Manufacturing method of composite tubular structure product

Abstract

The invention relates to the technical field of composite material manufacturing, and discloses a manufacturing method of a composite material tubular structure product, which comprises the following steps of: effectively solving the problems of thermal deformation and large weight in the traditional metal plate welding process through an innovative staggered platform laying layer design and an autoclave and vacuum bag pressing prepreg forming process; and in the composite material bonding process, the strength of the joint is insufficient, and the overall strength is poor. Meanwhile, the technological process is simple and efficient, the cost is low, and the final product has good surface smoothness and attractiveness.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material manufacturing, and more specifically, it relates to a manufacturing method for a composite material tubular structure product. Background Art

[0002] At present, the composite material industry is developing at a high speed. Due to the characteristics of low density and high strength, composite materials are gradually replacing the original sheet metal parts or other structural materials. However, for the manufacturing of some special-shaped parts, there is currently no relatively good method for composite materials. The traditional manufacturing processes for special-shaped parts mainly adopt two technical solutions: sheet metal welding forming and composite material split bonding. One is to regard the manufacturing of special-shaped parts as being formed by a mold; the other is a manufacturing system composed of simple combinations. The former realizes structural integration through welding based on the ductility characteristics of metal materials, and the latter completes overall assembly through adhesive bonding relying on the split mold preparation of composite materials. Most of these methods are based on existing basic forming and joining technologies, and it is difficult to meet the increasingly high process requirements of modern manufacturing for lightweight and high-strength special-shaped parts.

[0003] Therefore, how to ensure structural integrity, achieve lightweight and high-strength manufacturing of special-shaped parts, and avoid the unsightly situation caused by hand lay-up while the traditional sheet metal welding and composite material bonding processes are not completely reliable has become an urgent problem to be solved. Summary of the Invention

[0004] The present invention provides a manufacturing method for a composite material tubular structure product, which solves the technical problem in the prior art of being able to ensure structural integrity, achieve lightweight and high-strength manufacturing of special-shaped parts, and avoid the unsightly situation caused by hand lay-up while the traditional sheet metal welding and composite material bonding processes are not completely reliable.

[0005] The present invention provides a manufacturing method for a composite material tubular structure product, including upper and lower metal molds, and further comprising the following steps:

[0006] Coat the surfaces of the upper and lower metal molds with a release agent.

[0007] Lay up prepregs on the upper mold and the lower mold respectively.

[0008] During the laying-up process on the metal mold, perform stepped lay-up on the prepregs. The stepped lay-up stops after extending a certain distance from the mold edge inward, so that the prepregs can overlap each other at the joint after the upper and lower molds are closed.

[0009] After the stepped lay-up is completed, close the upper and lower molds. The positions reserved by the stepped lay-ups on both sides overlap each other, and use a pressing plate to press flat from the inside to the inner surface of the mold.

[0010] After the mold is closed according to the vacuum bag pressing process, the mold is vacuum bagged to package the product;

[0011] The packaged product is placed in an autoclave or an oven and cured at high temperature to form a shape;

[0012] After the product is cured and formed, the vacuum bag film and the release cloth on the surface of the mold and the inner surface of the product are removed, and the mold seam on the surface of the product is polished to obtain a finished composite material tubular structure.

[0013] Further, it includes an external metal mold and an internal metal core mold, and also includes another product manufacturing step, which is specifically as follows:

[0014] Apply a release agent to the external metal mold and the internal metal core mold;

[0015] The release agent treatment includes applying 2-3 layers of a silicone-based release agent or a wax-based release agent, with a waiting time of 3-5 minutes between each layer;

[0016] Lay up prepreg on the surface of the inner core mold;

[0017] Place the inner core mold into the external mold and close the mold;

[0018] Vacuum bag the entire closed mold through the vacuum bag pressing process;

[0019] Perform vacuum pumping on the vacuum bag and check the vacuum degree;

[0020] Place the vacuum-treated closed mold into an oven or an autoclave for curing;

[0021] After curing is completed, remove the vacuum bag, open the closed mold, and take out the core mold and the product;

[0022] According to the design of the core mold, perform segmented demolding operations;

[0023] Finally, perform post-treatment on the product to obtain a finished composite material tubular structure.

[0024] Further, the prepreg is one or a combination of several of carbon fiber prepreg, glass fiber prepreg or aramid fiber prepreg.

[0025] Further, the height of the stepped ply is 1.5-2 times the wall thickness of the product, and the length of the stepped ply is 5-10 times the wall thickness of the product.

[0026] Further, the temperature for high-temperature curing and forming is 120-180 °C, the curing time is 2-4 hours, and the heating rate and the cooling rate are both controlled at 2-3 °C / minute.

[0027] Furthermore, the vacuum pressure in the vacuum bag pressing process is 0.7 - 1.0 MPa.

[0028] Furthermore, the laying methods of the prepreg include: alternating laying of 0° and 90°; composite angle laying of 0°, 45° and 90°.

[0029] Furthermore, the prepreg is laid in segments, and there is an overlapping area of 50 - 100 mm between adjacent segments.

[0030] Furthermore, the pressing plate is made of metal material or composite material, and a release agent is applied on its surface.

[0031] Furthermore, the vacuum bag pressing process includes laying a layer of release cloth on the outer surface of the mold, laying a layer of breather felt on the release cloth, placing a vacuum valve, wrapping the whole mold with a vacuum bag film, and sealing the edge of the mold with a sealing strip.

[0032] The beneficial effects of the present invention are as follows: Through the innovative stepped layering design and the autoclave and vacuum bag pressing prepreg forming process, the present invention effectively solves the problems of thermal deformation and large weight existing in the traditional sheet metal welding process, as well as the technical defects of insufficient strength at the joints and poor overall strength in the composite material bonding process. At the same time, this process is simple and efficient, with low cost, and the final product has good surface finish and aesthetics. Brief Description of the Drawings

[0033] Figure 1 Schematic diagram of the upper and lower metal molds provided by the embodiment of the present invention;

[0034] Figure 2 Schematic three - dimensional diagram of the upper and lower molds provided by the embodiment of the present invention;

[0035] Figure 3 Schematic diagram of the stepped layering of the prepreg provided by the embodiment of the present invention;

[0036] Figure 4 Schematic diagram of the layering and stepping of the prepreg provided by the embodiment of the present invention;

[0037] Figure 5 Schematic diagram of the interlacing of the steps after the upper and lower molds are closed in the embodiment of the present invention;

[0038] Figure 6 Schematic diagram of laying the release cloth on the surface and wrapping the whole with the vacuum bag film in the embodiment of the present invention;

[0039] Figure 7 Schematic diagram of the final product forming in the embodiment of the present invention. Detailed Description of the Embodiment

[0040] Reference will now be made to example embodiments to discuss the subject matter described herein. It should be understood that discussing these embodiments is only to enable those skilled in the art to better understand and thus implement the subject matter described herein, and that changes can be made to the functions and arrangements of the elements discussed without departing from the scope of protection of the content of this specification. Each example can omit, substitute, or add various processes or components as needed. Additionally, the features described in some examples can also be combined in other examples.

[0041] In at least one embodiment of the present invention, a method for manufacturing a composite material tubular structure product is disclosed, including upper and lower metal molds, and further including the following steps:

[0042] As Figure 1 shown, coat the surfaces of the upper and lower metal molds with a release agent;

[0043] Lay prepregs on the upper mold and the lower mold respectively;

[0044] During the laying process of the prepregs on the metal molds, perform stepped laying, and the stepped laying stops after extending a certain distance inward from the edge of the mold, so that the prepregs can overlap each other at the joint after the upper and lower molds are closed;

[0045] After the stepped laying is completed, close the upper and lower molds, and the positions reserved by the stepped laying on both sides overlap each other, and use a pressing plate to press flat from the inside to the inner surface of the mold;

[0046] According to the vacuum bag pressing process, perform vacuum bag packaging treatment on the mold after closing the mold to package the product;

[0047] Put the packaged product into an autoclave or an oven and cure it at a high temperature;

[0048] After the product is cured and formed, remove the vacuum bag film and release cloth on the surface of the mold and the inner surface of the product, and polish the joint seam on the surface of the product to obtain a finished composite material tubular structure.

[0049] Another preferred embodiment of the present invention includes an external metal mold and an internal metal core mold, and further includes another product manufacturing step, specifically as follows:

[0050] Apply a release agent to the external metal mold and the internal metal core mold;

[0051] The release agent treatment includes applying 2 - 3 layers of a silicone-based release agent or a wax-based release agent, and waiting for 3 - 5 minutes between each layer;

[0052] Lay prepregs on the surface of the internal core mold;

[0053] Put the internal core mold into the external mold and close the mold;

[0054] Vacuum bag encapsulation of the entire mold clamping mold is carried out through the vacuum bag pressing process;

[0055] The vacuum bag is subjected to vacuum pumping treatment, and the vacuum degree is checked;

[0056] The mold clamping mold after vacuum treatment is placed in an oven or autoclave for curing;

[0057] After curing is completed, the vacuum bag is removed, the mold clamping mold is opened, and the core mold and the product are taken out;

[0058] According to the design of the core mold, segmented demolding operations are carried out;

[0059] Finally, post-treatment is carried out on the product to obtain a finished composite material tubular structure;

[0060] Post-treatment of the product includes:

[0061] (1) Remove excess resin and burrs on the surface of the product;

[0062] (2) Polish the mold clamping seam with 400-600 mesh fine sandpaper;

[0063] (3) Clean and inspect the surface of the product;

[0064] (4) Carry out surface treatment as required, such as painting and waxing;

[0065] (5) Conduct final inspection on the product size and appearance.

[0066] Specifically, multiple experimental verifications are carried out according to the above operation methods:

[0067] (1) Experimental verification of the optimization of the height and length of the stepped joint:

[0068] Experimental conditions: Tubular structure specimens with a wall thickness of 3 mm and a length of 200 mm; T300 grade carbon fiber prepreg is used, and the resin content is 40 ± 2%.

[0069] Stepped joint parameter settings:

[0070] Height group: 3 mm, 4.5 mm, 6 mm, 7.5 mm (1 - 2.5 times the wall thickness);

[0071] Length group: 15 mm, 21 mm, 27 mm, 33 mm (5 - 11 times the wall thickness).

[0072] Testing methods: Shear strength: According to the GB / T 7124 standard; Peel strength: According to the ASTM D1781 standard.

[0073] The stepped joint height is set to 3 mm, 4.5 mm, 6 mm, 7.5 mm (1 - 2.5 times the wall thickness);

[0074] The stepped lengths are respectively set to 15 mm, 21 mm, 27 mm, 33 mm (5 - 11 times the wall thickness);

[0075] The test results are shown in Table 1 and Table 2:

[0076] Table 1: Data of height group (shear strength MPa):

[0077] Step height 3mm 4.5mm 6mm 7.5mm Average value 42 56 58 51 Standard deviation ±2.1 ±1.8 ±1.9 ±2.3

[0078] Table 2: Data of length group (peel strength N / mm):

[0079] Step length 15mm 21mm 27mm 33mm Average value 7.8 8.5 8.4 7.6 Standard deviation ±0.3 ±0.2 ±0.3 ±0.4

[0080] The test results show that:

[0081] When the stepped height is 1.5 - 2 times the wall thickness (4.5 - 6 mm), the joint shear strength is relatively high, reaching 56 - 58 MPa;

[0082] When the stepped length is 5 - 10 times the wall thickness (15 - 30 mm), the joint peel strength is better, reaching 8.4 - 8.5 N / mm.

[0083] (2) Optimization experiment of curing process parameters:

[0084] Specimen specifications: 100 mm × 100 mm flat plate, 16 - layer ply;

[0085] Parameter settings:

[0086] Temperature group: 100 °C, 120 °C, 180 °C, 200 °C;

[0087] Time group: 1 h, 2 h, 3 h, 4 h, 5 h;

[0088] Heating and cooling rate group: 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min.

[0089] The key result data are shown in Table 3:

[0090] Table 3: Influence of temperature (curing for 2 h):

[0091] Temperature (°C) Degree of cure (%) ILSS (MPa) Tg (°C) 100 98.2 65 128 120 99.3 68 142 180 99.5 69 145 200 99.1 67 140

[0092] Test of curing temperature range: 100 °C - 200 °C;

[0093] Test of curing time range: 1 - 5 hours, with an interval of 1 hour;

[0094] Heating and cooling rate test: 1 - 4 °C / min, with an interval of 0.5 °C / min;

[0095] The test results show that: within the temperature range of 120 - 180 °C, the resin curing degree > 98%; a curing time of 2 - 4 hours can ensure complete curing; a heating and cooling rate of 2 - 3 °C / min can avoid thermal stress cracking;

[0096] (3) Vacuum pressure optimization experiment:

[0097] Standard tubular structure specimens, with an inner diameter of 50 mm and a wall thickness of 3 mm; T300 / epoxy prepreg, 0° - 90° layup;

[0098] Test pressures: 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 MPa

[0099] The test results are shown in Table 4:

[0100] Table 4: Influence results of vacuum pressure

[0101] Pressure (MPa) Void fraction (%) Fiber volume fraction (%) Flexural strength (MPa) 0.5 2.8 56.5 780 0.7 0.9 59.8 865 0.9 0.8 60.2 870 1.0 0.7 60.5 868

[0102] The test results show that:

[0103] The interlayer bonding is optimal within the pressure range of 0.7 - 1.0 MPa; the porosity is controlled below 1%;

[0104] The fiber volume fraction reaches 60 ± 2%.

[0105] (4) Layup method optimization experiment:

[0106] Tubular structure specimens, with an inner diameter of 50 mm and a wall thickness of 3 mm; using the same material system and process parameters;

[0107] 5 specimens for each layup method;

[0108] Performance comparison table of layup schemes:

[0109]

[0110]

[0111] Overlap area: 30, 50, 70, 90, 110 mm

[0112] Test items: Axial compressive strength; Circumferential compressive strength; Torsional strength. Comprehensive performance test results:

[0113] [0°, ±45° and 90°] layup, 70 mm overlap area is optimal:

[0114] Axial compressive strength: 685 MPa;

[0115] Circumferential compressive strength: 175 MPa;

[0116] Torsional strength: 168 MPa.

[0117] (5) Release agent coating process experiment:

[0118] Surface of standard metal mold;

[0119] Comparison between silicon-based release agent and wax-based release agent;

[0120] Ambient temperature 23 ± 2 °C, relative humidity 50 ± 5%.

[0121] Release agent performance comparison table:

[0122]

[0123]

[0124] Coating layers: 1 - 5 layers;

[0125] Interlayer waiting time: 1 - 10 minutes;

[0126] Evaluation index: Ease of demolding (1 - 5 point scale);

[0127] Product surface quality; Release agent residue situation; Optimal process parameters.

[0128] Silicon-based release agent: 3 layers, interlayer waiting for 4 minutes;

[0129] Wax-based release agent: 2 layers, interlayer waiting for 5 minutes.

[0130] All experiments were carried out under standard laboratory conditions (23 ± 2 °C, 50 ± 5% RH). Each set of parameters was tested more than 3 times, and the data was statistically analyzed. The coefficient of variation was controlled within 5%. Through the above systematic experimental verification, a reliable scientific basis was provided for the selection of process parameters.

[0131] Example 1

[0132] Prepare the upper and lower molds of the metal mold, where the internal shapes of the upper and lower molds correspond to the external and internal shapes of the product respectively. The mold material can be selected from aluminum alloy, steel or other metal materials suitable for the vacuum bag pressing process. The mold surface should be smooth and free of damage to ensure the product surface quality.

[0133] Perform release agent treatment on the mold surface. Specifically, use a special release agent to evenly coat the inner surfaces of the upper and lower molds, ensure that the release agent completely covers the mold surface, and wait for the release agent to dry. The release agent can be selected from silicon-based release agent or wax-based release agent, apply 2 - 3 layers, and wait 3 - 5 minutes between each layer to ensure good demolding effect.

[0134] As Figure 3 and Figure 4 shown, prepregs are respectively laid on the upper mold and the lower mold. In this embodiment, the prepreg can be a carbon fiber prepreg, a glass fiber prepreg or an aramid fiber prepreg, and preferably a carbon fiber prepreg is adopted. According to the design requirements of the product, unidirectional fiber prepregs or multi-directionally woven prepregs can be selected. The laying method of the prepreg can be designed according to the stress condition of the product, and 0° and 90° can be alternately laid; or 0°, 45° and 90° composite angles can be laid.

[0135] During the process of laying on the mold, the prepregs should be laid in a stepped manner. The stepped laying is a key step of the present invention. Specifically, the height of the staggered layers is 1.5 - 2 times the wall thickness of the product, and the length of the stagger is 5 - 10 times the wall thickness of the product. For example, when the wall thickness of the product is 3 mm, the stagger height is 4.5 - 6 mm, and the stagger length is 15 - 30 mm.

[0136] In this embodiment, an epoxy resin-based carbon fiber prepreg is used, with a resin content of 38 ± 2%, a surface density of 200 g / m 2 , and the laying thickness is 0.2 mm / layer.

[0137] As Figure 5 shown, after the laying is completed, the upper and lower molds are closed, and the positions reserved for the staggered layers on both sides are staggered with each other, and a pressing plate is used to flatten the inner surface from the inside of the mold. The pressing plate can be made of a metal material or a composite material, and a release agent should be applied to its surface to prevent adhesion to the prepreg

[0138] As Figure 6 shown, after the mold closing is completed, according to the operation process of the vacuum bag pressing process, a release cloth is laid on the surface and the whole is wrapped with a vacuum bag film. The specific steps include:

[0139] Lay a layer of release cloth on the outer surface of the mold, and the release cloth should cover the entire surface of the mold;

[0140] Lay a layer of breather felt on the release cloth for assisting in vacuum pumping;

[0141] Place a vacuum valve to ensure good contact between the vacuum valve and the breather felt;

[0142] Wrap the whole mold with a vacuum bag film and seal it with a sealing strip at the edge of the mold;

[0143] Connect the vacuum valve to the vacuum pump and start vacuum pumping, and the vacuum pressure should reach 0.7 - 1.0 MPa;

[0144] Check the tightness of the vacuum system to ensure no air leakage.

[0145] As Figure 2 and Figure 3As shown, during the die laying process, the prepreg should be laid with a stepped layer. The stepped layer laying is a key step of the present invention. The specific height of the stepped layer is designed according to the thickness, number of layers and size of the product. In this embodiment, the height of the step is generally 1.5 - 2 times the wall thickness of the product, and the length of the step is 5 - 10 times the wall thickness of the product. For example, if the wall thickness of the product is 3mm, the step height is 4.5 - 6mm, and the step length is 15 - 30mm.

[0146] Put the packed product into an autoclave or an oven and cure it at high temperature. The curing temperature is controlled at 120 - 180 °C, the curing time is 2 - 4 hours, and the heating rate and cooling rate are both controlled at 2 - 3 °C / minute.

[0147] The specific method of stepped layer laying is as follows:

[0148] When laying the prepreg on the inner surface of the upper die, stop after extending a certain distance (i.e., the step length) from the edge of the upper die inward;

[0149] When laying the prepreg on the inner surface of the lower die, also stop after extending a certain distance from the edge of the lower die inward;

[0150] The position of the stepped layer should correspond to the joint after the upper and lower dies are closed.

[0151] After curing is completed, remove the vacuum bag film and release cloth on the surface of the die and the inner surface of the product, and polish the joint seam on the surface of the product.

[0152] This stepped layer laying method ensures that after the dies are closed, the prepregs on the upper and lower dies can overlap each other at the joint, thus forming a continuous fiber structure and improving the strength at the joint of the product.

[0153] Example 2

[0154] The selection and laying method of the prepreg in this embodiment:

[0155] The pressing plate can be made of metal materials or composite materials, and its surface should be coated with a release agent to prevent adhesion to the prepreg. During the die closing process, the accurate alignment of the upper and lower dies can be ensured through positioning pins or positioning tools.

[0156] As Figure 6 shown, after the die closing is completed, according to the operation process of the vacuum bag pressing process, lay the release cloth on the surface and wrap the whole with a vacuum bag film. The release cloth can be selected from nylon or polyester materials, and the vacuum bag film should be made of high-temperature resistant materials such as nylon film. During packaging, it is necessary to ensure that there is a complete seal between the vacuum bag and the die, and a sealing strip can be used for sealing. In addition, a vacuum valve needs to be installed on the vacuum bag for subsequent vacuum pumping operations.

[0157] The choice of prepreg can be: carbon fiber prepreg, glass fiber prepreg, aramid fiber prepreg, or a combination of several of the above prepregs.

[0158] The specific steps of the vacuum bag pressing process are as follows:

[0159] Lay a layer of release cloth on the outer surface of the mold, and the release cloth should cover the entire mold surface;

[0160] Lay a layer of breather felt on the release cloth for assisting in vacuum pumping;

[0161] Place the vacuum valve to ensure good contact between the vacuum valve and the breather felt;

[0162] Wrap the entire mold with a vacuum bag film and seal it at the edge of the mold with a sealing strip;

[0163] Connect the vacuum valve to the vacuum pump and start vacuum pumping. The vacuum pumping pressure should reach above 0.095 MPa;

[0164] Check the tightness of the vacuum system to ensure there is no air leakage.

[0165] Put the packed product into an autoclave or an oven for high-temperature curing and forming. For carbon fiber prepreg, the curing temperature is generally 120 - 180 °C, and the curing time is 2 - 4 hours. The specific curing temperature and time should be set according to the requirements of the prepreg resin system used. During the curing process, it is necessary to maintain a vacuum state, and the pressure is generally 0.7 - 1.0 MPa.

[0166] The manufacturing method of this embodiment for large composite tubular structure products adopts a segmented paving method:

[0167] Cut the prepreg into appropriately sized segments, and the length of each segment does not exceed 1 meter;

[0168] Pave the prepreg on the mold in segments, and keep an overlapping area of 50 - 100 mm between adjacent segments;

[0169] In the overlapping area, adopt an alternating paving method to ensure fiber continuity.

[0170] The control of the curing process parameters is crucial for the product quality, and the following points should be noted:

[0171] The heating rate should be controlled at 2 - 3 °C / minute to avoid the generation of bubbles inside the product due to too fast resin curing;

[0172] The curing temperature should be set according to the technical requirements of the prepreg. Too high or too low temperature will affect the product performance;

[0173] The curing time should be sufficient to ensure complete curing of the resin;

[0174] The cooling rate should also be controlled at 2 - 3 °C per minute to avoid deformation or cracking of the product due to thermal stress.

[0175] After curing is completed, remove the vacuum bag film and release cloth from the surface of the mold and the inner surface of the product, and polish the mold joint on the product surface. When polishing, attention should be paid not to damage the product surface, and fine sandpaper can be used for polishing.

[0176] The steps for product demolding and post - treatment are as follows:

[0177] After the mold is cooled to room temperature, remove the vacuum bag system;

[0178] Carefully take out the product from the mold;

[0179] Remove the excess resin or burrs on the product surface;

[0180] Use fine sandpaper (400 - 600 mesh) to polish the mold joint;

[0181] If necessary, surface treatments such as painting and waxing can be carried out.

[0182] Example 3

[0183] This example also provides an alternative solution for molding using inner and outer molds:

[0184] Based on Example 1, this example provides an alternative implementation method, that is, using a silicone bag or a PE vacuum bag inside the mold. The specific steps are as follows:

[0185] Prepare the upper and lower metal molds, and treat the mold surface with a release agent;

[0186] Use prepregs to lay on the upper and lower molds respectively, and the prepregs are laid with a stepped layer;

[0187] Lay a layer of silicone bag or PE vacuum bag on the inner surface of the upper and lower molds respectively;

[0188] After the layup is completed, close the upper and lower molds, and the stepped layers on both sides are staggered with each other;

[0189] Evacuate the inside of the vacuum bag through the vacuum pipeline set on the mold;

[0190] Fill the inside of the mold with compressed air through the inflation pipeline set on the mold to apply pressure to the product;

[0191] Put the mold into the oven for high - temperature curing;

[0192] After curing is completed, open the mold, take out the product, and polish the mold joint.

[0193] Example 4

[0194] The advantage of this embodiment is that through the pressure of the internal silica gel bag or PE vacuum bag, the inner surface of the product can be made more flat and smooth, which is suitable for occasions with high requirements for the inner surface quality of the product.

[0195] Based on Example 1, this embodiment provides a method of using different types of prepregs. In this embodiment, glass fiber prepreg is used as the main material, and carbon fiber prepreg is used to strengthen at key positions.

[0196] Prepare the upper and lower molds of the metal mold, and perform mold preparation and release agent treatment according to Example 1;

[0197] Lay 2 - 3 layers of glass fiber prepreg on the upper and lower molds as the base layer;

[0198] On the parts with greater stress, lay 1 - 2 layers of carbon fiber prepreg as the strengthening layer;

[0199] On the strengthening layer, lay 2 - 3 layers of glass fiber prepreg as the surface layer;

[0200] Perform stepped layering, mold closing, vacuum bag pressing and curing operations according to Example 1.

[0201] Example 5

[0202] The advantage of this embodiment is that by reasonably combining different types of prepregs, the product cost can be reduced while ensuring the strength requirements of key positions.

[0203] In addition, the present invention can also adopt the method of forming with internal and external molds, that is, using an internal metal core mold and an external mold to jointly form. However, this method needs to consider the mold splitting and demolding problems of the metal core mold, and the manufacturing process is relatively complex and the cost is relatively high. In contrast, the main embodiments of the present invention do not need to consider the demolding problem and the mold splitting problem, and can also save the cost of manufacturing the core mold.

[0204] The specific steps of the method of forming with internal and external molds are as follows:

[0205] Prepare an external metal mold and an internal metal core mold, and perform release agent treatment on the surfaces of the mold and the core mold;

[0206] Lay prepreg on the surface of the internal core mold;

[0207] Put the internal core mold into the external mold and close the mold;

[0208] According to the operation process of the vacuum bag pressing process, perform vacuum bag packaging on the entire mold system;

[0209] Evacuate the air and check the vacuum degree;

[0210] Place the mold system in an oven or autoclave for curing;

[0211] After curing is completed, remove the vacuum bag system, open the mold, and take out the core mold and the product;

[0212] According to the design of the core mold, perform segmented removal or other demolding operations;

[0213] Perform post-treatment on the product, such as sanding and painting.

[0214] Example 6

[0215] This method is applicable to products with relatively complex shapes and high quality requirements for both inner and outer surfaces. However, since a detachable internal core mold needs to be designed, the cost is relatively high and the operation is relatively complex.

[0216] Based on Example 1, this example provides a manufacturing method for large composite tubular structure products. For tubular structure products with a length exceeding 3 meters, due to the difficulty of one-time laying, a segmented laying method can be adopted:

[0217] Prepare the mold and process it according to Example 1;

[0218] Cut the prepreg into appropriately sized segments, with each segment not exceeding 1 meter in length;

[0219] Lay the prepreg on the mold in segments, with a 50 - 100 mm overlapping area between adjacent segments;

[0220] In the overlapping area, adopt an alternating laying method to ensure fiber continuity;

[0221] Perform stepped layering, mold closing, vacuum bag pressing, and curing operations according to Example 1.

[0222] This method is applicable to the manufacturing of large composite tubular structure products. By segmented laying and overlapping connection, the problem of difficult one-time laying of large products is solved.

[0223] Through the detailed description of the above embodiments, the technical solutions of the present invention have been clearly demonstrated. The present invention is not limited to the above embodiments, and those skilled in the art can make various deformations and improvements based on the technical solutions of the present invention, and these deformations and improvements should all fall within the scope of protection required by the present invention.

[0224] The above describes the embodiments of the present invention, but these embodiments are not limited to the above specific implementation manners. The above specific implementation manners are merely illustrative and not restrictive. Under the inspiration of this embodiment, those of ordinary skill in the art can also make more forms of the same embodiments, all of which fall within the protection scope of this embodiment.

Claims

1. A method for manufacturing a composite tubular structure product, comprising upper and lower metal molds, characterized in that: The following steps are also included: The surfaces of the upper and lower metal molds are coated with a release agent; Laying the prepreg on the upper mold and the lower mold respectively; During the metal mold laying process, the prepreg is staggered and laid. The staggered laying extends the prepreg inward from the edge of the mold for a certain distance and then stops, so that the prepreg can be staggered and overlapped at the joint after the upper and lower molds are closed; After the staggered layers are laid, the upper and lower molds are closed, the positions reserved for the staggered layers on both sides are staggered, and a pressing plate is used to flatten the inner surface of the mold from the inside; According to the vacuum bag pressing process, the mold is vacuum bagged after the mold is closed to package the product; Put the packaged products into an autoclave or oven for high temperature curing and forming; After the product is solidified and formed, the vacuum bag film and the demoulding cloth on the mold surface and the inner surface of the product are removed, and the mold seam on the product surface is polished to obtain a finished composite tubular structure.

2. A method for manufacturing a composite tubular structure product according to claim 1, comprising an external metal mold and an internal metal core mold, characterized in that: Another product preparation step is also included, which is as follows: Apply release agent to the external metal mold and the internal metal core mold; The release agent treatment comprises applying 2-3 layers of a silicone-based release agent or a wax-based release agent, and waiting for 3-5 minutes between each layer; Laying prepreg on the surface of the internal core mold; Place the inner core mold into the outer mold and close the mold; The entire mold is vacuum bagged by vacuum bagging process; Perform vacuum evacuation on the vacuum bag and check the vacuum degree; The vacuum-treated mold is placed in an oven or autoclave for curing; After curing is completed, remove the vacuum bag, open the mold, and take out the core mold and product; According to the design of the core mold, the demoulding operation is carried out in sections; Finally, the product is post-processed to obtain a finished composite tubular structure.

3. The method for manufacturing a composite tubular structure product according to claim 2, characterized in that: The prepreg is one or a combination of carbon fiber prepreg, glass fiber prepreg or aramid fiber prepreg.

4. The method for manufacturing a composite tubular structure product according to claim 1, characterized in that: The height of the staggered layers is 1.5-2 times the wall thickness of the product, and the length of the staggered layers is 5-10 times the wall thickness of the product.

5. The method for manufacturing a composite tubular structure product according to claim 1, characterized in that: The temperature of the high temperature curing molding is 120-180° C., the curing time is 2-4 hours, and the heating rate and cooling rate are both controlled at 2-3° C. / minute.

6. The method for manufacturing a composite tubular structure product according to claim 1, characterized in that: The vacuum pressure in the vacuum bagging process is 0.7-1.0 MPa.

7. The method for manufacturing a composite tubular structure product according to claim 1, characterized in that: The paving methods of the prepreg include: paving at 0° and 90° alternately; paving at a composite angle of 0°, 45° and 90°.

8. The method for manufacturing a composite tubular structure product according to claim 1, characterized in that: The prepreg is laid in sections, with an overlap area of ​​50-100 mm between adjacent sections.

9. The method for manufacturing a composite tubular structure product according to claim 1, characterized in that: The pressing plate is made of metal material or composite material, and a release agent is applied on the surface of the pressing plate.

10. The method for manufacturing a composite tubular structure product according to claim 2, characterized in that: The vacuum bagging process includes laying a layer of release cloth on the outer surface of the mold, laying a layer of breathable felt on the release cloth, placing a vacuum valve, wrapping the entire mold with a vacuum bag film, and sealing the edge of the mold with a sealing strip.

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