CN102924020A - Piezoresistive/piezoelectric composite material and manufacturing method thereof, sensor adopting piezoresistive/piezoelectric composite material and manufacturing method thereof - Google Patents

Abstract

The invention relates to a piezoresistive/piezoelectric material system and a production and application method thereof. The piezoresistive/piezoelectric composite material of the present invention includes the following components by weight ratio: 100 parts of cement, 105-500 parts of micro/nano-scale piezoelectric ceramic powder, 10-30 parts of fly ash, 15-50 parts 1 part of water, 0.01-2 parts of superplasticizer, 0.1-10 parts of tough fiber, 0.01-15 parts of conductive filler. The sensor adopting the material in the present invention includes a piezoresistive/piezoelectric composite material layer, an electrode is respectively arranged on the upper and lower surfaces of the piezoresistive/piezoelectric composite material layer, and both the piezoresistive/piezoelectric composite material layer and the electrodes are wrapped in a packaging shell Inside, the upper and lower electrodes are connected through an electromagnetic shielding wire that runs through the package shell, and the sensor is arranged between the support and the supported bridge deck unit or embedded in the bridge deck unit. The invention has intrinsic structural toughness and the synchronous monitoring ability of static/dynamic traffic and structural parameters covering the whole frequency domain.

Description

Piezoresistive/piezoelectric composite material and its manufacturing method, sensor using the same and its manufacturing method

technical field

The invention relates to a self-powered piezoresistive/piezoelectric composite sensor system for a self-powered traffic and structural parameter synchronous monitoring sensor and a production and application method thereof.

Background technique

In recent years, with the rapid development of the national economy, the number of vehicles in my country has increased rapidly, and expressways, river (cross-sea) bridges, and urban viaducts/overpasses have been continuously built. Once a traffic accident or structural collapse occurs in these traffic structures, it will easily lead to congestion and casualties in the entire traffic system, and it will be difficult to repair in a short period of time, resulting in a significant drop in traffic capacity and immeasurable losses. Therefore, it is particularly necessary to carry out traffic control and structural health monitoring on the traffic structure of these hub areas and key road sections. At the same time, these traffic structures (especially the structural joints) are often in slight vibration under the action of driving loads. If the corresponding mechanical vibration energy can be effectively collected and supplied to the corresponding sensor monitoring network, or even the lighting systems on both sides , which is of great significance in today's era of energy conservation and environmental protection.

Various cement-based sensors, which have good compatibility with traffic structure acoustic impedance and matching, and have similar service life, have made great progress in the past few decades. It can be said that the success of various traffic structure monitoring systems is largely attributed to These smart sensors provide accurate and stable bridge traffic and structural data, such as accurate speed signals, trigger classification information, dynamic performance, displacement and deformation information, and long-term feedback traffic information statistics. For example, the technology of Chinese Patent No. ZL02132967.2, the electrical properties of cement matrix materials mixed with various conductive functional components (carbon black, nickel powder, carbon fiber, carbon nanotubes, etc.) will change with the change of external load/deformation The piezoresistive sensor formed by the piezoresistive effect is sensitive to (quasi) static signals, but not sensitive to dynamic vibration signals, and has low sensing accuracy. For example, the Chinese patent No. ZL201010523624.3 technology, using the cement matrix material mixed with fine piezoelectric ceramic (PZT) powder or directly encapsulating the PZT sheet with resin concrete, the charge density at both ends of the block electrode will change with the external load/deformation The piezoelectric sensor formed by the changing (inverse) piezoelectric effect is mainly sensitive to dynamic vibration signals and insensitive to (quasi) static signals. It has low intrinsic structural toughness and is susceptible to shrinkage cracking of concrete pavement and subsidence of roadbed. Defects such as the influence of the natural environment. At the same time, it does not involve the use of the inverse piezoelectric effect of the corresponding piezoelectric sensor to effectively collect and store the vibration energy of the driving machine and various circuit energy supply systems.

Contents of the invention

The technical effects of the present invention can overcome the above-mentioned defects, and provide a piezoresistive/piezoelectric composite material, which organically combines (quasi) static piezoresistive effect and dynamic piezoelectric effect, and is supplemented with flexible and toughened tough fibers, and then provides In addition to ensuring good compatibility with concrete structures and long service life, it also has multiple performances such as high intrinsic structural toughness, static/dynamic traffic structure monitoring covering the entire frequency range, and vibration self-supply. composite material.

In order to achieve the above object, the present invention adopts the following technical scheme: it includes the following components by weight ratio: 100 parts of cement, 105-500 parts of micro/nano-scale piezoelectric ceramic powder, 10-30 parts of fly ash, 15 - 50 parts of water, 0.01-2 parts of superplasticizer, 0.1-10 parts of ductile fiber, 0.01-15 parts of conductive filler.

Another object of the present invention is to provide a method for preparing a piezoresistive/piezoelectric composite material, comprising the steps of:

(1) Preparation of micro/nano piezoelectric ceramic powder;

Micro/nano lead zirconate titanate or lead niobium magnesium zirconate titanate piezoelectric ceramic powder can be synthesized by any method known to those skilled in the art, such as sol-gel method, hydrothermal method or sol-hydrothermal composite method. The preparation process of the sol-gel method is as follows: lead acetate, tetrabutyl titanate, and zirconium nitrate are used as raw materials (to ensure that the atomic ratio of lead, zirconium, and titanium in the raw material ratio is 1:0.52-0.56:0.44-0.48), first Dissolve zirconium nitrate and tetrabutyl titanate in water and ethylene glycol respectively, then heat and stir at 105-110°C for 0.5-1 hour, then add lead acetate and ethylene glycol successively, continue heating at 105-110°C and reflux for 1.5 -3 hours, the piezoelectric ceramic sol can be obtained, and after drying, it is calcined at 800-850° C. for 2-4 hours.

(2) Using acetone as a grinding aid, dry-mix 100 parts of cement and 10-30 parts of fly ash that acts as a lubricant and bridge between the filler and the matrix for 5-10 minutes, and then mix with 105-500 parts of the step ( 1) The prepared piezoelectric ceramic powder is ball milled for 10-20 minutes, then conductive filler and tough fiber are added successively, and then ball milled and mixed for 30-60 minutes;

(3) further ultrasonically disperse the mixture obtained in step (2) in an acetone medium for 30-60 minutes, volatilize and dry to obtain a mixed powder;

(4) Add 15-50 parts of water dissolved with 0.01-2 parts of superplasticizer to the mixed powder obtained in step (3), and after mixing, use compression molding to press into flakes of the shape and size according to actual needs sample;

5) Place the thin slice sample obtained in step (4) in a cement steam curing box, and after curing for three days under the condition of steam at 45°C and relative humidity RH100%, dry and clean the upper and lower surfaces to be coated with electrodes;

(6) Coat the thin slice sample obtained in step (5) with an electrode, and after drying, polarize it with a high-voltage DC power supply in a silicone oil bath for 1-12 hours at room temperature, and obtain a piezoresistive/ Sensing elements made of piezoelectric composite materials.

In the above sensing element, the electrode arrangement is one of full coverage, grid, interdigitated or cross grid; the electrode material is one of conductive silver gel electrode, silver electrode or nickel electrode.

Water-based resin (and/or supporting water-based curing agent) is a stable resin emulsion prepared by dispersing resin in the form of particles or droplets in water as the continuous phase medium. It can be better mixed with cement-based materials. Bonding and curing in a humid environment improves the compactness, water resistance, impact toughness and other properties of the hardened cement-based material. The water-based resin concrete used as the packaging material of the sensor not only has good compact waterproof performance, but also has good acoustic impedance, matching compatibility and working life with concrete materials.

Another object of the present invention is to provide a kind of sensor that adopts above-mentioned material, comprise piezoresistive/piezoelectric composite material layer, the upper and lower surface of piezoresistive/piezoelectric composite material layer respectively is provided with an electrode, piezoresistive/piezoelectric composite material layer Both the electrode and the electrodes are wrapped in the package shell, and the upper and lower electrodes are connected through electromagnetic shielding wires penetrating the package shell.

The electrodes are arranged in the form of full coverage or grid or interdigitated or cross grid. The electrodes are conductive silver gel electrodes or silver electrodes or nickel electrodes.

The package shell is a kind of fiber reinforced resin concrete mixed with cement, fly ash, water-based resin, water-based curing agent and tough fiber according to the weight ratio of 1:0.1-0.3:0.4-0.8:0.4-0.6:0.01-0.1 .

The above-mentioned piezoresistive/piezoelectric sensing element is packaged into a piezoresistive/piezoelectric composite sensor by fiber-reinforced resin concrete. The preparation method includes the following steps: firstly disperse the tough fiber in the water-based resin by high-speed stirring according to the proportion, and then add the corresponding curing agent. Then add cement and fly ash dry mixture, and stir evenly; fix the piezoresistive/piezoelectric sensing element in the mold (the upper and lower electrodes are drawn out through electromagnetic shielding wires and connected to shielding connectors), and then the above The fiber-reinforced resin concrete mixture is poured into the mold, and before the final setting of the cement, the mold is moved to a vacuum drying oven for vacuuming and defoaming (to further improve the density and insulation performance of the packaging material); finally, the water-based resin and the corresponding The surface of the mixed diluent of the curing agent is covered and cured until the age of 28 days, and the self-powered piezoresistive/piezoelectric composite sensor of the present invention is obtained. The size of the sensor can be adjusted according to actual needs.

In the aforementioned self-powered piezoresistive/piezoelectric composite sensor, the cement is one of Portland cement, ordinary Portland cement, and sulphoaluminate cement.

In the aforementioned self-powered piezoresistive/piezoelectric composite sensor, the fly ash is Class I fly ash specified in "Fly Ash Used in Cement and Concrete" (GB/T1596-2005).

In the aforementioned self-powered piezoresistive/piezoelectric composite sensor, the water is one of commercially available distilled water and deionized water.

In the above-mentioned self-powered piezoresistive/piezoelectric composite sensor, the superplasticizer is polycarboxylate-based superplasticizer, aliphatic superplasticizer, sulfamate-based superplasticizer, melamine One or more combinations of resin-based superplasticizers and naphthalene-based superplasticizers.

In the above self-powered piezoresistive/piezoelectric composite sensor, the tough fiber is one of polyvinyl alcohol fiber, polypropylene fiber, and polyimide fiber.

In the above-mentioned self-powered piezoresistive/piezoelectric composite sensor, the conductive filler is micro/nano-scale carbon black, micro/nano-scale nickel powder, carbon fiber, carbon nanofiber, carbon nanotube, graphene, graphene oxide bonded branched carbon fiber, graphene oxide grafted carbon nanofiber or a mixture of several of them.

In the above self-powered piezoresistive/piezoelectric composite sensor, the water-based resin is water-based epoxy resin, water-based phenolic resin, water-based urea-formaldehyde resin, water-based melamine-formaldehyde resin, water-based polyurethane resin, water-soluble polyimide resin One of them; the water-based curing agent is a special curing agent corresponding to each water-based resin.

The above-mentioned self-powered piezoresistive/piezoelectric composite sensor can also use an energy harvesting/discharging control circuit well-known to those skilled in the art to convert and effectively store the instantaneous electric energy under the inverse piezoelectric effect when the vehicle rolls over the above-mentioned sensor And feed back to realize the self-supply of sensor signal acquisition system.

After the self-powered piezoresistive/piezoelectric composite sensor of the present invention is embedded or pasted into the traffic structure system (that is, the sensor is arranged between the support and the supported bridge deck unit or embedded in the bridge deck unit), in addition to the interface and impedance In addition to good matching, high frequency response, and high durability, it also has better intrinsic structural toughness and the ability to simultaneously monitor static/dynamic traffic and structural parameters covering the full frequency domain, and can effectively collect vibration energy of driving machinery , Storage and energy supply for various circuits. Therefore, the self-powered composite sensor has a good application prospect.

Description of drawings

Fig. 1 is embodiment 1 of the present invention self-powered piezoresistive/piezoelectric sensor static/dynamic signal synchronous acquisition system;

Fig. 2 is an enlarged schematic diagram of the sensor of the present invention.

Fig. 3 is the layout of the static/dynamic signal synchronous acquisition system of the self-powered piezoresistive/piezoelectric sensor in Embodiment 2 of the present invention.

In the figure: 1. piezoresistive/piezoelectric composite material layer; 2. electrode; 3. packaging shell; 4. electromagnetic shielding wire; 5. bridge deck unit; 6. support; 7. dynamic signal acquisition system; 8. ( quasi) static signal acquisition system.

Detailed ways

Example 1

As shown in Figure 1 and Figure 2, the self-powered piezoresistive/piezoelectric composite sensor system between the bridge deck unit 5 supported by the support 6 of the present invention includes an inductive element, a packaging shell and a dynamic signal acquisition system 7, (quasi) static signal acquisition system8. The inductive element includes a piezoresistive/piezoelectric composite material layer 1 and a pair of electrodes 2 located on the upper and lower surfaces of the piezoresistive/piezoelectric composite material. A pair of electrodes are connected through the electromagnetic shielding wire 4 that runs through the package shell. The electromagnetic shielding wire 4 is connected to the sensing signal acquisition and processing system through the shielding joint.

The preparation steps of the piezoresistive/piezoelectric composite material used are as follows:

(1) Preparation of micro/nano piezoelectric ceramic powder

Measure 250g of lead acetate, 130g of tetrabutyl titanate, and 120g of zirconium nitrate as raw materials, firstly dissolve zirconium nitrate and tetrabutyl titanate in 500mL of water and 500mL of ethylene glycol respectively, and then heat and stir at 105-110°C for 1 Add lead acetate and 250mL ethylene glycol one hour later, continue heating at 105-110°C and reflux for 2 hours to obtain lead zirconate titanate piezoelectric ceramic sol, dry and calcinate at 820°C for 3 hours to obtain a particle size of 300- 450nm piezoelectric ceramic powder.

(2) Put 500mL of acetone into the planetary ball mill, dry-mix 100g of 425 sulfoaluminate cement and 15g of Class I fly ash for 5 minutes, and mix with 150g of the piezoelectric ceramic powder prepared in step (1) Ball mill for 15 minutes, then add 1.0g of multi-walled carbon nanotubes with an outer diameter of 20-40nm and a length of 5-15μm produced by CVD process, and 1.5g of polyvinyl alcohol fibers with a diameter of 20μm and a length of 8mm, and then ball mill and mix for 60 minutes.

(3) The mixture obtained in step (2) was further ultrasonically dispersed in an acetone medium for 45 minutes, and volatilized and dried to obtain a mixed powder.

(4) To the mixed powder obtained in step (3), add 30 g of distilled water dissolved with 0.5 g of carboxylate polyether ester block copolymer-based high-efficiency water reducer MPEG, mix well and load it with polytetrafluoroethylene In the stainless steel mold of the membrane, a Φ30mm×5mm disc-shaped thin slice sample was pressed with a universal testing machine under a pressure of 100MPa.

(5) Place the thin slice sample obtained in step (4) in a cement steam curing box (steam 45°C, relative humidity RH 100%) for 3 days, then dry and clean the upper and lower surfaces to be coated with electrodes.

(6) Coat the thin sheet sample obtained in step (5) with a fully covered silver paste electrode, and after drying, polarize it in a silicone oil bath at a DC voltage of 8kV/cm for 1 hour at room temperature. Wrap the polarized disk-shaped sheet with tin foil, and move it to an oven at 60°C for 12 hours for aging.

The packaging shell used is a fiber reinforced resin concrete obtained by mixing cement, fly ash, water-based resin, water-based curing agent, and tough fiber in a weight ratio of 1:0.15:0.4:0.6:0.05. The preparation steps of the package shell are as follows: according to the proportion, 1.0g of polyvinyl alcohol fibers with a diameter of 10-20μm and a length of 8mm are dispersed in 8g of water-based glycidyl ether epoxy resin by high-speed stirring, and then 12g of water-based triethanolamine curing agent is added and mixed. , then add 20g of grade 425 sulfoaluminate cement and 3g of grade I fly ash dry mix, and stir evenly; fix the piezoresistive/piezoelectric sensing element in a stainless steel mold with a polytetrafluoroethylene film (upper and lower electrodes Lead out through the shielding wire and connect the shielding joint), then pour the above fiber reinforced resin concrete mixture into the mold, and move the mold to a vacuum drying oven for 30 minutes of vacuuming; finally use water-based glycidyl ether epoxy resin /Water-based triethanolamine curing agent mixed with 5-fold dilution solution to cover and maintain the surface until the age of 28 days to obtain the self-powered piezoresistive/piezoelectric composite sensor of the present invention. As shown in FIG. 1 , the sensor is arranged between the simply supported bridge deck unit 5 and the support 6 .

The carbon nanotube/polyvinyl alcohol fiber/lead zirconate titanate/cement-based piezoresistive/piezoelectric composite sensor was measured by ASTM C1018 toughness index method, LCR digital bridge, quasi-static measuring instrument, and impedance analyzer. The fracture toughness is 1.037MPa/m ^-1/2 , the DC resistivity is 14.9kΩ.cm, the piezoelectric constant is 76.2pC/N, the dielectric loss is 0.41, and the electromechanical coupling coefficient is 12.8%.

Within the range of load frequency (0.1-50Hz) of traffic engineering structures, for load frequency less than 1Hz, it can generally be considered as static or quasi-static load, such as highway entrance toll stations, weighbridges, parking area monitoring, etc., at this time passed the test Unbalanced output voltage (ΔU ₁₂ ) on both ends of the diagonal of a wire-connected (quasi-)static signal acquisition system 8-bridge (as shown in Figure 1) to obtain a self-powered piezoresistive/piezoelectric The conductance parameter change characteristics of the composite sensor system, and then through the noise signal elimination technology caused by environmental factors well known to those skilled in the art, can realize the accurate extraction of corresponding quasi-static traffic and structural parameters; and for dynamic loads with a frequency greater than 1Hz (Including cyclical, pulse, random load forms), such as vehicle model identification, vehicle speed, traffic flow and corresponding structural stress and deformation detection of fast-moving vehicles on expressways and cross-river (sea) bridges. In order to effectively measure the weak charge generated by the piezoelectric effect of the self-powered piezoresistive/piezoelectric composite sensor system and prevent charge leakage, it can be connected to the dynamic signal acquisition system 7 (including pre-charge/voltage amplifier, A/D analog-to-digital converter, band-pass filter, voltage amplifier and storage/display, etc.) (as shown in Figure 1), to test the self-powered piezoresistive/piezoelectric composite sensor system of the present invention sensitive to dynamic signals The change of the piezoelectric parameters, and then through the signal sensing and noise signal elimination technology well known to those skilled in the art, the accurate extraction of the corresponding dynamic sensing signal is realized.

The power supplies in the static/dynamic signal acquisition systems 7 and 8 can be converted under the inverse piezoelectric effect when the vehicle rolls over the above-mentioned sensors during the traffic monitoring interval through an energy harvesting/discharging control circuit, and then the instantaneous electric energy that is effectively stored can be fed back, Realize the self-supply of monitoring system.

The invention also provides the application of the self-powered piezoresistive/piezoelectric composite sensor system: layout position, manner and quantity. The specific method is: calculate the number of vehicles with the peak number of the dynamic signal of the piezoresistive/piezoelectric composite sensor, calculate the vehicle weight/model with the sum of the responses of the sensors, and calculate with the time difference between the responses of two parallel sensors at a certain distance Vehicle speed; divide the amplitude of the sensor (quasi) static signal before and after loading by the area to calculate the stress, divide the (negative) amplitude by the elastic modulus to calculate the compressive (tensile) strain, and use the sensor response (negative) amplitude to exceed the concrete compressive strength The limit of the (tensile) strength ratio indicates that the corresponding structure is damaged or cracked. Then realize the traffic parameters (such as traffic volume, vehicle speed, vehicle type and vehicle weight, etc.) and structural parameters (axial stress, tensile/compressive strain, bending strain, crack and damage, etc.) real-time detection and damage assessment.

Of course, the self-powered piezoresistive/piezoelectric composite sensor system of the present invention can also be fully embedded in the two ends of the reinforced concrete beam (the corresponding reinforced concrete beam can be reinforced and concreted by methods well known to those skilled in the art), so that More accurate measurement of the speed of passing vehicles.

Example 2

As shown in FIG. 3 , the sensor system is embedded inside the cantilever deck unit 5 .

Others are with embodiment 1.

Example 3

The preparation process and structure of the self-powered piezoresistive/piezoelectric composite sensor are the same as in Example 1. The difference is: the cement used is P.O.42.5R ordinary Portland cement, the micro/nano-scale piezoelectric ceramic powder is lead zirconate titanate powder with a particle size of 400-1100nm prepared by hydrothermal method, and the conductive filler is a diameter of 500nm graphene oxide is grafted with carbon nanofibers with a diameter of 60-100nm and a length of 6-30μm. The tough fiber is a polyimide fiber with a diameter of 5-20μm and a length of 8mm. The water-based resin and corresponding curing agent are water-based phenolic resin and supporting water-based Curing agent and superplasticizer are naphthalene sulfonate formaldehyde condensate series FDN, and the electrodes used are grid-type silver electrodes.

The obtained graphene oxide grafted carbon nanofiber/polyimide fiber/lead zirconate titanate/cement-based piezoresistive/ The fracture toughness of the piezoelectric composite sensor is 0.914MPa/m ^-1/2 , the DC resistivity is 23.7kΩ.cm, the piezoelectric constant is 55.8pC/N, the dielectric loss is 0.40, and the electromechanical coupling coefficient is 11.6%.

Example 4

The preparation process and structure of the self-powered piezoresistive/piezoelectric composite sensor are the same as in Example 1. The difference is: the micro/nano piezoelectric ceramic powder is niobium magnesium lead zirconate titanate ceramic powder with a particle size of 300-600nm obtained by the sol-hydrothermal method, and the conductive filler is -200 mesh micron carbonyl nickel powder. The fiber is polypropylene fiber with a diameter of 50 μm and a length of 10 mm. The water-based resin and corresponding curing agent are water-based melamine-formaldehyde resin and supporting water-based curing agent. The superplasticizer is sulfonated melamine-formaldehyde resin-based SMF. The electrodes used are cross grid Gridded nickel electrodes.

Using the ASTM C1018 toughness index method, LCR digital bridge, quasi-static measuring instrument, and impedance analyzer to measure the obtained nickel powder/polypropylene fiber/lead niobium magnesium zirconate titanate/cement-based piezoresistive/piezoelectric composite sensor The fracture toughness is 0.891MPa/m ^-1/2 , the DC resistivity is 21.3k Ω.cm, the piezoelectric constant is 51.6pC/N, the dielectric loss is 0.43, and the electromechanical coupling coefficient is 14.7%.

Example 5

The preparation process and structure of the self-powered piezoresistive/piezoelectric composite sensor are the same as in Example 1. The difference is that the cement used is P I type 425 Portland cement, the conductive filler is nano-scale carbon black of 60-80nm, and the tough fiber is polypropylene fiber with a diameter of 50μm and a length of 10mm.

The fracture toughness of the obtained carbon black/polypropylene fiber/lead zirconate titanate/cement-based piezoresistive/piezoelectric composite sensor was measured by ASTM C1018 toughness index method, LCR digital bridge, quasi-static measuring instrument, and impedance analyzer The density is 0.924MPa/m ^-1/2 , the DC resistivity is 13.7kΩ.cm, the piezoelectric constant is 40.5pC/N, the dielectric loss is 0.39, and the electromechanical coupling coefficient is 12.6%.

Claims (9)

1. A piezoresistive/piezoelectric composite material, characterized in that it comprises the following components by weight ratio: 100 parts of cement, 105-500 parts of micro/nano piezoelectric ceramic powder, 10-30 parts of pulverized coal Ash, 15-50 parts of water, 0.01-2 parts of superplasticizer, 0.1-10 parts of tough fiber, 0.01-15 parts of conductive filler. 2. The piezoresistive/piezoelectric composite material according to claim 1, wherein the cement is Portland cement or ordinary Portland cement or sulphoaluminate cement; the fly ash is Class I Fly ash; the water is distilled water or deionized water; the superplasticizer is polycarboxylate superplasticizer, aliphatic superplasticizer, sulfamate superplasticizer, melamine One or more combinations of resin-based superplasticizers and naphthalene-based superplasticizers; the tough fiber is polyvinyl alcohol fiber or polypropylene fiber or polyimide fiber; the conductive filler is micro/nano Grade carbon black, micro/nano nickel powder, carbon fiber, carbon nanofiber, carbon nanotube, graphene, graphene oxide grafted carbon fiber, graphene oxide grafted carbon nanofiber or a mixture of several of them. 3. a method for preparing piezoresistive/piezoelectric composite material according to claim 1, is characterized in that, comprises the steps: (1) Preparation of micro/nano piezoelectric ceramic powder; (2) Using acetone as a grinding aid, dry-mix 100 parts of cement and 10-30 parts of fly ash that acts as a lubricant and bridge between the filler and the matrix for 5-10 minutes, and then mix with 105-500 parts of the step ( 1) The prepared piezoelectric ceramic powder was ball-milled for 10-20 minutes, then conductive fillers and tough fibers were added successively, and then ball-milled and mixed gently for 30-60 minutes; (3) Further ultrasonically disperse the mixture obtained in step (2) in an acetone medium for 30-60 minutes, and volatilize and dry to obtain a mixed powder; (4) Add 15-50 parts of water with 0.01-2 parts of superplasticizer dissolved in the mixed powder obtained in step (3), and after mixing, use compression molding to press into thin slices of the actual required shape and size. Sample; (5) Place the thin slice sample obtained in step (4) in a cement steam curing box, and after curing for three days under the condition of steam at 45°C and relative humidity RH100%, dry and clean the upper and lower surfaces to be coated with electrodes; (6) Coat the thin slice sample obtained in step (5) with an electrode, and after drying, polarize it with a high-voltage DC power supply in a silicone oil bath for 1-12 hours at room temperature, and obtain a piezoresistive/ Sensing elements made of piezoelectric composite materials. 4. A sensor using the material according to claim 1, characterized in that it comprises a piezoresistive/piezoelectric composite material layer (1), and an electrode ( 2), the piezoresistive/piezoelectric composite material layer (1) and the electrode (2) are wrapped in the package shell (3), and the upper and lower electrodes are connected through the electromagnetic shielding wire (4) that runs through the package shell, and the sensor is set in Between the support (6) and the supported deck unit (5) or embedded in the deck unit (5). 5 . The sensor according to claim 4 , wherein the electrodes are arranged in the form of full coverage or grid or interdigitated or cross grid. 6 . 6. The sensor according to claim 4, characterized in that the encapsulation shell (3) is made of cement, fly ash, water-based resin, water-based curing agent, tough fiber according to 1:0.1-0.3:0.4-0.8:0.4- A fiber-reinforced resin concrete mixed with a weight ratio of 0.6:_0.01-0.1. 7. The sensor according to claim 6, wherein the cement is Portland cement or ordinary Portland cement or sulphoaluminate cement; the fly ash is Class I fly ash; The water-based resin is water-based epoxy resin or water-based phenolic resin or water-based urea-formaldehyde resin or water-based melamine-formaldehyde resin or water-based polyurethane resin or water-soluble polyimide resin; the water-based curing agent is a special curing agent corresponding to each water-based resin; The tough fiber is polyvinyl alcohol fiber or polypropylene fiber or polyimide fiber. 8. The sensor according to claim 4, characterized in that the electrode (2) is a conductive silver glue electrode or a silver electrode or a nickel electrode. 9. A method for preparing the sensor according to claim 4-8, characterized in that it comprises the following steps: according to the proportion, the tough fiber is first dispersed in the water-based resin by high-speed stirring, then the corresponding curing agent is added to mix, and then cement is added Dry mix the mixture with fly ash and stir evenly; fix the piezoresistive/piezoelectric sensing element in the mold, then pour the above-mentioned fiber-reinforced resin concrete mixture into the mold, and move the mold to vacuum drying before the final setting of the cement Vacuumize and defoam in the box; finally, cover and maintain the surface with water-based resin and corresponding curing agent mixed diluent until 28 days old.

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