CN102814996B - Preparation method of hybrid composite spar for large wind turbine blades - Google Patents

Abstract

The invention discloses a preparing method of a hybrid composite wing spar of a large-scale wind power blade. The preparing method comprises the following steps of firstly, preprocessing a die; then, paving and covering distribution medium, demolding cloth, a perforated isolating membrane, an enhancing material performing body, the perforated isolating membrane and the demolding cloth on the surface of the die from bottom to top; paving a first ventilated felt which is provided with multiple semi-permeable ventilating connectors; forming a first layer closing die cavity by covering a first flexible vacuum bag membrane and a flexible semi-permeable membrane on the surface of the die by a sealing tape after connecting the first flexible vacuum bag membrane and the flexible semi-permeable membrane into a whole, completely sealing and coating the first flexible vacuum bag membrane and the flexible semi-permeable membrane by using a second flexible vacuum bag membrane, and forming a second layer closing die cavity; connecting the semi-permeable ventilating connectors to a vacuum pumping system and an glue injection system for injecting glue, and controlling a flow direction of matrix resin so as to realize the complete dipping in glue injection; and finally, obtaining a wing spar through solidifying, demolding and reconditioning. The preparing method disclosed by the invention has the advantages that the cost is low, the quality is stable, the technology efficiency is high, the product quality is good, and the like.

Description

Preparation method of hybrid composite spar for large wind turbine blades

technical field

The invention belongs to the technical field of manufacturing and processing of wind power generation equipment, and in particular relates to a preparation method of a wind power generation blade spar made of special materials.

Background technique

The typical structure of a large wind turbine blade consists of two aerodynamic skins made of fiber-reinforced polymer and a shear web connecting the two aerodynamic skins. The connection between the two aerodynamic shells and between the aerodynamic shell and the shear web is made by bonding. A typical method for preparing the blade aerodynamic skin and shear web is the vacuum infusion process. When the vacuum infusion process is used to prepare the aerodynamic shell of the blade, reinforcement materials such as fibers and fiber fabrics, and sandwich materials such as foam and balsa wood are laid in the forming mold according to the layup design and covered with a vacuum bag. By creating a vacuum in the cavity between the inner surface of the forming mold and the vacuum bag, the resin is drawn in and fills the cavity containing the fibrous material. Typical polymers used are mainly polyester or epoxy resins, and typical fiber materials used are mainly fiber fabrics of different shapes. Reinforcement fibers are often based on glass fibers, and carbon fibers, as a high-performance fiber, have also begun to be used in large-scale composite wind turbine blades. The rigidity of carbon fiber is greater than that of glass fiber, and the addition of carbon fiber can obtain higher rigidity and lighter weight. However, since carbon fiber is much more expensive than glass fiber, this shortcoming limits the widespread use of carbon fiber in large composite wind turbine blades.

The main component of the aerodynamic shell is the spar, which is the main load-bearing part of large composite wind turbine blades, and is a typical large-scale, thick-section fiber-reinforced resin-based plywood (thick-section composite plywood) component. Various implementations of wind turbine blades made of hybrid fiber reinforced composite materials have been proposed in the prior art, but the increase in blade cost due to the increase of carbon fibers makes it difficult to bear and promote in the existing market. In addition, the output power of wind turbines is easily affected by the external natural environment such as wind speed. For wind turbines with rated power, how to reduce the impact of the external environment and maximize the output power is an important issue facing the development of wind turbines. According to the principle that the output power of the fan is proportional to the square of the diameter of the wind rotor, the influence of external conditions can be eliminated by lengthening the length of the rated power blades, and the output power of the wind turbine can be increased. However, increasing the length of the blade will bring the following problems: 1) The mass of the blade will increase according to the cube of the length, which will seriously affect the operation and fatigue life of the fan; 3) After lengthening the blade length, the blade tip deflection increases under extreme wind load, and there is a risk of collision tower damage.

In the present invention, the hybrid composite material spar of the blade is distinguished and independently defined for the first time. The hybrid composite material spar refers to the glass fiber/carbon fiber hybrid reinforced thick section composite material blade spar, which is typically used in elongated composite material wind power blades. There are at least two difficulties in the preparation of hybrid composite spars: on the one hand, the blade spars are large-scale, thick-section composite laminates, and the length of large wind power blade spars has increased from more than 20 meters to More than 60 meters, the difficulty in forming thick-section composite members is that the permeability in the thickness direction is low and the resin is difficult to completely impregnate, so it is difficult to ensure that the resin is uniformly impregnated with fiber reinforced materials in the entire size range; on the other hand, compared with glass fiber , the carbon fiber diameter is small, the fiber gap is small, the total surface area of the fiber is large under the same volume, carbon fiber is more difficult to impregnate evenly than glass fiber, and the hybrid composite spar has both glass fiber thick section laminates and carbon fiber thick section laminates, There are also carbon fiber/glass fiber mixed thick-section laminates. The flow impregnation speed of resin on different fiber sections is different, which may easily lead to uneven impregnation and defects such as lack of glue. The process control is difficult and the product quality stability is poor.

At present, the most common low-cost method for forming large-scale composite wind power blade spars can also use vacuum infusion technology, but the traditional vacuum infusion process is only suitable for forming pure glass fiber reinforced thick-section blade spars, and the vacuum infusion process is used to form the above-mentioned Hybrid composite spars often only ensure adequate resin impregnation of the fiberglass reinforcement, but not the complete impregnation of the entire component. Therefore, the current method of molding and preparing hybrid composite spars mostly adopts the prepreg molding method, but the prepreg molding method is a multi-step molding method, and the prepreg needs to be stored in a special environment, and the cost is high. requirements are also higher.

In order to meet the needs of large-scale blades and high output power, how to effectively solve the problem of low-cost molding of hybrid composite material spars is the key to the successful application of carbon fiber in composite wind power blades, and it is also the key to the development of lengthened and large-scale composite wind power blades. In order to solve the problems, it will be of great practical significance to develop and develop the preparation and molding process scheme of the hybrid composite spar.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, and to provide a method for preparing a large-scale wind power blade hybrid composite spar with low cost, stable and uniform quality, one-step integral molding, high process efficiency, and good product quality. After the spar prepared by the preparation method is applied to large wind power blades, the length of the wind power blades can be increased and the output power can be improved under the premise of controlling the cost and ensuring the quality of the wind power blades.

In order to solve the above technical problems, the technical solution proposed by the present invention is a method for preparing a large-scale wind power blade hybrid composite spar. The spar skin layer, the spar sandwich layer mainly consists of a glass fiber sandwich layer near the blade root, a carbon fiber sandwich layer near the blade tip, and a transition zone connecting the glass fiber sandwich layer and the carbon fiber sandwich layer Partial composition, the preparation method of described spar mainly comprises the following steps:

(1) Mold pretreatment: first clean the mold, spray release agent and gel coat;

(2) Cladding material: according to the design requirements of the spar, the required reinforcing material preform and forming auxiliary material are cut out. The reinforcing material preform is made of spar skin layer reinforcement (including upper skin layer reinforcement lower skin layer reinforcements, and both are made of glass fiber fabrics) and spar sandwich layer reinforcements, the spar sandwich layer reinforcements include glass fiber fabrics near the blade root, carbon fiber fabrics near the blade tip, and connecting glass fibers Composed of mixed fiber fabrics of fabric and carbon fiber fabric, forming auxiliary materials include diversion medium, release cloth, perforated isolation film, air felt and vacuum bag film, on the surface of the mold after pretreatment in step (1) from bottom to top Lay diversion medium, release cloth, perforated isolation film, reinforcing material preform, perforated isolation film and release cloth in sequence; An air felt, the first air felt is provided with a plurality of semi-permeable air joints at intervals along the length direction of the spar;

(3) Set the first layer of closed mold cavity: the projection of the boundary line between the glass fiber sandwich layer and the transition zone on the horizontal plane is used as the dividing line, and the side of the dividing line close to the glass fiber sandwich layer uses the first The mold is covered with a flexible vacuum bag film, and the side of the boundary line close to the transition zone is covered with a flexible semi-permeable film. The first flexible vacuum bag film and the flexible semi-permeable film are connected as a whole at the boundary line and then covered with a sealing tape on the mold A first layer of closed mold cavity is formed on the surface, and the reinforcing material preform and molding auxiliary material are wrapped in the first layer of closed mold cavity;

(4) Set the second layer of closed mold cavity: Lay the second air felt above the flexible semi-permeable membrane, and set a plurality of air joints at intervals along the length direction of the spar on the second air felt; then use the second The flexible vacuum bag film covers the surface of the mold and completely seals and covers the first flexible vacuum bag film and the flexible semi-permeable film to form a second layer of closed mold cavity, so that the second air felt and the ventilation joint are in the second layer of closed mold cavity middle;

(5) Connect external equipment: connect all semi-permeable ventilation joints and ventilation joints to the vacuum system, and connect the injection system to the injection port located in the first layer of closed mold cavity;

(6) Vacuum glue injection: close the glue injection system, then open all the semi-permeable ventilation joints and ventilation joints, and exhaust the gas in the first layer of closed mold cavity and the second layer of closed mold cavity through the vacuum system, so that the first layer The first-layer closed mold cavity and the second-layer closed mold cavity reach a vacuum negative pressure and can maintain it stably, and then open the injection system to start injecting matrix resin to impregnate the reinforcing material preform in the first-layer closed mold cavity. The injection process Close the semi-permeable ventilation joint and the ventilation joint successively in order to control the flow direction of the matrix resin to realize the complete impregnation of the matrix resin to the reinforcing material preform;

(7) Curing molding and post-processing: After the vacuum injection is completed, the curing molding starts. During the curing molding process, the vacuum degree in the mold cavity is maintained until the curing is complete. After the curing is completed, demoulding, trimming and cleaning are performed to obtain a large-scale overall molding. Hybrid composite spars for wind turbine blades.

In the preparation method of the above-mentioned large-scale wind power blade hybrid composite spar, the flexible semi-permeable membrane is preferably a film material that can pass through the gas but not pass through the matrix resin glue (the film material is generally a two-layer structure, which belongs to this Those skilled in the art can commercially purchase and routinely select products).

In the above method for preparing a hybrid composite spar of a large wind power blade, the semi-permeable ventilation joint is preferably a ventilation joint through which the gas can pass but the matrix resin glue cannot pass through. The structure of the semi-permeable ventilation joint preferably includes a rigid shell, the bottom of the rigid shell is covered by a flow-guiding medium, an airflow channel is provided in the shell, and a filling body is provided at the bottom area of the airflow channel, and the filling body is mainly arranged from bottom to top. The semi-permeable membrane, the diversion medium, the semi-permeable membrane, the air felt and the diversion medium are sequentially stacked; the filling body is sealed and connected with the inner wall of the rigid shell; the air flow channel above the filling body is provided with a valve.

In the above method for preparing a hybrid composite spar of a large wind power blade, the ventilation joint is preferably a ventilation joint through which both gas and matrix resin glue can permeate. The structure of the ventilation joint preferably includes a rigid shell, the bottom of the rigid shell is covered by a flow-guiding medium, an air flow channel is provided in the shell, and a filling body is provided at the bottom area of the air flow channel, and the filling body is mainly stacked from bottom to top. It is composed of diversion medium, air felt and diversion medium; the filling body is sealed and connected with the inner wall of the rigid shell; the air flow channel above the filling body is provided with a valve.

In the above method for preparing a large-scale wind power blade hybrid composite spar, the spacing of the semi-permeable ventilation joints along the length direction of the spar is preferably 2 m to 3 m. The distance between the ventilation joints along the length direction of the spar is preferably 1m-2m.

In the method for preparing a hybrid composite spar of a large wind power blade mentioned above, in the vacuum injection step, successively closing the semi-permeable ventilation joint and the ventilation joint specifically refers to: from the end set as the blade root in the mold to the end set as the blade tip Close all semi-permeable vent joints and vent joints one by one. The closing time interval of each semipermeable ventilation joint is preferably 1 min to 2 min, and the closing time interval of each ventilation joint is preferably 2 min to 3 min.

In the preparation method of the above-mentioned large-scale wind power blade hybrid composite spar, the reinforcing material in the transition zone is a hybrid fiber fabric, and its arrangement in the reinforcing material preform is preferably: from the glass fiber fabric to the carbon fiber fabric Gradual transition from all glass fiber reinforced to all carbon fiber reinforced in the direction of . The gradual transition specifically refers to any of the following transition methods:

(1) The glass fiber fabric forms a transition tip in the transition zone and is wedged into the V-shaped groove formed in the carbon fiber fabric in the transition zone; or,

(2) The carbon fiber fabric forms a transition tip in the transition zone and is wedged into the V-shaped groove formed by the glass fiber fabric in the transition zone.

In the method for preparing a hybrid composite spar of a large-scale wind power blade, the glass fiber fabric and the carbon fiber fabric in the transition zone may also be transitioned and handed over by interlayer weaving. The weaving method in the layer refers to: the end of the glass fiber fabric and the end of the carbon fiber fabric in the transition zone are mixed and alternately woven in the layer, so that the glass fiber and carbon fiber sandwiched between the glass fiber sandwich layer extending into the transition zone The carbon fibers in the core layer extending into the transition zone are joined together.

In the preparation method of the above-mentioned large-scale wind power blade hybrid composite spar, the glass fiber fabric and the carbon fiber fabric in the transition zone are preferably transitioned and handed over by interlayer stitching, so that the glass fiber sandwich layer extending into the transition zone The fiber fabric is fixedly superimposed on the carbon fiber fabric extending into the transition zone in the carbon fiber sandwich layer. The suture thread used for the interlayer suture is preferably one or more of aramid fiber yarn, quartz fiber yarn and glass fiber yarn.

In the preparation method of the above-mentioned large-scale wind power blade hybrid composite spar, the thickness of the skin layer of the spar is preferably 2 mm to 3 mm, and the reinforcing material used for the skin layer of the spar is preferably glass fiber uniaxial cloth or glass fiber biaxial cloth. and/or fiberglass triaxial cloth. The glass fiber fabric in the spar sandwich layer is preferably a uniaxial fabric with an areal density above 1000 g/m ² , and the carbon fiber fabric in the spar sandwich layer is preferably a uniaxial fabric with an areal density above 600 g/m ² Uniaxial fabric.

Compared with the prior art, the present invention has the following advantages: firstly, the present invention adopts a vacuum glue injection system composed of vacuum bag film, semi-permeable membrane, semi-permeable ventilation joint and ventilation joint, which can effectively control the flow direction of resin liquid , which provides a simple and effective method for resin flow control in the liquid molding process of composite materials; secondly, through the resin liquid flow control method of the present invention, it can realize low-permeability multi-layer fiber fabric preforms (such as thick cross-section pure carbon fiber spar) and variable permeability multi-layer fiber fabric preform (such as thick cross-section hybrid fiber reinforced spar), which is a one-step integral molding of low permeability or variable permeability large-scale composite structural parts Provide effective methods. In addition, the preparation method of the invention is not only easy to operate, good in environmental protection, but also low in cost.

After the preparation method of the present invention is applied to the preparation of large-scale wind power blades, on the one hand, the production cost of applying carbon fiber is reduced, which is in line with the affordability of the current market; performance, prolonging the service life of the blades. In general, the lengthenable large-scale composite wind turbine blade prepared by the preparation method of the present invention can be rated at The blade length of the power is increased by 5% to 20%, and the same power (rated power) and the same airfoil (aerodynamic airfoil) can be maintained; according to the principle that the output power of the fan is proportional to the square of the diameter of the wind wheel, the wind turbine can be The output power is increased by 10% to 20%. Under a specific stiffness, the technical solution of the present invention can also reduce the static load of the wind turbine blade, and simultaneously reduce the dynamic load of the blade aerodynamic shell and the blade root; by changing and adjusting the content and distribution of carbon fibers in the transition zone and the outer end, The stiffness and natural frequency of the blade can be changed accordingly, so that the stiffness and natural frequency are optimal under specific conditions, which greatly improves the applicability, flexibility and operability of the blade of the present invention. It can be seen that the large-scale wind power blade prepared by the present invention has a good market application prospect.

Description of drawings

Fig. 1 is a schematic structural diagram of a wind turbine blade in an embodiment of the present invention.

Fig. 2 is an enlarged cross-sectional view at A-A in Fig. 1 .

Fig. 3 is a schematic diagram of the interval distribution of the spar sandwich layer in the blade length direction in the embodiment of the present invention.

Fig. 4 is a structural schematic diagram of a gradual transition mode 1 in the transition zone of the spar sandwich layer in the embodiment of the present invention.

Fig. 5 is a structural schematic diagram of the second gradual transition mode in the transition zone of the spar sandwich layer in the embodiment of the present invention.

Fig. 6 is a schematic diagram of the principle of using the intra-layer weaving method in the embodiment of the present invention.

Fig. 7 is a schematic diagram of the principle of interlayer stitching in the embodiment of the present invention.

Fig. 8 is a schematic diagram of the structure of the blade gradual transition mode combined with interlayer stitching mode to realize the transition connection in the embodiment of the present invention.

Fig. 9 is a structural schematic diagram of transitional connection realized by blade gradual transition mode 2 combined with interlayer suture mode in the embodiment of the present invention.

Fig. 10 is a distribution diagram of the position of the blade transition zone on the blade in the embodiment of the present invention.

Fig. 11 is a schematic diagram of the blade preparation method in the embodiment of the present invention.

Fig. 12 is a schematic structural diagram of a semi-permeable ventilation joint in an embodiment of the present invention.

Fig. 13 is a schematic structural diagram of the ventilation joint in the embodiment of the present invention.

illustration:

1. Aerodynamic shell; 11. Skin layer; 12. Filling body; 2. Shear web; 3. Wing spar; 31. Wing spar sandwich layer; 311. Glass fiber sandwich layer; 312. Transition zone; 313. Carbon fiber sandwich layer; 32, spar skin layer; 33, reinforcing material preform; 331, glass fiber fabric; 332, hybrid fiber fabric; 333, carbon fiber fabric; 334, spar skin layer reinforcement material; 34, diversion Medium; 35. Release cloth; 36. Isolation film with holes; 37. The first air felt; 371. The second air felt; 38. The first flexible vacuum bag film; 381. The flexible semi-permeable membrane; 382. The second flexible Vacuum bag film; 39. Sealing tape; 4. Glass fiber; 5. Carbon fiber; 6. Mold; 61. Semi-permeable vent joint; 62. Vent joint; 63. Rigid shell; 64. Semi-permeable membrane; 65. Air felt ; 66, valve; 7, vacuum system; 71, vacuum pump; 8, injection system; 81, injection port; 82, resin bucket.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example:

A large-scale composite wind turbine blade that can be lengthened as shown in Figure 1 and Figure 2. The overall shape of the blade is shown in Figure 1, and it can be seen from Figure 2 that the blade includes an aerodynamic shell 1 and an inner cavity of the aerodynamic shell 1 The shear web 2 in the aerodynamic shell 1 is mainly composed of the upper and lower spars 3 in the middle and the fillers 12 on both sides of the spar 3 (the fillers in this embodiment are the density provided by Mead China Composite Materials Co., Ltd. PVC foam with a density of 63.0±6 kg/m ³ and Balsa wood with a density of 150±20 kg/m ³ ), the aerodynamic shell 1 is covered with a skin layer 11 , and the upper and lower spars 3 pass through the shear web 2 connect.

The spar 3 in the present embodiment comprises a spar sandwich layer 31 and a spar skin layer 32 coated on the outside of the spar sandwich layer 31, as shown in Figure 3, the spar sandwich layer 31 is mainly composed of The glass fiber sandwich layer 311, the carbon fiber sandwich layer 313 near the tip of the blade, and the transition zone 312 connecting the glass fiber sandwich layer 311 and the carbon fiber sandwich layer 313 are composed of three parts. The glass fiber sandwich layer 311 is mainly composed of glass fiber Made of reinforced polymer (GFRP, Glass Fiber Reinforced Polymer), the carbon fiber sandwich layer 313 is mainly made of carbon fiber reinforced polymer (CFRP, Carbon Fiber Reinforced Polymer), and the transition zone 312 is mainly made of glass-carbon hybrid fiber reinforced polymer As a result, the specific arrangement of the glass-carbon hybrid fibers in the transition zone 312 is as follows: from the glass fiber sandwich layer 311 to the carbon fiber sandwich layer 313, there is a gradual transition from all glass fiber reinforcement to all carbon fiber reinforcement. Since carbon fibers are generally 3 to 4 times harder than glass fibers, the stress concentration in the transition zone 312 tends to easily cause the risk of damage to the entire blade. By using the transition zone designed by the present invention, it is possible to avoid the transition zone where the stiffness of the blade is between the glass fiber and the carbon fiber. A sudden change occurs in the middle, thereby avoiding stress concentration at the boundary surface between carbon fiber and glass fiber when it is subjected to large dynamic or static stress.

As shown in Figure 10, in the wind power blade of this embodiment, the length of the glass fiber sandwich layer 311 is 50% of the length L of the entire spar 3 (45% to 55% is acceptable, the length L of the spar in this embodiment 55m); the length of the transition zone 312 is 20% of the length L of the entire spar 3 (15% to 25% is acceptable); the length of the carbon fiber sandwich layer 313 is 30% of the length of the entire spar 3 (25% to 35% % can be used). Wherein, the position of the transition zone 312 is arranged in an area of 3 l /2 to 5 l /2 from the root of the blade, where l is the distance from the root of the blade to the center of gravity of the blade. The length ratio of each component in the spar sandwich layer 31 and the position distribution relationship of each part in the whole spar 3 are important improvements and optimizations made by us through repeated tests. Under such optimal conditions, it is not only beneficial to Improve overall blade strength and performance while minimizing cost.

Figure 11 shows the one-step integral molding method of the above-mentioned large-scale wind turbine blade hybrid fiber reinforced spar in this embodiment, which specifically includes the following steps:

(1) Mold pretreatment: firstly clean the mold, repair and smooth it, then spray the mold release agent, and then spray the gel coat.

(2) Overlay material: According to the design requirements in this embodiment, the reinforcing material preform 33 and forming auxiliary materials required for the spar 3 are cut; the reinforcing material preform 33 is composed of the spar skin layer reinforcing material 334 and wing The reinforced material of the beam sandwich layer consists of a glass fiber fabric 331 near the root of the blade (this embodiment uses a glass fiber uniaxially woven fabric with an area density of 1200g/m ² ), and a fiberglass fabric 331 near the tip of the blade. Carbon fiber fabric 333 (this embodiment selects carbon fiber uniaxially woven cloth with an area density of 600g/m ² ) and hybrid fiber fabric 332 connecting glass fiber fabric 331 and carbon fiber fabric 333; forming auxiliary materials include flow guide medium 34 (ie flow guide net), release cloth 35 ((R85PA66 release cloth produced by Shanghai Lek Technology Co., Ltd., surface density is 85g/m ² )), perforated isolation film 36, air felt (including the first air felt and the second air felt) and vacuum bag film (the vacuum bag film of this embodiment is the Vacfilm400Y26100 type vacuum bag film produced by French Aerorac company, including the first flexible vacuum bag film and the second flexible vacuum bag film); The surface of the treated mold 6 is sequentially covered with diversion medium 34, release cloth 35, perforated isolation film 36, reinforcing material preform 33, perforated isolation film 36 and release cloth 35 from bottom to top, wherein the reinforcing material The preform 33 is sequentially composed of the lower skin layer reinforcement material, the spar sandwich layer reinforcement material and the upper skin layer reinforcement material from bottom to top, and then lay on the corresponding release cloth 35 above the area where the glass fiber sandwich layer 311 is located. The first air felt 37 is placed, and a plurality of semi-permeable ventilation joints 61 are arranged at intervals along the length direction of the spar 3 on the first air felt 37 (with a distance of 2m to 3m).

(3) Set the first layer of closed mold cavity: take the projection of the boundary line between the glass fiber sandwich layer 311 and the transition zone 312 on the horizontal plane as the dividing line, and use the first flexible mold on the side of the dividing line close to the glass fiber sandwich layer 311 The vacuum bag film 38 covers the mold 6, and the side of the boundary near the transition zone 312 uses a flexible semi-permeable film 381 to cover the mold (the semi-permeable film in this embodiment is the QL836 semi-permeable film provided by Shanghai Lek Technology Co., Ltd., the thickness 0.35mm), the first flexible vacuum bag membrane 38 and the flexible semi-permeable membrane 381 are bonded at the joint with a sealing tape 39 to form a whole hybrid membrane that completely covers the spar reinforcement area, and then covered on the surface of the mold 6 by the sealing tape 39 A first-layer closed mold cavity is formed, and the reinforcing material preform 33 and the molding auxiliary material are both wrapped in the first-layer closed mold cavity. In this embodiment, the first flexible vacuum bag membrane 38 is a thin film material that is impermeable to both liquid and gas, while the flexible semipermeable membrane 381 is a thin film material that gas can pass through but liquid cannot pass through; the first flexible vacuum bag membrane 38 can make the matrix resin glue flow along the glass fiber sandwich layer 311 to the transition zone 312 and the carbon fiber sandwich layer 313, while the flexible semi-permeable membrane 381 guides the matrix resin glue to flow along the thickness direction and uniformly impregnate the preformed reinforcing material Body 33, avoiding the formation of defects; therefore, by using the first flexible vacuum bag film 38 and the flexible semi-permeable film 381 in combination, the resin can be guided to flow in the designed direction.

(4) Set the second layer of closed mold cavity: Lay the second air felt 371 above the flexible semi-permeable membrane 381, and set multiple air vents on the second air felt 371 at intervals along the length direction of the spar 3 (with a distance of 1m to 2m). Joint 62; then cover the mold 6 surface with the second flexible vacuum bag film 382 and use sealing tape 39 to completely seal and coat the first flexible vacuum bag film 38 and the flexible semi-permeable film 381 to form the second layer of closed mold cavity, so that The second air felt 371 and the air joint 62 are in the second layer closed mold cavity.

(5) Connect external equipment: connect all semi-permeable ventilation joints 61 and ventilation joints 62 to the vacuum system 7 (connected to the vacuum pump 71 by the vacuum pipeline), and connect the glue injection system 8 (connected to the vacuum pump by the glue injection pipeline) The resin barrel 82) is connected to the injection port 81 located in the closed mold cavity of the first layer. The matrix resin used for injection of spar 3 is generally epoxy resin system, which can well meet the interface performance requirements of glass fiber 4 and carbon fiber 5 .

(6) Vacuum glue injection: close the glue injection system 8, then open all the semi-permeable vent joints 61 and vent joints 62, and exhaust the gas in the first closed mold cavity and the second closed mold cavity through the vacuum system 7 , so that the vacuum negative pressure (0.098MPa) in the first layer of closed mold cavity and the second layer of closed mold cavity can be maintained stably for 20min~30min, then open the injection system 8 and start injecting matrix resin to impregnate the first layer of closed mold For the reinforcing material preform 33 in the cavity, the semi-permeable ventilation joint 61 and the ventilation joint 62 are successively closed during the glue injection process to control the flow direction of the matrix resin to realize the complete impregnation of the matrix resin to the reinforcement material preform; The permeable ventilation joint 61 and the ventilation joint 62 specifically refer to: from the end set as the blade root in the mold 6 to the end set as the blade tip, close all the semi-permeable ventilation joints 61 and 62 one by one, each semi-permeable The closing time interval of the ventilation joint 61 is 1 min to 2 min, and the closing time interval of each ventilation joint 62 is 2 min to 3 min.

(7) Curing molding and post-processing: After the vacuum injection is completed, the curing molding starts. During the curing molding process, the vacuum in the mold cavity is maintained until the curing is complete. After the curing is completed, demoulding, trimming and cleaning are performed to obtain the mold of this embodiment. Hybrid composite spars for large wind turbine blades3. Adopting the molding method of the above-mentioned spar 3 can not only realize the overall continuity of the spar 3 structure, but also facilitate the resin polymer to fully impregnate the reinforcing fibers during the vacuum infusion process of the spar 3, and the upper and lower surfaces of the spar 3 cover the entire length. The number of continuous fiber layers can be selected according to specific design requirements (3 layers in this embodiment).

In the above preparation method of this embodiment, the gradual transition of the hybrid fiber fabric 332 located in the transition zone 312 is realized in the following two ways:

As shown in Figure 4, the glass fiber sandwich layer 311 forms a transition tip in the transition zone 312 and is wedged into the V-shaped groove formed in the carbon fiber sandwich layer 313 in the transition zone 312; or as shown in Figure 5, the carbon fiber The sandwich layer 313 forms a transition tip in the transition region 312 and is wedged into the V-shaped groove formed by the glass fiber sandwich layer 311 in the transition region 312 .

Since the spar 3 is the main load-bearing part of the blade, the continuity of the reinforcing fibers is the key to maintaining the overall performance of the spar 3 and thus the overall performance of the blade. The glass fiber 4 and the carbon fiber 5 in the transition zone 312 of the blade in this embodiment can be transitioned and handed over through the intra-layer braiding method as shown in FIG. 6 or through the inter-layer stitching method as shown in FIG. 7 . In this embodiment, interlayer stitching is used to realize the connectivity of reinforcing fibers. After the interlayer stitching connection is applied to the above-mentioned two kinds of gradual transition areas in this embodiment, the effects are shown in Fig. 8 and Fig. 9 respectively. The stitching thread used for interlayer stitching is aramid fiber yarn, quartz fiber yarn or glass fiber yarn. In the transition zone 312, the length of the transition zone between the glass fiber fabric and the carbon fiber fabric on the same layer generally ranges from 0.6m to 1.4m.

In the manufacturing method of the above-mentioned hybrid composite spar in this embodiment, the flexible semipermeable membrane 381 is a thin film material that can pass through the gas but impermeable to the matrix resin glue. The semi-permeable ventilation joint 61 is a ventilation joint through which the gas can pass but the matrix resin glue cannot pass through. Its structure is as shown in Figure 12, including a rigid shell 63, the bottom of which is formed by a flow-guiding medium 34 (i.e. flow net), the shell is provided with an airflow channel, and the bottom area of the airflow channel is provided with a filling body. The filling body is mainly composed of a semi-permeable membrane 64, a flow-guiding medium 34, a semi-permeable membrane 64, and a breathable The felt 65 and the flow guide medium 34 are composed; the filling body and the inner wall of the rigid shell 63 are connected by a sealing tape 39; a valve 66 is arranged in the air flow channel above the filling body. The ventilation joint 62 is a ventilation joint through which both gas and matrix resin glue can permeate. Its structure is shown in Figure 13. The structure of the ventilation joint 62 includes a rigid shell 63. There is an air flow channel inside, and the bottom area of the air flow channel is provided with a filling body. The filling body is mainly composed of flow guide medium 34, air felt 65 and flow guide medium 34 stacked in sequence from bottom to top; the filling body and the inner wall of the rigid shell 63 There is a sealed connection between them; a valve 66 is arranged in the air flow channel above the filling body.

In the above-mentioned wind power blade spar 3 of this embodiment, the thickness of the spar skin layer 32 is 3 mm (2 mm to 3 mm is acceptable), and the reinforcing material used for the spar skin layer 32 is glass fiber uniaxial cloth, glass fiber biaxial cloth, etc. Cloth or glass fiber triaxial cloth (the reinforcing materials used in this example are uniaxial cloth with a surface density of 1250g/ ^m2 , ±45° braided biaxial cloth with a surface density of 808g/ ^m2 provided by Chongqing International Composite Materials Co. Axial fabric and 0°, ±45° braided triaxial fabric with a surface density of 1215g/ ^m2 ). Since the periphery of the spar 3 is covered with a spar skin layer along the entire length of the blade, the spar skin layer is a continuous glass fiber layer as a surface reinforcement, so the significance of the layer design has at least three aspects: 1) This is a way to further achieve the overall continuity of the spar structure; 2) it is beneficial for the resin polymer to fully impregnate the reinforcing fibers (especially carbon fibers) during the vacuum infusion process of the spar; 3) it is beneficial for the connection between the spar and the aerodynamic shell transitions between layers.

In the wind power blade spar finally obtained in this embodiment, the glass fiber sandwich layer 311 near the blade root of the blade spar 3 is made of GFRP, and the carbon fiber sandwich layer 313 near the blade tip is made of CFRP. The specific strength (strength/density) of reinforced polymer laminates is about 2 times that of glass fiber reinforced polymer laminates, and the specific modulus (modulus/density) is about 3 times that of GFRP. As a reinforcing material, it can not only give full play to the advantages of high elasticity and light weight of carbon fiber, greatly improve the stiffness and strength of the blade tip, and increase the critical length of the blade (see Table 1), but also the price is lower than that of using carbon fiber as a reinforcing material to prepare blades or blades. The use of carbon fiber as a reinforcing material to prepare all the spars 3 will be greatly reduced, which is more conducive to the promotion and application of carbon fiber in the field of wind power blades; at the same time, it can effectively reduce the deflection of the blade tip and prevent the blade tip from touching the tower during blade operation; and It can achieve the comprehensive goal of lengthening the blade and increasing the output power without increasing the weight of the blade, moving the center of gravity outward, and changing the natural frequency of the blade.

Table 1: Comparison of technical parameters between the blade of this embodiment and the existing blade

blade existing blade The blade of this embodiment Length/m 50 55 Rated power/MW 2.5 2.5 Weight/t 11.56 11.57 Center of gravity/m 16.56 16.58 First-order waving natural frequency/Hz 0.665 0.667 Second order waving natural frequency/Hz 1.913 1.918 First-order shimmy natural frequency/Hz 1.178 1.174 Second order shimmy natural frequency/Hz 3.521 3.526 Maximum deflection of blade tip/m 11.25 11.29 Rated wind speed/(m/s) 10.5 10 Survival wind speed/(m/s) 59.5 52.5 Maximum chord length/m 3.98 3.98 Applicable wind field Class III Class II and III Single piece material cost/10,000 yuan about 60 about 60

Claims (10)

1. A preparation method of a large wind power blade hybrid composite material wing spar is characterized by comprising the following steps: the hybrid composite material wing beam comprises a wing beam sandwich layer and a wing beam skin layer coated outside the wing beam sandwich layer, wherein the wing beam sandwich layer mainly comprises a glass fiber sandwich layer close to the root part of a blade, a carbon fiber sandwich layer close to the tip part of the blade and a transition region for connecting the glass fiber sandwich layer and the carbon fiber sandwich layer, and the preparation method of the wing beam mainly comprises the following steps:

(1) pretreatment of a mold: firstly, cleaning a mold, and spraying a release agent and a gel coat;

(2) paving materials: cutting a required reinforcing material preformed body and a forming auxiliary material according to the design requirements of a wing beam, wherein the reinforcing material preformed body consists of a wing beam skin layer reinforcing material and a wing beam sandwich layer reinforcing material, the wing beam sandwich layer reinforcing material comprises a glass fiber fabric close to the root part of a blade, a carbon fiber fabric close to the tip part of the blade and a mixed fiber fabric for connecting the glass fiber fabric and the carbon fiber fabric, the forming auxiliary material comprises a flow guide medium, demoulding cloth, a porous isolating membrane, an air felt and a vacuum bag membrane, and the flow guide medium, the demoulding cloth, the porous isolating membrane, the reinforcing material preformed body, the porous isolating membrane and the demoulding cloth are sequentially paved on the surface of the mould pretreated in the step (1) from bottom to top; then laying a first breathable felt on corresponding demoulding cloth above the area where the glass fiber sandwich layer is located, wherein a plurality of semi-permeable ventilation joints are arranged on the first breathable felt at intervals along the length direction of the wing beam;

(3) setting a first layer of closed mold cavities: taking the projection of the boundary line of the glass fiber sandwich layer and the transition region on a horizontal plane as a boundary line, covering a mold by using a first flexible vacuum bag film at one side of the boundary line close to the glass fiber sandwich layer, covering the mold by using a flexible semi-permeable film at one side of the boundary line close to the transition region, covering the first flexible vacuum bag film and the flexible semi-permeable film on the surface of the mold through a sealant tape after the first flexible vacuum bag film and the flexible semi-permeable film are connected into a whole to form a first layer of closed mold cavity, and covering the reinforcing material pre-forming body and the forming auxiliary material;

(4) setting a second layer of closed mold cavities: laying a second breathable felt above the flexible semi-permeable membrane, wherein a plurality of ventilation joints are arranged on the second breathable felt at intervals along the length direction of the wing beam; then covering the surface of the mold with a second flexible vacuum bag film, and completely sealing and wrapping the first flexible vacuum bag film and the flexible semi-permeable film to form a second closed mold cavity, so that the second ventilated felt and the ventilation joint are positioned in the second closed mold cavity;

(5) connecting an external device: connecting all the semi-permeable ventilating joints and the ventilating joints to a vacuum pumping system, and simultaneously connecting the glue injection system to a glue injection port in the first layer of closed mold cavity;

(6) vacuum glue injection: closing the glue injection system, opening all semi-permeable ventilating joints and ventilating joints, discharging gas in the first layer of closed die cavity and the second layer of closed die cavity through the vacuumizing system, enabling the vacuum negative pressure in the first layer of closed die cavity and the second layer of closed die cavity to be achieved and stably maintained, opening the glue injection system to start injecting matrix resin to impregnate the reinforcing material preformed body in the first layer of closed die cavity, closing all the semi-permeable ventilating joints and the ventilating joints one by one from one end, set as a blade root, in the mould to one end, set as a blade tip, in the glue injection process, and controlling the flow direction of the matrix resin to realize the complete impregnation of the reinforcing material preformed body by the matrix resin;

(7) curing, forming and post-treating: and after the vacuum glue injection is finished, curing and forming are carried out, the vacuum degree in the die cavity is kept until the curing is complete in the curing and forming process, and after the curing is finished, demoulding, trimming and cleaning are carried out to obtain the integrally formed large wind power blade hybrid composite material wing beam.

2. The method for preparing a hybrid composite spar for large wind blades according to claim 1, wherein: the flexible semipermeable membrane is a membrane material which can be penetrated by gas but cannot be penetrated by the matrix resin glue solution.

3. The method for preparing a hybrid composite spar for large wind blades according to claim 1 or 2, wherein: the semi-permeable ventilation joint is a ventilation joint which can allow gas to permeate but cannot allow matrix resin glue solution to permeate, and comprises a rigid shell, wherein the bottom of the rigid shell is coated by a flow guide medium, an airflow channel is arranged in the shell, a filler is arranged at the bottom area of the airflow channel, and the filler mainly comprises the semi-permeable membrane, the flow guide medium, the semi-permeable membrane, an air-permeable felt and the flow guide medium which are sequentially stacked from bottom to top; the filling body is hermetically connected with the inner wall of the rigid shell; a valve is arranged in the airflow channel above the filling body.

4. The method for preparing a hybrid composite spar for large wind blades according to claim 1 or 2, wherein: the air connector is permeable to gas and matrix resin glue solution and comprises a rigid shell, the bottom of the rigid shell is coated with a guide medium, an air flow channel is arranged in the shell, a filler is arranged in the bottom area of the air flow channel, and the filler mainly comprises the guide medium, an air felt and the guide medium which are sequentially stacked from bottom to top; the filling body is hermetically connected with the inner wall of the rigid shell; a valve is arranged in the airflow channel above the filling body.

5. The method for preparing a hybrid composite spar for large wind blades according to claim 1 or 2, wherein: the distance between the semi-permeable ventilation joints along the length direction of the wing beam is 2 m-3 m, and the distance between the ventilation joints along the length direction of the wing beam is 1 m-2 m.

6. The preparation method of the hybrid composite material wing spar of the large wind power blade according to claim 1 or 2, wherein in the step of vacuum glue injection, the closing time interval of each semi-permeable ventilation joint is 1min to 2min, and the closing time interval of each ventilation joint is 2min to 3 min.

7. The method for preparing the hybrid composite material wing spar of the large-scale wind power blade according to claim 1, wherein the reinforcing material in the transition area is a hybrid fiber fabric, and the arrangement mode of the hybrid fiber fabric in the reinforcing material preform is as follows: gradually transitioning from all glass fiber reinforcement to all carbon fiber reinforcement in the direction from the glass fiber fabric to carbon fiber fabric;

the gradual transition specifically refers to any one of the following transition modes:

(1) the glass fiber fabric forms a transition tip in the transition area and is wedged into a V-shaped groove formed in the transition area by the carbon fiber fabric; or,

(2) the carbon fiber fabric forms a transition point in the transition zone and wedges into the V-shaped groove formed in the transition zone by the glass fiber fabric.

8. The method for manufacturing the hybrid composite material wing spar of the large-scale wind power blade according to claim 7, wherein transition connection between the glass fiber fabric and the carbon fiber fabric in the transition region is achieved through an in-layer weaving mode;

the weaving mode in the layer is as follows: and the glass fiber fabric end head and the carbon fiber fabric end head in the transition region are woven in an in-layer mixed and alternate mode, so that the glass fiber extending into the transition region in the glass fiber sandwich layer and the carbon fiber extending into the transition region in the carbon fiber sandwich layer are connected together.

9. The method for manufacturing the hybrid composite material spar of a large wind turbine blade according to claim 7, wherein the glass fiber fabric and the carbon fiber fabric in the transition region are joined in a transitional manner by means of interlayer sewing, so that the glass fiber fabric extending into the transition region in the glass fiber sandwich layer and the carbon fiber fabric extending into the transition region in the carbon fiber sandwich layer are fixedly overlapped together;

the suture thread adopted by the interlayer suture is one or more of aramid fiber yarn, quartz fiber yarn and glass fiber yarn.

10. The method for manufacturing the hybrid composite material wing spar of the large wind power blade according to any one of claims 1 and 7 to 9, wherein the thickness of the wing spar skin layer is 2mm to 3mm, and the reinforcing material used for the wing spar skin layer is glass fiber uniaxial cloth, glass fiber biaxial cloth and/or glass fiber triaxial cloth; the surface density of the glass fiber fabric in the interlayer of the wing beam is 1000g/m²The above uniaxial fabric, the carbon fiber fabric in the spar sandwich layer is 600g/m in surface density²The above uniaxial textile.