Abstract:
A method and a mold for manufacturing a component for a wind turbine are provided. The method includes the steps of a) laying a fiber material onto a mold, b) attaching the fiber material to the mold and/or to a core of the component using staples, c) infiltrating the fiber material with a resin, and d) curing the resin to form the component. The method may further include wherein the fiber material is attached to a flexible mold part into which the staples are driven. The method may still further include wherein the flexile mold part is made of a polymer material. The method is advantageous in that a lack of consolidation of the component is prevented or reduced.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of European Application No. EP14158527 filed Mar. 10, 2014, incorporated by reference herein in its entirety. 
       FIELD OF INVENTION 
       [0002]    The present invention relates to a method and to a mold for manufacturing a component for a wind turbine. 
       BACKGROUND OF INVENTION 
       [0003]    Modern wind turbine rotor blades are built from fiber-reinforced plastics. A rotor blade typically comprises an airfoil having a rounded leading edge and a sharp trailing edge. To produce such a rotor blade, fiber material is laid onto a mold and subsequently infiltrated with a resin. 
       SUMMARY OF INVENTION 
       [0004]    It is one object of the present invention to provide an improved method and mold for manufacturing a component for a wind turbine. 
         [0005]    Accordingly, a method for manufacturing a component for a wind turbine, in particular a rotor blade, is provided. The method comprises the steps of a) laying a fiber material onto a mold, b) attaching the fiber material to the mold and/or to a core of the component using staples, c) infiltrating the fiber material with a resin, and d) curing the resin to form the component. 
         [0006]    The method is advantageous in that a lack of consolidation of the component, in particular the rotor blade, is prevented or reduced. Due to the fact that the fiber material is attached to the mold, the fiber material is always in contact with a surface of a mold cavity. This prevents a poor consolidation of the resin infiltrated fiber material due to complex mold geometries. In particular, in a section of the mold cavity which constitutes the leading edge of the rotor blade, the staples which attach the fiber material close to the mold prevent the formation of a gap between the fiber material and the mold cavity. Dry fibers, i.e. non-impregnated fibers, air bubbles in the impregnated fiber material and/or accumulations of resin in the leading edge of the rotor blade are therefore avoided or reduced. 
         [0007]    The curing of the resin may be done under pressure and high temperatures, for example in an autoclave. For attaching the fiber material to the mold a staple gun may be used. Examples of a resin which may be used for impregnating the fiber material are epoxy, polyester, vinylester or any other suitable thermoplastic or duroplastic material. The fiber material may comprise glass fibers, carbon fibers, aramid fibers or the like. Preferably the fiber material is made of glass fibers. The fiber material may be provided in the form of woven or knitted mats, as unidirectional fiber mats, rovings or the like. 
         [0008]    The impregnation of the fiber material with resin can be done in a vacuum assisted resin transfer molding (VARTM) process. Alternatively, the fiber material may be supplied in a pre-impregnated state (so-called prepreg material) in step a). Of course, when using a prepreg material, there is no need to inject the fiber material with resin. 
         [0009]    Generally speaking, the mold may be an open or a closed mold. For example, the mold may comprise one or more parts, in particular a lower part and an upper part. 
         [0010]    “Cured” or “set” refers to a resin being hardened and/or cross-linked to an extent where the shape of the fiber material impregnated with the resin will not or not change significantly any more. 
         [0011]    “a)”, “b)”, “c)” and “d)” are not to imply a fixed order of the method steps. Rather, the steps a) to c) may be carried out in a different order where appropriate in the mind of the skilled person. 
         [0012]    According to an embodiment, in step b) the fiber material is attached to a flexible mold part into which the staples are driven. 
         [0013]    Presently, “flexible” means that the material of the flexible mold part may be easily penetrated by the staples. 
         [0014]    According to a further embodiment, the flexible mold part is made of polymer material. 
         [0015]    The flexible mold part is for example made of polystyrene (PS). In particular, the flexible mold part may be made from a foamed polymer to ease the penetration of the staples into the flexible mold part. 
         [0016]    According to a further embodiment, in step a) before laying the fiber material on the mold, the flexible mold part is covered with a foil. 
         [0017]    Preferably, the foil is a polymer foil. The foil acts as a release foil which prevents the resin from sticking to the flexible mold part. The foil is configured removable for an easy replacement thereof. The foil may be made of polytetrafluoroethylene (PTFE), polypropylene (PP), silicone, polyethylene (PE) or the like. 
         [0018]    According to a further embodiment, the component is a rotor blade, wherein in step b) the fiber material corresponding to a leading edge of the rotor blade is attached to the flexible mold part. 
         [0019]    This prevents a lack of consolidation in the leading edge. 
         [0020]    According to a further embodiment, in step b) the fiber material is attached to a lower mold half. 
         [0021]    In particular, the mold includes also an upper mold half in an embodiment. The mold halves are separated in a plane of separation. Additionally, also the upper mold half may be equipped with a flexible mold part. 
         [0022]    According to a further embodiment, after removing the cured component form the mold, portions of the staples that protrude from the component are removed. 
         [0023]    This ensures a smooth surface of the component. 
         [0024]    According to a further embodiment, the portions of the staples that protrude from the component are removed by grinding. 
         [0025]    According to a further embodiment, the staples are made of a polymer material. 
         [0026]    The staples may have a C-shape or pin-shape, for example. In particular, the staples may be made of a glass-fiber reinforced polyamide. 
         [0027]    Further, a mold for manufacturing a component for a wind turbine, in particular a rotor blade, is provided. The mold may be used in the method described above. 
         [0028]    The mold comprises a flexible mold part configured for driving staples into the same, the staples being used to attach a fiber material to the mold. The mold may include a lower mold half and an upper mold half. The mold may be made of a polymer material, a plastic material, a metal alloy or a combination thereof. This ensures sufficient stability and durability of the mold. The mold has a mold cavity which constitutes a negative of the component to be manufactured. The mold cavity may be provided in both mold halves. 
         [0029]    According to an embodiment, the flexible mold part is arranged in a lower mold half of the mold. 
         [0030]    This enables an easy application of the staples before closing the mold with the upper mold half. 
         [0031]    According to a further embodiment, the flexible mold part is configured removable from the mold. 
         [0032]    The flexible mold part may be screwed, glued or clamped to the mold. This has the effect, that the flexible mold part may easily be replaced when it is worn out due to multiple attachment of fiber material to the flexible mold part with staples. 
         [0033]    According to a further embodiment, the flexible mold part is made of a polymer material. 
         [0034]    The flexible mold part is for example made of PS. In particular, the flexible mold part may be made from a foamed polymer to ease the penetration of the staples into the flexible mold part. 
         [0035]    According to a further embodiment, the flexible mold part is arranged adjacent to a plane of separation of the mold. 
         [0036]    This enables an attachment of the fiber material directly at the plane of separation. 
         [0037]    According to a further embodiment, the component is a rotor blade and the flexible mold part is positioned inside the mold so as to correspond to a leading edge of the rotor blade. 
         [0038]    This improves the consolidation in the area of the leading edge of the rotor blade. 
         [0039]    “Wind turbine” presently refers to an apparatus converting the wind&#39;s kinetic energy into rotational energy, which may again be converted to electrical energy by the apparatus. 
         [0040]    The embodiments and features described in relation to the method equally apply to the mold, and vice versa. 
         [0041]    Further possible implementations or alternative solutions of embodiments of the invention also encompass combinations—that are not explicitly mentioned herein—of features described above or below with regard to the embodiments. The person skilled in the art may also add individual or isolated aspects and features to the most basic form of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]    Further embodiments, features and advantages of the present invention will become apparent from the subsequent description and dependent claims, taken in conjunction with the accompanying drawings, in which: 
           [0043]      FIG. 1  shows a perspective view of a wind turbine according to one embodiment; 
           [0044]      FIG. 2  shows a sectional view of a turbine blade according to one embodiment; 
           [0045]      FIG. 3  shows a sectional view of a mold for manufacturing a turbine blade according to one embodiment; 
           [0046]      FIG. 4  shows a perspective view of the mold according to  FIG. 3 ; and 
           [0047]      FIG. 5  shows a flow diagram of a method for manufacturing a turbine blade according to one embodiment. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0048]    In the Figures, like reference numerals designate like or functionally equivalent elements, unless otherwise indicated. 
         [0049]      FIG. 1  shows a wind turbine  1  according to an embodiment. 
         [0050]    The wind turbine  1  includes a rotor  2  connected to a generator (not shown) arranged inside a nacelle  3 . The nacelle  3  is arranged at the upper end of a tower  4  of the wind turbine  1 . 
         [0051]    The rotor  2  includes three blades  5 . Rotors  2  of this kind may have diameters ranging from, for example, 30 to 160 meters. The blades  5  are subjected to high wind loads. At the same time, the blades  5  need to be lightweight. For these reasons, blades  5  in modern wind turbines  1  are manufactured from fiber-reinforced composite materials. Therein, glass fibers are generally preferred over carbon fibers for cost reasons. In addition, the blades  5  each comprise one or more core members made of a light material to reduce the weight of the blades  5 . 
         [0052]      FIG. 2  shows a sectional view of a blade  5  according to an embodiment. 
         [0053]    The blade  5  comprises a shell or airfoil  8  having a rounded leading edge  6  and a sharp trailing edge  7 . The airfoil  8  is made from a fiber-reinforced composite material. The fiber-reinforced material comprises a fiber material and a matrix material in which the fiber material is embedded. The matrix material is a resin. Examples of a resin which may be used for impregnating the fiber material are epoxy, polyester, vinylester or any other suitable thermoplastic or duroplastic material. 
         [0054]    The fiber material may comprise glass fibers, carbon fibers or the like. Preferably, in one embodiment, the fiber material is made of glass fibers. The fiber material may be provided in the form of woven or knitted mats, as unidirectional fiber mats, rovings or the like. The fiber material may be provided in the form of non-impregnated, i.e. dry, mats or in the form of so-called prepregs. Preferably, the fiber material is initially not impregnated with resin and will be impregnated when placed in a mold. The impregnation of the fiber material with resin can be done in a vacuum assisted resin transfer molding (VARTM) process. The airfoil  8  may be hollow or at least filled partly with a core member or core  9 . The core  9  comprises wood or a polymer material, in particular a polymeric foam material. The foam material may comprise polyurethane (PU), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polybutylene terephthalate (TBT) or the like. 
         [0055]      FIG. 3  shows a sectional view, and  FIG. 4  shows a perspective view of a mold  10  for manufacturing a rotor blade  5  according to an embodiment. 
         [0056]    The mold  10  comprises a lower mold half  11  and an upper mold half  12 . The mold halves  11 ,  12  are separated in a plane of separation  13 .  FIG. 3  shows the mold  10  in an open status. When the mold  10  is closed, the mold halves  11 ,  12  are positioned on each other to form a mold cavity  14  which has the shape of the drop-shaped profile of the blade  5 . The mold cavity  14  is constituted by both mold halves  11 ,  12 . In particular, each half  11 ,  12  has a section  15  which corresponds to the leading edge  6  of the blade  5  and a section  16  which corresponds to the trailing edge  7  of the blade  5 . The mold halves  11 ,  12  can be made of metal like aluminum, plastic material, a fiber composite material or a combination thereof. 
         [0057]    The mold  10  comprises a flexible mold part  17  which is configured for driving staples  18  into the same, the staples  18  being used to attach a fiber material  19  to the mold  10 , in particular to the lower mold half  11 . The fiber material  19  may comprise a plurality of fiber mats that are arranged on top of each other. The flexible mold part  17  may be part of the lower mold half  11 . The upper mold half  12  may also comprise a flexible mold part  17 . For attaching the fiber material  19  to the flexible mold part  17  a staple gun may be used. The flexible mold part  17  is preferably made of a plastic material, for example polystyrene (PS). In particular, the flexible mold part  17  is made of a foamed polymer to ease the penetration of the staples  18  into the flexible mold part  17 . Presently, “flexible” means that the material of the flexible mold part  17  may be easily penetrated by the staples  18 . 
         [0058]    The staples  18  are preferably made of a polymer material. The staples are U-shaped or pin-shaped, for example. For example the staples  18  may be made of a glass-fiber reinforced polyamide. The staples  18  may also be uses to attach the fiber material  19  to the core  9  of the blade. 
         [0059]    As can be seen from  FIG. 4 , the flexible mold part  17  is a flat rod which extends in a longitudinal direction of the lower mold half  11 . A plurality of staples  18  is used to attach the fiber material  19  to the flexible mold part  17 . In particular, the flexible mold part  17  is positioned inside the mold  10  so as to correspond to the leading edge  6  of the rotor blade  5 . This means, that the flexible mold part  17  is positioned in the section  15  of the lower mold half  11  and/or the upper mold half  12 . In particular, the flexible mold part  17  is arranged adjacent to the plane of separation  13  of the mold  10 . Alternatively or additionally, the flexible mold part  17  may be positioned at other areas of the mold  10 . In particular, the flexible mold part  17  is positioned in other areas of the mold  10  where the fiber material  19  is laid down on sharp geometries of the mold  10 . This is to ensure that the fiber material  19  always is in contact with a surface of the mold cavity  14 . 
         [0060]    The flexible mold part  17  is preferably removable from the mold  10 . The flexible mold part  17  can be screwed, glued or clamped to the mold  10 . This has the effect, that the flexible mold part  17  may easily be replaced when it is worn out due to multiple attachment of fiber material  19  to the flexible mold part  17  with staples  18 . 
         [0061]    Between the fiber material  19  and the flexible mold part  17  is provided a release foil  20  which prevents the resin from sticking to the flexible mold part  17 . The foil  20  is removable for an easy replacement. The foil  20  may be made of a polymer, for example polytetrafluoroethylene (PTFE), polypropylene (PP), silicone, polyethylene (PE) or the like. 
         [0062]      FIG. 5  shows a flow diagram of a method for manufacturing a component, in particular a rotor blade  5 , according to an embodiment. 
         [0063]    In step S 1 , the fiber material  19  is laid onto the mold  10 . In particular, the fiber material  19  is laid onto the lower mold half  11 . Before laying the fiber material  19  on the mold  10 , the flexible mold part  17  is covered with a foil  20 , also referred to as a release foil. The foil  20  is configured to be easily removable from the mold  10  to enable replacement thereof. The foil  20  prevents the fiber material  19  from sticking to the flexible mold part  17  after impregnating the fiber material with a resin. 
         [0064]    Subsequently, in step S 2  the fiber material  19  is attached to the mold  10 , in particular to the flexible mold part  17  of the lower mold half  11 , using staples  18 . The staples  18  are driven into the flexible mold part  17 . In step S 2 , the fiber material  19  corresponding to the leading edge  6  of the rotor blade  5  is attached to the flexible mold part  17 . Additionally or as an alternative to attaching the fiber material  19  to the flexible mold part  17 , the fiber material  19  may be attached to the core  9  of the component using staples  18 . In this case, the core  9  may comprise a flexible material, e.g. polymeric foam or any other flexible material as described herein. 
         [0065]    It is to be noted that the core  9  is optional. The core  9  may be placed on the fiber material  19  that is applied to the lower mold half  11 . The core  9  is subsequently covered with the fiber material  19  to enclose the core  9  in the fiber material  19 . The mold  10  is closed when the fiber material  19  and the core  9  are placed in the mold  10 . 
         [0066]    In step S 3 , the fiber material  19  is impregnated with a resin. This may be done in a VARTM process. This process may involve using a vacuum bag as well as a suction pump which are not shown in the figures. 
         [0067]    After impregnating the fiber material  19  with resin, the resin is cured to form the component of the wind turbine  1 , i.e. the blade  5 , in step S 4 . The impregnated fiber material  19  may be cured, e.g. in an autoclave, by adding pressure and/or heat. 
         [0068]    Subsequently, in step S 5 , the blade  5  is removed from the mold. 
         [0069]    After step S 5 , portions  21  (see  FIG. 2 ) of the staples  18  that protrude from the blade  5  are removed in a step S 6 . This can be done by grinding. 
         [0070]    The mold  10  and the method are advantageous in that due to the fact that the fiber material  19  is attached to the mold  10 , the fiber material  19  is always in contact with a surface of the mold cavity  14 . This prevents a poor consolidation of the resin infiltrated fiber material  19  due to complex mold geometries. In particular, in the section  15  of the mold cavity  14  which constitutes the leading edge  6  of the blade  5  and which is separated by the plane of separation  13 , the staples  18  which attach the fiber material  19  close to the mold  10  prevent the existence of a gap between the fiber material  19  and the mold cavity  14 . Thus, a lack of consolidation of the resin impregnated fiber material  19  is avoided. This means, dry fibers, i.e. non-impregnated fibers, air bubbles in the impregnated fiber material  19  and/or accumulation of resin in the leading edge  6  of the blade is prevented. 
         [0071]    Although the present invention has been described in accordance with preferred embodiments, it is obvious for the person skilled in the art that modifications are possible in all embodiments.