GB2510841A

GB2510841A - A method for manufacturing an elongated composite material object, such as a wind turbine blade spar

Info

Publication number: GB2510841A
Application number: GB1302581.2A
Authority: GB
Inventors: Anton Bech
Original assignee: Vestas Wind Systems AS
Current assignee: Vestas Wind Systems AS
Priority date: 2013-02-14
Filing date: 2013-02-14
Publication date: 2014-08-20
Also published as: GB201302581D0

Abstract

A method for manufacturing an elongated composite material object, such as a part for a wind turbine blade, for example a wind turbine blade spar, having the following steps: providing a first strip including a resin; providing a second strip including a fibrous material, but not including any resin; providing an elongated tool, such as a mandrel; winding the first and second strips around the tool simultaneously, and finally; allowing at least a part of the resin provided by the first strip, to impregnate the fibrous material of the second strip, thus forming the elongated composite material object. The first strip may also have fibrous material in addition to the resin, and the quantity of resin may be sufficient to fully impregnate the fibrous material in both the first and second strips. The step of winding may involve providing each strip 11, 21 on a separate roll 1, 2 rotatably mounted on a carrier 4 and rotating the carrier around the tool 3 in direction A while sliding it along in direction B.

Description

A METHOD FOR MANUFACTURING AN ELONGATED COMPOSITE MATERIAL OBJECT,

SUCH AS A WIND TURBINE BLADE SPAR

TECHNICAL FIELD

The invention relates to a method for manufacturing an elongated composite material object, such as a wind turbine blade part, for example a wind turbine blade spar.

BACKGROUND

Some wind turbine blade manufacturing processes include fabrication of a spar for the blade. This fabrication might include winding of a composite material, semipreg strip onto a mandrel. The semipreg strip comprises a fibrous material, e.g. glass fiber or carbon fiber, which is partially impregnated with resin. US8088470 describes an example of such a strip.

The semipreg strip can be a biax semipreg, i.e. a semipreg strip in which there are two layers of fibers which have a fiber orientation of -i-I-45 degrees, respectively, in relation to the longitudinal direction of the strip. The partial impregnation allows for trapped air to be bled or evacuated during the subsequent resin curing operation, wherein the resin moves so as to fully impregnate the wound strip. Even it such a process is advantageous, there is a desire to reduce the time and complexity of it. In particular, semipreg strips are complicated to manufacture.

SUMMARY

It is an object of the invention to reduce the time and complexity of manufacturing an elongated composite material object, including a process of winding a composite material strip onto a tool.

This object is reached with a method for manufacturing an elongated composite material object, such as a wind turbine blade part, for example a wind turbine blade spar, the method comprising the steps of -providing a first strip including a resin for the composite material of the elongated composite material object, -providing a second strip including a fibrous material for the composite material of the elongated composite material object, but not including any resin br the composite material of the elongated composite material object, -providing an elongated tool, such as a mandrel, -winding simultaneously the first and second strips around the tool, so as to deposit the first and second strips onto the tool, or onto a material provided on the tool, and -allowing, after the step of winding, at least a part of the resin, provided by the first strip, to impregnate the fibrous material of the second strip.

Preferably the second strip, not including any resin, is dry. The impregnation of the fibrous material of the second strip with resin provided by the first strip is preferably done during a curing process of the resin. Preferably, the first strip includes, in addition to the resin, a fibrous material. Preferably, the fibrous material of the first strip is used for reinforcing the composite material object to be manufactured. The first strip could be a prepreg strip, i.e. a strip where the fibrous material is fully impregnated with resin. However, the first strip could also be a semipreg strip. The fiber arrangement of the strips can be of any kind suitable for the process undertaken, e.g. biax fiber strips or unidirectional fiber tows.

Where one strip is prepreg (or semipreg) and the other strip is dry fabric, the amount of preimpregnated material can be halved, which provides cost saving. In addition, since a fully impregnated strip can be used, the invention eliminates the need for semi-preg strips, which are relatively complicated to manufacture and to handle, and thus the invention reduces the complexity of manufacturing an elongated composite material object, including the process of winding.

It should be mentioned that preferably, the method comprises, after the step of winding, curing the resin provided in the first strip during the step of winding. Where the resin is a thermoset, that is cured by raising the temperature of it, the resin obtains during an initial phase of the curing process, a relatively low viscosity, so that part of it flows from the first strip to the second strip to impregnate the latter. Preferably, the first strip includes, during the step of winding, more resin than needed to fully impregnate the fibrous material in the first strip. Preferably, the first strip includes an excess of resin which is sufficient to fully impregnate the fibrous material in the second strip, after the step of winding.

In alternative embodiments, the first strip does not include, in addition to the resin, any fibrous material for reinforcing the composite material object to be manufactured. For example, the resin could be a thermoplastic resin, which is solid in room temperature, and therefore suitable for forming the first strip. Alternatively, the first strip could include a substrate, for example a thin weave, which could carry the resin, e.g. a thermoset resin, during the step of winding.

Preferably, the step of winding includes providing the first strip on a first roll and providing the second strip on a second roll, providing the first and second rolls on a holder which is rotatably mounted on a carrier, and rotating the holder relative to the carrier so as to move the rolls around the tool. The holder and the carrier can then be parts of a winding machine.

Preferably, the step of winding includes moving the carrier along the tool while performing said step of rotating the holder relative to the carrier. Preferably, the step of moving the carrier includes moving the carrier along the longitudinal direction of the tool. Preferably, the step of winding includes depositing the first and second strips so that they partially overlap each other on the tool or on the material provided on the tool.

Thus, for example in the case of a wind turbine blade spar manufacturing process, the spar can be wound with two rolls or spools on the same holder or rotor, and thereby, and the process time can be reduced compared to a case where only one roll is used.

It should be mentioned that in alternative embodiments, the first and second rolls and the carrier could be stationary, and tool could be rotating. Thereby, the step of winding simultaneously the first and a second strip around the tool, could include moving the tool in its longitudinal direction past the rolls while simultaneously rotating the tool around its longitudinal axis so as to deposit the first and second strips onto the tool.

The object is also reached with an elongated composite material object in the form of a spar for a wind turbine blade, according to claim S. The object is also reached with a wind turbine blade according to claim 9.

DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will be described closer below with reference to the drawing, in which fig. 1 shows a perspective view of a mandrel and parts of a winding machine winding strips onto the mandrel, and fig. 2 shows a longitudinal cross-section of the mandrel.

DETAILED DESCRIPTION

Fig. 1 shows a winding process for a wind turbine blade spar section with two material spools herein also referred to as rolls 1, 2. A first 01 the rolls 1 includes a first strip 11 of prepreg, and a second of the rolls 2 includes a second strip 21 of dry fibrous material. The material of the strips 11, 21 is deposited in a double spiral mode around a mandrel 3. For this, the rolls 1, 2 are mounted on a holder 4, which in turn is rotatably mounted on a carrier (not shown). The holder extends around the mandrel 3 and is rotated as indicated by the arrows A, and the carrier with the holder 4 is moved along the mandrel 3 as indicated by the arrow B. In fig. 2 the material 11, 21 can be seen as positioned onto the mandrel 3. The alternating order of prepreg 11 and dry glass 21 allows, during the subsequent curing process, entrapped air to be evacuated freely. In this respect the material built onto the mandrel 3 will be similar to a semipreg. As a matter of fact, it will have improved breathability compared to a semipreg as the dry web is 100% free from resin. It should be noted that preferably, the prepreg first strip 11 contains more rosin than needed to fully impregnate it. More preferably, it contains an excess of resin which is sufficient to impregnate the dry second strip 21 fully during the curing process.

The winding with two spools 1, 2 will with the same areal weight of the webs require the double advancement of the rotor in the spanwise direction, (parallel to the mandrel's longitudinal direction), to reach the same areal weight on the mandrel 3. This means that the off angle of the web (strip) angle to the spar axis will be doubled. This means e.g. that at a location a +1-45°web will be at 55°/-35° orientation, where it would have been placed at 50°!-40 °orientation with a single spool. As most of the mandrel has a large perimeter vs. the width of the web, the off angle issue will not be profound. In cases where the increased advancement has issues, the web width can be smaller to counteract it.

The spools can be located opposite each other on the rotor (holder 4), but they do not have to be so. If they are opposite to each other (1800 apart), they can be located in the same axial position and can perform variable pitch windings without adjustments. They can also be positioned closer to one another than 180°. Then they must be offset relative to another in their axial position. At variable pitch this offset will have to vary accordingly to the advancement of the winding, if equal stagger between the prepreg and dry fabrics is desired.

Claims

CLAIMS1. A method for manufacturing an elongated composite material object, such as a wind turbine blade part, for example a wind turbine blade spar, the method comprising the steps of -providing a first strip including a resin for the composite material of the elongated composite material object, -providing a second strip including a fibrous material for the composite material of the elongated composite material object, but not including any resin for the composite material of the elongated composite material object, -providing an elongated tool, such as a mandrel, -winding simultaneously the first and second strips around the tool, so as to deposit the first and second strips onto the tool, or onto a material provided on the tool, and -allowing, after the step of winding, at least a part of the resin, provided by the first strip, to impregnate the fibrous material of the second strip.
2. A method according to claim 1, wherein the first strip includes, in addition to the resin, a fibrous material for the composite material of the elongated composite material object.
3. A method according to claim 2, wherein the first strip includes, during the step of winding, more resin than needed to fully impregnate the fibrous material in the first strip.
4. A method according to claim 3, wherein the first strip includes an excess of resin which is sufficient to fully impregnate the fibrous material in the second strip, after the step of winding.
5. A method according to any one of the preceding claims, wherein the step of winding includes providing the first strip on a first roll and providing the second strip on a second roll, providing the first and second rolls on a holder which is rotatably mounted on a carrier, and rotating the holder relative to the carrier so as to move the rolls around the tool.
6. A method according to claim 5, wherein the step of winding includes moving the carrier along the tool while performing said step of rotating the holder relative to the carrier.
7. A method according to any one of the preceding claims, wherein the step of winding includes depositing the first and second strips so that they partially overlap each other on the tool or on the material provided on the tool.
8. An elongated composite material object in the form of a spar for a wind turbine blade, made with a method according to any of the claims 1-7.
9. A wind turbine blade, including a spar according to claim 8.