Thermoplastic composite strain energy rod forming method and apparatus

Abstract

The application belongs to the technical field of aerospace composite material manufacturing, and particularly relates to a thermoplastic composite material strain energy rod forming method and equipment. First, a prepreg layer is formed into a preform, and then the preform is pressed by a flat plate pre-pressing equipment to form a preform sheet intermediate body. Then, the preform sheet intermediate body is sent into a hot-pressing module with an intermediate hot and two-end cold gradient temperature field, and finally shaping is completed through high-temperature zone melting forming and low-temperature zone controllable cooling. Finally, the shaped rod piece is cooled and shaped, and then is pulled out at a uniform speed by a traction device and is coiled and collected by a winding device, so that continuous production is realized. The hot-pressing module of the matched hot-pressing equipment is provided with a partition heating and integrated cooling system, so that a gradient temperature field can be accurately constructed and the cooling rate can be controlled. The application accurately controls the material crystallization behavior and releases internal stress by means of the gradient temperature control, so that the straightness, size stability and unfolding performance consistency of the strain energy rod are effectively ensured, and the manufacturing requirements of the strain energy rod for large deployable structures of a spacecraft are perfectly adapted.

Description

Technical Field

[0001] This invention belongs to the field of aerospace composite material manufacturing technology, specifically, it relates to a method and equipment for forming thermoplastic composite strain energy rods. Background Technology

[0002] Composite strain energy rods are core components of large deployable space structures such as satellite antennas and solar sails, relying on the strain energy stored during retraction to achieve autonomous deployment. These rods are characterized by their ultra-long length (up to tens of meters), ultra-thinness (wall thickness often less than 0.5 mm), and the need for extremely high shape accuracy and dimensional stability.

[0003] Currently, thermosetting composite materials (such as epoxy resin) are commonly used to prepare strain energy bars in this field. To address the need for ultra-long component fabrication, CN202110810510.5 proposes a continuous bonding method for ultra-long composite strain energy bars. This method uses flat-pressure bonding instead of in-situ bonding, integrating processes such as flattening, grinding, cleaning, applying adhesive, pressure bonding, and cutting to achieve continuous fabrication of thermosetting strain energy bars, thus solving the problems of bonding positioning errors and dimensional limitations to some extent. However, this process relies entirely on adhesive films / adhesives for flap connection, making it only suitable for thermosetting composite materials and unsuitable for the molding characteristics of thermoplastic materials.

[0004] However, thermosetting materials have inherent limitations such as relatively insufficient resistance to space environment (e.g., resistance to radiation and antigenic oxygen erosion), non-recyclability, and long processing cycles. For example, CN202410003767.3 proposes an on-orbit forming method for rods based on induction heating and magnetohydrodynamic cooling, which achieves efficient heating in a vacuum environment through an embedded metal layer to complete the forming of composite material tubes; CN202411105620.1 proposes an on-orbit cold bending manufacturing process for aluminum truss rods for space use, realizing the miniaturized on-orbit cold bending forming of aluminum truss rods. The above technologies either rely on induction heating of the metal layer, which cannot be adapted to pure thermoplastic composite materials; or they use metal materials, which have problems such as large weight, non-insulation, and high thermal conductivity, making it difficult to meet the requirements of lightweighting, insulation, and adaptability to the space environment of spacecraft, and none of them have the core advantages of thermoplastic materials, such as recyclability and melt-remodeling.

[0005] More importantly, existing continuous molding equipment and processes are designed for thermosetting resins, employing isothermal or programmed temperature curing modes. They lack the ability to construct gradient temperature fields and controllable cooling, failing to meet the process requirements of high-performance thermoplastic resins such as PPS and PEEK, which require melt molding above 350°C and slow, controllable cooling crystallization. The melt viscosity of thermoplastic resins is much higher than that of thermosetting resins, and traditional equipment easily leads to defects such as high internal stress, poor straightness, surface step marks, and poor consistency in unfolding performance. Furthermore, the non-adhesive and melt-welding characteristics of thermoplastic materials render existing adhesive bonding processes completely ineffective. There are currently no dedicated molding methods or equipment to achieve continuous, stable, and high-quality molding of thermoplastic composite strain gauges, severely restricting their engineering application in space-deployable structures.

[0006] However, applying thermoplastic composites to the manufacture of strain energy bars faces significant challenges: 1. Thermosetting strain gauges are not recyclable or can not be reprocessed in orbit, thus failing to meet the requirements for in-orbit reuse.

[0007] 2. On-orbit forming technology is difficult to adapt to pure thermoplastic materials, while metal rods have performance shortcomings.

[0008] 3. Traditional molding equipment lacks dedicated gradient temperature control capabilities for thermoplastic materials, resulting in compromised molding quality and efficiency.

[0009] Therefore, there is an urgent need for a rapid continuous molding method and equipment for strain energy bars specifically designed for high-performance thermoplastic composite materials, in order to solve the synergistic challenges of material compatibility, molding quality, production efficiency, and on-orbit reuse. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and apparatus for forming thermoplastic composite strain energy bars.

[0011] A method for forming a thermoplastic composite strain energy bar according to the present invention includes the following steps: Step S1: Lay up the prepreg to form a preform, wherein the prepreg is a carbon fiber fabric reinforced PPS or PEEK thermoplastic prepreg. Step S2: Press the preform using a double steel belt press or a continuous hot press to form a preformed sheet intermediate. Step S3: The preformed sheet intermediate is fed into the hot pressing molding module of the continuous molding equipment. The hot pressing molding module is provided with a temperature gradient field along the material's forward direction, consisting of a high-temperature zone in the middle and low-temperature zones at both ends. The temperature gradient field includes a high-temperature zone for melting and molding the material and a low-temperature zone for controlling the cooling of the molded component. The low-temperature zone achieves controllable cooling of the rod by adjusting the temperature and flow rate of the cooling medium. The cooling rate of the rod is controlled at 0.5-5°C / min to regulate the crystallinity of the resin and release internal stress. Step S4: After the formed strain energy bar is cooled and shaped, it is continuously pulled out and wound up by the traction device.

[0012] Furthermore, in step S1, the preform is formed by automatically laying prepreg according to a preset layup sequence and angle.

[0013] Furthermore, in step S2, the flat pre-pressing equipment is a double steel belt press or a continuous hot press, and the pressing process parameters are: temperature 300-400°C, pressure 0.3-3MPa, time 5-40min. Pressing allows the resin matrix to fully melt and initially impregnate the fibers, forming a dense sheet-like pre-fabricated intermediate.

[0014] Furthermore, in step S2, the pressing process parameters for preparing the preformed sheet intermediate are: temperature 320-380°C, pressure 0.5-1.5MPa, and time 15-30min.

[0015] Furthermore, in step S3, the temperature gradient field is a gradient structure with a hot center and cold ends, including a central high-temperature zone and low-temperature zones located on both sides of the central high-temperature zone. The total hot-pressing time of the pre-formed sheet intermediate in the hot-pressing molding module is 3-5 minutes.

[0016] Furthermore, the temperature of the high-temperature zone is higher than the melting point of the thermoplastic resin matrix, and the pressing pressure of the high-temperature zone is 2-8 MPa. The pre-formed sheet intermediate softens rapidly in the high-temperature zone and is bonded together under pressure to form the cross-sectional shape of the final rod. When the prepreg is PEEK thermoplastic prepreg, the high-temperature zone temperature is 380-410°C; when the prepreg is PPS thermoplastic prepreg, the high-temperature zone temperature is 310-330°C.

[0017] Furthermore, the temperature of the low-temperature zone is lower than the resin melting point and higher than the resin glass transition temperature; When the prepreg is PEEK thermoplastic prepreg, the low-temperature zone temperature is 150-280°C; when the prepreg is PPS thermoplastic prepreg, the low-temperature zone temperature is 90-200°C.

[0018] Furthermore, in step S4, the traction device pulls out the strain energy rod at a constant speed, and the winding device coils and collects the pulled-out strain energy rod, thereby realizing the continuous production of the strain energy rod.

[0019] The present invention also provides an apparatus for the aforementioned thermoplastic composite strain energy bar forming method, comprising an unwinding device, a preheating device, a hot pressing forming module, a cooling and shaping module, a traction device, and a winding device arranged in sequence; The hot pressing molding module is equipped with a zoned heating system and an integrated cooling system to form a temperature gradient field with the middle hot and the two ends cold along the material's direction of movement, thereby completing the melting and molding and controlled cooling of the pre-formed sheet intermediate.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses thermoplastic composite materials such as PPS and PEEK to replace traditional thermosetting materials, enabling strain energy rods to be recyclable, melt-reformable, and capable of on-orbit secondary processing, meeting the needs of on-orbit manufacturing, on-orbit repair, and reuse of spacecraft, while also exhibiting better adaptability to the space environment, such as resistance to radiation and antigenic oxygen erosion.

[0021] 2. The innovative gradient temperature control hot pressing module of this invention, through the temperature field design of "hot in the middle and cold at both ends" and combined with controllable cooling technology of 0.5-5°C / minute, not only effectively reduces the internal stress of the product, but also actively and precisely controls the crystallization behavior of thermoplastic resin, ensuring that ultra-long and ultra-thin rods have excellent straightness, dimensional stability and consistent unfolding performance.

[0022] 3. This invention addresses the melting and crystallization process characteristics of thermoplastic resins by specifically designing the hot pressing module of a continuous molding equipment. By combining a zoned heating system and an integrated cooling system to form a gradient temperature field, it solves the compatibility problem of thermoplastic materials in traditional thermosetting composite material molding equipment, providing reliable equipment support for the engineering production of thermoplastic composite strain gauges. Attached Figure Description

[0023] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a flow chart of the molding process of the present invention. Detailed Implementation

[0024] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0025] Example 1 This embodiment discloses a method for forming a thermoplastic composite strain energy bar, including the following steps.

[0026] Step S1, Prefabricated body layup: The prepreg made of 5H satin carbon fiber fabric and PEEK film is automatically laid up in a symmetrical layup sequence of [±45°]2s to form the component prefabricated body.

[0027] Step S2, Pre-formed sheet intermediate: The preform is fed into a double steel belt press and pressed for 25 minutes at a temperature of 380°C and a pressure of 1MPa to obtain a pre-formed sheet intermediate with a smooth surface and good resin impregnation.

[0028] Step S3, Final Forming of Strain Energy Rod: The preformed sheet intermediate is fed into a gradient temperature-controlled continuous hot press equipment. After being preheated by a preheating device, it enters the hot press forming module. The temperature of the high-temperature zone in the center of the hot press forming module is set to 385°C and the pressure to 5MPa. Cooling water at 40°C is introduced into the low-temperature zones at both ends to control the temperature of the low-temperature zones at 200°C. The preformed sheet intermediate passes through the hot press forming module at a speed of 0.1m / min. The hot press time is 4min and the cooling rate is approximately 2°C / min.

[0029] Step S4, Traction and Winding: After the formed strain energy rod is cooled by the cooling and shaping module, it is continuously pulled out by the traction mechanism and then coiled and collected by the winding device.

[0030] The resulting carbon fiber fabric / PEEK strain energy bar is 10.5m long, with a straightness error of less than 1 / 1000, a deployment torque of 5.5 N·m, and a fluctuation range of less than ±3%. After 100 cycles of high and low temperature cycling from -100°C to +100°C, the performance degradation is less than 2%, and there is no permanent deformation, meeting the requirements for use in spacecraft deployable structures.

[0031] Compared with the traditional isothermal hot pressing process, other process conditions and raw materials are kept completely consistent with those in Example 1. The only difference is that the hot pressing molding module of the gradient temperature control continuous hot pressing equipment is set to isothermal 395°C, and rapid water cooling is used at the equipment outlet.

[0032] The resulting rods exhibited significant bending and surface step marks; the unfolding torque fluctuated by more than ±10%, resulting in poor consistency; after undergoing the same high and low temperature cycling test, the rods showed permanent deformation and could not meet the usage requirements.

[0033] Example 2 This embodiment also discloses a molding device for the method of Embodiment 1, including an unwinding device, a preheating device, a hot pressing molding module, a cooling and shaping module, a traction device, and a winding device arranged sequentially along the material advance direction of the production line. The hot pressing molding module is provided with a corresponding partitioned heating system and an integrated cooling system.

[0034] The zoned heating system uses heating rods with independent temperature control as heating elements. In this embodiment, resistance heaters are preferred. Along the longitudinal direction of the material's movement, the heating area of ​​the hot pressing molding module is divided into a central high-temperature zone and two low-temperature zones on both sides. The heating rods in each zone are independently controlled, thereby establishing a gradient temperature field with a high temperature in the middle and low temperatures at both ends inside the hot pressing molding module, which meets the temperature requirements for thermoplastic resin melting and initial cooling.

[0035] The integrated cooling system is a cooling pipeline set in the low-temperature zone of the hot pressing molding module. In this embodiment, the cooling pipeline is preferably a coil structure. A cooling medium is introduced into the cooling pipeline. In this embodiment, the cooling medium is preferably water with a temperature of 20-80°C. By adjusting the temperature and flow rate of the cooling medium, the temperature of the low-temperature zone and the cooling rate of the part are precisely controlled, thereby achieving precise control of the resin crystallization behavior.

[0036] The unwinding device is used to unwind the pre-formed sheet intermediate, the preheating device preheats the intermediate to ensure that the material temperature is uniform when entering the hot pressing module, the cooling and shaping module performs secondary cooling on the rod after hot pressing to further stabilize the size and shape, the traction device provides constant traction force to ensure that the material moves forward at a uniform speed, and the winding device realizes the coiling and collection of the strain energy rod after forming.

[0037] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0038] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for forming a thermoplastic composite strain energy bar, characterized in that, Includes the following steps: Step S1: Lay up the prepreg to form a preform, wherein the prepreg is a carbon fiber fabric reinforced PPS or PEEK thermoplastic prepreg. Step S2: Press the preform using a double steel belt press or a continuous hot press to form a preformed sheet intermediate. Step S3: The preformed sheet intermediate is fed into the hot pressing molding module of the continuous molding equipment. The hot pressing molding module is provided with a temperature gradient field along the material's forward direction, consisting of a high-temperature zone in the middle and low-temperature zones at both ends. The temperature gradient field includes a high-temperature zone for melting and molding the material and a low-temperature zone for controlling the cooling of the molded component. The low-temperature zone achieves controllable cooling of the rod by adjusting the temperature and flow rate of the cooling medium. The cooling rate of the rod is controlled at 0.5-5°C / min to regulate the crystallinity of the resin and release internal stress. Step S4: After the formed strain energy bar is cooled and shaped, it is continuously pulled out and wound up by the traction device.

2. The method for forming a thermoplastic composite strain energy bar according to claim 1, characterized in that, In step S1, the preform is formed by automatically laying prepreg according to a preset layup sequence and angle.

3. The method for forming a thermoplastic composite strain energy bar according to claim 1, characterized in that, In step S2, the pressing process parameters are: temperature 300-400°C, pressure 0.3-3MPa, and time 5-40min. Pressing allows the resin matrix to fully melt and initially impregnate the fibers, forming a dense sheet-like pre-fabricated intermediate.

4. The method for forming a thermoplastic composite strain energy bar according to claim 3, characterized in that, The pressing process parameters for preparing the preformed sheet intermediate are: temperature 320-380°C, pressure 0.5-1.5MPa, and time 15-30min.

5. The method for forming a thermoplastic composite strain energy bar according to claim 1, characterized in that, The temperature gradient field is a gradient structure with a hot center and cold ends, including a central high-temperature zone and low-temperature zones located on both sides of the central high-temperature zone. The total hot-pressing time of the pre-formed sheet intermediate in the hot-pressing molding module is 3-5 minutes.

6. The method for forming a thermoplastic composite strain energy bar according to claim 1, characterized in that, The temperature in the high-temperature zone is higher than the melting point of the thermoplastic resin matrix, and the pressing pressure in the high-temperature zone is 2-8 MPa. The pre-formed sheet intermediate softens rapidly in the high-temperature zone and is bonded together under pressure to form the cross-sectional shape of the final rod. When the prepreg is PEEK thermoplastic prepreg, the high-temperature zone temperature is 380-410°C; when the prepreg is PPS thermoplastic prepreg, the high-temperature zone temperature is 310-330°C.

7. The method for forming a thermoplastic composite strain energy bar according to claim 1, characterized in that, The temperature in the low-temperature zone is below the resin melting point and above the resin's glass transition temperature. When the prepreg is PEEK thermoplastic prepreg, the low-temperature zone temperature is 150-280°C; when the prepreg is PPS thermoplastic prepreg, the low-temperature zone temperature is 90-200°C.

8. The method for forming a thermoplastic composite strain energy bar according to claim 1, characterized in that, The traction device pulls out the strain energy rod at a constant speed, and the winding device coils and collects the pulled-out strain energy rod, realizing the continuous production of strain energy rods.

9. A thermoplastic composite strain energy bar molding device, characterized in that, The thermoplastic composite strain energy bar is produced using any one of claims 1 to 8.

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