REPAIR FILAMENT AND PROCESS FOR REPAIRING A WIND TURBINE PROTECTION TAPE

Abstract

A method for repairing the surface of rotor blades or aircraft wings, comprising (c) a composite substrate (1); and (d) a protection layer (2) having at least one area of at least partial damage, the method comprising: (vii) removing at least part of the damaged part of the protection tape (2); (viii) optionally, reconstructing the surface of damaged composite substrate (1); (ix) optionally, applying primer (6) solution to the surface of the composite substrate; (x) optionally, applying a polymer solution, preferably in at least one organic solvent; (xi) applying heat so as to heat the surface of the composite substrate; (xii) applying a polymer filament (7) onto the surface of the composite substrate so that the polymer filament melts and covers the damaged area.

Claims

1. A method for repairing the surface of rotor blades or aircraft wings, comprising (a) a composite substrate; and (b) a protection layer having at least one area of at least partial damage, the method comprising: (i) removing at least part of a damaged area of the protection layer; (ii) optionally, reconstructing a surface of damaged composite substrate; (iii) optionally, applying a primer solution to the surface of the composite substrate; (iv) optionally, applying a polymer solution, preferably in at least one organic solvent; (v) applying heat so as to heat the surface of the composite substrate; (vi) applying a polymer filament onto the surface of the composite substrate, after step (v), so that the polymer filament melts and covers the damaged area.

2. The method according to claim 1, wherein the protection layer of the rotor blade or aircraft wing comprises at least one thermoplastic elastomer.

3. The method according to claim 1, wherein the polymer filament comprises at least one thermoplastic elastomer.

4. The method according to claim 3, wherein the protection layer comprises at least one thermoplastic elastomer, and wherein the at least one thermoplastic elastomer in the polymer filament and the protection layer is selected from thermoplastic polyurethane, styrenic block copolymers, thermoplastic olefins, elastomeric alloys, thermoplastic copolyesters, thermoplastic polyamides and combinations thereof.

5. The method according to claim 4, wherein the elastomer in the polymer filament is the same polymer as the elastomer in the protection layer.

6. The method according to claim 1, wherein a polymer in the polymer solution is the same as in the polymer filament and/or the protection layer.

7. The method according to claim 1, wherein the at least one organic solvent of the polymer solution is selected from tetrahydrofuran, diethylether, dichloromethane, trichloromethane, ethyl acetate, dimethylformamide, ethanol, cyclohexane, butanol, pentanol, hexanol, diethylene glycol, diethylene glycol dimethyl ether, methyl tert-butylether, methylene chloride, pentane, hexane, petroleum ether, xylene, and mixtures thereof, preferably tetrahydrofuran, isopropanol, ethanol, and mixtures thereof.

8. The method according to claim 1, wherein the melted polymer filament covers the edges of the protection layer surrounding the damaged area.

9. The method according to claim 1, wherein the heat applied in step (v) is in the range of from 120 to 500° C.

10. The method according to claim 1, wherein the heat is also applied during step (vi).

11. The method according to claim 10, wherein the heat applied in step (vi) is applied until the temperature of the polymer filament reaches 140 to 170° C.

12. The method according to claim 1, with a further step (vii) of flattening the applied melted polymer filament material so that it is evenly applied over the area of at least partial damage.

13. The method according to claim 12, wherein any excessive melted polymer filament material is spread over the edge of the protection layer surrounding the damaged area, e. g. during step (vii).

14. (canceled)

15. The method according to claim 1, wherein the protection layer is located on a leading edge of the rotor blade, preferably wherein the protection layer is a rain erosion protection layer.

16. The method according to claim 4, wherein the at least one thermoplastic elastomer in the polymer filament and the protection layer is a thermoplastic polyurethane.

17. The method according to claim 1, preferably wherein the protection layer is a rain erosion protection layer.

Description

DRAWINGS

[0057] The invention will now be described in more detail with reference to the following Figures exemplifying particular embodiments of the invention:

[0058] FIG. 1 schematic drawing of a cross-section of a substrate and a protection layer with an area of a partial damage;

[0059] FIG. 2 schematic drawing of the substrate with protection layer of FIG. 1 with removed parts of the protection layer;

[0060] FIG. 3 schematic drawing of the substrate with protection layer of FIGS. 1 and 2 with a primer solution being applied;

[0061] FIG. 4 schematic drawing of the substrate with protection layer of the preceding figures with a polymer filament being held in the area of the partial damage;

[0062] FIG. 5 schematic drawing of the substrate with protection layer of the preceding figures with a molten piece of the polymer filament and

[0063] FIG. 6 schematic drawing of the substrate with protection layer of the preceding figures with a flattened piece of the polymer filament.

[0064] Herein below various embodiments of the present invention are described and shown in the drawings wherein like elements are provided with the same reference numbers.

[0065] In FIG. 1 a cross-section of a substrate 1 with a protection layer 2 can be seen. The protection layer 2 comprises a polymer layer 3 and an adhesive layer 4, wherein the adhesive layer is positioned between the polymer layer 3 and the substrate 1 and serves to adhere the polymer layer 3 to the surface of the substrate 1. The polymer layer 3 may for example comprise a thermoplastic polyurethane. The adhesive layer 4 may for example be a pressure sensitive adhesive. FIG. 1 further shows an area of a minor damage 5 in the protection layer 2 applied to the substrate 1 and the substrate 1. The damage effects the polymer layer 3, the adhesive layer 4 and the substrate 1.

[0066] In FIG. 2 the damaged area of FIG. 1 is shown after the surrounding damaged protection layer 2 has been removed. This may be advantageous in order to get a clean edge of the protection layer 2 and also to remove loose material from the damaged area. This process may for example be done with the help of a knife cutter by performing a circular cut or longitudinal cuts around the damaged area.

[0067] It may be advantageous to clean the surface of the damaged area for example with isopropyl alcohol and a lint-free cloth in order to remove any residuals of the adhesive and any other dirt.

[0068] As shown in FIG. 3, the surface may then be primed with an adhesion promoter or primer 6. The primer 6 should be applied to the surface and the edges of the surrounding protection layer 3 as well, as also shown in FIG. 3.

[0069] As a next step the surface of the damaged area as well as the surrounding edges of the protection layer 2 will be heated. This can for example be done with a hot air blower or heat gun. After the surface has been sufficiently heated (usually visible when the surrounding protection layer starts to gloss) a polymer filament 7 is brought in contact with the hot surface as shown in FIG. 4. It is possible to still heat the damaged area while the polymer filament 7 is brought in contact with the hot surface. The polymer filament 7 may for example comprise a thermoplastic polyurethane. It may start to melt as soon as it gets in contact with the heated area or as soon as it gets heated through for example hot air. To separate the molten part of the polymer filament 7 from the rest of the filament additional heat may be applied. A molten polymer filament 8 in the damaged area is shown in FIG. 5. The molten material 8 may then be evenly applied to the damaged area for example by means of a silicon rubber roll (not shown). Any excessive material will be spread out over the surrounding protection layer 2. A smooth transition between tape and repair material from the polymer filament 7 may be obtained. If the edges of the polymer filament 7 are heated long enough it is even possible to fuse the repair material from the polymer filament 7 with the polymer material from the protection layer 2.

EXAMPLES

[0070] The present disclosure is further described without however wanting to limit the disclosure thereto. The following examples are provided to illustrate certain embodiments but are not meant to be limiting in any way. Prior to that some test methods used to characterize materials and their properties will be described.

[0071] Materials Used:

[0072] 3M W8750 tape: thermoplastic polyurethane tape having acrylic PSA layer

[0073] 3M W9910 primer

[0074] Krystalgran PE

[0075] Isopropyl Alcohol

[0076] Application Solution (mixture of 75 wt.-% demineralized water and 25 wt.-% Isopropyl Alcohol)

[0077] Grit 320 sand paper

[0078] Heat Gun (Hot Air Blower) with adjustable temperature setting

[0079] Small Paint Brush

[0080] Rubber Roller (e. g. 3M Safety-Walk Rubber Hand Roller 903)

[0081] Polymer Filament

[0082] The polymer filament is produced by extrusion of Krystalgran PE on a Collin Teach-Line E20T with a simple circular die opening. Extrusion conditions were as follows:

[0083] Zone 1: 120° C.

[0084] Zone 2: 150° C.

[0085] Zone 3: 150° C.

[0086] Zone 4: 150° C.

[0087] Die: 150° C.

[0088] Screw speed: 50 rpm

[0089] Melt pressure: 46 bar

[0090] After extrusion the strand was pulled through a water basin for cooling and wound onto spools. It was also demonstrated that various additives—such as UV absorbers and stabilizers such as for examples hindered amine light stabilizers (HALS) can be easily added to the resin. The filament diameter can be adjusted and controlled by haul-off speed and ranged from approximate 1 to 2 mm.

[0091] Application Procedure

[0092] The test blade profiles surfaces having a length of 225 mm simulating the leading edges of wind turbines in the rain erosion text as described herein were ground with grit 320 abrasive paper, cleaned with isopropyl alcohol and allowed to dry under ambient conditions. Two sheets of wind protection tape were prepared. The size of each sheet was selected in such a way that there was a 5-10 mm excess of the sheet on the long as well on both of the short sides of the profile. Also, there was a small gap between the two pieces at the front edge of the profile.

[0093] Both sheets were made of 3M Wind Protection Tape W8750. The liner was removed from the first tape sheet and the PSA side of the tape as well as the profile surface were sprayed with the application solution. Next, the tape sheet was affixed with its PSA side onto one side of the profile. The tape was positioned in such a way that there was a 5-10 mm excess of the sheet on the long as well on both of the short sides of the profile and a distance of approx. 5 mm to the very outer leading edge of the profile. The outer surface of the tape sheet was then sprayed with application solution. A rubber squeegee was used to carefully squeeze out the application solution without moving or stretching the tape sheet. Accordingly, all air bubbles and water pockets which were visible under the tape sheet were removed. These steps were repeated with the second tape sheet on the other side of the profile. After that, the profile was allowed to dry for at least 1 hour under ambient conditions.

[0094] Next, excess tape material was sliced off from the long and short edges of the profile. A Heat Gun was used to further carefully dry the gap between the two tape sheets on the profile. After that, W9910 adhesion promoter was applied onto the surface of the profile in the gap between the two tape sheets by means of a small paint brush. Again, a Heat Gun was used to evaporate the adhesion promoter solvent.

[0095] A Heat Gun with a temperature setting of 270° C. was used to gently heat-up the damaged area. As soon as the edges of the surrounding protection layer started to gloss, the repair polymer filament was brought into contact with the damaged area. The polymer filament stated to melt. At that time, a rubber roller was used in order to push the molten polymer filament towards the surface of the substrate. Additional heat and pressure was applied in order to finalize the bonding process and flatten the edges of the molten polymer filament. The test profiles were allowed to cool down under ambient conditions. Any excess material was removed. Finally, the profiles were stored for 1 week under ambient conditions to obtain final performance.

[0096] Test Method:

[0097] Rain Erosion Test

[0098] The anti-erosion properties were measured with the rain erosion test method according to ASTM G73-10.

[0099] The test profiles obtained as described above were mounted on the blades of a rotor, which was rotated to provide a speed ranging from test velocity of 160 m/s at the tip of the blades to a test velocity of 143 m/s in the center and 126 m/s at root.

[0100] Rainfall was simulated by spraying water (23° C.), having a droplet size of about 2 mm, with a velocity of 30 mm/hour onto the rotating blades inside the rig. The test was stopped every 30 minutes after which the coated surfaces were visually inspected. The test was run during 18 hours.

[0101] Rain Erosion Test Results

[0102] The examples were visually inspected and any damage or erosion to the tape surfaces were determined. For both examples, no visible damage or breakthrough of the repair areas could be observed. Thus, it can be concluded that the method as described herein is excellently suited for repairing erosion tape surfaces of rotor blades such as rotor blades of wind turbines.