A lightweight composite fuel tank for missiles and a manufacturing method thereof

Abstract

The present invention relates to a lightweight missile-carrying composite fuel tank and a manufacturing method thereof. The composite fuel tank is divided into two parts, namely, an upper cover of the composite fuel tank and a lower cover of the composite fuel tank. The upper cover and the lower cover of the composite fuel tank are respectively formed by an expansion film molding method, and then the upper cover and the lower cover are sealed and bonded with a room temperature curing adhesive to manufacture the composite fuel tank. Among them, in order to meet the requirements of structural strength and rigidity, the anti-sway plate and the rib plate inside the composite fuel tank need to be integrally cured and formed with the upper cover and the lower cover of the fuel tank, and reinforcing ribs are laid at the bottom of the anti-sway plate and the rib plate to improve the compressive resistance of the composite fuel tank. The present invention overcomes the shortcomings brought about by the application of metal fuel tanks in the field of cruise missiles, fills the gap in the application of composite fuel tanks in large-scale missile body compartments in the field of cruise missiles, and provides a method for manufacturing a lightweight composite fuel tank used in the field of cruise missiles.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material forming technology for missile-borne oil storage devices, and in particular relates to a lightweight missile-borne composite material oil tank and a manufacturing method thereof. Background Art

[0002] As a key component of a cruise missile, the weight of the fuel tank has a decisive influence on the total weight of the cruise missile.

[0003] Usually, the fuel tanks used to load cruise missiles are metal tanks, which have the following main disadvantages: 1) large mass; 2) poor corrosion resistance; 3) easy to generate static electricity and low safety; 4) complex molding process; 5) high processing and manufacturing costs.

[0004] Therefore, in order to meet the demand for lightweight weapons and equipment and solve the shortcomings of the above-mentioned metal fuel tanks in the field of cruise missiles, the call for the application of composite fuel tanks in the field of cruise missiles is getting higher and higher. Composite fuel tanks have the advantages of light weight, strong corrosion resistance, high safety, simple manufacturing, and low production cost, which can make up for the shortcomings of metal fuel tanks. It was found that the application of composite fuel tanks in the large fuselage compartment of cruise missiles is still blank. Summary of the invention

[0005] In view of this, the purpose of the present invention is to overcome the shortcomings brought about by the application of metal fuel tanks in the field of cruise missiles, fill the gap in the application of composite fuel tanks in large missile body compartments in the field of cruise missiles, and provide a manufacturing method for lightweight composite fuel tanks used in the field of cruise missiles.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the present invention is: the missile-borne fuel tank shell adopts a composite thin-wall foam sandwich structure. At the same time, the internal structure of the cruise missile fuel tank is complex. In order to meet its use requirements, the fuel tank is divided into two parts, namely the upper cover and the lower cover. The upper cover and the lower cover of the composite fuel tank are respectively formed by the expansion film molding method, and then the upper cover and the lower cover are sealed and bonded with room temperature curing glue to manufacture the composite fuel tank. Among them, in order to meet the requirements of structural strength and rigidity, the anti-sway plate and rib plate inside the composite fuel tank need to be integrally cured and formed with the upper and lower covers of the fuel tank, and reinforcing ribs need to be laid at the bottom of the anti-sway plate and the rib plate to improve the compressive resistance of the composite fuel tank. By using this molding method, a composite fuel tank with a length greater than 2m and a complex internal structure and strong pressure bearing capacity can be manufactured.

[0007] The present invention is achieved through the following technical solutions:

[0008] A lightweight missile-carrying composite fuel tank comprises a composite fuel tank upper cover and a composite fuel tank lower cover; the composite fuel tank upper cover and the composite fuel tank lower cover are thin-wall foam sandwich structures, comprising an outer skin, foam, and an inner skin; the composite fuel tank upper cover and the composite fuel tank lower cover are sealed by adhesive.

[0009] Furthermore, an anti-sway plate is arranged inside the composite fuel tank upper cover, and the anti-sway plate and the composite fuel tank upper cover are integrally solidified; an anti-sway plate and a rib plate are arranged inside the composite fuel tank lower cover, and the anti-sway plate and the rib plate are integrally solidified with the composite fuel tank lower cover; reinforcing ribs are laid at the bottom of the anti-sway plate and the rib plate to improve the compressive resistance of the composite fuel tank.

[0010] Furthermore, the molding material system of the composite material fuel tank includes fiber-reinforced resin (ie, the material of the outer skin and the inner skin), foam and adhesive film.

[0011] Preferably, the fiber is carbon fiber, and the type of fiber is selected according to the product structure characteristics and design load, such as one or more of T700, T800, T1000, etc. The reinforcing fabric can be in the form of plain fabric, satin fabric, twill fabric, weft knitted fabric and warp knitted fabric. It is preferred to have good paving performance, can meet the paving requirements of complex curved surface components, and after mixing with epoxy resin, it is beneficial to the wettability of epoxy resin, thereby further improving the molding quality.

[0012] Preferably, according to the curing requirements, the resin is a medium-temperature epoxy resin system. The specific type of resin is not particularly limited and is selected according to design requirements, such as one or more of 9368, 8522, 6808, 9A16, EM817B, EM134, etc.

[0013] Preferably, the foam is a polymethacrylimide (PMI) foam core board, preferably having good bending and paving properties. There is no special restriction on the specific type of foam, which can be selected according to design requirements, such as one or more of XK110-HT, CK110-HT, A-110, C-110 and AF-110.

[0014] Preferably, according to the curing requirements, the adhesive film is a medium-temperature adhesive film. The specific type of the adhesive film is not particularly limited and is selected according to the design requirements, such as one or more of J-47A, J-78B, J-69D and AD-36.

[0015] Furthermore, the composite fuel tank has a molding structure of outer skin + foam + inner skin, wherein the outer skin is 1.8-2.2 mm thick, the foam is 5.8-6.2 mm thick, and the inner skin is 1.8-2.2 mm thick, wherein a layer of adhesive film needs to be laid between the composite material and the foam and between the foams; the anti-sway plate and the rib plate in the fuel tank are also foam sandwich structures (composite material + foam + composite material), wherein the total thickness of the composite material of the anti-sway plate is 1.5-2 mm, the foam is 2.8-3.2 mm thick, the total thickness of the composite material of the rib plate is 5.8-6.2 mm, and the foam is 3.8-4.2 mm thick. The inner and outer skins of the upper and lower covers of the fuel tank are paved in a quasi-isotropic manner.

[0016] A method for manufacturing a lightweight composite fuel tank for missiles is achieved by the following steps:

[0017] Step 1: Forming the composite material fuel tank cover;

[0018] Step 2: forming a composite fuel tank lower cover;

[0019] Step 3: Install the oil pipe in the composite fuel tank lower cover;

[0020] Step 4: Bond the composite fuel tank upper cover and the composite fuel tank lower cover.

[0021] Further, step one: forming a composite material fuel tank upper cover, comprising:

[0022] (1) Design the mold using 3D modeling software based on the shape and internal structure of the fuel tank. The mold inner shape must be consistent with the outer shape of the fuel tank cover. The mold core block is designed to ensure the complex structure inside the fuel tank shell is formed.

[0023] (2) A forming mold is manufactured according to the established three-dimensional structural model, wherein the forming mold includes an upper / lower mold cover plate, front and rear side strips, left and right side strips, a forming core block, a preformed insert, and a pressurized fastening screw; the lower mold cover plate and the front and rear side strips and the left and right side strips form an outer mold with an upper end opening, and after all the layers are laid, the mold is closed by the upper cover plate; the forming core block and the preformed insert are used to form the complex internal structure of the fuel tank, including the integral forming of the anti-sway plate and the reservation of the position of the equipment cover and the left and right cover, and a fuel tank shell that meets the internal quality and structural strength is obtained by placing a rubber film between the forming core blocks for pressurized and heated expansion;

[0024] (3) Laying out the outer skin, reinforcing ribs, foam, and inner skin in sequence in the outer mold with an upper opening, and performing vacuum pre-compaction once after the outer skin and foam are laid out;

[0025] (4) After the inner skin is laid, the forming core blocks, anti-sway plates and rubber strips are laid in the mold in order;

[0026] (5) After laying, buckle the upper cover plate onto the mold and check the mold gap. If the mold gap is too large, check whether the upper cover plate is completely fastened to the mold and whether there is any jamming. If there is no jamming, tighten the pressure screws until the mold gap is met and the mold is closed.

[0027] (6) Oven curing and molding, pushing the mold after mold closing into the oven for curing;

[0028] (7) Demolding and trimming: After curing, open the upper cover plate to remove the core block in the mold, take out the product and trim the flash to obtain the composite material tank upper cover.

[0029] Further, step 2: forming a composite material fuel tank lower cover, comprising:

[0030] (1) Design the mold using 3D modeling software based on the shape and internal structure of the fuel tank. The mold inner shape must be consistent with the outer shape of the fuel tank lower cover. The mold core block is designed to ensure the complex structure inside the fuel tank shell is formed.

[0031] (2) A forming mold is manufactured according to the established three-dimensional structural model, wherein the forming mold includes an upper / lower mold cover plate, front and rear side strips, left and right side strips, a forming core block, a preformed insert, and a pressurized fastening screw; the lower mold cover plate and the front and rear side strips and the left and right side strips form an outer mold with an upper end opening, and after all the layers are laid, the mold is closed by the upper cover plate; the forming core block and the preformed insert are used to form the complex internal structure of the fuel tank, including the integral forming of the anti-sway plate and the rib plate, and the reservation of the position of the wire hole and the steel bushing. A fuel tank shell that meets the internal quality and structural strength is obtained by placing a rubber film between the forming core blocks for pressurized and heated expansion;

[0032] (3) Laying out the outer skin, reinforcing ribs, foam, and inner skin in sequence in the outer mold with an upper opening, and performing vacuum pre-compaction once after the outer skin and foam are laid out;

[0033] (4) After the inner skin is laid, the forming core block, anti-sway plate, rib plate and rubber strip are laid in the mold in sequence;

[0034] (5) After laying, buckle the upper cover plate onto the mold and check the mold gap. If the mold gap is too large, check whether the upper cover plate is completely fastened to the mold and whether there is any jamming. If there is no jamming, tighten the pressure screws until the mold gap is met and the mold is closed.

[0035] (6) Oven curing and molding, pushing the mold after mold closing into the oven for curing;

[0036] (7) Demolding and trimming: After curing, open the upper cover plate to remove the core block in the mold, take out the product and trim the flash to obtain the composite material tank lower cover.

[0037] Furthermore, step three: installing the oil pipe includes:

[0038] After obtaining the composite material fuel tank lower cover, use a hole opener to open holes in the internal anti-sway plate of the fuel tank lower cover and the front and rear of the lower cover, then install the oil pipe, seal the opening at the same time, tighten the inner and outer nuts that fix the oil pipe to complete the installation of the oil pipe.

[0039] Further, step 4: bonding the composite material fuel tank upper / lower cover, including:

[0040] (1) Apply adhesive evenly to the overlap area between the upper and lower covers of the composite fuel tank;

[0041] (2) Snap the upper cover onto the lower cover smoothly, making sure that the overlapping areas are completely butted together and that adhesive can be squeezed out of the overlapping seams;

[0042] (3) Use straps or place heavy objects on the top of the oil tank for pressurized curing;

[0043] (4) Pressure relief and finishing: After curing, the bonding area should be polished and trimmed to ensure that the surface is flat and free of burrs.

[0044] The precision of the mold in step 1 and step 2 is 0-0.6 mm, the outer mold material is P20 steel, and the internal core block is 6061 aluminum alloy.

[0045] In the steps 1 and 2, before laying the outer skin in the outer mold, a layer of reinforcing fabric needs to be laid.

[0046] The outer skin of step one and step two is laid using unidirectional prepreg, and the laying method adopts quasi-isotropic laying.

[0047] The foam laying in step 1 and step 2 adopts a single layer of foam, and a layer of adhesive film is laid between the foam and the prepreg.

[0048] In the steps 1 and 2, the reinforcing ribs are laid at the bottom of the anti-sway plate to replace the original foam. The reinforcing ribs have a width of 9.8-10.2 mm and a thickness of 5.8-6.2 mm.

[0049] The inner skin in step 1 and step 2 is laid using unidirectional prepreg, and the laying method adopts quasi-isotropic laying.

[0050] After the inner skin is laid in step 1 and step 2, a layer of reinforcing fabric needs to be laid.

[0051] After the inner skin of step 1 and step 2 is laid, the excess skin needs to be cut off along the mold score line with a paper cutter.

[0052] The anti-sway plates and stiffener plates in step one and step two need to be prefabricated, and then laid together with the core blocks and connected to the inner skin. The prepreg material covering the anti-sway plates and stiffener plates is laid in a quasi-isotropic manner.

[0053] The unidirectional prepreg plies in step 1 and step 2 are not overlapped, but only butted along the fiber direction, that is, the butt joint gap is parallel to the fiber direction, and the butt joint gap width is ≤2mm. The fabric prepreg plies are overlapped, and the overlap width is between 15mm and 25mm. The splicing positions of adjacent plies are not allowed to appear at the same place, and must be staggered by more than 20mm. If splicing at the same position, at least 4 plies should be separated.

[0054] The ply in step 1 and step 2 should maintain smooth thickness changes, and no bridging is allowed in the thickness change area formed by the increase or decrease of the ply and where the ply crosses the fillet or step.

[0055] When laying the foam in step 1 and step 2, as much foam as possible should be laid at the rounded corners, and the gaps where the foam cannot be laid should be filled with prepreg.

[0056] The vacuum pre-compaction parameter requirements of step 1 and step 2 are vacuum degree ≥ 0.09 MPa, temperature 50±5° C., and time ≥ 30 min.

[0057] When removing the core blocks in step 1 and step 2, they do not necessarily need to be removed in a strict order.

[0058] In step 3, the oil pipes must be installed at the highest and lowest points of the oil tank respectively.

[0059] The adhesive in step 4 is a room temperature curing adhesive.

[0060] The beneficial effects of the present invention compared with the prior art are as follows:

[0061] (1) The present invention proposes a method for manufacturing a lightweight composite fuel tank for missiles, which overcomes the shortcomings of metal fuel tanks, such as large mass, poor corrosion resistance, low safety, and high molding difficulty, and fills the gap in the use of composite fuel tanks in the field of cruise missiles.

[0062] (2) The present invention innovatively uses a thin-wall composite foam sandwich structure to manufacture a composite fuel tank, which not only further reduces the weight of the fuel tank, but also greatly reduces the production cost, thus meeting the design requirements and having good economic benefits.

[0063] (3) Missile-borne fuel tanks are often complex in structure and difficult to replace with composite fuel tanks. The present invention provides a new idea for molding complex structural parts and solves the problem that the internal structure of the composite fuel tank shell is complex and difficult to mold. Compared with other curing processes, the curing process of the present invention is simple and easy to operate, which provides an effective reference for the subsequent development of similar composite fuel tanks. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a flow chart of a method for manufacturing a lightweight missile-carrying composite fuel tank provided by an embodiment of the present invention.

[0065] Figure 2 It is an axonometric view of the composite material fuel tank upper cover shell in the method of the present invention.

[0066] Figure 3 It is an axonometric view of a composite material fuel tank upper cover shell forming die in the method of the present invention.

[0067] Figure 4 It is an axonometric view of the composite material fuel tank lower cover shell body in the method of the present invention.

[0068] Figure 5 It is an axonometric view of a composite material fuel tank lower cover shell forming die in the method of the present invention.

[0069] Figure 6 It is a schematic diagram of installing the oil pipe on the lower cover of the composite material oil tank in the method of the present invention.

[0070] Figure 7 It is an appearance diagram of the composite material fuel tank upper / lower cover after bonding in the method of the present invention.

[0071] Explanation of the reference numerals: 1—left cover, 2—right cover, 3—equipment cover, 4, 15—anti-sway plate, 5, 19—overlap area, 6, 20—lower cover, 7, 21—upper cover, 8, 22—front edge strip, 9, 23—rear edge strip, 10, 24—left edge strip, 11, 25—right edge strip, 12, 26—molded core block, 13, 27—preformed insert, 14, 28—pressure screw, 16—rib plate, 17—steel bushing, 18—wire hole, 29—oil pipe (low point), 30—oil pipe (high point). DETAILED DESCRIPTION

[0072] In order to make the technical solution of the present invention more obvious and easy to understand, embodiments are given and described in detail as follows in conjunction with the accompanying drawings.

[0073] Example 1

[0074] like Figure 1 As shown, this embodiment provides a method for manufacturing a lightweight composite fuel tank for missiles, and the manufacturing method mainly includes the following steps:

[0075] (1) A molded composite fuel tank cover, wherein the cover includes an integrally molded anti-sway plate and a reserved position for the cover;

[0076] (2) Molding a composite material fuel tank lower cover, wherein the lower cover includes integral molding of a rib plate and an anti-sway plate, and reserved positions for wire holes, steel bushings, etc.;

[0077] (3) An oil pipe is installed in the lower cover of the composite fuel tank, and the material of the oil pipe is 5A06 aluminum;

[0078] (4) The composite fuel tank upper / lower cover is bonded using a room temperature curing adhesive, wherein the adhesive is J-133C.

[0079] Example 2

[0080] Figure 2 The composite material oil tank upper cover of the present invention comprises a left cover 1, a right cover 2, an equipment cover 3, an anti-sway plate 4 and an overlap area 5. Figure 3 The composite material oil tank upper cover shell forming mold of the present invention comprises a lower cover plate 6, an upper cover plate 7, a front side strip 8, a rear side strip 9, a left side strip 10, a right side strip 11, a forming core block 12, a preformed insert 13, and a pressure screw 14.

[0081] like Figure 2 , Figure 3 As shown, this embodiment provides a method for forming a composite material fuel tank upper cover, the steps are as follows:

[0082] (1) According to the product structure and appearance, taking into account the layup process and molding method, a solid model is established using 3D modeling software based on various conditions, and a molding mold is designed; according to the design idea, the composite material tank cover structure is a thin-walled foam sandwich structure (outer skin + foam + inner skin), and the layers are laid in the molding mold according to the female mold to ensure the product's external dimensions. At the same time, anti-sway plates, molding core blocks, pre-molded inserts, and rubber strips are placed in the female mold to ensure the complex internal structure of the tank;

[0083] (2) The molding materials are selected according to the product characteristics and load-bearing requirements. In this embodiment, T300-grade plain carbon cloth / 9A16 prepreg, T700-grade unidirectional carbon fiber / 9A16 prepreg, domestic PMI foam (CK110-HT) and J-47A medium-temperature adhesive film with good draping performance are selected; the outer skin thickness of the composite fuel tank upper cover shell of this embodiment is 1.8-2.2 mm, preferably 2 mm, the foam thickness is 5.8-6.2 mm, preferably 6 mm, and the inner skin thickness is 1.8-2.2 mm, preferably 2 mm; the total thickness of the anti-sway plate composite material is 1.5-2 mm, preferably 2 mm, and the foam thickness is 2.8-3.2 mm, preferably 3 mm;

[0084] (3) Use 3D digital modeling software to lay out the prepreg samples of the product, and use AutoCAD to optimize the layout design of the cutting sample. Then use the CNC cutting machine to cut the materials, mark the layers of the cut prepreg and stack them;

[0085] (4) Clean the molding mold, remove the core blocks in the mold in the order of numbers, and arrange them in sequence, prepare the pre-molding inserts, wipe the female mold of the molding mold, the pre-molding inserts and the molding core blocks with acetone, place the pre-molding inserts in the corresponding positions of the reserved opening covers, and finally evenly apply the medium-temperature release agent on the mold surface;

[0086] (5) First, lay a layer of plain carbon cloth along the inner surface of the mold, and then lay the outer skin in the order of [0 / +45 / 90 / -45 / -45 / 90 / +45 / 0] according to the laying angle. This laying sequence is repeated once; after each layer of prepreg is laid, no bubbles or bridging should appear. After laying, it is vacuum pre-compacted once;

[0087] (6) Lay reinforcing ribs at the bottom of the anti-sway plate, and after laying, lay a layer of medium-temperature adhesive film at the location where the foam is laid on the surface of the outer skin, and then lay the foam. The reinforcing ribs have a width of 9.8-10.2 mm, preferably 10 mm, and a thickness of 5.8-6.2 mm, preferably 6 mm. After the foam is laid, vacuum pre-compact it once;

[0088] (7) Lay a layer of medium-temperature adhesive film on the foam, and finally lay the inner skin in the same order according to the laying angle of [0 / +45 / 90 / -45 / -45 / 90 / +45 / 0]. Repeat this laying sequence once; after each layer of prepreg is laid, no bubbles or bridging should occur, and then lay a layer of plain carbon cloth;

[0089] (8) The core blocks are placed in the mold in the order of numbering, and the anti-sway plates and rubber strips are placed at the same time. The anti-sway plates are composite foam sandwich structures. The thickness of the composite materials on the left and right sides is 1 mm respectively. The composite material laying sequence is quasi-isotropic laying. When the anti-sway plates are placed, the composite materials covering the anti-sway plates on both sides should overlap with the inner skin. The rubber strips are made of high temperature resistant silicone rubber. The thickness of the rubber strips laid in the mold is 10 mm and 3 mm. They are laid in the gaps formed by the formed core blocks.

[0090] (9) Mold closing and curing: fasten the mold cover, tighten the pressure screws, check the mold clearance, and ensure that the mold clearance is ≤0.5mm; push the mold into the oven for curing, the mold curing temperature is 135±5℃, and the curing time is about 2h;

[0091] (10) Demolding and trimming: After curing, open the mold cover, remove the core block, take out the product, and trim the flash to obtain the composite material tank cover shell.

[0092] Example 3

[0093] Figure 4 The composite material oil tank lower cover of the present invention comprises an anti-sway plate 15, a rib plate 16, a steel bushing 17, a wire hole 18 and an overlap area 19. Figure 5 The composite material fuel tank lower cover shell forming mold of the present invention comprises a lower cover plate 20, an upper cover plate 21, a front side strip 22, a rear side strip 23, a left side strip 24, a right side strip 25, a forming core block 26, a preformed insert 27, and a pressure screw 28.

[0094] like Figure 4 , Figure 5 As shown, this embodiment provides a method for forming a composite material fuel tank lower cover, the steps are as follows:

[0095] (1) According to the product structure and appearance, taking into account the layup process and molding method, a solid model is established using 3D modeling software to design the molding mold based on various conditions. According to the design idea, the lower cover structure of the composite fuel tank is a thin-walled foam sandwich structure (outer skin + foam + inner skin). The layers are laid in the molding mold according to the female mold to ensure the product's external dimensions. At the same time, anti-sway plates, rib plates, molding core blocks, pre-molded inserts and rubber strips are placed in the female mold to ensure the complex internal structure of the fuel tank.

[0096] (2) The molding materials are selected according to the product characteristics and load-bearing requirements. In this embodiment, T300-grade plain carbon cloth / 9A16 prepreg, T700-grade unidirectional carbon fiber / 9A16 prepreg, domestic PMI foam (CK110-HT) and J-47A medium-temperature adhesive film with good draping performance are selected; the outer skin thickness of the composite fuel tank lower cover shell of this embodiment is 1.8-2.2mm, preferably 2mm, the foam thickness is 5.8-6.2mm, preferably 6mm, and the inner skin thickness is 1.8-2.2mm, preferably 2mm; the total thickness of the anti-sway plate composite material is 1.5-2mm, preferably 2mm, and the foam thickness is 2.8-3.2mm, preferably 3mm; the total thickness of the rib plate composite material is 5.8-6.2mm, preferably 6mm, and the foam thickness is 3.8-4.2mm, preferably 4mm;

[0097] (3) Use 3D digital modeling software to lay out the prepreg samples of the product, and use AutoCAD to optimize the layout design of the cutting sample. Then use the CNC cutting machine to cut the materials, mark the layers of the cut prepreg and stack them;

[0098] (4) Clean the forming mold, remove the core blocks in the mold in the order of numbers, and arrange them in sequence, prepare the pre-molding inserts, wipe the female mold of the forming mold, the pre-molding inserts and the forming core blocks with acetone, place the pre-molding inserts in the corresponding positions of the reserved wire holes and steel bushings, and finally evenly apply the medium-temperature release agent on the mold surface;

[0099] (5) First, lay a layer of plain carbon cloth along the inner surface of the mold, and then lay the outer skin in the order of [0 / +45 / 90 / -45 / -45 / 90 / +45 / 0], and repeat this laying sequence once; after each layer of prepreg is laid, no bubbles or bridging should occur, and after laying, it should be vacuum pre-compacted once;

[0100] (6) Lay reinforcing ribs at the bottom of the anti-sway plate, and after laying, lay a layer of medium-temperature adhesive film at the location where the foam is laid on the surface of the outer skin, and then lay the foam. The reinforcing ribs have a width of 9.8-10.2 mm, preferably 10 mm, and a thickness of 5.8-6.2 mm, preferably 6 mm. After the foam is laid, vacuum pre-compact it once;

[0101] (7) Lay a layer of medium-temperature adhesive film on the foam, and finally lay the inner skin in the same order according to the laying angle of [0 / +45 / 90 / -45 / -45 / 90 / +45 / 0]. This laying sequence is repeated once; after each layer of prepreg is laid, no bubbles or bridging should occur, and then a layer of plain carbon cloth is laid;

[0102] (8) The core blocks are placed in the mold in the order of numbering, and the anti-sway plates, rib plates and rubber strips are placed at the same time. The anti-sway plates and rib plates are composite foam sandwich structures. The thickness of the composite materials on the left and right sides of the anti-sway plates is 1 mm, and the thickness of the composite materials on the left and right sides of the rib plates is 3 mm. The composite material laying order is quasi-isotropic laying. When placing the anti-sway plates and rib plates, the composite materials covering the anti-sway plates and rib plates on both sides should overlap with the inner skin. The rubber strip is made of high temperature resistant silicone rubber. The thickness of the rubber strips laid in the mold is 10 mm and 3 mm, and they are laid in the gap formed by the formed core blocks;

[0103] (9) Mold closing and curing: fasten the mold cover, tighten the pressure screws, check the mold clearance, and ensure that the mold clearance is ≤0.5mm; push the mold into the oven for curing, the mold curing temperature is 135±5℃, and the curing time is about 2h;

[0104] (10) Demolding and trimming: After curing, open the upper cover plate of the mold, remove the core block, take out the product, and trim the flash to obtain the composite material fuel tank lower cover shell.

[0105] Example 4

[0106] like Figure 6As shown, holes for oil pipes are drilled on the front end and rear end of the lower cover of the composite material oil tank and on the internal anti-sway plate, and oil pipes 29 and 30 are respectively installed at the lowest point and the highest point of the oil tank, and then adhesive is applied to the interface between the oil pipes and the composite material and a sealing ring is installed, and then the inner and outer nuts of the oil pipes are tightened to complete the installation of the oil pipes; the lowest point is the position where the oil pipe contacts the inner bottom surface of the lower cover, and the highest point is the position where the oil pipe contacts the inner bottom surface of the upper cover, and the sealing ring is a commercially available rubber ring containing fluorine.

[0107] Among them, the highest point oil pipe is the oil filling pipe, in order to ensure that the oil tank can be filled with oil; the lowest point oil pipe is the oil drain pipe, in order to ensure that the oil tank can be drained of oil.

[0108] Example 5

[0109] like Figure 7 As shown, place the upper cover and lower cover of the composite fuel tank horizontally and stably, then evenly apply adhesive on the overlapping area of ​​the upper cover and the lower cover, buckle the upper cover onto the lower cover steadily, use straps to tie the upper / lower cover for pressurized curing, and cure at room temperature for about 12 hours. After curing, remove the straps, grind and trim the bonding area to ensure that the surface is flat and free of thorns; the straps are military straps, and are tied evenly with 5 straps at intervals to ensure that the adhesive can flow out from the overlapping area of ​​the upper and lower covers and there is no gap in the overlapping area of ​​the upper and lower covers.

[0110] The pressure resistance test shows that the composite fuel tank manufactured by the present invention fully meets the use requirements, and realizes the application of lightweight composite fuel tanks in the field of large missile body compartments.

[0111] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0112] The specific embodiments of the present invention disclosed above in conjunction with the accompanying drawings are intended to help understand the content of the present invention and implement it accordingly. Those of ordinary skill in the art can understand that various replacements, changes and modifications are possible without departing from the spirit and scope of the present invention. The present invention should not be limited to the contents disclosed in the embodiments of this specification. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, those of ordinary skill in the art can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, all of which belong to the protection of the present invention.

Claims

1. A lightweight composite fuel tank for missiles. It is characterized in that It comprises a composite fuel tank upper cover and a composite fuel tank lower cover; the composite fuel tank upper cover and the composite fuel tank lower cover are thin-walled foam sandwich structures, including an outer skin, foam, and an inner skin; the composite fuel tank upper cover and the composite fuel tank lower cover are sealed by adhesive; the outer skin and the inner skin are made of unidirectional prepreg, and are quasi-isotropically laid in sequence according to the laying angles of [0 / +45 / 90 / -45 / -45 / 90 / +45 / 0]; an anti-sway plate is arranged inside the composite fuel tank upper cover, and the anti-sway plate and the composite fuel tank upper cover are integrally cured and formed; an anti-sway plate and a rib plate are arranged inside the composite fuel tank lower cover, and the anti-sway plate and the rib plate are connected to the composite fuel tank The lower cover is integrally solidified and formed; reinforcing ribs are laid at the bottom of the anti-sway plate and the rib plate to improve the compressive resistance of the composite material tank; the thickness of the outer skin is 1.8-2.2mm, the thickness of the foam is 5.8-6.2mm, and the thickness of the inner skin is 1.8-2.2mm, wherein a layer of adhesive film is laid between the outer skin, the inner skin and the foam, and between the foams; the anti-sway plate and the rib plate are foam sandwich structures, namely "composite material + foam + composite material", the total thickness of the composite material of the anti-sway plate is 1.5-2mm, the thickness of the foam is 2.8-3.2mm, the total thickness of the composite material of the rib plate is 5.8-6.2mm, and the thickness of the foam is 3.8-4.2mm.

2. The lightweight composite fuel tank for missiles according to claim 1, It is characterized in that The material of the outer skin and the inner skin is fiber-reinforced resin; in the fiber-reinforced resin, the fiber is carbon fiber and the resin is a medium-temperature epoxy resin system; the foam is a polymethacrylimide foam core board.

3. A method for manufacturing a lightweight composite fuel tank for missiles as claimed in claim 1 or 2, It is characterized in that The following steps are involved: Molded composite fuel tank cover; Molded composite fuel tank lower cover; Installing oil pipes in the composite fuel tank lower cover; Bonding composite fuel tank upper cover and composite fuel tank lower cover; The molded composite material fuel tank upper cover comprises: (1) Based on the shape and internal structure of the fuel tank, the molding mold is designed using 3D modeling software. The inner shape of the mold is required to be consistent with the outer shape of the fuel tank cover. The molding core block is designed in the mold to ensure the molding of the complex structure inside the fuel tank shell; (2) Manufacturing a forming mold according to the established three-dimensional structural model, wherein the forming mold includes an upper cover plate, a lower cover plate, front and rear side strips, left and right side strips, a forming core block, a preformed insert, and a pressurized fastening screw; the lower cover plate and the front and rear side strips and the left and right side strips form an outer mold with an upper opening, and after all the layers are laid, the upper cover plate closes the mold; the forming core block and the preformed insert are used to form the complex internal structure of the fuel tank, including the integral forming of the anti-sway plate and the reservation of the positions of the equipment cover and the left and right covers, and a fuel tank shell that meets the internal quality and structural strength is obtained by placing a rubber film between the forming core blocks for pressurized and heated expansion; (3) Laying out the outer skin, reinforcing ribs, foam, and inner skin in sequence in the outer mold with an opening at the upper end, and performing vacuum pre-compaction once after the outer skin and foam are laid out; the outer skin and the inner skin are made of unidirectional prepreg, and are quasi-isotropically laid out in sequence according to the layup angles of [0 / +45 / 90 / -45 / -45 / 90 / +45 / 0]; (4) After the inner skin is laid, the forming core blocks, anti-sway plates and rubber strips are laid in the mold in order; (5) After laying, buckle the upper cover plate onto the mold and check the mold gap. If the mold gap is too large, check whether the upper cover plate is completely fastened to the mold around the mold to see if there is any jamming. If there is no jamming, tighten the pressure screws until the mold gap is met and the mold is closed. (6) Pushing the mold after mold closing into the oven for curing; (7) After curing, open the upper cover plate, remove the core block in the mold, take out the product, and trim the flash to obtain the composite material tank upper cover; The molded composite material fuel tank lower cover comprises: (1) Based on the shape and internal structure of the fuel tank, the mold is designed using 3D modeling software. The inner shape of the mold is required to be consistent with the outer shape of the fuel tank lower cover. The mold core is designed to ensure the complex structure inside the fuel tank shell is formed; (2) Manufacturing a forming mold according to the established three-dimensional structural model, the forming mold comprising an upper cover plate, a lower cover plate, front and rear side strips, left and right side strips, a forming core block, a preformed insert, and pressurized fastening screws; the lower cover plate and the front and rear side strips and the left and right side strips form an outer mold with an upper opening, and after all the layers are laid, the upper cover plate closes the mold; the forming core block and the preformed insert are used to form the complex internal structure of the fuel tank, including the integral forming of the anti-sway plate and the rib plate, and the reservation of the position of the wire hole and the steel bushing. A fuel tank shell that meets the internal quality and structural strength is obtained by placing a rubber film between the forming core blocks for pressurized and heated expansion; (3) Laying out the outer skin, reinforcing ribs, foam, and inner skin in sequence in the outer mold with an opening at the upper end, and performing vacuum pre-compaction once after the outer skin and foam are laid out; the outer skin and the inner skin are made of unidirectional prepreg, and are quasi-isotropically laid out in sequence according to the layup angles of [0 / +45 / 90 / -45 / -45 / 90 / +45 / 0]; (4) After the inner skin is laid, the core blocks, anti-sway plates, rib plates and rubber strips are laid in the mold in order; (5) After laying, buckle the upper cover plate onto the mold and check the mold gap. If the mold gap is too large, check whether the upper cover plate is completely fastened to the mold around the mold to see if there is any jamming. If there is no jamming, tighten the pressure screws until the mold gap is met and the mold is closed. (6) Pushing the mold after mold closing into the oven for curing; (7) After the curing is completed, the upper cover is opened to remove the core block in the mold, and the product is taken out for flash trimming to obtain the composite material fuel tank lower cover.

4. The method according to claim 3, It is characterized in that The method of installing an oil pipe in a composite oil tank lower cover comprises: using a hole opener to open holes in an anti-sway plate inside the composite oil tank lower cover and in the front and rear of the composite oil tank lower cover, and then installing the oil pipe, while sealing the openings, and tightening inner and outer nuts that fix the oil pipe to complete the installation of the oil pipe.

5. The method according to claim 3, It is characterized in that The method for bonding a composite material fuel tank upper cover and a composite material fuel tank lower cover comprises: (1) Apply adhesive evenly to the overlapping area of ​​the composite fuel tank upper cover and the composite fuel tank lower cover; (2) Smoothly buckle the composite fuel tank upper cover onto the composite fuel tank lower cover, ensuring that the overlapping areas are completely butted together and that adhesive can be squeezed out of the overlapping seams; (3) Use straps or place heavy objects on the top of the tank to pressurize and cure; (4) After curing, grind and trim the bonding area to ensure that the surface is smooth and free of burrs.

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