Hot-pressing system and hot-pressing method for composite material preform

Abstract

The invention discloses a hot-pressing system and a hot-pressing method for a composite material preform. The hot-pressing system comprises a product tool, a hot-pressed prepreg laying layer, a to-be-hot-pressed prepreg laying layer, a hot-pressing pressure pad, a temperature sensor, a sealed vacuumizing system and temperature control equipment, the pressure pad for hot pressing is of a layered structure and sequentially comprises a bottom rubber layer, a thin film electric heating layer, a composite material layer, a wrapping rubber layer and a heat insulation layer from inside to outside, and the hot pressing method comprises the steps of sensor arrangement, layer laying, pressure pad covering, packaging and vacuumizing, temperature control heating and completion of hot pressing according to temperature feedback and set time. The method does not need to depend on long-term occupation of an autoclave, reduces tool transfer, can perform hot pressing by paving only 1-5 layers of prepreg once, reduces the deformation risk of a workpiece, improves the heat efficiency through direct contact heat transfer, remarkably reduces the manufacturing cost and time, and is suitable for efficient forming of composite material preforms in the fields of aviation, spaceflight and traffic.

Description

Technical Field

[0001] This invention belongs to the field of composite material preparation technology, specifically relating to a hot pressing system and hot pressing method for composite material preforms. Background Technology

[0002] Resin-based carbon fiber composites possess superior properties such as high specific strength and specific stiffness, strong designability, good fatigue fracture resistance, corrosion resistance, and good dimensional stability. They are currently widely used high-performance structural materials in aerospace, transportation, and other fields.

[0003] Currently, the mainstream molding process for composite material products is autoclave curing. This process involves laying uncured prepreg on the mold surface, then vacuum sealing it before placing it in an autoclave for high-temperature, high-pressure curing. To reduce the internal porosity of the composite material and ensure product quality, a pre-compression operation is required during the prepreg laying process. This involves laying several layers of prepreg, sealing them, and then compacting the prepreg in advance using vacuum. However, for thick products, the interlayer pressure transmission in conventional pre-compression processes is insufficient, and the resin's physical properties at room temperature are close to solid, failing to effectively fill the pores. Consequently, the compaction effect of the pre-compression process for thick composite material products does not meet requirements.

[0004] To address this issue, existing technologies primarily employ a method of laying multiple layers, encapsulating them, and then hot-pressing them in an autoclave. After hot-pressing, further layering is performed. This overall hot-pressing process moderately heats the resin, improving its fluidity, promoting resin filling of pores, and enhancing the interlayer compaction effect of the prepreg. However, this technology has the following drawbacks: 1. The overall hot pressing requires tooling transfer and occupies the autoclave for a long time, resulting in low operating efficiency and high operating costs; 2. Due to the complicated and time-consuming hot pressing process, many layers are laid before hot pressing in actual applications, which leads to a large deformation of the part along the thickness direction during the hot pressing process. Composite material components with curvature are prone to bridging (female mold parts) or wrinkles (male mold parts). 3. The hot pressing process occupies the entire autoclave and uses hot air heating. The heat transfer efficiency is low and the process takes a long time. Therefore, we propose a hot pressing system and method for composite material preforms. Summary of the Invention

[0005] The purpose of this invention is to provide a hot pressing system and method for composite material preforms to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a hot pressing system for composite material preforms, comprising a pre-pressed prepreg layup, a prepreg layup to be hot-pressed, a pressure pad for hot pressing, a sealing vacuum system, a temperature sensor, a temperature control device, and product tooling; The pressure pad for hot pressing has a layered structure, comprising, from the inside out, a bottom rubber layer, a thin-film electric heating layer, a composite material layer, a wrapping rubber layer, and a heat insulation layer: The bottom rubber layer is used to directly contact the prepreg layer to be hot-pressed and to transmit uniform pressure. The thin-film electric heating layer is electrically connected to the temperature control device and is used to adjust the heating temperature and heating rate. The composite material layer is used to provide the overall rigidity of the pressure pad for hot pressing to ensure uniform pressure transmission; The rubber wrapping layer is wrapped around the outside of the composite material layer; The heat insulation layer is used to reduce heat loss; The temperature sensor is located in the edge margin area of ​​the pre-pressed prepreg layer, and the prepreg layer to be hot-pressed covers the temperature sensor; the sealing vacuum system is used to encapsulate and vacuum the entire assembly consisting of the pre-pressed prepreg layer, the prepreg layer to be hot-pressed, and the pressure pad for hot pressing. The temperature control device is used to receive the detection signal from the temperature sensor and regulate the working state of the thin-film electric heating layer.

[0007] Preferably, the shape of the pressure pad for hot pressing is adapted and adjusted according to the surface characteristics of the composite material preform, and the adapted surface includes L-shaped, annular and complex surfaces with curvature.

[0008] Preferably, the temperature sensor is a sheet-like temperature sensor and is connected to the temperature control device for signal transmission. The temperature control device is also used to display the detection temperature of the prepreg in real time.

[0009] Preferably, both the bottom rubber layer and the wrapping rubber layer are made of elastic rubber material.

[0010] Preferably, the composite material layer is made of a high-strength composite material, and its rigidity is adjusted according to the hot pressing pressure requirements.

[0011] Preferably, the heat insulation layer is made of high-temperature resistant heat insulation material and completely wraps around the outermost side of the pressure pad for hot pressing.

[0012] A hot pressing method for composite material preforms, based on a hot pressing system for composite material preforms, includes the following steps: S1: Place a temperature sensor in the edge margin area of ​​the hot-pressed prepreg layer; S2: Lay the prepreg layer to be hot-pressed along the surface of the prepreg layer, so that the prepreg layer to be hot-pressed completely covers the temperature sensor, until the preset number of layers are laid. S3: Cover the surface of the prepreg layer to be hot-pressed with a pressure pad for hot pressing; S4: The entire assembly consisting of the pre-pressed prepreg layer, the prepreg layer to be pressed, and the pressure pad for pressing is encapsulated by a sealed vacuum system and then vacuumed and pre-pressed. S5: Start the temperature control equipment, set the heating parameters, control the film electric heating layer to heat the prepreg layer to be hot-pressed, and start the hot-pressing operation; S6: The actual temperature of the prepreg is detected in real time by a temperature sensor. The hot pressing process is judged based on the actual temperature. When the hot pressing time reaches the specified value, the temperature control equipment is turned off, the heating is stopped, and the hot pressing is completed.

[0013] Preferably, in step S2, the number of layers of prepreg to be hot-pressed laid in a single step is 1-5.

[0014] Preferably, in step S5, the temperature control device sets a heating temperature of 40-80℃ and a heating rate of 1-10℃ / min based on the physicochemical properties of the prepreg.

[0015] Preferably, in step S6, the hot pressing time is specified as 10-60 minutes. When the temperature sensor detects that the actual temperature of the prepreg is stable within the set temperature range and the duration reaches the specified hot pressing time, the hot pressing is determined to be completed.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. Significantly improved ease of operation: The hot pressing operation is achieved by integrating a heating layer and pressure transmission function into the pressure pad for hot pressing, eliminating the need to rely on a hot press tank for overall hot pressing, saving tooling transfer links, simplifying the operation process and greatly improving hot pressing efficiency; 2. Significantly reduced costs and time: Reduces the time spent in autoclaves and the cost of tooling transfer, thereby reducing the manufacturing cost and time cost of parts, especially suitable for mass production scenarios; 3. Stable and reliable product quality: Supports hot pressing after laying 1-5 layers at a time, effectively reducing the deformation of the preform along the thickness direction during a single hot pressing. Combined with the conformal characteristics of the pressure pad used for hot pressing, it can reduce the risk of bridging or wrinkling of curved parts during hot pressing, ensuring the dimensional accuracy of the product and the quality of interlayer bonding. 4. Significantly improved heat transfer efficiency: The pressure pad used in hot pressing directly contacts the prepreg for heat transfer. Compared with the hot air medium heating in the autoclave, the heat transfer path is shorter, the heat loss is smaller, and the heating rate is faster, further improving the hot pressing efficiency. 5. High adaptability: The shape of the pressure pad for hot pressing can be adjusted according to the product surface, and it can be adapted to L-shaped, ring-shaped and complex surface parts with curvature. The heating temperature, heating rate and hot pressing time can be flexibly adjusted according to the physicochemical properties of the prepreg, and it can adapt to the hot pressing requirements of different types of composite material preforms. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the system structure of the present invention; Figure 2 This is a schematic diagram of the structure of the pressure pad for hot pressing according to the present invention.

[0018] In the diagram: 1. Prepreg layer that has been hot-pressed; 2. Prepreg layer to be hot-pressed; 3. Pressure pad for hot pressing; 310. Bottom rubber layer; 320. Thin film electric heating layer; 330. Composite material layer; 340. Wrapping rubber layer; 350. Thermal insulation layer; 4. Sealing vacuum system; 5. Temperature sensor; 6. Temperature control equipment; 7. Product tooling. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figures 1-2 The hot pressing system for composite material preforms provided by the present invention includes a pre-pressed prepreg layup 1, a prepreg layup to be hot-pressed 2, a pressure pad for hot pressing 3, a sealing vacuum system 4, a temperature sensor 5, a temperature control device 6, and a product tooling 7. The pressure pad 3 for hot pressing has a layered structure, which includes, from the inside out, a bottom rubber layer 310, a thin film electric heating layer 320, a composite material layer 330, a wrapping rubber layer 340, and a heat insulation layer 350. The bottom rubber layer 310 is made of elastic rubber material and has conformal bonding characteristics. It is used to directly contact the prepreg layer 2 to be hot-pressed and to transmit uniform pressure. The thin film electric heating layer 320 is electrically connected to the temperature control device 6 and is used to heat up the prepreg layer 2 to be heated. The heating temperature and heating rate can be adjusted by the temperature control device 6. The composite material layer 330 is made of high-strength composite material, and its rigidity can be adjusted according to the hot pressing pressure requirements. For example, rigidity can be adapted by selecting composite materials of different strength grades or adjusting the layer thickness, so as to provide rigidity for the entire pressure pad 3 for hot pressing to ensure uniform pressure transmission. The rubber wrapping layer 340 is made of elastic rubber material and has conformal properties. It is wrapped around the outside of the composite material layer 330 to help transmit pressure evenly. The heat insulation layer 350 is made of high-temperature resistant heat insulation material and is completely wrapped around the outermost side of the pressure pad 3 for hot pressing, in order to reduce heat loss and improve hot pressing efficiency. Temperature sensor 5 is a sheet-shaped temperature sensor, which is set in the edge margin area of ​​the prepreg layer 1 that has been hot-pressed, and the prepreg layer 2 to be hot-pressed covers the temperature sensor 5; temperature sensor 5 is connected to temperature control device 6, which is used to display the detected temperature of the prepreg in real time. The sealing vacuum system 4 is used to seal and vacuum the entire assembly consisting of the pre-pressed prepreg layer 1, the prepreg layer 2 to be pressed, and the pressure pad 3 for pressing; the temperature control device 6 is used to receive the detection signal from the temperature sensor 5 and regulate the working state of the thin film electric heating layer 320. The shape of the pressure pad 3 for hot pressing can be adapted and adjusted according to the surface characteristics of the composite material preform. The adaptable surfaces include L-shaped, annular and complex surfaces with curvature, in order to meet the hot pressing requirements of composite material preforms with different structures.

[0021] The hot pressing method for composite material preforms provided by this invention, based on the aforementioned hot pressing system, includes the following steps: S1: Place a sheet-shaped temperature sensor 5 in the edge margin area of ​​the prepreg layer 1 that has been hot-pressed, and ensure that the temperature sensor 5 is tightly attached to the hot-pressed prepreg layer 1. S2: Lay the prepreg layer 2 to be hot-pressed along the surface of the prepreg layer 1, so that the prepreg layer 2 to be hot-pressed completely covers the temperature sensor 5, until the specified number of layers are laid. Among them, the number of layers of prepreg to be hot-pressed in a single laying is 1-5 layers. This range of layers can effectively reduce the deformation amplitude of the preform along the thickness direction in a single hot pressing, and reduce the risk of bridging or wrinkling of curved parts. S3: Cover the surface of the prepreg layer 2 to be hot-pressed with the hot-pressing pressure pad 3, ensuring that the hot-pressing pressure pad 3 is completely attached to the prepreg layer 2 to be hot-pressed, and that the shape of the hot-pressing pressure pad 3 is adapted to the surface of the preform. S4: The entire assembly consisting of the ply (pre-pressed prepreg ply 1 + prepreg ply 2 to be pressed) and the pressure pad 3 for press is sealed by the sealing vacuum system 4 and vacuum pre-pressed to ensure that there are no obvious gaps between the ply layers. S5: Start the temperature control device 6, set the heating temperature to 40-80℃ and the heating rate to 1-10℃ / min according to the physical and chemical properties of the prepreg (such as resin type, curing requirements, etc.), control the film electric heating layer 320 to heat the prepreg layer 2 to be hot-pressed, and start the hot pressing operation. S6: The actual temperature of the prepreg is detected in real time by the temperature sensor 5, and the temperature control device 6 displays the detection data synchronously. The hot pressing process is judged based on the actual temperature. The specified hot pressing time is 10-60 minutes. When the temperature sensor 5 detects that the actual temperature of the prepreg is stable within the set temperature range and the duration reaches the specified hot pressing time, the hot pressing is determined to be completed, the temperature control device 6 is turned off, the heating is stopped, and the hot pressing process is completed. Repeating steps S1-S6 above can achieve multiple rounds of high-frequency hot pressing until the entire composite material preform is laid up and hot-pressed.

[0022] The present invention has the following beneficial effects: 1. Significantly improved ease of operation: The hot pressing operation is achieved by integrating a heating layer and pressure transmission function into the pressure pad for hot pressing, eliminating the need to rely on a hot press tank for overall hot pressing, saving tooling transfer links, simplifying the operation process and greatly improving hot pressing efficiency; 2. Significantly reduced costs and time: Reduces the time spent in autoclaves and the cost of tooling transfer, thereby reducing the manufacturing cost and time cost of parts, especially suitable for mass production scenarios; 3. Stable and reliable product quality: Supports hot pressing after laying 1-5 layers at a time, effectively reducing the deformation of the preform along the thickness direction during a single hot pressing. Combined with the conformal characteristics of the pressure pad used for hot pressing, it can reduce the risk of bridging or wrinkling of curved parts during hot pressing, ensuring the dimensional accuracy of the product and the quality of interlayer bonding. 4. Significantly improved heat transfer efficiency: The pressure pad used in hot pressing directly contacts the prepreg for heat transfer. Compared with the hot air medium heating in the autoclave, the heat transfer path is shorter, the heat loss is smaller, and the heating rate is faster, further improving the hot pressing efficiency. 5. High adaptability: The shape of the pressure pad for hot pressing can be adjusted according to the product surface, and it can be adapted to L-shaped, ring-shaped and complex surface parts with curvature. The heating temperature, heating rate and hot pressing time can be flexibly adjusted according to the physicochemical properties of the prepreg, and it can adapt to the hot pressing requirements of different types of composite material preforms.

[0023] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hot pressing system for a composite material preform, characterized in that, It comprises a hot-pressed prepreg layer (1), a to-be-hot-pressed prepreg layer (2), a hot-pressing pressure pad (3), a sealed vacuum system (4), a temperature sensor (5), a temperature control device (6) and a product tooling (7); The hot-pressing pressure pad (3) has a layered structure, comprising, from inside to outside, a bottom rubber layer (310), a film electric heating layer (320), a composite material layer (330), a wrapped rubber layer (340) and a heat insulation layer (350); The bottom rubber layer (310) is used for directly contacting the to-be-hot-pressed prepreg layer (2) and transmitting uniform pressure; The film electric heating layer (320) is electrically connected with the temperature control device (6) and is used for adjusting heating temperature and heating rate; The composite material layer (330) is used for providing overall rigidity of the hot-pressing pressure pad (3) to ensure uniform pressure transmission; The wrapped rubber layer (340) is wrapped outside the composite material layer (330); The heat insulation layer (350) is used for reducing heat loss; The temperature sensor (5) is arranged at an edge allowance area of the hot-pressed prepreg layer (1), and the to-be-hot-pressed prepreg layer (2) covers the temperature sensor (5); the sealed vacuum system (4) is used for packaging and vacuumizing the whole composed of the hot-pressed prepreg layer (1), the to-be-hot-pressed prepreg layer (2) and the hot-pressing pressure pad (3); The temperature control device (6) is used for receiving a detection signal of the temperature sensor (5) and controlling a working state of the film electric heating layer (320).

2. A hot pressing system for a composite material preform according to claim 1, characterized in that: The shape of the hot-pressing pressure pad (3) is adjusted according to the profile characteristics of the composite material preform, and the adaptive profile includes L-shaped, ring-shaped and complex profile with curvature.

3. A hot pressing system for a composite material preform according to claim 1, characterized in that: The temperature sensor (5) is a sheet-shaped temperature sensor and is signal-connected with the temperature control device (6), and the temperature control device (6) is also used for displaying the detection temperature of the prepreg in real time.

4. A hot pressing system for a composite material preform according to claim 1, characterized in that: The bottom rubber layer (310) and the wrapped rubber layer (340) are both made of elastic rubber material.

5. A hot pressing system for a composite material preform according to claim 1, characterized in that: The material of the composite material layer (330) is high-strength composite material, and the rigidity thereof is adjusted according to the hot-pressing pressure demand.

6. A hot pressing system for a composite material preform according to claim 1, characterized in that: The heat insulation layer (350) is made of high-temperature-resistant heat insulation material and completely wraps the outermost side of the hot-pressing pressure pad (3).

7. A method for hot pressing a composite preform, implemented on the basis of the hot pressing system for a composite preform according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1: placing a temperature sensor (5) at an edge allowance area of a hot-pressed prepreg layer (1); S2: laying a to-be-hot-pressed prepreg layer (2) along the surface of the hot-pressed prepreg layer (1) so that the to-be-hot-pressed prepreg layer (2) completely covers the temperature sensor (5) until the laying of a preset number of layers is completed; S3: covering a hot-pressing pressure pad (3) on the surface of the to-be-hot-pressed prepreg layer (2); S4: packaging and vacuumizing the whole composed of the hot-pressed prepreg layer (1), the to-be-hot-pressed prepreg layer (2) and the hot-pressing pressure pad (3) through a sealed vacuum system (4); S5: starting a temperature control device (6), setting heating parameters, controlling a film electric heating layer (320) to heat the to-be-hot-pressed prepreg layer (2) and starting hot-pressing operation; S6: Real-time detection of the actual temperature of the prepreg by the temperature sensor (5), judgment of the hot pressing process according to the actual temperature, when the hot pressing time reaches the specified value, the temperature control device (6) is closed, the heating is stopped, and the hot pressing is completed.

8. The method of claim 7, wherein the method further comprises: In step S2, the number of layers of the single-laid hot-pressing prepreg is 1-5 layers.

9. The method of claim 7, wherein the method further comprises: In step S5, the temperature control device (6) sets the heating temperature of 40-80℃ and the temperature rising rate of 1-10℃ / min according to the physicochemical properties of the prepreg.

10. The method of claim 7, wherein the method further comprises: In step S6, the specified hot pressing time is 10-60min, and when the temperature sensor detects that the actual temperature of the prepreg is stable in the set temperature range and the duration reaches the specified hot pressing time, it is determined that the hot pressing is completed.

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