Embedding element for a wind turbine blade
The present invention relates to an embedding element ( 76 ) for embedment in a shell structure of a wind turbine rotor blade ( 10 ), the element having a wedge-shaped part ( 85 ). The embedding element ( 76 ) comprises a fibre material and a binding agent, wherein the fibre material is at least partially joined together by means of the binding agent. The inventive element provides improved structural flexibility and elasticity resulting in less wrinkle formation during blade manufacturing. In other aspects, the invention relates to a method of manufacturing the embedding element ( 76 ), to a method of manufacturing a wind turbine rotor blade ( 10 ) using the embedding element ( 76 ), and to a wind turbine blade ( 10 ) obtainable by said method.
1. A root end assembly for a wind turbine rotor blade ( 10 ) comprising a plurality of embedding elements ( 76 ) embedded together with a plurality of bushings in a root region of a blade shell structure in between an outer shell part and an inner shell part, wherein each of the embedding elements is placed between a corresponding pair of adjacent bushings, such that alternating ones of the embedding elements and the bushings are arranged about a circumference of a cross-section of the root region, each of the embedding elements ( 76 ) being elongated and having a first end portion ( 77 ) and a second end portion ( 79 ), the first end portion ( 77 ) and the second end portion ( 79 ) having a uniform width, wherein the width extends perpendicular to a longitudinal axis of the embedding element ( 76 ), wherein each of the embedding elements ( 76 ) comprises a wedge-shaped part ( 85 ) which tapers in a direction towards the second end portion ( 79 ), each of the embedding elements ( 76 ) comprising a fibre material and a binding agent, wherein the fibre material is at least partially joined together by means of the binding agent, and wherein the binding agent is present in an amount of 0.1-15 wt % relative to the weight of the fibre material, the fibre material consisting of glass fibres, carbon fibres or a combination of glass and carbon fibres, the binding agent comprising a thermoplastic binding agent, wherein each of the embedding elements ( 76 ) is separately formed through a pultrusion process comprising pulling a pultrusion string formed from the fibre material and the binding agent, and cutting the pultrusion string to form the embedding element ( 76 ), and wherein each of the embedding elements ( 76 ) consists essentially of the fibre material and the binding agent,
wherein the root end assembly is formed by placing each of the embedding elements between the corresponding pair of adjacent bushings, such that the alternating ones of the embedding elements and the bushings are arranged about the circumference of the cross-section of the root region, a resin material being subsequently infused between the outer shell part and the inner shell part for fixing the embedding elements and the bushings within the blade shell structure, and
wherein the embedding element ( 76 ) has an elastic modulus of between 0.01 and 110 GPa.
2. The root end assembly for a wind turbine rotor blade according to claim 1 , wherein the binding agent is present in an amount of 0.5-5 wt % relative to the weight of the fibre material.
3. The root end assembly for a wind turbine rotor blade according to claim 2 , wherein the binding agent is present in an amount of 0.5-2.5 wt % relative to the weight of the fibre material.
4. The root end assembly for a wind turbine rotor blade according to claim 1 , wherein the melting point of the binding agent is between 40° C. and 220° C.
5. The root end assembly for a wind turbine rotor blade according to claim 4 , wherein the melting point of the binding agent is between 40° C. and 160° C.
6. The root end assembly for a wind turbine rotor blade according to claim 1 , wherein the binding agent comprises a polyester.
7. The root end assembly for a wind turbine rotor blade according to claim 6 , wherein the polyester is a bisphenolic polyester.
8. The root end assembly for a wind turbine rotor blade according to claim 1 , wherein between its two end portions the embedding element ( 76 ) is provided with a first longitudinal lateral face ( 86 ) extending concavely in a cross-sectional view perpendicular to the longitudinal axis of the embedding element ( 76 ) and provided with a second longitudinal lateral face ( 87 ) facing opposite the first lateral face ( 86 ) and extending concavely in a cross-sectional view perpendicular to the longitudinal axis of the embedding element ( 76 ).
9. The root end assembly for a wind turbine rotor blade according to claim 1 , wherein the embedding element ( 76 ) has an elastic modulus of between 0.01 and 45 GPa.