Method of producing a continuous fibre reinforcement layer from individual fibre mats

Abstract

A method of producing a single assembled longitudinally extending fibre layer for use in a later resin infusion process for manufacturing a fibre-reinforced composite structure is described including steps: a) providing a first fibre mat comprising unidirectional reinforcement fibres oriented in a longitudinal direction of the first fibre mat, b) providing a second fibre mat comprising unidirectional reinforcement fibres oriented in a longitudinal direction of the second fibre mat, c) arranging the first fibre mat and the second fibre mat so that unidirectional fibres of one end of the first fibre mat adjoin one end of the second fibre mat in a single plane at a common boundary, and d) splicing unidirectional fibres of the first fibre mat at one end of the first fibre mat to unidirectional fibres of the second fibre mat at one end of the second fibre mat in order to form a splicing joint.

Claims

1. A method of manufacturing a wind turbine blade part producing a single assembled longitudinally extending fibre layer for use in a later resin infusion process, the method comprising the following steps: a) providing a first fibre mat comprising unidirectional reinforcement fibres oriented in a longitudinal direction of the first fibre mat between two ends; b) providing a second fibre mat comprising unidirectional reinforcement fibres oriented in a longitudinal direction of the second fibre mat between two ends; c) arranging the first fibre mat and the second fibre mat so that unidirectional fibres of one end of the first fibre mat adjoin one end of the second fibre mat in a single plane at a common boundary; and d) splicing unidirectional fibres of the first fibre mat at said one end of the first fibre mat to unidirectional fibres of the second fibre mat at said one end of the second fibre mat in order to form a splicing joint, the first fibre mat and the second fibre mat forming a spliced mat, the spliced mat consisting of a single layer of longitudinally extending fibres.

2. The method according to claim 1, wherein said one end of the first fibre layer and said one end of the second fibre layer are cut taperingly, and wherein said fibre layers in step c) are arranged so that the common boundary forms a tapering transition between unidirectional fibres of the first fibre mat and unidirectional fibres of the second fibre mat in the longitudinal direction of the single continuous, longitudinally extending fibre layer.

3. The method according to claim 2, wherein the tapering transition has a thickness-to-length ratio between 1:50 and 1:5.

4. The method according to claim 1, wherein step d) comprises the use of an adhesive for providing said splicing.

5. The method according to claim 4, wherein the adhesive is powder based.

6. The method according to claim 1, wherein the splicing joint is heated.

7. The method according to claim 1, wherein step d) comprises the step of stitching the first fibre mat and the second fibre mat together for providing said splicing.

8. The method according to claim 1, wherein further unidirectional fibres of the first fibre mat are pressed against unidirectional fibres of the second fibre mat in order to form a frictional connection between said unidirectional fibres.

9. The method according to claim 1, wherein step d) comprises the use of rollers for pressing the unidirectional fibres of the first mat and the second fibre mat against each other.

10. The method according to claim 1, wherein unidirectional fibres at said one ends of the first fibre mat and the second fibre mat are unstitched at a longitudinal zone at said one ends prior to step d).

11. The method according to claim 1, wherein unidirectional fibres at said one ends of the first fibre mat and the second fibre mat are aligned in the longitudinal direction via alignment means.

12. A method of manufacturing a wind turbine blade part, comprising the steps of: laying up fibre layers in a mould, wherein at least one of the fibre layers is produced according to the method of claim 1; supplying a resin to said fibre layers; and forming the fibre layers into a composite structure.

13. The method of manufacturing a wind turbine blade part according to claim 12, wherein the layup of the fibre layers involves stacking a plurality of the fibre layers, and wherein said at least one fibre layer is sandwiched between two fibre layers which do not have a splicing joint at the splicing joint of said at least one fibre layer.

14. The method of manufacturing a wind turbine blade part according to claim 12, wherein the wind turbine blade part is a load carrying structure.

15. The method of manufacturing a wind turbine blade part according to claim 12, wherein the step of forming the fibre layers into the composite structure comprises formation selected from the group consisting of hardening and curing.

16. The method of manufacturing a wind turbine blade part according to claim 12, wherein the wind turbine blade part comprises a blade shell part.

17. The method according to claim 3, wherein the thickness-to-length ratio is approximately 1:30.

18. The method according to claim 6, wherein the splicing joint is ironed.

19. The method according to claim 11, wherein the alignment means comprise a comb.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in detail below with reference to an embodiment shown in the drawings, in which

(2) FIG. 1 shows a wind turbine,

(3) FIG. 2 is a schematic perspective view of a wind turbine blade according to the invention,

(4) FIG. 3 is a schematic perspective view showing the fibre layers of a main laminate,

(5) FIG. 4 is a schematic longitudinal view of fibre layers of the main laminate,

(6) FIG. 5 is a schematic side view of an assembled fibre layer according to the invention,

(7) FIG. 6 is a schematic top view of a first assembled fibre layer according to the invention,

(8) FIG. 7 is a schematic top view of a second assembled fibre layer according to the invention,

(9) FIG. 8 is a schematic top view of a third assembled fibre layer according to the invention,

(10) FIG. 9 is a schematic top view of a fourth assembled fibre layer according to the invention,

(11) FIG. 10 is a schematic top view of a fifth assembled fibre layer according to the invention,

(12) FIG. 11 is a schematic top view of a sixth assembled fibre layer according to the invention,

(13) FIG. 12 is a schematic side view of a seventh assembled fibre layer according to the invention,

(14) FIG. 13 is a flow chart showing an example of steps for producing an assembled fibre layer according to the invention,

(15) FIG. 14 shows a schematic view of rollers for use in the invention, and

(16) FIG. 15 shows a schematic side view of the rollers.

DETAILED DESCRIPTION OF THE INVENTION

(17) FIG. 1 illustrates a conventional modern upwind wind turbine according to the so-called Danish concept with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub 8 and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 farthest from the hub 8. The rotor has a radius denoted R.

(18) FIG. 2 shows a schematic view of a first embodiment of a wind turbine blade 10 according to the invention. The wind turbine blade 10 has the shape of a conventional wind turbine blade and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 farthest away from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub, and a trailing edge 20 facing the opposite direction of the leading edge 18.

(19) The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 may be constant along the entire root area 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.

(20) A shoulder 40 of the blade 10 is defined as the position, where the blade 10 has its largest chord length. The shoulder 40 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

(21) It should be noted that the chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.

(22) The blade is typically made from a pressure side shell part 36 and a suction side shell part 38 that are glued to each other along bond lines at the leading edge 18 and the trailing edge of the blade 20.

(23) In the following, the invention is explained with respect to the manufacture of the pressure side shell part 36 or suction side shell part 38.

(24) As shown in FIG. 3, the suction side shell part 38 comprises a spar cap or main laminate 50, which extends in the longitudinal direction of the suction side shell part substantially along the entire length of the suction side shell part 38. The main laminate 50 comprises a plurality of fibre layers or mats 52 comprising unidirectional fibres (UD fibres), typically more than twenty fibre layers. The fibre mats are typically applied from a roll in dry form and are cut to the desired length. The fibre layup is then later vacuum bagged and infused with a resin, which is finally cured in order to form a composite structure. Many of the glass fibre reinforced blades utilise H-glass. While ply joints comprising ply drops are allowed for E-glass, such ply joints are not allowed for H-glass. This in effect means that if the fibre mat roll ends at a length that is shorter than the main laminate, this end piece will have to be discarded and a new roll is started. As an example, if an H-glass roll ends at 25 metres from the root for a 47.6 metre blade, the 25 metres of H-glass will have to be scrapped. The resulting waste of excess fibre-reinforcement material is significant.

(25) The present invention as shown in FIG. 4 solves this problem by producing assembled fibre layer 52, which comprises at least a first fibre mat 54 and a second fibre mat 55, where the UD fibres are spliced at ends of the two fibre mats 54, 55 so as to form an assembled fibre layer 52. The two fibre mats 54, 55 are arranged in a single plane such that the assembled layer 52 forms a single layer without ply drops. This provides a stronger laminate layer in a final composite structure than conventional laminate layers that are manufactured via two or more non-spliced fibre mats prior to the infusion process. Further, it is possible to reduce the number of wrinkles in the laminate, which will decrease mechanical weaknesses in the final composite structure even further. This is particularly achieved since the splicing joint ensures that the two mats do not move during a layup procedure, e.g. when additional fibre layers are arranged on top of the assembled fibre layers, or when the fibre reinforcement material is later vacuum bagged and infused. As seen from FIG. 4, the assembled fibre layer 52 or at least the assembly region is sandwiched between two continuous fibre layers 52, which do not have a splicing at the splicing region of the assembled fibre layer 52.

(26) According to a preferred embodiment shown in FIG. 5, the UD fibres of the first fibre mat 54 and the UD fibres of the second fibre mat 55 are cut taperingly such that the UD fibres of the two fibre mats 54, 55 adjoin each other at a common boundary 56, which forms a tapering transition between the UD fibres of the two mats 54, 55. The UD fibres of the two fibre mats are spliced to each other via a preliminary connection, such as via an adhesive, stitching, or a frictional connection. The assembled fibre layer 52 is overall provided in dry form, i.e. non-impregnated, and it is important that the splicing or preliminary connection does not impair a later resin infusion process. Accordingly, the preliminary connection is only established so as to ensure that the UD fibres do not wrinkle and that the two fibre mats 54, 55 do not move during the layup or the later vacuum bagging and infusion process. In order to provide a relative long common boundary 56 and a smooth transition between the UD fibres of the two fibre mats 54, 55, the thickness to length ratio is between 1:50 and 1:5, advantageously around 1:30.

(27) FIG. 6 illustrates a top view of a first embodiment of an assembled layer 52 according to the invention. The UD fibres are cut orthogonal to the longitudinal direction of the assembled layer 52, and the ends are cut taperingly so that a tapering transition between the UD fibres of the two mats 54, 55 are formed in the longitudinal direction of the assembled layer.

(28) FIG. 7 illustrates a top view of a second embodiment of an assembled layer according to the invention, where UD fibres of a first fibre mat 154 are spliced with UD fibres of a second fibre mat 155. The UD fibres are cut so that the end face is angled compared to the transverse direction of the assembled fibre mat. The angle may for instance be approximately 10 degrees to the transverse direction or equivalently 80 degrees to the longitudinal direction. The ends are further cut so that a tapering transition between the UD fibres of the two mats 154, 155 are formed in the longitudinal direction of the assembled fibre layer.

(29) FIG. 8 illustrates a top view of a third embodiment of an assembled layer according to the invention, where UD fibres of a first fibre mat 254 are spliced with UD fibres of a second fibre mat 255. The UD fibres are cut so that the ends face in the transverse direction forming a zigzag pattern. The ends are further cut so that a tapering transition between the UD fibres of the two mats 254, 255 is formed in the longitudinal direction of the assembled fibre layer.

(30) It should be mentioned that it is possible to combine the various embodiments for the cutting angle. It is for instance possible to provide a combination of the embodiments shown in FIGS. 7 and 8 by having a zigzag pattern along an inclined angle. Such an embodiment may distribute any possible small variations over a longer longitudinal distance of the fibre mats.

(31) FIG. 9 illustrates a top view of a fourth embodiment of an assembled layer according to the invention, where UD fibres of a first fibre mat 354 are spliced with UD fibres of a second fibre mat 355. The UD fibres of the first fibre mat 354 and the UD fibres of the second fibre mat 355 are shown cut taperingly such that the UD fibres of the two fibre mats 354, 355 adjoin each other at a common boundary, which forms a tapering transition between the UD fibres of the two mats 354, 355 in the longitudinal direction. The splicing is in this embodiment facilitated by a double stitching 360.

(32) FIG. 10 illustrates a top view of a fifth embodiment of an assembled layer according to the invention, where UD fibres of a first fibre mat 454 are spliced with UD fibres of a second fibre mat 455. The UD fibres of the first fibre mat 454 and the UD fibres of the second fibre mat 455 are shown cut taperingly such that the UD fibres of the two fibre mats 454, 455 adjoin each other at a common boundary, which forms a tapering transition between the UD fibres of the two mats 454, 455 in the longitudinal direction. The splicing is in this embodiment facilitated by a single stitching line 460.

(33) FIG. 11 illustrates a top view of a sixth embodiment of an assembled layer according to the invention, where UD fibres of a first fibre mat 554 are spliced with UD fibres of a second fibre mat 555. The UD fibres of the first fibre mat 554 and the UD fibres of the second fibre mat 555 are shown cut taperingly such that the UD fibres of the two fibre mats 554, 555 adjoin each other at a common boundary, which forms a tapering transition between the UD fibres of the two mats 554, 555 in the longitudinal direction. The splicing is in this embodiment facilitated by a zigzag stitch 560.

(34) While the embodiments are shown as the preferred embodiment with a tapering transition between, it is recognised that the common boundary does not necessarily have to be tapered. However, in general the UD fibres of the two mats should overlap in the longitudinal direction such that the splicing may be achieved.

(35) Further, it is recognised that it is possible to combine the stitching methods shown in FIGS. 9-11, e.g. by combining the zigzag stitch with the single stitch or double stitch.

(36) However, it is also possible to achieve a splicing of the fibres via a butt joint like boundary between the UD fibres of the two fibre mats as shown in FIG. 12. In this embodiment, the UD fibres of a first fibre mat 654 are spliced with UD fibres of a second fibre mat 655 via a scrim 670. The scrim may for instance be a glass tape or a chopped strand mat. The scrim may be connected to the two fibre mats via stitching, a frictional connection, an adhesive or a combination of these.

(37) FIG. 13 shows one example of the steps involved in producing an assembled fibre layer 752 according to the invention. In a first step 700, a first fibre mat 754 comprising bundles of UD fibres 774, which are stitched 784 in the transverse direction, is unstitched in an end region of the first fibre mat 754. The longitudinal extent of the region being unstitched may for instance be approximately 10 cm. In a second step 710, the end of the first fibre layer 754 is cut taperingly. In a third step, the UD fibres are combed and aligned such that it is ensured that the strands extend in the longitudinal direction.

(38) In a fourth step 730, a second fibre mat 755 comprising bundles of UD fibres 775, which are stitched 785 in the transverse direction, is unstitched in an end region of the second fibre mat 755. The longitudinal extent of the region being unstitched may for instance be approximately 10 cm. In a fifth step 740, the end of the second fibre layer 755 is cut taperingly. In a sixth step, the UD fibres are combed and aligned such that it is ensured that the strands extend in the longitudinal direction.

(39) In a seventh step 760, a Neoxil powder 788 is applied to the unstitched UD fibres of the first fibre mat 754. The second fibre mat 755 is then in an eighth step 770 arranged so that the unstitched UD fibres of the second fibre mat 755 overlap with the unstitched UD fibres of the first fibre mat 754. In a ninth step 780, the unstitched overlapping UD fibres are heated and ironed such that the Neoxil powder melts and provides a splicing between the UD fibres of the two mats 754, 755 and the assembled fibre layer 752 is formed.

(40) While the method of producing the assembled fibre layer according to the invention is shown for the splicing being carried out via the use of an adhesive powder, it is recognised that the splicing steps can also be carried out via other adhesives, stitching, frictional connection or a combination thereof.

(41) FIG. 14 shows a schematic front view and FIG. 15 shows a schematic side view of a roller system, which can be used to provide a frictional connection between UD fibres of a first fibre mat 854 and a second fibre mat 855. The roller system comprises a first roller 890 and a second roller 895. The first roller 890 has a corrugated surface with a number of ridges 891. The first roller is hollow and comprises a number of holes 892 in the surface. The second roller is also hollow and comprises a number of holes 896 in the surface. The roller system makes it possible to apply pressurised air to an inlet 897 of the second roller and apply suction 893 to the hollow interior of the first roller. The emission of air through the holes 896 of the second roller 895 creates loose fibre strands to the unstitched UD fibres, whereas the suction through the holes 892 ensures that the strands are aligned in the ridges 891 of the first roller 890. The distance between the two rollers 890 is set according to the thickness of the fibre mats 854, 855. The width and depth of the ridges 891 of the first roller 890 are set according to the desired cross-sectional UD fibre bundle size. The rollers 890 and 895 are rolled along the UD fibres of the two fibre mats 854, 855 in the longitudinal direction and may be rolled back and forth for a predetermined time or until a sufficient frictional connection is achieved.

(42) The invention has been described with reference to advantageous embodiments. However, the scope of the invention is not limited to the illustrated embodiments, and alterations and modifications can be carried out without deviating from the scope of the invention.

(43) TABLE-US-00001 List of reference numerals 2 wind turbine 4 tower 6 nacelle 8 hub 10 blade 14 blade tip 16 blade root 18 leading edge 20 trailing edge 30 root region 32 transition region 34 airfoil region 36 pressure side shell part 38 suction side shell part 40 shoulder 50 spar cap/main laminate 52 fibre layers .sup.52 assembled fibre layer 54, 154, 254, 354, 454, first fibre mat 554, 654, 754, 854 55, 155, 255, 355, 455, second fibre mat 555, 655, 755, 855 56 common boundary 360, 460, 560 stitches 670 scrim 700, 710, 720, 730, 740, steps 750, 760, 770, 780 774, 775 unidirectional fibres 784, 785 stitches 788 powder adhesive 890 first roller 891 ridges 892 holes 893 suction 895 second roller 896 holes 897 inlet r local radius, radial distance from blade root L blade length