Carbon fiber thermoplastic composite material and preparation method thereof

Abstract

The invention relates to the technical field of carbon fiber reinforced thermoplastic composite materials, in particular to a carbon fiber thermoplastic composite material and a preparation method thereof. The method comprises the following steps: carrying out liquid-phase oxidation treatment on carbon fibers to improve the surface roughness of the carbon fibers and introducing oxygen-containing functional groups; the carbon fibers subjected to liquid phase oxidation treatment and a blend of a high-heat-resistance liquid crystal polymer / low-melting-point polyether-ether-ketone are impregnated, compounded and formed in a molten state, wherein the liquid crystal polymer is oriented in the melting flow process and forms a microfiber structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon fiber reinforced thermoplastic composites, in particular to a carbon fiber thermoplastic composite material and a preparation method thereof. BACKGROUND

[0002] In recent years, with the continuous progress of science and technology, the low-altitude economy is showing a burst of growth trend. Since 2024, more than 60% of provinces in China have laid out low-altitude economic industries. Thermoplastic composites are key basic materials to support the development of low-altitude economy. In-depth development of thermoplastic composites is of great significance to promote the scale expansion of low-altitude economy. Among them, the prepreg tape and composite profile with carbon fiber as the reinforcing body and polyether ether ketone (PEEK) resin as the matrix have been widely used in aerospace, flying cars and other core fields of low-altitude economy. At present, carbon fiber / PEEK prepreg tape and its composite profile are the mainstream products of thermoplastic composites, which is due to the high strength and high modulus performance of carbon fiber and the heat and corrosion resistance of PEEK. However, the carbon fiber / PEEK composite material prepared by the existing technology still has common shortcomings: first, the strength retention rate of carbon fiber yarn is low, and second, the interfacial bonding performance between the fiber and the resin is poor.

[0003] CN 119553504 A discloses a method for improving the interfacial bonding strength between carbon fiber and PEEK resin. The method mainly uses carbon fiber, including: desizing and activating the carbon fiber fabric; then soaking in a PEI aqueous solution for modification; after soaking, soaking in a MXene suspension for a second time; finally, soaking the carbon fiber treated by the above steps in a dispersion liquid of CB (conductive carbon black) and PEI for a third time; and finally preparing a carbon fiber thermoplastic composite material by a film lamination method. This method needs multiple soaking steps, which is complex, cumbersome, time-consuming, high-cost, difficult to industrialize, and has serious nanoparticle agglomeration. After optimization, the interlaminar shear strength of the material is only 67.1 MPa, and the interfacial bonding performance between the fiber and the resin is still poor.

[0004] CN 113501982 A discloses a method for improving the interfacial bonding strength of carbon fiber reinforced PEEK composite material, which comprises: heat-oxidizing the surface of carbon fiber without sizing agent; then reacting the carbon fiber with dichloro sulfide to prepare acyl chloride carbon fiber; finally blending the acyl chloride carbon fiber with PEEK and hot-pressing to form carbon fiber reinforced PEEK composite material. This method has strict requirements on raw materials, requiring yarns without sizing agent, while carbon fibers in the prior art generally have sizing agent. Secondly, dichloro sulfide is used as an acyl chloride reaction reagent, which has corrosion and pollution problems, and poor environmental protection. In addition, the dichloro sulfide waste gas generated during molding needs harmless treatment, resulting in complex process flow and increased production cost. After optimization, the highest bending strength of the material is 805.9 MPa, and the interlaminar shear strength is 99.6 MPa. Although the interfacial bonding effect between the fiber and the resin is improved, the yarn strength retention rate is poor. SUMMARY

[0005] The present application encompasses the following technical solutions:

[0006] One aspect of the present application relates to a method for preparing a carbon fiber thermoplastic composite material, which comprises the following steps:

[0007] Liquid phase oxidation treatment is performed on the carbon fiber to increase its surface roughness and introduce oxygen-containing functional groups;

[0008] The carbon fiber treated by liquid phase oxidation is impregnated and compounded with a blend of high-heat-resistant liquid crystal polymer and low-melting-point polyether ether ketone in a molten state, and then formed, wherein the liquid crystal polymer is oriented and forms a micro-fiber structure during the molten flow process.

[0009] Another aspect of the present application relates to a carbon fiber thermoplastic composite material prepared by the method described above.

[0010] Still another aspect of the present application relates to a load-bearing component comprising the carbon fiber thermoplastic composite material described above.

[0011] The present application performs mild and controllable liquid phase oxidation treatment on carbon fiber, and introduces the orientation of high-heat-resistant liquid crystal polymer and the in-situ micro-fiber structure formation mechanism during the molten impregnation forming process, so as to build a continuous structure transition layer between the carbon fiber and the low-melting-point polyether ether ketone matrix in the interfacial region, thereby effectively relieving the modulus mutation between the high-modulus carbon fiber and the low-modulus thermoplastic resin and the stress concentration problem caused thereby, significantly improving the interfacial bonding stability and energy dissipation capacity without significantly damaging the mechanical properties of the carbon fiber. The carbon fiber thermoplastic composite material prepared in this way has high yarn strength retention rate, excellent interlaminar shear performance and good structural reliability, and can meet the application requirements of load-bearing structures with high requirements for lightweight, high damage tolerance and service stability. Attached Figure Description

[0012] 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.

[0013] Figure 1 Diagrams showing the liquid phase oxidation process and interfacial interaction mechanism of carbon fiber tow; (a): liquid phase oxidation process; (b): interfacial interaction mechanism.

[0014] Figure 2 Comparison of carbon fiber tow surface before and after liquid phase oxidation treatment; (a): before treatment; (b): after treatment. Detailed Implementation

[0015] 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.

[0016] 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 polymer materials science, composite materials engineering, materials physics and processing engineering, interface chemistry, and continuous molding processes, 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.

[0017] The terms “containing,” “comprising,” and “including” as used in this invention are synonyms and are inclusive or open-ended, not excluding additional, uncited members, elements, or method steps.

[0018] 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.

[0019] 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.

[0020] This invention relates to concentration values, which include fluctuations within a certain range. For example, fluctuations are allowed within a corresponding precision range. For instance, 2% can fluctuate within ±0.1%. For larger values ​​or values ​​that do not require overly precise control, even greater fluctuations are permitted.

[0021] As used in this invention, unless otherwise stated, the singular forms of the articles “a,” “an,” and “the” include plural referents.

[0022] In this invention, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity of 2 or more.

[0023] 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.

[0024] In this invention, terms such as "preferred," "better," "more suitable," and "ideal" are merely descriptions of more effective implementation methods or embodiments, 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.

[0025] In this invention, "high heat-resistant liquid crystal polymer" refers to a class of thermotropic liquid crystal polymers that, compared to the low-melting-point polyether ether ketone (PEEK) used in this invention, possess higher heat resistance and thermodeformation capability. These liquid crystal polymers maintain a rigid rod-shaped molecular backbone structure in the molten state and can undergo orientation under the influence of an applied flow field. Specifically, the high heat-resistant liquid crystal polymer can maintain its liquid crystal phase characteristics within the melt processing temperature range of the low-melting-point PEEK without significant softening, melt disorder, or thermal degradation, thus exhibiting structural stability different from that of the matrix resin in the blend system. Based on the aforementioned relative heat resistance characteristics, the high heat-resistant liquid crystal polymer has the ability to spontaneously orient along the flow direction during melt flow and can form oriented or fibrous structures in the low-melting-point PEEK matrix, providing a molecular basis for structural transitions in the interfacial regions. This invention does not limit the specific chemical composition or commercial model of the high heat-resistant liquid crystal polymer; any polymer possessing the aforementioned heat resistance stability and orientation behavior characteristics relative to the low-melting-point PEEK is applicable to this invention.

[0026] In this invention, "microfiber structure" refers to a slender, fibrous phase structure formed in situ under shear force and / or tensile flow field when a liquid crystal polymer is blended with a low-melting-point polyetheretherketone (PEEK) and in a molten flow state. This structure exhibits an oriented distribution along the main flow direction and is distinct from spherical or irregularly dispersed phases. The microfiber structure typically has a high aspect ratio, with characteristic dimensions reaching the micrometer or submicrometer scale. It can form a continuous or semi-continuous intermediate phase structure between the carbon fiber and the thermoplastic resin matrix, thereby achieving structural transition at the interface. It should be understood that the specific morphology and size of the microfiber structure may vary depending on processing conditions, but as long as it meets the above-mentioned in-situ formation and fibrous orientation characteristics, it falls within the scope of the microfiber structure described in this invention.

[0027] In this invention, "traction effect" refers to the axial tensile force applied to the molten impregnated carbon fibers by a winding device or traction device during the continuous molding process of carbon fiber thermoplastic composites. This force causes the carbon fibers and the molten resin system they carry to move stably along the fiber axis, forming a directional tensile flow state within the impregnation mold or molding area. The traction effect not only enables continuous material transport but also works synergistically with the flow behavior of the molten resin to provide the necessary flow field conditions for the liquid crystal polymer to orient and form an oriented structure during the molten flow process. The specific implementation of the traction effect in this invention is not limited to a specific equipment form; any method that can produce the aforementioned axial tensile flow effect during the molding process should be considered as a traction effect under the meaning of this invention.

[0028] In this invention, "liquid-phase oxidation treatment" refers to a method of modifying the surface of carbon fibers by placing them in a liquid oxidation medium and performing a chemical oxidation reaction. This treatment method can improve the micro-roughness of the carbon fiber surface and introduce oxygen-containing functional groups onto the surface without significantly damaging the mechanical properties of the carbon fiber itself. The liquid-phase oxidation treatment is typically carried out under controlled temperature, time, and reaction conditions to induce a limited degree of oxidation reaction on the carbon fiber surface, thereby improving the interfacial wettability and bonding ability between the carbon fiber and the thermoplastic resin. The liquid-phase oxidation treatment described in this invention is not limited to a specific reaction path or process parameters; any treatment that achieves the aforementioned surface modification effect can be considered liquid-phase oxidation treatment in the sense of this invention.

[0029] In this invention, the "alkaline peroxidation system" refers to a liquid-phase oxidation system formed by introducing peroxides as oxidants under alkaline conditions. This system can perform oxidative modification on the carbon fiber surface under relatively mild reaction conditions. The alkaline peroxidation system adjusts the pH value of the reaction system through alkaline components, enabling the peroxides to have suitable reactivity within the system. This allows oxygen-containing functional groups such as hydroxyl, carboxyl, and carbonyl groups to be generated on the carbon fiber surface, while simultaneously avoiding fiber structure damage caused by excessive oxidation.

[0030] In this invention, "low-melting-point polyetheretherketone" refers to a polyetheretherketone thermoplastic resin with a lower melting temperature or more suitable melt processing characteristics compared to conventional polyetheretherketone. This type of resin can achieve full melting at lower processing temperatures and has good fluidity, which is beneficial for impregnating and coating carbon fibers. While maintaining the inherent heat resistance, mechanical properties, and chemical stability of polyetheretherketone materials, the low-melting-point polyetheretherketone can form a stable blend system with high-heat-resistant liquid crystal polymers and provide a continuous matrix environment for the orientation and structure formation of the liquid crystal polymers during melt processing.

[0031] This invention provides a method for preparing carbon fiber thermoplastic composite material, which includes the following steps:

[0032] Liquid phase oxidation treatment is applied to carbon fibers to improve their surface roughness and introduce oxygen-containing functional groups;

[0033] Carbon fibers treated with liquid phase oxidation are impregnated and compounded with a blend of high heat-resistant liquid crystal polymer / low melting point polyether ether ketone in a molten state and then molded, wherein the liquid crystal polymer is oriented and forms a microfiber structure during the molten flow process.

[0034] The above preparation method allows the surface functional group effect introduced by liquid phase oxidation treatment to work in conjunction with the oriented microfiber structure formed by the liquid crystal polymer in the melt flow, thereby achieving effective control of the carbon fiber / thermoplastic resin interface structure at the interface scale. This results in a carbon fiber thermoplastic composite material with stable interfacial bonding and good structural continuity without relying on additional solvents or complex chemical grafting reactions, providing a reliable process basis for obtaining composite materials with both high yarn strength retention and excellent interlayer properties.

[0035] In some embodiments, the impregnation, compounding, and molding process in the molten state is carried out under traction, causing the carbon fiber and the liquid crystal polymer / low-melting-point polyether ether ketone blend to synergistically orient in the flow direction. By applying stable traction to the carbon fiber during continuous molding, the carbon fiber, after liquid-phase oxidation treatment, remains axially straight in the molten resin system, and promotes the formation of a directional flow field in the high-heat-resistant liquid crystal polymer / low-melting-point polyether ether ketone blend during impregnation and flow. Under the action of this flow field, the axial orientation of the carbon fiber is consistent with the main flow direction of the molten resin system, thereby causing the liquid crystal polymer to orient during the molten flow process and forming a synergistic relationship with the carbon fiber orientation direction, which is beneficial to the stable formation of the oriented structure.

[0036] Furthermore, the traction effect can be applied by a take-up roller during the continuous molding process. In the actual molding process, the take-up roller applies axial traction tension to the carbon fibers after molten impregnation, causing the carbon fibers and the high heat-resistant liquid crystal polymer / low melting point polyether ether ketone blend they carry to move continuously along the fiber axis within the impregnation mold, thereby forming a flow state dominated by axial tension in the molding area. This tensile flow state can cooperate with the shear flow in the molten system, providing stable flow conditions for the liquid crystal polymer to orient and maintain its oriented structure in the molten state, thus facilitating the obtaining of a structurally uniform and orientation-stable interface region in the composite material.

[0037] In some embodiments, the characteristic size of the microfiber structure is submicron. This microfiber structure is a slender fibrous phase formed during melt impregnation and molding when the liquid crystal polymer is oriented and stretched in situ under the influence of a flow field. Its size is significantly smaller than the macroscopic fibers or phase-separated structures formed in conventional composite materials. By controlling the characteristic size of the microfiber structure within the submicron range, the oriented structure can form a more uniformly distributed and continuous intermediate phase region between the carbon fiber and the low-melting-point polyetheretherketone matrix. This avoids significant structural abrupt changes at the interface, resulting in a smoother stress transfer characteristic in the interface region during mechanical response, which is beneficial for maintaining the overall stability of the composite material structure.

[0038] In some embodiments, the amount of the high heat-resistant liquid crystal polymer in the blend is 5 wt% to 12 wt% of the mass of the low-melting-point polyetheretherketone, for example, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or 11 wt%. By controlling the amount of the high heat-resistant liquid crystal polymer within the above range, good processing performance can be ensured while facilitating the formation and maintenance of the microfiber structure, thereby providing conditions for obtaining carbon fiber thermoplastic composite materials with uniform structure and stable interface.

[0039] In some embodiments, the liquid-phase oxidation treatment is carried out using an alkaline peroxidation system. By introducing the peroxidation reaction system under alkaline conditions, limited oxidation of the carbon fiber surface can be achieved in a relatively mild and controllable environment, resulting in a controlled reaction on the carbon fiber surface. This improves its micro-roughness and introduces oxygen-containing functional groups, while avoiding adverse effects on the carbon fiber's main structure and mechanical properties due to excessive reaction. This alkaline peroxidation system is suitable for continuous processing, ensuring processing uniformity while providing a stable reinforcing material for the subsequent melt impregnation composite process.

[0040] Furthermore, the alkaline peroxidation system can be composed of ammonia, hydrogen peroxide, and deionized water. Ammonia is used to adjust the alkaline environment of the reaction system, hydrogen peroxide acts as an oxidant providing suitable oxidation activity under alkaline conditions, and deionized water serves as a reaction medium to regulate the system concentration and reaction rate. In one specific embodiment, the volume ratio of ammonia, 30% hydrogen peroxide, and deionized water in the mixed solution can be 1.5:2:6.5. By using the above-mentioned alkaline peroxidation system, while ensuring a mild and controllable oxidation reaction, oxygen-containing functional groups such as hydroxyl, carboxyl, or carbonyl groups can be uniformly introduced onto the carbon fiber surface. This is beneficial for improving the wettability and interfacial interaction stability of the carbon fiber and the high-heat-resistant liquid crystal polymer / low-melting-point polyetheretherketone blend system during melt impregnation.

[0041] In some embodiments of the present invention, the liquid-phase oxidation treatment can be performed under ultrasonic-assisted conditions. By introducing ultrasound into the liquid-phase oxidation system, the renewal and diffusion of the reaction solution on the carbon fiber surface can be promoted, allowing the oxidation medium to contact the carbon fiber surface more fully, thereby improving the uniformity and controllability of the surface modification treatment. Ultrasonic assistance helps to reduce the problem of excessive local reaction or uneven treatment, making the carbon fiber surface oxidation process more gentle and stable, and helping to achieve synergistic control of surface roughness and oxygen-containing functional group content without significantly damaging the carbon fiber structure. In an exemplary embodiment, the liquid-phase oxidation treatment time can be 15–25 min, the treatment temperature can be controlled at 42–53 °C, and the ultrasonic vibration frequency can be 57–91 kHz.

[0042] In some embodiments, the volume ratio of the carbon fiber treated with liquid phase oxidation to the low-melting-point polyether ether ketone is 6-8:2-4.

[0043] The present invention also relates to carbon fiber thermoplastic composite materials prepared by the preparation method described above.

[0044] The present invention also relates to a load-bearing member comprising the carbon fiber thermoplastic composite material as described above.

[0045] The load-bearing components may include, but are not limited to, beams, plates, shells, stiffeners, frame components, or combinations thereof. The carbon fiber thermoplastic composite material typically constitutes the main material or primary load-bearing layer of the load-bearing component, accounting for more than 50% of the total volume of the component, preferably 60%–90%, to fully utilize the load-bearing capacity of the carbon fiber reinforcement phase. In this application, the carbon fibers are continuously distributed along the main stress direction of the component. The oriented microfiber structure formed by the low-melting-point polyetheretherketone matrix and the liquid crystal polymer synergistically constructs a stable interface, enabling the load to be uniformly transferred between the fibers and the matrix, thereby improving the structural stability of the load-bearing component under tensile, bending, or shear loads.

[0046] Furthermore, the load-bearing component may optionally be an aircraft structural component, preferably applicable to the structural systems of low-altitude aircraft, unmanned aerial vehicles, flying cars, or other aircraft. For example, the aircraft structural component may include fuselage skin, load-bearing beams, longitudinal beams, frames, reinforcing ribs, cabin shells, or combinations thereof. In the above structural components, the carbon fiber thermoplastic composite material of the present invention can be used as the main load-bearing material or a local reinforcing material. When used as the main load-bearing material, it can form the overall laminated body of the structural component; when used as a local reinforcing material, it can be arranged in areas of high stress concentration or critical stress paths. Because the composite material of the present invention forms a structurally continuous intermediate phase in the fiber-matrix interface region, it can effectively alleviate the interface stress concentration caused by the abrupt change in modulus. Therefore, during the service of the aircraft structural component, it is beneficial to improve its fatigue resistance, impact resistance, and damage tolerance, thereby improving the overall safety and service reliability of the structural component while meeting the requirements for lightweighting.

[0047] This invention proposes a method for preparing carbon fibers using liquid-phase oxidation. This treatment increases the micro-roughness of the carbon fiber surface, expands the contact area with the resin, and enriches surface functional groups without significantly damaging the mechanical properties of the carbon fiber, thereby strengthening the interfacial bonding between the carbon fiber and the resin. Furthermore, when high-heat-resistant liquid crystal polymer (LCP) is blended with low-melting-point polyether ether ketone (LMPEEK), the molten high-heat-resistant LCP exhibits a rigid rod-like structure. Under shear or tensile flow, it spontaneously and highly oriented along the flow direction, forming a sub-micron diameter in-situ microfiber network. This network can synergistically work with the axial orientation of the carbon fiber to reduce yarn buckling and twisting. Simultaneously, high-heat-resistant LCP and LMPEEK can achieve molecular-level interfacial bonding through π-π electron stacking, forming a modulus transition zone of "carbon fiber / LCP microfiber network / LMPEEK" during the melting process. This effectively alleviates interfacial stress concentration under external force, further improving interfacial bonding performance. In summary, compared with the prior art, the preparation method of the present invention does not require the use of solutions or organic solvents, which is more environmentally friendly. At the same time, it has the characteristics of strong process operability, excellent product stability, low process cost, and high cost performance of raw materials.

[0048] 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.

[0049] Example

[0050] This embodiment combines Figure 1 Describe it.

[0051] (1) Liquid phase oxidation treatment of carbon fiber surface: The carbon fiber is first introduced into an alkaline peroxidation solution bath via guide rollers 1-8 for ultrasonic constant temperature surface treatment. The rotation speed of guide rollers 1-8 is 10-30 rpm. The alkaline peroxidation solution is a mixed solution of ammonia, 30% H2O2 and deionized water. The ratio of ammonia:30% H2O2:deionized water is 1.5:2:6.5. The constant temperature oxidation time is 15-25 min. The water temperature of the solution bath is controlled at 42-53℃. The ultrasonic vibration frequency is 57-91 kHz. After ultrasonic constant temperature surface treatment, the carbon fiber is introduced into a deionized water bath via guide rollers 1-3 for constant temperature water washing until the pH of the washing solution is neutral. The rotation speed of guide rollers 1-3 is 10-30 rpm. The water temperature of the deionized water bath is controlled at 55-60℃. Finally, the washed carbon fiber is collected by collecting roller 4 to obtain carbon fiber with surface roughening and increased functional groups. The rotation speed of collecting roller 4 is 10-30 rpm.

[0052] (2) Preparation of liquid crystal polymer (LCP) / LMPEEK blend: The high heat-resistant liquid crystal polymer with a particle size of 18-25μm and the LMPEEK powder with a particle size of 16-20μm are mixed evenly by a dry powder mixer and stirred at 20-25℃ and 3000-4000 rpm for 0.5-2h to ensure that the LCP powder and LMPEEK powder are fully mixed to obtain the LCP / LMPEEK blend; the amount of LCP powder is 5wt%-12wt% of the mass of LMPEEK powder.

[0053] (3) Preparation of carbon fiber thermoplastic composite material with modulus gradient effect: The carbon fiber tow treated by liquid phase oxidation in step 1) is dried at 80-90℃ for 5-7 min; the LCP / LMPEEK blend obtained in step 2) is preheated in a twin-screw extruder; the dried carbon fiber yarn is pre-spread and spread, and then passed through an incineration oven, a twin-screw extruder, an impregnation die, and a cooling calendering roller under the traction of the take-up roller to complete the prepreg tape winding. Finally, it is formed into a carbon fiber thermoplastic composite material with modulus gradient effect by hot stamping process. The preheating time of LCP / LMPEEK blend is 30-50 min, the oscillation frequency of the spreading device is 25-40 Hz, and the tension of the take-up roller is 25-40 Hz. The incineration oven temperature is 240-280℃. The temperature control zones of the twin-screw extruder are set as follows: Zone 1: 310-330℃; Zone 2: 310-330℃; Zone 3: 320-345℃; Zone 4: 340-350℃. The melt pressure in the impregnation die is maintained at 0.5-1.5 MPa. The cooling calender roller temperature is 110-130℃, and the pressure is set at 1-2 MPa. The winding roller traction speed is 1.2-2 m / min. In step 3), the volume ratio of carbon fiber to LMPEEK resin is 6~8:2~4.

[0054] Comparative Example 1 (no fiber treatment and no LCP added)

[0055] (1) Carbon fiber is not treated in any way.

[0056] (2) Preparation of carbon fiber thermoplastic composite material: The carbon fiber bundle from step 1) is dried at 80-90℃ for 5-7 min; LMPEEK is preheated in a twin-screw extruder; the dried carbon fiber yarn is pre-spread and then spread, and then passed through an incineration oven, a twin-screw extruder, an impregnation die, and a cooling calendering roller under the traction of the take-up roller to complete the prepreg tape winding. Finally, it is formed into a carbon fiber thermoplastic composite material with modulus gradient effect by hot stamping process. The preheating time of LMPEEK is 30-50 min, the oscillation frequency of the spreading device is 25-40 Hz, and the tension of the take-up roller is 25-40 Hz. The incineration oven temperature is 240-280℃. The temperature control zones of the twin-screw extruder are set as follows: Zone 1: 310-330℃; Zone 2: 310-330℃; Zone 3: 320-345℃; Zone 4: 340-350℃. The melt pressure in the impregnation die is maintained at 0.5-1.5 MPa. The cooling calender roller temperature is 110-130℃, and the pressure is set at 1-2 MPa. The winding roller traction speed is 1.2-2 m / min. The volume ratio of carbon fiber to LMPEEK resin is 6~8:2~4.

[0057] Comparative Example 2 (Liquid-phase treated carbon fiber, without LCP)

[0058] (1) Liquid phase oxidation treatment of carbon fiber surface: The carbon fiber is first introduced into an alkaline peroxidation solution bath via guide rollers 1-8 for ultrasonic constant temperature surface treatment. The rotation speed of guide rollers 1-8 is 10-30 rpm. The alkaline peroxidation solution is a mixed solution of ammonia, 30% H2O2 and deionized water. The ratio of ammonia:30% H2O2:deionized water is 1.5:2:6.5. The constant temperature oxidation time is 15-25 min. The water temperature of the solution bath is controlled at 42-53℃. The ultrasonic vibration frequency is 57-91 kHz. After ultrasonic constant temperature surface treatment, the carbon fiber is introduced into a deionized water bath via guide rollers 1-3 for constant temperature water washing until the pH of the washing solution is neutral. The rotation speed of guide rollers 1-3 is 10-30 rpm. The water temperature of the deionized water bath is controlled at 55-60℃. Finally, the washed carbon fiber is collected by collecting roller 4 to obtain carbon fiber with surface roughening and increased functional groups. The rotation speed of collecting roller 4 is 10-30 rpm.

[0059] (2) Preparation of carbon fiber thermoplastic composite material: The carbon fiber tow treated by liquid phase oxidation in step 1) is dried at 80-90℃ for 5-7 min; LMPEEK is preheated in a twin-screw extruder; the dried carbon fiber yarn is pre-spread and spread, and then passed through an incineration oven, twin-screw extruder, impregnation die, and cooling calendering roller under the traction of the take-up roller to complete the prepreg tape winding. Finally, it is formed into a carbon fiber thermoplastic composite material with modulus gradient effect by hot stamping process. The preheating time of LMPEEK is 30-50 min, the oscillation frequency of the spreading device is 25-40 Hz, and the tension of the take-up roller is 25-40 Hz. The carbon fiber to LMPEEK resin volume ratio is 6~8:2~4. The incineration oven temperature is 240-280℃. The twin-screw extruder temperature control zones are set as follows: Zone 1: 310-330℃; Zone 2: 310-330℃; Zone 3: 320-345℃; Zone 4: 340-350℃. The melt pressure in the impregnation die is maintained at 0.5-1.5 MPa. The cooling calender roller temperature is 110-130℃, and the pressure is set at 1-2 MPa. The winding roller traction speed is 1.2-2 m / min.

[0060] Comparative Example 3 (no carbon fiber treatment, but LCP added)

[0061] (1) Carbon fiber is not treated in any way.

[0062] (2) Preparation of liquid crystal polymer (LCP) / LMPEEK blend: The high heat-resistant liquid crystal polymer with a particle size of 18-25μm and the LMPEEK powder with a particle size of 16-20μm are mixed evenly by a dry powder mixer and stirred at 20-25℃ and 3000-4000 rpm for 0.5-2h to ensure that the LCP powder and LMPEEK powder are fully mixed to obtain the LCP / LMPEEK blend; the amount of LCP powder is 5wt%-12wt% of the mass of LMPEEK powder.

[0063] (3) Preparation of carbon fiber thermoplastic composite material with modulus gradient effect: The carbon fiber tow treated by liquid phase oxidation in step 1) is dried at 80-90℃ for 5-7 min; the LCP / LMPEEK blend obtained in step 2) is preheated in a twin-screw extruder; the dried carbon fiber yarn is pre-spread and spread, and then passed through an incineration oven, a twin-screw extruder, an impregnation die, and a cooling calendering roller under the traction of the take-up roller to complete the prepreg tape winding. Finally, it is formed into a carbon fiber thermoplastic composite material with modulus gradient effect by hot stamping process. The preheating time of LCP / LMPEEK blend is 30-50 min, the oscillation frequency of the spreading device is 25-40 Hz, and the tension of the take-up roller is 25-40 Hz. The carbon fiber to LMPEEK resin volume ratio is 6~8:2~4. The incineration oven temperature is 240-280℃. The twin-screw extruder temperature control zones are set as follows: Zone 1: 310-330℃; Zone 2: 310-330℃; Zone 3: 320-345℃; Zone 4: 340-350℃. The melt pressure in the impregnation die is maintained at 0.5-1.5 MPa. The cooling calender roller temperature is 110-130℃, and the pressure is set at 1-2 MPa. The winding roller traction speed is 1.2-2 m / min.

[0064] Material properties of the above embodiments and comparative examples

[0065]

[0066] The mechanical property tests of all materials listed in the table were completed under the same test conditions. The interlaminar shear strength was determined according to the relevant national standards for interlaminar shear performance testing of composite materials, and the tensile strength was determined according to the national standards for tensile performance testing of carbon fiber reinforced composite materials. Dynamic mechanical property parameters such as loss tangent were obtained using dynamic mechanical analysis methods under uniform test modes and temperature conditions.

[0067] To ensure the comparability of data across different technical approaches, the samples used in the examples and comparative examples maintained consistency in material ratios, molding methods, sample sizes, and testing environments. Differences only existed in key technical features such as whether liquid-phase oxidation treatment was performed and whether high-heat-resistant liquid crystal polymers were introduced. Each set of performance data was derived from the statistical average of multiple repeated test results. Each test was conducted at least three times independently, and the average value was used to characterize the corresponding material properties. This ensured that the test results had good repeatability and representativeness, thus accurately reflecting the impact of different preparation methods on the properties of carbon fiber thermoplastic composites.

[0068] Taking domestically produced T700 carbon fiber as an example, the tensile strength is 4900MPa. The carbon fiber accounts for 60% of the measured material, so the equivalent initial strength of the yarn is uniformly 2940MPa.

[0069] Among them, the yarn strength retention rate = (tensile strength / equivalent initial strength) × 100%.

[0070] Comparative analysis of the mechanical properties of the carbon fiber thermoplastic composites obtained in the Examples and Comparative Examples 1, 2, and 3 shows that the technical solution adopted in this invention achieves a synergistic optimization effect that is difficult to achieve simultaneously in terms of interfacial bonding performance and yarn strength retention rate. Specifically, under the condition of simultaneously employing liquid-phase oxidation treatment and introducing a high heat-resistant liquid crystal polymer, the interlaminar shear strength of the Examples is significantly higher than that of Comparative Example 1 (no carbon fiber treatment and no liquid crystal polymer introduction), Comparative Example 2 (only liquid-phase oxidation treatment of carbon fiber but no liquid crystal polymer introduction), and Comparative Example 3 (no carbon fiber treatment but liquid crystal polymer introduction). This indicates that the technical solution of this invention can form a more stable and effective interfacial bonding structure between carbon fiber and low-melting-point polyetheretherketone matrix.

[0071] Further analysis of tensile strength and yarn strength retention data reveals that while Comparative Example 2 improved the carbon fiber surface condition through liquid-phase oxidation, the lack of a structurally continuous transition layer at the interface resulted in a significantly lower yarn strength retention rate compared to the Example. This indicates that relying solely on surface oxidation can easily introduce fiber damage or stress concentration issues while enhancing interfacial bonding. Comparative Example 3, by introducing a liquid crystal polymer without treating the carbon fiber surface, improved the overall material properties to some extent. However, due to insufficient wettability between the carbon fiber and the resin matrix, the oriented structure formed by the liquid crystal polymer was difficult to stably distribute in the interfacial region, resulting in lower interlayer shear strength and yarn strength retention rates compared to the Example. This demonstrates that a single resin modification method cannot simultaneously achieve interfacial reinforcement and fiber strength maintenance. In contrast, the Example significantly outperformed the Comparative Examples in both indicators, indicating that the synergistic effect of liquid-phase oxidation and the formation mechanism of the oriented microfiber structure by the liquid crystal polymer can effectively suppress fiber strength loss while enhancing interfacial bonding.

[0072] Furthermore, the comparison of dynamic mechanical properties such as loss tangent shows that, while maintaining a high stiffness level, the loss tangent of the embodiment is higher than that of Comparative Example 1 and Comparative Example 2, and significantly different from Comparative Example 3. This indicates that the interface structure formed in the embodiment can not only effectively transfer loads but also has stronger energy dissipation capabilities. This result further confirms that, in the embodiment, the oriented microfiber structure formed by the high heat-resistant liquid crystal polymer during the melt flow process, in conjunction with the carbon fiber surface after liquid-phase oxidation treatment, constructs a structurally continuous and scale-gradually varying mesophase in the interface region, thereby effectively mitigating the modulus abrupt change between high-modulus carbon fibers and low-modulus thermoplastic resin. A comprehensive comparison of the performance of the above embodiments and comparative examples confirms that the present invention does not achieve performance improvement through simple superposition of fiber surface treatments or resin system modification, but rather forms a new synergistic mechanism at the interface structure level. Therefore, it exhibits significantly better performance than existing technologies in terms of interface bonding performance, yarn strength retention rate, and overall mechanical properties, demonstrating outstanding substantive features and significant progress.

[0073] The above data combination shows that the embodiment forms a modulus gradient transition region with energy dissipation capability at the fiber-matrix interface. This transition region effectively alleviates stress concentration caused by abrupt changes in modulus and achieves synergistic optimization of interface reinforcement and fiber strength retention.

[0074] 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 method for preparing a carbon fiber thermoplastic composite material, characterized in that, Includes the following steps: Liquid phase oxidation treatment is applied to carbon fibers to improve their surface roughness and introduce oxygen-containing functional groups; Carbon fibers treated with liquid phase oxidation are impregnated and compounded with a blend of high heat-resistant liquid crystal polymer / low melting point polyether ether ketone in a molten state and then molded, wherein the liquid crystal polymer is oriented and forms a microfiber structure during the molten flow process.

2. The preparation method according to claim 1, characterized in that, The impregnation, composite and molding process in the molten state is carried out under traction, causing the carbon fiber and the liquid crystal polymer / low melting point polyether ether ketone blend to undergo synergistic orientation in the flow direction.

3. The preparation method according to claim 2, characterized in that, The traction is applied by the take-up rollers during the continuous forming process.

4. The preparation method according to claim 1, characterized in that, The characteristic size of the microfiber structure is in the submicron range.

5. The preparation method according to claim 1, characterized in that, The amount of the high heat-resistant liquid crystal polymer in the blend is 5 wt% to 12 wt% of the mass of the low melting point polyether ether ketone.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The liquid-phase oxidation treatment is carried out using an alkaline peroxidation system.

7. The preparation method according to claim 6, characterized in that, The alkaline peroxidation system is a mixed solution composed of ammonia, hydrogen peroxide and water.

8. The preparation method according to any one of claims 1 to 5, characterized in that, The volume ratio of the carbon fiber treated with liquid phase oxidation to the low-melting-point polyether ether ketone is 6-8:2-4.

9. A carbon fiber thermoplastic composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. A load-bearing component, characterized in that, It includes the carbon fiber thermoplastic composite material as described in claim 9; Optionally, the load-bearing component is selected from aircraft structural components.

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