the attachment of a wind turbine blade root portion to a pitch bearing of the wind turbine according to an embodiment;

(3) FIGS. 2a, 3a and 4a show cross-sectional views of an impregnated metal insert according to different embodiments;

(4) FIGS. 2b, 3b, and 4c show cross-sectional views of the inserts of FIGS. 2a, 2b and 2c respectively embedded into a blade root portion of a wind turbine blade;

(5) FIG. 5 shows a schematic cross-section of a mould for moulding a blade portion;

(6) FIG. 6 shows a top view of a wind turbine blade comprising any of the inserts of FIG. 2a, 3a or 4a; and

(7) FIG. 7 shows a perspective view of an exemplary wind turbine.

DETAILED DESCRIPTION OF EMBODIMENTS

(8) FIG. 1 shows a cross-sectional view of the attachment of a blade 503 to a pitch bearing 10 for attachment to a hub 502 of the wind turbine 500 (FIG. 7). The blade 503 may comprise a blade root portion 20 for coupling to a hub 502 of the wind turbine 500 through the outer ring 11 of the pitch bearing 10. In alternative embodiments, it may be coupled to the inner ring. The blade root may comprise a plurality of holes 21 provided with an internal insert 30. As will be explained for example in connection with FIG. 5, the blade root portion 20 may be made using an infusion technique and the inserts 30 may comprise an outer surface 31 covered by a prepreg layer 32. A mounting flange 22 may further be provided along a periphery of a mounting surface 23 of the blade root. The mounting flange 12 may be provided with holes 24 that may be aligned with an open end 33 of the inserts 30 embedded in the blade root portion 20. This enables insertion of fasteners 40 for securing the blade 503 to the hub 502.

(9) FIGS. 2a, 3a and 4a show cross-sectional views of an impregnated metal insert according to different embodiments. The same reference numbers will be used for matching parts.

(10) The metal insert 30 may comprise a metal core 35 adapted to receive a fastener through an open end 33. The metal core 35 may further comprise an outer surface 31 covered with a prepreg layer 32 i.e. a resin pre impregnated fibre layer may be provided on the outer surface 31 of the metal core 35. The prepreg layer 32 may further be covered with a peel ply layer 42 before the insert core with the resin pre impregnated fibre layer may be cured to consolidate and become an integral composite structure. After curing, the outer surface 31 may be substantially smooth when the peel ply layer 42 is removed, and a closed end 34 of the insert 30, opposite to the open end 33, may the straight shaped. It is thus rather easy to machine.

(11) In alternative embodiments, the closed end may have other shapes. In the examples of FIGS. 3a and 4a the closed ends 34 and 34 may be wedge-shaped. In particular, the closed end 34 of FIG. 3a is arrowhead shaped and the closed end 34 of FIG. 4a has a gradually reducing cross-section to a substantially pointed end 341. These shapes enhance adhesion properties.

(12) Depending on circumstances, in some embodiments, the outer surface may comprise roughness or may be serrated in order to further improve adhesion properties.

(13) FIGS. 2b, 3b and 4b show cross-sectional views of the inserts 30 of FIGS. 2a, 3a and 4a respectively embedded into a blade root portion 20 of a wind turbine blade.

(14) FIG. 5 shows a cross-sectional view of a mould 100 that may be used e.g. for infusing a blade shell or a blade root portion of a wind turbine blade using any known infusion technique.

(15) Any known infusion technique may comprise resin transfer moulding (RTM), vacuum assisted resin transfer moulding (VARTM) or RTM light, Seeman's composite resin infusion moulding process (SCRIMP) and resin film infusion among others. The general principle of infusion techniques is to suck a resin into the reinforcing fibres and fabrics using a vacuum. The vacuum is used to reduce the pressure at one end of the fabric stack thus allowing atmospheric pressure to force the resin through the fibres.

(16) In FIG. 5 some of the stages of the method of manufacturing a portion of a wind turbine blade have been depicted. In a first stage, a plurality of fibre layers 200 may be distributed on an inner surface 101 of the mould 100. In a second stage, a plurality of pre impregnated inserts 300 may be equidistantly arranged on top of the fibre layers 200 at a blade root portion. And in a third stage further fibre layers 201 may be distributed in between the inserts 300. These further fibre layers 201 may be provided until the inserts 300 are completely covered. In alternative methods, the further layers 201 may be distributed continually on top of the previous fibre layers 200 and on top of the inserts 300.

(17) The method of manufacturing a portion of a wind turbine blade may further comprise the stages of introducing a resin in the mould using an infusion technique i.e. covering the stack of fibre layers with a vacuum bag and sucking the resin inside the mould and curing the resin. This way, the pre impregnated inserts are joined together with the fibre layers but with improved mechanical properties with respect to adhesion of the metal inserts because the metal inserts were previously very well adhered to a resin impregnated fibre layer.

(18) The portion of a wind turbine blade provided in accordance with these methods may be e.g. a blade half, a substantially cylindrical blade root, or a semi-cylindrical half blade root.

(19) FIG. 6 shows a top view of a wind turbine blade comprising any of the inserts of FIG. 2a, 3a or 4a. FIG. 6 shows the blade root mounting surface 23. An enlarged view of the area enclosed by the dashed lines of FIG. 6 shows that each hole 21 of the blade root may be fitted with a metal insert. Each insert may comprise a metal core 35 adapted to receive a fastener for attachment to the hub of a wind turbine through its open end 33. The metal core 35 may comprise an outer surface that may be fully bonded to a prepreg layer 32 substantially as hereinbefore described.

(20) Although only a number of particular embodiments and examples of the invention have been disclosed herein, it will be understood by those skilled in the art that other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof are possible. Furthermore, the present invention covers all possible combinations of the particular embodiments described. Thus, the scope of the present invention should not be limited by particular embodiments, but should be determined only by a fair reading of the claims that follow.