CN108943769B - Manufacturing method of non-equal-diameter closed square tubular carbon fiber beam structural part of unmanned aerial vehicle - Google Patents
Manufacturing method of non-equal-diameter closed square tubular carbon fiber beam structural part of unmanned aerial vehicle Download PDFInfo
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- CN108943769B CN108943769B CN201810640505.2A CN201810640505A CN108943769B CN 108943769 B CN108943769 B CN 108943769B CN 201810640505 A CN201810640505 A CN 201810640505A CN 108943769 B CN108943769 B CN 108943769B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/28—Shaping operations therefor
- B29C70/40—Shaping or impregnating by compression not applied
- B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
- B29C70/44—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
- B29C33/3842—Manufacturing moulds, e.g. shaping the mould surface by machining
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/28—Shaping operations therefor
- B29C70/54—Component parts, details or accessories; Auxiliary operations, e.g. feeding or storage of prepregs or SMC after impregnation or during ageing
- B29C70/543—Fixing the position or configuration of fibrous reinforcements before or during moulding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/28—Shaping operations therefor
- B29C70/54—Component parts, details or accessories; Auxiliary operations, e.g. feeding or storage of prepregs or SMC after impregnation or during ageing
- B29C70/545—Perforating, cutting or machining during or after moulding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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Abstract
The invention relates to a method for manufacturing a non-equal-diameter closed square tubular carbon fiber beam structural part of an unmanned aerial vehicle. The integral forming tool is effectively simplified, the forming process is simplified, and the product performance and the size stability of the integral forming are ensured.
Description
Technical Field
The invention belongs to the technical field of unmanned aerial vehicle composite material forming processes, and relates to a manufacturing process of a non-constant-diameter closed square tubular carbon fiber beam structural part of a small and medium-sized unmanned aerial vehicle.
Background
Unmanned aerial vehicle combined material roof beam structural style is various, and its shaping mode also has respectively different. Compared with the traditional linear composite beam structure, the complex non-constant-diameter closed square tubular beam structure has the advantages that the internal structural layout of the fuselage and the wings can be better arranged, the internal structure of the airframe is optimized, and the load distribution is effectively carried out, so that the space utilization rate is high, the shape following performance is good, and the complex non-constant-diameter closed square tubular beam structure is particularly suitable for a medium-small high-performance unmanned aerial vehicle airframe structure with the layout of a wing-body fusion body; the integral forming process has high requirements on forming process and tools, the product is difficult to demould, and in order to obtain a high-quality complex beam structure product meeting the design requirements, a better forming scheme is to use the combination of a core mould and a female mould with good demoulding effect to carry out compression molding.
Chinese patent publication No. CN 106182805A discloses "a manufacturing process of a carbon fiber composite material equal-diameter tubular structure", and proposes that a combined core mold of a metal rod and flexible rubber is used to realize thermal expansion compression molding on a combined female mold through non-autoclave molding. The method is suitable for manufacturing the equal-diameter tubular carbon fiber part with a larger pipe diameter, is difficult to be suitable for manufacturing the complex closed square tubular beam part, and has the problems of difficult demoulding of metal rods and silicon rubber core moulds, short service life of the core moulds and the like.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a method for manufacturing a non-isodiametric closed square tubular carbon fiber beam structural part of a small and medium-sized unmanned aerial vehicle, which solves the problem that the forming application of the non-isodiametric closed square tubular carbon fiber beam structural part is limited, optimizes the internal structural layout of an unmanned aerial vehicle body, improves the operability and the demolding property in the product forming process, and improves the process application range of integrally forming a small and medium-sized complex structural part, so that the method can be suitable for manufacturing the isodiametric closed square tubular carbon fiber composite beam structural part and can also be used for manufacturing the non-isodiametric closed square tubular carbon fiber composite beam structure.
Technical scheme
A manufacturing method of a non-equal-diameter closed square tubular carbon fiber beam structural part of an unmanned aerial vehicle is characterized by comprising the following steps:
step 1: manufacturing of the integral air bag forming die:
adopting CATIA software to carry out three-dimensional modeling and optimized design of the integral air bag forming die, and carrying out die processing on the optimized digital model; the integral air bag forming die is divided into a lower female die (1) and an upper female die (2), the lower female die (1) and the upper female die (2) are connected through a positioning pin and a bolt, a cavity is formed in the middle after combination, and the shape of the cavity is consistent with that of a non-equal-diameter closed square tubular carbon fiber beam structural workpiece of the unmanned aerial vehicle to be processed; metal baffles are arranged at two ends of the integral air bag forming die and used for sealing the cavity; the baffles at two ends are respectively connected with the end faces of the lower female die (1) and the upper female die (2) in a positioning way through bolts, and the baffle at one end is provided with an inflation joint and a deflation joint;
step 2: production of balloon core mold (3):
step 2 a: sequentially smearing hole sealing agents and water-soluble release agents on the inner surfaces of the lower female die (1) and the upper female die (2) respectively, airing for 15min, paving single-layer sheet glass cloth fabric prepreg with the thickness of 0.1mm on the inner surfaces of the lower female die (1) and the upper female die (2) layer by layer until a preformed body with the thickness equal to that of a product is formed, and performing vacuum pre-compaction in the paving process to enable the prepreg to be tightly attached; paving aporate barrier film, air felt and vacuum bag on the preforming body in proper order, forming the airtight system of vacuum through the adhesion of sealing tape, will contain lower bed die (1) and last bed die (2) of preforming body and place in vacuum curing oven and solidify: firstly, heating at a heating rate of 1-3 ℃/min until the constant temperature of 120 ℃ is reached, and keeping the temperature for 1 hour; cooling at a cooling rate of 3 ℃/min until the temperature is below 55 ℃, and discharging to obtain an upper rigid prosthesis and a lower rigid prosthesis; vacuumizing in the whole curing process, wherein the vacuum degree is required to be more than 0.08 MPa;
and step 2 b: respectively paving and sticking 1 layer of tooling demolding cloth on the inner surfaces of the upper and lower rigid prostheses, and then respectively paving and sticking silicon rubber sheets on the tooling demolding cloth to form a silicon rubber layer; then closing the silicon-containing rubber layer, the lower female die (1) and the upper female die (2) of the rigid prosthesis, installing metal baffles at two ends, and embedding a joint into the silicon rubber layer on the baffle at one end to form a closed assembly containing a cavity; filling nitrogen into the cavity through the gas filling and discharging joint, and maintaining the pressure at 0.4 Mpa; and (3) carrying out air tightness detection on the interior of the cavity, and when the leakage pressure within 5 minutes is not more than 0.017MPa, putting the combined body into a vacuum curing furnace for vulcanization: firstly, heating at the heating rate of 1-3 ℃/min until the constant temperature of 180 ℃ is reached, and preserving heat for 2 hours; cooling at the cooling rate of 3 ℃/min until the temperature is below 55 ℃, and discharging; vacuumizing in the whole vulcanization process, wherein the vacuum degree is required to be more than 0.08 MPa;
and step 2 c: detaching the metal baffle plate, separating the upper female die (2) containing the rigid prosthesis, separating the air bag core die (3) with the joint from the inner surface of the rigid prosthesis of the lower female die (1), and trimming the silicone rubber edge to obtain the air bag core die (3);
step 2 d: respectively separating the rigid prosthesis from the lower female die (1) and the upper female die (2); when the air bag core mold (3) does not meet the use requirement, the rigid prosthesis and the integral air bag forming mold can be used for repeated manufacture;
and step 3: laying and pasting prepreg on the lower female die (1) layer by layer, wherein the laying and pasting step is as follows: 1 layer of 0/90-degree carbon fiber fabric prepreg is laid on the inner surface of the lower female die (1); sequentially paving 1 layer of 0 degree/90 degree and 1 layer of +/-45 degree carbon fiber fabric prepreg on the left side of the lower female die (1), respectively placing redundant prepreg on a non-working molded surface (4) on the left side of the lower female die (1), and separating the prepreg by using an isolating film; sequentially paving 2 layers of 0 degree/90 degree and 2 layers of +/-45 degree carbon tape prepregs on the inner surface of the lower female die (1); 1 layer of +/-45-degree carbon fiber fabric prepreg is laid and attached to the left side of the lower female die (1); sequentially paving 1 layer of 0 degree/90 degree and 2 layers of +/-45 degree carbon fiber fabric prepreg on the right side of the lower female die (1), respectively placing redundant prepreg on a working profile (4) on the left side of the lower female die (1), and separating the prepreg by using an isolating film;
the prepreg is stored in a low-temperature refrigeration environment at the temperature of-18 ℃, and no condensed water is formed on the packaging bag before unsealing; the paving is carried out in a purification room, the temperature in the purification room is kept at 22 +/-4 ℃, and the relative humidity is not more than 65%;
and 4, step 4: metal baffles are arranged at two ends of the lower female die (1), the air bag core die (3) is placed in the metal baffles, and the inflation joints and the deflation joints are fixed on the corresponding baffles; filling nitrogen into the air bag core mold (3) to 0.4 MPa;
and 5: removing an isolating film from 1 layer of redundant prepreg reserved on the working profile (4) on the left side of the lower female die (1) and 3 layers of redundant prepreg reserved on the working profile (4) on the right side, and then respectively turning and pressing the prepregs layer by layer on two sides of the upper surface of the air bag core die (3); continuously and sequentially paving 2 layers of plus or minus 45-degree and 2 layers of 0-degree/90-degree carbon tape prepregs on the upper surface of the air bag core mold (3); removing the isolating film from 2 layers of redundant prepreg reserved on the non-working molded surface (4) on the left side, and then respectively turning and pressing the prepreg on the upper surface of the air bag core mold (3) layer by layer; 1 layer of 0/90-degree carbon fiber fabric prepreg is paved and adhered on the inner surface of the upper female die (2); finally, combining an upper female die (2) and a lower female die (1) which respectively contain prepreg, and installing metal baffles at two ends to form a closed assembly;
step 6: sequentially placing a non-porous isolating film and an embossed high-ductility vacuum bag on the outer edge of the closed assembly, and forming a vacuum closed system through adhesion of a sealing adhesive tape; placing the vacuum closed system in a vacuum curing furnace for curing: firstly, heating at a heating rate of 1-3 ℃/min until the constant temperature of 120 ℃ is reached, and keeping the temperature for 1 hour; cooling at the cooling rate of 3 ℃/min until the temperature is below 55 ℃, and discharging; vacuumizing in the whole curing process, wherein the vacuum degree is required to be more than 0.08 MPa;
and 7: cleaning a non-porous isolating film and an embossing type high-ductility vacuum bag, disassembling baffles at two ends of the assembly, and upwards and integrally separating the lower female die (2); after the air bag core mold (3) is subjected to nitrogen gas discharge treatment, the air bag core mold (3) is drawn out from the solidified product blank; and separating the product blank from the upper female die (1), performing appearance processing on the remaining edge of the product, and performing polishing treatment on the sanding notch to obtain the non-equal-diameter closed square tubular carbon fiber beam structural part of the unmanned aerial vehicle.
The integral air bag forming die is a frame type metal steel die.
Advantageous effects
The invention provides a method for manufacturing a non-equal-diameter closed square tubular carbon fiber beam structural part of an unmanned aerial vehicle, which has the following beneficial effects:
(1) the non-equal-diameter closed square tubular carbon fiber beam structural part effectively solves the problem of optimization of the structural layout of the wings of the airplane body, improves the utilization rate of the internal space of the airplane body, reduces the occupation of the internal space of the airplane body and optimizes the structure of the airplane body.
(2) The problem of limited application of the existing integrally formed carbon fiber beam structural part is solved, the operability and the demolding performance in the product forming process are improved, and the application range of the integral forming process is effectively improved.
3) The demoulding problem after integral forming is effectively improved, integral forming of a complex beam structure is realized, the reliability of a product is improved, and the service life of a core mould is prolonged;
(4) the integral forming tool is effectively simplified, the forming process is simplified, and the product performance and the size stability of the integral forming are ensured.
Drawings
Figure 1 is a schematic view of a carbon fiber beam structural member of the present invention;
FIG. 2 is a schematic representation of a carbon fiber fabric ply;
FIG. 3 is a schematic view of a tool assembly prior to curing;
wherein, 1-lower female die, 2-upper female die and 3-air bag core die; 4-non-forming working surface;
FIG. 4 is a simplified view of a mold;
FIG. 5 is a simplified drawing of a rigid prosthesis (2 prostheses are molded separately, but not demolded);
FIG. 6 is a simplified diagram of balloon core membrane fabrication (silicone rubber alone laid over 2 prostheses);
FIG. 7 is a mold closing view.
Detailed Description
The invention will now be further described with reference to the following examples and drawings:
the technical scheme of the invention is a manufacturing process of a non-equal-diameter closed square tubular carbon fiber beam structural part of a small and medium-sized unmanned aerial vehicle, which comprises the following steps:
step 1, tool design: and according to the three-dimensional digital model of the product, tool design is carried out by CATIA software, and tool and die processing is carried out according to the digital model to obtain the integral air bag forming die. The whole air bag forming die is divided into a lower female die 1 and an upper female die 2, the lower female die 1 and the upper female die 2 are connected through a positioning pin and a bolt, a cavity is formed in the middle of the lower female die and the upper female die after combination, and the cavity is consistent with the shape of a non-equal-diameter closed square tubular carbon fiber beam structural workpiece of the unmanned aerial vehicle to be processed. The tool is designed in a partitioning mode so as to ensure that the air bag is smoothly demoulded after vulcanization; the two ends of the combined die are respectively provided with a baffle, and the baffle at one end is provided with an inflation joint port and an deflation joint port which are used for fixing the inflation joint and the deflation joint of the air bag core die 3, and the joints adopt a quick-release connection mode.
Step 2, manufacturing an airbag core mold 3:
and opening the forming die, and sequentially coating a hole sealing agent and a water-soluble release agent on the forming working surface of the forming die.
Sequentially paving single-layer sheet glass cloth prepreg with the thickness of 0.1mm on the working surfaces of the lower female die 1 and the upper female die 2 respectively until a preformed body with the same thickness as the product is formed; after trimming and curing of the residual edges, 1 layer of tooling demolding cloth is respectively paved on the inner surface of the rigid prosthesis to form the outer profile required by the forming of the air bag core mold 3.
The silicone rubber layer is laid and attached on the respective inner molded surface of the rigid prosthesis; closing a lower female die 1 and an upper female die 2 containing a silicone rubber layer and a rigid prosthesis, and installing upper baffles at two sides to form a closed assembly; nitrogen is filled through the air filling and discharging joint until the pressure of 0.4MPa is formed inside the cavity of the combination body; and (3) carrying out air tightness detection on the interior of the cavity, and when the leakage pressure within 5 minutes is not more than 0.017MPa, putting the combined body into a vacuum curing furnace for vulcanization, wherein the main vulcanization parameter is constant temperature of 180 ℃ for 2 hours. The temperature control precision of the vacuum curing furnace is required to be +/-3 ℃, the temperature uniformity is +/-5 ℃, and the vacuum degree during curing is required to be not less than 0.08 MPa.
Disassembling baffles at two ends and an upper female die 2 containing a rigid prosthesis, and taking out an air bag core die 3; the excess edge generated by the molding is trimmed by a paper cutter blade to obtain a molding air bag core mold 3.
And respectively carrying out demoulding treatment on the rigid prostheses on the lower female die 1 and the upper female die 2 to obtain 2 corresponding rigid prostheses. The balloon core mold 3 can be reused generally 6 to 12 times, and if the balloon core mold 3 is damaged and cannot be used as a forming core mold, the rigid prosthesis and the integral balloon forming mold can be repeatedly manufactured.
And 4, preforming:
and (3) paving and pasting prepreg on the lower female die 1 layer by layer, respectively separating redundant prepreg (reservation) by using an isolating film, and placing the prepreg on the non-working molded surfaces at two sides of the die.
Baffles are arranged at two ends of the lower female die 1, the air bag core die 3 is arranged in the baffles, and the inflation joints and the deflation joints are fixed on the corresponding baffles; the balloon core mold 3 was charged with nitrogen gas to 0.4 MPa. And respectively paving and sticking the residual prepreg reserved on the non-working surface of the lower female die 1 on the two sides of the air bag core die 3 in sequence.
And laying and pasting prepreg on the upper female die 2.
The upper and lower female moulds 2, 1, each containing prepreg, are combined to form a closed assembly.
Paving and pasting the porous insulation film on a clean room, keeping the temperature in the clean room to be 22 +/-4 ℃, keeping the relative humidity not more than 65%, and carrying out necessary vacuum pre-compaction in the whole process, wherein the vacuum pre-compaction method is that a porous insulation film, an air-permeable felt and a vacuum bag are sequentially paved and pasted on a preformed body, a vacuum closed system is formed through adhesion of a sealing adhesive tape, and then the vacuum degree in the system is kept for at least 10 minutes in a continuous vacuumizing mode at the pressure of more than 0.08 MPa.
Step 5, process combination and curing: sequentially placing a non-porous isolating film and an embossed high-ductility vacuum bag on the outer edge of the closed assembly, and forming a vacuum closed system through adhesion of a sealing adhesive tape; and then according to the curing parameter requirements of the specification of the prepreg material, carrying out vacuum-pumping curing in a vacuum curing furnace, wherein the main curing parameter is constant temperature of 120 ℃ for 1 hour.
Step 6, demolding: cleaning the imperforate isolating film and the embossing type high-ductility vacuum bag, disassembling the baffles at the two ends of the assembly, and separating the lower female die 2 upwards and integrally; after the air-pocket core mold 3 is deflated, the air-pocket core mold 3 is drawn out from the solidified product blank; the product blank is then released from the upper female die 1.
Step 7, processing the appearance: and (5) carrying out appearance processing on the product residual edge along the contour line of the outer edge, sanding the notch, and carrying out finishing treatment.
The specific embodiment is as follows:
firstly, designing a tool.
Referring to fig. 1, the product of this embodiment is a typical irregular part with a non-equal-diameter closed square-tube-shaped carbon fiber beam structure, and has small two ends and a large middle part, and symmetric inward concave grooves are distributed at the two ends, so that the product can be inserted and fixed with other carbon fiber composite connecting pieces, and load transfer is facilitated.
And according to the three-dimensional digital model of the product, using CATIA software to carry out tool design, and carrying out die machining according to the digital model to obtain the integral air bag forming die.
Referring to fig. 3, the integral air bag forming die mainly comprises a lower female die 1 and an upper female die 2, wherein the lower female die 1 is a main forming die, and the block design of the tooling die is carried out along a process parting surface; the upper female die 2 is matched with the lower female die 1 for use, and an integral combined die is formed in a positioning pin and bolt connection mode and used for providing a required upper molded surface for a product during integral forming and curing of the air bag core die 3.
On the basis, the two ends of the combined integral air bag forming die are provided with the baffles, so that the cavity is convenient to seal. The baffle is a metal flat plate made of the same material as the die, the surface of the baffle contains bolt holes, and the baffle is respectively matched and connected with the end faces of two sides of the lower female die 1 and the upper female die 2 through bolts. One of the metal flat plate has a central hole in the middle region, and can be used for fixing the inflation and deflation joints of the air bag core mold 3, and the joints adopt a quick-release connection mode.
The design of whole gasbag forming die piecemeal is simple, reasonable, can effectively avoid because of the poor scheduling problem of gas tightness that too much piecemeal design causes, through the detachable baffle that both ends set up, guarantee good seal in the die cavity promptly and the detachability of baffle, be favorable to the location and the drawing of patterns of gasbag mandrel again. The integral quality state of the product before and after curing can be fully and effectively solved by the matching use of the integral air bag forming die and the air bag core die 3, and the product demoulding performance and the reliability of the inner and outer quality are improved.
In the second step, the balloon core mold 3 is manufactured.
And (3) unsealing the lower female die 1 and the upper female die 2, sequentially coating a hole sealing agent and a water-soluble release agent on each forming working surface, and airing for 15 min.
With reference to fig. 2, the manufacture of a rigid prosthesis of the same thickness as the product is carried out (the inner surface of the rigid prosthesis being used to provide the outer surface required for the formation of the balloon core 3): respectively paving and sticking prepreg on the working surfaces of the lower female die 1 and the upper female die 2 layer by layer until preformed bodies with the same thickness as the product are respectively formed; the preform was trimmed to shape using a paper cutter. In this example, a sheet glass cloth fabric prepreg having a single layer thickness of δ 0.1mm was used, and it was required to perform necessary vacuum pre-compaction in the laying process, and the method was as described above. The lower and upper female molds 1 and 2, respectively, containing the preform are then process assembled and cured. The process combination content is that a non-porous isolating film, a breathable felt and a vacuum bag are sequentially paved on a preformed body, and a vacuum closed system is formed through adhesion of sealing tapes. The curing process is carried out in a vacuum curing furnace, and the main content is that the temperature is raised at the rate of 1-3 ℃/min until the constant temperature reaches 120 ℃, and the temperature is preserved for 1 hour; cooling at the cooling rate of 3 ℃/min until the temperature is below 55 ℃, and discharging; the whole curing process is vacuumized in the whole process, and the vacuum degree is required to be more than 0.08 MPa.
And (3) paving and pasting 1 layer of tooling demolding cloth on the inner profile surface of each rigid prosthesis of the lower female die 1 and the upper female die 2, and paving and pasting silicon rubber sheets on the tooling demolding cloth respectively to form the silicon rubber layers. The specific method is that thicker silicone rubber layers are paved on each corner of the rigid prosthesis and the baffle, so that certain rigidity can be effectively formed, and an effective supporting molded surface is formed; the connector is embedded into the silicon rubber layer on the baffle at one end, so that the tightness of the vulcanized connector and the silicon rubber is ensured. And after finishing paving and pasting, carrying out appearance finishing on the silicone rubber layer, and reserving a 5mm allowance at a future lap joint.
On the basis, a lower female die 1 and an upper female die 2 which contain a silicone rubber layer and a rigid prosthesis are closed, and baffles are respectively arranged at two ends of the combined die to finally form a closed assembly.
Filling nitrogen into the cavity of the sealed combination body through the air filling and discharging joint until the pressure of 0.4MPa is formed in the cavity; carrying out air tightness detection on the interior of the cavity, and when the leakage pressure is not more than 0.017MPa within 5 minutes, putting the combination into a vacuum curing furnace for vulcanization, wherein the main content is that the temperature is increased at the rate of 1-3 ℃/min until the constant temperature reaches 180 ℃, and the temperature is maintained for 2 hours; cooling at a cooling rate of 3 ℃/min, discharging the product until the temperature is below 55 ℃, and demolding. And finally, trimming the flaky residual edge generated by air bag forming by using a paper cutting blade to obtain the air bag core mold 3.
And thirdly, preparing the process.
Preparing a prepreg for integral molding; the prepreg adopted in the embodiment is MTM28/CF 0300-42% RW carbon cloth fabric prepreg and MTM28-1/T700 SC-125-33% RW carbon belt prepreg with the single-layer thickness delta 0.2 mm.
And fourthly, cutting the prepreg.
The product three-dimensional digital-analog method is used for unfolding and lofting the prepreg, and the AutoCAD is used for optimizing the layout design of the prepreg, so that the material utilization rate is improved, and the cost is reduced; and cutting by using a numerical control blanking machine, and marking and stacking the cut prepreg. The prepreg is unfolded, lofted and discharged according to the cutting size by using AutoCAD software, then cut by using a numerical control blanking machine, marked and stacked, and the direction deviation of the cut pieces is allowed to be +/-1 degrees and the size deviation is allowed to be +/-1 mm during cutting.
And fifthly, laying the prepreg.
Referring to fig. 2, the prepreg is laid on the lower female die 1 layer by layer, and the laying step is as follows: 1 layer of 0/90-degree carbon fiber fabric prepreg is laid on the bottom surface (web plate) of the lower female die 1; sequentially paving 1 layer of 0 degree/90 degree and 1 layer of +/-45 degree carbon fiber fabric prepreg on the left side (left edge strip) of the lower female die 1, respectively separating redundant prepreg (reservation) and placing the prepreg on the non-working molded surface on the left side of the lower female die 1; sequentially paving 2 layers of 0 degree/90 degree and 2 layers of +/-45 degree carbon tape prepregs on the bottom surface (web plate) of the lower female die 1; paving 1 layer of +/-45-degree carbon fiber fabric prepreg on the left side (left edge strip) of the lower female die 1; and sequentially paving 1 layer of 0 degree/90 degree and 2 layers of +/-45 degree carbon fiber fabric prepreg on the right side (right edge strip) of the lower female die 1, respectively separating redundant prepreg (reservation) and placing the prepreg on the non-working molded surface on the left side of the lower female die 1.
Baffles are arranged at two ends of the lower female die 1, the air bag core die 3 is arranged in the baffles, and the inflation joints and the deflation joints are fixed on the corresponding baffles; the balloon core mold 3 was charged with nitrogen gas to 0.4 MPa.
After the isolating film is removed, the redundant prepreg reserved on the 1 layer of the left edge strip and the 3 layers of the right edge strip is respectively turned and pressed on the two sides of the upper surface of the air bag core mold 3 layer by layer; continuously and sequentially paving 2 layers of plus or minus 45 degrees and 2 layers of 0 degree/90 degree carbon tape prepreg on the upper surface of the air bag core mold 3; and (3) turning and pressing the redundant prepreg reserved in the 2 layers at the left edge strip on the upper surface of the air bag core mold 3 layer by layer respectively after the isolating film is removed.
And (3) paving 1 layer of 0/90-degree carbon fiber fabric prepreg on the upper female die 2.
And finally, combining the upper female die 2 and the lower female die 1 which respectively contain the prepreg to form a closed combination body.
The requirements of the whole paving process are as follows: after the layer 1 is paved, carrying out vacuum pre-compaction for 1 time, and after that, carrying out vacuum pre-compaction for 1-3 layers each time, wherein the vacuum pre-compaction is required to be as described above; when the carbon fiber fabric prepreg is laid and pasted, lap joint treatment is carried out, the lap joint width is about 25mm, the lap joint seams between adjacent layers are staggered by about 25mm, and every 5 layers can be repeatedly staggered and arranged. When the carbon tape prepreg is laid, the fibers are not allowed to break in the radial direction, the butt joint is allowed along the fiber direction, and the maximum gap of a single-layer butt joint seam is 1 mm.
And sixthly, combining the processes and curing.
Sequentially placing a non-porous isolating film and an embossed high-ductility vacuum bag on the outer edge of the closed assembly, and forming a vacuum closed system through adhesion of a sealing adhesive tape; then according to the curing parameter requirements of the specification of the prepreg material, vacuumizing and curing are carried out in a vacuum curing furnace, specifically, the temperature is raised at the rate of 1-3 ℃/min until the constant temperature of 120 ℃ is reached, and the temperature is maintained for 1 hour; cooling at the cooling rate of 3 ℃/min until the temperature is below 55 ℃, and discharging.
And seventhly, demolding and processing the shape.
Cleaning the imperforate isolating film and the embossing type high-ductility vacuum bag, disassembling the baffles at the two ends of the assembly, and separating the lower female die 2 upwards and integrally; after the gas bag core mold 3 is subjected to nitrogen gas discharge treatment, the gas bag core mold 3 is drawn out from the solidified product blank; the product blank is then released from the upper female die 1. And (5) carrying out appearance processing on the remaining edge of the product, sanding the notch, and finishing.
And finishing the integral forming of the non-equal-diameter closed square tubular carbon fiber beam structural part.
Referring to fig. 4, the tooling design: an upper and a lower assembling die; fig. 5 shows the rigid prosthesis fabrication: 2 prostheses are respectively formed without demoulding; FIG. 6 shows the application of silicone rubber to 2 prostheses individually; FIG. 7 shows involution; the principle of the invention is as follows: 1. when the silicon rubber is vulcanized (namely, the constant temperature is 180 ℃), the silicon rubber becomes viscous rubber fluid, and continuous and sealed rubber can be formed along with the continuation of temperature and time, so that after two light blue silicon rubber layers are combined, a whole can be gradually formed along with the continuation of temperature and time, and nitrogen gas filled in the silicon rubber can better form pressure equalization to ensure that the silicon rubber is smooth.
2. Steel is not sticky to steel.
3. The prostheses are individually shaped and are not tacky at temperature.
4. Combining the above 3 points, the integral core mold can be obtained after the block involution, and the involution can be disassembled.
5. By the time the product is formed, it is just a process of replacing the prosthesis with a product layup. So it can be said that mold + prosthesis → silicone rubber; mold + silicone rubber → "new prosthesis" (i.e., product).
The invention has the characteristics that: the combined female die and the air bag core die are used for forming products, so that the easy demoulding performance, the quality stability and the reliability of the products are ensured. The method of the invention can also be used for manufacturing the equal-diameter tubular laminated carbon fiber composite material product.
Claims (2)
1. A manufacturing method of a non-equal-diameter closed square tubular carbon fiber beam structural part of an unmanned aerial vehicle is characterized by comprising the following steps:
step 1: manufacturing of the integral air bag forming die:
adopting CATIA software to carry out three-dimensional modeling and optimized design of the integral air bag forming die, and carrying out die processing on the optimized digital model; the integral air bag forming die is divided into a lower female die (1) and an upper female die (2), the lower female die (1) and the upper female die (2) are connected through a positioning pin and a bolt, a cavity is formed in the middle after combination, and the shape of the cavity is consistent with that of a non-equal-diameter closed square tubular carbon fiber beam structural workpiece of the unmanned aerial vehicle to be processed; metal baffles are arranged at two ends of the integral air bag forming die and used for sealing the cavity; the baffles at two ends are respectively connected with the end faces of the lower female die (1) and the upper female die (2) in a positioning way through bolts, and the baffle at one end is provided with an inflation joint and a deflation joint;
step 2: production of balloon core mold (3):
step 2 a: sequentially smearing hole sealing agents and water-soluble release agents on the inner surfaces of the lower female die (1) and the upper female die (2) respectively, airing for 15min, paving single-layer sheet glass cloth fabric prepreg with the thickness of 0.1mm on the inner surfaces of the lower female die (1) and the upper female die (2) layer by layer until a preformed body with the thickness equal to that of a product is formed, and performing vacuum pre-compaction in the paving process to enable the prepreg to be tightly attached; paving aporate barrier film, air felt and vacuum bag on the preforming body in proper order, forming the airtight system of vacuum through the adhesion of sealing tape, will contain lower bed die (1) and last bed die (2) of preforming body and place in vacuum curing oven and solidify: firstly, heating at a heating rate of 1-3 ℃/min until the constant temperature of 120 ℃ is reached, and keeping the temperature for 1 hour; cooling at a cooling rate of 3 ℃/min until the temperature is below 55 ℃, and discharging to obtain an upper rigid prosthesis and a lower rigid prosthesis; vacuumizing in the whole curing process, wherein the vacuum degree is required to be more than 0.08 MPa;
and step 2 b: respectively paving and sticking 1 layer of tooling demolding cloth on the inner surfaces of the upper and lower rigid prostheses, and then respectively paving and sticking silicon rubber sheets on the tooling demolding cloth to form a silicon rubber layer; then closing the silicon-containing rubber layer, the lower female die (1) and the upper female die (2) of the rigid prosthesis, installing metal baffles at two ends, and embedding a joint into the silicon rubber layer on the baffle at one end to form a closed assembly containing a cavity; filling nitrogen into the cavity through the gas filling and discharging joint, and maintaining the pressure at 0.4 Mpa; and (3) detecting the air tightness of the interior of the cavity, and when the leakage pressure is not more than 0.017MPa within 5 minutes, putting the combined body into a vacuum curing furnace for vulcanization: firstly, heating at the heating rate of 1-3 ℃/min until the constant temperature of 180 ℃ is reached, and preserving heat for 2 hours; cooling at the cooling rate of 3 ℃/min until the temperature is below 55 ℃, and discharging; vacuumizing in the whole vulcanization process, wherein the vacuum degree is required to be more than 0.08 MPa;
and step 2 c: detaching the metal baffle plate, separating the upper female die (2) containing the rigid prosthesis, separating the air bag core die (3) with the joint from the inner surface of the rigid prosthesis of the lower female die (1), and trimming the residual edge of the silicone rubber layer to obtain the air bag core die (3);
step 2 d: respectively separating the rigid prosthesis from the lower female die (1) and the upper female die (2); when the air bag core mold (3) does not meet the use requirement, the rigid prosthesis and the integral air bag forming mold can be used for repeated manufacture;
and step 3: laying and pasting prepreg on the lower female die (1) layer by layer, wherein the laying and pasting step is as follows: 1 layer of 0/90-degree carbon fiber fabric prepreg is laid on the inner surface of the lower female die (1); sequentially paving 1 layer of 0 degree/90 degree and 1 layer of +/-45 degree carbon fiber fabric prepreg on the left side of the lower female die (1), respectively placing redundant prepreg on a non-working molded surface (4) on the left side of the lower female die (1), and separating the prepreg by using an isolating film; sequentially paving 2 layers of 0 degree/90 degree and 2 layers of +/-45 degree carbon tape prepregs on the inner surface of the lower female die (1); 1 layer of +/-45-degree carbon fiber fabric prepreg is laid and attached to the left side of the lower female die (1); sequentially paving 1 layer of 0 degree/90 degree and 2 layers of +/-45 degree carbon fiber fabric prepreg on the right side of the lower female die (1), respectively placing redundant prepreg on a non-working molded surface (4) on the left side of the lower female die (1), and separating the prepreg by using an isolating film;
the prepreg is stored in a low-temperature refrigeration environment at the temperature of-18 ℃, and no condensed water is formed on the packaging bag before unsealing; the paving is carried out in a purification room, the temperature in the purification room is kept at 22 +/-4 ℃, and the relative humidity is not more than 65%;
and 4, step 4: metal baffles are arranged at two ends of the lower female die (1), the air bag core die (3) is placed in the metal baffles, and the inflation joints and the deflation joints are fixed on the corresponding baffles; filling nitrogen into the air bag core mold (3) to 0.4 MPa;
and 5: removing an isolating film from 1 layer of redundant prepreg reserved on the non-working profile (4) on the left side of the lower female die (1) and 3 layers of redundant prepreg reserved on the non-working profile (4) on the right side, and turning and pressing the prepregs on two sides of the upper surface of the air bag core die (3) layer by layer respectively; continuously and sequentially paving 2 layers of plus or minus 45-degree and 2 layers of 0-degree/90-degree carbon tape prepregs on the upper surface of the air bag core mold (3); removing the isolating film from 2 layers of redundant prepreg reserved on the non-working molded surface (4) on the left side, and then respectively turning and pressing the prepreg on the upper surface of the air bag core mold (3) layer by layer; 1 layer of 0/90-degree carbon fiber fabric prepreg is paved and adhered on the inner surface of the upper female die (2); finally, combining an upper female die (2) and a lower female die (1) which respectively contain prepreg, and installing metal baffles at two ends to form a closed assembly;
step 6: sequentially placing a non-porous isolating film and an embossed high-ductility vacuum bag on the outer edge of the sealed combination body, and forming a vacuum sealed system through adhesion of a sealing adhesive tape; placing the vacuum closed system in a vacuum curing furnace for curing: firstly, heating at a heating rate of 1-3 ℃/min until the constant temperature of 120 ℃ is reached, and keeping the temperature for 1 hour; cooling at the cooling rate of 3 ℃/min until the temperature is below 55 ℃, and discharging; vacuumizing in the whole curing process, wherein the vacuum degree is required to be more than 0.08 MPa;
and 7: cleaning a non-porous isolating film and an embossing type high-ductility vacuum bag, disassembling baffles at two ends of the assembly, and upwards and integrally separating the upper female die (2); after the air bag core mold (3) is subjected to nitrogen gas discharge treatment, the air bag core mold (3) is drawn out from the solidified product blank; and separating the product blank from the lower female die (1), performing appearance processing on the remaining edge of the product, and performing polishing treatment on the sanding notch to obtain the non-equal-diameter closed square tubular carbon fiber beam structural part of the unmanned aerial vehicle.
2. The manufacturing method of the non-constant diameter closed square tubular carbon fiber beam structural component of the unmanned aerial vehicle as claimed in claim 1, wherein the integral air bag forming mold is a frame type metal steel mold.
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