Piezoelectric sensing network for structural health monitoring and preparation method and application thereof

Abstract

The invention relates to a piezoelectric sensing network for structural health monitoring and a preparation method and application thereof, the piezoelectric sensing network comprises a plurality of array elements, each array element comprises a lower insulating layer and an upper insulating layer which are sequentially arranged on the surface of a monitored structure, and a piezoelectric layer and an electrode layer are clamped between the lower insulating layer and the upper insulating layer. The electrode layer extends out of an array element for realizing electric connection between the piezoelectric layer and an external circuit; wherein the array elements are arranged along the edge of the monitored structure, the distance d between the adjacent array elements is larger than or equal to 3.0 cm and smaller than or equal to 5.0 cm, and the minimum vertical distance l between the array elements and the edge of the monitored structure is larger than or equal to 2.0 cm and smaller than or equal to 5.0 cm. The piezoelectric sensing network can be prepared by adopting an aerosol printing technology, and the prepared piezoelectric sensing network can be conformally attached to a curved surface structure or a variable cross-section structure, is highly compatible with a monitored structure, is high in monitoring sensitivity, and can monitor and evaluate the health state of the sonar structure in real time when being used for the sonar structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a piezoelectric sensing network for structural health monitoring and a preparation method and application thereof. BACKGROUND

[0002] Deep-sea imaging sonar is an important device for detecting ocean topography, biology and resources. The pressure-resistant shell structure of the system is subjected to high pressure load, corrosion medium erosion and complex fluid mechanics in deep-sea environment, resulting in serious challenges to the structural health. However, there are relatively few studies on the structural health monitoring (SHM) of sonar. The traditional health monitoring of sonar structure mainly relies on periodic maintenance and offline detection, which has the problems of poor real-time performance, low monitoring accuracy and high cost, and it is difficult to ensure the long-term stable operation of the sonar. Therefore, it is of great significance to develop a sonar structure monitoring technology which is highly compatible with the sonar structure and highly sensitive to damage, to realize real-time monitoring and evaluation of the structural health state of deep-sea imaging sonar, and to find potential damage in time, so as to ensure the safe operation of the equipment and prolong the service life. SUMMARY

[0003] Therefore, it is necessary to provide a piezoelectric sensing network for structural health monitoring and a preparation method and application thereof, which can be highly compatible with the surface of the monitored structure and has high monitoring sensitivity, so as to realize real-time monitoring and evaluation of the health state of the sonar structure.

[0004] A piezoelectric sensing network for structural health monitoring, comprising a plurality of array elements, each array element comprising a lower insulating layer and an upper insulating layer arranged in sequence on the surface of a monitored structure, a piezoelectric layer and an electrode layer being arranged between the lower insulating layer and the upper insulating layer, the electrode layer extending out of the array element for electrically connecting the piezoelectric layer to an external circuit.

[0005] In one embodiment, the array elements are arranged along the edge of the monitored structure with an equal interval, and the interval d between adjacent array elements satisfies 3.0 cm≤d≤5.0 cm, and the minimum vertical distance l from the array element to the edge of the monitored structure satisfies 2.0 cm≤l≤5.0 cm.

[0006] In one embodiment, the array elements are arranged along the edge of the monitored structure with an equal interval, and the interval d between adjacent array elements satisfies 3.0 cm≤d≤5.0 cm, and the minimum vertical distance l from the array element to the edge of the monitored structure satisfies 2.0 cm≤l≤5.0 cm.

[0007] In one embodiment, the thickness of the upper insulating layer and the lower insulating layer is independently selected from 5 μm to 10 μm.

[0008] In one embodiment, the thickness of the piezoelectric layer is 1.0 μm to 2.0 μm.

[0009] And / or, the thickness of the electrode layer is 100nm-300nm.

[0010] In one embodiment, the length of the piezoelectric layer is 2.0cm-4.0cm, and the width is 0.5cm-1.0cm.

[0011] And / or, the length of the electrode layer is equal to the length of the piezoelectric layer, and the width of the electrode layer is 0.10cm-0.20cm.

[0012] And / or, the length and width of the upper and lower insulating layers are greater than or equal to the piezoelectric layer.

[0013] In one embodiment, the piezoelectric layer is selected from at least one of a piezoelectric composite layer of lead zirconate titanate nanoparticles and polyvinylidene fluoride-trifluoroethylene or a polyvinylidene fluoride-trifluoroethylene layer, wherein the volume ratio of lead zirconate titanate nanoparticles to polyvinylidene fluoride-trifluoroethylene in the piezoelectric composite layer is 4:6-6:4.

[0014] And / or, the upper and lower insulating layers are independently selected from at least one of an epoxy resin layer or a polydimethylsiloxane layer.

[0015] And / or, the electrode layer is selected from at least one of a silver layer or a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate layer.

[0016] In one embodiment, the lower insulating layer, the piezoelectric layer, the electrode layer and the upper insulating layer are sequentially printed on the monitored structure using an aerosol printing technology, or the lower insulating layer, the electrode layer, the piezoelectric layer and the upper insulating layer are sequentially printed on the monitored structure.

[0017] Then, after annealing and polarization treatment, an array element is obtained, and a plurality of array elements form a piezoelectric sensing network.

[0018] In one embodiment, the step of printing the lower insulating layer and the step of printing the upper insulating layer both use a pneumatic atomization method to atomize insulating material ink, and the printing is carried out under the conditions of a sheath gas flow of 400sccm-600sccm, an atomization gas flow of 400sccm-600sccm, a printing platform moving speed of 8mm / s-12mm / s, and a temperature of 60℃-80℃.

[0019] And / or, in the step of printing the piezoelectric layer, an ultrasonic atomization method is used to atomize piezoelectric material ink, and the printing is carried out under the conditions of a sheath gas flow of 40sccm-60sccm, an atomization gas flow of 100sccm-140sccm, a printing platform moving speed of 2mm / s-4mm / s, and a temperature of 60℃-80℃.

[0020] And / or, in the step of printing the electrode layer, an ultrasonic atomization method is used to atomize the electrode material ink, and printing is carried out under the conditions that the sheath gas flow is 60sccm~100sccm, the atomization gas flow is 60sccm~100sccm, the printing platform moving speed is 2mm / s~4mm / s, and the temperature is 60℃~80℃.

[0021] In one of the embodiments, in the step of annealing, the temperature is 120℃~140℃, and the time is 1h~2h.

[0022] In one of the embodiments, in the step of polarization, the electric field intensity is 12MV / m~18MV / m, and the polarization time is 15min~60min.

[0023] The application of the piezoelectric sensing network for structural health monitoring as described above in the structural health monitoring of a sonar.

[0024] The piezoelectric sensing network of the application is composed of a plurality of array elements, has low invasiveness to the monitored structure to which it is attached, and can conform to the monitored structure, so that the piezoelectric sensing network has high compatibility; at the same time, by arranging the array elements along the edges of the surface of the monitored structure and optimizing the array element spacing and the distance from the edges of the surface of the monitored structure, global distributed monitoring or precise monitoring of key areas can be realized, and the damage identification sensitivity is significantly improved; in addition, each array element comprises a piezoelectric layer and an electrode layer, so that the piezoelectric sensing network has a dual monitoring mode of passive monitoring of acoustic emission signals and active monitoring of ultrasonic guided waves, and can monitor and evaluate the health status of the monitored structure in real time. In summary, the piezoelectric sensing network of the application has high compatibility with the monitored structure, high monitoring sensitivity, and when used in a sonar structure, can monitor and evaluate the health status of the sonar structure in real time. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments described in the application, and other drawings can also be obtained by those skilled in the art without creative effort.

[0026] Figure 1 It is a schematic diagram of the piezoelectric sensing network of the application;

[0027] Figure 2 It is a sectional view of the array element of the application;

[0028] Figure 3 It is a top view of the array element of the application;

[0029] Figure 4Waveform diagram of a pair of adjacent elements transmitting signal and receiving signal in the piezoelectric sensing network prepared for the embodiment 1 of the present application;

[0030] Figure 5 Waveform diagram of a pair of adjacent elements transmitting signal and receiving signal in the piezoelectric sensing network prepared for the embodiment 2 of the present application;

[0031] Figure 6 Waveform diagram of a pair of adjacent elements transmitting signal and receiving signal in the piezoelectric sensing network prepared for the embodiment 3 of the present application;

[0032] Figure 7 Waveform diagram of a pair of adjacent elements transmitting signal and receiving signal in the piezoelectric sensing network prepared for the comparative example 1;

[0033] Figure 8 Waveform diagram of a pair of adjacent elements transmitting signal and receiving signal in the piezoelectric sensing network prepared for the comparative example 2.

[0034] In the figure: 100, the monitored structure; 200, the element; 211, the lower insulating layer; 212, the upper insulating layer; 220, the piezoelectric layer; 230, the electrode layer; 231, the positive electrode; 232, the negative electrode. DETAILED DESCRIPTION

[0035] In order to facilitate the understanding of the present application, the present application will be described in more detail below. However, it should be understood that the present application can be realized in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the disclosure of the present application more thorough and comprehensive.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein is for the purpose of describing particular embodiments or examples only and is not intended to be limiting of the present application.

[0037] In combination with the figures shown in Figure 1 , Figure 2 and Figure 3 , the present application provides a piezoelectric sensing network for structural health monitoring, which comprises a plurality of elements 200, the element 200 comprising a lower insulating layer 211 and an upper insulating layer 212 arranged in sequence on the surface of the monitored structure 100, a piezoelectric layer 220 and an electrode layer 230 being sandwiched between the lower insulating layer 211 and the upper insulating layer 212, the electrode layer 230 extending out of the element 200 for realizing the electrical connection of the piezoelectric layer 220 with an external circuit;

[0038] The array element 200 is arranged along the edge of the monitored structure 100, and the distance d between adjacent array elements 200 satisfies 3.0 cm≤d≤5.0 cm, and the minimum vertical distance l of the array element 200 from the edge of the monitored structure 100 satisfies 2.0 cm≤l≤5.0 cm.

[0039] The piezoelectric sensing network of the present application is composed of a plurality of array elements 200, has little invasiveness to the attached monitored structure 100, and can conform to the monitored structure 100, so that the piezoelectric sensing network has high compatibility; at the same time, by arranging the array elements 200 along the edge of the surface of the monitored structure 100 and optimizing the distance between the array elements 200 and the edge of the surface of the monitored structure 100, global distributed monitoring or precise monitoring of key areas can be realized, and the damage identification sensitivity is significantly improved; in addition, each array element 200 includes a piezoelectric layer 220 and an electrode layer 230, so that the piezoelectric sensing network has a dual monitoring mode of passive monitoring of acoustic emission signals and active monitoring of ultrasonic guided waves, and can monitor and evaluate the health status of the monitored structure 100 in real time. In summary, the piezoelectric sensing network of the present application can be highly compatible with the monitored structure 100, has high monitoring sensitivity, and when used in a sonar structure, can monitor and evaluate the health status of the sonar structure in real time.

[0040] It can be understood that the array elements 200 in the piezoelectric sensing network can be arranged along the edge of the monitored structure 100 of any shape and any area, and as the area of the monitored structure 100 increases, the number of array elements 200 arranged along the edge of the monitored structure 100 increases, and the array elements 200 arranged along the edge of the monitored structure 100 can be arranged at equal intervals or at unequal intervals, preferably at equal intervals, which can improve the printing efficiency and facilitate signal extraction and processing during the implementation of structural health monitoring of the piezoelectric sensing network, thereby improving the accuracy of damage location evaluation.

[0041] The array elements 200 can also be arranged in any area other than the edge of the monitored structure 100, such as arranging specific array elements 200 on the surface of the monitored structure 100 according to the shape of the monitored structure 100. For the same area of the monitored structure 100, the more array elements 200 arranged, the higher the monitoring sensitivity of the piezoelectric sensing network.

[0042] Further, the distance d between adjacent array elements 200 can be any one value of 3.0 cm, 3.5 cm, 4.0 cm, 4.5 cm or 5.0 cm or a range value between any two values, and controlling the distance d between the array elements 200 within this range can suppress mutual crosstalk between the array elements 200 while ensuring damage monitoring accuracy.

[0043] To reduce the interference of the edge reflection echo of the monitored structure 100 to the received signal of the piezoelectric sensing network, the minimum vertical distance l of the array element 200 from the edge of the monitored structure 100 can be any one of 2.0 cm, 2.5 cm, 3.0 cm, 3.5 cm, 4.0 cm, 4.5 cm or 5.0 cm or a range value between any two of them, preferably 3.0 cm.

[0044] Optionally, the array element 200 is sequentially stacked as a lower insulating layer 211, a piezoelectric layer 220, an electrode layer 230 and an upper insulating layer 212; or, the array element 200 is sequentially stacked as a lower insulating layer 211, an electrode layer 230, a piezoelectric layer 220 and an upper insulating layer 212.

[0045] To better protect the piezoelectric layer 220 and reduce the influence of the insulating material on the sensitivity, optionally, the thickness of the upper insulating layer 212 and the lower insulating layer 211 is independently selected from 5 μm to 10 μm, and the thickness can be the same or different, and can be any one of 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm or a range value between any two of them.

[0046] It can be understood that the area of the lower insulating layer 211 can be greater than or equal to the area of the piezoelectric layer 220, and the area of the upper insulating layer 212 can be greater than or equal to the area of the piezoelectric layer 220. To better protect the piezoelectric layer 220 and the electrode layer 230 and fix the array element 200, the area of the lower insulating layer 211 is preferably greater than the area of the piezoelectric layer 220 and covers the monitored structure 100, and the area of the upper insulating layer 212 corresponds to the area of the lower insulating layer 211, so that the piezoelectric layer 220 and the electrode layer 230 are completely wrapped in the insulating layer.

[0047] Optionally, the thickness of the piezoelectric layer 220 is preferably 1.0 μm to 2.0 μm, and can be any one of 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2.0 μm or a range value between any two of them, the length of the piezoelectric layer 220 is preferably 2.0 cm to 4.0 cm, and can be any one of 2.0 cm, 2.5 cm, 3.0 cm, 3.5 cm or 4.0 cm or a range value between any two of them; the width of the piezoelectric layer 220 is preferably 0.5 cm to 1.0 cm; and can be any one of 0.5 cm, 0.6 cm, 0.7 cm, 0.8 cm, 0.9 cm or 1.0 cm or a range value between any two of them. Controlling the size of the piezoelectric layer 220 within the above range can facilitate improving the density of the array element 200 of the piezoelectric sensing network on the basis of ensuring the piezoelectric performance of the array element 200, thereby improving the monitoring accuracy.

[0048] Optionally, the thickness of the electrode layer 230 is preferably 100 nm to 300 nm, and can be any one of 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, or 300 nm, or a range between any two of them; the width of the electrode layer 230 is preferably 0.10 cm to 0.20 cm. Controlling the thickness and width of the electrode layer 230 can not only ensure good conductivity of the electrode layer 230 and effective emission / reception of ultrasonic guided wave signals, but also reduce the burden of the electrode layer 230 on the volume and mass of the sensing network.

[0049] It can be understood that the electrode layer 230 includes a positive electrode 231 and a negative electrode 232 arranged at intervals, the width of the positive electrode 231 and the width of the negative electrode 232 are independently selected from 0.10 cm to 0.20 cm, and can be any one of 0.10 cm, 0.12 cm, 0.14 cm, 0.16 cm, 0.18 cm, or 0.20 cm, or a range between any two of them, the positive electrode 231 is arranged along one long side of the piezoelectric layer 220, and the negative electrode 232 is arranged along the other long side of the piezoelectric layer 220, the positive electrode 231 and the negative electrode 232 respectively extend out of the array element 200, and are used to realize electrical connection of the positive electrode 231 and the negative electrode 232 with an external circuit.

[0050] Optionally, the upper insulating layer 212 and the lower insulating layer 211 are independently selected from at least one of an epoxy resin layer or a polydimethylsiloxane layer, so as to provide good insulation effect for the piezoelectric sensing network while taking into account the printability.

[0051] In order to make the piezoelectric layer 220 have better flexibility and piezoelectric effect, the piezoelectric layer 220 is selected from at least one of a piezoelectric composite layer composed of lead zirconate titanate (PZT) nanoparticles and polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) or a P(VDF-TrFE) layer, in order to make the piezoelectric layer 220 of the piezoelectric sensing network have a high piezoelectric strain coefficient and a low dielectric constant, the piezoelectric layer 220 is preferably a piezoelectric composite layer, wherein the volume ratio of PZT nanoparticles to P(VDF-TrFE) in the piezoelectric composite layer is 4:6 to 6:4.

[0052] Optionally, the electrode layer 230 is selected from at least one of a silver layer or a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) layer, so as to ensure that the electrode layer 230 has excellent conductivity and light weight characteristics, thereby maintaining high signal transmission efficiency while having minimal impact on the weight of the array element 200.

[0053] The application further provides a preparation method of the piezoelectric sensing network for structural health monitoring. First, a layout of the piezoelectric sensing network is designed according to the geometric size of the monitored structure 100, then the lower insulating layer 211, the piezoelectric layer 220, the electrode layer 230 and the upper insulating layer 212 are sequentially stacked and printed on the monitored structure 100 by using the aerosol printing technology, or the lower insulating layer 211, the electrode layer 230, the piezoelectric layer 220 and the upper insulating layer 212 are sequentially stacked and printed on the monitored structure 100 by using the aerosol printing technology, and then annealing and polarization treatment are performed to obtain the array element 200, and a plurality of array elements 200 form the piezoelectric sensing network.

[0054] Specifically, in the steps of printing the lower insulating layer 211 and the upper insulating layer 212, the insulating material ink is atomized by using the pneumatic atomization method. In order to fully atomize the insulating material ink and make the printed lower insulating layer 211 and upper insulating layer 212 more dense, the sheath gas flow of the printing setting is preferably 400-600 sccm, which can be selected as any one value or a range value between any two values of 400 sccm, 420 sccm, 440 sccm, 460 sccm, 480 sccm, 500 sccm, 520 sccm, 540 sccm, 560 sccm, 580 sccm or 600 sccm, and is further preferably 500 sccm; the atomization gas flow of the printing setting is preferably 400-600 sccm, which can be selected as any one value or a range value between any two values of 400 sccm, 420 sccm, 440 sccm, 460 sccm, 480 sccm, 500 sccm, 520 sccm, 540 sccm, 560 sccm, 580 sccm or 600 sccm, and is further preferably 500 sccm; the printing platform moving speed is preferably 8-12 mm / s, which can be selected as any one value or a range value between any two values of 8 mm / s, 9 mm / s, 10 mm / s, 11 mm / s or 12 mm / s, and is further preferably 10 mm / s; the temperature of the printing setting is preferably 60-80℃, and is further preferably 80℃.

[0055] Further, the insulating material ink contains insulating material and solvent, and the concentration of the insulating material in the insulating material ink is 35wt.%-45wt.%, preferably 40wt.%, and the insulating material is preferably at least one of epoxy resin or polydimethylsiloxane, preferably epoxy resin.

[0056] Specifically, in the step of printing the piezoelectric layer 220, the piezoelectric material ink is atomized by ultrasonic atomization method. In order to fully atomize the piezoelectric material ink and control the printing morphology of the piezoelectric layer 220, the sheath gas flow of the printing setting is preferably 40-60 sccm, which can be selected as any one value or a range value between any two values of 40 sccm, 45 sccm, 50 sccm, 55 sccm or 60 sccm, and is further preferably 50 sccm; the atomization gas flow of the printing setting is preferably 100-140 sccm, which can be selected as any one value or a range value between any two values of 100 sccm, 110 sccm, 120 sccm, 130 sccm or 140 sccm, and is further preferably 120 sccm; the printing platform moving speed is 2-4 mm / s, which can be selected as any one value or a range value between any two values of 2 mm / s, 2.5 mm / s, 3 mm / s, 3.5 mm / s or 4 mm / s, and is further preferably 3 mm / s; the temperature of the printing setting is preferably 60-80℃, and is further preferably 60℃.

[0057] Further, the piezoelectric material ink is selected from at least one of a piezoelectric composite ink composed of PZT nanoparticles and P(VDF-TrFE) or a P(VDF-TrFE) ink, and preferably the piezoelectric composite ink composed of PZT nanoparticles and P(VDF-TrFE) is used.

[0058] Specifically, in the piezoelectric composite ink, the volume ratio of PZT nanoparticles to P(VDF-TrFE) is 4:6-6:4; the solvent of the piezoelectric composite ink is N,N-dimethylformamide (DMF), and the content of P(VDF-TrFE) in the DMF solvent is 17.5wt.%-22.5wt.%.

[0059] Specifically, in the step of printing the electrode layer 230, the electrode material ink is atomized by ultrasonic atomization method, in order to fully atomize the electrode material ink and control the printing morphology of the electrode layer 230, the sheath gas flow of the printing setting is preferably 60sccm~100sccm, and can be selected as any one value or a range value between any two values of 60sccm, 70sccm, 80sccm, 90sccm and 100sccm; the atomization gas flow of the printing setting is preferably 60sccm~100sccm, and can be selected as any one value or a range value between any two values of 60sccm, 70sccm, 80sccm, 90sccm and 100sccm, and is further preferably 80sccm; the printing platform moving speed is preferably 2mm / s~4mm / s, and can be selected as any one value or a range value between any two values of 2mm / s, 2.5mm / s, 3mm / s, 3.5mm / s or 4mm / s, and is further preferably 3mm / s; the temperature of the printing setting is preferably 60℃~80℃, and is further preferably 80℃.

[0060] Further, the electrode material ink contains electrode material and solvent, in the electrode material ink, the concentration of the electrode material is 15wt.%~25wt.%, and is preferably 20wt.%, and the electrode material is selected from at least one of silver or PEDOT:PSS, and preferably silver is adopted.

[0061] In order to fully volatilize the solvent in each printing material and make P(VDF-TrFE) obtain higher crystallinity, in the annealing step, the temperature is preferably 120℃~140℃, and is further preferably 120℃; the annealing time is preferably 1h~2h, and is further preferably 2h.

[0062] In order to make the printed piezoelectric layer 220 obtain better piezoelectricity, in the polarization step, the electric field intensity is preferably 12MV / m~18MV / m, and is further preferably 15MV / m; the polarization time is preferably 15min~60min, and is further preferably 30min.

[0063] The piezoelectric sensing network in the application adopts full-flexible material, and is prepared by aerosol printing technology to realize micron-level piezoelectric sensing network, so that the additional mass of the piezoelectric sensing network is extremely small, and can be conformally attached to a curved surface structure or a variable cross-section structure, which not only eliminates the signal attenuation problem caused by the contact gap of the traditional rigid sensor, but also maintains the stability of the electrical and mechanical properties of the piezoelectric sensing network, effectively avoids the damage of the traditional sensor to the local stiffness disturbance and the aerodynamic shape, and significantly improves the accuracy and reliability of the monitoring data. Therefore, the preparation method of the application can realize high customization, high precision and high consistency of the piezoelectric sensing network.

[0064] The application further provides application of the piezoelectric sensing network for structural health monitoring in sonar structural health monitoring.

[0065] Hereinafter, the technical solutions of the present application will be further described through the following specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be obtained by purchase on the market.

[0066] Example 1

[0067] Firstly, taking the sonar back plate as the monitored structure 100, the layout of the piezoelectric sensing network is designed, the elements 200 of the piezoelectric sensing network are arranged along the outer periphery of the sonar back plate at equal intervals, the interval d between adjacent elements 200 is 3.0 cm, the minimum vertical distance l of each element 200 from the outer peripheral edge of the sonar back plate is 3.0 cm, and each element 200 is designed to be sequentially stacked with a lower insulating layer 211, a piezoelectric layer 220, an electrode layer 230 and an upper insulating layer 212. The lower insulating layer 211 is designed to be attached to the sonar back plate, the area of the lower insulating layer 211 and the upper insulating layer 212 is designed to completely cover the sonar back plate, and the thickness of each is 10 μm; the area of the piezoelectric layer 220 is designed to be 3.0 x 0.8 cm 2 , and the thickness is 2.0 μm; the area of the electrode layer 230 is designed to be 3.0 x 0.2 cm 2 for each of the positive electrode 231 and the negative electrode 232, and the thickness of each is 300 nm.

[0068] Then, aerosol printing is performed, including the following steps:

[0069] The lower insulating layer 211 is printed on the monitored structure 100, specifically: the epoxy resin ink with a concentration of 40 wt.% is atomized by a pneumatic atomization method, and the printing is performed at a sheath gas flow of 600 sccm, an atomization gas flow of 600 sccm, a printing platform moving speed of 8 mm / s and a temperature of 80℃.

[0070] The piezoelectric layer 220 is printed on the lower insulating layer 211, specifically: PZT nanoparticles and P(VDF-TrFE) are dissolved in a DMF solvent to prepare a piezoelectric composite ink, wherein the volume ratio of PZT nanoparticles to P(VDF-TrFE) is 6:4, and the content of P(VDF-TrFE) in the DMF is 20 wt.%. The piezoelectric composite ink is atomized by an ultrasonic atomization method, and the printing is performed at a sheath gas flow of 60 sccm, an atomization gas flow of 140 sccm, a printing platform moving speed of 2 mm / s and a temperature of 80℃.

[0071] Print the electrode layer 230 on the piezoelectric layer 220, specifically: adopt ultrasonic atomization method to atomize silver ink with a concentration of 20wt.%, print the positive electrode 231 and the negative electrode 232 respectively under the conditions of sheath gas flow of 100sccm, atomization gas flow of 100sccm, printing platform moving speed of 2mm / s, and temperature of 80℃.

[0072] Print and deposit the upper insulation layer 212 on the electrode layer 230, specifically: adopt pneumatic atomization method to atomize epoxy resin ink with a concentration of 40wt.%, print under the conditions of sheath gas flow of 600sccm, atomization gas flow of 600sccm, printing platform moving speed of 8mm / s, and temperature of 80℃.

[0073] Anneal the array element 200 at 140℃ for 2h, and then polarize in an electric field of 18MV / m for 60min to obtain a piezoelectric sensing network, and test the piezoelectric strain constant d 33 of the piezoelectric layer, which is 40.6pC / N, and the dielectric constant of the piezoelectric layer is 19.4@10 3 Hz.

[0074] Test the transmission and reception of ultrasonic guided waves of the piezoelectric sensing network: generate a 5-cycle Hann window modulated sinusoidal pulse signal with a center frequency of 750kHz by a waveform generator, amplify to 70V by a power amplifier pp to excite a certain array element of the piezoelectric sensing network, based on the inverse piezoelectric effect, the array element generates ultrasonic guided waves in the sonar backplane under voltage excitation. Conversely, based on the piezoelectric effect, the microstructure strain caused by the ultrasonic guided waves causes other array elements of the piezoelectric sensing network to generate voltage signals, which are then filtered and amplified by a preamplifier, and recorded by an oscilloscope, Figure 4 is a waveform diagram of the transmission signal and the reception signal of a pair of adjacent array elements of the piezoelectric sensing network, where A is the excitation signal and B is the reception signal. As can be seen from the figure, the first arrival wave component of the reception signal is the zero-order symmetric mode (S0) Lamb wave, the waveform is clear and complete, and is separated from and does not overlap with the second part of the guided wave component of the reception signal, i.e. the Lamb wave reflected by the outer peripheral edge of the sonar backplane.

[0075] Example 2

[0076] Firstly, taking the sonar back plate as the monitored structure 100, the layout of the piezoelectric sensing network is designed. The elements 200 of the piezoelectric sensing network are arranged along the outer periphery of the sonar back plate at equal intervals. The interval d between adjacent elements 200 is 5.0 cm. The minimum vertical distance l between each element 200 and the outer periphery edge of the sonar back plate is 2.0 cm. Each element 200 is designed to be sequentially stacked with a lower insulating layer 211, a piezoelectric layer 220, an electrode layer 230, and an upper insulating layer 212. The lower insulating layer 211 is designed to be attached to the sonar back plate. The areas of the lower insulating layer 211 and the upper insulating layer 212 are designed to completely cover the sonar back plate. The thicknesses of the lower insulating layer 211 and the upper insulating layer 212 are each 8 μm. The area of the piezoelectric layer 220 is designed to be 4.0 x 1.0 cm 2 , and the thickness is 1.5 μm. The area of the electrode layer 230 is designed to be 4.0 x 0.2 cm 2 for each of the positive electrode 231 and the negative electrode 232, and the thickness is 200 nm.

[0077] Then, aerosol printing is performed, including the following steps:

[0078] The lower insulating layer 211 is printed on the monitored structure 100. Specifically, the epoxy resin ink with a concentration of 40 wt.% is atomized by a pneumatic atomization method. The printing is performed at a sheath gas flow of 500 sccm, an atomization gas flow of 500 sccm, a printing platform moving speed of 10 mm / s, and a temperature of 70°C.

[0079] The piezoelectric layer 220 is printed on the lower insulating layer 211. Specifically, PZT nanoparticles and P(VDF-TrFE) are dissolved in a DMF solvent to prepare a piezoelectric composite ink. The volume ratio of PZT nanoparticles to P(VDF-TrFE) is 6:4, and the content of P(VDF-TrFE) in the DMF is 20 wt.%. The piezoelectric composite ink is atomized by an ultrasonic atomization method. The printing is performed at a sheath gas flow of 50 sccm, an atomization gas flow of 120 sccm, a printing platform moving speed of 3 mm / s, and a temperature of 70°C.

[0080] The electrode layer 230 is printed on the piezoelectric layer 220. Specifically, the silver ink with a concentration of 20 wt.% is atomized by an ultrasonic atomization method. The positive electrode 231 and the negative electrode 232 are respectively printed at a sheath gas flow of 80 sccm, an atomization gas flow of 80 sccm, a printing platform moving speed of 3 mm / s, and a temperature of 70°C.

[0081] The upper insulating layer 212 is printed on the electrode layer 230. Specifically, the epoxy resin ink with a concentration of 40 wt.% is atomized by a pneumatic atomization method. The printing is performed at a sheath gas flow of 500 sccm, an atomization gas flow of 500 sccm, a printing platform moving speed of 10 mm / s, and a temperature of 70°C.

[0082] The array element 200 is annealed at 130℃ for 1.5h, and then polarized in an electric field of 15MV / m for 45min to obtain a piezoelectric sensing network.

[0083] The piezoelectric sensing network is tested for transmitting and receiving ultrasonic guided wave according to the method of Example 1, Figure 5 The piezoelectric sensing network transmits and receives signal waveforms for a pair of array elements, wherein A is the excitation signal and B is the received signal. As can be seen from the figure, the first arriving wave component of the received signal is the zero-order symmetric mode (S0) Lamb wave, which has a clear and complete waveform and is not overlapped with the second part of the received signal, which is the guided wave component, i.e. the Lamb wave reflected by the outer peripheral edge of the sonar back plate.

[0084] Example 3

[0085] First, the layout of the piezoelectric sensing network is designed with the sonar back plate as the monitored structure. The array elements of the piezoelectric sensing network are arranged at equal intervals in an array. The distance d between adjacent array elements is 4.0cm. The minimum vertical distance l between the array element close to the outer peripheral edge of the sonar back plate and the outer peripheral edge of the sonar back plate is 5.0cm. Each array element is designed to have a lower insulating layer, an electrode layer, a piezoelectric layer and an upper insulating layer stacked in turn. The lower insulating layer is designed to be attached to the sonar back plate. The area of the lower insulating layer and the upper insulating layer is designed to completely cover the sonar back plate, and the thickness of each is 5μm. The area of the piezoelectric layer is designed to be 2.0×0.5cm 2 , and the thickness is 1.0μm. The area of the electrode layer is designed to be 2.0×0.1cm 2 for each of the positive electrode 231 and the negative electrode 232, and the thickness is 100nm.

[0086] Then, aerosol printing is performed, including the following steps:

[0087] The lower insulating layer is printed on the monitored structure, specifically: the epoxy resin ink with a concentration of 40wt.% is atomized by a pneumatic atomization method, and the printing is performed at a sheath gas flow of 400sccm, an atomization gas flow of 400sccm, a printing platform moving speed of 12mm / s and a temperature of 60℃.

[0088] The lower insulating layer is printed on the lower insulating layer, specifically: PZT nanoparticles and P(VDF-TrFE) are dissolved in DMF solvent to prepare a piezoelectric composite ink, wherein the volume ratio of PZT nanoparticles to P(VDF-TrFE) is 6:4, and the content of P(VDF-TrFE) in DMF is 20wt.%. The piezoelectric composite ink is atomized by an ultrasonic atomization method, and the printing is performed at a sheath gas flow of 40sccm, an atomization gas flow of 100sccm, a printing platform moving speed of 4mm / s and a temperature of 60℃.

[0089] Printing the electrode layer on the piezoelectric layer, specifically: using ultrasonic atomization method to atomize silver ink with a concentration of 20wt.%, printing the positive electrode and the negative electrode under the conditions of sheath gas flow of 60sccm, atomization gas flow of 60sccm, printing platform moving speed of 4mm / s, and temperature of 60℃.

[0090] Printing and depositing the upper insulating layer on the electrode layer, specifically: using pneumatic atomization method to atomize epoxy resin ink with a concentration of 40wt.%, printing under the conditions of sheath gas flow of 400sccm, atomization gas flow of 400sccm, printing platform moving speed of 12mm / s, and temperature of 60℃.

[0091] Annealing the array elements at 120℃ for 1h, and then polarizing in an electric field of 12MV / m for 15min to obtain the piezoelectric sensing network.

[0092] Testing the piezoelectric sensing network for transmitting and receiving ultrasonic guided wave ability according to the method of Example 1, Figure 6 The waveform diagram of the transmitting signal and the receiving signal of a pair of array elements of the piezoelectric sensing network, wherein A is the excitation signal and B is the receiving signal. As can be seen from the figure, the first arriving wave component of the receiving signal is the zero-order symmetric mode (S0) Lamb wave, the waveform is clear and complete, and is separated from the second part of the receiving signal, that is, the Lamb wave reflected by the outer peripheral edge of the sonar back plate, without overlapping.

[0093] Comparative Example 1

[0094] Comparative Example 1 is different from Example 1 in that: the sonar back plate is used as the monitored structure, the layout of the piezoelectric sensing network is designed, and the array elements of the piezoelectric sensing network are arranged at equal intervals along the outer periphery of the sonar back plate, the spacing d between adjacent array elements is 1.0cm, and the minimum vertical distance l between each array element and the outer peripheral edge of the sonar back plate is 3.0cm.

[0095] Figure 7 The waveform diagram of the transmitting signal and the receiving signal of a pair of array elements of the piezoelectric sensing network, wherein A is the excitation signal and B is the receiving signal. As can be seen from the figure, the first arriving wave component of the receiving signal is the zero-order symmetric mode (S0) Lamb wave, which overlaps and interferes with the crosstalk signal, and the signal characteristics cannot be accurately extracted, making it difficult to effectively implement monitoring.

[0096] Comparative Example 2

[0097] Comparative Example 2 is different from Example 1 in that: the sonar back plate is used as the monitored structure, the layout of the piezoelectric sensing network is designed, and the array elements of the piezoelectric sensing network are arranged at equal intervals along the outer periphery of the sonar back plate, the spacing d between adjacent array elements is 3.0cm, and the minimum vertical distance l between each array element and the outer peripheral edge of the sonar back plate is 1.0cm.

[0098] Figure 8The waveforms of the transmitting signal and the receiving signal of a pair of elements of the piezoelectric sensing network are shown in the figure, wherein A is the excitation signal and B is the receiving signal, and it can be seen from the figure that the first arriving wave component of the receiving signal is the zero-order symmetric mode (S0) Lamb wave, and the second part of the wave component of the receiving signal is the Lamb wave reflected by the outer peripheral edge of the back plate of the sonar, which partially overlaps and interferes, and the signal characteristics cannot be accurately extracted, and it is difficult to effectively implement monitoring.

[0099] The technical features of the above-described embodiments can be combined in any manner, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not exist, they should be considered as the scope of the description.

[0100] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A piezoelectric sensing network for structural health monitoring, characterized in that: The piezoelectric sensing network includes a plurality of array elements, each of which includes a lower insulating layer and an upper insulating layer sequentially disposed on the surface of the monitored structure, a piezoelectric layer and an electrode layer sandwiched between the lower insulating layer and the upper insulating layer, and the electrode layer extending out of the array element to achieve electrical connection between the piezoelectric layer and an external circuit; The array elements are arranged along the edge of the monitored structure, and the spacing d between adjacent array elements satisfies 3.0 cm ≤ d ≤ 5.0 cm. The minimum vertical distance l between the array element and the edge of the monitored structure satisfies 2.0 cm ≤ l ≤ 5.0 cm.

2. The piezoelectric sensing network for structural health monitoring according to claim 1, characterized in that: The array elements are arranged at equal intervals along the edge of the monitored structure.

3. The piezoelectric sensing network for structural health monitoring according to claim 1, characterized in that: The thickness of the upper insulating layer and the lower insulating layer are independently selected from 5 μm to 10 μm; And / or, the thickness of the piezoelectric layer is 1.0 μm to 2.0 μm; And / or, the thickness of the electrode layer is 100 nm to 300 nm.

4. The piezoelectric sensing network for structural health monitoring according to claim 1 or claim 3, characterized in that: The piezoelectric layer has a length of 2.0 cm to 4.0 cm and a width of 0.5 cm to 1.0 cm; And / or, the length of the electrode layer is equal to the length of the piezoelectric layer, and the width of the electrode layer is 0.10 cm to 0.20 cm; And / or, the length and width of the upper insulating layer and the lower insulating layer are greater than or equal to the piezoelectric layer.

5. The piezoelectric sensing network for structural health monitoring according to claim 1, characterized in that: The piezoelectric layer is selected from at least one of a piezoelectric composite material layer composed of lead zirconate titanate nanoparticles and polyvinylidene fluoride-trifluoroethylene or a polyvinylidene fluoride-trifluoroethylene layer, wherein the volume ratio of lead zirconate titanate nanoparticles to polyvinylidene fluoride-trifluoroethylene in the piezoelectric composite material layer is 4:6 to 6:4; And / or, the upper insulating layer and the lower insulating layer are independently selected from at least one of an epoxy resin layer and a polydimethylsiloxane layer; And / or, the electrode layer is selected from at least one of a silver layer and a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate layer.

6. A method for preparing a piezoelectric sensor network for structural health monitoring according to any one of claims 1 to 5, characterized in that: Using aerosol printing technology to sequentially print a lower insulating layer, a piezoelectric layer, an electrode layer, and an upper insulating layer on the monitored structure, or sequentially printing a lower insulating layer, an electrode layer, a piezoelectric layer, and an upper insulating layer on the monitored structure; Then, after annealing and polarization treatment, array elements are obtained, and a plurality of the array elements form a piezoelectric sensing network.

7. The method for preparing a piezoelectric sensor network for structural health monitoring according to claim 6, characterized in that: The steps of printing the lower insulating layer and the upper insulating layer both use a pneumatic atomization method to atomize the insulating material ink, and the printing is performed under the conditions of a sheath gas flow of 400 sccm to 600 sccm, an atomizing gas flow of 400 sccm to 600 sccm, a printing platform movement speed of 8 mm / s to 12 mm / s, and a temperature of 60° C. to 80° C. And / or, in the step of printing the piezoelectric layer, ultrasonic atomization is used to atomize the piezoelectric material ink, and printing is performed under the conditions of a sheath gas flow of 40 sccm to 60 sccm, an atomizing gas flow of 100 sccm to 140 sccm, a printing platform movement speed of 2 mm / s to 4 mm / s, and a temperature of 60° C. to 80° C.; And / or, in the step of printing the electrode layer, ultrasonic atomization is used to atomize the electrode material ink, and printing is performed under the conditions of a sheath gas flow of 60 sccm~100 sccm, an atomizing gas flow of 60 sccm~100 sccm, a printing platform movement speed of 2 mm / s~4 mm / s, and a temperature of 60°C~80°C.

8. The method for preparing a piezoelectric sensor network for structural health monitoring according to claim 6, wherein: In the annealing step, the temperature is 120° C. to 140° C., and the time is 1 hour to 2 hours.

9. The method for preparing a piezoelectric sensor network for structural health monitoring according to claim 6, wherein: In the polarization step, the electric field strength is 12 MV / m to 18 MV / m, and the polarization time is 15 min to 60 min.

10. Application of the piezoelectric sensor network for structural health monitoring according to any one of claims 1 to 5 in sonar structural health monitoring.

Images