Resin-based piezoelectric composite smart material and application thereof

Abstract

This invention discloses a resin-based piezoelectric composite smart material and its applications. The material comprises piezoelectric ceramic powder and resin in a mass ratio of 5:1, with glass fibers layered internally. It is obtained by mixing and stirring the piezoelectric ceramic powder and resin in the specified ratio, vacuuming, molding, laying glass fibers, curing, electrode plating, and polarization. It can be used in structural health monitoring, human-computer interaction, and intelligent robotics. Based on this material, this invention proposes a resin-based piezoelectric composite smart structure that integrates sensors and structural components, combining load-bearing capacity with the ability to transmit and receive high-frequency mechanical waves. This results in good actuation and sensing effects, enabling various forms of sensing and control, greatly simplifying structural health monitoring methods and reducing costs. It also has self-damage monitoring capabilities, allowing for self-detection and self-repair of the material to improve its reliability and durability.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a resin-based piezoelectric composite smart material and its applications. Background Technology

[0002] Reinforced concrete and other structural components are widely used as the main load-bearing components of various engineering infrastructures. However, external forces such as wind, earthquakes, and vehicle vibrations can cause internal damage, thereby endangering the safety of the entire building. Therefore, the development of intelligent systems with smart sensors to monitor structures throughout their entire life cycle has attracted increasing interest. Current methods mainly involve using various types of sensors in combination on the structure for monitoring. Among them, piezoelectric sensors are widely used in the field of structural health monitoring due to their advantages such as high sensitivity, high dynamic range, low threshold level, high resonant frequency, wide bandwidth, low cost, and large batch production.

[0003] For structural health monitoring, existing technologies mainly focus on three areas:

[0004] Direction 1: Surface-mounted piezoelectric sensors for structural components. Piezoelectric wafer active sensors (PWASs) have been widely used to generate and receive ultrasonic guided waves. By directly bonding or embedding piezoelectric wafers into structures, they measure physical motion or strain within the main structure. Piezoelectric ceramics are perhaps the most popular piezoelectric material for sensing applications. However, piezoelectric wafer active sensors are brittle materials, and cracks in the sensor itself may limit their use in applications involving large deformations. Furthermore, they do not adhere well to surfaces with complex geometries and are prone to debonding and peeling, significantly impacting the effectiveness of structural health monitoring.

[0005] Direction Two: Embedding piezoelectric sensors within structural components. Minakuchi and Takeda et al. have implemented fiber optic sensors for impact damage detection in aerospace composite structures. Krishnamurthy et al. have embedded magnetostrictive particle layers in composite laminates to achieve layered detection. Paget et al. conducted experiments on the performance of embedded piezoelectric ceramic transducers in mechanically loaded composite materials, and the results showed that the survival rate of the sensors was very low. It is evident that embedding piezoelectric sensors within structural components can disrupt the internal structure and even cause stress concentration during structural use, which may lead to structural safety hazards or even structural failure.

[0006] Direction 3: Deploying piezoelectric composite material sensors on structural components. Using polymer-based piezoelectric coatings that can be directly deposited onto the surface of the main structure, piezoelectric coatings offer advantages over traditional piezoelectric ceramics in terms of adjustable mechanical properties (e.g., flexibility), low manufacturing cost, large coverage area, and adaptability to curved surfaces. Tallman et al. used carbon nanofibers / polyurethane to prepare nanocomposite materials, achieving enhanced layered detection and distributed strain sensing; Gallo and Thostenson distributed carbon nanotubes in composite materials to establish structural self-sensing capabilities and successfully monitored microcracks in the material; Haghhiashtiani and Greminger used polyvinylidene fluoride (PVDF) as a composite matrix for integrated structural load sensing, and this piezoelectric composite material exhibited excellent sensing capabilities in low-frequency mechanical tests. However, when polymer-based piezoelectric coatings are deposited on the surface of the main structure, the piezoelectric composite sensor has a smaller piezoelectric constant compared to traditional piezoelectric sensors. According to the inverse piezoelectric effect, under the same electric field, the mechanical disturbance generated by the piezoelectric composite actuator is weaker than that of the PZT patch. Furthermore, such sensors are more expensive and difficult to manufacture. Summary of the Invention

[0007] In view of the above-mentioned shortcomings of the prior art, the main objective of the present invention is to provide a resin-based piezoelectric composite smart material with high sensitivity, high precision, load-bearing and sensing characteristics, which can be applied to structural health monitoring applications.

[0008] Another objective of this invention is to provide a resin-based piezoelectric composite smart structure. Laying glass fibers in the resin can increase the structural strength, while mixing piezoelectric ceramic powder produces an actuation sensing effect, thus integrating the structure's load-bearing and self-sensing functions.

[0009] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0010] This invention provides a resin-based piezoelectric composite smart material, comprising piezoelectric ceramic powder and resin, and further comprising glass fiber, wherein the glass fiber is a mesh-like glass fiber, laid layer by layer in the structure, and the glass fiber accounts for 30% of the total structural volume fraction. The mass ratio of the piezoelectric ceramic powder to the resin is 5:1. The material is obtained by mixing and stirring the above raw materials according to the ratio, vacuuming, molding, laying glass fiber, curing, electrode plating, and polarization.

[0011] Preferably, the piezoelectric ceramic powder is lead zirconate titanate (PZT) powder with a particle size of 120-200 mesh.

[0012] Preferably, the resin is an epoxy resin, and more preferably a mixture of HF-005 and HF-006.

[0013] More preferably, the mass ratio of the PZT powder to the epoxy resin is 5:1.

[0014] In the above technical solution, the PZT powder is a ceramic material composed of elements such as lead, zirconium, and titanium, and is a piezoelectric material; the epoxy resin is a polymer compound that can be used as an adhesive or plastic.

[0015] This invention provides a resin-based piezoelectric composite smart structure, which is obtained by a preparation method including the following steps:

[0016] Step 1: Mix PZT powder and epoxy resin at a mass ratio of 5:1;

[0017] Step 2: Pour the mixture into a mold and vacuum process it;

[0018] Step 3: Place the mixture in the mold at a constant temperature of 60℃ for 4 hours to cure;

[0019] Step 4: Apply the polarization electrode using silver wire mesh printing at a high temperature of 110℃ for 45 minutes;

[0020] Step 5: Polarize using a high-voltage amplifier immersed in oil at a voltage of 6 kV for 15 minutes;

[0021] Step 6: The initial polarization electrode covers the upper and lower surfaces of the entire piezoelectric composite material structure, and the structure is machined to the required dimensions;

[0022] Step 7: Remove excess silver layer from the surface of the structure by laser engraving, leaving the electrode components intact.

[0023] This invention provides an application of resin-based piezoelectric composite smart material in structural health monitoring, human-computer interaction, and intelligent robot fabrication.

[0024] Compared with existing technologies, this invention breaks away from conventional methods of structural health detection that rely on sensors integrated with structural components. It integrates multiple sensing methods, including piezoelectric, fiber, and electromagnetic sensing, and proposes a resin-based piezoelectric composite intelligent structure. This structure combines sensors and structural components into a structure-sensor integrated system, forming an intelligent "skin / skeleton" system. Combined with an electrode circuit array design, it constructs adaptive, highly distributed structural sensing "neurons," integrating load-bearing function with the ability to transmit and receive high-frequency mechanical waves. This achieves an integrated intelligent material structure that combines load-bearing and sensing capabilities. The structure itself is both a sensor and a load-bearing component, establishing a self-aware structure and pioneering a new paradigm of self-aware intelligent structures. This has the following beneficial effects:

[0025] 1. Improve the structural strength of the material: Glass fiber is mixed with resin glue, curing agent and piezoelectric ceramic powder, and through processes such as vacuuming, mold shaping, glass fiber laying, curing, electrode plating and polarization, the resulting piezoelectric composite smart material has high structural strength and can maintain stable performance in various environments, making it suitable for applications under various load conditions.

[0026] 2. Achieving Self-Sensing Integration: The piezoelectric ceramic powder incorporated into the piezoelectric composite smart material enables it to achieve self-sensing functionality, that is, it can automatically detect whether there is damage in the material. The mechanical impedance method and active ultrasonic sensing simulation of the piezoelectric composite material can effectively verify the self-sensing integration effect of the piezoelectric composite material and evaluate the material's monitoring capability after being damaged. This self-damage monitoring function is of great significance for realizing the material's self-detection and self-repair, and can improve the material's reliability and durability.

[0027] 3. Excellent actuation and sensing performance: It integrates load-bearing and self-sensing into one unit, upgrading the traditional method of attaching sensors to the area to be measured to brushing electrodes on the area to be measured. It can realize various forms of sensing and control, such as sensing and controlling signals such as vibration, deformation, and temperature, which greatly simplifies the method and reduces the cost of structural health monitoring and has significant economic value.

[0028] 4. Significant benefits: The preparation process is simple and the cost is low, which allows for large-scale production. Resin-based piezoelectric composite smart materials can be used in many fields such as structural health monitoring, human-computer interaction, and intelligent robots. In particular, structural health monitoring applications in safety-critical fields such as aviation, aerospace, high-speed trains, and nuclear power plants have broad application prospects and significant economic benefits. Attached Figure Description

[0029] Figure 1 The image shown is an electron microscope image of a piezoelectric ceramic powder sample with a mesh size of 300 or larger, as described in the example.

[0030] Figure 2 The image shown is an electron microscope image of a 200-300 mesh piezoelectric ceramic powder sample from the examples.

[0031] Figure 3 The images shown are electron microscope images of 120-200 mesh piezoelectric ceramic powder samples from the examples.

[0032] Figure 4 The mechanical electrical impedance finite element analysis model in the embodiment is as follows: a) no damage; b) one damage point; c) two damage points.

[0033] Figure 5 The simulation results of RSMD for each electrode pair in the examples are as follows: a) one-damage model; b) two-damage model.

[0034] Figure 6 The sample shown is a resin-based piezoelectric composite smart material from an example.

[0035] Figure 7 This is a diagram showing the setup of the internal electrical impedance analysis experiment in the example.

[0036] Figure 8 The experimental results for RSMD of each electrode pair in the examples are as follows: a) one damage model; b) two damage models.

[0037] Figure 9 The active sensing finite element models in the embodiments are: a) non-damaging model; b) damaged model.

[0038] Figure 10 The results are simulation results of the active sensing finite element model in the example.

[0039] Figure 11 This is a diagram showing the setup of the active ultrasonic sensing experiment in the example.

[0040] Figure 12 The results of the active sensing test in this embodiment are shown.

[0041] Figure 13 A flowchart for creating an example is provided. Detailed Implementation

[0042] The present invention will be further described below with reference to the embodiments and accompanying drawings:

[0043] In the following embodiment, a beam with a length of 500 mm, a width of 27.8 mm, and a thickness of 3 mm is fabricated. To facilitate subsequent electrode voltage loading, nine pairs of 10 mm diameter electrodes are strategically placed on the upper and lower surfaces of the beam, with a distance of 50 mm between each pair. To achieve the required electrode voltage load, a portion of the silver layer is reserved to form a conductive circuit. This design differs from conventional post-weld wire-loaded voltage at the electrodes in that it allows for the introduction of external interfaces anywhere on the structural surface, thereby enhancing the product's designability. Simultaneously, the implementation of multiple circuits improves the reliability of the interfaces, allowing for the use of alternative interfaces in the event of any unforeseen damage or failure, thus increasing its resilience and practicality.

[0044] Mechanical impedance method: To assess localized structural damage, an iron block is fixed to the sample surface to evaluate changes in the impedance spectrum at the damaged area. The basic principle of using an iron block to simulate damage is based on the ability of the iron block to induce localized changes in material stiffness. A sponge block is placed at each end of the specimen, and alligator clips are attached to designated interfaces to establish a detachable connection. Mechanical impedance data at the electrodes are obtained using a Bode 100 impedance analyzer manufactured by OMICRON LAB.

[0045] Active ultrasonic sensing method: In order to demonstrate the tuning effect and self-sensing capability of the piezoelectric composite beam, an active ultrasonic sensing experimental device was designed. The excitation waveforms of three Hanning window modulated sinusoidal signals were generated using a Keysight 33500B arbitrary function generator. The excitation signals were further amplified to 150Vpp by a Krohn-Hite 7602M broadband power amplifier and applied in practice.

[0046] Example 1

[0047] This embodiment proposes a resin-based piezoelectric composite smart structural component, the preparation steps of which are as follows:

[0048] 1) Material Preparation and Mixing: Effectively disperse the PZT powder in the epoxy resin matrix. Use a vacuum pump to completely remove air bubbles from the mixture. This process aims to prevent voids in the structure during subsequent curing, thus avoiding breakdown during material polarization. This step is crucial because a uniformly dispersed powder and a bubble-free mixture ensure the material's density and electrical properties.

[0049] 2) Casting: The mixture is slowly poured into a mold with pre-laid glass fiber while being slowly and repeatedly heated with a blowtorch. This aims to further eliminate any air bubbles that may have been introduced during the injection process. Heating during injection encourages air bubbles to rise to the surface and escape rapidly, reducing the presence of bubbles that could affect structural integrity and electrical properties. This step helps ensure higher density and uniformity in the final composite material, improving its performance and reliability.

[0050] 3) Curing: Samples must be placed stably in an oven for a slow curing process. The curing stage should be carried out at a constant 60°C for 4 hours to ensure complete curing. Throughout the curing process, a dust-free working environment must be maintained to prevent particle deposition on the surface of the structure. This ensures that the subsequent silver screen printing process is not disturbed and guarantees the electrical properties and appearance quality of the final product. A dust-free environment is crucial for the success of the material's electrical properties and surface treatment and must therefore be strictly adhered to.

[0051] 4) Electrode Application: Since the material used is resin, it cannot withstand the high-temperature environment of traditional silver infiltration processes. Therefore, low-temperature silver paste was used for electrode printing at 110℃, followed by incubation at 60℃ for 45 minutes. To ensure effective subsequent polarization, special attention must be paid to ensuring the initial electrode covers the entire upper and lower surfaces of the sample to guarantee comprehensive polarization and achieve the desired electrical properties. This low-temperature silver paste printing process allows for electrode printing under temperature-limited conditions while maintaining material stability and performance.

[0052] 5) Polarization: The sample is placed in high-temperature polarization oil and polarized for 15 minutes using a 6kV voltage. The main purpose is to create an insulating environment, ensure a uniform electric field distribution, maintain temperature stability, prevent oxidation, and thus protect the sample, ensuring the effective polarization process. This step is to ensure the material obtains the required piezoelectric properties while preventing electric shock and arcing, ensuring operational safety and material quality.

[0053] 6) Processing: The sample undergoes rigorous processing to meet specific size requirements, and the necessary electrode areas are precisely preserved through laser etching. This step helps ensure that the sample has the required electrode structure while removing unnecessary parts, thereby achieving precise control and customized electrode design to meet the requirements of specific applications.

[0054] Figure 6 A beam-shaped structural specimen fabricated using piezoelectric composite material is presented. To enable voltage application and vibration driving in subsequent experiments, nine pairs of 10mm diameter circular electrodes were placed on the upper and lower surfaces of the beam. The spacing between adjacent electrodes was strictly controlled at 50mm. Each electrode can act as an individual excitation source to drive the beam. To ensure reliable application of external voltage to the electrodes, silver-layered leads were intentionally retained during electrode fabrication. These conductive leads allow for easy external connection, establishing a reliable electrical interface. Even if some lead connections are accidentally damaged, the connection can be quickly re-established using spare leads to maintain electrode operation. This design improves the structure's damage resistance and practicality. By carefully designing independently controlled electrode pairs on the piezoelectric composite beam structure, various distributed control experiments can be conducted. This design ensures the effectiveness of external voltage application and also possesses a certain degree of fault tolerance.

[0055] To verify the self-sensing integrated effect of the resin-based piezoelectric composite smart structure prepared in Example 1, simulation experiments based on the finite element simulation software ANSYS and physical sample experiments were conducted.

[0056] 1. Simulation Experiment:

[0057] Using the finite element simulation software ANSYS, based on the parameters of PZT4 piezoelectric ceramic material and in conjunction with glass fiber, the equivalent average parameter simulation method was used to simulate the piezoelectric composite smart material integrating load-bearing and self-sensing using the mechatronic impedance method and active ultrasonic sensing. The specific steps are as follows:

[0058] 1.2 Mechanical resistance impedance test: Ten pairs of electrodes were placed in the piezoelectric composite material, and simulated damage was created between electrodes 3 and 4 and between electrodes 9 and 10 by reducing stiffness. Figure 4As shown. Frequency sweep analysis was performed on the electrodes sequentially to obtain the spectra under damaged and undamaged conditions. The root mean square error coefficient (RMSE) was used to evaluate the location of the damage. The RSMD value was obtained through... Figure 5 The maximum RSMD value was normalized across all cases, and the RSMD value was used as an indicator of algorithm accuracy. A significant increase in RMSD value was observed at the electrode near the damage site. The presence of two separate damages resulted in the identification of two distinct RMSD peaks. These results demonstrate that the proposed piezoelectric composite sensor can successfully perform mechatronics techniques to detect and monitor the precise location of damage.

[0059] 1.3 Active Ultrasonic Sensing Experiment: A piezoelectric composite material was designed as a planar thin plate, with electrodes at both ends serving as actuation and sensing points. The effects of ultrasonic signals on different types of damage were investigated within this composite plate. By analyzing the transmission and reflection characteristics of ultrasonic signals, the material's actuation and sensing effects were studied. The results show that this material has the same effect as traditional active ultrasonic monitoring. Figure 9 As shown, the sensing signals received by the sensing electrodes initially all contain a small wave, i.e., an electromagnetic wave signal. The reason for this is that capacitors are formed on both the actuating electrode and the sensing electrode. Simultaneously with the application of the excitation signal, the electromagnetic wave travels at the speed of light to various areas of the thin plate, generating voltages across the capacitors. According to the capacitor formula:

[0060]

[0061] In the formula, C represents capacitance, Q represents charge, and U represents voltage, thus generating charge on the upper and lower surfaces of the actuating electrode. It can be observed that electromagnetic wave signals of the same magnitude appear regardless of whether there is damage or not. This further verifies that the generation of this wave packet is due to electromagnetic wave signal propagation, unrelated to damage, and does not belong to the category of ultrasonic guided waves. Simultaneously, compared to the undamaged condition, the amplitude of the ultrasonic wave in the damaged area is significantly attenuated and exhibits a slight phase shift, clearly reflecting the difference between the original and damaged structures. Furthermore, in the signals captured by the sensing electrodes, a reflected wave packet originating from damage reflection appears at the tail of the sensing signal when damage is present. This provides a feasible approach for ultrasonic-based damage detection, offers insights into related structural safety monitoring technologies, and is of great significance for promoting the further development of intelligent structural systems.

[0062] 2. Physical sample experiment:

[0063] The following steps were taken to prepare a piezoelectric composite smart material integrating load-bearing and self-sensing functions and to conduct real sample testing:

[0064] 2.1 Mechanical impedance method experiment: Simulated damage is set on the sample, and frequency sweep analysis is performed on the electrodes to obtain the spectrum under damaged and undamaged conditions. The root mean square error coefficient is used to evaluate the location of the simulated damage. The experimental setup is as follows: Figure 7 As shown, to assess localized structural damage, iron blocks were fixed to the sample surface to evaluate changes in the electrical impedance spectrum at the damaged site. The basic principle of using iron blocks to simulate damage is based on their ability to induce localized changes in material stiffness. Sponge blocks were placed at each end of the sample, and alligator clips were secured at designated interfaces to establish a detachable connection. Mechanical electrical impedance data at the electrodes were obtained using a Bode 100 impedance analyzer manufactured by OMICRONLAB. Figure 8 It is evident that the RMSD algorithm demonstrates exceptional capability in detecting impedance spectra from all electrodes, particularly regarding the impedance differences between the original and damaged scenes. Electrodes closer to the damaged area exhibit a significant increase in RMSD values. Of particular importance, electrode 3, located near the damaged area, was observed to cause the most significant resonance change.

[0065] 2.2 Active Ultrasonic Sensing Experiment: The piezoelectric composite smart material was used as the test plate, and an ultrasonic detection system was employed to analyze its motion and sensing effects, while simultaneously monitoring material damage. Test results show that the material exhibits good motion and sensing effects and can effectively detect the material's damage state. The experimental setup is as follows: Figure 11 As shown, a Keysight 33500B arbitrary waveform signal generator was used to generate a sinusoidal excitation signal modulated by a 3-cycle Hanning window. This signal was amplified to 175Vpp by a Krohn-hite 7602M broadband amplifier and applied to the actuating electrode on the piezoelectric composite beam. Under this excitation, the transmitting end excited the mechanical vibration of the piezoelectric composite structure, i.e., the formation of ultrasonic guided waves. These excited ultrasonic guided waves propagate along the beam and are detected by the receiving electrode, forming a corresponding sensing electrical signal. To ensure the stability of the experiment, sponges were placed at both ends of the beam for support. In addition, alligator clips were used for detachable connection of the electrodes, which avoids damage caused by welding and facilitates reconnection for different experiments. This connection method helps to avoid irreversible damage that may be caused by welding, ensuring the stability of the experiment and the integrity of the material. According to the experimental results... Figure 12Observations show that, compared with numerical simulation predictions, the response waveform of the damaged structure is significantly attenuated and its complexity increases compared to the original intact structure. Detailed analysis suggests this is due to the superposition of the incident excitation signal and the reflected signal from the damaged structure. When the incident symmetrical modal excitation signal is reflected from the damaged area, the reflected wave contains a strong symmetrical modal component. This reflected wave is superimposed on the incident excitation signal, leading to waveform distortion and attenuation. Furthermore, due to sample size limitations, non-reflective boundaries were not fully established around the sample, resulting in some reflection interference in the received signal. Therefore, this active sensing method is highly sensitive to localized structural damage and can effectively detect minute structural damage from changes in signal morphology, providing a potential technical means for non-destructive testing based on piezoelectric composite materials.

[0066] The above description represents a preferred embodiment of the present invention, but the present invention should not be limited to the content disclosed in this embodiment. Therefore, any equivalent or modified versions made without departing from the spirit of the present invention fall within the scope of protection of the present invention.

Claims

1. A resin-based piezoelectric composite smart material, characterized in that, It includes piezoelectric ceramic powder and resin, and also includes glass fiber, wherein the mass ratio of piezoelectric ceramic powder to resin is 5:1; The piezoelectric ceramic powder is PZT powder with a particle size of 120~200 mesh; The resin is epoxy resin; The resin-based piezoelectric composite smart material is obtained by a preparation method including the following steps: Step 1: Mix PZT powder and epoxy resin at a mass ratio of 5:1; Step 2: Slowly inject the mixture into the mold that has been laid with glass fiber, and remove air bubbles by vacuum treatment; Step 3: Place the mixture in the mold at a constant temperature of 60℃ for 4 hours to cure, and obtain the cured structural part; Step 4: The cured structural component is coated with polarized electrodes using silver wire mesh printing at a high temperature of 110°C for 45 minutes; Step 5: Polarize using a high-voltage amplifier immersed in oil at a voltage of 6 kV for 15 minutes; Step 6: The initial polarization electrode covers the entire upper and lower surfaces of the structural component and is then machined to the required dimensions; Step 7: Remove excess silver layer from the structure surface by laser engraving, retaining the electrode components.

2. The resin-based piezoelectric composite smart material according to claim 1, characterized in that, The epoxy resin is a mixture of HF-005 and HF-006.

3. The application of the resin-based piezoelectric composite smart material according to claim 1 or 2 in structural health monitoring, human-computer interaction and intelligent robot fabrication.

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