Wind turbine blades

1. A method of making a wind turbine blade, the method comprising:

providing a plurality of strips, each strip made by a pultrusion process comprising:

drawing fibres and resin through a pultrusion die in a process direction to form a pultruded strip; and

applying a resin-free, infusion-promoting layer to a surface of the pultruded strip down-stream from the die in the process direction,

placing the plurality of strips in a wind turbine blade mould tool to form a stack having at least one infusion-promoting layer between two pultruded strips, wherein each infusion-promoting layer remains substantially resin-free when the plurality of strips is placed in the wind turbine blade mould tool;

infusing resin into the wind turbine blade mould tool such that the resin infiltrates around the stack and between the pultruded strips via each infusion-promoting layer; and

curing the resin to form the wind turbine blade.

2. The method of claim 1 , comprising bonding the infusion-promoting layer to the surface of the pultruded strip.

3. The method of claim 2 , comprising applying the infusion-promoting layer to the surface of the pultruded strip when the pultruded strip is in an uncured or semi-cured state, and curing the pultruded strip to bond the infusion-promoting layer to the surface of the pultruded strip.

4. The method of claim 1 , comprising curing the pultruded strip before applying the infusion-promoting layer to the surface of the pultruded strip.

5. The method of claim 4 , comprising applying an adhesive layer to the surface of the pultruded strip after curing the pultruded strip and before applying the infusion-promoting layer.

6. The method of claim 5 , comprising spraying the adhesive layer onto the surface of the pultruded strip.

7. The method of claim 1 , wherein the infusion-promoting layer is a fibrous layer.

8. The method of claim 7 , wherein the infusion-promoting layer is a glass fabric layer.

9. The method of claim 7 , wherein the infusion-promoting layer has a fibre density of between approximately 100 grams per square metre and 300 grams per square metre.

10. The method of claim 1 , comprising applying the infusion-promoting layer to an upper surface or a lower surface of the pultruded strip.

11. The method of claim 1 , wherein the applying a resin-free, infusion-promoting layer to a surface of the pultruded strip includes applying a first, resin-free, infusion-promoting layer to an upper surface of the pultruded strip down-stream from the die in the process direction, and applying a second, resin-free, infusion-promoting layer to a lower surface of the pultruded strip down-stream from the die in the process direction.

12. The method of claim 1 , wherein the pultruded strip has a length of between approximately 2 metres and approximately 1000 metres.

13. The method of claim 12 , wherein the pultruded strip has a length of between approximately 10 metres and approximately 150 metres.

14. The method of claim 13 , wherein the pultruded strip has a length of between approximately 10 metres and approximately 80 metres.

15. The method of claim 1 , wherein the pultruded strip is substantially flat and has a substantially rectangular cross-section.

16. A method of making a wind turbine blade, the method comprising:

providing a plurality of strips, each strip made by a process comprising:

drawing fibres and resin through a pultrusion die in a process direction to form a pultruded strip; and

applying a resin-free, infusion-promoting layer to a surface of the pultruded strip down-stream from the die in the process direction,

placing the plurality of strips in a mould tool to form a stack having at least one infusion-promoting layer between two pultruded strips, wherein each infusion-promoting layer remains substantially resin-free when the plurality of strips is placed in the mould tool;

infusing resin into the mould tool such that resin infiltrates between the pultruded strips via each infusion-promoting layer;

curing the resin in the stack of the plurality of strips;

placing the cured stack in a wind turbine blade mould tool;

infusing resin into the wind turbine blade mould tool such that the resin infiltrates around the stack; and

curing the resin to form the wind turbine blade.