Method for the production of thermoplastic composites, thermoplastic composites and applications

Abstract

The application provides a thermoplastic composite material preparation method, a thermoplastic composite material and an application thereof. The preparation method comprises: performing at least one preforming process on a laminated preform to form a blank for forming the thermoplastic composite material; and the preforming process comprises: a heating stage for heating to a melting temperature at a first preset heating rate; a pressure maintaining stage for maintaining a preset time length at a preset pressure range in a stepped pressure increasing manner at the melting temperature; and a cooling stage for cooling to a preset temperature at a preset cooling rate at the second preset pressure. The thermoplastic composite material preparation method provided by the application can effectively reduce the size of spherulites by controlling the melting temperature in the heating stage, so that the mechanical properties of the thermoplastic composite material, such as the interlaminar shear strength, the in-plane shear strength and the compressive strength, are obviously improved, and the thermoplastic composite material is suitable for high-performance manufacturing of aviation structural parts.

Description

Technical Field

[0001] This disclosure relates to the field of composite materials technology, and in particular to a method for preparing thermoplastic composite materials, thermoplastic composite materials and their applications. Background Technology

[0002] Thermoplastic resin is an important component of continuous fiber reinforced thermoplastic composites, serving as the matrix material to provide structural integrity and processing flexibility. The high toughness, high temperature resistance, and chemical stability exhibited by continuous fiber reinforced thermoplastic composites mainly stem from the intrinsic properties of the thermoplastic resin matrix.

[0003] Existing research indicates that reducing the spherulite size of the matrix resin in continuous fiber-reinforced thermoplastic composites helps improve the mechanical properties of the composites. This is typically achieved by adding nucleating agents to introduce heterogeneous nucleation sites, thereby lowering the free energy barrier during polymer crystallization and increasing nucleation density, thus refining the spherulites. However, compatibility issues between nucleating agents and the polymer matrix lead to significant differences in the efficiency of different nucleation systems, and this instability limits their widespread application in industrial production. Summary of the Invention

[0004] To overcome the problems existing in related technologies, this disclosure provides a method for preparing thermoplastic composite materials, thermoplastic composite materials and their applications. The thermoplastic composite materials have excellent mechanical properties, and the compressive strength, in-plane shear strength and interlaminar shear strength are significantly improved.

[0005] According to a first aspect of this application, a method for preparing a thermoplastic composite material is provided, the method comprising: The laminated preformed material is subjected to at least one preforming process to form a blank for use in forming the thermoplastic composite material; the preforming process includes: During the heating stage, the temperature is increased to the melting temperature at a first preset heating rate; the first preset heating rate is 1~25℃ / min; the melting temperature is 300~450℃; During the pressure holding stage, at the melting temperature, the pressure is maintained within a preset pressure range in a stepped manner for a preset duration; the preset pressure range is 0.3~4.2MPa; the preset duration is 5~300 minutes; and the stepped pressure range is 1.0~1.7MPa. During the cooling phase, under the second preset pressure, the temperature is cooled to a preset temperature at a preset cooling rate; the cooling rate is 1~34℃ / min; and the preset temperature is 10~300℃.

[0006] In some embodiments of this application, maintaining the pressure at the melting temperature for a preset duration in a stepped manner within a preset pressure range includes: In the first stage, the pressure is maintained at a first preset pressure for a first preset duration; in the second stage, the pressure is maintained at a second preset pressure for a second preset duration; the first preset pressure is 0.3~1.8MPa; the first preset duration is 5~80 minutes; the second preset pressure is 1.1~4.2MPa; the second preset duration is 50~300 minutes.

[0007] In some embodiments of this application, when the preforming process is performed n times, the melting temperature of the nth time is less than the melting temperature of the (n-1)th time; n is greater than or equal to 2.

[0008] In some embodiments of this application, when the preforming process is performed twice. The melt temperature of the second preforming process is lower than the melt temperature of the first preforming process; and / or The preset temperature range for the first preforming process is 200~250 degrees Celsius; the preset temperature range for the second preforming process is 10~35 degrees Celsius.

[0009] In some embodiments of this application, the preform material includes carbon fiber reinforced thermoplastic resin prepreg or a composition of carbon fiber fabric and thermoplastic resin powder.

[0010] In some embodiments of this application, when the preform is a carbon fiber reinforced thermoplastic resin prepreg, the mass content of the resin in the carbon fiber reinforced thermoplastic resin prepreg is 25.3% to 43.6%; the volume content of the carbon fiber is 47.2% to 78.5%; and the thickness of the preform is 0.08 to 0.21 mm. When the preform material is a composition of carbon fiber fabric and thermoplastic resin powder, the areal density of the carbon fiber fabric is 128~284 g / m³. 2 .

[0011] In some embodiments of this application, before heating to the molding temperature at a second heating rate and molding the preform at the molding temperature to form the thermoplastic composite material, the preparation method further includes: The blank is transferred to the forming mold at a speed less than the preset transfer time, which is 18 seconds.

[0012] According to a second aspect of this application, a thermoplastic composite material is provided, prepared according to the above-described method for preparing a thermoplastic composite material. The thermoplastic composite material has a porosity of less than 2.0% and an interlaminar shear strength ≥80 MPa.

[0013] According to a third aspect of this application, the application of the thermoplastic composite material or the preparation method described herein in the field of aerospace structural components is provided.

[0014] The technical solution provided in this application may include the following beneficial effects: This application forms a blank by performing at least one preforming process on the layered preformed material, wherein performing at least one preforming process can refine the grains of the preformed material without adding additional nucleating agents, thereby improving the mechanical strength of the thermoplastic composite material. In the preforming process, during the heating stage, the temperature is raised to the melting temperature at a first preset heating rate. Controlling the melting temperature effectively increases the nucleation density of the thermoplastic resin matrix and significantly reduces the spherulite size, thereby improving the interfacial bonding between carbon fibers and thermoplastic resin. During the holding pressure stage, at the melting temperature, the pressure is increased in stages within a preset pressure range and maintained for a preset duration. Through this staged pressure increase, the first stage avoids carbon fiber misalignment and structural deformation caused by instantaneous high-pressure impact, while the second stage allows for deep wetting of the carbon fibers, forming and strengthening a continuous and dense carbon fiber-thermoplastic resin interface, reducing the porosity of the thermoplastic composite material. During the cooling stage, the temperature is cooled to the preset temperature at a preset cooling rate under a second preset pressure. The second preset pressure in the cooling stage is consistent with the second preset pressure in the holding pressure stage, allowing the thermoplastic resin to more tightly encapsulate the carbon fibers, resulting in a strong interfacial bond. Strictly controlling the cooling rate and setting an appropriate final cooling temperature allows the thermoplastic resin to complete crystallization and curing under controllable conditions, forming a fine and uniform crystal structure and improving the mechanical properties of the thermoplastic composite material.

[0015] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0017] Figure 1 This is a flowchart illustrating a method for manufacturing thermoplastic composite materials according to an exemplary embodiment of this application.

[0018] Figure 2 This is an example of the geometry of an airfoil rib part used in this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this disclosure will be clearly and completely described below in conjunction with the embodiments of this disclosure. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this disclosure. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0020] In related technologies, reducing the spherulite size of the matrix resin in continuous fiber-reinforced thermoplastic composites helps improve the mechanical properties of the composites. Adding nucleating agents introduces heterogeneous nucleation sites to lower the free energy barrier during polymer crystallization, thereby increasing nucleation density and refining spherulites. However, the compatibility issues between nucleating agents and the polymer matrix lead to significant differences in the efficiency of different nucleation systems, and this instability limits its widespread application in industrial production.

[0021] Based on this, an exemplary embodiment of this application provides a method for preparing a thermoplastic composite material, the method comprising: The laminated preforms are subjected to at least one preforming process to form a blank for use in the formation of thermoplastic composites.

[0022] The layered preform undergoes at least one preforming process, such as two or three. In the first preforming process, the grain size of the thermoplastic resin is only tens of nanometers; after the second preforming process, the grains are refined, reaching within ten nanometers; and after the third preforming process, the grain size continues to decrease. Through multiple preforming processes, the number of nucleation sites increases progressively, and the crystal growth space is continuously compressed. Typically, after 2-3 preforming processes, the grain size can be refined from tens of nanometers to within ten nanometers with a uniform size distribution, and there are no obvious weak crystallization regions within the system. The reduced grain size significantly increases the number of grain boundaries per unit volume, hindering chain segment slippage and dislocation movement under external forces, eliminating grain boundary stress concentration points, and improving mechanical properties. By performing multiple preforming processes, grain refinement is achieved without adding additional nucleating agents, thus improving the mechanical strength of thermoplastic composites.

[0023] In the exemplary embodiments provided in this application, the preform material includes carbon fiber reinforced thermoplastic resin prepreg or a composition of carbon fiber fabric and thermoplastic resin powder.

[0024] When the preform is a carbon fiber reinforced thermoplastic resin prepreg, the mass content of thermoplastic resin in the carbon fiber reinforced thermoplastic resin prepreg is 25.3% to 43.6%, that is, the mass of thermoplastic resin accounts for 25.3% to 43.6% of the mass of the carbon fiber reinforced thermoplastic resin prepreg. For example, it can be 25.3%, 28.9%, 32.4%, 38.5%, 42.3%, or 43.6%. The mass content of thermoplastic resin can also be any value between the exemplary mass contents, for example, the mass content of thermoplastic resin can be 28.9% to 38.5%.

[0025] The volume content of carbon fiber is 47.2% to 78.5%, meaning that the volume of carbon fiber accounts for 47.2% to 78.5% of the volume of the carbon fiber reinforced thermoplastic resin prepreg. For example, it can be 47.2%, 52.9%, 57.3%, 61.6%, 66.3%, 72.1%, or 78.5%. The volume content of carbon fiber can also be any value between the exemplary volume contents, for example, the volume content of carbon fiber can be 52.9% to 66.3%.

[0026] The thickness of the preform can be 0.08 to 0.21 mm, for example, 0.08 mm, 0.11 mm, 0.15 mm, 0.17 mm, 0.19 mm, or 0.21 mm. The thickness of the preform can also be any value between the exemplary volume fractions, for example, the thickness of the preform can be 0.11 mm to 0.17 mm.

[0027] After undergoing multiple preforming processes, carbon fiber reinforced thermoplastic resin prepregs form a dense and uniform microcrystalline layer at the interface between the carbon fibers and the thermoplastic resin. When the prepreg bears external loads, this microcrystalline layer evenly distributes the load across the carbon fibers, improving the shear strength of the prepreg. Simultaneously, the repeated melting and flow of the thermoplastic resin fills the micropores remaining after the initial impregnation, ensuring thorough wetting of the voids between the carbon fibers and complete coating of the carbon fiber surface. This stabilizes and enhances the mechanical properties of the thermoplastic composite. Controlling the thermoplastic resin content to 25.3%–43.6% ensures the formation of a continuous and uniform interface layer on the carbon fiber surface, significantly strengthening the bond strength between the carbon fibers and the thermoplastic resin and improving the interlaminar shear strength of the prepreg.

[0028] Controlling the volume content of carbon fiber between 47.2% and 78.5% ensures uniform dispersion and thorough coating by the thermoplastic resin. In carbon fiber reinforced thermoplastic resin prepreg, if the carbon fibers are arranged in bundles and the volume content is controlled between 47.2% and 78.5%, performing at least one preforming process allows the thermoplastic resin to further coat the carbon fibers, enhancing their load-bearing capacity. Simultaneously controlling the thickness of the carbon fiber reinforced thermoplastic resin prepreg between 0.08 and 0.21 mm ensures uniform single-layer layup thickness, resulting in uniform stress distribution in all directions after stacking, avoiding excessive local stress concentration, and effectively reducing the probability of molding defects.

[0029] The carbon fiber is selected from one or more of T700, T800, or T1100 grades, such as T700. T700 grade carbon fiber has stable high tensile strength and high modulus, excellent interfacial bonding with thermoplastic resins, and can efficiently transfer stress, thereby improving mechanical strength.

[0030] The thermoplastic resin is one or more of polyetheretherketone (PEEK) resin or polyphenylene sulfide (PPS) resin. PEEK resin possesses high tensile strength and good flowability in the molten state, allowing it to fully wet the pores of carbon fibers, forming a dense and robust carbon fiber-thermoplastic resin interface. This ensures that external stress is evenly distributed at the carbon fiber-thermoplastic resin interface, improving the mechanical properties of the thermoplastic composite material. PPS resin has good tensile strength, low melt viscosity, and good flowability, allowing it to fully penetrate the pores of carbon fibers, forming a uniform and continuous carbon fiber-thermoplastic resin interface, and evenly bearing external stress.

[0031] When the preform is a composition of carbon fiber fabric and thermoplastic resin powder, the areal density of the carbon fiber fabric is 128~284 g / m2, for example, it can be 128 g / m2, 133 g / m2, 145 g / m2, 159 g / m2, 167 g / m2, 188 g / m2, 197 g / m2, 206 g / m2, 213 g / m2, 229 g / m2, 235 g / m2, 243 g / m2, 258 g / m2, 269 g / m2, 275 g / m2, or 284 g / m2. The areal density of the carbon fiber fabric can also be any value between the exemplary areal densities; for example, the areal density of the carbon fiber fabric can be 167 g / m2~285 g / m2.

[0032] Thermoplastic resin powder has a small particle size and strong fluidity after melting, allowing it to fully penetrate the pores of carbon fiber fabric, facilitating uniform impregnation. Furthermore, it exhibits no irreversible cross-linking reaction, and the composition can be repeatedly heated and melted for molding. The inherent weave structure of the carbon fiber fabric ensures more balanced in-plane mechanical properties. Controlling the areal density of the carbon fiber fabric between 128 and 284 g / m² ensures the retention of thermoplastic resin penetration channels between the carbon fibers, resulting in uniform coating of the molded carbon fiber fabric with thermoplastic resin and the formation of a continuous and dense carbon fiber-thermoplastic resin interface. This facilitates efficient transfer of external loads from the thermoplastic resin to the carbon fibers, improving the mechanical properties of the thermoplastic composite material.

[0033] Exemplary embodiments of this disclosure provide a molding method for refining the spherulite size of thermoplastic resins without the need for external nucleating agents, solely through temperature control, thereby improving the mechanical properties of continuous fiber reinforced thermoplastic composites, simplifying the process, and enhancing production stability.

[0034] In the exemplary embodiments provided in this application, the preforming process includes: S100: Heating stage, heating to the melting temperature at a first preset heating rate; the first preset heating rate is 1~25℃ / min; the melting temperature is 300~450℃.

[0035] In this step, the preform material is stacked layer by layer according to a preset layup sequence. The heating stage is initiated, and a first preset heating rate is set to 1~25℃ / min, for example, 1℃ / min, 5℃ / min, 8℃ / min, 11℃ / min, 15℃ / min, 17℃ / min, 20℃ / min, 23℃ / min, or 25℃ / min. The first preset heating rate can also be any value between the exemplary heating rates, for example, 5℃ / min~17℃ / min. The preform material temperature reaches a melting temperature of 300~450℃, for example, 300℃, 343℃, 389℃, 412℃, 425℃, 436℃, or 450℃. The melting temperature can also be any value between the exemplary melting temperatures, for example, 389℃~436℃. The preset layup sequence can be stacked alternately at any angle, for example, alternating between 0° and 90°.

[0036] In one exemplary embodiment, preforms stacked layer by layer can be placed into a heating container. The heating container is heated uniformly at a set rate, and a heating pressure of 0.1~1.2MPa is applied, for example, 0.1MPa, 0.3MPa, 0.6MPa, 0.8MPa, 1.05MPa, or 1.2MPa. The heating pressure can also be any value between the exemplary heating pressures, for example, 0.3MPa~1.05MPa. This continues until the preform temperature reaches a melting temperature of 300~450℃. The preset layering sequence is alternating between 0° and 90° stacking.

[0037] In the exemplary embodiments provided in this application, a first preset heating rate is set, which allows the thermoplastic resin powder to gradually melt and impregnate the carbon fiber layer by layer, fully expelling air from the gaps between the thermoplastic resin powder and the carbon fiber fabric. This ensures a continuous and uniform carbon fiber-thermoplastic resin interface, improving the stress transfer capability of the carbon fiber-thermoplastic resin interface. A melting temperature of 300~450℃ allows the thermoplastic resin to melt while preventing thermal oxidative degradation of the thermoplastic resin molecular chains, thus improving mechanical strength. It also prevents surface structural damage to the thermoplastic resin due to high temperatures, stabilizing and enhancing the tensile strength and interlaminar shear of the preform. Controlling the heating pressure to 0.1~1.2MPa allows for regulation of the thermoplastic resin's softening and melting process, ensuring a uniform and stable heating and melting rate. This allows the thermoplastic resin molecular chains to gradually adhere to the carbon fiber, laying a solid foundation for deep penetration molding of the thermoplastic resin in the subsequent pressure holding stage.

[0038] During the multiple heating stages of the preforming process, the ordered aggregates of thermoplastic resin crystals and chain segments effectively increase the nucleation density of the thermoplastic resin through a self-nucleation effect. This refines the originally coarse spherulites into uniformly sized microcrystals, improving the toughness of the thermoplastic resin and preventing brittle cracking. Furthermore, the uniform fine-grained structure of the thermoplastic resin eliminates the stress concentration caused by large spherulites, simultaneously improving the impact resistance of the thermoplastic composite material.

[0039] In the exemplary embodiments provided in this application, when the preforming process is executed n times, the melting temperature of the nth time is less than the melting temperature of the (n-1)th time; n is greater than or equal to 2, for example, it can be 2, 3, or 4.

[0040] In multiple preforming processes, the melting temperature of the nth preforming step is lower than that of the (n-1)th preforming step. This allows for gradual refinement and homogenization of the grains while avoiding damage to the crystalline framework of the thermoplastic resin, ultimately leading to a steady improvement in the mechanical properties of the thermoplastic composite material. After cooling in the first preforming process, crystals form within the thermoplastic resin. Subsequent preforming steps progressively lower the melting temperature, increasing the number of nucleation sites and continuously compressing the crystal growth space. The grain size decreases from tens of nanometers to within ten nanometers, ultimately forming a uniform crystalline structure. This avoids the problems of coarse grains and uneven distribution caused by re-nucleation after complete melting at high temperatures.

[0041] In the exemplary embodiments provided in this application, when the preforming process is executed 2 times, the melting temperature of the second preforming process is lower than the melting temperature of the first preforming process; and / or the preset temperature range of the first preforming process is 200~250℃, for example, 200℃, 210℃, 240℃, 245℃; the preset temperature range of the second preforming process is 10~35℃, for example, 10℃, 16℃, 26℃, 35℃.

[0042] In the two preforming processes, controlling the preset temperature of the first preforming process within the range of 200~250℃ instead of lowering it to room temperature allows for the optimization of thermoplastic composite material properties at the microstructural level by controlling the relaxation state of thermoplastic resin segments, the crystal growth process, and the thermal stress level, thereby achieving a steady improvement in the mechanical properties of thermoplastic composite materials. If cooled to room temperature, the thermoplastic resin molecular chains completely freeze as the temperature decreases, and the original thermoplastic resin crystal structure must be completely destroyed when the second preforming process heats up to melt it.

[0043] S200: During the pressure holding stage, at the melting temperature, the pressure is maintained for a preset duration in a stepped manner within a preset pressure range; the preset pressure range is 0.3~4.2 MPa, for example 0.3 MPa, 1.4 MPa, 3.1 MPa, 4.2 MPa; the preset duration is 5~300 minutes, for example 5 minutes, 113 minutes, 247 minutes, 300 minutes; the stepped pressure range is 1.0~1.7 MPa, for example 1.0 MPa, 1.2 MPa, 1.5 MPa, 1.7 MPa.

[0044] The holding pressure stage employs a stepped pressure increase for a preset duration. This stepped pressure increase gradually expels gas from the thermoplastic resin, avoiding gas generation from instantaneous high pressure, effectively reducing internal porosity, and allowing the thermoplastic resin to gradually impregnate the carbon fibers, forming and strengthening the carbon fiber-thermoplastic resin interface. Controlling the stepped pressure range drives the thermoplastic resin to smoothly penetrate the carbon fiber gaps, maintaining the carbon fiber orientation and the structural integrity of the thermoplastic resin, and improving the interlaminar shear strength of the thermoplastic composite. Limiting the preset pressure range and preset duration matches the flow viscosity characteristics of the molten thermoplastic resin, avoiding insufficient impregnation of the carbon fibers due to insufficient pressure, while preventing carbon fiber buckling and excessive loss of thermoplastic resin due to pressure overload.

[0045] In the exemplary embodiments provided in this application, maintaining a preset pressure for a preset duration in a stepped pressure manner within a preset pressure range at the melting temperature includes: In the first stage, the pressure is maintained at a first preset pressure for a first preset duration; in the second stage, the pressure is maintained at a second preset pressure for a second preset duration. The first preset pressure is 0.3~1.8 MPa, for example, 0.3 MPa, 0.8 MPa, 1.2 MPa, 1.8 MPa; the first preset duration is 5~80 minutes, for example, 5 minutes, 24 minutes, 47 minutes, 80 minutes; the second preset pressure is 1.1~4.2 MPa, for example, 1.1 MPa, 2.6 MPa, 3.5 MPa, 4.2 MPa; the second preset duration is 50~300 minutes, for example, 50 minutes, 106 minutes, 238 minutes, 300 minutes.

[0046] The pressure holding stage employs a two-stage stepped pressure increase process. The first stage uses a first preset pressure, which drives the molten thermoplastic resin to slowly spread and evenly coat the carbon fiber surface, preventing misalignment and structural deformation caused by instantaneous high pressure. The second stage uses a second preset pressure, higher than the first, which allows for deep impregnation of the carbon fiber, forming and strengthening a continuous and dense carbon fiber-thermoplastic resin interface. Limiting the pressure and preset duration of the first stage drives the molten thermoplastic resin to slowly spread and evenly coat the carbon fiber surface, preventing bending, misalignment, and excessive resin overflow caused by instantaneous high pressure. Limiting the pressure and preset duration of the second stage promotes deep penetration of the molten thermoplastic resin into the carbon fiber gaps, fully expelling trapped air and micropores, reducing porosity, and improving the tensile strength and interlaminar shear strength of the composite material.

[0047] S300: Cooling stage, under the second preset pressure, cool to the preset temperature at a preset cooling rate; the cooling rate is 1~34℃ / min, for example, it can be 1℃ / min, 14℃ / min, 26℃ / min, 34℃ / min; the temperature is 10~300℃, for example, it can be 10℃, 116℃, 238℃, 300℃.

[0048] In the exemplary embodiments provided in this application, the second preset pressure is limited to 1.1~4.2 MPa, consistent with the second preset pressure during the holding stage. This allows the thermoplastic resin to more tightly encapsulate the carbon fibers, resulting in a strong bond between the carbon fiber and the thermoplastic resin interface. The constant pressure promotes uniform and refined crystal formation within the thermoplastic resin, improving mechanical properties. Controlling the cooling rate and setting a suitable final cooling temperature allows the thermoplastic resin to form a fine and uniform crystalline structure under controllable conditions, enhancing mechanical strength. Controlling the preset cooling rate avoids stress concentration and microcrack formation within the thermoplastic resin caused by excessively rapid cooling, while also preventing coarse-grained thermoplastic resin due to excessively slow cooling.

[0049] In the exemplary embodiments provided in this application, the preparation method further includes: The material is heated to the molding temperature at a second heating rate and then molded at the molding temperature to form a thermoplastic composite material; the second heating rate is 3~26℃ / min; the molding temperature is 340~390℃.

[0050] In this step, the blank is placed in a high-temperature heating chamber and pre-melted using a second heating rate of 3~26℃ / min. For example, the heating rate can be 3℃ / min, 10℃ / min, 14℃ / min, 18℃ / min, 21℃ / min, or 26℃ / min. This uniform heating rate softens and melts the blank layer by layer, avoiding localized overheating that could lead to thermoplastic resin degradation and structural deterioration. The molding temperature is 340~390℃, for example, 340℃, 350℃, 370℃, or 390℃. This ensures that the thermoplastic resin is fully melted and maintains good fluidity. It avoids insufficient melting and poor wetting due to excessively low temperatures, and thermal degradation and molecular chain breakage of the thermoplastic resin due to excessively high temperatures. This guarantees the high strength and high toughness of the thermoplastic resin and promotes self-nucleation-dominated crystallization behavior in the thermoplastic composite material.

[0051] In the exemplary embodiments provided in this application, before heating to the molding temperature at a second heating rate and molding the preform at the molding temperature to form a thermoplastic composite material, the preparation method further includes: The blank is transferred to the forming mold at a speed less than the preset transfer time, which is 18 seconds.

[0052] Controlling the transfer time to less than 18 seconds, such as 17 seconds, 12 seconds, 9 seconds, or 6 seconds, can prevent the thermoplastic resin viscosity from rising sharply due to the rapid cooling of the blank exposed to the environment. This ensures that the thermoplastic resin is always in a suitable state of flow and wetting, fully encapsulating the carbon fiber and reducing defects and internal pores at the thermoplastic resin-carbon fiber interface.

[0053] In the exemplary embodiments of this disclosure, a specific example is provided of a method for preparing thermoplastic composite materials according to the exemplary embodiments of this disclosure.

[0054] The laminated preformed material undergoes two preforming processes to form a blank for use in forming a thermoplastic composite material; the preforming process includes: During the heating stage, the temperature is increased to the melting temperature at a first preset heating rate; the first preset heating rate is 1~25℃ / min; the melting temperature is 300~450℃; During the pressure holding stage, at the melting temperature, the pressure is maintained in a stepped manner within a preset pressure range for a preset duration; the preset pressure range is 0.3~4.2MPa; the preset duration is 5~300 minutes; and the stepped pressure range is 1.0~1.7MPa. During the cooling phase, the temperature is cooled to a preset temperature at a preset rate under a second preset pressure; the cooling rate is 1~34℃ / min; the preset temperature is 10~300℃.

[0055] To more clearly explain the technical solution of this application, specific embodiments of thermoplastic composite materials are provided. The beneficial effects of selecting the above-mentioned range of component contents will be explained through specific experimental data provided in the specific embodiments.

[0056] Example It should be noted that the raw materials used in the following examples are all commercially available. Specifically, the carbon fiber fabric (T7003K 200gsm) was purchased from Zhongfu Shenying Carbon Fiber Co., Ltd.; the polyetheretherketone resin powder (ZYPEEK 330UPF) was purchased from Jilin Zhongyan Polymer Materials Co., Ltd. Example 1: A method for preparing an epoxy resin matrix, comprising the following steps: A preform (a composition of carbon fiber fabric and thermoplastic resin powder, with a mass ratio of carbon fiber fabric to thermoplastic resin powder of 60:40 to 70:30) is subjected to at least one preforming process to form a blank for use in forming a thermoplastic composite material; the preforming process includes: S100: During the heating stage, the mold is heated to a melting temperature of 400°C at a first preset heating rate of 10°C / min, wherein the heating pressure is 0.5MPa.

[0057] S200: During the pressure holding stage, at a melting temperature of 400℃, in the first stage, a first preset pressure of 1.2MPa is maintained for 10 minutes for a first preset duration; in the second stage, a second preset pressure of 2.5MPa is maintained for 30 minutes for a second preset duration.

[0058] S300: During the cooling stage, the mold is cooled to the preset temperature of 25°C at a preset cooling rate of 10°C / min under the second preset pressure of 2.5MPa, and then demolded.

[0059] Example 2 This embodiment is basically the same as Embodiment 1, except that the preforming process is performed twice, and the melting temperature in the heating stage of the second preforming process is 345°C.

[0060] Example 3 This embodiment is basically the same as embodiment 2, except that the preforming process is performed three times, and the melting temperature in the heating stage of the third preforming process is 340°C.

[0061] Example 4 This embodiment is basically the same as embodiment 2, except that the melting temperature in the heating stage of the second preforming process is 360°C.

[0062] Example 5 This embodiment is basically the same as embodiment 4, except that the melting temperature during the heating stage of the second preforming process is 370°C.

[0063] Example 6 This embodiment is basically the same as embodiment 4, except that the melting temperature during the heating stage of the second preforming process is 390°C.

[0064] Example 7 This embodiment is basically the same as Embodiment 2, except that: the pressure holding stage is divided into three stages of step pressure increase. At a melting temperature of 400°C, in the first stage, a first preset pressure of 1.2MPa is maintained for 20 minutes for a first preset duration; in the second stage, a second preset pressure of 2.2MPa is maintained for 40 minutes for a second preset duration; and in the third stage, a third preset pressure of 2.7MPa is maintained for 30 minutes for a third preset duration.

[0065] Example 8 This embodiment is basically the same as Embodiment 2, except that the mass ratio of carbon fiber fabric to thermoplastic resin powder is 55:45.

[0066] Example 9 This embodiment is basically the same as Embodiment 2, except that the mass ratio of carbon fiber fabric to thermoplastic resin powder is 45:55.

[0067] Comparative Example Comparative Example 1: The main difference between this comparative example and Example 2 is that the melting temperature during the heating stage of the second preforming process is 410°C.

[0068] Comparative Example 2: The main difference between this comparative example and Example 2 is that the first preset pressure during the pressure holding stage is 2.2 MPa, and the second preset pressure is 1.5 MPa.

[0069] Application examples Application Example 1: Fabrication of a typical wing rib component In this application example, the thermoplastic composite material prepared in Example 1 is used as the blank. The blank is placed in a high-temperature heating box and heated to the molding temperature of 370°C at a second heating rate of 10°C / min. The blank is then molded at the molding temperature and transferred to the molding mold at a speed of less than 10 seconds of preset transfer time. A pressure of 2.5 MPa is applied and the blank is cooled at a cooling rate of 10°C / min.

[0070] Table 1 provides the test results of impact properties, tensile and flexural properties, and glass transition temperature of the thermoplastic composite materials prepared by the preparation methods of Examples 1-7, Comparative Examples 1-2, and Application Examples.

[0071] Table 1.

[0072] As can be seen from the performance comparison results of Examples 1-9, Comparative Examples, and Application Example 1 above, this application, by performing multiple preforming processes, with the melting temperature during the heating stage within the self-nucleation temperature range of the thermoplastic resin (preferably 360-370°C), can effectively increase the nucleation density of the preform and refine the spherulite size, thereby significantly improving the interlaminar shear strength, in-plane shear strength, and compressive strength of the thermoplastic composite material. Among these, when performing two preforming processes, the interlaminar shear performance improvement is most significant when the melting temperature during the second heating stage is 370°C. Furthermore, the method of this application has good applicability to preforming materials that are carbon fiber reinforced thermoplastic resin prepreg or compositions of carbon fiber fabric and thermoplastic resin powder. It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0073] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a thermoplastic composite material, characterized in that, The preparation method includes: The laminated preformed material is subjected to at least one preforming process to form a blank for use in forming the thermoplastic composite material; the preforming process includes: During the heating stage, the temperature is increased to the melting temperature at a first preset heating rate; the first preset heating rate is 1~25℃ / min; the melting temperature is 300~450℃; During the pressure holding stage, at the melting temperature, the pressure is maintained within a preset pressure range in a stepped manner for a preset duration; the preset pressure range is 0.3~4.2MPa; the preset duration is 5~300 minutes; and the stepped pressure range is 1.0~1.7MPa. During the cooling phase, under the second preset pressure, the temperature is cooled to a preset temperature at a preset cooling rate; the cooling rate is 1~34℃ / min; and the preset temperature is 10~300℃.

2. The method for preparing the thermoplastic composite material according to claim 1, characterized in that, The step of maintaining a preset pressure for a preset duration within a preset pressure range at the melting temperature includes: In the first stage, the pressure is maintained at a first preset pressure for a first preset duration; in the second stage, the pressure is maintained at a second preset pressure for a second preset duration; the first preset pressure is 0.3~1.8MPa; the first preset duration is 5~80 minutes; the second preset pressure is 1.1~4.2MPa; the second preset duration is 50~300 minutes.

3. The method for preparing the thermoplastic composite material according to claim 1, characterized in that, When the preforming process is performed n times, the melting temperature of the nth time is less than the melting temperature of the (n-1)th time; n is greater than or equal to 2.

4. The method for preparing the thermoplastic composite material according to claim 3, characterized in that, When the preforming process is executed twice. The melting temperature of the second preforming process is lower than the melting temperature of the first preforming process; and / or The preset temperature range for the first preforming process is 200~250℃; the preset temperature range for the second preforming process is 10~35℃.

5. The method for preparing the thermoplastic composite material according to claim 1, characterized in that, The preform material includes carbon fiber reinforced thermoplastic resin prepreg or a composition of carbon fiber fabric and thermoplastic resin powder.

6. The method for preparing the thermoplastic composite material according to claim 5, characterized in that, When the preform is a carbon fiber reinforced thermoplastic resin prepreg, the mass content of the resin in the carbon fiber reinforced thermoplastic resin prepreg is 25.3%~43.6%; the volume content of the carbon fiber is 47.2%~78.5%; and the thickness of the preform is 0.08~0.21 mm. When the preform material is a composition of carbon fiber fabric and thermoplastic resin powder, the areal density of the carbon fiber fabric is 128~284 g / m³. 2 .

7. The method for preparing the thermoplastic composite material according to any one of claims 1-6, characterized in that, The preparation method further includes: The material is heated to the molding temperature at a second heating rate and then molded at the molding temperature to form the thermoplastic composite material; the second heating rate is 3~26℃ / min; the molding temperature is 340~390℃.

8. The method for preparing the thermoplastic composite material according to claim 7, characterized in that, Before heating to the molding temperature at a second heating rate and molding the preform at the molding temperature to form the thermoplastic composite material, the preparation method further includes: The blank is transferred to the forming mold at a speed less than the preset transfer time, which is 18 seconds.

9. A thermoplastic composite material, characterized in that, The thermoplastic composite material is prepared by the method of preparing thermoplastic composite material according to any one of claims 1 to 8, wherein the porosity of the thermoplastic composite material is less than 2.0% and the interlaminar shear strength is ≥80MPa.

10. The application of the thermoplastic composite material prepared by the method of any one of claims 1-8 and / or the thermoplastic composite material of claim 9 in aerospace structural components.

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