Structural health monitoring method of plant fiber composite material based on nano-generator

Abstract

The invention provides a structural health monitoring method of a plant fiber composite material based on a nano-generator, and belongs to the technical field of composite material health monitoring. According to the characteristic that the surfaces of plant fibers are rich in hydroxyl groups, polyvinylidene fluoride is added into resin, the plant fiber composite material with excellent mechanical properties and piezoelectric properties is prepared, and a corresponding structural health monitoring system is constructed. Compared with the prior art, the nanometer generator is well applied to health monitoring of the plant fiber composite material, the high-voltage electric field polarization operation necessary for preparing the piezoelectric nanometer generator in the prior art is simplified, and the method is simple in process, energy-saving, environment-friendly and wide in application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of health monitoring of composite materials, and particularly relates to a method for structural health monitoring of plant fiber composite materials based on a nanogenerator. Background Art

[0002] Due to their advantages such as high specific strength, high specific stiffness, and strong designability, fiber-reinforced composite materials have been widely used in fields such as aerospace, automotive, shipbuilding, mechanical manufacturing, and chemical engineering. However, artificial fibers such as carbon fibers and glass fibers consume a large amount of energy during the manufacturing process and have problems such as difficult recycling. Therefore, plant fiber composite materials with natural plant fibers as the reinforcement have attracted the attention of a large number of scholars. Plant fibers come from nature, have recyclable characteristics, and relatively low costs, meeting the current global requirements for environmental protection and sustainable development, and having great application prospects. During the long-term use of composite materials, different degrees of damage will inevitably occur. These unpredictable damages will lead to a decrease in their mechanical properties, thereby affecting their normal use. Therefore, it is very important to detect damage to composite materials.

[0003] Structural health monitoring is a highly feasible and economical damage detection method. Compared with traditional non-destructive testing, structural health monitoring can achieve continuous, spontaneous, and real-time monitoring, timely feedback the safety performance of the structure, and has a wider monitoring range. This technology usually collects signals related to the structural health state in real time through sensors integrated inside or on the surface of the structure, and then extracts damage characteristic parameters through signal processing to achieve online monitoring. Different health monitoring methods require different types of sensors, mainly including fiber optic sensors, acoustic sensors, and piezoresistive sensors. However, integrating most sensors into the composite material structure in an intercalation or surface pasting manner will reduce the mechanical properties of the composite material, and their sensing performance is also easily affected by the environment, and the sensing performance will be greatly reduced in high-temperature and high-humidity environments. In addition, these sensors generally require an external power source to maintain normal operation, which is contrary to the green environmental protection concept of plant fiber composite materials. In contrast, applying a nanogenerator that can convert mechanical energy into electrical energy to the structural health monitoring of plant fiber composite materials not only has a simple structure and high sensitivity, but also can achieve energy self-sufficiency, which has important research significance.

[0004] Nanogenerators are mainly divided into piezoelectric nanogenerators and triboelectric nanogenerators. The working principle of piezoelectric nanogenerators is electrostatic induction and piezoelectric effect, and the working principle of triboelectric nanogenerators is electrostatic induction and triboelectrification effect. They can convert different forms of mechanical energy into electrical energy and show broad application prospects in many fields. At present, only a few researchers have applied them to the structural health monitoring of composite materials. Chinese Patent CN118418486A provides a preparation process, production device, product and application of a carbon fiber reinforced composite material plate. By filling specific polytetrafluoroethylene balls in a specific aramid paper honeycomb core, the obtained carbon fiber reinforced composite material can convert vibration mechanical energy into electrical energy and can provide distributed energy for the health monitoring system and street lamp system of bridges. However, this technology is only used to supply power to the health monitoring system and cannot eliminate the problem of reduced mechanical properties caused by the integration of sensors in the composite material structure in the monitoring system. Chinese Patent CN114414107A discloses a preparation method of a high-strength carbon fiber composite material with self-sensing function. Using carbon fiber as the substrate, atomic layer deposition technology enables the piezoelectric nanolayer to be uniformly and densely distributed on the substrate. While maintaining the performance advantages of the original high strength of the structural material, in-situ detection of the damage location and degree of damage is realized, and there is a warning function for serious damage to the material. However, this technology has a complex process and a long cycle, and due to the need to use atomic layer deposition technology, it is only applicable to carbon fiber composite materials with high temperature and corrosion resistance. Chinese Patent CN116940205A discloses a preparation method of a self-powered and self-sensing piezoelectric composite material. By adding polyvinylidene fluoride and barium titanate to a fiber-reinforced resin-based composite material, a piezoelectric composite material is prepared, which can realize the health state diagnosis without additional sensors. However, the barium titanate added in this technology will cause a reduction in the mechanical properties of the plant fiber composite material. At the same time, it must require a polarization operation, and the two-step process of pre-forming and then polarizing is complex and costly.

[0005] Currently, the structural health monitoring of plant fiber composite materials based on nanogenerators has certain limitations due to reasons such as complex preparation processes and reduced mechanical properties of the prepared composite materials. Summary of the Invention

[0006] The present invention is made to solve the above problems, and aims to provide a structural health monitoring method for plant fiber composite materials based on nanogenerators.

[0007] The present invention provides a method for structural health monitoring of a plant fiber composite material based on a nanogenerator, which has the following characteristics and includes the following steps: S10, soaking a plant fiber fabric in a strong alkali solution for a period of time, then taking it out, washing and drying it to serve as a reinforcing phase; S20, uniformly mixing a thermosetting resin solution, PVDF and a curing agent to obtain a matrix phase; S30, curing and molding the matrix phase and the reinforcing phase through a molding process to prepare a plant fiber composite material serving as a piezoelectric nanogenerator; S40, after processing the plant fiber composite material according to the required dimensions of the workpiece, placing electrodes at corresponding positions on its surface and encapsulating; S50, performing a three-point bending test on the plant fiber composite material, and detecting the output electrical signal of the electrodes through a detection device to achieve damage monitoring and positioning of the plant fiber composite material.

[0008] In the method for structural health monitoring of a plant fiber composite material based on a nanogenerator provided by the present invention, it may further have the following characteristics: wherein, in step S10, the material of the plant fiber fabric includes any one or more of hemp fiber, bamboo fiber, cellulose fiber or wood fiber, the hemp fiber includes any one or more of flax fiber, sisal fiber or ramie fiber, and the weaving method of the plant fiber fabric is unidirectional arrangement, two-dimensional weaving or three-dimensional weaving.

[0009] In the method for structural health monitoring of a plant fiber composite material based on a nanogenerator provided by the present invention, it may further have the following characteristics: wherein, in step S10, the preparation method of the strong alkali solution is: dissolving a strong alkali in water at 40°C to 50°C and preparing it into a 4wt% to 10wt% solution, and the strong alkali includes any one of NaOH, Ca(OH)2, ammonia water, Na2CO3 or NaHCO3.

[0010] In the method for structural health monitoring of a plant fiber composite material based on a nanogenerator provided by the present invention, it may further have the following characteristics: wherein, in step S10, the soaking time is 8h to 12h, the washing method is to repeatedly rinse with clean water and remove the residual alkali solution thereon, and the drying method is heat drying or vacuum drying.

[0011] In the method for structural health monitoring of a plant fiber composite material based on a nanogenerator provided by the present invention, it may further have the following characteristics: wherein, in step S20, the resin in the resin solution includes any one or more of epoxy resin, phenolic resin, unsaturated polyester, polyurethane or bismaleimide resin, and the mass fraction of PVDF in the matrix phase is denoted as ω, 0wt% < ω ≤ 20wt%.

[0012] In the structural health monitoring method of the plant fiber composite material based on the nanogenerator provided by the present invention, it may further have the following characteristics: Among them, in step S30, the forming process includes any one of a hot pressing process, an RTM process, or an autoclave process.

[0013] In the structural health monitoring method of the plant fiber composite material based on the nanogenerator provided by the present invention, it may further have the following characteristics: Among them, in step S40, the material of the electrode is a conductive substance, and the conductive substance includes a metal, a metal oxide, or a conductive polymer. The size of the electrode is 0.25 cm 2 ~4 cm 2 , and the material used for encapsulation is an insulating material, and the insulating material includes silica gel or polyimide film. The size of the material used for encapsulation is 2 to 4 times the size of the electrode.

[0014] In the structural health monitoring method of the plant fiber composite material based on the nanogenerator provided by the present invention, it may further have the following characteristics: Among them, in step S50, damage localization of the plant fiber composite material is achieved through the output electrical signals corresponding to the electrodes at different positions.

[0015] In the structural health monitoring method of the plant fiber composite material based on the nanogenerator provided by the present invention, it may further have the following characteristics: Among them, it further includes the following steps: S60, setting corresponding thresholds according to the output electrical signals corresponding to the electrodes of the plant fiber composite material under different damage degrees and / or damage forms, and designing relevant programs according to the corresponding thresholds to construct a structural health monitoring system that realizes online alarm and remote warning functions. The structural health monitoring system includes: a detection device, electrically connected to the electrode, including any one or more of a multimeter, an electrometer, or an oscilloscope, for detecting the output electrical signal of the electrode; an Arduino board, electrically connected to the detection device, for allowing the user to input the relevant program designed according to the corresponding threshold and receiving the output electrical signal detected by the detection device; a wireless device, including a mobile phone terminal and / or a computer terminal, communicatively connected to the wireless module of the Arduino board, for receiving the output electrical signal detected by the detection device transmitted by the Arduino board to achieve remote warning; and an alarm device, including an LED and / or a buzzer, communicatively connected to the wireless module of the Arduino board, for receiving the output electrical signal detected by the detection device transmitted by the Arduino board to achieve online alarm.

[0016] In the structural health monitoring method of the plant fiber composite material based on the nanogenerator provided by the present invention, it may further have the following characteristics: Among them, the characteristic parameters of the output electrical signal include voltage, voltage frequency, and voltage waveform.

[0017] Functions and effects of the invention

[0018] The method for structural health monitoring of a plant fiber composite based on a nanogenerator according to the present invention involves adding a piezoelectric material, polyvinylidene fluoride (PVDF), to a resin solution and then curing it with plant fibers to form a composite material. The entire plant fiber composite material serves as a piezoelectric nanogenerator, and its piezoelectric effect can be used to detect and locate its own damage. The manufacturing process is simple, the monitoring range is wide, the use of sensors is avoided, it is green and environmentally friendly, and it conforms to the concept of green composite materials for plant fiber composites.

[0019] The present invention only uses one piezoelectric material, PVDF. However, since the hydroxyl groups rich on the surface of plant fibers will form hydrogen bonds with the -CF groups in PVDF, it not only stabilizes the material system but also induces the formation of the β phase, enhancing the macroscopic polarization and piezoelectric properties. This simplifies the high-voltage electric field polarization operation that is necessary for preparing piezoelectric nanogenerators in the prior art, with a simple process, energy conservation, and environmental protection. In addition, on the one hand, the use of PVDF in plant fiber composites will bring higher piezoelectric properties, which can avoid the addition of piezoelectric ceramics that can enhance piezoelectric properties but cause a decrease in mechanical properties. On the other hand, the addition of PVDF can enhance the mechanical properties of the material. Therefore, using only one piezoelectric material, PVDF, can ensure that the prepared plant fiber composite material has high mechanical properties.

[0020] The present invention realizes the in-situ detection of the damage location and damage degree through the response of electrical signals at different positions of the plant fiber composite material to damage. In addition, by setting relevant thresholds for different damage degrees and then constructing a relevant structural health monitoring system, it can timely feedback the damage state of the composite material through an online device to achieve the remote warning function, and can meet the application requirements in actual complex scenarios. Description of the Drawings

[0021] Figure 1 is a flowchart of the method for structural health monitoring of a plant fiber composite based on a nanogenerator according to an embodiment of the present invention;

[0022] Figure 2 is a schematic diagram of the interaction between PVDF and plant fibers in an embodiment of the present invention;

[0023] Figure 3 is a comparison chart of the flexural strength of the plant fiber composite material in an embodiment of the present invention and the blank group (plant fiber composite material without added PVDF);

[0024] Figure 4 is a schematic diagram of the piezoelectric properties of the plant fiber composite material under loads of different sizes and frequencies in an embodiment of the present invention;

[0025] Figure 5It is the top view and front view of the plant fiber piezoelectric material under the three-point bending test in step S50 of the embodiment of the present invention;

[0026] Figure 6 It is the electrical signal output curve and force-time curve of different corresponding positions of each electrode under the three-point bending test in step S50 of the embodiment of the present invention;

[0027] Figure 7 It is the schematic diagram of the structural health monitoring system constructed in step S60 of the embodiment of the present invention. Detailed implementation manners

[0028] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the following embodiments will specifically elaborate on a structural health monitoring method of a plant fiber composite material based on a nanogenerator of the present invention in conjunction with the accompanying drawings.

[0029] <Embodiment>

[0030] Figure 1 It is the flow block diagram of the structural health monitoring method of the plant fiber composite material based on a nanogenerator in the embodiment of the present invention.

[0031] As Figure 1 shown, this embodiment provides a structural health monitoring method of a plant fiber composite material based on a nanogenerator, including the following steps:

[0032] S10, preparing a reinforcing phase, including the following sub-steps S11 to S13:

[0033] S11, dissolving a strong base in water at 40°C to 50°C and configuring it into a strong base solution with a concentration of 4wt% to 10wt%.

[0034] Among them, the strong base includes any one of NaOH, Ca(OH)2, ammonia water, Na2CO3 or NaHCO3 (in this embodiment, NaOH is specifically selected).

[0035] S12, immersing the plant fiber fabric in the strong base solution for 8h to 12h.

[0036] Among them, the plant fiber fabric is a unidirectionally arranged, two-dimensional woven or three-dimensional woven hemp fiber (any one or more of flax fiber, sisal fiber or ramie fiber), bamboo fiber, cellulose fiber or wood fiber (in this embodiment, the plant fiber fabric is specifically a unidirectionally arranged fabric).

[0037] S13, taking out the plant fiber fabric soaked in step S12, repeatedly rinsing it with clean water to remove the residual alkali solution, and placing it in an oven for drying at a drying temperature of 80°C and a drying time of 5h to prepare the reinforcing phase.

[0038] S20. Prepare the matrix phase, including the following sub-steps S21 to S22:

[0039] S21. Mix the thermosetting resin solution and the curing agent to obtain a first mixed solution.

[0040] Among them, the addition amount of the curing agent depends on the selection of the resin and the subsequent molding process (specifically in this embodiment, the resin solution and the curing agent are mixed according to a mass ratio of 100:26).

[0041] The resin includes any one or more of epoxy resin, phenolic resin, unsaturated polyester, polyurethane, or bismaleimide resin (specifically epoxy resin in this embodiment).

[0042] S22. Add PVDF to the first mixed solution and stir and mix. Observe the color degree in the solution during stirring, and stir it sufficiently until it is uniformly mixed to obtain the matrix phase, and make the mass fraction of PVDF in the matrix phase be 0 wt% to 20 wt% (specifically 10 wt% in this embodiment).

[0043] Among them, the stirring and mixing method includes manual stirring and using a stirrer, and the stirring time depends on the mixing degree of the matrix phase (specifically, an electric stirrer is used for stirring and mixing in this embodiment).

[0044] S30. Prepare the plant fiber composite material as a piezoelectric nanogenerator, including the following sub-steps S31 to S32:

[0045] S31. Use the hand lay-up process to lay the reinforcing phase obtained in step S13 and the matrix phase obtained in step S22 on a flat mold.

[0046] Among them, the laying method and the number of layers depend on the requirements of the plant fiber composite material parts.

[0047] S32. The lay-up in step S31 is cured and formed by a molding process to prepare a plant fiber composite material as a piezoelectric nanogenerator.

[0048] Among them, the molding process includes any one of a hot pressing process, an RTM process, or an autoclave process. Specifically, in this embodiment, the molding process is a hot pressing process carried out in a hot press, and the specific process parameters are: preheat for 0.5 h under the conditions of a pressure of 0.2 MPa and a temperature of 90 °C, then form for 3 h under the conditions of a pressure of 1.2 MPa and a temperature of 120 °C, and finally cool at room temperature.

[0049] Figure 2 It is a schematic diagram of the interaction between PVDF and plant fibers in the embodiment of the present invention.

[0050] AsFigure 2 As shown, the hydroxyl groups rich on the surface of plant fibers will form hydrogen bonds with the -CF groups in PVDF, enhancing its macroscopic polarization and thus increasing the proportion of the β-phase in PVDF.

[0051] Figure 3 It is a comparison chart of the flexural strength between the plant fiber composite material in the embodiment of the present invention and the blank group (plant fiber composite material without added PVDF).

[0052] Use an electronic universal testing machine to conduct a three-point bending test on the PVDF group (the plant fiber composite material in this embodiment) and the blank group (plant fiber composite material without added PVDF), and compare the mechanical properties of the two to verify the high mechanical properties of the prepared plant fiber piezoelectric composite material. As Figure 3 shown, after adding PVDF in step S22 in this embodiment, the plant fiber composite material finally prepared in step S30 has improved mechanical properties compared with the blank group (plant fiber composite material without added PVDF).

[0053] S40. Set electrodes and encapsulate, including the following sub-steps S41 to S42:

[0054] S41. Cut the plant fiber composite material prepared in step S32 into a size of 100 mm × 13 mm according to the ASTM D7264 standard to obtain specimens.

[0055] S42. Paste electrodes at corresponding positions on the surface of the specimens and encapsulate.

[0056] Among them, the placement position of the electrodes depends on the shape of the plant fiber composite material, and the number of electrodes depends on the size of the plant fiber composite material. Specifically, in this embodiment, the corresponding positions are the middle part of the specimen and the upper and lower surfaces at 10 mm, 20 mm, and 40 mm away from the middle part.

[0057] The material of the electrodes is a conductive substance, and the conductive substance includes metals, metal oxides, or conductive polymers. The electrode size is 0.25 cm 2 ~4 cm 2 . Specifically, in this embodiment, the electrodes are copper strips of 10 mm × 10 mm.

[0058] The material used for encapsulation is an insulating material, and the insulating material includes silica gel or polyimide film. The size of the material used for encapsulation is 2 to 4 times the electrode size. Specifically, in this embodiment, the insulating material used for encapsulation is polyimide film.

[0059] Figure 4 It is a schematic diagram of the piezoelectric properties of the plant fiber composite material under loads of different sizes and frequencies in the embodiment of the present invention.

[0060] By controlling the output pressure and frequency of the motor to apply loads of different magnitudes and frequencies at the middle part of the plant fiber composite material encapsulated with electrodes, the electrodes on the upper and lower surfaces of the plant fiber piezoelectric composite material are connected to detection devices (including devices such as multimeters, electrometers, oscilloscopes, etc.), and at the same time, data is read on a computer to detect the piezoelectric properties of the prepared plant fiber composite material. As Figure 4 shown, the plant fiber piezoelectric composite material in this embodiment is sensitive, and its electrical signal output can respond to load actions in different forms.

[0061] S50, damage monitoring and location:

[0062] Figure 5 are the top view and front view of the plant fiber piezoelectric material under the three-point bending test in step S50 of the embodiment of the present invention.

[0063] As Figure 5 shown, the electrodes 2 encapsulated on the upper and lower surfaces of the plant fiber composite material 1 in step S42 are connected to the detection device through wires 3, and a three-point bending test is performed on the plant fiber composite material 1. Relevant output electrical signals (including voltage, voltage frequency, and voltage waveform) are read on a computer to achieve real-time monitoring of the plant fiber composite material 1, and damage location is achieved according to the electrical signal characteristics of the electrodes 2 at different positions.

[0064] Figure 6 are the electrical signal output curves and force-time curves at different corresponding positions of each electrode under the three-point bending test in step S50 of the embodiment of the present invention. Among them, part (a) corresponds to the electrical signal output curve and force-time curve at the middle part of the plant fiber composite material; part (b) corresponds to the electrical signal output curve and force-time curve in the area 1 cm away from the middle part on the plant fiber composite material; part (b) corresponds to the electrical signal output curve and force-time curve in the area 2 cm away from the middle part on the plant fiber composite material; part (b) corresponds to the electrical signal output curve and force-time curve in the area 4 cm away from the middle part on the plant fiber composite material.

[0065] As Figure 6 shown, there is an obvious corresponding relationship between the electrical signal output curve and the force-time curve at the middle part (i.e., the damaged part), while no corresponding relationship appears in other parts, indicating that the method of this embodiment has successfully achieved damage monitoring and location.

[0066] S60, constructing a structural health monitoring system:

[0067] Set corresponding thresholds according to the output electrical signals of the electrodes corresponding to the plant fiber composite materials under different degrees and / or forms of damage, and design relevant programs according to the corresponding thresholds to construct a structural health monitoring system that realizes online alarm and / or remote early warning functions.

[0068] Figure 7 It is a schematic diagram of the structural health monitoring system constructed in step S60 of the embodiment of the present invention.

[0069] As Figure 7 shown, the structural health monitoring system 100 includes a detection device 10, an Arduino board 20, a wireless device 30, and an alarm device 40.

[0070] The detection device 10 is electrically connected to the electrodes 2 encapsulated on the upper and lower surfaces of the plant fiber composite material 1, and includes any one or more of a multimeter, an electrometer, or an oscilloscope, and is used to detect the output electrical signals (including voltage, voltage frequency, and voltage waveform) of the electrodes 2.

[0071] The Arduino board 20, which is electrically connected to the detection device 10, is used for the user to input relevant programs designed according to the corresponding thresholds of the output electrical signals under different loads or different degrees of damage of the plant fiber composite material 1, and to receive the output electrical signals detected by the detection device 10.

[0072] The wireless device 30 includes a mobile phone terminal and / or a computer terminal, and is communicatively connected to the wireless module of the Arduino board 20, and is used to receive the output electrical signals detected by the detection device 10 transmitted by the Arduino board 20 to realize remote early warning.

[0073] The alarm device 40 includes an LED and / or a buzzer, and is communicatively connected to the wireless module of the Arduino board 20, and is used to receive the output electrical signals detected by the detection device 10 transmitted by the Arduino board 20 to realize online alarm.

[0074] In this embodiment, relevant thresholds are set according to the obtained output electrical signals under different loads or different degrees of damage, the written code is imported into the Arduino board 20, and the relevant electrical signals output by the electrodes 2 are collected through an electrical signal collector (detection device 10), and the characteristic parameters of the electrical signals (including voltage, voltage frequency, and voltage waveform) are output to the Arduino board 20. On the one hand, by connecting to the alarm device 40 (LED and buzzer), the online alarm function for the damage of the plant fiber composite material 1 is realized; on the other hand, relevant information is output to the wireless device 30 (mobile phone terminal and / or computer terminal) through its wireless module (Bluetooth module and / or WiFi module) to realize remote early warning of the damage of the plant fiber composite material 1.

[0075] Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A structural health monitoring method for a plant fiber composite material based on a nanogenerator, characterized in that, It includes the following steps: S10. Immerse the plant fiber fabric in a strong alkali solution for a period of time, then take it out, wash and dry it to obtain the reinforcing phase; S20. Mix the thermosetting resin solution, PVDF and curing agent evenly to obtain the matrix phase; S30. Cure and mold the matrix phase and the reinforcing phase through a molding process to prepare a plant fiber composite material as a piezoelectric nanogenerator; S40. After processing the plant fiber composite material according to the required size of the workpiece, place electrodes at corresponding positions on its surface and encapsulate; S50. Conduct a three-point bending test on the plant fiber composite material, and detect the output electrical signal of the electrode through a detection device to realize damage monitoring and positioning of the plant fiber composite material.

2. The structural health monitoring method of the plant fiber composite material based on a nanogenerator according to claim 1, wherein: Among them, In step S10, the material of the plant fiber fabric includes any one or more of hemp fiber, bamboo fiber, cellulose fiber or wood fiber, The hemp fiber includes any one or more of flax fiber, sisal fiber or ramie fiber, The weaving method of the plant fiber fabric is unidirectional arrangement, two-dimensional weaving or three-dimensional weaving.

3. The structural health monitoring method of the plant fiber composite material based on a nanogenerator according to claim 1, wherein: Among them, In step S10, the preparation method of the strong alkali solution is: dissolve the strong alkali in water at 40°C to 50°C and configure it into a 4wt% to 10wt% solution, The strong alkali includes any one of NaOH, Ca(OH)2, ammonia water, Na2CO3 or NaHCO3.

4. The structural health monitoring method of the plant fiber composite material based on a nanogenerator according to claim 1, wherein: Among them, In step S10, the soaking time is 8h to 12h, The cleaning method is to repeatedly rinse with clean water and remove the residual alkali solution on it, The drying method is heat drying or vacuum drying.

5. The structural health monitoring method of the plant fiber composite material based on a nanogenerator according to claim 1, wherein: Among them, In step S20, the resin in the resin solution includes any one or more of epoxy resin, phenolic resin, unsaturated polyester, polyurethane or bismaleimide resin, Denote the mass fraction of PVDF in the matrix phase as ω, 0wt% < ω ≤ 20wt%.

6. The structural health monitoring method of the plant fiber composite material based on a nanogenerator according to claim 1, wherein: Among them, In step S30, the molding process includes any one of a hot pressing process, an RTM process or an autoclave process.

7. The structural health monitoring method of the plant fiber composite material based on a nanogenerator according to claim 1, wherein: Among them, In step S40, the material of the electrode is a conductive substance, the conductive substance includes a metal, a metal oxide or a conductive polymer, and the size of the electrode is 0.25 cm 2 to 4 cm 2 , The material used for encapsulation is an insulating material, and the insulating material includes silica gel or polyimide film. The size of the material used for encapsulation is 2 to 4 times the size of the electrode.

8. The structural health monitoring method of the plant fiber composite material based on a nanogenerator according to claim 1, wherein: Among them, In step S50, damage localization of the plant fiber composite material is achieved through the output electrical signals corresponding to the electrodes at different positions.

9. The structural health monitoring method of the plant fiber composite material based on the nanogenerator according to claim 1, wherein It further includes the following steps: S60. Set corresponding thresholds according to the output electrical signals corresponding to the electrodes of the plant fiber composite material under different damage degrees and / or damage forms, and design relevant programs according to the corresponding thresholds to construct a structural health monitoring system that realizes online alarm and remote warning functions. The structural health monitoring system includes: A detection device, electrically connected to the electrode, including any one or more of a multimeter, an electrometer, or an oscilloscope, and is used to detect the output electrical signal of the electrode. An Arduino board, electrically connected to the detection device, is used for the user to input relevant programs designed according to the corresponding thresholds, and receive the output electrical signal detected by the detection device. A wireless device, including a mobile phone terminal and / or a computer terminal, is communicatively connected to the wireless module of the Arduino board, and is used to receive the output electrical signal detected by the detection device transmitted by the Arduino board to realize remote warning; and An alarm device, including an LED and / or a buzzer, is communicatively connected to the wireless module of the Arduino board, and is used to receive the output electrical signal detected by the detection device transmitted by the Arduino board to realize online alarm.

10. The structural health monitoring method of a plant fiber composite material based on a nanogenerator according to any one of claims 1 to 9, characterized in that: Among them, The characteristic parameters of the output electrical signal include voltage, voltage frequency, and voltage waveform.

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