Wind tunnel blade and preparation method thereof

Abstract

The invention discloses a wind tunnel blade in the technical field of composite material products, and the wind tunnel blade comprises a foam core, the end part of the foam core is fixedly connected with a blade handle, auxiliary beams are fixedly mounted on one side of the blade handle and one side of the foam core, and main beams are mounted on the surfaces of the auxiliary beams, the other side of the blade handle, the other side of the foam core and the end part of the foam core; a front edge beam is installed on the front edge of the foam core, a skin is laid on the outer surface of the blade, and the defects that in the prior art, an autoclave and RTM forming method is high in porosity, high in glue content, uneven in glue distribution, large in operation labor intensity and the like are overcome; the consistency of the weight and the gravity center of the wind tunnel blade is effectively guaranteed, the production efficiency of the wind tunnel blade is improved, and the method can be used for manufacturing large wind tunnel blades.

Description

Technical Field

[0001] The invention relates to the technical field of composite material products, and in particular to a method for preparing a composite blade. Background Art

[0002] The prior art discloses that the molding of wind tunnel blades often adopts the "autoclave + RTM molding" method, in which the beam, front beam and inner skin are molded by autoclave, and the outer skin and wind tunnel blade are molded by RTM. This molding method autoclave molding can ensure that the internal resin content of the wind tunnel blade is uniform, the internal structure is dense, the porosity is low, and the mechanical properties are stable and reliable. However, the RTM molding process has defects such as high porosity of the blade, high and uneven distribution of glue content, and high labor intensity of operation, which affects the weight of the wind tunnel blade, the consistency of the center of gravity and the production efficiency of the wind tunnel blade.

[0003] The RTM molding process is to place the reinforcement material preform in a closed molding mold in advance, inject low-viscosity thermosetting resin into the mold cavity through a glue injection device, infiltrate the reinforcement material preform, and heat the mold to solidify the resin to form a product.

[0004] Wind tunnel blades (hereinafter referred to as "blades") are composed of metal petioles and composite blade components. Combined with the structural characteristics of the blades, there are sealing problems at the petiole cylinder of the molding mold. Poor sealing will cause glue flow in the mold during glue injection, resulting in glue injection failure. At the same time, air will enter the glue injection process, making the surface prone to defects such as glue deficiency and stratification. In addition, during the glue injection process, resin enters the foam core, which can easily cause problems such as insufficient injection resin or a large deviation in the center of mass position of the blade, as well as incomplete penetration of the outer skin fabric. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a wind tunnel blade and a preparation method thereof, which adopts "autoclave + compression molding" in combination with a petiole and a foam core arranged in a vertical direction to prepare the wind tunnel blade, thereby solving the defects of the "autoclave + RTM molding" method in the prior art, such as high porosity, high and uneven glue content, and high labor intensity in operation; effectively ensuring the consistency of the weight and center of gravity of the wind tunnel blade, and improving the production efficiency of the wind tunnel blade.

[0006] The object of the present invention is achieved as follows: A wind tunnel blade comprises a foam core, the end of the foam core is fixedly connected to the petiole, an auxiliary beam is fixedly installed on one side of the petiole and one side of the foam core, the surface of the auxiliary beam, the other side of the petiole, the other side of the foam core, and the end of the foam core are installed with a main beam, the leading edge of the foam core is installed with a leading edge beam, and the outer surface of the blade is paved with a skin. A wind tunnel blade comprises a foam core, the end of the foam core is fixedly connected to the petiole, the one side of the petiole and one side of the foam core are fixedly installed with an auxiliary beam, the surface of the auxiliary beam, the other side of the petiole, the other side of the foam core, and the end of the foam core are installed with a main beam, the leading edge of the foam core is installed with a leading edge beam, and the outer surface of the blade is paved with a skin.

[0007] Furthermore, the auxiliary beam is installed on the windward side of the blade.

[0008] Furthermore, the main beam is installed at the middle position of both sides of the blade.

[0009] A method for preparing a wind tunnel blade comprises the following steps: Step 1) Gluing the foam core and the metal petiole: The foam core and the petiole are glued and fixed by using an integral laying tool, wherein the integral laying tool hoists the petiole and glues the foam core at the bottom of the petiole in a vertical hoisting state, so that the petiole and the foam core are in a hoisting state as a whole; Step 2) Forming the leading edge beam and the auxiliary beam: laying the prepreg sheets of the leading edge beam and the auxiliary beam in the corresponding molds for vacuum laying and compaction and autoclave compaction, and then demoulding to obtain the leading edge beam and the auxiliary beam; Step 3) forming the main beam: first install the auxiliary beam obtained in step 2) to the corresponding position of the foam core, and perform vacuum laying and compaction treatment; then lay the main beam prepreg sheet on the foam core and auxiliary beam in the vertical hoisting state, and perform vacuum laying and compaction for multiple times. After the main beam is laid, install the leading edge beam obtained in step 2) to the corresponding position of the foam core, and perform vacuum laying and compaction treatment for multiple times, and finally enter the autoclave for pre-compacting treatment, and obtain the blade preform after demoulding; Step 4) Skin and blade molding: Lay the inner skin prepreg sheet on the corresponding position of the foam core and perform vacuum laying and compaction treatment; lay the outer skin of the non-working surface and the working surface in the blade molding mold cavity, put in the blade core preform, and perform hot press molding on it to obtain a wind tunnel blade.

[0010] Furthermore, the overall placement tooling of step 1) includes a gantry, the top of the gantry is equipped with a petiole positioning pile for fixing and hoisting the petiole, and the bottom of the gantry is located below the petiole positioning pile and is provided with a supporting positioning pile; step 1) specifically includes: firstly hoisting the petiole on the petiole positioning pile, then assembling the foam core and the petiole, adjusting the coaxiality with the supporting positioning pile, and fixing the petiole on the petiole positioning pile; and gluing and fixing are performed in an oven.

[0011] Furthermore, in step 2), vacuum placement and compaction during the placement of the leading edge beam and the auxiliary beam are specifically as follows: peeling cloth, isolation film and breathable felt are evenly placed on the surface of the prepreg blank in sequence, and then the mold is sealed as a whole using sealing tape and vacuum bag film.

[0012] Furthermore, the specific process of installing the auxiliary beam in step 3) is: receiving the auxiliary beam, removing the storage package of the auxiliary beam, and not removing the peeling cloth; performing a trial installation of the auxiliary beam and the foam core at the installation interface of the auxiliary beam and the foam core, and then laying a layer of adhesive film on the installation interface area of ​​the auxiliary beam and the foam core, and finally, laying glass cloth on the contact surface of the auxiliary beam and the petiole, installing the auxiliary beam on the foam core, and vacuuming and compacting it.

[0013] Furthermore, the specific process of the leading edge beam installation in step 3) is: receive the leading edge beam, remove the preservation packaging of the leading edge beam, and do not remove the peeling cloth; conduct a trial installation of the leading edge beam and the foam core at the installation interface of the leading edge beam and the foam core, and then stick a layer of adhesive film on the installation interface area of ​​the leading edge beam and the foam core, and after the leading edge beam is installed on the foam core, it is packaged and vacuumed for pre-compaction treatment.

[0014] Furthermore, in step 3), the main beam includes side beams laid on both sides of the foam core and a cross beam connecting the side beams from the petiole, and a circular hole matching the petiole is formed on the cross beam; The thickness of the side sheet beam decreases in sequence along the axial direction from the blade root to the blade tip; The size of the ply cut pieces of the side beam decreases cyclically along the axial direction from the blade tip to the blade root; When laying the side beams, the bottom and top layers are laid in one piece, and the middle layer is laid in transition. When laying the cross beams, bypass the shoulder of the petiole and lay them continuously at the bottom of the "U". The prepregs on both sides of the petiole on the crossbeam are complete prepregs continuously laid from one side sheet beam to the other side sheet beam, and the prepregs on the crossbeam at the petiole are prepregs of the sheet beams on both sides laid separately and independently to the petiole; The layer laying sequence is 0° / +45° / 0° / 0° / 0° / -45° / 0°, and the width of the sheet in the +45° / -45° direction is 200mm-300mm.

[0015] Furthermore, in step 4), when the inner skin is laid, the thickness of the inner skin is 1.75 mm, and the material is T700 / E1302 unidirectional carbon fiber prepreg; the ply laying sequence of the inner skin is +45° / 90° / -45° / 90° / -45° / 90° / +45° / +45° / 90° / -45° / 90° / -45° / 90° / +45°, for a total of 14 layers; the first layer and every 4 layers are subjected to vacuum compaction treatment until all the prepregs are laid; The width of the sheet in the 45° / -45° direction is 200mm-300mm. The overlap method is butt joint. The butt joint interfaces are staggered. An overlap of ≤5mm is allowed at the root and tip sections to ensure that the sheet is continuous and unbroken. The inner skin prepreg sheet in the 90° laying direction starts from the trailing edge of the blade and is laid along the working surface, leading edge, and non-working surface to the trailing edge of the blade. The root end surface and the tip end surface are laid separately, and the sheets of the working surface and the non-working surface are widened, allowing an overlap of ≤5mm. Step 4) When laying the inner and outer skins, lay the non-working surface outer skin and the working surface outer skin respectively in the non-working surface and the coplanar blade molding model cavity. After the first layer and the laying are completed, vacuum compaction treatment is required; use compressed air to clean the impurities on the surface of the blade core preform, and then place the blade core preform on the non-working surface mold cavity surface; and fill the blade core preform with appropriate foam glue at both ends of the petiole and the tip.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The "autoclave + compression molding" method adopted in the present invention is beneficial to the integrity of the blade (the raw materials of the outer skin and the inner skin are the same resin, which reduces the problem of interface bonding between each other), can effectively improve the stiffness and strength of the blade; at the same time, it can effectively reduce the internal defects of the blade; compression molding can increase the volume content of composite fiber and improve the mechanical properties of the composite material; in addition, compared with the RTM molding process, the compression molding process has fewer operating procedures, no glue injection pre-treatment and other procedures, and with the help of a hot press in the mold closing and heating method, the blade production cycle can be effectively shortened and its production efficiency can be improved.

[0017] The present invention adopts vertical hoisting arrangement of petiole and foam core, the petiole is in a natural vertical state, and the foam core is limited to the petiole, so that the coaxiality of the blade and the foam core is guaranteed; the blade is directly paved on the vertically hoisted foam core, and the foam core is used as a laying reference, so the cost is low, and the auxiliary beam and the leading edge beam can be installed and laid at the same time, reducing the multiple laying and turning operations of the main beam and the inner skin, shortening the manufacturing cycle, reducing the laying difficulty, and making the laying more convenient; after the installation and laying are completed, the autoclave is used for pre-compaction treatment, so that the auxiliary beam, the leading edge beam, the inner skin and the main beam are more closely fitted with the petiole and the foam core, while ensuring the glue content and quality at each position, and ensuring the controllability and consistency of the blade weight and center of gravity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0019] Figure 1 It is a schematic diagram of the wind tunnel blade structure in the present invention.

[0020] Figure 2 It is an exploded view of the wind tunnel blade structure in the present invention.

[0021] Figure 3 It is a schematic diagram of the overall laying tooling structure in the present invention.

[0022] Figure 4 This is a schematic diagram of the petiole positioning pile structure in the overall laying tooling.

[0023] Figure 5 This is a schematic diagram of the supporting positioning pile structure in the overall laying tooling.

[0024] Figure 6 This is a schematic diagram of the overall placement of tooling and wind tunnel blades.

[0025] Figure 7 It is a schematic diagram of the front edge beam paving mold in the present invention.

[0026] Figure 8 It is a schematic diagram of the auxiliary beam paving mold in the present invention.

[0027] Fig. 9 It is a schematic diagram of the blade main beam ply transition in the present invention.

[0028] Fig.10 It is a schematic diagram of the ply angle of the blade main beam at 45° in the present invention.

[0029] Fig.11 It is a schematic diagram of the ply laying at 0° direction of the blade main beam in the present invention.

[0030] Among them, 100 gantry, 200 petiole positioning pile, 201 upper positioning sleeve, 202 locking nut, 203 support flange, 204 reinforcement rib, 300 support positioning pile, 301 support base plate, 302 lower positioning sleeve, 303 positioning column, 304 positioning plate, 305 hand lever, 400 wind tunnel blade, 401 petiole, 402 foam core, 403 leading edge beam, 404 auxiliary beam, 405 main beam, 406 skin. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1 A wind tunnel blade 400 includes a foam core 402, the end of the foam core 402 is fixedly connected to a petiole 401, auxiliary beams 404 are fixedly installed on one side of the petiole 401 and one side of the foam core 402, main beams 405 are installed on the surface of the auxiliary beam 404, the other side of the petiole 401, the other side of the foam core 402, and the end of the foam core 402, a leading edge beam 403 is installed on the leading edge of the foam core 402, a skin 406 is laid on the outer surface of the blade, the auxiliary beams 404 are installed on the windward side of the blade, and the main beams 405 are installed in the middle of both sides of the blade.

[0033] Specifically, the blade foam core 402 is made of polymethacrylimide (PMI) rigid foam, which has the characteristics of light weight, high strength, uniform structure, and high / low temperature resistance. The foam core 402 is formed by CNC machine, which can ensure the appearance quality of the foam core 402 and its weight requirement.

[0034] Furthermore, the blade uses T700J / E1302 unidirectional carbon fiber prepreg and T700 / E1302 unidirectional carbon fiber prepreg as the main materials; SYT45 / E1302 plain carbon fiber prepreg is selected as the outer skin 406 material.

[0035] Specifically, the leading edge beam 403 structure is a thin-walled "C" type. Based on previous molding experience, the leading edge beam 403 adopts the autoclave + prepreg molding method, which can ensure the internal quality of the main beam 405 and the weight consistency. The material of the leading edge beam 403 is T700 / E1302 unidirectional carbon fiber prepreg, and its layer laying sequence is [0° / +45° / 0° / 0° / 0° / -45° / 0°], 8 identical cycle layers, a total of 56 layers.

[0036] Specifically, the leading edge beam 403 is formed by performing multiple vacuum laying and compaction treatments + autoclave pre-compacting molding on the leading edge beam 403 laying mold.

[0037] Furthermore, the auxiliary beam 404 is in the shape of a small curvature flat plate, with its root flush with the end face of the petiole 401 and the other side flush with the foam end face. It is arranged on the inner side of the "U"-shaped main beam 405 and the outer side of the blade foam working surface, with equal width, and symmetrically arranged on the axis of the blade in the width direction. According to the external structure of the auxiliary beam 404, the auxiliary beam 404 adopts the autoclave molding method, which can fully ensure that the resin content of the auxiliary beam 404 is uniform, the internal density is dense, and the void ratio is reduced. During the laying process of the auxiliary beam 404, multiple vacuum laying and compaction treatments + autoclave pre-compacting molding are performed.

[0038] It should be noted that the metal petiole 401 is glued to the foam core 402 and the auxiliary beam 404. When the auxiliary beam 404 is installed on the foam core 402, in order to prevent potential corrosion between the carbon fiber and the metal petiole 401, a layer of glass fabric prepreg is laid between the end of the petiole 401 and the contact surface of the prepreg.

[0039] Furthermore, the main beam 405 is a "U"-shaped structure. The thickness of the main beam 405 decreases from the blade root to the blade tip, with a thickness of 7mm at the blade root and 1.05mm at the blade tip. In order to ensure its quality, a hot autoclave + prepreg molding method is used, which can ensure the internal quality of the main beam 405 and ensure weight consistency.

[0040] Specifically, the material of the main beam 405 is T700J / E1302 and T700 / E1302 unidirectional carbon fiber prepreg, and the ply laying sequence is [0° / +45° / 0° / 0° / 0° / -45° / 0°], 8 identical cycle plies, and a total of 56 layers. The main beam 405 consists of 8 cycle transition stages in the length direction of the blade, with the entire layer being laid in the cycle 1 stage, and a single-layer transition starting from the cycle 2 stage until the cycle 7 stage, and then there is no transition laying in the cycle 8 stage. The beams on the working surface and the non-working surface bypass the shoulders of the petiole 401 and are continuous at the bottom of the "U", with the same ply laying on both sides. The molding method of the main beam 405 is multiple vacuum laying and compaction treatments + multiple autoclave pre-compacting molding (the foam core 402 is used as a mold after being glued to the metal petiole 401, and is directly laid on its surface).

[0041] Specifically, the inner skin 406 is a layer of equal thickness of 1.75 mm, wrapped around the outer layer of the foam core 402, the main beam 405 and the leading edge beam 403 of the blade, and its main function is to form a closed cavity enclosure with the foam core 402, the main beam 405 and the leading edge beam 403. The material of the inner skin 406 is T700 / E1302 unidirectional carbon fiber prepreg, and its layer laying sequence is [+45° / 90° / -45° / 90° / -45° / 90° / +45° / +45° / 90° / -45° / 90° / -45° / 90° / +45°]. The molding method of the inner skin 406 is to lay the prepreg sheet directly on the foam core 402, and perform vacuum laying and compaction treatment for multiple times to form a blade core preform, and finally perform compression molding together with the outer skin 406.

[0042] Specifically, the outer skin 406 is made of SYT45 / E1302 plain carbon fiber prepreg, the thickness of the outer skin 406 is 1 mm, and the layering sequence is [0° / 0° / 90° / 0° / 0°]. The outer skin 406 of the blade is molded by prepreg + hot press. This method is a closed mold molding method for composite materials, which can effectively ensure the outer dimensions of the blade; at the same time, it can effectively ensure the surface roughness of the blade. Due to closed mold molding, the surface roughness of the blade is determined by the surface roughness of the mold (the mold roughness can be controlled at about Ra0.8).

[0043] It should be noted that in order to ensure that the profile deviation of each airfoil section of the blade is ±0.5mm, the edge pressing problem is solved in time by using a low-temperature pre-compacting method during the molding process of the outer skin 406, so that the blade mold clearance is controlled within 0.2mm. In order to ensure the appearance quality of the blade, a certain thickness of molding is reserved during the machining process of the foam core 402 to provide sufficient reverse support; at the same time, in order to improve the appearance quality of the blade top and blade shoulder, a piece of expansion film is prefabricated between the outer skin 406 and the blade top and blade shoulder of the preform.

[0044] In addition, since the entire blade is wrapped and molded with prepreg, the prepreg is made by dry molding, which can effectively control the resin content within 2%, and each part is accurately cut using a CNC automatic cutting machine to ensure the consistency of the sheet size, thereby effectively ensuring the deviation of the weight of each part, so that the total mass of a single blade assembly is ≤130kg.

[0045] Example 2 A method for preparing a wind tunnel blade comprises the following steps: Step 1) The foam and the petiole 401 are glued and fixed as follows: 1-1) Raw material re-inspection and preparation: When materials are put into storage, check whether the types, brands and manufacturers of all raw materials involved in blade molding meet the requirements, accept the raw material certificates and re-inspect the raw materials; receive qualified foam core 402 materials, adhesives and metal petioles 401, and check the material certificates, re-inspection certificates and whether they are within the validity period before use.

[0046] 1-2) Foam machining: The foam is machined according to the three-dimensional digital model of the blade foam core 402 so that the foam core 402 reaches the required dimensional accuracy. It is weighed and an inspection report is required. It can only be used after passing the inspection.

[0047] 1-3) Dehumidification treatment of foam core 402: Take qualified foam core 402, or use clean and oil-free compressed air to remove the powder on the surface of foam core 402, then wrap it with a porous isolation film, and finally put it in an oven at 120℃ for 2 hours to ensure that the water vapor inside the foam is removed to prevent shrinkage during curing.

[0048] 1-4) Sandblasting of petiole 401: Sandblasting is performed on the joint surface of petiole 401 to remove the oxide film on the joint surface, improve the cleanliness of the joint surface, increase the surface roughness, and the contact area between the adhesive. After sandblasting, it needs to be transferred to the next process in time. Generally, the logistics transfer time is controlled within 2 hours to the bonding site, and the maximum period between the sandblasting process and bonding is 8 hours.

[0049] 1-5) Gluing of foam core 402 and petiole 401: Before gluing, install petiole 401 on petiole positioning pile 200 of integral laying tooling and lock it with locking nut 202. Then clean the inner cavity of the surface to be glued of petiole 401 joint with acetone, and pre-install it with foam core 402. Subsequently, apply 1 layer of AW116 adhesive on the root of foam core 402 to be glued and the inner surface of petiole 401 joint respectively, lay 1 layer of glass fiber cloth on the root of foam core 402 to be glued, and then glue foam core 402 and petiole 401. Clean the excess adhesive with acetone to ensure the glueing accuracy and cleanliness. In addition, this process is completed in a clean room.

[0050] Specifically, the overall laying tooling includes a gantry 100, the top of the gantry 100 is equipped with a petiole positioning pile 200 for fixing and hoisting the petiole 401, the bottom of the gantry 100 is located below the petiole positioning pile 200 and is provided with a supporting positioning pile 300, the petiole positioning pile 200 includes an upper positioning sleeve 201 and a locking nut 202, the top of the upper positioning sleeve 201 is provided with a supporting flange 203, and a reinforcing rib 204 is provided between the supporting flange 203 and the upper positioning sleeve 201, the supporting positioning pile 300 includes a supporting base plate 301, a lower positioning sleeve 302 is provided on the supporting base plate 301, a liftable positioning column 303 is provided on the top of the lower positioning sleeve 302, the bottom of the lower positioning sleeve 302 is installed on the supporting base plate 301 via a positioning plate 304, the positioning column 303 is threadedly connected to the lower positioning sleeve 302, and a hand rod 305 is passed through the positioning column 303.

[0051] 1-6) Curing of the foam core 402 and the petiole 401: The overall laying tooling is transferred to an oven, which can be vacuum-packaged to enhance the bonding effect between the foam core 402 and the petiole 401, and kept warm at a temperature of 45°C-60°C for 2h±10min.

[0052] Step 2) Forming of the leading edge beam 403 and the auxiliary beam 404, specifically as follows: 2-1) Raw material preparation: Collect qualified T700J / E1302 unidirectional carbon fiber prepreg, T700 / E1302 unidirectional carbon fiber prepreg, medium temperature epoxy film and other raw materials, and check the material certificate, re-inspection certificate and whether they are within the validity period before use.

[0053] 2-2) Mold preparation: Check the flatness and dimensional accuracy of the mold used for auxiliary beam 404. After the new mold is inspected and qualified, use absorbent cotton (or wiping paper) dipped in an appropriate amount of acetone to clean the mold surface until the gauze has no different color, let it dry at room temperature for more than 15 minutes, then apply a layer of release cloth to the paving surface, and then use wiping paper dipped in an appropriate amount of anhydrous ethanol to wipe the surface of the release cloth until the wiping paper has no different color. After drying, it can be paved. After the last layer of release agent is wiped, after the release agent is cured, use a clean wipe to wipe off the thin mist beads formed by the release agent in the same direction until there is no different color.

[0054] 2-3) Automatic material cutting: According to the three-dimensional digital model surface of the leading edge beam 403 and the auxiliary beam 404, the laying surface is extracted and unfolded in a plane. The shape of each layer of prepreg of the leading edge beam 403 and the auxiliary beam 404 is drawn using Catia software and Fibersim three-dimensional software. The pieces with different laying angles can be cut according to the actual situation to reduce the difficulty of prepreg laying and improve the utilization rate of materials. At the same time, it is imported into the operating system of the automatic material cutting machine, and the prepreg is placed on the bracket of the automatic material cutting machine. Each piece of material is cut according to the program, and the prepreg pieces of the leading edge and the auxiliary beam 404 are cut out, and the label paper is used to mark the number, part name and date.

[0055] 2-4) Laying of the leading edge beam 403: Before laying, the operator checks whether the number of layers and quantity of the prepreg sheets are complete according to the design requirements of the leading edge beam 403 prepreg ply. The thickness of the leading edge beam 403 is 7mm, and the ply laying sequence is [0° / +45° / 0° / 0° / 0° / -45° / 0°], with 8 identical cycle plies and a total of 56 layers. The prepreg sheets are laid to the corresponding positions of the foam core 402, and a gap of 2mm is required from the edge to ensure that the fibers are flat and extended when the prepreg is compacted. The sheets are staggered and butt-jointed, and the R-angle area is compacted with a rolling plate during the laying process. The first layer of ply is required to be vacuum compacted, and thereafter, vacuum compaction is performed once every 4 to 6 layers, and pre-compacting and molding in an autoclave is performed once every 16 layers until the laying is completed. The laying mold is as follows: Figure 7 shown.

[0056] 2-5) Laying of auxiliary beam 404: Before laying, the operator checks whether the number of layers and quantity of prepreg pieces are complete according to the design requirements of auxiliary beam 404 prepreg laying. Lay the pieces on the auxiliary beam 404 laying mold in sequence according to the laying sequence design requirements. The laying sequence is [0° / +45° / 0° / 0° / 0° / 90° / 0° / 0° / 0° / -45° / 0° / 0° / -45° / 0° / 0° / 0° / 90° / 0° / 0° / 0° / +45° / 0° / ], for a total of 22 layers. The prepreg pieces are laid to the mold product line, and the pieces are staggered and butted. During the laying process, a rolling plate is used to compact the R-angle area. The first layer of laying is required to be vacuum compacted. Thereafter, vacuum compaction is performed once every 4 to 6 layers. The above operation is repeated until the laying is completed. The laying mold is as follows: Figure 8 shown.

[0057] 2-6) Vacuum packaging: Place the peeling cloth, isolation film and breathable felt evenly on the surface of the prepreg blank, and then use sealing tape and vacuum bag film to seal the mold as a whole. Check the air tightness of the vacuum bag film: the vacuum degree is required to be less than -0.095MPa.

[0058] 2-7) Autoclave pre-compacting treatment: The mold temperature is raised to 90℃±5℃ at a heating rate of no more than 1.5℃ / min, kept at this temperature for 2.0h±10min, and then cooled to below 45℃ at a cooling rate of no more than 2℃ / min before unloading the pressure and opening the mold. The pressure is 0.6±0.05MPa.

[0059] 2-8) Demolding and cleaning: When demolding, remove the vacuum packaging material (do not remove the peeling cloth), open the mold safely without bumping or falling, and do not use hammers, copper rods or other tools to directly hit, and isolate and protect the front edge beam 403 and auxiliary beam 404 to avoid contamination of the blank, and transfer them to the clean room for the next process. The mold is cleaned with acetone, and the mold is cured and stored.

[0060] 2-9) Profiling and cleaning: Profiling and burr grinding are performed along the inner product lines of the leading edge beam 403 and the auxiliary beam 404. Impurities on the surface are blown away with compressed air, and the burrs around are smooth and clean.

[0061] 2-10) Check the appearance and non-destructive testing of the leading edge beam 403 and the auxiliary beam 404 and record them, and visually observe whether the mold has bumps and damages. After passing the test, the leading edge beam 403 and the auxiliary beam 404 will be vacuum-packed and stored for use.

[0062] Step 3) forming the main beam 405, as follows: 3-1) Raw material preparation: Collect qualified T700J / E1302 unidirectional carbon fiber prepreg, T700 / E1302 unidirectional carbon fiber prepreg, medium temperature epoxy film and other raw materials, and check the material certificate, re-inspection certificate and whether they are within the validity period before use.

[0063] 3-2) Automatic cutting: Use Fibersim software to make the electronic cutting diagram of the main beam 405, and use the automatic cutting machine to cut the material pieces. After cutting, check whether the pieces are complete and sort the pieces according to the laying order.

[0064] 3-3) Installation of auxiliary beam 404: Receive qualified auxiliary beam 404, remove the preservation package of auxiliary beam 404, and do not remove the peeling cloth (the peeling cloth on the contact surface between auxiliary beam 404 and main beam 405 can be removed only when laying main beam 405); test-install auxiliary beam 404 and foam core 402 at the installation interface between auxiliary beam 404 and foam core 402. Then, lay a layer of adhesive film on the installation interface area between auxiliary beam 404 and foam core 402, and finally, lay a layer of glass cloth on the contact surface between auxiliary beam 404 and petiole 401 to prevent potential corrosion. Install auxiliary beam 404 on foam core 402 and vacuum and compact it.

[0065] 3-4) Laying of main beam 405: Before laying, the operator shall check whether the number and quantity of prepreg ply of main beam 405 are complete according to the design requirements of prepreg ply. According to the technical requirements of three-dimensional digital model and two-dimensional drawing, the thickness of main beam 405 decreases from blade root to blade tip. The thickness at blade root is 7mm and the thickness at blade tip is 1.05mm. The size of ply ply of main beam 405 decreases cyclically along the axial direction from blade tip to blade root. According to the design requirements of ply of main beam 405, the ply laying sequence is [0° / +45° / 0° / 0° / 0° / -45° / 0°], 8 identical cyclic plies, totaling 56 layers. Fig. 9 As shown, the main beam 405 has 8 cycle transition stages in the length direction of the blade. The whole is laid in cycle 1, and the single-layer transition length of 50mm starts from cycle 2 until cycle 7, and then there is no transition in cycle 8. The beams of the working surface and non-working surface bypass the shoulder of the petiole 401 and are continuous at the bottom of the "U", with the same layer laying on both sides.

[0066] Laying of prepreg pieces in the +45° / -45° direction: Due to the presence of petiole 401, the blade needs to be divided into three parts when laying prepreg pieces in the +45° / -45° direction, such as Fig.10 As shown, for the paving areas ① and ③, +45° / -45° sheets can maintain continuous fiber paving; for area ②, sheets are allowed to be laid along the working surface and non-working surface respectively. Because the fiber curvature changes greatly during paving, the method of reducing the sheet width is adopted to adapt to the change of curvature, that is, sheets with a width of 200mm-300mm are selected, and the splicing method is staggered docking, the splicing gap or overlap width is not greater than 1mm, and docking is not allowed along the fiber direction. In the subsequent paving, the docking interface needs to be staggered to avoid low local strength.

[0067] Laying of 0° directional prepreg pieces: When laying 0° directional prepreg, due to the presence of the petiole 401, the paving surface is divided into three areas, such as Fig.11 As shown. Areas ① and ③ are areas without petiole 401 interference, and the 0° direction fibers are required to be continuous and unbroken, that is, starting from the working surface, they are directly laid through the root end face to the non-working surface. For area ② with petiole 401 interference, it is impossible to ensure the continuous laying of 0° direction fibers, so the petiole 401 is used as the dividing line, and the working surface and non-working surface are laid separately. The staggered joint is selected for splicing. During the laying process, the joint interfaces need to be staggered to avoid excessive local stress. See the schematic diagram of the laying layer. Fig.11 .

[0068] 3-5) Installation of the leading edge beam 403: Receive qualified leading edge beam 403, remove the preservation package of leading edge beam 403, and do not remove the peeling cloth (the peeling cloth on the contact surface between leading edge beam 403 and inner skin 406 can be removed only when laying inner skin 406); test-install leading edge beam 403 and foam core 402 at the installation interface between leading edge beam 403 and foam core 402. Subsequently, a layer of medium-temperature epoxy film is pasted on the installation interface area between leading edge beam 403 and foam core 402, and after the leading edge beam 403 is installed on the foam core 402, it is packaged and vacuumed for pre-compaction.

[0069] 3-6) Vacuum packaging: Place peeling cloth, isolation film and breathable felt evenly on the surface of the blade core preform, and then use sealing tape and vacuum bag film to seal the mold as a whole, and try to reduce wrinkles as much as possible. Test the air tightness of the vacuum bag film: the vacuum degree is required to be less than -0.095MPa.

[0070] 3-7) Autoclave pre-compacting treatment: The mold temperature is raised to 90℃±5℃ at a heating rate of no more than 1.5℃ / min, kept at this temperature for 2.0h±10min, and then cooled to below 45℃ at a cooling rate of no more than 2℃ / min before the pressure is released and the mold is opened. The pressure is 0.6±0.05MPa.

[0071] 8) Demolding and cleaning: Remove excess debris during demoulding (do not remove the peeling cloth on the surface of the preform). Be careful not to use sharp objects to force demoulding to avoid damaging the product. Isolate and protect the blade preform to avoid contamination and transfer it to the next process.

[0072] Step 4) Skin 406 and blade molding 4-1) Raw material preparation: Collect qualified SYT45 / E1302 plain carbon fiber prepreg, foam glue and other raw materials, and check the material certificate, re-inspection certificate and whether they are within the validity period before use.

[0073] 4-2) Automatic cutting: Use Fibersim software to make the electronic cutting diagram of the main beam 405, and use the automatic cutting machine to cut the material pieces. After cutting, check whether the pieces are complete and sort the pieces according to the laying order.

[0074] 4-3) Laying of inner skin 406: The thickness of inner skin 406 is 1.75mm, and the material is T700 / E1302 unidirectional carbon fiber prepreg. The laying order of inner skin 406 is [+45° / 90° / -45° / 90° / -45° / 90° / +45° / +45° / 90° / -45° / 90° / -45° / 90° / +45°], with a total of 14 layers. The first layer and every 4 layers are vacuum compacted until all prepregs are laid.

[0075] In order to reduce the distortion of the inner skin 406 prepreg sheets in the +45° / -45° direction, the width of the prepreg sheets in the +45° / -45° direction is adjusted to 200mm-300mm, and the overlapping method is selected as butt-jointing. The butt joints are staggered, and an overlap of ≤5mm is allowed at the root and tip sections to ensure that the sheets are continuous and not broken.

[0076] The 90° paving direction of the inner skin 406 prepreg cut pieces starts from the trailing edge of the blade and is laid along the working surface, leading edge, and non-working surface to the trailing edge of the blade. The prepreg is required to be as continuous as possible without breaking. The root end face and the tip end face of the blade can be laid separately, that is, the material is cut according to the shape of the end face, and then accurately laid to the profile. In order to strengthen the strength of the joints between the upper and lower end faces and the working and non-working surfaces, the sheets of the working and non-working surfaces can be appropriately widened, and an overlap of ≤5mm is allowed.

[0077] 4-4) Preparation of blade forming mold: Clean the qualified mold cavity and apply more than 3 release agents.

[0078] 4-5) Laying down of outer skin 406: The thickness of outer skin 406 is 1 mm. The material used is SYT45 / E1302 plain carbon fiber prepreg, and the layer laying sequence is [0° / 0° / 90° / 0° / 0°].

[0079] 4-6) Preform installation: Lay the non-working surface skin 406 and the working surface skin 406 in the non-working surface and coplanar blade molding mold cavity respectively. After the first layer and the layer laying are completed, vacuum compaction treatment is required; use compressed air to clean the impurities on the surface of the blade core preform, and then place the blade core preform on the non-working surface mold cavity surface. Fill the blade core preform with appropriate foam glue at both ends of the petiole 401 and the blade tip.

[0080] 4-7) Hot press molding and curing: with an initial pressure of 8MPa±0.1MPa, heat the mold to 90℃±5℃ at a heating rate of no more than 1.5℃ / min, adjust the pressure to 10MPa±0.1MPa, and keep the temperature and pressure under this condition for 1.0h±10min; continue to heat the mold to 130℃±5℃ at the same heating rate, keep the temperature and pressure for 3h±10min, and then cool the mold to below 45℃ at a cooling rate of no more than 2℃ / min before releasing the pressure and opening the mold.

[0081] 4-8) Demolding and trimming: Remove excess debris during demoulding (do not remove the peeling cloth on the surface of the preform). Be careful not to use sharp objects to force demoulding to avoid damaging the product, and cut the excess and trim the shape of the blade.

[0082] 4-9) Inspection: Weigh and record the blades, and inspect the internal and external quality of the blades as required.

[0083] 4-10) Balance: Use a torque scale to initially weigh the blade torque, and then add weights according to design requirements. When adding weights, try to place them at the root of the blade without affecting the load-bearing condition at the root of the blade.

[0084] 4-11) Spraying: Determine the coating color, brand and material standard according to the design requirements of the blade.

[0085] ① First, protect the non-painted areas such as the petiole 401 area with masking tape or plastic film.

[0086] ② Repair the surface to be painted. If there are bubbles, sand holes, pits, wrinkles and other defects on the blade surface, fill and repair them with epoxy resin or polyvinyl putty of the same material as the outer skin 406, spray the surface coating, and grind and polish.

[0087] ③ Roughen the surface to be painted, use a P240 pneumatic grinder to fully cover the roughened painted surface area, use a cleaning agent, acetone or industrial ethanol to clean the painted surface and then paint it after it is dry.

[0088] ④ Spraying primer and topcoat: Spraying primer is mainly to increase the adsorption strength of topcoat, and topcoat is camouflage color. Since the paint layer of a single spray is thin, it is necessary to repeatedly fill in the gaps and spray points under strong light, while avoiding omissions and glue flow during the spraying process. The painting conditions meet the relevant requirements of QJ2057-1991 "Painting Quality Control".

[0089] ⑤ Inspection record of paint surface: Inspection shall be in accordance with the index requirements of Level III in QJ813A-1996 "General Technical Conditions for Painting".

[0090] ⑥Surface roughness detection: The surface roughness of the blade is measured using the TR200 surface roughness tester produced by Cyber ​​Ruixin, and the measurement result is Ra grade data.

[0091] 4-12) Stiffness test: The blades are installed into the testing fixture and fixed, and then the stiffness test is carried out according to the design requirements.

[0092] 4-13) Natural frequency detection: The blades are installed and fixed into the detection fixture, and then the natural frequency of the blades is detected using a natural frequency detector.

[0093] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A wind tunnel blade, characterized in that: The blade comprises a foam core (402), the end of the foam core (402) being fixedly connected to a petiole (401), an auxiliary beam (404) being fixedly mounted on one side of the petiole (401) and one side of the foam core (402), a main beam (405) being mounted on the surface of the auxiliary beam (404), the other side of the petiole (401), the other side of the foam core (402), and the end of the foam core (402), a leading edge beam (403) being mounted on the leading edge of the foam core (402), and a skin (406) being paved on the outer surface of the blade.

2. A wind tunnel blade according to claim 1, characterized in that: The auxiliary beam (404) is installed on the windward side of the blade.

3. A wind tunnel blade according to claim 1 or 2, characterized in that: The main beam (405) is installed at the middle position of both sides of the blade.

4. A method for preparing a wind tunnel blade according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1) Gluing the foam core (402) and the metal petiole (401): The foam core (402) and the petiole (401) are glued and fixed by using an integral laying tool, wherein the integral laying tool hoists the petiole (401) and glues the foam core (402) to the bottom of the petiole (401) in a vertically hoisted state, so that the petiole (401) and the foam core (402) are in a hoisted state as a whole; Step 2) Forming the leading edge beam (403) and the auxiliary beam (404): placing the prepreg sheets of the leading edge beam (403) and the auxiliary beam (404) in corresponding molds for vacuum placement and compaction and autoclave compaction, and then demolding to obtain the leading edge beam (403) and the auxiliary beam (404); Step 3) Forming of the main beam (405): first, the auxiliary beam (404) obtained in step 2) is installed at the corresponding position of the foam core (402), and vacuum laying and compacting treatment is carried out; then, the prepreg sheet of the main beam (405) is laid on the foam core (402) and the auxiliary beam (404) in a vertically hoisted state, and vacuum laying and compacting are carried out multiple times. After the main beam (405) is laid, the leading edge beam (403) obtained in step 2) is installed at the corresponding position of the foam core (402), and vacuum laying and compacting treatment is carried out multiple times, and finally, it is put into the autoclave for pre-compacting treatment, and the blade preform is obtained after demoulding; Step 4) Skin (406) and blade molding: the inner skin (406) prepreg sheet is laid on the corresponding position of the foam core (402) and vacuum laid and compacted; the outer skin (406) of the non-working surface and the working surface is laid in the cavity of the blade molding mold, and the blade core preform is placed, and it is molded by a hot press to obtain a wind tunnel blade (400).

5. The method for preparing a wind tunnel blade according to claim 4, characterized in that: Step 1) The overall placement tooling comprises a gantry (100), the top of the gantry (100) is provided with a petiole positioning pile (200) for fixing and hoisting the petiole (401), and the bottom of the gantry (100) is provided with a support positioning pile (300) below the petiole positioning pile (200); Step 1) specifically comprises: firstly hoisting the petiole (401) on the petiole positioning pile (200), then assembling the foam core (402) and the petiole (401), adjusting the coaxiality with the support positioning pile (300), and fixing the petiole (401) on the petiole positioning pile (200); and gluing and fixing are performed in an oven.

6. A method for preparing a wind tunnel blade according to claim 4 or 5, characterized in that: Step 2) During the laying process of the leading edge beam (403) and the auxiliary beam (404), vacuum laying and compaction are specifically as follows: peeling cloth, isolation film and breathable felt are evenly placed on the surface of the prepreg blank in sequence, and then the mold is sealed as a whole using sealing tape and vacuum bag film.

7. A method for preparing a wind tunnel blade according to claim 4 or 5, characterized in that: The specific process of installing the auxiliary beam (404) in step 3) is as follows: receiving the auxiliary beam (404), removing the preservation package of the auxiliary beam (404) without removing the peeling cloth; performing a trial installation of the auxiliary beam (404) and the foam core (402) at the installation interface of the auxiliary beam (404) and the foam core (402), and then laying a layer of adhesive film on the installation interface area of ​​the auxiliary beam (404) and the foam core (402); finally, laying glass cloth on the contact surface between the auxiliary beam (404) and the petiole (401), installing the auxiliary beam (404) on the foam core (402), and performing a vacuum compaction treatment on it.

8. A method for preparing a wind tunnel blade according to claim 4 or 5, characterized in that: The specific process of installing the leading edge beam (403) in step 3) is as follows: receiving the leading edge beam (403), removing the preservation packaging of the leading edge beam (403) without removing the peeling cloth; performing a trial installation of the leading edge beam (403) and the foam core (402) at the installation interface of the leading edge beam (403) and the foam core (402), and then pasting a layer of adhesive film on the installation interface area of ​​the leading edge beam (403) and the foam core (402), and after installing the leading edge beam (403) on the foam core (402), packaging it and vacuuming it for pre-compaction treatment.

9. A method for preparing a wind tunnel blade according to claim 4 or 5, characterized in that: In step 3), the main beam (405) includes side beams laid on both sides of the foam core (402) and a cross beam connecting the side beams from the petiole (401), and a circular hole is formed on the cross beam to match the petiole (401); The thickness of the side sheet beam decreases in sequence along the axial direction from the blade root to the blade tip; The size of the ply cut pieces of the side beam decreases cyclically along the axial direction from the blade tip to the blade root; When laying the side beams, the bottom and top layers are laid in a whole manner, and the middle layer is laid in a transitional manner; when laying the cross beams, the shoulder of the petiole (401) is bypassed and laid continuously at the bottom of the "U"; The prepregs on both sides of the petiole (401) on the crossbeam are complete prepregs continuously laid from one side sheet beam to the other side sheet beam, and the prepregs on the crossbeam at the petiole (401) are prepregs of the sheet beams on both sides that are separately laid to the petiole (401); The layer laying sequence is 0° / +45° / 0° / 0° / 0° / -45° / 0°, and the width of the sheet in the +45° / -45° direction is 200mm-300mm.

10. A method for preparing a wind tunnel blade according to claim 4 or 5, characterized in that: Step 4) When the inner skin (406) is laid, the thickness of the inner skin (406) is 1.75 mm, and the material is T700 / E1302 unidirectional carbon fiber prepreg; the ply laying sequence of the inner skin (406) is +45° / 90° / -45° / 90° / -45° / 90° / +45° / +45° / 90° / -45° / 90° / -45° / 90° / +45°, for a total of 14 layers; the first layer and every 4 layers are subjected to vacuum compaction treatment until all the prepregs are laid. Finished; the width of the sheet in the +45° / -45° direction is 200mm-300mm, the overlap method is selected as butt joint, the butt joint interface is staggered, and an overlap of ≤5mm is allowed at the root and tip sections to ensure that the sheet is continuous and unbroken; the inner skin (406) prepreg sheet in the 90° laying direction is based on the trailing edge of the blade as the starting point, and is laid along the working surface, leading edge, and non-working surface to the trailing edge of the blade. For the root end surface and the tip end surface, separate laying is performed, and the sheet of the working surface and the non-working surface is widened, allowing an overlap of ≤5mm; Step 4) When laying the inner and outer skins (406), the outer skins (406) of the non-working surface and the outer skins (406) of the working surface are laid in the non-working surface and the coplanar blade molding mold cavity respectively. After the first layer and the layer laying are completed, vacuum compaction treatment is required; impurities on the surface of the blade core preform are cleaned by compressed air, and then the blade core preform is placed on the non-working surface mold cavity surface; Appropriate amount of foam glue is filled at both ends of the petiole (401) and the tip of the blade core preform.

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