Forming method for stress pressurizing section of S-shaped air inlet channel

Abstract

The invention discloses a forming method of a stress pressurizing section of an S-shaped air inlet channel in the technical field of airplanes. The forming method comprises the following steps: 1) taking out carbon fiber / epoxy resin prepreg; 2) cleaning the surface of the mold for later use; (3) blanking; (4) inner skin paving is conducted according to the layer paving sequence; 5) conveying the workpiece into an autoclave for curing, and unbagging after curing and cooling; (6) punching and then demolding; (7) the surface of the inner skin is polished and cleaned up; (8) foam is positioned, and cap-shaped ribs are laid; (9) conveying the workpiece into an autoclave for curing, and unbagging after curing and cooling; the method comprises the following steps of (1) preparing a digital model, (2) extracting the bottom surface of a honeycomb core according to the digital model, cutting the honeycomb core with the same size by using a blanking machine, and then cutting and chamfering, (11) positioning and pre-forming the honeycomb core, (12) paving an outer skin according to a layer paving sequence, and (13) feeding a workpiece into an autoclave for curing, and demolding after curing and cooling, thereby ensuring the internal quality, the molded surface and the mechanical property of the air inlet channel.

Description

Technical Field

[0001] The present invention relates to the technical field of composite products, and in particular to a method for forming an S-shaped air inlet structure segment. Background Art

[0002] Carbon fiber reinforced resin-based composite materials have the advantages of high strength, high modulus, light weight and strong designability. In recent years, carbon fiber composite structural parts have been widely used in aerospace, weapon equipment, aircraft and ships and other fields.

[0003] The air inlet is the flow channel through which the aircraft engine sucks in air. It is one of the five major components of an aircraft engine and a major component of the aircraft propulsion system. In recent years, many engineering designers have been continuously exploring how to design and manufacture air inlets with high structural strength and low weight.

[0004] According to different structural functions, the air intake duct is generally divided into 2-3 sections, such as the lip air intake section, the force-pressurized section, and the section connected to the engine. The so-called force-pressurized section, as the name implies, is a section that realizes the deceleration and pressurization of high-speed airflow and converts the kinetic energy of airflow into pressure energy. This means that it is also the section with the greatest impact intensity of airflow, so it puts forward higher requirements on the mechanical properties and aerodynamic appearance of the parts. In this case, the design and use of foam cap ribs and honeycomb cores not only improves the rigidity of the parts, but also meets the weight reduction requirements of the air intake duct components. However, due to the large curvature of the arc surface and the complex structure of the S-shaped air intake duct, it is difficult to form during the manufacturing process, and the foam and honeycomb core are prone to positioning deviation and debonding, which seriously affects the internal quality, surface and mechanical properties of the air intake duct. Therefore, it is more important to study the forming method of the S-shaped sandwich structure air intake duct with both foam and honeycomb core. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method for forming a stressed and pressurized section of an S-shaped air inlet, which solves the problems that the S-shaped air inlet is difficult to form during the manufacturing process due to its large arc curvature and complex structure, and that the foam and honeycomb core are prone to positioning deviation and debonding, thereby ensuring the internal quality, profile and mechanical properties of the air inlet.

[0006] The object of the present invention is achieved by: a molding method of an S-shaped air intake duct stress-bearing supercharging section, wherein the upper and lower half plates formed in one piece are spliced ​​and assembled with fasteners, and the half plates are both made of inner skin, foam, hat-shaped ribs, honeycomb core, and outer skin structure, and the molding method of the half plates comprises the following steps: Step 1) Take out the carbon fiber / epoxy resin prepreg from the cold storage and cool it to room temperature for later use; Step 2) Clean the mold surface and set aside; Step 3) Use the automatic cutting machine to cut materials according to the designed layer diagram; Step 4) Lay the inner skin according to the laying order; Step 5) Send the product into the autoclave for curing, and unpack it after curing and cooling; Step 6) Install a drilling jig on the mold to flanging and punch holes in the workpiece, and then demold it; Step 7) Grind the inner skin surface and clean it; Step 8) Position the foam and lay the cap-shaped ribs. Use laser projection and pallet to help locate the foam position. The specific operations are as follows: first wrap the foam with film, vacuum and compact for 14-16 minutes, then use the laser projector to locate the foam position, and lay a layer of film on the projection area. The laying area needs to be expanded by 15-20mm, pre-pump for 14-16 minutes, then place the foam in sequence according to the projection position of the foam, install the foam positioning pallet on the mold tooling in sequence, check the fit with the foam under laser projection, and after confirming that the position is correct, remove the pallet and make bags. After bag making, install the pallet again, then connect the vacuum to sort the pre-pumped bags, and place the foam in the mold. Pre-pumping and compacting are performed for more than 30 minutes while being fixed by the positioning pallet. After pre-pumping, the pallet is removed, the vacuum bag is opened, the projection is turned on, and the foam position is checked. If the position is not offset, the next step of laying is started. Otherwise, the foam needs to be pried open and repositioned and bonded according to the above method. In addition, for gaps that cannot be compacted, fill them with adhesive film and then pre-pump for 14-16 minutes until there is no gap between the foam and the inner skin. For foam tears and edge corners, fill them with foam glue and then pre-pump for 14-16 minutes. After the foam is positioned, use carbon twisted wire to roll into 1-3mm thin strips and fill them between the foam and the inner skin. Then, the hat-shaped reinforcement pieces are laid according to the laying order and the bag making is completed. Step 9) Send the product into the autoclave for curing, and unpack it after curing and cooling; Step 10) Extract the bottom surface of the honeycomb core according to the digital model, use a blanking machine to cut the honeycomb core of the same size, and then cut and chamfer; Step 11) Positioning and preforming the honeycomb core; Step 12) Lay the outer skin according to the laying order; Step 13) The product is sent into the autoclave for curing. After curing and cooling, demoulding and subsequent cutting, punching and inspection are carried out.

[0007] Furthermore, step 10) specifically includes: according to the direction and size of the honeycomb core in the digital model, using a blanking machine to cut out a demoulding cloth of the same size, cutting out the honeycomb core according to the demoulding cloth, then sticking the demoulding cloth on a hard pad, cutting out a pad of a corresponding shape, gluing the pad around and sticking the honeycomb core thereon, grinding the edge of the honeycomb core according to the chamfer angle required by the honeycomb core in the digital model, measuring the angle of the honeycomb core while grinding, ensuring that the angle deviation is controlled within ±3°, and after the chamfering of the honeycomb core is completed, cleaning the pores; and cleaning the surface of the honeycomb core, wrapping the honeycomb core with a peelable cloth and a breathable felt in turn, placing it in an oven at 70±5°C for 1h, then sealing the honeycomb core in a sealed bag, and transporting it to a clean room for use.

[0008] Furthermore, step 11) specifically includes: laying a layer of special adhesive film between the inner skin and the honeycomb core, laying corresponding special adhesive films in other areas, overlapping the adhesive films by 2-4 mm, and then vacuuming and compacting for 14-16 minutes, then placing the honeycomb core on the adhesive film, using foam glue to bond the honeycomb core joints, trimming and aligning the seams, filling the gaps that cannot be compacted with adhesive film and then pre-evacuating for 14-16 minutes until there is no gap between the honeycomb core and the inner skin, and filling the torn and edge-notched areas of the honeycomb core with foam glue and then pre-evacuating for 14-16 minutes; then putting the product into the can for pre-forming the honeycomb core, and after taking it out of the can and unpacking the bag, use an air grinder to grind the honeycomb core and the area where the foam glue protrudes from the hat-shaped ribs to make it flush and smooth, and fill the concave area between the honeycomb core and the hat-shaped ribs with foam glue again to pre-form, so that the honeycomb core and the hat-shaped ribs are basically smooth and have no height difference.

[0009] Furthermore, step 4) specifically includes: firstly, laying a sacrificial layer at the flange position, followed by pre-drawing, and then laying the cut prepreg in the effective area of ​​the mold according to the laying order, laying ratio and laying direction. The first layer of fabric is pre-drawn for 14-16 minutes after laying, and prefabricated carbon twisted wires are placed at the right angles of the flanges at both ends and the R corners on both sides for transition. When the twisted wire length is not enough, it can be overlapped; the overlap width of the first layer of fabric is 20mm. In addition to laying and compacting the first layer of prepreg once, vacuum compaction is performed once after laying four layers of prepreg, and each compaction takes more than 15 minutes. After the material piece is half laid, cold pressing and pre-compacting is performed.

[0010] Further, the curing process of step 9) and step 13) is as follows: Evacuate at room temperature, the vacuum degree is not less than 0.092MPa, and solidify in the tank after passing the cold pressure test; Heat up to 125±5℃ at room temperature, with a heating rate of 1.0-2.0℃ / min, and the medium temperature is set to 130℃. When the fastest heating thermocouple reaches 40℃, start pressurizing until it reaches 0.2MPa and then maintain the pressure. When the slowest thermocouple is heated to 120℃, keep it warm for 120min-130min; Cool down to below 80℃ at a rate of no more than 2℃ / min and then release the pressure. When the temperature of the fastest cooling thermocouple drops below 60℃, open the can.

[0011] Furthermore, step 12) specifically includes: laying the outer skin according to the design requirements, pre-extracting for 14-16 minutes after the first layer is laid, and then laying the next layer, and finally laying a layer of Tedlar waterproof membrane on the honeycomb core area, overlapping 2-4mm, pre-extracting time more than 2h, overlapping the outer skin sheets, overlapping length of 24-26mm, and staggering the seam positions layer by layer.

[0012] The present invention is mainly to successfully realize the related process operations which are more difficult in the process of manufacturing the segment layer of the foam + honeycomb core sandwich structure. The specific principle is as follows: Due to the large curvature of the inlet profile and the large ply area, as the number of sheet layers increases, the effect of the simple vacuum pump (≤0.1Mpa) pressure will be greatly weakened, and there may still be bridges and wrinkles between the layers in these areas. The cold pressing pre-curing method is to place the workpiece in an autoclave, apply a pressure of ≥0.1MPa at low or normal temperature, and use high pressure to assist in compacting the sheet that the vacuum pump cannot compact. In addition, because the autoclave applies a large pressure, the R corners and bends can be filled with raw silicone to reduce the risk of bag explosion.

[0013] The use of carbon twisted wire can avoid the formation of bridges at the R corners due to difficulty in laying in the subsequent layering process. After the first layer of plain fabric with good ductility and easy laying is laid, the prepreg carbon twisted wire obtained by pressing according to different R angles is first used with a special twisting tool to fill the surrounding R area, so that the material can be laid in such areas smoothly, improving the layering operability and reducing the risk of bridging and delamination in the R corner area.

[0014] Since the position of the intake duct foam not only affects the mechanical strength of the intake duct and the docking of the upper and lower foam ribs, but also the area outside the hat-shaped ribs is a honeycomb core, the offset of the foam will directly affect the size and position of the honeycomb core, so the accuracy of the foam position is very important; this process uses laser projection + card board assistance to locate the foam position, which can perform two-way benchmark verification and verify the position offset before and after pre-evacuation.

[0015] After the hat-shaped ribs are formed, their flanges will form a variable thickness layer loss area on the skin, which will cause the honeycomb core placed between the hat-shaped ribs to have the problem of protruding on the four sides. In this case, the protruding honeycomb core needs to be cut flat. If the honeycomb core is processed from the bottom, due to the large curvature of the air inlet surface, the large number of hat-shaped ribs, and the different R angles of the flanges after forming, the chamfering and adaptation work one by one is difficult and time-consuming. In addition, after chamfering, the gap between the bottom surface of the honeycomb core and the skin and hat-shaped ribs may be too large, or multiple bonding checks may be required, otherwise the product will have a low bonding strength. The method of preforming the honeycomb core with the front chamfer transition can be processed according to the specific conditions of the upper surface after the honeycomb core is preformed. For the areas where the honeycomb core is protruding, the foam glue overflows, and the vacant areas are repaired more and supplemented less, so that the honeycomb core and the hat-shaped ribs are basically smooth and have no height difference, ensuring the surface flatness of the outer skin paving surface, reducing the risk of honeycomb core debonding, and ensuring the outer surface of the outer skin.

[0016] In addition, when this section is assembled with the next section of the air intake, the glued assembly area will be repaired and polished, which will cause fiber breakage and affect the strength, and also affect the internal aerodynamic surface. In the early layer design and mold design, a sacrificial layer design and mold milling surface processing compensation are specially added to the later polishing area to ensure that there is no step difference between the internal surface of the air intake lip section of the air intake after polishing and the next section after assembly.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1) The inner skin forming, hat-shaped rib forming, honeycomb core + outer skin one-time forming method is adopted to ensure the precise positioning of the foam, the bonding strength of the honeycomb core and the skin, and the mechanical properties of the parts, while effectively reducing the weight of the product, improving production efficiency and saving production costs; 2) The autoclave process is used to reduce the porosity of the composite material and improve its structural strength; 3) Use the cold pressing pre-curing method to pre-compact the product at a certain thickness for each layer, so as to avoid the situation that the prepreg is laid too thick at one time, which may lead to uncompacted parts, wrinkles, bridges, and uncured internal resin, so as to ensure the internal quality of the parts; 4) Use carbon twisted wire to fill the right-angle area of ​​the flange, so that the material can be laid smoothly in the right-angle area, improve the laying operation, and reduce the risk of bridging and delamination in the right-angle area; 5) The foam positioning method combining laser projection and pallet fixture fixation is adopted to accurately position the foam, avoiding the mechanical strength of the air intake duct caused by foam deviation, the docking of the upper and lower foam ribs, and the size and position offset of the honeycomb core in the area outside the hat-shaped ribs.

[0018] 6) When placing the honeycomb core between the skin and the hat-shaped ribs, the pre-curing + front chamfering transition method is used to solve the problem that the variable thickness area formed after the hat-shaped ribs are formed makes the four sides of the honeycomb core higher after placement. This avoids the problem of chamfering the bottom of the honeycomb core one by one and the gap between the bottom of the honeycomb core and the skin and the hat-shaped ribs after chamfering, which leads to low bonding strength of the parts or the need for multiple bonding checks. While ensuring the molding quality, it reduces the difficulty of operation, improves production efficiency and saves production costs; 7) In order to avoid fiber breakage caused by grinding when this section is assembled with other sections, which in turn affects the strength, a sacrificial layer area is added to the later grinding area during the layer design, and milling compensation is performed at the corresponding position of the mold to ensure that there is no step difference between the internal surface of this section after grinding and after assembly with the front and rear sections. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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.

[0020] Figure 1 It is a flow chart of the present invention.

[0021] Figure 2 It is a schematic diagram of the structure of the force-bearing and pressurizing section of the S-shaped air inlet in the present invention.

[0022] Figure 3 It is an exploded view of the upper half plate in the present invention.

[0023] Figure 4 This is a schematic diagram after the inner skin of the present invention is paved.

[0024] Figure 5 This is a schematic diagram of the laser positioning of the foam installation of the present invention.

[0025] Figure 6 This is a schematic diagram of the foam laser projection + pallet auxiliary mold in the present invention.

[0026] Figure 7 It is a schematic diagram of the structure of the pallet auxiliary mold in the present invention.

[0027] Figure 8 It is a schematic diagram of pre-drawing with a card board in the present invention.

[0028] Fig. 9 for Figure 4 Schematic diagram of foam installed in the middle.

[0029] Fig.10 for Figure 5Schematic diagram of the cap-shaped rib on the middle installation.

[0030] Fig.11 This is a schematic diagram of the honeycomb core of the present invention after positioning.

[0031] Fig.12 Schematic diagram of the honeycomb core before and after polishing in the present invention.

[0032] Fig.13 for Figure 6 Schematic diagram of the honeycomb core installed in the middle.

[0033] Fig.14 This is a schematic diagram of the upper half plate after curing prepared by the present invention.

[0034] Among them, 100 is the upper half plate, 101 is the inner skin, 102 is the foam, 103 is the hat-shaped rib, 104 is the honeycomb core, 105 is the outer skin, 200 is the lower half plate, and 300 is the pallet auxiliary mold. DETAILED DESCRIPTION

[0035] 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.

[0036] like Figure 2-3 The figure shows an S-shaped air inlet force-bearing pressurized section, including an upper half plate 100 and a lower half plate 200, which are assembled with fasteners after splicing, and an S-shaped air inlet is formed between the upper half plate 100 and the lower half plate 200. The internal structure of the upper half plate 100 and the lower half plate 200 is the same, and both adopt an inner skin 101, foam 102, hat-shaped ribs 103, honeycomb core 104, and outer skin 105 structure.

[0037] Since the upper half plate 100 and the lower half plate 200 have the same structure, the upper half plate 100 is taken as an example to explain the molding process. Figure 1 As shown, the following steps are included: 1) Picking materials Take out the carbon fiber / epoxy resin prepreg from the cold storage and cool it to room temperature before use.

[0038] 2) Mold processing Pour anhydrous ethanol onto a clean wipe or rag, and wipe off dust, particles, and other excess materials that affect the surface quality of the mold, keeping the mold surface smooth and clean. Confirm that the tooling surface is not damaged, and the tooling cutting lines, margin lines, coordinate system and other engraved lines are clearly visible. Apply the release agent on the work surface three times, with an interval of 15 minutes each time. After the construction is completed, dry it at room temperature for at least 30 minutes.

[0039] 3) Prepreg cutting The inlet profile is made by using Catia and Fibersim software. According to the principle that the joints of the layers in the same direction should be staggered by at least 25mm, each layer of the sheet is segmented, coded, and sorted using CAD drawing software to make a blanking diagram. The blanking diagram is imported into the automatic blanking machine to accurately cut the sheet, and the sheet angle can be guaranteed to be within 0.5°. After cutting, the sheets are arranged in the order of the layers, and the sheets are checked to see if they are complete and undamaged.

[0040] 4) Preparation of twisted yarn The prepreg and the film are cut into narrow strips with a width of 24 mm, and the two are first pasted together and rolled into thin round strips. Then they are put into the twisting tool and a pressure of 10 MPa is applied on the press at room temperature to compact the prepreg and twist the yarn for 30 minutes.

[0041] 5) Prepreg laying First, lay the sacrificial layer at the turning position and then pre-draw for 15 minutes. Then, lay the cut prepreg in the effective area of ​​the mold according to the laying order, laying ratio, laying direction, etc. After the first layer of fabric is laid, pre-draw for 15 minutes, and prefabricated R5 carbon twisted wire is placed at the right angles of the two ends and the R angles on both sides for transition. If the twisted wire length is not enough, it can be overlapped.

[0042] Note that the overlap width of the first layer of fabric is 20mm (in order to reduce the gap between each layer of prepreg as much as possible, in addition to the first layer of prepreg being laid and compacted once, vacuum compaction is performed once after every four layers of prepreg are laid, and each compaction lasts for more than 15 minutes. In order to enhance the compaction effect, cold pressing is performed for pre-compaction after the sheet is halfway laid.

[0043] 6) Packaging After the prepreg is laid, the auxiliary materials are packaged according to the figure below.

[0044] 7) Curing Transfer the mold to the effective temperature area of ​​the autoclave. After the leak test is qualified, cure according to the following curing parameters: ①Evacuate at room temperature, the vacuum degree is not less than 0.092MPa, and solidify in the tank after passing the cold pressure test; ②Heat up to 125±5℃ at room temperature, with a heating rate of 1.0-2.0℃ / min, and the medium temperature is set to 130℃. When the fastest heating thermocouple rises to 40℃, start pressurizing until it reaches 0.6MPa and then maintain the pressure. ③When the slowest thermocouple is heated to 120℃, keep it warm for 120min-130min; ④Relieve the pressure after cooling to below 80℃ at a rate of no more than 2℃ / min. When the temperature of the fastest cooling thermocouple drops below 60℃, the can can be opened to complete the curing of the parts.

[0045] 8) Unpacking the bag When the mold temperature needs to be cooled to room temperature, the bag removal process can be carried out. Open the vacuum bag and remove the auxiliary materials on the surface of the part, including breathable felt, isolation film, peelable cloth, etc. Be careful when cleaning the peelable cloth and do not tear the surface fibers.

[0046] 9) Design position holes Place the unpacked workpiece together with the mold on the drilling jig, check whether the position of the drilling jig and the workpiece is accurate after installation, and then drill holes at the flange positions on both sides.

[0047] 10) Inner skin 101 treatment Use 50-180 mesh sandpaper to grind the outer surface of the entire air inlet inner skin 101 to increase its roughness and enhance the bonding strength. The inner skin 101 obtained is as follows: Figure 4 shown.

[0048] 11) Foam 102 treatment First, use compressed air to clean the stains and other excess materials on the surface of foam 102. Then use a clean wiping paper dipped in anhydrous ethanol to clean the surface of foam 102. After drying for 10 minutes, wrap foam 102 with peeling cloth and breathable felt in turn, place it in an oven at 70°C, and dry it for 1 hour. Record the equipment code, drying temperature, insulation start time, and insulation end time. After the foam 102 is dried, wrap and seal the foam 102 with breathable felt and a sealing bag, take it out of the oven, send it to the clean room, remove the sealing bag and breathable felt outside the foam 102, and use pressure-sensitive tape to remove the breathable felt lint for later use.

[0049] 12) Foam 102 positioning Since the position of the foam 102 not only affects the mechanical strength of the air inlet and the connection between the upper and lower foam 102 ribs, but also the area outside the hat-shaped rib 103 is the honeycomb core 104, the deviation of the foam 102 will directly affect the size and position of the honeycomb core 104, the accuracy of the position of the foam 102 is very important.

[0050] The process uses laser projection + cardboard auxiliary mold 300 to locate the position of the foam 102, and the specific operation is as follows: like Figure 5-8As shown, first wrap the foam 102 with a film, vacuum and compact for 15 minutes, then use a laser projector to locate the position of the hat-shaped rib 103, and lay a layer of film in the projection area. The laying area needs to be expanded by 15-20mm, pre-pump for 15 minutes, and then place the foam 102 in sequence according to the projection position of the foam 102. Install the foam 102 positioning card on the mold tooling in sequence, and check the fit with the foam 102 under the laser projection. After confirming that the position is correct, remove the card and make the bag. After the bag making is completed, install the card again, then connect the vacuum, organize the pre-pumped bag, and pre-pump and compact for more than 30 minutes when the foam 102 is fixed by the positioning card. After the pre-pumping, remove the card, open the vacuum bag, turn on the projection, and check the position of the foam 102. If the position is offset, start the next layering, otherwise, pry open the foam 102 and reposition and bond it according to the above method. In addition, for the gaps that cannot be compacted, use adhesive film to fill them and then pre-pump for 15 minutes until there is no gap between the foam 102 and the inner skin 101; for the tearing of the foam 102 and the edge of the missing corner (within the inspection requirements), use foam glue to fill them and then pre-pump for 15 minutes. After the foam 102 is positioned, Fig. 9 shown.

[0051] 13) Hat-shaped rib 103 forming After the foam 102 is positioned, a carbon twisted wire is rolled into a thin strip of about 2 mm and filled between the foam 102 and the inner skin 101. Subsequently, the hat-shaped rib 103 sheet is laid in the order of layering and the bag is made. After the hat-shaped rib 103 is laid, Fig.10 shown.

[0052] 14) Curing The mold is transferred to the effective temperature area of ​​the autoclave. After the leak test is qualified, the part is cured according to the following parameters: ①Evacuate at room temperature, the vacuum degree is not less than 0.092MPa, and solidify in the tank after passing the cold pressure test; ②Heat up to 125±5℃ at room temperature, with a heating rate of 1.0-2.0℃ / min, and the medium temperature is set to 130℃. When the fastest heating thermocouple rises to 40℃, start pressurizing until it reaches 0.2MPa and then maintain the pressure. ③When the slowest thermocouple is heated to 120℃, keep it warm for 120min-130min; ④ Cool down to below 80℃ at a rate of no more than 2℃ / min and then release the pressure. When the fastest thermocouple temperature drops below 60℃, the can can be opened. 15) Honeycomb core 104 processing According to the direction and size of the honeycomb core 104 in the digital model, a stripping cloth of the same size is cut out using a blanking machine, and the honeycomb core 104 is cut out according to the stripping cloth. Then the stripping cloth is pasted on a hard pad, and the pad of the corresponding shape is cut out. Double-sided tape is pasted around the pad and the honeycomb core 104 is pasted on it. According to the chamfer angle required by the honeycomb core 104 in the digital model, the edge of the honeycomb core 104 is polished by a grinder, and the angle of the honeycomb core 104 is measured with an angle ruler while polishing to ensure that the angle deviation is controlled within ±3° to meet the design requirements (±5°). After the chamfering of the honeycomb core 104 is completed, the debris, particles and other excess materials in the pores are cleaned with compressed air, and the surface of the honeycomb core 104 is cleaned with a clean rag dipped in anhydrous ethanol, and the honeycomb core 104 is wrapped with a peelable cloth and a breathable felt in turn, and placed in an oven at 70±5℃ for 1h, and then the honeycomb core 104 is placed in a sealed bag and sealed, and transported to a clean room.

[0053] 16) Honeycomb core 104 pasting and positioning Lay a layer of skin and core material bonding film between the inner skin 101 and the honeycomb core 104, and lay skin and prepreg bonding film in other areas. The film overlaps 2-4mm, then vacuum and compact for 15 minutes, and then place the honeycomb core 104 on the film. Use foam glue to bond the joints of the honeycomb core 104, and trim and align the seams. For gaps that cannot be compacted, fill them with film and pre-pump for 15 minutes until there is no gap between the honeycomb core 104 and the inner skin 101. For torn honeycomb core 104 and edge notches (within the inspection requirements), use foam glue to fill them and pre-pump for 15 minutes. Fig.11 shown.

[0054] 17) Honeycomb core 104 preforming The workpiece is put into the can for preforming the honeycomb core 104. After the can is unpacked, the honeycomb core 104 and the area where the foamed glue is higher than the hat-shaped rib 103 are polished and smoothed by an air grinder. Fig.12 As shown. For the concave part between the honeycomb core 104 and the hat-shaped rib 103, the foam glue preform is filled again to make the honeycomb core 104 and the hat-shaped rib 103 basically smooth and without height difference. After the honeycomb core 104 is laid, the thickness is as shown. Fig.13 shown.

[0055] 18) Outer skin 105 paving The outer skin 105 is laid according to the design requirements. After the first layer is laid, a pre-extraction is performed for 15 minutes, and then the next layer is laid. Finally, a layer of Tedlar waterproof membrane is laid on the honeycomb core 104 area, with an overlap of 2-4mm. The pre-extraction time is more than 2 hours. The outer skin 105 sheets are overlapped, with an overlap length of 25mm, and the joint positions need to be staggered layer by layer.

[0056] 19) Curing The mold is transferred to the effective temperature area of ​​the autoclave. After the leak test is qualified, the part is cured according to the following parameters: ①Evacuate at room temperature, the vacuum degree is not less than 0.092MPa, and solidify in the tank after passing the cold pressure test; ②Heat up to 125±5℃ at room temperature, with a heating rate of 1.0-2.0℃ / min, and the medium temperature is set to 130℃. When the fastest heating thermocouple rises to 40℃, start pressurizing until it reaches 0.2MPa and then maintain the pressure. ③When the slowest thermocouple is heated to 120℃, keep it warm for 120min-130min; ④ Cool down to below 80℃ at a rate of no more than 2℃ / min and then release the pressure. When the fastest cooling thermocouple temperature drops below 60℃, the can can be opened. Fig.14 shown.

[0057] Finally, the solidified and cooled parts are demoulded and subsequently cut, punched and inspected.

[0058] Pay special attention that when making holes in composite parts, the back side needs to be supported with a wooden block (or bakelite block) or other methods should be adopted to prevent delamination at the hole exit.

[0059] 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 method for forming an S-shaped air intake duct pressure-bearing supercharging section, wherein the upper and lower half plates formed in one piece are spliced ​​and assembled with fasteners, wherein the half plates are both constructed with an inner skin (101), foam (102), hat-shaped ribs (103), a honeycomb core (104), and an outer skin (105) structure, wherein: The forming method of the half plate comprises the following steps: Step 1) Take out the carbon fiber / epoxy resin prepreg from the cold storage and cool it to room temperature for later use; Step 2) Clean the mold surface and set aside; Step 3) Use the automatic cutting machine to cut materials according to the designed layer diagram; Step 4) Laying the inner skin (101) according to the laying order; Step 5) Send the product into the autoclave for curing, and unpack it after curing and cooling; Step 6) Install a drilling jig on the mold to flanging and punch holes in the workpiece, and then demold it; Step 7) Grind the surface of the inner skin (101) and clean it; Step 8) Position the foam (102) and lay the cap-shaped rib (103). Use laser projection and a pallet to assist in positioning the foam (102). The specific operation is as follows: first, wrap the foam (102) with a film, vacuum and compact for 14-16 minutes, then use a laser projector to locate the foam (102), and lay a layer of film on the projection area. The laying area needs to be expanded by 15-20 mm, and pre-pump for 14-16 minutes. Then, place the foam (102) in sequence according to the projection position of the foam (102), and install the foam (102) positioning pallets on the mold tooling in sequence. Check the fit with the foam (102) under laser projection. After confirming that the position is correct, remove the pallet and make bags. After bag making is completed, install the pallet again, and then connect the vacuum to arrange the pre-pumped bags. 2) Pre-pumping and compacting for more than 30 minutes while being fixed by a positioning card; after pre-pumping, remove the card, open the vacuum bag, open the projection, check the position of the foam (102), and if the position is not offset, start the next step of laying; otherwise, pry open the foam (102), reposition and bond according to the above method, and in addition, fill the gaps that cannot be compacted with adhesive film and then pre-pump for 14-16 minutes until there is no gap between the foam (102) and the inner skin (101); fill the torn and edge-notched parts of the foam (102) with foam glue and then pre-pump for 14-16 minutes; after the foam (102) is positioned, use carbon twisted wire to roll into 1-3 mm thin strips and fill them between the foam (102) and the inner skin (101), and then lay the cap-shaped rib (103) sheet according to the laying order and complete the bag making; Step 9) Send the product into the autoclave for curing, and unpack it after curing and cooling; Step 10) extracting the bottom surface of the honeycomb core (104) according to the digital model, using a blanking machine to cut the honeycomb core (104) of the same size, and then cutting and chamfering; Step 11) Positioning and preforming the honeycomb core (104); Step 12) Laying the outer skin (105) according to the laying order; Step 13) The product is sent into the autoclave for curing. After curing and cooling, demoulding and subsequent cutting, punching and inspection are carried out.

2. The method for forming an S-shaped air intake duct pressure boosting section according to claim 1, characterized in that: Step 10) specifically includes: according to the direction of the honeycomb core (104) in the digital model and the size of the honeycomb core (104), using a blanking machine to cut out a demoulding cloth of the same size, cutting out the honeycomb core (104) according to the demoulding cloth, then pasting the demoulding cloth on a hard pad, cutting out a pad of a corresponding shape, gluing the pad around and pasting the honeycomb core (104) thereon, grinding the edge of the honeycomb core (104) according to the chamfer angle required by the honeycomb core (104) in the digital model, measuring the angle of the honeycomb core (104) while grinding, ensuring that the angle deviation is controlled within ±3°, and after the honeycomb core (104) is chamfered, cleaning the cells; and cleaning the surface of the honeycomb core (104), wrapping the honeycomb core (104) with a peelable cloth and a breathable felt in turn, placing it in an oven at 70±5°C for 1 hour, then placing the honeycomb core (104) in a sealed bag, sealing it, and transporting it to a clean room for use.

3. A method for forming an S-shaped air intake duct pressure boosting section according to claim 1 or 2, characterized in that: Step 11) specifically includes: laying a layer of special adhesive film between the inner skin (101) and the honeycomb core (104), laying corresponding special adhesive films in other areas, overlapping the adhesive films by 2-4 mm, and then vacuuming and compacting for 14-16 minutes, then placing the honeycomb core (104) on the adhesive film, using foam glue to bond the joints of the honeycomb core (104), trimming and aligning the seams, filling the gaps that cannot be compacted with adhesive film, and then pre-evacuating for 14-16 minutes until the honeycomb core (104) and the inner skin (101) are connected. ), the torn and edge-notched areas of the honeycomb core (104) are filled with foam glue and then pre-extracted for 14-16 minutes; then the product is put into a can for pre-forming the honeycomb core (104), and after it is taken out of the can and unpacked, the honeycomb core (104) and the area where the foam glue protrudes from the hat-shaped rib (103) are polished and smoothed with an air grinder, and the concave area between the honeycomb core (104) and the hat-shaped rib (103) is filled with foam glue again for pre-forming, so that the honeycomb core (104) and the hat-shaped rib (103) are basically smooth and have no height difference.

4. A method for forming an S-shaped air intake duct pressure boosting section according to claim 1 or 2, characterized in that: Step 4) specifically includes: firstly, laying a sacrificial layer at the flange position, followed by pre-drawing, and then laying the cut prepreg in the effective area of ​​the mold according to the laying order, laying ratio and laying direction. After the first layer of fabric is laid, pre-drawing is carried out for 14-16 minutes. Prefabricated carbon twisted wires are placed at the right angles of the flanges at both ends and the R angles on both sides for transition. When the twisted wire length is not enough, it can be overlapped; the overlap width of the first layer of fabric is 20mm. In addition to laying and compacting the first layer of prepreg once, vacuum compaction is carried out once after laying four layers of prepreg, and each compaction takes more than 15 minutes. After the material piece is laid to half, cold pressing and pre-compacting is carried out.

5. A method for forming an S-shaped air intake duct pressure boosting section according to claim 1 or 2, characterized in that: The curing process of step 9) and step 13) is as follows: Evacuate at room temperature, the vacuum degree is not less than 0.092MPa, and solidify in the tank after passing the cold pressure test; Heat up to 125±5℃ at room temperature, with a heating rate of 1.0-2.0℃ / min, and the medium temperature is set to 130℃. When the fastest heating thermocouple reaches 40℃, start pressurizing until it reaches 0.2MPa and then maintain the pressure. When the slowest thermocouple reaches 120℃, keep it warm for 120min-130min; After cooling to below 80°C at a rate no greater than 2°C / min, release the pressure. When the fastest cooling thermocouple temperature drops below 60°C, open the can.

6. A method for forming an S-shaped air intake duct pressure boosting section according to claim 1 or 2, characterized in that: Step 12) specifically includes: laying the outer skin (105) according to the design requirements, performing a pre-extraction for 14-16 minutes after the first layer is laid, and then laying the next layer, and finally laying a layer of Tedlar waterproof membrane on the honeycomb core (104) area, overlapping by 2-4 mm, and pre-extraction time of more than 2 hours. The outer skin (105) sheets are overlapped, the overlap length is 24-26 mm, and the seam positions are staggered layer by layer.

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