An in-situ conformal heating homogenization forming method for a profiled inner cavity composite cylindrical part

Abstract

This invention proposes an in-situ conformal heating and homogenization forming method for irregularly shaped internal cavity composite cylindrical parts. The method involves: designing a composite layup of carbon fiber prepreg and a heat-replenishing adhesive film; preparing the heating and heat-replenishing adhesive film; composite laying of the carbon fiber prepreg and the heat-replenishing adhesive film; bonding the heating film with a metal outer mold; curing reaction; demolding; and machining. This invention provides an in-situ conformal heating and homogenization forming method for irregularly shaped internal cavity composite cylindrical parts. It explores the forming mechanism under the coupled action of the homogenizing temperature field and pressure field, which are synergistically controlled by the heating film and the heat-replenishing adhesive film under varying thicknesses. This forms a macroscopic multi-scale temperature gradient integrated forming technology, achieving homogenized, low-cost, high-efficiency, and low-energy-consumption manufacturing of large-size complex cylindrical parts. This meets various mechanical performance indicators of the products and enables their application, enhancing the competitiveness of high-end composite products in the defense field.

Description

Technical Field

[0001] This invention belongs to the field of composite material forming technology, specifically relating to an in-situ conformal heating and homogenization forming method for irregularly shaped internal cavity composite cylindrical parts. Background Technology

[0002] Carbon fiber composites have outstanding advantages such as the lowest density, high specific strength, high specific stiffness, corrosion resistance, high temperature resistance, and fatigue resistance. However, the internal structure of composite cylindrical parts is a multi-ribbed, multi-windowed, and multi-flange irregular structure with varying dimensions. The temperature field of traditional autoclave molding is uneven, resulting in large deviations in shell consistency, temperature resistance, mechanical properties, and stability, which seriously affects the reliability and large-scale application of composite shells. Specifically, the reasons why the products cannot be homogeneously formed at present are as follows: (1) Due to the heating method and air duct during the autoclave molding process, the circumferential temperature difference of the product is large (temperature difference ≥ 30℃); (2) The product is thick and complex in structure, and the anisotropy of the fibers leads to a large temperature difference between the inner and outer layers, especially for irregular structures with varying thickness.

[0003] Meanwhile, traditional autoclave molding suffers from low efficiency and high energy consumption, resulting in high manufacturing costs and excessively long production cycles for composite cylindrical parts. This makes it difficult to meet the critical demands of the current defense industry for low-cost, large-scale mass production and rapid response manufacturing. Therefore, developing key technologies for low-cost, high-efficiency homogeneous forming is a necessary way to solve the above-mentioned bottlenecks. Summary of the Invention

[0004] The purpose of this invention is to provide an in-situ conformal heating and homogenization forming method for irregularly shaped internal cavity composite cylindrical parts. This method solves the technical problems of complex structures and uneven internal temperatures in composite cylindrical parts. By employing in-situ conformal heating and homogenization forming technology for composite cylindrical parts, this invention explores the forming mechanism under the coupling effect of the homogenization temperature field and pressure field, which is controlled by the synergistic control of the heating film and the heat-replenishing adhesive film under varying thickness. Combined with the resin gradient distribution controlled by canisterless adhesive absorption, a macroscopic multi-scale temperature gradient integrated forming technology is formed. Without using conventional pressurization equipment such as autoclaves or molding equipment, this invention achieves homogenization, low cost, high efficiency, and low energy consumption manufacturing of large-size complex cylindrical parts, meeting various mechanical performance indicators and enabling applications. This enhances the competitiveness of high-end composite products in the defense field.

[0005] A method for in-situ conformal heating and homogenization forming of irregularly shaped internal cavity composite cylindrical parts, specifically including the following steps:

[0006] Step S1: Design and analyze composite cylindrical components;

[0007] Step S2: Composite layup design of carbon fiber prepreg and heat-repairing adhesive film;

[0008] Step S3: Preparation of the heating film and heat-repairing adhesive film of homogeneous resin;

[0009] Step S4: Composite laying of carbon fiber prepreg and heat-repairing adhesive film;

[0010] Step S5: The heating film is bonded to the metal outer mold;

[0011] Step S6: Curing reaction;

[0012] Step S7: Demolding and machining.

[0013] In step S2, Abaqus software is used to embed the operation mode of the heat-repairing adhesive film, so as to simulate and separate the temperature field of the material with varying thickness.

[0014] Based on the variable thickness structure, the heat-repairing adhesive film is embedded in the carbon fiber prepreg, and the temperature field, modal, static stiffness and stability are simulated to determine and optimize the position of the heat-repairing adhesive film, so as to achieve uniform temperature distribution with variable thickness.

[0015] In step S4, according to the simulation design results, the carbon fiber prepreg is laid up according to the angle and number of layers, for example, by manual or electric iron heat-pressure coupling, and the heat-reinforcing adhesive film is applied to the surface of the carbon fiber prepreg, similar to the heat-pressure coupling of an electric iron. The axial dimension of the heat-reinforcing adhesive film is larger than that of the carbon fiber prepreg, with 10mm at each end, and then the carbon fiber prepreg is laid up again.

[0016] After the composite layup is completed, the front and rear heat-reinforcing adhesive films are connected to the electrodes and circuitry.

[0017] In step S5, the pre-prepared uniform conformal heating film is adhered to the surface of the metal outer mold with an adhesive. The temperature uniformity inside the metal outer mold is tested by powering on. The specific parameters are: voltage -5V DC, temperature difference ≤1℃, operating range room temperature -280℃, and temperature difference standard of uniform temperature field is ±2℃. Then, the composite material after composite layup is molded.

[0018] When vacuuming a vacuum bag, ensure that the wires and thermocouples pass through the sealing strip of the vacuum bag to prevent air leakage.

[0019] In step S6, under the uniform temperature field and conventional pressure of the heating film and the heat-repairing adhesive film, the components of the thermosetting resin undergo a curing and cross-linking reaction.

[0020] The positive effects of this invention are as follows:

[0021] (1) This solution has the advantages of homogeneous molding, low cost, low energy consumption and high efficiency. It replaces the traditional bulky autoclave, significantly reduces asset investment, shortens heating time, improves production efficiency, optimizes resin curing quality and consistency, and enhances product quality stability.

[0022] This technology has overcome the bottlenecks of traditional autoclave forming, such as low efficiency, high cost, and high energy consumption, achieving a 30% reduction in cost, a 40% increase in efficiency, a 40% reduction in energy consumption, and a 98% increase in product consistency, reaching the international leading level.

[0023] (2) This solution addresses the problem of large circumferential temperature difference in autoclave molding by proposing an in-situ conformal heating technology for the metal outer mold. The heating film (low pressure, high conversion rate) is evenly distributed on the surface of the metal outer mold to achieve uniform heating around the perimeter, thereby achieving green and low-cost manufacturing. To address the problem of temperature difference between the inner and outer layers of the complex structure and irregular inner cavity, an in-situ conformal heat-repairing adhesive film heat-repairing technology is proposed. A heat-repairing adhesive film (0.05mm-0.2mm) with the same resin as the carbon fiber composite material is applied to the surface of the carbon fiber prepreg. Electrodes are connected to the front and rear ends and energized to achieve a uniform temperature field with varying thickness. This forms a multi-size temperature gradient uniform molding technology, which solves the technical problem of coordinated control of the heat-repairing adhesive film and the heating film and the achievement of a uniform temperature field. It realizes the composite layup of the heat-repairing adhesive film and the carbon fiber prepreg, and the composite of the heating film and the metal outer mold. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the embedded structure of the heat-repairing adhesive film and the carbon fiber prepreg in this invention.

[0025] Figure 2 This is an embedded front view of the heat-repairing adhesive film and carbon fiber prepreg in this invention.

[0026] Figure 3 This is a schematic diagram of the connection structure between the metal and the metal outer mold in this invention.

[0027] The attached figures are labeled as follows: 1. Carbon fiber prepreg; 2. Heat-repairing adhesive film; 3. Heating film; 4. Metal outer mold; 5. Composite material cylindrical part; 6. Power supply; A. Current direction; B. Temperature transfer direction. Detailed Implementation

[0028] To more clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0029] See Figures 1-3 A method for in-situ conformal heating and homogenization forming of irregularly shaped internal cavity composite cylindrical parts, specifically including the following steps:

[0030] Step S1: Design and analyze the composite cylindrical component 5;

[0031] The specific analysis focuses on the product thickness. Heating will generate a temperature difference at the point where the thickness changes, similar to the temperature difference between the outer and inner surfaces of the product. By simulating the temperature difference at the point where the product's thickness changes, a heat-compensating film is added at the point of temperature difference to achieve temperature balance.

[0032] Step S2: Composite layup design of carbon fiber prepreg 1 and heat-repairing adhesive film 2;

[0033] Step S3: Preparation of heating film 3 and heat-replenishing adhesive film of homogeneous resin. The embedded film is heat-replenishing adhesive film 2 (lower temperature 10-50 degrees Celsius), and the composite with metal outer mold 4 is heating film 3 (higher temperature, main heating carrier).

[0034] Step S4: Composite laying of carbon fiber prepreg 1 and heat-repairing adhesive film 2, that is, adding heat-repairing adhesive film 2 at the designed thickness of carbon fiber prepreg 1.

[0035] Step S5: The heating film 3 is bonded to the metal outer mold 4;

[0036] Step S6: The components of the resin undergo a curing reaction;

[0037] Step S7: Demolding and machining.

[0038] It should be noted that the heating film 3 is made of graphene, and the metal outer mold 4 is actually a mold made of metal.

[0039] In step S2, Abaqus software is used to embed the operation mode of the heat-repairing adhesive film 2 to simulate and separate the temperature field of the material with varying thickness.

[0040] Based on the variable thickness structure, the heat-repairing adhesive film 2 is embedded in the carbon fiber prepreg 1, and the temperature field, modal, static stiffness and stability are simulated to determine and optimize the position of the heat-repairing adhesive film 2, so as to achieve uniform temperature distribution with variable thickness.

[0041] Regarding the specific simulation method, those skilled in the art can implement the specific operation through the Abaqus software, so it will not be described in detail here.

[0042] The carbon fiber prepreg 1 is 0.2mm thick. Layers are stacked together until the set thickness is reached. Then, a heat-repairing adhesive film is added, followed by another layer of carbon fiber prepreg 1. The metal outer mold 4 is then closed and cured. The outer surface of the metal outer mold 4 is the heating film 3, so the heating film 3 is not connected to the carbon fiber prepreg 1 or the heat-repairing adhesive film 2.

[0043] In step S3, according to the simulation design results, carbon fiber prepreg 1 is laid up according to the angle and number of layers, for example, by manual or electric iron heat-pressure coupling, and heat-reinforcing film 2 is applied to the surface of carbon fiber prepreg 1, similar to the heat-pressure coupling of an electric iron. The axial dimension of heat-reinforcing film 2 is larger than that of carbon fiber prepreg 1, with 10mm at each end, and then the carbon fiber prepreg 1 is laid up again.

[0044] After the composite layup is completed, the front and rear heat-repairing adhesive films 2 are connected to the electrodes and circuits.

[0045] The angles and number of layers of different composite cylindrical parts are different, which is common knowledge to those skilled in the art and will not be elaborated here.

[0046] In step S5, the pre-prepared uniform conformal heating film 3 is adhered to the surface of the metal outer mold 4 with an adhesive. The temperature uniformity inside the metal outer mold 4 is tested by powering on. The specific parameters are: voltage -5V DC, temperature difference ≤1℃, operating range room temperature -280℃, and temperature difference standard of uniform temperature field is ±2℃. Then, the composite material after composite layup is molded.

[0047] Mold assembly refers to combining the metal outer mold 4 with the composite cylindrical part 5. The product refers to the blank that has reached the required thickness after layup (including carbon fiber prepreg and heat-repairing film), namely the composite cylindrical part 5.

[0048] During the power-on test, specifically, the power supply 6 and the heating film 3 are connected in series using wires. The current direction A and the temperature transfer direction B are referenced in the appendix. Figure 3 As shown.

[0049] When vacuuming a vacuum bag, ensure that the wires and thermocouples pass through the sealing strip of the vacuum bag to prevent air leakage.

[0050] In step S6, under a uniform temperature field and normal pressure, the components of the thermosetting resin undergo a curing and cross-linking reaction. The curing and cross-linking reaction is the most basic reaction of thermosetting resins and is a technical term, so it will not be described in detail here.

[0051] Vacuuming involves placing the molded product into a vacuum bag, and the vacuum bag needs to be sealed with adhesive strips.

[0052] The technical features of this invention not described can be implemented by or using existing technology, and will not be repeated here. Of course, the above description is not a limitation of this invention, and this invention is not limited to the examples above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention should also be within the protection scope of this invention.

Claims

1. A method for in-situ conformal heating and homogenization forming of irregularly shaped internal cavity composite cylindrical parts, characterized in that, Specifically, the steps include the following: Step S1: Design and analyze composite cylindrical components; Step S2: Simulation design of composite layup of carbon fiber prepreg and heat-repairing adhesive film; In step S2, Abaqus software is used to embed the operation mode of the heating film to simulate and separate the temperature field of the material with varying thickness. Based on the variable thickness structure, the heat-repairing adhesive film is embedded in the carbon fiber prepreg, and the temperature field, modal, static stiffness and stability are simulated to determine and optimize the position of the heat-repairing adhesive film, so as to achieve uniform temperature distribution with variable thickness. Step S3: Preparation of heating film and heat-repairing adhesive film of homogeneous resin; Step S4: Laying out the carbon fiber prepreg and the heat-repairing adhesive film; Step S5: The heating film is bonded to the metal outer mold; Step S6: Curing reaction; Step S7: Demolding and machining.

2. The in-situ conformal heating and homogenization forming method for irregularly shaped internal cavity composite cylindrical parts according to claim 1, characterized in that, In step S4, based on the simulation design results, carbon fiber prepreg is laid up according to the angle and number of layers, and a heat-repairing adhesive film is applied to the surface of the carbon fiber prepreg. The axial dimension of the heat-repairing adhesive film is larger than that of the carbon fiber prepreg, and then the carbon fiber prepreg is laid up again. After the composite layup is completed, the front and rear heat-reinforcing adhesive films are connected to the electrodes and circuitry.

3. The in-situ conformal heating and homogenization forming method for irregularly shaped internal cavity composite cylindrical parts according to claim 1, characterized in that, In step S5, the pre-prepared uniform conformal heating film is adhered to the surface of the metal outer mold with an adhesive, the temperature uniformity inside the metal outer mold is tested by powering on, and then the composite material after composite layup is molded together.

4. The in-situ conformal heating and homogenization forming method for irregularly shaped internal cavity composite cylindrical parts according to claim 3, characterized in that, When vacuuming a vacuum bag, ensure that the wires and thermocouples pass through the sealing strip of the vacuum bag to prevent air leakage.

5. The in-situ conformal heating and homogenization forming method for irregularly shaped internal cavity composite cylindrical parts according to claim 1, characterized in that, In step S6, the components of the thermosetting resin undergo a curing and cross-linking reaction.

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