A method of post-processing a thermoplastic composite

Abstract

The present application relates to the technical field of thermoplastic composite material processing, in particular to a post-processing method of thermoplastic composite material. The method comprises the following steps: double-sided heating of a thermoplastic composite material test plate, so that the upper and lower sides of the test plate are heated simultaneously and the temperature is raised to a temperature matching the melting temperature of the resin in the test plate; continuously conveying the heated test plate; during the continuous conveying of the test plate, the test plate sequentially passes through at least two roller pressing zones with gradually decreasing temperatures along the conveying direction, and the test plate is rolled and simultaneously cooled in each roller pressing zone, so that the test plate experiences a temperature path with gradually decreasing temperatures along the conveying direction until it is cooled to a predetermined temperature. The method can shorten the post-processing cycle, improve the dimensional accuracy and performance stability of the product, and is suitable for various thermoplastic resin systems, having good process adaptability and industrial application value.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic composite material processing technology, and in particular to a post-processing method for thermoplastic composite materials. Background Technology

[0002] Thermoplastic composites are widely used in aerospace, high-end equipment manufacturing, and the automotive industry due to their advantages such as short molding cycles, high recyclability, and excellent mechanical properties. However, thermoplastic resins typically have high melt viscosity and narrow processing temperature windows, which can easily lead to problems such as internal stress accumulation, warping deformation, and high porosity during the composite molding process. These issues can affect the dimensional accuracy and mechanical property stability of the parts, thus requiring post-processing to optimize the performance of the molded specimens.

[0003] Currently, post-processing techniques for thermoplastic composites mainly include oven heat treatment and infrared heat treatment. Oven heat treatment typically relies on hot air circulation for heating, with heat primarily transferred through air convection. This results in significant temperature differences between the surface and core layers, and between the edges and center of the test specimen, leading to inconsistent resin crystallization rates and uneven internal stress distribution, which can easily cause significant warping deformation. Furthermore, the oven heating rate is relatively low, and the preheating and holding processes are time-consuming, resulting in an overall processing cycle that typically lasts several hours, leading to low production efficiency and difficulty in meeting the needs of large-scale production. In addition, this method offers limited improvement in specimen densification, fails to effectively reduce porosity, and provides only a small improvement in mechanical properties.

[0004] In comparison, infrared heat treatment has a higher heating rate, but existing infrared heating methods mostly use a single-sided heating structure, resulting in a large temperature difference between the upper and lower surfaces of the test plate, making it difficult to achieve uniform heating. For thicker composite materials, heat is difficult to transfer effectively to the core layer, leading to insufficient release of internal stress and even delamination. At the same time, excessive resin melting and loss can easily occur in local areas, causing fiber exposure and reducing local mechanical properties.

[0005] In addition, some existing technologies have attempted to use microwave heating, chemical modification or autoclaves for post-processing. However, microwave heating is prone to generating local hot spots, which can lead to resin degradation or even scrapping of test plates. Chemical modification has limited improvement on mechanical properties and may introduce residues that affect material properties. Autoclave equipment is expensive and has a long processing cycle. Furthermore, the dimensional accuracy of the parts may be reduced during the secondary pressurization process, which limits the overall industrial application.

[0006] In summary, existing post-processing technologies generally suffer from difficulties in balancing heating efficiency and heating uniformity, failing to effectively balance the relationship between interfacial pore filling and resin flow control. They also exhibit poor adaptability to the high-temperature sensitivity and interlayer structural characteristics of thermoplastic composites, easily leading to limited improvement in material properties or even the introduction of new defects. Therefore, there is an urgent need to provide a post-processing method for thermoplastic composites that can achieve rapid and uniform heating while simultaneously ensuring densification and dimensional stability. Summary of the Invention

[0007] This invention covers the following technical solutions:

[0008] This invention relates to a post-processing method for thermoplastic composite materials, characterized by comprising the following steps:

[0009] The thermoplastic composite material test plate is heated on both sides, so that the upper and lower sides of the test plate are heated simultaneously and the temperature is raised to a temperature that matches the melting temperature of the resin in the test plate.

[0010] The heated test plates are continuously conveyed.

[0011] During the continuous transport of the test plate, the test plate passes through at least two rolling zones with progressively decreasing temperatures along the transport direction. The test plate is rolled and cooled simultaneously in each rolling zone, so that the test plate experiences a progressively decreasing temperature path along the transport direction until it is cooled to the predetermined temperature.

[0012] This invention utilizes the synergistic effect of double-sided heating and gradient slow-cooling roller pressing to achieve uniform heating and controlled cooling of thermoplastic composite material test panels within a short time. This helps reduce the temperature difference between the surface and core layers of the test panel, decreases internal stress accumulation, and suppresses warping deformation. Simultaneously, roller pressing promotes pore compaction, thereby reducing porosity and improving interlayer bonding strength and overall mechanical properties. This method shortens the post-processing cycle, improves the dimensional accuracy and performance stability of the parts, and is applicable to various thermoplastic resin systems, demonstrating good process adaptability and industrial application value. Attached Figure Description

[0013] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0014] Figure 1 : A schematic diagram of the arrangement of infrared heating lamps in one embodiment of the present invention.

[0015] Figure 2: This is a side view of a thermoplastic composite material post-processing device according to an embodiment of the present invention.

[0016] Figure 3 : Front view of a thermoplastic composite material post-processing device according to an embodiment of the present invention.

[0017] Reference numerals: 101-Infrared thermometer, 102-High thermal conductivity equalizing pressure component, 103-Locking device, 104-Thermoplastic composite material test plate, 105-Lifting device, 106-Sliding table, 107-Screw lifting device, 108-Infrared heating module, 109-Servo motor, 110-Linear module, 111-Constant temperature electric heating roller, 112-Pneumatic lifting device, 113-Tooling platform. Detailed Implementation

[0018] Reference will now be made to detailed embodiments of the present invention, one or more of which are described below. Each example is provided for explanation and not for limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0019] Unless otherwise stated, all terms used to disclose this invention (including technical and scientific terms) should be understood to have the meaning commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of protection of this invention. Unless the context clearly defines otherwise, the scientific and technical terms used herein, as well as terms and laboratory procedures in related fields such as composite materials engineering, materials thermal processing and heat transfer, and heating and roll forming in mechanical engineering, are all conventional terms and standard methods well-known and widely used in the art. To facilitate understanding of the technical solutions of this invention, some related terms are further defined and explained below.

[0020] The terms “containing,” “comprising,” and “including” as used in this invention are synonyms and are inclusive or open-ended, and do not exclude additional, uncited members, elements, or method steps.

[0021] In this invention, the numerical range represented by endpoints includes all numerical values ​​and fractions contained within that range, as well as the endpoints mentioned.

[0022] Furthermore, in describing representative embodiments of the invention, this specification may present the methods and / or processes of the invention as a specific sequence of steps. However, the method or process should not be limited to the specific order of the steps described herein, to the extent that the method or process does not depend on the specific order of the steps presented herein. As will be understood by those skilled in the art, other sequences of steps are also possible. Therefore, the specific order of steps presented in the specification should not be construed as a limitation of the claims. Additionally, the claims relating to the methods and / or processes of the invention should not be limited to the execution of their steps in the order they are written, and those skilled in the art will readily recognize that the sequence can be changed while still remaining within the spirit and scope of the invention.

[0023] As used in this invention, unless otherwise stated, the singular forms of the articles “a,” “an,” and “the” include plural referents.

[0024] In this invention, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2.

[0025] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0026] In this invention, terms such as "preferred," "better," "more suitable," and "ideal" merely describe implementation methods or embodiments with better effects and should be understood not to limit the scope of protection of this invention. In this invention, terms such as "optionally," "optionally," and "optional" mean that something is optional, that is, selected from either "with" or "without" a parallel solution. If multiple "optional" statements appear in a technical solution, unless otherwise specified and without contradiction or mutual constraint, each "optional" statement is independent.

[0027] In this invention, the term "thermoplastic composite material" refers to a composite material system consisting of a thermoplastic resin as the matrix and fiber-reinforced materials as the reinforcing phase.

[0028] In this invention, the term "test plate" refers to a thermoplastic composite material part to be post-processed. It can be a sheet structure or a layered or plate-like structure with a certain thickness direction, including sheets, laminates or other parts that can be heated and rolled.

[0029] In this invention, the term "double-sided heating" refers to heating the test plate simultaneously from both the top and bottom sides, so that the test plate achieves a more uniform temperature distribution in the thickness direction, thereby reducing the temperature difference between the surface layer and the core layer and improving the distribution of thermal stress.

[0030] In this invention, the term "rolling zone" refers to a region consisting of one or more rolling units capable of applying pressure to the test plate and simultaneously exchanging heat, in which the test plate is subjected to rolling action and undergoes temperature changes during transport.

[0031] In this invention, the term "gradient cooling" refers to the process where the test plate passes through multiple roller pressing zones with different temperatures in sequence during the conveying process, causing its temperature to decrease gradually along the conveying direction, thereby achieving a controlled cooling process.

[0032] In this invention, the term "pressure equalization component" refers to a component disposed on the surface of a test plate for conducting heat and uniformly distributing pressure during the heating process. It is usually made of a high thermal conductivity material to improve the heating uniformity of the test plate and suppress deformation during the heating process.

[0033] In this invention, the "isothermal crystallization zone" refers to a temperature-maintaining area set in the gradient slow cooling roller pressing path. Within this zone, the test plate is maintained within the crystallization temperature range of the corresponding thermoplastic resin during continuous conveying or staged dwell, and is subjected to roller pressing under these temperature conditions.

[0034] In this invention, "crystallization peak temperature Tc" refers to the peak temperature of the exothermic peak of crystallization during the crystallization process of thermoplastic resin. It can be determined by differential scanning calorimetry or by other thermal analysis methods recognized in the art.

[0035] This invention relates to a post-processing method for thermoplastic composite materials, which includes the following steps:

[0036] The thermoplastic composite material test plate is heated on both sides, so that the upper and lower sides of the test plate are heated simultaneously and the temperature is raised to a temperature that matches the melting temperature of the resin in the test plate.

[0037] The heated test plates are continuously conveyed.

[0038] During the continuous transport of the test plate, the test plate passes through at least two rolling zones with progressively decreasing temperatures along the transport direction. The test plate is rolled and cooled simultaneously in each rolling zone, so that the test plate experiences a progressively decreasing temperature path along the transport direction until it is cooled to the predetermined temperature.

[0039] The coordinated action of the above steps helps to reduce the temperature difference between the surface and core layers of the test plate, reduce the accumulation of internal stress and suppress warping deformation. At the same time, the rolling action promotes interlayer bonding and pore compaction, thereby improving the dimensional stability and mechanical properties of thermoplastic composite parts. The post-processing process is completed in a shorter time to meet the needs of continuous and large-scale production.

[0040] The technical solution of this invention is not a simple parallel application of existing heating or rolling methods, but rather an integrated design of the entire process of "heating-conveying-rolling-cooling" in the post-processing of thermoplastic composite materials, focusing on the rheological behavior and cooling and solidification characteristics of the material in the molten state. By closely linking double-sided heating with subsequent gradient slow cooling rolling, the test plate directly enters the multi-stage rolling zone while maintaining a state close to the melting temperature, thereby completing heating, densification, and controlled cooling in the same continuous process, changing the process path of separate processing steps in the prior art. Furthermore, this invention introduces a temperature distribution that gradually decreases along the conveying direction during the rolling stage, and makes each rolling zone perform different heat treatment functions while applying pressure, so that the test plate sequentially experiences resin flow, pore compaction, and gradual solidification in different temperature ranges. This coupling mechanism of "temperature gradient-rolling action" matches the pressure action with the material state, thereby avoiding the internal stress concentration and structural defects caused by traditional single temperature or rapid cooling conditions, and achieving a synergistic improvement in densification and dimensional stability.

[0041] Furthermore, this invention, through the combination of double-sided heating and a high thermal conductivity pressure-equalizing component, enables the test plate to achieve a relatively uniform temperature distribution before entering the rolling zone, and completes the transition from the heating stage to the rolling cooling stage within a short path, thereby significantly reducing the temperature difference between the surface layer and the core layer. Combined with a gradient slow-cooling rolling process, the generation and release path of thermal stress can be effectively controlled while ensuring processing efficiency. Therefore, this invention can significantly shorten the post-processing cycle while simultaneously improving multiple properties such as temperature uniformity, low warpage deformation, and high density, demonstrating a comprehensive technical effect different from existing technologies.

[0042] "A temperature matching the melting temperature of the resin in the test plate" is a functional temperature limit, which is not strictly equal to the melting temperature (Tm), but refers to the temperature range that allows the resin to reach a flowable processing state. Specifically, this statement should be understood as: the temperature is set to allow the thermoplastic resin to be in a molten or near-molten state, thereby possessing a certain fluidity, so as to achieve, for example, pore compaction, interface rearrangement, and internal stress release during subsequent rolling processes. This temperature can be equal to the melting temperature of the resin, or slightly higher or slightly lower, as long as the above-mentioned process objectives are achieved, which is easily understood by those skilled in the art.

[0043] In a preferred embodiment of the present invention, the relative positional relationship between the rolling zone and the double-sided heating zone is optimized so that the test plate after double-sided heating can enter the rolling zone within a shorter transport path. This facilitates the subsequent rolling and cooling processes while the test plate is still at a relatively high temperature. Specifically, the present invention preferably proceeds to the rolling gradient cooling step immediately after heating.

[0044] Specifically, the distance between the rolling zone and the double-sided heating zone can be adjusted according to factors such as the resin type, thickness, and conveying speed of the test plate to meet the needs of equipment layout and process integration in practical applications. In some embodiments, the distance between the rolling zone and the double-sided heating zone is no more than 50 mm. This setting helps reduce temperature loss between the end of heating and the start of rolling, ensuring the test plate remains close to its melting temperature when entering the rolling zone. This improves the rolling densification effect and reduces the risk of internal stress caused by sudden temperature drops, thereby contributing to improved dimensional stability and mechanical properties of the parts.

[0045] In some implementations, during the continuous transport of the test plates, the test plates are sequentially transported along the transport direction through three, four, five, six or more rolling zones with progressively decreasing temperatures.

[0046] In some implementations, each rolling zone is formed by multiple sets of thermostatically heated rollers arranged sequentially along the transport direction.

[0047] The constant-temperature electric heating rollers are arranged in series along the test plate transport path so that the test plate can pass through multiple rolling units sequentially during continuous transport. Each constant-temperature electric heating roller can be configured to have a heating function and maintain a set temperature, thereby achieving heat exchange while applying rolling pressure to the test plate.

[0048] In some specific implementations, the temperature of the first rolling zone is typically set slightly below the resin's melting temperature (approximately 70% to 90% of the melting temperature, corresponding to approximately Tm−40°C to Tm−80°C) to ensure the resin remains in a flowable or semi-molten state, thus facilitating pore compaction and interface rearrangement. Subsequently, the temperature of each rolling zone gradually decreases along the transport direction, with the initial cooling amplitude being relatively large (typically 40–80°C) to achieve rapid detachment from the melting zone and control resin flow. The subsequent cooling amplitude gradually decreases (typically 20–50°C), allowing the material to complete curing and internal stress release under a gentler temperature gradient, avoiding new thermal stress concentration. Comparing different material systems, high-melting-point resins (such as PEEK) generally have an upward-shifted gradient range and more stages (e.g., a 4-stage gradient), while low-melting-point resins (such as PP) generally have a lower temperature range and fewer stages (e.g., a 3-stage gradient). However, both follow the basic pattern of "initial high temperature maintaining fluidity—rapid cooling in the middle stage—slow cooling in the final stage." The gradient slow cooling roller pressing temperature setting of the present invention has good scalability. Its core lies in constructing a staged cooling path around the resin melting temperature to complete the flow densification, structural stabilization and stress release processes in different temperature zones.

[0049] In some embodiments, a lifting device is provided below each of the thermostatic heating rollers to drive the rollers to lift and press down, adapting to thermoplastic composite material test plates of different thicknesses. This structural arrangement facilitates the formation of a continuous and stable rolling path as the test plate moves along the transport direction, allowing the test plate to undergo continuous compaction while being cooled step by step. This promotes interlayer bonding and reduces porosity, thereby improving the overall mechanical properties and structural density of the part.

[0050] In a preferred embodiment of the present invention, each rolling zone is equipped with a temperature control unit, allowing the temperature of each rolling zone to be independently adjustable. The temperature control unit can set the temperature of each rolling zone according to the type of resin, melting temperature, and cooling characteristics of the thermoplastic composite material, thereby forming a predetermined temperature distribution as the test plate passes through each rolling zone sequentially along the transport direction. Independent temperature control of each rolling zone allows the test plate to experience a gradually decreasing temperature path during rolling, enabling it to complete resin flow, pore compaction, and gradual curing at different temperature stages. This avoids stress concentration caused by sudden temperature changes and helps improve the dimensional stability and mechanical properties of the test plate. Furthermore, this independent temperature control method can be flexibly adjusted according to different material systems and part thicknesses, thereby improving the applicability and process stability of the method of the present invention.

[0051] In a preferred embodiment of the present invention, during the process of the test plate passing through the at least two stages of rolling zones with progressively decreasing temperatures along the conveying direction, an isothermal crystallization zone is set up so that the test plate is kept within the crystallization temperature range of the corresponding thermoplastic resin for a predetermined time, thereby promoting the formation of the thermoplastic resin crystal structure and reducing the residual stress inside the test plate.

[0052] The isothermal crystallization zone does not require the test plate temperature to be absolutely constant throughout the entire holding process. Rather, it means that the temperature fluctuation in this zone is controlled within a range that does not affect the purpose of resin crystallization regulation. For example, the temperature fluctuation can be controlled within ±2℃, ±5℃, ±10℃, or ±15℃ of the set temperature.

[0053] In some embodiments, the temperature of the isothermal crystallization zone can be set within the crystallization temperature range of the corresponding thermoplastic resin, so that the resin molecular chains can undergo orderly rearrangement under suitable crystallization temperature conditions, thereby facilitating the formation of a more uniform and stable crystalline structure. The crystallization temperature range can be determined based on the type of thermoplastic resin, crystallization peak temperature, melting temperature, glass transition temperature, part thickness, fiber content, and target performance. In some embodiments, the temperature of the isothermal crystallization zone can be within the range of the thermoplastic resin's crystallization peak temperature Tc ± 30℃, Tc ± 20℃, or Tc ± 10℃. The crystallization peak temperature Tc refers to the peak temperature of the exothermic peak during the crystallization process of the thermoplastic resin, which can be determined by differential scanning calorimetry or other thermal analysis methods recognized in the art. By setting the temperature of the isothermal crystallization zone near the crystallization peak temperature, it is beneficial to avoid insufficient crystallization or uneven crystallinity distribution caused by simple rapid cooling, while also reducing the increase in processing cycle or local performance degradation that may result from prolonged high-temperature maintenance.

[0054] In some embodiments, the isothermal holding time in the isothermal crystallization zone can be 3–90 seconds, for example, 5–60 seconds, 8–45 seconds, 10–30 seconds, or 15–25 seconds. The isothermal holding time can be achieved by increasing the number of constant-temperature heating rollers forming the isothermal crystallization zone, extending the length of the isothermal crystallization zone along the conveying direction, reducing the linear module's moving speed, intermittently stopping the test plate within the isothermal crystallization zone, or a combination of the above methods. If the holding time is too short, the resin molecular chains may not have fully rearranged, resulting in insufficient crystallization; if the holding time is too long, it may increase the processing cycle and, for some resin systems, may cause excessive crystallization or a decrease in toughness. Therefore, those skilled in the art can select an appropriate holding time within the above range based on the resin type, part thickness, and target performance.

[0055] In some specific embodiments, for PEEK resin systems, the temperature of the isothermal crystallization zone can be set to 220–280°C, 230–270°C, 240–260°C, or approximately 250°C, and the isothermal holding time can be 10–40 seconds, 10–30 seconds, 15–25 seconds, or approximately 20 seconds. For PP resin systems, the temperature of the isothermal crystallization zone can be set to 80–120°C, 90–110°C, or approximately 100°C, and the isothermal holding time can be 5–30 seconds, 5–20 seconds, or approximately 10 seconds. For PA resin systems, the temperature of the isothermal crystallization zone can be determined according to the specific type of polyamide and its crystallization peak temperature; for example, it can be set within the range of the corresponding crystallization peak temperature Tc ± 30°C and held for 5–60 seconds. By setting different isothermal crystallization temperatures and holding times for different thermoplastic resin systems, the method of the present invention can be adapted to the crystallization kinetics of different resins, thereby improving process stability and consistency of part performance.

[0056] In some embodiments, the test plate undergoes a first cooling stage before entering the isothermal crystallization zone and a second cooling stage after passing through the isothermal crystallization zone. The cooling rate of the first cooling stage is greater than that of the second cooling stage. The first cooling stage refers to the cooling process where the test plate moves from a near-molten or semi-molten state into a temperature range suitable for subsequent crystallization control. This facilitates the rapid removal of the resin from its excessive flow dynamics, thereby reducing excessive resin loss, interlayer slippage, or fiber wrinkling. The second cooling stage refers to the stage where the test plate continues to cool to a lower temperature after passing through the isothermal crystallization zone. This facilitates further cooling and shaping, and release of residual thermal stress, based on the resin having already formed a certain crystalline structure. The greater cooling rate of the first cooling stage allows the test plate to enter the suitable temperature range for crystallization control more quickly, followed by a more gradual temperature change to complete the subsequent structural stabilization process.

[0057] In some embodiments, the cooling rate of the first cooling stage is 10℃ / min to 20℃ / min (e.g., 12℃ / min, 14℃ / min, 16℃ / min, 18℃ / min), and the cooling rate of the second cooling stage is 5℃ / min to 10℃ / min (e.g., 6℃ / min, 8℃ / min, 10℃ / min). The cooling rate can be calculated based on the temperature difference between adjacent temperature stages and the time required for the test plate to traverse the corresponding cooling path. Specifically, it can be calculated using the formula V=(T1-T2) / t, where V represents the cooling rate, T1 represents the temperature of the previous temperature stage, T2 represents the temperature of the next temperature stage, and t represents the time taken for the test plate to move from the previous temperature stage to the next temperature stage. The time t can be calculated based on the distance between adjacent rolling zones and the test plate conveying speed, or it can be obtained through actual measurement using a temperature detection device. For a cooling path formed by multiple sets of constant-temperature electric heating rollers, the cooling rate can be calculated based on the temperature difference between two adjacent constant-temperature electric heating rollers and the time it takes for the test plate to pass through the corresponding section, or it can be calculated by averaging the total temperature difference and total passage time of multiple continuous rolling zones.

[0058] In some embodiments, each rolling zone forms a pressure path matching the temperature path along the test plate transport direction, so that different rolling pressures are applied to the pre-rolling zone near the double-sided heating zone, the isothermal crystallization zone, and the subsequent slow cooling and shaping zone; wherein, the rolling pressure of the pre-rolling zone near the double-sided heating zone is 100N to 200N, the rolling pressure of the isothermal crystallization zone is 200N to 300N, and the rolling pressure of the subsequent slow cooling and shaping zone is 300N to 500N.

[0059] In a specific implementation of the PEEK resin system, the test plate can be a CF / PEEK composite material test plate with a thickness of 1–5 mm, 1.5–3 mm, or approximately 2 mm. The carbon fiber volume fraction can be 50–70%, 55–68%, or approximately 64%, and the resin content can be 30–45%, 32–40%, or approximately 36%. The double-sided heating temperature can be 320–380°C, 330–370°C, 340–360°C, or approximately 350°C, and the heating time can be 3–10 seconds, 4–8 seconds, or approximately 5 seconds. After double-sided heating, the test plate can be sequentially passed through isothermal heating rollers at temperatures of 340°C, 280°C, 250°C, 150°C, and 50°C. The isothermal heating roller at 250°C forms an isothermal crystallization zone, which is maintained for approximately 20 seconds. As an alternative, the temperature path of the PEEK system can also be set as a staged temperature path of 330~350℃, 270~290℃, 240~260℃, 140~170℃ and 40~70℃, so as to achieve a gradual transition from the near-molten state, the crystallization-controlled state to the low-temperature stable state under different working conditions.

[0060] In the aforementioned PEEK resin system, the pre-rolling zone near the double-sided heating area can include two sets of constant-temperature electric heating rolling zones at 340℃ and 280℃, with rolling pressures of 100–200 N; the isothermal crystallization zone can be a constant-temperature electric heating rolling zone at 250℃, with rolling pressures of 200–300 N; the subsequent slow cooling and shaping zone can include constant-temperature electric heating rolling zones at 150℃ and 50℃, with rolling pressures of 300–500 N. The pre-rolling zone can be used to maintain chain segment flow and interface rearrangement when the resin is in a molten or semi-molten state; the isothermal crystallization zone can be used to promote the formation of a stable crystalline structure near the crystallization peak temperature; and the subsequent slow cooling and shaping zone can be used to further shape the formed crystalline structure under higher pressure. Through the synergistic matching of the above temperature path, pressure path, and crystallization process, it is beneficial to improve the crystallization uniformity, dimensional stability, and interlayer bonding performance of the CF / PEEK composite material, and further reduce warpage and internal defects.

[0061] In some embodiments, the isothermal crystallization zone is not limited to a single temperature point and can also form a narrow temperature plateau. For example, when the thermoplastic resin is PEEK, the isothermal crystallization zone can be set to a temperature plateau of 240–260°C; when the thermoplastic resin is PP, the isothermal crystallization zone can be set to a temperature plateau of 90–110°C. The temperature plateau can be formed by multiple sets of thermostatic heating rollers with the same set temperature, or by multiple sets of thermostatic heating rollers with small temperature differences, as long as the test plate is within a suitable temperature range for resin crystallization in this region and can be maintained for a sufficient time for crystallization regulation. Through the above settings, the present invention can introduce a regulation stage for resin crystallization behavior without significantly changing the continuous processing method, thereby balancing processing efficiency and part performance.

[0062] In a preferred embodiment of the present invention, the double-sided heating is achieved by infrared heating modules arranged symmetrically on the top and bottom.

[0063] Heating from both sides simultaneously helps to reduce the temperature difference between the surface and core layers of the test plate, thereby reducing the problem of excessive temperature gradient caused by heating from one side, improving the distribution of internal stress and suppressing warping deformation of the test plate during the heating process.

[0064] In terms of specific structure, each group of infrared heating modules preferably includes multiple infrared heating lamps arranged in a uniformly staggered manner. This staggered arrangement helps avoid spatial concentration or gaps in infrared radiation, allowing for a more uniform distribution of radiant energy across the test plate surface, thereby improving overall heating uniformity. In a preferred embodiment, each group of infrared heating modules includes 6 to 8 infrared heating lamps; however, the invention is not limited to this specific number and can be adjusted according to the test plate size and heating requirements.

[0065] Furthermore, the upper and lower sets of infrared heating modules are mounted in an inverted C-shape on the screw lifting device. This allows the infrared heating modules to form a relatively enclosed heating space around the test plate, thereby reducing heat loss and improving heating efficiency.

[0066] Furthermore, the screw lifting device is used to adjust the distance between the upper and lower sets of infrared heating modules. This device allows for adjustment of the distance between the two sets of infrared heating modules to accommodate thermoplastic composite parts of different thicknesses or structural forms, ensuring that infrared radiation maintains a suitable effective distance under various operating conditions. This structure not only improves heating efficiency and uniformity but also enhances the versatility and adjustment flexibility of the equipment to meet the post-processing requirements of different material systems.

[0067] In a preferred embodiment of the present invention, the double-sided heating employs mid-wave infrared heating. This allows the thermoplastic composite material test plate to achieve rapid heating and good heating uniformity in a short time. Mid-wave infrared radiation can generate good energy coupling with various thermoplastic resins, which is beneficial to improving radiation absorption efficiency, thereby enabling the test plate to quickly reach a temperature state matching the resin melting temperature during double-sided heating.

[0068] Furthermore, in a preferred embodiment, the wavelength of the mid-wave infrared radiation is 2–5 μm. This wavelength range balances heating efficiency and penetration depth, allowing infrared radiation to act not only on the surface of the test plate but also to a certain extent to the internal regions. This helps reduce the temperature gradient along the thickness direction of the test plate and improves overall heating uniformity. Through the above settings, the test plate can achieve a more uniform temperature distribution before subsequent rolling and cooling processes, providing favorable initial conditions for the subsequent gradient slow cooling rolling process.

[0069] In a preferred embodiment of the present invention, the double-sided heating is completed in a short time to ensure that the test plate reaches a temperature matching the resin melting temperature while reducing resin degradation or performance deterioration that may be caused by prolonged heating. In a preferred embodiment, the double-sided heating time is 3 to 8 seconds. For materials with lower melting temperatures or better thermal conductivity, the heating time can be relatively shorter, while for test plates with higher melting temperatures or greater thickness, the heating time can be appropriately extended. Reasonable control of the heating time helps to avoid localized overheating or uneven temperature distribution of the test plate while ensuring heating efficiency, thereby providing stable initial temperature conditions for subsequent rolling and gradient cooling processes, and contributing to improved overall process stability and repeatability.

[0070] In a preferred embodiment of the present invention, the test plate is fitted with a high thermal conductivity equalizing pressure component during double-sided heating to improve heating uniformity and suppress deformation of the test plate during heating. The equalizing pressure component is disposed on the upper and lower sides of the test plate and is tightly fitted to the surface of the test plate, allowing infrared radiation to be rapidly conducted and redistributed through the equalizing pressure component while acting on the test plate. This improves heating uniformity in all areas of the test plate and reduces the temperature difference between the surface and core layers. Simultaneously, the equalizing pressure component provides support to the test plate during heating, which helps to suppress warping or deformation of the test plate at high temperatures, thereby improving the dimensional stability of the part.

[0071] In a preferred embodiment, the pressure equalizing member is made of graphite copper composite material.

[0072] Graphite-copper composite materials possess high thermal conductivity, good dimensional stability, and sufficient structural strength. While ensuring effective infrared radiation on the test plate, they facilitate rapid and uniform heat distribution on the test plate surface and maintain the plate's flatness before rolling. Exemplary graphite-copper composite materials can have a thickness of 0.8–1.2 mm, a thermal conductivity of not less than 350 W / (m·K), preferably 370–380 W / (m·K), a surface flatness of not more than 0.02 mm, and a hardness of not less than HRC45. By employing the aforementioned pressure-equalizing component, heating uniformity and forming quality can be improved without significantly increasing structural complexity, thereby further enhancing the overall performance of thermoplastic composite parts.

[0073] In a preferred embodiment of the present invention, the pressure equalizing component is mounted on a lifting device, and the lifting device is mounted on a sliding table of a transmission structure.

[0074] With the above structural design, the pressure equalizing component can be adjusted up and down with the lifting device to adapt to thermoplastic composite material parts of different thicknesses or structural forms, and maintain a close fit with the surface of the test plate during heating and transportation.

[0075] Furthermore, the lifting device, in conjunction with the transmission structure, enables the pressure equalizing component and the test plate to be smoothly and continuously conveyed between the double-sided heating area and the rolling area, maintaining a stable posture and positional relationship during the conveying process. By installing the pressure equalizing component on the lifting device and linking it with the sliding table, reliable clamping and support are achieved during the heating stage, and appropriate height adjustment is possible before entering the rolling area, thus providing a good structural foundation for the subsequent rolling process. This structure not only improves the stability and adaptability of equipment operation but also reduces the need for manual adjustments, thereby improving the overall process continuity and automation level.

[0076] In a preferred embodiment of the present invention, the thermoplastic resin in the thermoplastic composite material is selected from one or more of polyetheretherketone (PEEK), polypropylene (PP), polyamide (PA), and polycarbonate (PC). These resin materials have different melting temperature ranges and rheological properties. By adjusting the double-sided heating temperature and the temperature distribution of each rolling zone, the method of the present invention can be adapted to the post-processing requirements of different types of thermoplastic composite materials, thereby achieving performance optimization while ensuring processing stability.

[0077] The above method facilitates the synergistic effect of uniform heating and controlled cooling in different resin systems, thereby reducing internal stress, suppressing warpage, and improving pore structure, ultimately enhancing the dimensional accuracy and mechanical property stability of the parts. Based on its excellent temperature control capabilities and continuous processing characteristics, this method is particularly suitable for the post-processing of composite material parts with high requirements for dimensional accuracy, heating uniformity, and processing continuity, such as thermoplastic composite components in aerospace, high-end equipment manufacturing, and automotive manufacturing, demonstrating promising engineering application prospects and significant potential for widespread adoption.

[0078] The embodiments of the present invention will be described in detail below with reference to the examples. It should be understood that these embodiments are only used to illustrate the technical content of the present invention and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the specific experimental conditions in the following embodiments are given priority reference to the guidelines provided in this specification, or may be carried out according to generally accepted experimental manuals or conventional experimental conditions, or other experimental methods known in the art, or according to the conditions recommended by the relevant reagent or instrument manufacturers. In specific embodiments, unless otherwise specified, minor deviations within the weighing accuracy range are allowed for the measurement parameters involving raw material components; reasonable deviations due to instrument detection accuracy or operational accuracy are also allowed for parameters such as temperature and time.

[0079] Example 1

[0080] This embodiment provides a post-processing device for thermoplastic composite materials, and processing steps based thereon.

[0081] 1. Post-processing equipment

[0082] Combination Figures 1-3 It includes a double-sided heating area, a transmission area and a gradient cooling roller pressing area along the processing direction, which are used to perform double-sided heating, continuous conveying and gradient cooling roller pressing on thermoplastic composite material test plates. Figure 2 and Figure 3 In the diagram, 101 is an infrared thermometer, 102 is a high thermal conductivity equalizing pressure component, 103 is a locking device, 104 is a thermoplastic composite material test plate, 105 is a lifting device, 106 is a sliding table, 107 is a screw lifting device, 108 is an infrared heating module, 109 is a servo motor, 110 is a linear module, 111 is a constant temperature electric heating roller, 112 is a pneumatic lifting device, and 113 is a tooling platform. It should be noted that the high thermal conductivity equalizing pressure component 102 shown in the diagram is preferably designed as a sheet material to fit snugly against the surface of the thermoplastic composite material test plate 104, thereby simultaneously performing the functions of heat conduction, uniform distribution, and support shaping during the heating process.

[0083] like Figure 2 and Figure 3As shown, the double-sided heating area consists of two sets of infrared heating modules 108 arranged symmetrically. The upper infrared heating module 108 is positioned above the thermoplastic composite material test plate 104, with the heating surface facing downwards; the lower infrared heating module 108 (wavelength 2μm~5μm mid-wave infrared) is positioned below the thermoplastic composite material test plate 104, with the heating surface facing upwards, so as to achieve simultaneous heating of both sides of the thermoplastic composite material test plate 104. Figure 1 It is understood that each infrared heating module 108 contains multiple infrared heating lamps, which are preferably arranged in a uniformly staggered manner to facilitate a more balanced distribution of radiant energy in both the width and transmission directions of the test plate. In a preferred embodiment, each infrared heating module 108 includes 6 to 8 infrared heating lamps. The upper and lower infrared heating modules 108 are preferably mounted in an inverted C-shape on a screw lifting device 107. The screw lifting device 107 can adjust the distance between the upper and lower infrared heating modules 108 (preferably within a range of 10 mm to 500 mm) to accommodate thermoplastic composite material parts of different thicknesses (e.g., 1 mm to 10 mm) or structural forms, and to maintain a suitable working distance between the infrared heating modules 108 and the thermoplastic composite material test plate 104. An infrared thermometer 101 is located on the side of the infrared heating module 108 to detect the temperature status on both sides of the thermoplastic composite material test plate 104, facilitating monitoring and adjustment of the heating process.

[0084] The thermoplastic composite material test plate 104 is disposed between two upper and lower high thermal conductivity equalizing pressure members 102 and fixed by a locking device 103. The high thermal conductivity equalizing pressure members 102 are preferably sheet-shaped, and their planar contours can be adapted to the areas to be treated on the thermoplastic composite material test plate 104 to facilitate a tight fit with the test plate surface. Through this arrangement, on the one hand, the high thermal conductivity equalizing pressure members 102 can rapidly conduct and redistribute the heat provided by the infrared heating module 108, which is beneficial to improving the heating uniformity of each area of ​​the thermoplastic composite material test plate 104 and reducing the temperature difference between the surface layer and the core layer; on the other hand, the high thermal conductivity equalizing pressure members 102 can also provide stable support for the thermoplastic composite material test plate 104 during the heating process, thereby reducing the possibility of warping and local deformation of the thermoplastic composite material test plate 104 at high temperatures. In a preferred embodiment, the high thermal conductivity equalizing pressure component 102 is made of graphite copper composite material with a thickness of 0.8–1.2 mm, a thermal conductivity of not less than 350 W / (m·K), preferably 370–380 W / (m·K), a surface flatness of not more than 0.02 mm, and a hardness of not less than HRC45, possessing high thermal conductivity, thinness, and high strength. The high thermal conductivity equalizing pressure component 102 is directly attached to the surface of the thermoplastic composite material test plate 104, serving as a support carrier for the thermoplastic composite material test plate 104. It does not obstruct the penetration of infrared rays and can quickly conduct heat to ensure uniform heating of the thermoplastic composite material test plate 104, while suppressing warping deformation of the test plate under hot conditions. The upper and lower high thermal conductivity equalizing pressure components 102 are equipped with locking devices for pressing the thermoplastic composite material test plate. The distance between the high thermal conductivity equalizing pressure component 102 and the infrared heating module 108 is 5-8mm. The distance can be adjusted according to different material properties. Infrared radiation can act on the high thermal conductivity equalizing pressure component 102 and be transferred to the test plate 104 through its thermal conduction. The high thermal conductivity equalizing pressure component 102 can evenly transfer heat to each area of ​​the test plate, avoid local overheating, and adapt to the temperature window requirements of different resins.

[0085] The high thermal conductivity equalizing pressure component 102 is mounted on the lifting device 105, which is further mounted on the sliding table 106. The sliding table 106 is connected to the linear module 110 and driven by the servo motor 109, thereby continuously conveying the thermoplastic composite material test plate 104 and the high thermal conductivity equalizing pressure component 102 attached to it between the double-sided heating area and the gradient slow cooling rolling area. The lifting device 105 is preferably an L-shaped structure. The above-mentioned transmission structure facilitates the timely entry of the thermoplastic composite material test plate 104 into the subsequent rolling cooling stage after the double-sided heating is completed, thereby reducing unnecessary heat loss and achieving smooth movement of the test plate between the double-sided heating area and the gradient slow cooling rolling area, improving the continuity and stability of the process connection.

[0086] The gradient slow-cooling rolling pressing area is located downstream of the double-sided heating area, adjacent to it, with a spacing of ≤50mm. It mainly consists of multiple sets of constant-temperature electric heating rollers 111 arranged sequentially along the conveying direction of the thermoplastic composite material test plate 104. Each constant-temperature electric heating roller 111 is preferably connected to an independent temperature control unit, so that different temperatures can be set for the constant-temperature electric heating rollers 111 at different positions according to the type of resin in the thermoplastic composite material and its melting temperature and cooling characteristics, allowing the thermoplastic composite material test plate 104 to experience a gradually decreasing temperature path along the conveying direction during transport. A pneumatic lifting device 112 is preferably installed below each constant-temperature electric heating roller 111 to drive the constant-temperature electric heating roller 111 to lift and press down, adapting to thermoplastic composite material test plates 104 of different thicknesses and providing stable contact during rolling. A tooling platform 113 is located below the constant-temperature electric heating roller 111 for installing and supporting the constant-temperature electric heating roller 111 and its related components. Therefore, after the thermoplastic composite material test plate 104 is heated on both sides, it can continuously enter the rolling zone formed by multiple sets of constant temperature electric heating rollers 111 under the drive of the linear module 110 and the sliding table 106. While being cooled down step by step, it is subjected to rolling treatment, thereby promoting pore compaction, interlayer bonding and structural densification.

[0087] In this embodiment, the above-mentioned equipment achieves double-sided heating of the thermoplastic composite material test plate 104 through infrared heating modules 108 arranged symmetrically on both sides. A high thermal conductivity pressure equalizing component 102 improves heating uniformity and suppresses thermal deformation. A servo motor 109, a linear module 110, a sliding table 106, and a lifting device 105 achieve continuous conveying and position adjustment of the thermoplastic composite material test plate 104. Gradient slow cooling and rolling processing is achieved through multiple sets of constant-temperature electric heating rollers 111 and their corresponding temperature control and lifting structures. The synergistic cooperation of these structures facilitates the completion of the heating, conveying, rolling, and cooling processes within a shorter process path, thereby improving the dimensional accuracy, heating uniformity, structural density, and mechanical property stability of the thermoplastic composite material parts.

[0088] 2. Post-processing steps

[0089] (1) Pretreatment: Clean the surface of the thermoplastic composite material test plate (such as CF / PEEK, GF / PP, CF / PA, etc.) to remove oil, dust and impurities. After checking that the test plate is undamaged, tightly attach it to the upper and lower high thermal conductivity equalizing pressure components and fix it with the edge locking device to ensure that there is no gap between the test plate and the high thermal conductivity equalizing pressure components, thereby improving the thermal conductivity efficiency. Fix the high thermal conductivity equalizing pressure components and the test plate on the lifting device and lift it to the middle of the two sets of infrared heating modules.

[0090] (2) Parameter adaptation and heating preparation: Set the adaptation parameters according to the resin type and thickness (1mm~10mm) of the test plate:

[0091] Infrared heating temperature: Match the resin melting temperature (e.g., PEEK: 320-380℃; PP: 160-180℃; PA: 220-260℃; PC: 260-290℃).

[0092] Heating lamp spacing: Adjust the spacing between the upper and lower sets of infrared heating modules to keep the distance between the infrared heating module and the high thermal conductivity equalizing pressure component 5-8mm;

[0093] Infrared heating power: 8-12kW (adapted according to the thickness of the test plate and the thermal conductivity of the resin).

[0094] (3) Double-sided infrared heating: Start the linear module and feed the test plate with the high thermal conductivity equalizing pressure component into the double-sided infrared heating module at a uniform speed. The heating time is 3-8 seconds (adjusted according to the resin type: 3-5 seconds for low melting point resin and 5-8 seconds for high melting point resin). The infrared rays penetrate the high thermal conductivity equalizing pressure component to directly heat the test plate. At the same time, the high thermal conductivity equalizing pressure component quickly conducts heat. With the double-sided symmetrical heating, the temperature difference between the surface layer and the core layer of the test plate is ≤5℃. Moreover, the supporting effect of the high thermal conductivity equalizing pressure component helps to suppress the thermal deformation of the test plate.

[0095] (4) Gradient slow cooling roll forming: After heating, the test plate enters the gradient slow cooling roll forming area within 1-3 seconds (before significant cooling) along with the high thermal conductivity equalizing pressure component. It passes through multiple sets of gradient slow constant temperature electric heating rollers adapted to the resin type in sequence. The roll forming temperature is set according to the resin type, and the temperature is reduced according to the set temperature gradient. Finally, it is naturally cooled to room temperature. After the high thermal conductivity equalizing pressure component is removed, the post-processing is completed.

[0096] Example 2: CF / PEEK composite material (high melting point type)

[0097] (1) Specifications of the test plate to be treated: thickness 2mm, resin content 36%;

[0098] (2) Pretreatment: Wipe the surface of the test plate with anhydrous ethanol, and fix it tightly with the upper and lower high thermal conductivity graphite copper high thermal conductivity pressure equalizing components (thickness 1.0mm, thermal conductivity 380W / (m·K)) through edge locking devices (such as buckles and nuts). The flatness error of the test plate is ≤0.03mm.

[0099] (3) Parameter adaptation: Set the infrared heating temperature to 350℃, the distance between the upper and lower heating lamps to 12mm (the distance between the heating lamp and the high thermal conductivity equalizing pressure component to 4mm), and the heating power to 10kW;

[0100] (4) Double-sided infrared heating: linear module speed 1m / min, heating time 5 seconds, actual test results showed a temperature difference of 2.8℃ between the surface and core layers of the test board;

[0101] (5) Gradient slow cooling roll forming: The rolls are passed through constant temperature electric heating rollers at 280℃→200℃→100℃→50℃ in sequence. The rolling speed is synchronized with the linear module (1m / min). After cooling to room temperature, the high thermal conductivity equalizing pressure component is disassembled.

[0102] (6) Post-processed part properties: crystallinity 26.3%, warpage 0.65mm, porosity 0.9%, short beam shear strength 85MPa, 0° tensile strength 1852MPa, elastic modulus 131GPa.

[0103] Unless otherwise specified, the crystallinity testing method used in this invention is as follows: Non-isothermal melt crystallization studies are conducted using a DSC instrument under a nitrogen protective atmosphere at a gas flow rate of 50 ml / min. The mass of the resin sample being tested is controlled between 3 and 5 mg. First, the temperature is increased from 30°C to 400°C at a heating rate of 10°C / min and held for 5 min to eliminate thermal history. Then, the temperature is decreased to 50°C at a cooling rate of 10°C / min. Finally, the temperature is increased to 400°C at a heating rate of 10°C / min to complete the test.

[0104] Example 3: GF / PP composite material (low melting point type)

[0105] (1) Specifications of the test plate to be treated: thickness 5mm, glass fiber volume fraction 25%;

[0106] (2) Pretreatment: Mechanically clean the surface of the test plate and tightly fix it with the upper and lower high thermal conductivity graphite copper high thermal conductivity equalizing pressure components (thickness 1.0mm, thermal conductivity 380W / (m·K)). The flatness error of the test plate is ≤0.04mm.

[0107] (3) Parameter adaptation: Set the infrared heating temperature to 170℃, the distance between the upper and lower heating lamps to 19mm (the distance between the heating lamp and the high thermal conductivity equalizing pressure component is 6mm), and the heating power to 8kW;

[0108] (4) Double-sided infrared heating: linear module speed 1.2m / min, heating time 4 seconds, actual test results showed that the temperature difference between the surface layer and the core layer of the board was 3.2℃;

[0109] (5) Gradient slow cooling roll forming: The rolls are passed through constant temperature electric heating rollers at 140℃→100℃→50℃ in sequence. The rolling speed is synchronized with the linear module (1.2m / min). After cooling to room temperature, the high thermal conductivity equalizing pressure component is disassembled.

[0110] (6) Post-treatment properties of the part: warpage 0.54 mm / m, porosity 0.8%, interlaminar shear strength 0.9 N / mm 2 Tensile strength 185MPa, elastic modulus 25.6GPa.

[0111] Example 4: CF / PA composite material (medium melting point type)

[0112] (1) Specifications of the test plate to be treated: 6mm thickness, 28% carbon fiber volume fraction;

[0113] (2) Pretreatment: Wipe the surface of the test plate with anhydrous ethanol, and fix it tightly with the upper and lower high thermal conductivity graphite copper high thermal conductivity equal pressure components (thickness 1mm, thermal conductivity 370W / (m·K)). The flatness error of the test plate is ≤0.03mm.

[0114] (3) Parameter adaptation: Set the infrared heating temperature to 240℃, the distance between the upper and lower heating lamps to 20mm (the distance between the heating lamp and the high thermal conductivity equalizing pressure component to 6mm), and the heating power to 9kW;

[0115] (4) Double-sided infrared heating: linear module speed 1m / min, heating time 5 seconds, actual test results showed that the temperature difference between the surface layer and the core layer of the test board was 3.0℃;

[0116] (5) Gradient slow cooling roll forming: The rolls pass through constant temperature electric heating rollers at 200℃→150℃→80℃→40℃ in sequence. The rolling speed is synchronized with the linear module (1m / min). After cooling to room temperature, the high thermal conductivity equalizing pressure component is disassembled.

[0117] (6) Post-processed part performance: warpage amplitude 0.71mm / m, porosity 0.86%, interlaminar shear strength 1.2N / mm, tensile strength 205MPa, elastic modulus 27.8GPa.

[0118] Example 5: CF / PEEK composite material (optimized crystallization process)

[0119] (1) Specifications of the test plate to be treated: thickness 2mm, carbon fiber volume fraction 64%, resin content 36%;

[0120] (2) Pretreatment: Wipe the surface of the test plate with anhydrous ethanol, and fix it tightly with the upper and lower high thermal conductivity graphite copper equal pressure components (thickness 1.0mm, thermal conductivity 380W / (m·K)) through the edge locking device. The flatness error of the test plate is ≤0.03mm.

[0121] (3) Parameter adaptation: set the infrared heating temperature to 350℃, the distance between the upper and lower heating lamps to 12mm (the distance between the heating lamp and the high thermal conductivity equalizing pressure component to 4mm), and the heating power to 10kW;

[0122] (4) Double-sided infrared heating: linear module speed 1m / min, heating time 5 seconds, actual test results showed a temperature difference of 2.8℃ between the surface and core layers of the test board;

[0123] (5) Gradient slow cooling roll forming: pass through 340℃→280℃→250℃ (isothermal holding for 20s)→150℃→50℃ constant temperature electric heating rollers in sequence, and disassemble the high thermal conductivity equalizing pressure component after cooling to room temperature.

[0124] In the pre-rolling zone near the double-sided heating area, which is the isothermal electric heating rolling zone upstream of the isothermal crystallization zone and at a higher temperature than the isothermal crystallization zone, the resin is still in a molten or semi-molten state. At this time, a relatively low rolling pressure is used, with a pressure range of 100N to 200N, in order to maintain the flow and rearrangement ability of the resin molecular chains and reduce the interference of excessive shear force on the fiber structure and subsequent crystallization process. Meanwhile, the cooling rate at this stage is 10℃ / min to 20℃ / min.

[0125] Subsequently, the test plate enters the isothermal crystallization zone, which needs to be located within the range of resin crystallization peak temperature (Tc) ±30℃, i.e., the 250℃ constant temperature electric heating roller pressing zone. Medium roller pressing pressure is applied, with a pressure range of 200N~300N, so that the resin can complete pore compaction and interface bonding while maintaining a stable crystallization temperature, which is conducive to forming a more uniform and stable crystal structure. The heat preservation time can be matched by increasing the number of constant temperature electric heating rollers or reducing the linear module moving speed.

[0126] In the subsequent slow cooling and shaping stage, specifically in the isothermal electric heating roller pressing zone downstream of the isothermal crystallization zone and at a lower temperature, the rolling pressure can be further increased as the resin gradually cures. The pressure range is 300N-500N to promote structural shaping and reduce residual internal stress. The cooling rate in this stage is 5℃ / min to 10℃ / min. When the surface temperature of the test plate is lower than the glass transition temperature, it can be rapidly cooled to the 50℃ isothermal electric heating roller pressing zone and room temperature using methods such as air cooling.

[0127] The pressure of the rollers at each stage is controlled by cylinders, and the moving speed of the linear module at each stage is set by PLC. The design is based on the spacing of the constant temperature electric heating rollers, the cooling rate, and the material properties. Through the coordinated matching between the temperature path, pressure path and crystallization process, it is beneficial to improve the crystallization uniformity, dimensional stability and interlayer bonding performance of thermoplastic composite materials, and further reduce warpage and internal defects.

[0128] (6) Post-processed part properties: crystallinity 31.7%, warpage 0.28mm / m, porosity 0.7%, short beam shear strength 92MPa, 0° tensile strength 1949MPa, elastic modulus 134GPa.

[0129] This embodiment further demonstrates that by adding an isothermal crystallization zone to the original process and using a customized cooling curve for the resin, precise control of crystallization behavior can be achieved while maintaining the heating uniformity advantage of the original process.

[0130] 1. Significantly improved crystallinity: The average crystallinity of the CF / PEEK composite material increased from 26.3% to 31.7%, effectively solving the problems of incomplete crystallization and large differences in crystallinity in different regions caused by rapid cooling;

[0131] 2. Further upgrade in dimensional accuracy: The warpage of the parts has been further reduced by more than 55%, and the warpage of CF / PEEK parts is controlled within 0.5mm / m, meeting the stringent requirements of high-precision structural parts in the aerospace field;

[0132] 3. Enhanced mechanical properties and service stability: The shear strength of the short beam is increased from 30%–50% to 45%–65%, and the porosity is further reduced to below 0.7%. The temperature resistance, fatigue resistance and long-term dimensional stability of the parts are significantly improved.

[0133] This optimization scheme can be flexibly switched according to the actual performance requirements of the parts: for ordinary industrial parts, the original process can be used to achieve higher production efficiency; for fields with extremely high performance requirements such as aerospace and high-end equipment, the optimized crystallization process can be used to obtain the best part quality.

[0134] Experimental Example: Comparative Experimental Data

[0135] In one verification embodiment of the present invention, a comparative experiment was conducted between the method of the present invention and existing common post-processing methods. Specifically, thermoplastic composite material test plates of the same type and specification (material CF / PEEK, thickness 2mm, fiber volume fraction 64%) were selected as test objects, and post-processing was performed using the method of the present invention (corresponding to Examples 2 / 5), oven heat treatment method, and traditional unilateral infrared heat treatment method, respectively.

[0136] The specific process steps of oven heat treatment are as follows: ① Pretreatment: Clean the surface of the thermoplastic composite material test plate to remove oil, dust, and impurities, and check that the test plate is undamaged; clean the mold to remove oil, dust, and other impurities, wipe it with anhydrous ethanol, and then let it air dry naturally. ② Laying auxiliary materials: Place the thermoplastic composite material test plate (as the substrate to be treated) on the mold, and lay the release film (to prevent the composite material from sticking to other layers), release cloth (to facilitate subsequent demolding), and breathable felt (to ensure smooth airflow during vacuum extraction) in sequence. Each layer should be laid flat and without wrinkles. Place a vacuum base on the breathable felt at the corner of the mold, and cut a double layer of breathable felt that matches the shape of the vacuum base and put it on the vacuum base (to eliminate the influence of the height difference of the vacuum base and ensure smooth airflow during vacuum extraction). ③ Vacuum bag sealing: Stick the sealing strip on the mold, cover it with the vacuum bag film, and seal the edge of the vacuum bag with the sealing strip to ensure good vacuum bag sealing. Make an opening in the vacuum bag membrane above the vacuum base, install a vacuum nozzle, connect the vacuum equipment to check the vacuum stability, and check if the vacuum bag is sealed properly. Place the sealed test plate into the oven, turn on the vacuum pump, and evacuate the vacuum bag to a vacuum level above 0.095 MPa, maintaining this level for a period of time to remove air bubbles. ④ Oven heat treatment: Set the oven heat treatment temperature to 220℃ and the time to 120 minutes, turn on the circulating air, and slowly raise the temperature to the set temperature, holding it at the set temperature for the set time. ⑤ Cooling and shaping: After the heat treatment is completed, cool the test plate to room temperature using the oven cooling method, remove the test plate, and remove the vacuum bag and auxiliary materials.

[0137] The specific process steps of traditional single-sided infrared heat treatment are as follows: ① Pretreatment: Clean the surface of the thermoplastic composite material test plate to remove oil, dust, and impurities. After checking that the test plate is undamaged, fix it on the fixture. A linear module is set below the fixture to control the movement of the test plate; ② Parameter adaptation: Set the infrared heating temperature to 350℃, the height of the infrared heating lamp from the upper surface of the test plate to about 8mm, the infrared heating power to 10kW, and the pressure of the pressure roller to 180N; ③ Single-sided infrared heat treatment: The linear module speed is 1m / min, the heating time is 10 seconds, and the test plate passes through infrared heating and pressure roller pressing in sequence to complete the single-sided infrared heat treatment; ④ Cooling and shaping: After the single-sided infrared heat treatment is completed, allow it to cool naturally to room temperature. This ensures that the three methods are carried out under comparable conditions.

[0138] The experimental results are shown in the table below:

[0139]

[0140] Comparative test results show that the basic process shown in Example 2 exhibits superior overall advantages in terms of temperature uniformity, processing cycle, and forming quality. Specifically, the method in Example 2 can control the temperature difference between the surface and core layers of the test plate to ≤5℃ during heating, while the temperature differences for oven heat treatment and traditional single-sided infrared heat treatment are approximately 15-25℃ and 15-30℃, respectively. Regarding the processing cycle, the overall processing time for the method in Example 2 can be controlled to 15-25 seconds, significantly shorter than the 2-4 hours required for oven heat treatment and also shorter than the 3-5 minutes required for traditional single-sided infrared heat treatment. In terms of deformation control, the warpage of the test plate treated by the method in Example 2 is ≤1mm, while the warpage of oven heat treatment and traditional single-sided infrared heat treatment are 5-8mm and 3-5mm, respectively. Regarding densification, the method in Example 2 can reduce porosity to ≤1% and increase the short beam shear strength by approximately 30%-50%, significantly better than oven heat treatment and traditional single-sided infrared heat treatment.

[0141] Furthermore, the optimized crystallization process shown in Example 5 adds an isothermal crystallization zone to the basic process shown in Example 2, and introduces temperature and pressure paths that match the resin crystallization behavior. Compared with the method in Example 2, the processing cycle of the method in Example 5 is extended to 15-30 minutes, but is still significantly shorter than the 2-4 hours of oven heat treatment; at the same time, the method in Example 5 further controls the warpage to ≤0.5mm, further reduces the porosity to ≤0.7%, and increases the short beam shear strength by 45%-65%. Therefore, the method in Example 5 is more suitable for thermoplastic composite parts with high requirements for dimensional accuracy, porosity control, interlayer bonding performance, and long-term service stability.

[0142] The comparative test results further demonstrate that by adding an isothermal crystallization zone to the original process and using a customized cooling curve for the resin, precise control of crystallization behavior can be achieved while maintaining the heating uniformity advantage of the original process.

[0143] 1. Significantly improved crystallinity: The average crystallinity of the CF / PEEK composite material increased from 26.3% to 31.7%, effectively solving the problems of incomplete crystallization and large differences in crystallinity in different regions caused by rapid cooling;

[0144] 2. Further upgrade in dimensional accuracy: The warpage of the parts has been further reduced by more than 55%, and the warpage of CF / PEEK parts is controlled within 0.5mm / m, meeting the stringent requirements of high-precision structural parts in the aerospace field;

[0145] 3. Enhanced mechanical properties and service stability: The shear strength of the short beam is increased from 30%-50% to 45%-65%, and the porosity is further reduced to below 0.7%. The temperature resistance, fatigue resistance and long-term dimensional stability of the parts are significantly improved.

[0146] This optimization scheme can be flexibly switched according to the actual performance requirements of the parts: for ordinary industrial parts, the original process can be used to achieve the highest production efficiency; for fields with extremely high performance requirements such as aerospace and high-end equipment, the optimized crystallization process can be used to obtain the best part quality.

[0147] The above results demonstrate that the method of the present invention, through the synergistic effect of double-sided heating and gradient slow cooling rolling, facilitates uniform heating, controlled cooling, and roll densification of thermoplastic composite material specimens, thereby reducing temperature gradients and internal stress accumulation, and promoting pore compaction and interlayer bonding. Specifically, the method in Example 2 focuses on completing the post-processing within a shorter cycle, making it suitable for applications requiring high processing efficiency. The method in Example 5 further introduces an isothermal crystallization zone and synergistic control of temperature and pressure paths, making it suitable for applications requiring high crystal quality, dimensional stability, and interlayer bonding performance. Therefore, compared with existing technologies, the method of the present invention has significant effects in improving dimensional accuracy, reducing warpage, and enhancing mechanical properties. The method in Example 2 significantly shortens the post-processing cycle; while the method in Example 5 has a relatively longer processing cycle, it is still shorter than oven heat treatment and further improves crystal quality, dimensional stability, and interlayer bonding performance.

[0148] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A post-processing method for thermoplastic composite materials, characterized in that, Includes the following steps: The thermoplastic composite material test plate is heated on both sides, so that the upper and lower sides of the test plate are heated simultaneously and the temperature is raised to a temperature that matches the melting temperature of the resin in the test plate. The heated test plates are continuously conveyed. During the continuous transport of the test plate, the test plate passes through at least two rolling zones with progressively decreasing temperatures along the transport direction. The test plate is rolled and cooled simultaneously in each rolling zone, so that the test plate experiences a progressively decreasing temperature path along the transport direction until it is cooled to the predetermined temperature.

2. The post-processing method according to claim 1, characterized in that, The distance between the rolling zone and the double-sided heating zone is no more than 50 mm.

3. The post-processing method according to claim 1, characterized in that, Each rolling zone is formed by multiple sets of constant-temperature electric heating rollers arranged sequentially along the conveying direction; Optionally, each of the thermostatic heating rollers is provided with a lifting device below it, which is used to drive the thermostatic heating rollers to lift and press down, so as to adapt to thermoplastic composite material test plates of different thicknesses.

4. The post-processing method according to claim 1 or 3, characterized in that, Each rolling zone is equipped with a temperature control unit so that the temperature of each rolling zone can be adjusted independently.

5. The post-processing method according to claim 4, characterized in that, During the process of the test plate passing through the at least two stages of rolling zones with progressively decreasing temperatures along the conveying direction, an isothermal crystallization zone is set up so that the test plate is kept within the crystallization temperature range of the corresponding thermoplastic resin for a predetermined time, so as to promote the formation of the thermoplastic resin crystal structure and reduce the residual stress inside the test plate. Optionally, the temperature of the isothermal crystallization zone is within the range of the crystallization peak temperature Tc ± 30℃ of the thermoplastic resin, and is maintained at this temperature for 5 to 60 seconds.

6. The post-processing method according to claim 5, characterized in that, The test plate undergoes a first cooling stage before entering the isothermal crystallization zone and a second cooling stage after passing through the isothermal crystallization zone. The cooling rate of the first cooling stage is greater than the cooling rate of the second cooling stage. Optionally, the cooling rate of the first cooling stage is 10℃ / min to 20℃ / min, and the cooling rate of the second cooling stage is 5℃ / min to 10℃ / min. Optionally, each rolling zone forms a pressure path matching the temperature path along the test plate transport direction, so that different rolling pressures are applied to the pre-rolling zone, the isothermal crystallization zone, and the subsequent slow cooling and shaping zone near the double-sided heating zone; wherein, the rolling pressure of the pre-rolling zone near the double-sided heating zone is 100N to 200N, the rolling pressure of the isothermal crystallization zone is 200N to 300N, and the rolling pressure of the subsequent slow cooling and shaping zone is 300N to 500N.

7. The post-processing method according to claim 1, characterized in that, The double-sided heating is achieved through infrared heating modules arranged symmetrically at the top and bottom; Optionally, each group of infrared heating modules includes multiple infrared heating lamps, which are arranged in a uniformly staggered manner. Optionally, each group of infrared heating modules includes 6 to 8 infrared heating lamps; Optionally, the upper and lower sets of infrared heating modules are mounted in an inverted C-shape on the screw lifting device; Optionally, the lead screw lifting device is used to adjust the distance between the upper and lower sets of infrared heating modules.

8. The post-processing method according to claim 7, characterized in that, The double-sided heating uses mid-wave infrared heating. Optionally, the wavelength of the mid-wave infrared is 2–5 μm; Optionally, the heating time on both sides is 3 to 8 seconds.

9. The post-processing method according to claim 1, characterized in that, The test plate is fitted with a high thermal conductivity equalizing pressure component during the double-sided heating process to improve the uniformity of heating and suppress the deformation of the test plate during the heating process. Optionally, the pressure equalizing member is made of graphite-copper composite material; Optionally, the pressure equalizing component is mounted on a lifting device, which is mounted on a sliding table of the transmission structure.

10. The post-processing method according to any one of claims 1 to 9, characterized in that, The thermoplastic resin in the thermoplastic composite material is selected from one or more of PEEK, PP, PA and PC.

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