Pultruded strips
A pultruded strip ( 50 ) of reinforcing material for stacking with one or more similar strips ( 50 ) to form a spar cap for a wind turbine blade is disclosed. The pultruded strip comprises a core ( 56 ) comprising fibres ( 58 ) disposed in a resin matrix ( 60 ) and a sacrificial layer ( 52 ) at least partially covering one or more surfaces of the core ( 56 ). The sacrificial layer ( 52 ) is a resin layer defining an adherend surface ( 62 A) of the strip. A pultrusion process for making such a strip ( 50 ) comprises drawing resin-coated reinforcing fibres ( 58 ) through a pultrusion die ( 80 ) in a process direction to form a core ( 56 ) of the strip ( 50 ) and applying further resin ( 53 ) to one or more surfaces of the core ( 56 ) to form a sacrificial resin layer ( 52 ) defining an adherend surface ( 62 A) of the strip ( 50 ).
1. A pultrusion process for making a pultruded strip suitable for stacking with one or more similar strips to form a spar cap for a wind turbine blade, the process comprising:
drawing resin-coated reinforcing fibres through a pultrusion die in a process direction to form a core of the strip;
applying further resin to one or more surfaces of the core to form a sacrificial resin layer defining an adherend surface of the strip; and
removing resin from the sacrificial layer through a surface treatment process to activate the adherend surface.
2. The pultrusion process of claim 1 , further comprising at least partially curing the resin in the core of the strip before applying the further resin.
3. The pultrusion process of claim 1 , comprising applying the further resin downstream of the pultrusion die in the process direction.
4. The pultrusion process of claim 1 , wherein the method comprises drawing the core with the applied further resin through a further pultrusion die to form the strip into a final cross-sectional shape.
5. The pultrusion process of claim 1 , further comprising shaping the core of the strip in a first portion of the die and shaping the core and sacrificial layer in a second portion of the die, wherein the method comprises applying the further resin to the core within the die between the first and second portions of the die.
6. A pultruded strip of reinforcing material for stacking with one or more similar strips to form a spar cap for a wind turbine blade, the pultruded strip comprising:
a core comprising fibres disposed in a resin matrix; and
a sacrificial layer at least partially covering one or more surfaces of the core, wherein the sacrificial layer is a resin layer defining an adherend surface of the strip; and
wherein the sacrificial layer has an activated adherend surface formed by using a surface treatment process to remove resin from the sacrificial layer.
7. The pultruded strip of claim 6 , wherein the sacrificial layer is substantially devoid of fibres.
8. The pultruded strip of claim 6 , wherein the sacrificial layer has a thickness in the range of 0.1 mm to 2 mm.
9. The pultruded strip of claim 6 , wherein the sacrificial resin layer comprises a resin that is different to the resin in the core.
10. The pultruded strip of claim 6 , wherein the sacrificial layer is provided on mutually opposed first and second surfaces of the core.
11. A spar cap for a wind turbine blade, the spar cap comprising a stack of pultruded strips integrated together, wherein each strip is a pultruded strip as claimed in claim 6 .
12. The spar cap of claim 11 , wherein an adherend surface of each strip is bonded to an adherend surface of an adjacent strip in the stack by adhesive such as cured resin.
13. A wind turbine blade comprising the spar cap claim 12 .
14. The pultrusion process of claim 1 , wherein the surface treatment process includes at least one of an abrasion process, a blasting treatment process, or an energetic surface treatment process.
15. The pultrusion process of claim 1 , wherein the one or more surfaces to which the resin is applied extend an entire width of the strip.
16. The pultrusion process of claim 15 , wherein the one or more surfaces that extend the entire width of the strip are planar surfaces.