3-1 / 1-3 piezoelectric composite material and method for manufacturing the same

Abstract

The application discloses a 3-1 / 1-3 type piezoelectric composite material and a preparation method thereof. The 3-1 / 1-3 type piezoelectric composite material adopts a concentric cylinder configuration, and comprises a core functional layer of a cylindrical 3-1 type piezoelectric composite material and a peripheral coupling layer of a circular ring-shaped 1-3 type composite material. The core functional layer comprises a cylindrical first piezoelectric phase and a plurality of first polymer phases embedded in the first piezoelectric phase. The peripheral coupling layer comprises a circular ring-shaped second polymer phase and a plurality of second piezoelectric phases embedded in the second polymer phase. The thicknesses of the core functional layer and the peripheral coupling layer are equal, and an intermediate adhesive layer is further arranged between the core functional layer and the peripheral coupling layer. The ratio of the diameter of the core functional layer to the diameter of the peripheral coupling layer is between 0.4 and 0.7, thereby improving the bandwidth widening effect. The application utilizes the compatibility of the thickness vibration modes of the 1-3 type and 3-1 type composite materials, realizes the coupling transmission of vibration energy through structural integration, makes the two single-peak resonance peaks superimpose and widen each other, and finally forms a broadband response of the composite material.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric materials technology, and in particular to a 3-1 / 1-3 type piezoelectric composite material and its preparation method. Background Technology

[0002] In 1880, the Curie brothers discovered the piezoelectric effect, laying the foundation for research on piezoelectric materials, with natural crystals becoming the core research object in the early stages. However, the low piezoelectric coefficient and high difficulty in preparing natural crystals made them unsuitable for engineering applications. In the 1950s, the advent of zirconate titanate (PZT) piezoelectric ceramics sparked a revolution in the field of piezoelectric materials. Their high piezoelectric coefficient, high dielectric constant, and good mechanical stability allowed them to quickly replace natural crystals, becoming a core material in fields such as ultrasonic detection and medical imaging. As applications expand towards higher frequencies and wider bandwidths, the inherent defects of pure PZT ceramics have gradually become apparent.

[0003] First, multimodal vibration crosstalk is severe. When the operating frequency is close to the resonant frequency of the radial, transverse or bending modes, energy leakage will occur, resulting in decreased transducer sensitivity, waveform distortion and bandwidth limitation. Secondly, the high acoustic impedance results in poor impedance matching with human tissue or water, affecting energy transfer efficiency. Thirdly, ceramic materials are brittle and lack toughness, making them prone to fracture failure under complex working conditions. These defects severely restrict the application of piezoelectric ceramics in high-end fields such as broadband ultrasonic imaging and underwater detection.

[0004] To overcome the limitations of pure piezoelectric ceramics, Newnham et al. proposed the concept of piezoelectric composites in the late 1970s. Based on the connectivity between the piezoelectric and polymer phases, piezoelectric composites are composed of PZT piezoelectric ceramic phases and polymer phases arranged in a specific spatial geometric distribution with defined connectivity, volume, or weight. Common types of piezoelectric composites include 0-0, 0-1, 0-2, 0-3, 1-1, 1-2, 1-3, 2-2, 2-3, and 3-3 types. Among the numerous studies on piezoelectric composites, the 1-3 type is the most researched and applied. The 1-3 type piezoelectric composite consists of a one-dimensionally connected array of piezoelectric micropillars embedded in a three-dimensionally connected polymer matrix. This structure effectively reduces lateral constraint through the flexible support of the polymer phase, suppresses non-thickness vibration modes, significantly reduces acoustic impedance, and improves compatibility with the medium.

[0005] Type 3-1 piezoelectric composites have a complementary configuration to Type 1-3, consisting of a one-dimensionally connected array of polymer rods embedded in a three-dimensionally connected piezoelectric matrix. This structure retains the piezoelectric response of the piezoelectric matrix while reducing the acoustic impedance of the material through the introduction of the polymer phase. Its thickness vibration modes also exhibit good directionality. Similar to Type 1-3 materials, the properties of Type 3-1 composites can be controlled by adjusting parameters such as the volume fraction of the polymer phase, rod diameter, and spacing. However, its preparation process is more complex, and traditional methods greatly limit its industrial application. Figure 1 The diagram shows the structural schematics of two types of piezoelectric composite materials: type 1-3 and type 3-1. Figure 1 (a) shows a schematic diagram of the structure of a piezoelectric composite disc of type 1-3. Figure 1 (b) shows a schematic diagram of the structure of a polymer-filled 3-1 type piezoelectric composite disc.

[0006] Broadband piezoelectric materials, besides being prepared by adding pure piezoelectric ceramics to polymers to form piezoelectric composites, most commonly utilize multimode coupled vibration. Multimode coupled vibration can be achieved by adding an acoustic matching layer to the acoustic radiation surface of the piezoelectric material. This allows the piezoelectric material to couple with the matching layer during vibration, thus broadening the overall bandwidth of the material. However, the addition of the matching layer increases the load on the acoustic material, which can suppress its acoustic properties and reduce its acoustic radiation force. Another approach is to design piezoelectric composites of the same material with varying thicknesses for structural combinations. The different thicknesses result in different resonant frequencies, and the superposition of these different resonant frequencies broadens the acoustic bandwidth. However, the different thicknesses also lead to different acoustic radiation interfaces. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention aims to provide a 3-1 / 1-3 type piezoelectric composite material and its preparation method. This invention employs an integrated structure of the 3-1 / 1-3 type piezoelectric composite material, with the 1-3 type composite material serving as the outer coupling layer and the 3-1 type composite material as the core functional layer. Both materials have the same thickness. This coupling structure inherits the thickness vibration advantages of both materials, achieving significant bandwidth broadening through synergistic excitation and through the interaction of the thickness vibrations of the two materials. The core innovation of this design lies in utilizing the compatibility of the thickness vibration modes of the 1-3 and 3-1 type composite materials. Through structural integration, vibration energy is coupled and transferred, allowing the two single-peak resonance peaks to superimpose and broaden, ultimately forming the broadband response of the composite material.

[0008] To achieve the above objectives, the present invention provides a 3-1 / 1-3 type piezoelectric composite material. The 3-1 / 1-3 type piezoelectric composite material adopts a concentric cylindrical configuration, comprising a cylindrical 3-1 type piezoelectric composite material core functional layer and an annular 1-3 type composite material peripheral coupling layer. The core functional layer comprises a cylindrical first piezoelectric phase and a plurality of first polymer phases embedded in the first piezoelectric phase. The peripheral coupling layer comprises an annular second polymer phase and a plurality of second piezoelectric phases embedded in the second polymer phase. The core functional layer and the peripheral coupling layer have equal thicknesses, and an intermediate adhesive layer is provided between the core functional layer and the peripheral coupling layer. The ratio of the diameter of the core functional layer to the diameter of the peripheral coupling layer is between 0.4 and 0.7, preferably between 0.6 and 0.7, and particularly preferably 2 / 3, thereby improving the bandwidth broadening effect.

[0009] Furthermore, the first piezoelectric phase is provided with a plurality of cylindrical through holes, each first polymer phase being a cylinder adapted to the cylindrical through holes, the plurality of first polymer phases being evenly distributed, and the center-to-center distance between adjacent first polymer phases being equal.

[0010] Furthermore, the second piezoelectric phase is a cylindrical structure with a rectangular cross-section, and multiple second piezoelectric phases are evenly distributed around the circumference with the annular axis as the center.

[0011] Furthermore, multiple second piezoelectric phases are arranged in an inner and outer ring along the circumference, and the width of the rectangular cross-section of each second piezoelectric phase is perpendicular to the radial direction of the ring; the number of second piezoelectric phases in the outer ring is greater than the number of second piezoelectric phases in the inner ring.

[0012] Furthermore, the 3-1 / 1-3 type piezoelectric composite material has a total diameter of 30.5 mm, a thickness of 3 mm, a core functional layer diameter of 20 mm, and the materials of the first piezoelectric phase and the second piezoelectric phase are pure piezoelectric ceramics, the first polymer phase is silicone rubber, and the second polymer phase is epoxy resin.

[0013] Furthermore, the volume fraction of the first piezoelectric phase Volume fraction of the second piezoelectric phase .

[0014] Furthermore, the intermediate adhesive layer of the 3-1 / 1-3 type piezoelectric composite material is epoxy resin with a thickness of 0.25 mm.

[0015] On the other hand, the present invention provides a method for preparing a 3-1 / 1-3 type piezoelectric composite material, the method being used to prepare the 3-1 / 1-3 type piezoelectric composite material according to the present invention, the method comprising the following steps: S1. A first piezoelectric phase with multiple through holes in the core functional layer of a 3-1 type piezoelectric composite material is prepared using water-guided laser technology. The material of the first piezoelectric phase is pure piezoelectric ceramic. The pure piezoelectric ceramic is cut with water-guided laser technology to obtain through holes as filling positions of the first polymer phase. Silicone rubber, which is the material of the first polymer phase, is potted into the through holes and vacuum degassing is performed. Then, the silicone rubber that protrudes above the first piezoelectric phase is removed to prepare a cylindrical 3-1 type piezoelectric composite material core functional layer. S2. Use a cutting machine to cut pure piezoelectric ceramic sheets into cylinders with rectangular cross sections to prepare the second piezoelectric phase of the type 1-3 piezoelectric composite material. Use a 3D printer to print the frame of the second polymer phase of the type 1-3 piezoelectric composite material with epoxy resin material. The printing size ensures that the cut piezoelectric cylinders can be installed in the gaps of the frame. Use silicone rubber to bond the cut cylinders to the epoxy resin frame to prepare the outer coupling layer of the type 1-3 piezoelectric composite material. S3. The 3-1 type piezoelectric composite material is bonded to the 3-1 type piezoelectric composite material ring using epoxy resin to complete the preparation of the 3-1 / 1-3 type piezoelectric composite material coupling structure.

[0016] Furthermore, in step S1, the first piezoelectric phase after the through hole is drilled is ultrasonically cleaned to remove the dirt inside the through hole, and in step S2, the cut column is cleaned with ultrasound for later use.

[0017] The beneficial effects of this invention are as follows: This invention addresses the limitations of bandwidth and multimodal crosstalk in pure piezoelectric ceramics by studying the thickness vibration coupling mechanism and bandwidth broadening of 3-1 / 1-3 type piezoelectric composite materials. First, a theoretical model of thickness vibration for both materials was established, deriving the correlation formula between the resonant frequency and material parameters and structural dimensions, revealing the fundamental reason for the difference in resonant frequencies. Then, bandwidth broadening was achieved through double-peak coupling. COMSOL simulation verified the single-peak resonance characteristics of the single material and the double-peak superposition effect of the coupled structure, with a peak spacing of 120 kHz. Samples were prepared using water-guided laser and 3D printing technology. Test results showed that the peak frequencies of the 3-1 and 1-3 type single materials were 562.375 kHz and 455.5 kHz, respectively, with a peak spacing of 106.875 kHz after coupling. The relative errors between simulation and measurement were within a reasonable range. The study confirms that this coupling structure can inherit the advantages of thickness vibration of both materials, achieving significant bandwidth broadening through synergistic excitation. This provides new theoretical support and technical pathways for the design of broadband piezoelectric devices, and is of great significance for promoting their application in fields such as ultrasonic imaging and underwater detection. Attached Figure Description

[0018] Figure 1(a) is a schematic diagram of the structure of a piezoelectric composite material disc in the prior art; (b) is a schematic diagram of the structure of a type 1-3 piezoelectric composite material disc in the prior art; Figure 2 This is a schematic diagram of the structure of a 3-1 / 1-3 type piezoelectric composite material; Figure 3 The graphs show the relationship between the resonant frequency and the thickness of the two materials; (a) the relationship between the thickness and the resonant frequency of the 1-3 type piezoelectric composite material; (b) the relationship between the thickness and the resonant frequency of the 3-1 type piezoelectric composite material. Figure 4 This is a schematic diagram comparing the simulated conductivity spectra of the coupled structure and the single-component material; Figure 5 These are the mode shapes of a 3-1 / 1-3 type coupled structure and a single-component material; (a) 3-1 / 1-3 type model structure; (b) 3-1 / 1-3 type material coupled vibration; (c) 1-3 type material single-mode resonance; (d) 3-1 type material single-mode resonance; Figure 6 This is a process flow diagram for the fabrication of 3-1 / 1-3 type piezoelectric composite material coupling structures; Figure 7 This is a comparison of the conductivity spectra of 3-1 / 1-3 piezoelectric composite materials. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] The following combination Figures 2-7 Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the present invention.

[0023] The 3-1 / 1-3 type piezoelectric composite material according to the present invention comprises a 1-3 type composite material and a 3-1 type composite material formed as an integral structure, wherein the 1-3 type composite material serves as an outer coupling layer and the 3-1 type composite material serves as a core functional layer, and the outer coupling layer and the core functional layer have the same thickness. Bandwidth broadening is achieved through the interaction of the thickness vibration modes of the two materials. The core innovation of this design lies in utilizing the compatibility of the thickness vibration modes of the 1-3 and 3-1 type composite materials, achieving the coupling and transfer of vibrational energy through structural integration, causing the two single-peak resonance peaks to superimpose and broaden, ultimately forming a broadband response of the composite material.

[0024] Specifically, such as Figure 2 As shown, the 3-1 / 1-3 type piezoelectric composite material adopts a concentric cylindrical configuration, including a cylindrical 3-1 type piezoelectric composite core functional layer and a ring-shaped 1-3 type composite outer coupling layer. The core functional layer includes a cylindrical first piezoelectric phase and multiple first polymer phases. The first piezoelectric phase has multiple cylindrical through holes, and each first polymer phase is cylindrical with dimensions matching the cylindrical through holes. The multiple first polymer phases are evenly distributed, and the center-to-center distance between adjacent first polymer phases is equal. The outer coupling layer of the 1-3 type piezoelectric composite material includes a ring-shaped second polymer phase and multiple second piezoelectric phases. The second piezoelectric phase is a cylindrical structure with a rectangular cross-section. The multiple second piezoelectric phases are evenly distributed around the ring axis along the circumference, forming inner and outer rings. The width of the rectangular cross-section of each second piezoelectric phase is perpendicular to the radial direction of the ring. The number of second piezoelectric phases in the outer ring is greater than the number of second piezoelectric phases in the inner ring. An intermediate adhesive layer is also provided between the core functional layer and the outer coupling layer. Based on the theoretical research results and actual simulation verification obtained below, the diameter of the core functional layer in this invention is... With the diameter of the outer coupling layer Relationship satisfaction The optimal matching between the coupling area and the effective vibration area of ​​the outer coupling layer results in the largest coupling coefficient and the best bandwidth expansion effect.

[0025] Based on the above design principles, the present invention provides a specific embodiment, such as... Figure 2 As shown, the 3-1 / 1-3 type piezoelectric composite material of this embodiment has a cylindrical structure with a total diameter of The dimensions are 30.5 mm in diameter and 3 mm in thickness, specifically including the 3-1 type piezoelectric composite core functional layer, with a diameter of... The value is 20 mm, and its ratio basically satisfies To achieve optimal bandwidth broadening; the diameter of the first polymer phase is 1.3 mm, and the center-to-center spacing is 0.85 mm, where the center-to-center spacing refers to the minimum distance between adjacent outer surfaces of the first polymer; the first polymer phases are arranged in a cylindrical shape, and the volume fraction of the first piezoelectric phase is... Volume fraction of the first polymer phase The 1-3 type piezoelectric composite material serves as the outer coupling layer, with a ring width of 5 mm. The second piezoelectric phase has a side length of 2 mm, a height of 3 mm, and a spacing of 0.5 mm (the spacing is the difference between the distance from the midpoint of the innermost width of the outer rectangle to the central axis and the distance from the midpoint of the outermost width of the inner rectangle to the central axis), uniformly distributed along the circumference. The volume fraction of the second piezoelectric phase... Second polymer phase The thickness of the intermediate adhesive layer in the 3-1 / 1-3 type coupling structure is 0.25 mm. The above are the optimal results of the example data, which can be adjusted according to the proportion of ceramics. The side length of the small column ranges from 0.5 mm to 4 mm, and the height ranges from 0.5 mm to 10 mm.

[0026] The main objectives of this invention are as follows: First, to establish a theoretical model of thickness vibration of type 1-3 and type 3-1 piezoelectric composite materials, and derive the calculation formulas for key parameters such as resonant frequency and electromechanical coupling coefficient; Second, to reveal the coupling mechanism of thickness vibration of the two materials, derive the theoretical formula for bandwidth broadening of the coupling system, and clarify the influence of structural parameters on the coupling effect.

[0027] Third, finite element simulations were performed using COMSOL to analyze the thickness resonant frequency ranges of the two materials. A broadband range was selected to analyze the vibration modes, impedance characteristics, and coupling mechanism of the coupled structure, verifying the effectiveness of the theoretical model. Fourth, type 1-3 composite materials were prepared using photopolymerization 3D printing technology, and type 3-1 composite materials were processed using water-guided laser technology. Integrated structural assembly and performance testing were completed, verifying the bandwidth broadening effect. The significance of this invention lies in: proposing a novel piezoelectric composite material coupling structure, providing a new approach for the design of broadband piezoelectric devices; the established coupled vibration theoretical model can provide theoretical support for the collaborative design of multi-configuration piezoelectric composite materials; and the developed fabrication process provides a technical reference for the high-precision processing of type 3-1 / 1-3 piezoelectric composite materials.

[0028] The structural design research process of the 3-1 / 1-3 type piezoelectric composite material of the present invention is as follows: (1) Determine the thickness vibration mechanism of type 1-3 piezoelectric composite materials.

[0029] Thickness vibration of type 1-3 piezoelectric composites refers to the stretching vibration of the material in the Z-axis of thickness. When an electric field is applied along the Z-axis, the piezoelectric pillars deform in the thickness direction under the inverse piezoelectric effect, which in turn drives the polymer matrix to vibrate in tandem. Since the lateral constraint of the polymer phase is much smaller than that of the piezoelectric phase, the vibration of the composite material is mainly concentrated in the thickness direction, and lateral vibration is effectively suppressed. Type 1-3 composites consist of a second piezoelectric phase and a second polymer phase. The mass per unit volume of the type 1-3 composite material is equal to the sum of the masses of the two phases, i.e., the effective density of the material. for:

[0030] in, The volume fraction of the piezoelectric phase. This represents the volume fraction of the polymer phase. The piezoelectric phase volume density, ρ is the bulk density of the polymer phase.

[0031] Considering the one-dimensional stress state in the Z-direction of thickness, the macroscopic stress of the composite material With macroscopic strain Satisfies Hooke's Law:

[0032] Due to the coordinated deformation of the second piezoelectric phase and the second polymer phase, the strain satisfies:

[0033] In the equation: ε represents strain, which is the relative deformation of the material.

[0034] The subscript z indicates the component along the z-direction.

[0035] The superscript P represents the piezoelectric ceramic component in the composite material.

[0036] The superscript R represents the polymer matrix component in the composite material.

[0037] The subscript 1-3 represents type 1-3 piezoelectric composite material, which refers to a structure in which the piezoelectric phase is arranged in a one-dimensional columnar shape and the polymer phase is three-dimensionally interconnected.

[0038] The stress satisfies the equilibrium condition:

[0039] Stress represents the force exerted per unit area.

[0040] : The stress of the entire piezoelectric composite material of type 1-3 in the z direction.

[0041] : Stress of the second piezoelectric phase in the z-direction.

[0042] : Stress of the second polymer phase in the z-direction.

[0043] A: Total cross-sectional area of ​​the composite material.

[0044] : Cross-sectional area of ​​the second piezoelectric phase.

[0045] : Cross-sectional area of ​​the second polymer phase.

[0046] in, This represents the total cross-sectional area. And... , .

[0047] Combining (2), (3), and (4), the effective elastic modulus can be obtained as:

[0048] Effective elastic modulus in the z-direction of type 1-3 piezoelectric composite materials Volume fraction of piezoelectric phase Volume fraction of polymer phase Elastic modulus of piezoelectric phase Elastic modulus of polymer phase The speed of sound is a key physical quantity connecting material parameters and resonant frequency. The elastic wave equation in the thickness direction is:

[0049] Displacement in the z-direction; the vibrational displacement of a material particle in the z-direction. t: time Effective acoustic velocity, the propagation speed of elastic waves in composite materials. z: Coordinate in the thickness direction The displacement in the Z direction is the effective acoustic velocity. According to the definition of elastic wave propagation speed, acoustic speed With material density Elastic modulus The relationship is: Therefore, combining (1) and (5), the effective acoustic velocity satisfies:

[0050] and , Therefore, (8) can be transformed into a form in which the effective sound velocity is related to the volume fraction of the two phases.

[0051]

[0052] The resonant frequency of thickness vibration in type 1-3 piezoelectric composite materials is essentially the eigenfrequency of the elastic wave satisfying boundary conditions in a finite-thickness medium. For a thickness of... The upper and lower surfaces of the material are and The location is a free surface with zero stress. , Under initial conditions At time t, the initial displacement of the fundamental frequency initial velocity Therefore, the general solution to the wave equation (7) can be obtained:

[0053] in, For wave number, Angular frequency, , , is an undetermined constant.

[0054] lower surface The positional stress is zero. Substituting into the general solution (10), we get:

[0055] The general solution (10) simplifies to:

[0056] upper surface The stress is zero. ,because and If they are not both zero, then:

[0057] Will ,and Substitution ,have to:

[0058] After simplification, the general formula for the thickness resonant frequency is obtained:

[0059] When n=1, the main operating mode of thickness vibration is the fundamental resonant frequency:

[0060] Substituting the effective acoustic velocity formula (8) into (15), we finally obtain the complete correlation between the fundamental resonant frequency and the material parameters and dimensions:

[0061] Or equivalent form:

[0062] Formula (17) clarifies the resonant frequency and thickness of type 1-3 piezoelectric composite materials. They are inversely proportional, which is a direct means of controlling the resonant frequency in material design; secondly, the elastic modulus of the piezoelectric phase... ,density and acoustic velocity Directly determines the effective acoustic velocity. The bigger, The smaller, The higher the value, the higher the resonant frequency; it also changes... The resonant frequency can be adjusted.

[0063] In the design of 1-3 / 3-1 type piezoelectric composite materials, the ratio of thickness d to diameter D is determined by two core requirements: suppressing transverse vibration and ensuring thickness vibration dominance, as well as structural stability and process feasibility. At this time, the influence of lateral vibration can be effectively suppressed, and the material vibrates mainly in a thickness expansion and contraction mode, ensuring the stability and purity of the resonant frequency. This is a classic industry experience value. A larger diameter is not necessarily better. Excessive ratios can lead to decreased bending strength of the material, increased susceptibility to deformation or fracture during processing and assembly, difficulty in ensuring uniform piezoelectric phase distribution, reduced effective performance, and a significant increase in the overall size and weight of the transducer, which is detrimental to engineering applications. Therefore, the optimal ratio range in engineering is between 10 and 15 times, which ensures that thickness vibration dominates while balancing structural stability and process feasibility.

[0064] piezoelectric phase volume fraction The electromechanical coupling coefficient and transmit / receive sensitivity of the transducer are directly determined, and a performance balance must be considered; when At that time, due to the low proportion of polymer phase, the material's flexibility decreases and its broadband properties deteriorate; when At this time, the electromechanical coupling coefficient is insufficient, and the energy conversion efficiency is significantly reduced. The optimal range is: type 1-3 materials. 3-1 type material This range allows for an optimal balance between electromechanical performance and broadband characteristics. Polymer phase volume fraction. satisfy It primarily provides flexibility and damping to the material to broaden the frequency band, and usually does not need to be selected independently; it is determined based on the target. Confirmation is sufficient. Piezoelectric phase density. Choose mature piezoelectric ceramics, such as PZT-5H. Its density is a fixed material property; polymer phase density Low-density types, such as epoxy resin, are preferred. silicone rubber To reduce the effective density and increase the acoustic velocity. Once the material is selected, its density is fixed. During the design phase, the effective density is optimized by adjusting the volume fraction to satisfy: .

[0065] (2) Determine the thickness vibration mechanism of the 3-1 type piezoelectric composite material.

[0066] The thickness vibration mechanism of the 3-1 type piezoelectric composite material is similar to that of the 1-3 type, but its first piezoelectric phase is a three-dimensionally connected matrix, and the first polymer phase is a one-dimensionally connected rod-like structure (also called a polymer rod). When an electric field is applied along the thickness direction, the piezoelectric matrix undergoes thickness-direction expansion and contraction, and the polymer rod vibrates in tandem with the matrix due to its bonding with the interface. Due to the flexible characteristics of the first polymer phase, its lateral constraint on the matrix is ​​weak, ensuring the dominance of thickness vibration.

[0067] The volume fraction of the piezoelectric matrix. , The volume fraction of the polymer rod is denoted as . The piezoelectric substrate is a continuous phase, and the polymer phase is a dispersed phase. The effective elastic modulus is similar to that of formula (5), and still satisfies:

[0068] Effective density: Consistent with the derivation logic of types 1-3, it is:

[0069] Effective acoustic velocity:

[0070] Unlike type 1-3 materials, the piezoelectric matrix continuity of type 3-1 composites makes their effective elastic modulus closer to that of pure piezoelectric ceramics. Therefore, under the same first polymer phase volume fraction, The corresponding resonant frequency is also higher.

[0071] Using the same boundary conditions as wave equation (7), the fundamental resonant frequency of the 3-1 type composite material is obtained:

[0072] Formula (21) clarifies that the resonant frequency characteristics of the 3-1 type piezoelectric composite material are the same as those of the 1-3 type piezoelectric composite material. The essential difference lies in the structural size sensitivity. The diameter of the first polymer phase in the 3-1 type is... Spacing It will affect the lateral constraint strength, when When, lateral constraints can be ignored; when At this time, a horizontal correction factor needs to be introduced. At this point, the effective elastic modulus is corrected to The resonant frequency decreases accordingly. Because Therefore, under the same material thickness, the resonant frequency of the 3-1 type composite material is... Materials higher than type 1-3 This provides a structural basis for the superposition of two resonance peaks when the two are coupled. The optimal ratio of the diameter to the spacing of the first polymer phase in the 3-1 type is 1.53.

[0073] (3) Determine the resonant frequency coupling mechanism of the 3-1 / 1-3 coupling structure.

[0074] The resonant frequency of the 3-1 / 1-3 type coupled structure is not a simple superposition of the resonant frequencies of two single materials, but rather a new coupled resonant frequency is formed through interfacial mechanical coupling. The derivation based on a two-degree-of-freedom vibration system is as follows: Assume the mass of the outer ring of type 1-3 Stiffness The quality of the 3-1 type core layer Stiffness Interface coupling stiffness , The elastic modulus of the adhesive layer, The coupling area is... This represents the thickness of the adhesive layer.

[0075] The dynamic equations of a two-degree-of-freedom coupled system are:

[0076] in, , Driven by the electric field, For the applied electric field strength, , Let be the z-direction displacement of the two systems.

[0077] Let the steady-state response be , Substituting into the dynamic equation (22), we get:

[0078] The condition for system (23) to have a non-zero solution is that the determinant of the coefficient row is zero:

[0079] Expanding the determinant yields the frequency equation:

[0080] Let the natural angular frequency of a single material be... , Introducing coupling coefficient , representing the resonant coupling strength between the two materials, the frequency equation can be simplified to:

[0081] Solving (25) yields the two coupled resonant angular frequencies. and The corresponding coupled resonant frequency is: .

[0082] Coupled resonance peak spacing With coupling coefficient Positive correlation The larger the elastic modulus of the adhesive layer, the greater the elastic modulus. Larger, coupling area Larger, thicker adhesive layer The smaller, The larger the bandwidth, the more significant the bandwidth expansion effect; when At that time, the two resonance peaks completely merged, forming a single broad peak, but the broadband effect was consistent with the broadband effect of the material. and When the difference is too large, peak separation is obvious, which may also lead to a decrease in the response amplitude between the two peaks, preventing the formation of an effective broadband and affecting the coupled resonance performance of the material. Coupling coefficient The diameter of the core functional layer is positively correlated with the interface bonding strength and contact area. Ring width with outer coupling layer Determine the coupling area ,when , The total diameter, also known as the diameter of the outer coupling layer, and the coupling area. The optimal matching between the effective vibration area and the outer coupling layer, and the coupling coefficient Maximum bandwidth expansion is achieved. In the 3-1 / 1-3 coupling structure, the adhesive layer design should focus on improving the coupling coefficient. High elastic modulus and good interface compatibility should be prioritized for adhesive materials. The thickness should be controlled to the minimum within the allowable range of the process, while ensuring that the area of ​​the adhesive layer is completely matched with the optimal coupling area. Surface treatment is used to improve the interfacial bonding strength, and high-precision processes are used to ensure the uniformity of thickness and area, so as to achieve the best broadband resonant response.

[0083] (4) Simulation and calculation of type 3-1 piezoelectric composite material A finite element model of a 3-1 / 1-3 coupled structure was established using COMSOL. Combining multiphysics interfaces of electrostatics, solid mechanics, and piezoelectric effect, the electrical characteristics of the material and its thickness-coupled vibrations were simulated. Based on the study of the thickness vibration mechanisms and coupling mechanisms of the two materials, a [further details needed]. Figure 2 The optimal coupling structure model of the 3-1 / 1-3 type piezoelectric composite material is shown.

[0084] The coupling structure adopts a concentric cylindrical configuration with a total diameter of 30.5 mm and a thickness of 3 mm. Specific dimensions include a 3-1 type piezoelectric composite core layer with a diameter of 20 mm, a polymer phase with a diameter of 1.3 mm, and a center-to-center spacing of 0.85 mm, arranged in a cylindrical shape. The piezoelectric phase volume fraction... , Type 1-3 piezoelectric composite material forms the outer layer, with a ring width of 5 mm. The piezoelectric phase has a width of 2 mm, a length of 3 mm, and a spacing of 0.5 mm, uniformly distributed along the circumference. The volume fraction of the piezoelectric phase is... polymer phase The thickness of the intermediate adhesive layer in the 3-1 / 1-3 type coupling structure is 0.25 mm.

[0085] Based on the study of the thickness vibration mechanism of type 1-3 and type 3-1 piezoelectric composite materials and Figure 2 The coupling configurations of the two materials were simulated, and the relationship between the thickness of the two materials and the resonant frequency was investigated. In the relevant material parameter settings, PZT-5H was selected as the piezoelectric phase, and 3D-printed photocurable epoxy resin was selected as the polymer phase. The piezoelectric pillars of the type 1-3 piezoelectric composite material were bonded to the resin framework with silicone rubber, so the piezoelectric pillars were surrounded by silicone rubber. Figure 3 The figure shows the resonant frequencies of two materials with thicknesses ranging from 1 mm to 10 mm, simulated separately. Figure 3 (a) shows the relationship between the thickness and resonant frequency of piezoelectric composite materials of types 1-3. Figure 3 (b) shows the relationship between the thickness and resonant frequency of the 3-1 type piezoelectric composite material. The simulation results show that, for the same material thickness, the resonant frequency of the 1-3 type piezoelectric composite material is lower than that of the 3-1 type piezoelectric composite material. This is consistent with the results analyzed in formulas (16) and (21).

[0086] Epoxy resin was used as the bonding layer between the two materials to analyze the coupled vibration modes of the two materials. The frequency sweep range set for the simulation was 100 kHz to 1 MHz. Figure 4 A comparison of the conductivity spectra of the coupled structure and the single-component material in simulations. Figure 2 It can be seen that the conductivity spectra of the type 1-3 single materials exhibit a single-peak characteristic with a resonance frequency of 420 kHz. The type 3-1 single material also exhibits a single-peak characteristic with a resonance frequency of 540 kHz. The conductivity spectra of the coupled structure show a clear double-peak superposition characteristic, with the two resonance peaks located at 420 kHz and 540 kHz, respectively, and a peak spacing of 120 kHz, verifying the effectiveness of the coupling mechanism.

[0087] Figure 5 shows the thickness vibration modes of the coupled structure at different frequencies. Figure 5(a) shows the simulated model structure. Figure 5 (b) shows that at 480 kHz, both the core and outer layers exhibit significant vibrations, indicating effective coupling between them. Vibrational energy is transferred through the epoxy resin adhesive layer, forming a coupled resonance mode. Figure 5(c) shows that at 420 kHz, the vibration is mainly concentrated in the outer 1-3 type layer, exhibiting a ring-shaped thickness expansion mode, while the inner 3-1 type layer shows smaller displacement, indicating a single-mode resonance of the 1-3 type material. Figure 5(d) shows that at 540 kHz, the dominant vibration region shifts to the 3-1 type inner layer, exhibiting uniform axial expansion, corresponding to a single-mode resonance of the 3-1 type material. The mode shape results indicate that the coupled model, located between the peak frequencies of the two materials, can achieve more efficient coupled vibration.

[0088] The preparation method of the 3-1 / 1-3 type piezoelectric composite material according to the present invention is as follows: like Figure 6 This is a process flow diagram for the fabrication of a 3-1 / 1-3 type piezoelectric composite material coupling structure. (See diagram for example.) Figure 6 As shown, the method of the present invention includes the following steps: S1. A first piezoelectric phase with multiple through-holes in the core functional layer of a type 3-1 piezoelectric composite material was prepared using water-guided laser technology. The first piezoelectric phase was made of pure piezoelectric ceramic. The introduction of water flow during water-guided laser cutting effectively reduced thermal damage and improved the surface quality of the cut material, making it ideal for fine processing of high-hardness, brittle materials. First, water-guided laser cutting was used to create through-holes in the pure piezoelectric ceramic, which served as filling locations for the polymer. The material with the through-holes was then ultrasonically cleaned to remove contaminants from the pores. Next, silicone rubber, serving as the first polymer phase, was potted into the pores and vacuum degassing was performed. The excess silicone rubber was then removed to ensure the smoothness of the entire material surface. Finally, a cylindrical core functional layer of the type 3-1 piezoelectric composite material was prepared.

[0089] S2. Using a cutting machine, pure piezoelectric ceramic sheets are cut into cylinders with rectangular cross-sections (also called piezoelectric micropillars) to prepare the second piezoelectric phase of the type 1-3 piezoelectric composite material. The piezoelectric micropillars are then ultrasonically cleaned for later use. 3D printing technology provides a new approach to the preparation of piezoelectric composite materials, allowing for flexible adjustment of the frame shape and the distribution of the second piezoelectric phase. A 3D printer is used to print the frame of the second polymer phase of the type 1-3 piezoelectric composite material using resin material. The printing dimensions ensure that the cut piezoelectric micropillars can be precisely installed into the gaps in the frame. Silicone is used to bond the cut piezoelectric micropillars to the resin frame, preparing the outer coupling layer of the type 1-3 piezoelectric composite material.

[0090] S3. The 3-1 type piezoelectric composite material is bonded to the 3-1 type piezoelectric composite material ring using epoxy resin to complete the preparation of the 3-1 / 1-3 type piezoelectric composite material coupling structure.

[0091] The preparation process of the piezoelectric composite material coupling structure also includes cleaning, degreasing and roughening the surface of the piezoelectric composite material to be plated, drying it and then uniformly coating the target surface with silver paste by screen printing, scraping or spraying. Then, it is placed in an 80℃ oven and gradually heated and cured for 4 hours according to the silver paste process requirements. After cooling, the conductivity and adhesion of the electrode are tested. If necessary, the coating-curing process is repeated to optimize the electrode performance.

[0092] According to the fabrication process of the coupling structure of the 3-1 / 1-3 type piezoelectric composite material, the prepared sample was subjected to frequency scanning in the range of 100 kHz to 1000 kHz. The results are as follows: Figure 7 The conductivity spectrum comparison diagram is shown. Figure 7 Curve 2 represents the electrical conductivity of the 3-1 type piezoelectric composite material, exhibiting a single-peak mode with a peak frequency of 562.375 kHz. Figure 4 The simulated peak frequency is 540 kHz. Curve 4 shows the conductivity of the type 1-3 piezoelectric composite material, exhibiting a single-peak shape with a peak frequency of 455.5 kHz. Figure 4 The simulated peak frequency is 420 kHz. Curve 6 shows the conductivity spectrum after coupling of the two materials. The test results show the double-peak coupling effect of the surface line, and the two peaks are the same as those of the single material test. The broadband range covers a peak spacing of 106.875 kHz, while the simulated peak spacing is 120 kHz. The relative error of the peak frequency of the 3-1 type piezoelectric composite material is about 3.98%, and the relative error of the peak frequency of the 1-3 type piezoelectric composite material is about 7.79%. The relative error of the peak spacing after coupling is 12.27%. The overall error is within a reasonable range, which is due to the simplification of material parameters in the ideal simulation model. This error level is consistent with the conventional results of comparing the simulation and experiment of piezoelectric composite materials, verifying the reliability of the model and the validity of the experimental data.

[0093] For 3-1 type or 3-1 type piezoelectric composite materials, both simulation and field measurements demonstrate a significant single-peak thickness resonance characteristic in conductivity at specific frequencies. This indicates that the composite material primarily exhibits thickness vibration at resonance, while the transversely coupled vibration modes are effectively suppressed. Experiments have proven the reliability of fabricating these two materials using water-conducting laser cutting and 3D printing technologies, as well as the feasibility of broadening the bandwidth of coupled thickness vibrations between the two materials.

[0094] This paper addresses the limitations of bandwidth and multimodal crosstalk in pure piezoelectric ceramics by investigating the thickness vibration coupling mechanism and bandwidth broadening of 3-1 / 1-3 type piezoelectric composite materials. First, a theoretical model of thickness vibration for both materials was established, deriving the correlation formula between the resonant frequency and material parameters and structural dimensions. The fundamental reason for the difference in resonant frequencies between the two materials was revealed. Then, bandwidth broadening was achieved through double-peak coupling. COMSOL simulation verified the single-peak resonance characteristics of the single material and the double-peak superposition effect of the coupled structure, with a peak spacing of 120 kHz. Samples were prepared using water-guided laser and 3D printing technology. Test results showed that the peak frequencies of the 3-1 and 1-3 type single materials were 562.375 kHz and 455.5 kHz, respectively, with a peak spacing of 106.875 kHz after coupling. The relative errors between simulation and measurement were within a reasonable range. This study confirms that the coupling structure can inherit the advantages of thickness vibration of both materials, achieving significant bandwidth broadening through synergistic excitation. This provides new theoretical support and technical pathways for the design of broadband piezoelectric devices, and is of great significance for promoting their application in fields such as ultrasonic imaging and underwater detection.

[0095] Any process or method described in the flowcharts of this invention or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, which can be implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device. The computer-readable medium can be any medium containing a program for storage, communication, propagation, or transmission for use by the execution system, apparatus, or device, including read-only memory, magnetic disks, or optical disks.

[0096] In the description of this specification, references to terms such as "embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, those skilled in the art can combine or combine the different embodiments or examples described in this specification and the features therein without causing contradiction.

[0097] While embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and alterations to the above embodiments within the scope of the present invention.

Claims

1. A 3-1 / 1-3 type piezoelectric composite material, characterized in that, The 3-1 / 1-3 type piezoelectric composite material adopts a concentric cylindrical configuration, including a cylindrical 3-1 type piezoelectric composite core functional layer and an annular 1-3 type composite outer coupling layer. The core functional layer includes a cylindrical first piezoelectric phase and multiple first polymer phases embedded in the first piezoelectric phase. The outer coupling layer includes an annular second polymer phase and multiple second piezoelectric phases embedded in the second polymer phase. The core functional layer and the outer coupling layer have equal thicknesses, and an intermediate adhesive layer is provided between the core functional layer and the outer coupling layer. The ratio of the diameter of the core functional layer to the diameter of the outer coupling layer is between 0.4 and 0.7, thereby improving the bandwidth broadening effect. The volume fraction of the first piezoelectric phase... The volume fraction of the second piezoelectric phase is between 0.4 and 0.

7. between.

2. The 3-1 / 1-3 type piezoelectric composite material according to claim 1, characterized in that, The first piezoelectric phase is provided with multiple cylindrical through holes, and each first polymer phase is a cylinder adapted to the cylindrical through hole. The multiple first polymer phases are evenly distributed, and the center-to-center distance between adjacent first polymer phases is equal.

3. The 3-1 / 1-3 type piezoelectric composite material according to claim 2, characterized in that, The second piezoelectric phase is a cylindrical structure with a rectangular cross-section, and multiple second piezoelectric phases are evenly distributed around the circumference with the ring axis as the center.

4. The 3-1 / 1-3 type piezoelectric composite material according to claim 3, characterized in that, Multiple second piezoelectric phases are arranged in an inner and outer ring along the circumference. The width of the rectangular cross-section of each second piezoelectric phase is perpendicular to the radial direction of the ring. The number of second piezoelectric phases in the outer ring is greater than the number of second piezoelectric phases in the inner ring.

5. The 3-1 / 1-3 type piezoelectric composite material according to claim 1, characterized in that, The first and second piezoelectric phases are made of pure piezoelectric ceramics, the first polymer phase is silicone rubber, and the second polymer phase is epoxy resin.

6. The 3-1 / 1-3 type piezoelectric composite material according to any one of claims 1-5, characterized in that, The ratio of the diameter of the core functional layer to the diameter of the outer coupling layer is 2 / 3.

7. The 3-1 / 1-3 type piezoelectric composite material according to claim 1, characterized in that, The intermediate adhesive layer of the 3-1 / 1-3 type piezoelectric composite material is epoxy resin with a thickness of 0.25 mm.

8. A method for preparing a 3-1 / 1-3 type piezoelectric composite material, characterized in that, The method is used to prepare the 3-1 / 1-3 type piezoelectric composite material according to any one of claims 1-7, and the method includes the following steps: S1. A first piezoelectric phase with multiple through holes in the core functional layer of a 3-1 type piezoelectric composite material is prepared using water-guided laser technology. The material of the first piezoelectric phase is pure piezoelectric ceramic. The pure piezoelectric ceramic is cut with water-guided laser technology to obtain through holes as filling positions of the first polymer phase. Silicone rubber, which is the material of the first polymer phase, is potted into the through holes and vacuum degassing is performed. Then, the silicone rubber that protrudes above the first piezoelectric phase is removed to prepare a cylindrical 3-1 type piezoelectric composite material core functional layer. S2. Use a cutting machine to cut pure piezoelectric ceramic sheets into cylinders with rectangular cross sections to prepare the second piezoelectric phase of the type 1-3 piezoelectric composite material. Use a 3D printer to print the frame of the second polymer phase of the type 1-3 piezoelectric composite material with epoxy resin material. The printing size ensures that the cut piezoelectric cylinders can be installed in the gaps of the frame. Use silicone rubber to bond the cut cylinders to the epoxy resin frame to prepare the outer coupling layer of the type 1-3 piezoelectric composite material. S3. The 3-1 type piezoelectric composite material is bonded to the 3-1 type piezoelectric composite material ring using epoxy resin to complete the preparation of the 3-1 / 1-3 type piezoelectric composite material coupling structure.

9. The method for preparing the 3-1 / 1-3 type piezoelectric composite material according to claim 8, characterized in that, In step S1, the first piezoelectric phase after the through hole is drilled is ultrasonically cleaned to remove the dirt inside the through hole. In step S2, the cut column is cleaned with ultrasound for later use.

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