JP2002137307A - Blade structure of windmill made of fiber-reinforced resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a further lighter blade structure of a state having a higher bending fatigue strength than that of prior art. SOLUTION: The blade structure 1 of a windmill made of an FRP containing reinforcing fibers and the resin having a width W, a flange 10 of a girder having a width Wf of a range of 0.2 to 0.5 W at sectional central positions 3 and 4 of gravity of the blade 1, carbon fiber-reinforced resin layers 14 and high elongation fiber-reinforced resin layers 15 alternately laminated thereon. In this case, a total thickness 2Tf occupying the upper and lower flanges 10 of a composite layer 17 is in a range of 10 to 30% of the thickness T of the blade. The layer 17 is a laminate containing a carbon fiber-reinforced resin layer having a thickness of at least one layer oriented in a longitudinal direction of the blade of at least 70% or more of its volume is 16 mm, and the glass fiber-reinforced resin layer having a thickness of 0.2 to 1.5 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a wind turbine blade structure used for wind power generation, and more particularly, to a lightweight blade structure having high bending fatigue strength.

[0002]

2. Description of the Related Art As is well known, wind turbine blades for wind power generation have a streamlined blade cross-sectional structure, and the required performance is that lightness is important for a rotating body. Also, blades made of fiber reinforced resin (hereinafter referred to as FRP) having high specific strength and specific elastic modulus have been put to practical use.

[0003] Incidentally, since a wind turbine blade made of FRP is usually formed by stacking a plurality of layers of FRP sheets, the cross section of the blade has a layered structure, and the reinforcing fibers in the layer mainly consist of the blade. They are arranged in the longitudinal direction. In addition, since a bending moment is generated in the longitudinal direction of the blade due to wind force, a large number of fibers are arranged in the longitudinal direction of the blade (for example, JP-A-6-66244) to prevent the life of the blade from being shortened by bending fatigue. Has been taken. Furthermore, compression, torsion, shearing, etc. are acting on the blade in a complicated manner due to centrifugal force, fluctuating load per rotation due to its own weight, vibration, etc., and considerable effort is required to quantify those effects. Therefore, conventionally, in addition to the fibers arranged in the longitudinal direction of the blade, the fibers are arranged in a direction of ± 45 ° to 90 ° with respect to the longitudinal direction, and a quasi-isotropic near-isotropic laminating structure is adopted. I was For example, Japanese Patent Application Laid-Open No. 3-27
In Japanese Patent No. 1566, a blade having a fiber orientation angle of 10 to 50 degrees is provided, and in Japanese Patent Application Laid-Open No. 6-66244, a glass cloth and a glass mat are laminated in a bandage shape on one-way roving in the longitudinal direction. An arrangement of blades is disclosed. Japanese Patent Application Laid-Open No. 11-311101 discloses a structure in which fibers are arranged in the longitudinal direction of the blade in addition to the fibers arranged in the longitudinal direction in order to improve the bending fatigue life. Is disclosed.

However, in the conventional blades having such a laminated structure, the entire wind turbine is increased in size and the power generation efficiency of the wind turbine is improved with an increase in the number of reinforcing fibers laminated, but from the viewpoint of weight and durability, In any case, there is a problem that there is a limit in reducing the weight and improving the fatigue life. In particular, as the blade length increases, the weight of the blade also increases in proportion to the power of 2.5 to 3 times the length, so that the load on the rotating mechanism increases and there is a weight limit. Further, when the weight of the blade is heavy, there is a problem that the stress generated in the plane is increased, and the handleability during production, transportation, and mounting is deteriorated. Therefore, there is a need for a blade that is lighter and has higher flexural fatigue strength and flexural rigidity.

Therefore, the conventional blade structure is made of FRP
However, the laminated structure of the reinforcing fibers does not always make full use of the light weight effect, which is the greatest advantage of the above, and the industry has required a more suitable laminated structure for the blade structure.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has a higher level of performance than the conventional one by optimizing the laminated structure of reinforcing fibers in a wind turbine blade made of FRP. An object of the present invention is to provide a lightweight blade structure having bending fatigue strength.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a hollow wing shaped cross section made of fiber reinforced resin having a horizontal width (W) and a vertical thickness (T). In the wind turbine blade structure provided with a flange portion which is a girder member,
It has a width (Wf) in the range of 0.2 to 0.5 (W) in the horizontal direction around the center of gravity of the cross section of the blade, and (B) the carbon fiber reinforced resin layer before and 2-6
% Of a high elongation fiber reinforced resin layer in a range of (C) a total thickness (2Tf) of the composite layer and a thickness (T) of the blade. Of 10
The present invention provides a wind turbine blade structure made of fiber reinforced resin, wherein the wind turbine blade structure is in the range of up to 30%.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A wind turbine blade structure according to the present invention will be described with reference to the drawings of one embodiment shown in FIGS. FIG.
2 shows the definition of the axis of the blade structure according to the present invention and the arrangement angle of the reinforcing fibers. The longitudinal axis 2 of the blade 1 in the present invention is defined by a sectional center of gravity 3 at the root of the blade and a sectional center of gravity 4 at a position の of the blade length.
Is defined by a straight line connecting. In addition, the length of the blade is 10
It is about 50 m.

FIG. 2 is a cross-sectional view of a plane perpendicular to the longitudinal axis 2 at the center 4 of the blade 1 in FIG. 1 and has a streamlined thickness T (vertical distance of the maximum blade thickness). The cross section of the blade 1 is composed of an outer plate called an upper skin 7 and a lower skin 8 connecting a front edge portion 5 and a rear edge portion 6, and an upper skin 7 and a lower skin 8
In the meantime, over the longitudinal direction of the blade, a horizontal width Wf called a spar 9 having a layered structure and a vertical thickness Tf
Box-shaped girders. Furthermore, spar 9
Flange portion 10 in contact with inner peripheral surfaces of skins 7 and 8
And a web part 1 connecting the upper and lower flanges of the blade
1 and 1. The spar 9 may have a C shape, an I shape, or a plate shape in addition to the box shape. The upper and lower skins are preferably made of fiber reinforced resin for reasons of weight reduction and corrosion resistance.

FIG. 3 is a sectional view of the flange portion 10 of FIG. As shown in the figure, the flange portion 10 forms a composite layer 17 including a carbon fiber layer 14, a glass fiber layer 15, and an adhesive layer 16, which are integrally laminated and have a vertical thickness of T.
f. The carbon fiber layer 14 is formed by impregnating a matrix resin 13 into a reinforcing fiber 12 described later, the glass fiber layer 15 is formed by impregnating glass fiber with a matrix resin, and the carbon fiber layer 16 is formed by mixing carbon fiber with a matrix resin. It is impregnated.

The most influence on the bending stiffness of the blade 1 is shown in FIG.
The width Wf of the flange portion 10 is a width in the range of 0.2 to 0.5 W in the horizontal direction with respect to the blade width W around the center of gravity 3 and 4 of the cross section. It is necessary to have This is because whether the width of the flange portion 10 becomes wider or narrower, the average cross-sectional height becomes lower, and the bending rigidity of the entire blade decreases.
Further, the bending rigidity per blade weight decreases as the thickness Tf of the composite layer 17 of the flange portion 10 increases.
Therefore, the width Wf of the flange portion has a width of 0.2 to 0.5 W with respect to the blade width W, and the thickness Tf of the composite layer 17 of the flange portion 10 is in the range of 10 to 30% of the thickness T of the blade. Is preferably within the range.

When the thickness T of the blade is kept constant, the width of the flange portion Wf is plotted on the horizontal axis, and the weight of the blade when the thickness of the composite layer 17 of the flange portion is changed is plotted on the vertical axis. As shown in FIG. 4 that the width Tf of the flange 10 has a width of 0.3 to 0.4 W, and the thickness Tf of the composite layer 17 of the flange 10 is
When the thickness T is within the range of 15 to 25% of the thickness T of the blade, the total weight of the blade 1 is optimized and reduced, indicating that the weight is further reduced while securing the bending rigidity and the bending fatigue strength. ing.

The most influential on the bending fatigue life of the blade 1 is the bending fatigue characteristics of the composite layer 17 of the flange portion 10 shown in FIG. In order to obtain excellent bending fatigue properties, the composite layer 17 should be at least ±± with respect to the longitudinal direction 2 of the blade 1.
A layer 14 having carbon fibers arranged at an angle within 9 degrees,
It is preferable that the matrix resin having a high elongation has a structure in which the glass fiber layers 15 are alternately continuous. In order to improve the torsional rigidity of the blade, if necessary, for example, a carbon fiber layer 16 made of carbon fibers having an orientation angle of ± 45 ° is used.
May be laminated.

The layer 14 is mainly composed of the longitudinal axis 2 of the blade 1.
It is responsible for the directional rigidity and strength, and the preferable arrangement angle of the reinforcing fibers is preferably in the range of +9 degrees to -9 degrees. The larger the length of the blade, the greater the amount of deformation of the blade. Therefore, it is more preferable that the arrangement angle is closer to the 0 degree direction than the above range because the rigidity of the blade is increased and the deflection is reduced.

The layer 15 is formed by being continuous with the layer 14.
Plays a role in improving the bending fatigue life of
As a result, the bending life of the blade is significantly improved. That is, since the layer 15 uses a high elongation matrix resin having an elongation of 3 to 10%, the elongation at break increases, the shear strength between layers increases, and the strain generated in the layer 14 is locally reduced. Has the effect of suppressing the destruction of the layer 14, and has the effect of preventing the layer 14 from being broken at the time of bending fatigue and increasing the compressive load bearing capacity of the layer 14 because it is continuous with the layer 14. . When the arrangement angle θ of the reinforcing fibers in the layer 15 is within the same range as that of the layer 14, in addition to the above effects,
Since its own compressive strength is high, it has the effect of increasing the overall compressive strength, which is more preferable. The arrangement angle θ of the reinforcing fibers of the layer 15 is, as described in JP-A-11-311101, to improve the bending fatigue life.
The fibers may be arranged in a direction within ± 50 ° to 70 ° with respect to the longitudinal direction, or may be within ± 45 ° or 0/90 °. In the present invention, “the layers are continuous” means, for example, that the layers are adjacent to each other without being sandwiched by another fiber-reinforced resin or the like. The thickness of the layer 15 is such that the thickness ratio of the layer 14 to the layer 15 is 1: 0.05 to
It is preferably in the range of 1: 0.3. If it is smaller than this range, the effect of improving the bending fatigue life is not sufficient, and if it is larger, the rigidity in the longitudinal direction tends to be insufficient. More preferably, it is in the range of 1: 0.05 to 1: 0.2. That is, it is preferable that at least 70% or more of the volume of the composite layer 17 of the flange portion 10 is made of the carbon fiber reinforced resin layer. More preferably, when it is 80% or more, the blade becomes lighter, and the bending rigidity and the bending fatigue life are improved.

In order to maintain the bending stiffness of the blade 1 and improve the bending fatigue life, the layer 14 is
It is preferable to sandwich it. In this case, the effect is higher and the bending fatigue life of the blade is significantly improved. By arranging a plurality of layers 15, the effect can be further enhanced. At this time, in order to prevent the rigidity in the longitudinal direction of the blade from being extremely reduced, it is extremely effective to reduce the thickness of one layer of the layer 15 and increase the number of layers without increasing the overall thickness. is there. Above all, it is preferable that the layer composed of the layer 15 is provided in mirror symmetry with respect to the layer 14 because out-of-plane deformation of the layer 14 is reduced. The out-of-plane deformation becomes more remarkable as the thickness of the blade structure is smaller and as the size of the blade structure is larger. Therefore, if the length of the blade is about 20 m to 50 m, the thickness of the layer 14 is 1 mm to 6 mm. It is preferably within the range.

As the reinforcing fibers for the layers 14 and 15 of the present invention, it is preferable to use carbon fibers and glass fibers, respectively.

Here, the carbon fiber is a so-called carbon fiber produced from a polyacrylonitrile fiber or a pitch through a flame-proofing, carbonization / graphitization step, etc., and the diameter of the single fiber is 5 to 10 μm. And a high-strength type,
High elastic modulus type is commercially available. In the present invention, any of a PAN (polyacrylonitrile) type and a pitch type may be used. Among them, the PAN type carbon fiber has a high radial strength in addition to the above elastic modulus and elongation. It is particularly preferable because it improves the strength and thus the bending fatigue. Further, it is preferable to use carbon fiber for weight reduction. In general, carbon fibers are used in the form of strands in which thousands or hundreds of thousands of single fibers (monofilaments) are bundled. In the present invention, the strands inside the carbon fiber reinforced resin when repeatedly subjected to a bending load are used. From the viewpoint of reducing splitting between carbon fibers, a carbon fiber bundle composed of 24000 or more single fibers having a large strand interval is preferable. Above all, in consideration of the improvement in process (productivity), between 48,000 and 200,000 tow (thick bundle) carbon fibers are more preferable. When the rigidity of the blade 1 is low, the deformation of the blade increases, the deformation distortion amount in the bending mode, which is a problem of the present invention, increases, and bending fatigue easily occurs. Therefore, it is preferable that the blade has high rigidity. The carbon fibers used for the layer 14 preferably have an elastic modulus in the range of 230 to 600 GPa. The use of carbon fibers in this range also has the advantage of improving the torsional rigidity of the blade and maintaining the aerodynamic characteristics of the blade. In order to improve the repetitive bending characteristics, the bending strength of the blade is preferably high, and the strength of the carbon fiber is preferably 3 GPa to 10 GPa. The elastic modulus and strength of carbon fiber are determined by JI
It can be measured by SR7601. Glass fibers have a good balance of compression / tensile strength (compressive strength and tensile strength are almost equal), and have excellent bending properties due to high elongation, and are one of the preferable reinforcing fibers in the present invention. The glass fiber is a so-called E-glass, C-glass, S-glass or the like containing silicon dioxide (SiO ₂ ) as a main component, and has a fiber diameter of about 5 to 20 μm. Also, it has the feature that it can be inexpensive compared to carbon fiber. Since the blade preferably has high strength, the glass fiber used for the layer B preferably has an elongation of 2 to 6%.

The reinforcing fiber is preferably in the form of continuous fiber or long fiber, and is formed by laminating a prepreg in which a continuous fiber is impregnated with a resin to form a sheet, or a woven prepreg in which a continuous fiber fabric is impregnated with a resin. Alternatively, the layer structure may be formed while the resin is impregnated in the strand, roving, woven or mat-like reinforcing fiber. Preferred in terms of strength and rigidity are yarns, strands or rovings.

Next, the resin constituting the layers 14 and 15 includes a thermosetting resin such as an epoxy resin, a vinyl ester resin and an unsaturated polyester resin. Among them, epoxy resin is most preferable in terms of fatigue resistance since it has a high elongation and a high utilization of fiber strength. Epoxy resin is also a preferable resin in terms of blade vibration damping performance. As a preferable resin other than the epoxy resin, a polyester resin is excellent in weather resistance and environmental resistance and is preferable in terms of durability. Vinyl ester resins are also preferable because of their excellent impact resistance. Also, the volume resistivity is 1 × 10 ¹² to 1 ×
A resin in the range of 10 ¹⁶ Ω · cm is preferable in terms of safety because it reduces damage due to energization due to lightning and the like.

Since the elongation of the resin affects the bending fatigue, the elongation of the resin is preferably in the range of 2 to 10%. If the content is 2% or less, the resin itself may fatigue before the fiber, and if it is 10% or more, the resin may creep. The elongation of the resin is determined according to JIS-K7113.

As a means for keeping the elongation within the above range, in the case of an epoxy resin-based thermosetting resin, the curing agent is made to have a flexible structure or the curing temperature is lowered to increase the distance between crosslinking points or to increase the crosslinking. It is effective to reduce the density. Also, it is preferable to suppress the amount of voids in the FRP to 5% or less, since the elongation of the fiber reinforced resin layer increases and the bending fatigue life is improved. When the void amount is 3% or less, the elongation is further improved, which is more preferable. The void amount is determined according to JIS-K7053 or JIS-K7075. When it is necessary to reduce thermal stress, a resin of a curing type at room temperature (10 ° C. to 40 ° C.) is preferable. The volume content of the reinforcing fibers with respect to the resin of the layers A and B is preferably 40% or more and less than 80%. The volume content is JIS-K7052 or JIS-K7075.
Can be measured by

Next, as a method of manufacturing the FRP blade structure of the present invention, any known molding techniques such as a prepreg method, a resin transfer molding (RTM) method, a drawing method, a filament winding method, and a hand lay-up method are used. Can be used. Among them, a prepreg method, an RTM method, and a drawing method are preferable for expressing the strength of the reinforcing fiber and improving the bending fatigue property. The prepreg method is a molding method in which a sheet-like prepreg (intermediate base material) in which a reinforcing fiber is impregnated with a resin is laminated (stacked in layers), and the resin is cured with or without heating. Usually, pressure is applied during curing or lamination.
The RTM method is a molding method in which a base material made of a reinforcing fiber such as a woven fabric or a mat-like material called a preform is set in a predetermined mold, an uncured resin is poured, and the resin is shaped or cured by heating or non-heating. Is the law. The drawing method is a method in which reinforcing fibers are aligned, impregnated with a resin, drawn into a mold, shaped, cured, and continuously formed. The carbon fiber reinforced resin layer of the present invention may be formed by embedding a plate or rod-shaped molded body formed by a drawing method in combination with a molding method such as an RTM method or a hand lay-up method. At that time, the plate thickness is 2mm-6m
m and a width of 10 mm to 100 mm are preferable for molding.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the blade 1 shown in FIGS. 1-3, the total length (W) of the blade is 263 mm and the thickness (T) of the blade is 56 mm.
And SPAN-based carbon fiber (strength 49)
0 MPa, elastic modulus 235 GPa, torsional elastic modulus 25 GP
a, a prepreg (volume content of carbon fiber 60%) composed of epoxy resin (resin elongation 4%, volume resistivity 5.7 × 10 ¹⁵ Ω · cm) and elongation 2%, specific gravity 1.8), and Glass fiber (strength 160 MPa, elastic modulus 75 GPa, elongation 2.1%, specific gravity 2.5) prepreg (fiber volume content 5
5%) to obtain a box having a 3 m long cross section.

The upper and lower flange portions 10 of the spar 9 each have a thickness (Tf) of 5 mm, a width (Wf) of 100 mm, a thickness of the web portion 11 of 5 mm, and a total height of 50 mm (thus, Wf / W is 0). .38, 2Tf / T is 0.18
It is. ).

The laminated structure of the flange portion 10 is the same as that of the lower skin 8
From the side, a layer 15 having a thickness of 0.5 mm and a glass fiber arrangement angle of 0 degree, and a continuous thickness of 3 mm and a carbon fiber arrangement angle of 0 degree.
Layer 14), a layer 15 having a continuous thickness of 0.5 mm and a glass fiber arrangement angle of 0 degree, and a layer 1 having a further continuous thickness of 1 mm.
mm and a layer 16 having an arrangement angle of carbon fibers of ± 45 degrees.

The spar 9 was subjected to a three-point bending fatigue test at a deflection of 70% of the static strength (measurement method: JIS K7118, K
Compliance with the 7082, measurement span: was the 2.5m), lowering of the bending after a few 10 ⁶ cycles stiffness was not observed. No abnormality such as peeling was observed between the 14th and 15th layers in both the upper and lower flanges 10.

The spar 9 molded in the above-described configuration is integrated with a separately laminated outer skin (leading edge portion 5 and skins 7 and 8) with an adhesive so as to have a thickness of 3 mm with glass fiber reinforced resin. When a blade having a length of 23 m was manufactured, the weight was reduced by 34% compared to the all glass fiber blade.

COMPARATIVE EXAMPLE In Example 1, the arrangement angle of the glass fibers of the layer 15 was 9
0 degrees, was exactly the same way bending fatigue test as in Example, the lower flange by the number 10 ⁵ cycles (tension side)
Cracking was observed in the layer 15 of the bending stiffness in 10 ⁶ times is decreased to 90%. It is considered that the reason is that the effect of stress relaxation by the high elongation fiber reinforced resin layer is not exhibited.

[0030]

As described above, the wind turbine blade structure made of fiber reinforced resin according to the present invention has a structure in which the width of the flange portion and the thickness of the carbon fiber reinforced resin layer of the flange portion are set to the entire length and thickness of the blade. Since the value is defined within the appropriate range, optimization of the blade weight can be achieved, and as a result, a lighter blade structure can be obtained while securing bending rigidity and bending fatigue strength. Furthermore, by alternately laminating and integrating the carbon fiber reinforced resin layer and the glass fiber reinforced resin layer of the flange part, the bending strength and bending fatigue life of the blade structure are greatly improved, and a long-life wind turbine blade structure The body is obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a wind turbine blade structure made of fiber-reinforced resin of the present invention.

FIG. 2 is a cross-sectional view of the fiber-reinforced resin wind turbine blade structure of the present invention in a direction perpendicular to a blade longitudinal axis.

FIG. 3 is a partial sectional view of an upper flange portion of FIG. 2;

FIG. 4 is a graph in which the width of the flange portion is plotted on the horizontal axis and the weight of the blade when the thickness of the composite layer of the flange portion is changed is plotted on the vertical axis when the thickness of the blade is constant in the present invention. It is.

[Explanation of symbols]

 1: Blade 2: Longitudinal axis of blade 3: Cross-sectional center of gravity at root of blade 4: Cross-sectional center of gravity at half blade length 5: Front edge 6: Rear edge 7: Upper skin 8: Lower skin 9: Spar 10: Flange part 11: Web part 12: Reinforcement fiber 13: Resin 14: Carbon fiber layer layer 15: Glass fiber layer 16: Carbon fiber layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29C 67/14 U F term (Reference) 3H078 BB12 CC02 4F072 AA07 AB09 AB10 AD08 AD23 AD38 AG03 AH02 AL09 4F205 AA39 AA41 AA43 AG09 AG26 AG27 AH04 HA19 HA33 HA35 HA45 HB01 HC16 HC17 HL13 HL14 HT02 HT26 HW02

Claims (4)

[Claims] 1. A blade for a windmill having a hollow blade-shaped cross section made of fiber-reinforced resin having a horizontal width (W) and a vertical thickness (T) and having a flange portion as a girder member. In the structure, the flange portion has: (A) a width (Wf) within a range of 0.2 to 0.5 (W) in a horizontal direction around a center of gravity of a cross section of the blade; And (C) the composite layer is formed by alternately laminating a pre-carbon fiber reinforced resin layer and a high elongation fiber reinforced resin layer having an elongation in the range of 2 to 6%. Wherein the total thickness (2Tf) is within a range of 10 to 30% of the thickness (T) of the blade. 2. The composite layer has a volume of at least 7
0% or more is a carbon fiber reinforced resin layer oriented in the longitudinal direction of the blade, wherein the thickness of one of the carbon fiber reinforced resin layers is in the range of 1 to 6 mm, and the high elongation fiber reinforced resin layer The wind turbine blade structure made of fiber reinforced resin according to claim 1, wherein the thickness of one layer is in the range of 0.2 to 1.5 mm. 3. The fiber reinforced resin blade structure according to claim 1, wherein the elongation of the matrix resin of the composite layer is 3% or more and less than 10%. 4. The flange portion is a girder member made of a fiber-reinforced resin having a longitudinal section of the blade in a box shape, a C shape, an I shape, or a plate shape, and a longitudinal axis of the blade. 2. The device according to claim 1, wherein the first direction is provided.
The wind turbine blade structure made of a fiber reinforced resin according to any one of claims 1 to 3.