Self-sensing carbon fiber composite material, nanogenerator and preparation method thereof

Abstract

The application discloses a self-sensing carbon fiber composite material, a nanometer generator and a preparation method, relates to the technical field of functional polymer composite materials and nanometer energy material, and comprises a P-TENG obtained by assembling a PENG and a TENG; the preparation method of the PENG is that a pre-oriented PVDF film is subjected to high-pressure annealing treatment, and then electric field polarization is adopted; the applied pressure of the high-pressure heating annealing treatment is 100-500 MPa, and the temperature is 140-200 DEG C; the carbon fiber composite material which is coupled and integrated by a high-orientation pure beta phase PVDF piezoelectric layer and a triboelectric unit is prepared through stretching orientation-high-pressure annealing orientation strengthening-piezoelectricity / triboelectricity synergy for the first time, the integration of structure bearing and high-sensitivity self-powered sensing function is realized, and the problems of orientation attenuation and insufficient piezoelectric response performance of a traditional PVDF piezoelectric layer after heat treatment are solved.

Description

Technical Field

[0001] This invention relates to the field of functional polymer composite materials and nano-energy materials technology, specifically to a self-sensing carbon fiber composite material, a nanogenerator, and its preparation method. Background Technology

[0002] With the in-depth development of aerospace, automotive, and new energy equipment towards lightweight, high reliability, long lifespan, and intelligence, traditional metal structural materials can no longer meet the comprehensive service requirements of high-end equipment under complex working conditions. Carbon fiber reinforced polymer (CFRP) has been widely used in the core load-bearing structures of key industrial equipment such as aircraft, intelligent vehicles, and wind turbine blades due to its ultra-high specific strength, high specific modulus, excellent fatigue resistance, corrosion resistance, and structural designability (Composites Part B: Engineering, 2011, 42 (1): 77-86). However, CFRP is prone to latent damage such as microcracks under long-term alternating loads, vibration and shock, and temperature change cycles. Traditional offline non-destructive testing technologies such as ultrasonic and eddy current testing have the drawbacks of detection lag, low efficiency, and inability to achieve real-time online monitoring across the entire domain.

[0003] Piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs) are two promising types of mechanical energy harvesting and self-sensing devices, showing great application potential in fields such as micro-energy supply, structural self-sensing, and intelligent sensing and monitoring (ACS nano, 2013, 7(11): 9533-9557). However, numerous studies have confirmed that both single PENGs and single TENGs have inherent performance bottlenecks (Nanomaterials, 2023, 13(24): 3170.). Against this backdrop, constructing a piezoelectric-triboelectric hybrid nanogenerator (P-TENG) by coupling the piezoelectric and triboelectric effects can achieve the superposition of electrical signals in the same direction and complementary advantages, effectively overcoming the performance shortcomings of single devices and significantly improving the output performance and environmental adaptability of the device (AdvancedComposites and Hybrid Materials, 2025, 8(2): 225).

[0004] Polyvinylidene fluoride (PVDF) has become the most widely used polymer piezoelectric functional layer material in the PENG field due to its considerable piezoelectric and ferroelectric responses. Semi-crystalline PVDF mainly has three common crystal forms: α, β and γ crystals. Among them, the β phase is in the all-trans conformation (TTTT), exhibiting the strongest piezoelectricity (Thermochimica Acta, 2004, 424, 201-207), and in order to obtain higher electrical output performance, it is made with the highest possible degree of orientation (polymertesting.2006.08.003). However, existing processing methods, such as solution methods for natural film formation, mainly use non-piezoelectric α phase with low β phase content. The commonly used NMP solvent is highly toxic and expensive, posing significant environmental and energy consumption pressures. Even with the addition of conductive fillers, excessive addition will cause a chain of problems such as increased volume conductivity, longitudinal charge leakage, internal short circuit, and decreased piezoelectric voltage, resulting in a decrease in performance instead of an increase (Nanomaterials, 2023,13(24): 3170). Furthermore, the orientation structure is usually obtained through stretching or shear flow field induction (CN118878859A). However, in the subsequent high-temperature heat treatment process, although it helps to improve and rearrange the lamellar structure, it will also cause the molecular chain segment relaxation, which will lead to a decrease in the degree of orientation.

[0005] Meanwhile, the working principle of TENG devices relies on repeated contact-separation and sliding friction. Long-term repetitive mechanical friction can easily cause wear, peeling, and microstructure collapse of the friction layer surface, resulting in a continuous decrease in interface charge density and a gradual decay of electrical output performance. To improve the output performance of TENG, existing studies have mostly used nanofillers such as carbon nanotubes, graphene, MXene, and metal nanoparticles for modification (Micromachines, 2023, 14(6): 1273). However, such modification techniques are highly dependent on high-cost and high-energy-consumption processes such as photolithography, plasma etching, and high-energy ultrasonic dispersion. Not only is the equipment investment large and the preparation process cumbersome, but the use of a large amount of organic solvents will cause environmental pollution, making it difficult to meet the needs of large-scale and green industrial production, which greatly limits the engineering application of nano-power generation self-sensing devices.

[0006] Therefore, traditional structural monitoring methods cannot achieve real-time online health monitoring of carbon fiber composites, and single PENG and TENG devices have inherent performance defects. Based on this, we developed a simple, green, efficient, scalable, and self-sensing carbon fiber composite system. This system, combined with the structural properties of ultra-highly oriented pure β-phase PVDF thin films, forms an integrated piezoelectric-triboelectric coupled self-sensing nanogenerator, effectively overcoming the shortcomings of carbon fiber composites in self-sensing and the performance bottleneck of single devices. Summary of the Invention

[0007] This invention overcomes the shortcomings of existing technologies by proposing a self-sensing carbon fiber composite material, a nanogenerator, and its preparation method. The invention constructs a technical route of "stretching orientation - high-pressure annealing orientation strengthening - piezoelectric / triboelectric synergistic sensitization." High-pressure annealing stabilizes and strengthens the PVDF orientation structure, obtaining an ultra-highly oriented pure β-phase PVDF piezoelectric layer. This layer is further coupled and integrated with triboelectric units into the carbon fiber composite material, achieving a unified structural load-bearing capacity and highly sensitive self-powered sensing, thus solving the problems of orientation attenuation and insufficient piezoelectric response performance of traditional PVDF piezoelectric layers after heat treatment.

[0008] This invention is achieved through the following technical solution: A self-sensing carbon fiber composite material includes assembled PENG and TENG; the PENG is prepared by high-pressure annealing of a pre-oriented PVDF film and then polarizing it by an electric field; the high-pressure annealing is applied at a pressure of 100~500MPa and a temperature of 140~200℃.

[0009] Preferably, TENG is obtained by assembling a PDMS film with a hierarchical micro / nano structure with a copper mesh embedded carbon fiber composite material.

[0010] A method for preparing a self-sensing carbon fiber composite material, wherein PENG is prepared by: melting and extruding PVDF through a single screw extruder, cooling and then stretching the extruded material by rollers to obtain a pre-oriented PVDF film, and then subjecting the pre-oriented PVDF film to high-pressure annealing and electric field polarization treatment. Preparation of TENG: After stacking carbon fiber prepreg with copper mesh, copper mesh embedded carbon fiber composite material is obtained by vacuum bag molding process of prepreg. Then, PDMS film with hierarchical micro-nano structure is assembled with copper mesh embedded carbon fiber composite material to obtain TENG. Then PENG and TENG are assembled to obtain P-TENG.

[0011] Preferably, the processing temperature of the single-screw extruder is 170~220℃, and the screw speed is 60~200r / min.

[0012] Preferably, the temperature of the preheating roller and the stretching roller used in roller stretching forming is 80~100℃, and the speed ratio of the stretching roller to the preheating roller is... R≥ 3.

[0013] Preferably, the polarization temperature is 90~110℃ and the electric field strength is 350~450V / μm.

[0014] Preferably, during high-pressure annealing, the temperature should be maintained at that temperature for 30-40 minutes under pressure, and then cooled to room temperature under pressure for setting.

[0015] Preferably, the method for preparing PDMS thin films with hierarchical micro-nano structures is to mix PDMS and curing agent evenly, then degas the mixture under vacuum, pour the mixture into a petri dish containing sandpaper, cure it at room temperature, and then demold it.

[0016] A nanogenerator includes the aforementioned self-sensing carbon fiber composite material, or is obtained using the aforementioned method for preparing the self-sensing carbon fiber composite material.

[0017] The beneficial effects of this invention compared to the prior art are as follows: 1. This invention integrates a highly oriented pure β-phase PVDF piezoelectric layer with triboelectric units into a carbon fiber composite material system, completely changing the single characteristic of traditional carbon fiber composite materials that only possess structural load-bearing capacity and lack autonomous sensing capabilities. Without the need for external power supply equipment and detection sensors, the composite material can achieve highly sensitive self-powered sensing function while bearing structural loads. This effectively makes up for the shortcomings of traditional structural materials, such as the inability to autonomously monitor working conditions, detection lag, and susceptibility of external detection equipment to environmental interference. It expands the application prospects of such materials and provides a new technical approach for the design of intelligent composite materials.

[0018] 2. This invention employs a high-pressure mold to construct a synergistic system of temperature and pressure fields. Based on the initial orientation achieved through roller stretching, a high-pressure annealing process efficiently induces the transformation of residual nonpolar α-crystals within the PVDF material into polar pure β-crystals. Simultaneously, the pressure stabilizes the conformation of the oriented molecular chains, promoting orderly crystal arrangement and improvement, thereby enhancing the overall orientation degree and β-phase purity of the pre-oriented PVDF film and fundamentally strengthening its piezoelectric response performance. This process overcomes the technical problems of insufficient orientation degree and low β-phase crystal conversion rate in traditional PVDF heat treatment modification, providing a novel process approach and technical reference for the research of high-orientation and high-purity phase modification of polymer piezoelectric materials.

[0019] 3. This invention organically assembles and couples piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs) to construct a P-TENG composite power generation and sensing system. Unlike the shortcomings of single piezoelectric or triboelectric nanogenerators, which have narrow response ranges, limited sensitivity, and single output performance, the two power generation units can achieve complementary functions and synergistic performance gains, significantly improving the electrical response sensitivity and detection range of the composite material. The overall electrical response performance is significantly better than that of traditional single nanogenerator materials, effectively improving the material's ability to dynamically sense and capture weak signals, and adapting to the high-precision self-sensing requirements under complex working conditions. Attached Figure Description

[0020] Figure 1 This is a flowchart and model diagram of the preparation process of the P-TENG structural material of the present invention.

[0021] Figure 2This is a series of comparative images of the PENG section in Example 3 and Comparative Example 1; wherein, (a) two-dimensional wide-angle X-ray diffraction (2D-WAXD) image, (b) one-dimensional wide-angle X-ray diffraction curve (1D-WAXD) image, (c) WAXD azimuth scan image, and (d) Herman orientation factor ( f H (e) Bar chart, (f) Two-dimensional small-angle X-ray scattering (2D-SAXS) image, (g) One-dimensional small-angle X-ray scattering (1D-SAXS) image, (h) Differential scanning calorimetry (DSC) scan image, (f) Piezoelectric coefficient ( d 33 (i) Bar chart, dielectric constant ( ε ′ (j) Spectral image, (j) Dielectric loss (tanδ) spectral image, and a comparison diagram of the response of the PENG part in Example 3 and Comparative Example 1 under an external force of 6N (1Hz); where (k) Voltage response diagram and (l) Current response diagram.

[0022] Figure 3 The response diagrams are for Example 3; (a) voltage response diagram under an external force of 6-36N (1Hz), (b) current response diagram under an external force of 6-36N (1Hz), (c) voltage response diagram under an external force of 1-4Hz (6N), and (d) current response diagram under an external force of 1-4Hz (6N).

[0023] Figure 4 The response diagrams for Comparative Example 3 are shown below; (a) is the voltage response diagram under an external force of 6-36N (1Hz), (b) is the current response diagram under an external force of 6-36N (1Hz), (c) is the voltage response diagram under an external force of 1-4Hz (6N), and (d) is the current response diagram under an external force of 1-4Hz (6N).

[0024] Figure 5 The response diagrams for Comparative Example 4 are shown below; (a) is the voltage response diagram under an external force of 6-36N (1Hz), (b) is the current response diagram under an external force of 6-36N (1Hz), (c) is the voltage response diagram under an external force of 1-4Hz (6N), and (d) is the current response diagram under an external force of 1-4Hz (6N). Detailed Implementation

[0025] To make the technical problems to be solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto.

[0026] The high-pressure mold described in the following embodiments and comparative examples is referred to as follows: Figure 1 As shown, the high-pressure mold includes a pressure plunger, copper blocks, a cavity, a heating jacket, and a thermocouple port. The pressure plunger is divided into upper and lower parts, both of which slide in contact with the cavity. The copper blocks consist of two high-thermal-conductivity copper blocks, one upper and one lower, located within the cavity to clamp the pre-oriented PVDF film, ensuring uniform heating of its upper and lower surfaces. The upper and lower copper blocks respectively contact the upper and lower pressure plungers, applying pressure to the internal pre-oriented PVDF film. The heating jacket is connected to an external heating device and has threaded holes that completely cover the outer surface of the cavity, further secured with bolts to prevent slippage. The thermocouple port is located on the upper surface of the cavity and is inserted during high-pressure annealing to monitor the temperature in real time.

[0027] The high-pressure mold is placed on the mold frame to ensure its smooth operation. These are all routine operating techniques for those skilled in the art and will not be described in detail here. Example 1

[0028] A method for preparing piezoelectric-triboelectric synergistic self-sensing carbon fiber composite (P-TENG) includes the following steps: S1, Polyvinylidene fluoride (PVDF) drying: Select high-purity PVDF powder raw material, spread the PVDF powder evenly on the drying tray, with a thickness not exceeding 5mm, place it in a vacuum drying oven, set the drying temperature to 80℃, and dry at a constant temperature for 12 hours; after drying, take it out, quickly place it in a desiccator to cool naturally to room temperature, seal and store for later use, and prevent secondary moisture absorption.

[0029] S2, Preparation of PVDF precursor film: Dried polyvinylidene fluoride (PVDF) is poured into the hopper of a single-screw extruder. The processing temperature is 210℃, and the screw speed is 100 rpm, allowing the PVDF powder to fully melt, plasticize, and homogenize within the barrel, resulting in a continuous and smooth PVDF molten film substrate. After cooling, the PVDF molten film substrate undergoes roller stretching. The roller stretching process uses preheating rollers of varying heights arranged sequentially, followed by synchronous preheating rollers, stretching rollers, cooling and shaping rollers, and cooling rollers. The PVDF molten film substrate is stretched after passing over these rollers in sequence. The temperature of the preheating and stretching rollers is 80℃ (i.e., the drawing temperature is 80℃), and the linear speed of the stretching rollers is... V 2. The linear velocity of the preheating roller is V 1. Speed ​​ratio R = V 2 / V 1=4, and after stretching, an oriented PVDF precursor film is obtained.

[0030] S3, High-pressure annealing: The above PVDF precursor film is placed in a high-pressure mold and pressurized to 200 MPa while being heated to 140°C for annealing. The film is then held at the pressure for 30 minutes and then cooled and shaped at room temperature to 60°C under the pressure. The film is then polarized at 100°C and an electric field strength of 450 V / μm for 30 minutes to obtain a PENG film.

[0031] S4, Microstructured TENG Anode: PDMS and curing agent are mixed in a 10:1 ratio and poured into a beaker. After stirring evenly, the mixture is placed in a vacuum drying oven for vacuum degassing for 30 minutes to obtain a degassed mixed solution. 2000-mesh high-precision sandpaper is selected as the microstructure replication template. The sandpaper needs to be cleaned with ethanol. The sandpaper is flat and fixed at the bottom of a clean petri dish with the sandpaper facing upwards. The mixed solution is then poured into the petri dish containing the 2000-mesh sandpaper and cured at room temperature for 48 hours. After curing, the sandpaper and film are slowly peeled off to replicate a PDMS film with a uniform micro-uneven structure on the surface. This PDMS film is a PDMS film with a hierarchical micro-nano structure, i.e., the TENG anode. The microstructure can significantly increase the triboelectric contact area and enhance the power generation performance.

[0032] S5, two carbon fiber prepregs (unidirectional epoxy resin-based carbon fiber prepregs) with the release paper and PE film removed are stacked one on top of the other, and the upper carbon fiber prepreg is rotated 90° and then stacked on the lower carbon fiber prepreg; after attaching the copper mesh to the upper surface of the upper carbon fiber prepreg, a copper mesh embedded carbon fiber composite material (Cu-CFRP cured material) is obtained; the carbon fiber prepregs need to be thawed for 1-3 hours before use to ensure that the resin recovers its tackiness. The following steps are taken from bottom to top: glass plate - release cloth - Cu-CFRP curing material - release cloth - separator film - breathable felt - glass plate. Then, the entire assembly is placed in a vacuum bag and a vacuum is drawn. The vacuum level is controlled above 0.8 and then placed in an oven. It is kept at 100°C for 8 hours to ensure complete curing. After curing, the Cu-CFRP curing material is demolded to obtain the TENG positive electrode.

[0033] S6. The obtained TENG negative electrode and TENG positive electrode are encapsulated with PI (polyimide). Specifically, PI is a flat hollow cylindrical structure. The TENG positive electrode and TENG negative electrode materials are tightly attached to the upper and lower surfaces of PI to form an upper and lower structure, and a certain gap is maintained between the TENG positive electrode and TENG negative electrode to ensure that the nanogenerator can be used normally.

[0034] S7. The negative electrode surface of the obtained PENG film is attached tightly to the negative electrode surface of the encapsulated TENG material, and then the positive electrode surface of the PENG film is encapsulated using PI to finally obtain P-TENG. Example 2

[0035] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing temperature in step S3 is adjusted from 140°C to 160°C. Example 3

[0036] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing temperature in step S3 is adjusted from 140°C to 180°C. Example 4

[0037] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing pressure in step S3 is adjusted from 200MPa to 100MPa. Example 5

[0038] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing pressure in step S3 is adjusted from 200MPa to 100MPa and the annealing temperature in step S3 is adjusted from 140℃ to 160℃. Example 6

[0039] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing pressure in step S3 is adjusted from 200MPa to 100MPa and the annealing temperature in step S3 is adjusted from 140℃ to 180℃. Example 7

[0040] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing pressure in step S3 is adjusted from 200MPa to 100MPa and the annealing temperature in step S3 is adjusted from 140℃ to 200℃. Example 8

[0041] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing temperature in step S3 is adjusted from 140°C to 180°C, and the 2000-mesh sandpaper in step S4 is adjusted to 60-mesh. Example 9

[0042] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing temperature in step S3 is adjusted from 140°C to 180°C, and the 2000-mesh sandpaper in step S4 is adjusted to 180-mesh. Example 10

[0043] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing temperature in step S3 is adjusted from 140°C to 180°C, and the 2000-mesh sandpaper in step S4 is adjusted to 240-mesh. Example 11

[0044] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing temperature in step S3 is adjusted from 140°C to 180°C, and the 2000-mesh sandpaper in step S4 is adjusted to 320-mesh. Example 12

[0045] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing temperature in step S3 is adjusted from 140°C to 180°C, and the 2000-mesh sandpaper in step S4 is adjusted to 600-mesh. Example 13

[0046] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing temperature in step S3 is adjusted from 140°C to 180°C, and the 2000-mesh sandpaper in step S4 is adjusted to 1000-mesh. Example 14

[0047] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing temperature in step S3 is adjusted from 140°C to 180°C, and the 2000-mesh sandpaper in step S4 is adjusted to 3000-mesh. Example 15

[0048] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing temperature in step S3 is adjusted from 140°C to 180°C, and the 2000-mesh sandpaper in step S4 is adjusted to 4000-mesh. Example 16

[0049] The preparation method of P-TENG is carried out according to the method of Example 1, except that the annealing temperature in step S3 is adjusted from 140°C to 180°C, and the 2000-mesh sandpaper in step S4 is adjusted to 7000-mesh.

[0050] Comparative Example 1 The preparation method of PENG includes the following steps: S1, Polyvinylidene fluoride (PVDF) drying: Select high-purity PVDF powder raw material, spread the PVDF powder evenly on the drying tray, with a thickness not exceeding 5mm, place it in a vacuum drying oven, set the drying temperature to 80℃, and dry at a constant temperature for 12 hours; after drying, take it out, quickly place it in a desiccator to cool naturally to room temperature, seal and store for later use, and prevent secondary moisture absorption.

[0051] S2, the dried polyvinylidene fluoride (PVDF) is poured into the hopper of a single-screw extruder. The processing temperature is 210℃, and the screw speed is 100 rpm, allowing the PVDF powder to be fully melted, plasticized, and homogenized in the barrel for extrusion, resulting in a continuous and smooth PVDF molten film substrate. After cooling, the PVDF molten film substrate undergoes roller stretching treatment at a stretching temperature of 80℃ and a speed ratio of... R =4, thus obtaining an oriented PVDF precursor film, namely PENG.

[0052] Comparative Example 2 The preparation method of PENG includes the following steps: S1, Polyvinylidene fluoride (PVDF) drying: Select high-purity PVDF powder raw material, spread the PVDF powder evenly on the drying tray, with a thickness not exceeding 5mm, place it in a vacuum drying oven, set the drying temperature to 80℃, and dry at a constant temperature for 12 hours; after drying, take it out, quickly place it in a desiccator to cool naturally to room temperature, seal and store for later use, and prevent secondary moisture absorption.

[0053] S2, the dried polyvinylidene fluoride (PVDF) is poured into the hopper of a single-screw extruder. The processing temperature is 210℃, and the screw speed is 100 rpm, allowing the PVDF powder to be fully melted, plasticized, and homogenized in the barrel for extrusion, resulting in a continuous and smooth PVDF molten film substrate. After cooling, the PVDF molten film substrate undergoes roller stretching treatment at a stretching temperature of 80℃ and a speed ratio of... R =3, thus obtaining an oriented PVDF precursor film.

[0054] S3, High-pressure heating annealing treatment: The above PVDF precursor film is placed in a high-pressure mold and heated to 60°C and held for 5 minutes. Then, the pressure is increased to 200 MPa and the temperature is increased to 180°C for annealing. The film is held under pressure for 30 minutes and then cooled and shaped at room temperature to 60°C under pressure. The film is then polarized at 100°C and electric field strength of 450 V / μm for 30 minutes to obtain PENG film.

[0055] This comparative example was not assembled with TENG, and the resulting sample was used only for comparative analysis.

[0056] Comparative Example 3 The preparation method of PENG is carried out according to the method of Comparative Example 2, except that the speed ratio in step S2 is changed. R =3 adjusted to R =4. This comparative example was not assembled with TENG; the resulting sample was used only for comparative analysis.

[0057] Comparative Example 4 The preparation method of TENG includes the following steps: S1. Mix PDMS and curing agent in a 10:1 ratio and pour into a beaker. Stir well and place in a vacuum drying oven for vacuum degassing for 30 minutes to obtain a degassed mixed solution. Select 2000-mesh high-precision sandpaper as a microstructure replication template, fix it flat at the bottom of a clean petri dish with the sandpaper facing upward. Pour the mixed solution into the petri dish containing the 2000-mesh sandpaper and cure at room temperature for 48 hours. After curing, slowly peel the sandpaper off the film to replicate a PDMS film with a uniform micro-uneven structure on the surface, which is the TENG negative electrode.

[0058] S2, two carbon fiber prepregs with the release paper and PE film removed are stacked one on top of the other, and the upper carbon fiber prepreg is rotated 90° and then stacked on the lower carbon fiber prepreg; after attaching the copper mesh to the upper surface of the upper carbon fiber prepreg, Cu-CFRP cured material is obtained. The following steps are taken from bottom to top: glass plate - release cloth - Cu-CFRP curing material - release cloth - separator film - breathable felt - glass plate. Then, the entire assembly is placed in a vacuum bag and a vacuum is drawn. The vacuum level is controlled above 0.8 and then placed in an oven. It is kept at 100°C for 8 hours to ensure complete curing. After curing, the Cu-CFRP curing material is demolded to obtain the TENG positive electrode.

[0059] This comparative example was not assembled with PENG; the resulting sample was used only for comparative analysis.

[0060] Table 1. Different parameter conditions in Examples 1-16 and Comparative Examples 1-4

[0061] The table above shows that annealing under appropriate pressure can significantly improve the long period of pre-oriented PVDF films, further perfecting their internal lamellar structure. (Observation) Figure 2 Among them are two-dimensional wide-angle X-ray diffraction (2D-WAXD) images, one-dimensional wide-angle X-ray diffraction curve (1D-WAXD) images, WAXD azimuth scan images, and Herman orientation factor ( f H The histogram and 2D-WAXD image show that Example 3 (equatorial direction) exhibits a more concentrated and stronger diffraction arc signal compared to Comparative Example 1 (meridian direction), indicating that pressure annealing further promoted crystal orientation. The corresponding 1D-WAXD curve only shows a clear β crystal (110 / 200). β (201 / 111) β The diffraction peaks confirmed that the sample prepared in Example 3 formed a highly oriented pure β phase. Furthermore, (110 / 200) diffraction peaks were observed. βIn the WAXD azimuth scan image of the crystal plane, Example 3 exhibits sharp and concentrated diffraction peaks, indicating a highly concentrated crystal orientation. The Herman orientation factor was calculated accordingly. f H The Herman orientation factor was 0.84 for Comparative Example 1 and as high as 0.98 for Example 3. f H The bar chart makes the difference more obvious, further confirming that Example 3 obtained ultra-high orientation pure β crystals.

[0062] Secondly observe Figure 2 Two-dimensional small-angle X-ray scattering (2D-SAXS) images, one-dimensional small-angle X-ray scattering (1D-SAXS) images, differential scanning calorimetry (DSC) scan images, and piezoelectric coefficient (D... 33 The bar chart shows that, in the 2D-SAXS image, Example 3 (meridian direction) exhibits a stronger scattering signal compared to Comparative Example 1 (equatorial direction), indicating that pressure annealing induced the formation of a highly ordered and oriented lamellar structure in the PVDF. The corresponding 1D-SAXS curve shows that the long-period characteristics of the layered structure in Example 3 were enhanced under high-pressure thermal annealing. Furthermore, in the differential scanning calorimetry (DSC) scan image, the high-temperature peak (167.9℃) of Example 3 corresponds to the melting of more complete and thicker lamellar (β phase), further confirming that Example 3 obtained a more stable lamellar structure. The piezoelectric coefficient (…) d 33 The bar chart can more intuitively reflect the advantages of Example 3.

[0063] Furthermore, by observing the dielectric constant ( ε ′ The spectrum images, dielectric loss (tanδ) spectrum images, and piezoelectric performance output signal images are shown. The dielectric constant spectrum and dielectric loss spectrum clearly demonstrate that high-voltage annealing significantly improves the dielectric constant of the PVDF film while maintaining low dielectric loss. Further observation of the piezoelectric performance output signal reveals that the voltage and current signals of Example 3 are significantly higher than those of Comparative Example 1. This confirms that high-voltage annealing promotes crystal perfection, suppresses the relaxation of oriented molecular chains, reduces residual porosity defects, and promotes the ordered arrangement of dipoles, thereby enhancing the piezoelectric output performance of the PVDF film.

[0064] To investigate the electrical response performance of the P-TENG sample prepared in this invention, observations were made. Figure 3A comparison of the electrical output performance of Example 3 under external force inputs of 6-36N (1Hz) and 1-4Hz (6N) shows that both the open-circuit voltage and short-circuit current of Example 3 increase with increasing external load and excitation frequency, exhibiting good linear response characteristics. Specifically, under a 36N load, the open-circuit voltage and short-circuit current reach 18.9V and 205.5nA, respectively; at a 4Hz excitation frequency, they reach 11.6V and 162.6nA, respectively, indicating that this self-sensing composite material possesses excellent mechanical stimulus response capability.

[0065] As can be seen from the above, the P-TENG prepared by this invention can respond to large external forces and high frequencies without attenuation, and can be adapted to a wider range of application scenarios.

[0066] To investigate the electrical response performance of the PENG sample prepared in this invention, observations were made. Figure 4 Comparative Example 3 shows a comparison of electrical output performance under external force inputs of 6-36N (1Hz) and 1-4Hz (6N): The open-circuit voltage and short-circuit current of Comparative Example 3 both increase with increasing external load and excitation frequency, exhibiting good linear response characteristics. Specifically, under a 36N load, the open-circuit voltage and short-circuit current reach 12V and 78nA, respectively; at an excitation frequency of 4Hz, the open-circuit voltage and short-circuit current reach 11.7V and 78.1nA, respectively.

[0067] As can be seen from the above, the electrical performance output of a single PENG is lower than that of a P-TENG, and this difference is more significant under low-frequency excitation conditions.

[0068] To investigate the electrical response performance of the TENG sample prepared in this invention, observations were made. Figure 5 Comparative Example 4 compares electrical output performance under external force inputs of 6-36N (1Hz) and 1-4Hz (6N): The open-circuit voltage and short-circuit current of Comparative Example 4 both increase with increasing external load and excitation frequency, exhibiting a good linear response. Specifically, under a 36N load, the open-circuit voltage and short-circuit current reach 5.7V and 48.4nA, respectively; at a 4Hz excitation frequency, they reach 4.7V and 48.4nA, respectively.

[0069] As can be seen from the above, the electrical performance output of a single TENG is lower than that of a P-TENG. Adding a PENG coupling can significantly improve the insufficient electrical performance output.

[0070] In summary, it can be seen that the P-TENG sample can effectively reflect changes in the external environment through its electrical response performance. Under high pressure and frequency external force conditions, the electrical output performance can still show a linear increasing trend. Moreover, its open-circuit voltage and short-circuit current output effects are higher than those of a single PENG and TENG. This indicates that after P-TENG coupling, the piezoelectric effect and triboelectric effect are mutually stimulated and the charge complementary gain is achieved.

[0071] Furthermore, this invention effectively verifies that high-pressure annealing can further improve the overall piezoelectric properties of PVDF materials, and realizes the coupling and integration of the PVDF piezoelectric layer and triboelectric unit in carbon fiber composite materials, thus preparing a material that integrates load-bearing and highly sensitive self-powered sensing functions.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A self-sensing carbon fiber composite material, comprising assembled PENG and TENG; characterized in that, The preparation method of PENG is to perform high-pressure annealing on a pre-oriented PVDF film and then obtain it by electric field polarization; the pressure applied for the high-pressure annealing is 100~500MPa and the temperature is 140~200℃.

2. The self-sensing carbon fiber composite material according to claim 1, characterized in that, TENG is obtained by assembling a PDMS film with a hierarchical micro-nano structure with a copper mesh embedded carbon fiber composite material.

3. The method for preparing a self-sensing carbon fiber composite material according to claim 1, characterized in that, Preparation of PENG: PVDF is melt-extruded through a single screw extruder, cooled, and then the extruded material is stretched by rollers to obtain a pre-oriented PVDF film. The pre-oriented PVDF film is then subjected to high-pressure annealing and electric field polarization treatment. Preparation of TENG: After stacking carbon fiber prepreg with copper mesh, copper mesh embedded carbon fiber composite material is obtained by vacuum bag molding process of prepreg. Then, PDMS film with hierarchical micro-nano structure is assembled with copper mesh embedded carbon fiber composite material to obtain TENG. Then PENG and TENG are assembled to obtain P-TENG.

4. The method for preparing a self-sensing carbon fiber composite material according to claim 3, characterized in that, The processing temperature of the single-screw extruder is 170~220℃, and the screw speed is 60~200r / min.

5. The method for preparing a self-sensing carbon fiber composite material according to claim 3, characterized in that, The temperature of the preheating roll and the stretching roll used in roller stretching forming is 80~100℃, and the speed ratio of the stretching roll to the preheating roll is... R≥ 3.

6. The method for preparing a self-sensing carbon fiber composite material according to claim 3, characterized in that, The electric field polarization temperature is 90~110℃, and the electric field strength is 350~450V / μm.

7. The method for preparing a self-sensing carbon fiber composite material according to claim 3, characterized in that, During high-pressure annealing, the temperature needs to be maintained under pressure for 30-40 minutes, and then cooled to room temperature under pressure to set.

8. The method for preparing a self-sensing carbon fiber composite material according to claim 3, characterized in that, The method for preparing PDMS thin films with hierarchical micro-nano structures is to mix PDMS and curing agent evenly, then degas the mixture under vacuum, pour the mixture into a petri dish containing sandpaper, cure it at room temperature, and then demold it.

9. A nanogenerator, characterized in that, It includes a self-sensing carbon fiber composite material as described in claim 1 or 2, or is obtained by the preparation method of the self-sensing carbon fiber composite material as described in any one of claims 3-8.

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