Piezoelectric ceramics piece sensor is used for composite material life cycle method of real-timeTechnical field
The present invention relates to composite materials, real-time for composite material life cycle more particularly, to piezoelectric ceramics piece sensorMonitoring method.
Background technique
Advanced composite material has many advantages, such as that specific strength and specific stiffness are high, performance can design, be easy to integrally formed, is lightweightThe ideal material of efficient configuration design is widely used in aerospace, communications and transportation, the latent warship in ocean, petrochemical industry and building and buildsBuild the heavy construction structure in equal fields.However, composite material is in large scale structure due to designing, manufacturing the limitation with detection techniqueThe superior function of upper application is also far from giving full play to, wherein most important reason is the absence of the reality to moulding process solidification processWhen monitor and control, product quality is difficult to ensure.Meanwhile composite material is vulnerable to impact injury, and the most mesh of defect can not be surveyed,Need advanced health monitoring technique ([1] COLPO F, HUMBERT L, BOTSIS J.Characterisation ofresidual st resses in a single fibre compositewith FBG sensor[J].CompositesScience and Technology,2007,67(9):1830-1841).Therefore, to composite material solidification process, processAccurate monitoring in real time is carried out with use process, to improving product quality, reduce cost, ensure that composite structure safety hasHighly important meaning.
Piezoelectric ceramics piece can be achieved on the conversion equipment of positive and negative piezoelectric effect, both can be based on direct piezoelectric effect to dynamicPressure is monitored, and the technologies such as ultrasound detection and supersonic guide-wave monitoring can be realized based on reversed piezoelcetric effect.It is pressed using ceramicsElectric piece is disc structure, radius 4mm, with a thickness of 0.2mm.
The used special material for first packaging ceramic piezoelectric patches, it is desirable that it is low with fusing point, initial strength is highFeature, and be one of resin matrix curing agent and one of modified material, such as polycaprolactone.
Mainly there are ultrasonic method, Fiber Optic Sensor, dielectric method, impedance method and calorifics for composite material solidification monitoring technology at this stageMethod mainly has supersonic guide-wave method, Fiber Optic Sensor, impedance method etc. for composite material structure health monitoring technology.Ultrasonic method is comparedOther monitoring methods have many advantages, such as that precision is high, structure is simple, at low cost.
Monitoring structural health conditions are to be using the distributed sensor networks being permanently integrated in body structure surface or embedded structureBasis is revolutionary innovative technology ([2] CROWLEY D M, WARD C, POTTER K.A status of determining structural intergrityof acceptance criteria and process requirements in advanced compositesmanufacturing,and whether they are fit for purpose[R].SAE Technical Pap-Er.2013), important work can be played in composite structure design, manufacture, military service and the life cycle management of maintenanceWith.
Summary of the invention
The purpose of the present invention is can not carry out life cycle management for existing composite molding and processing monitoring missingThe phenomenon that monitoring, while it being directed to the problems such as complicated for operation, precision is not high, at high cost in existing composite molding monitoring technology,Piezoelectric ceramics piece sensor is provided and is used for composite material life cycle method of real-time.
The present invention the following steps are included:
1) using can packaging ceramic piezoelectric patches and special material formation co-curing sensor；The special material, which uses, gathers oneselfOne of lactone etc.；
2) co-curing sensor is fixed on to the type chamber of mold in advance, co-curing sensor is reserved type chamber metallic channel and sealedAfter solidify；
3) when composite material injects, flow process generates pressure change, and cure sensor generates piezoelectric ceramics piece togetherElectric signal obtains composite material flowing advanced position；
4) composite material, according to supersonic detection method, passes through the variation reality of velocity of wave and amplitude full of being solidified after type chamberWhen monitor curing degree, and co-curing sensor will be integrated in composite material surface after solidifying, directly as monitoring structural health conditions.
In step 2), co-curing sensor and metallic channel are reserved in the mold, the depth of the metallic channel is togetherThe thickness of cure sensor is preferably identical；The sealing can be used identical material and be fixed；The mold can for metal die,One of composite material mould, ceramic material mold, quartz material mold, cement material mold, gypsum material mold etc.；InstituteStating cured temperature can be 60~180 DEG C, keep heating rate uniform, and heating rate is no more than 10 DEG C/min.In the moldSlot should ensure that cavity surface is smooth, sensor arrangement does not influence product surface quality after sensor encapsulation.
In step 3), fiber-reinforced resin matrix compound material is can be used in the composite material or Whisker reinforced resin-base is multipleOne of condensation material etc.；The liquid molding process of the composite material, which can be used, to be vacuumized；The flow front position is to makeResin flow front is incuded with the direct piezoelectric effect of piezoelectric ceramics piece.
In step 4), when the characterization curing degree of the supersonic detection method, velocity of wave V can be usedLThere is sensing in the side=2d/tWhen device and attenuation alpha=(1/d) 20log (A0/ A) characterization curing degree, wherein d is plate thickness, and t is time, A0To emit signal amplitude, ATo receive signal amplitude；When for monitoring structural health conditions, it can be used for supersonic guide-wave technology or acoustic emission；The ultrasound inspectionSurvey method is by co-curing sensor arrangement in composite material work piece side, piezoelectric ceramics piece connection signal capture card is sent outIt penetrates and also receives.
The present invention has technical effect following prominent:
1, easy to operate: the present invention forms co-curing combination sensor using special material and piezoelectric ceramics piece, directly usesSpecial material is encapsulated into mold inside groove again；
2, sensor does not impact composite property: special material be resin curing agent and modified material itOne, if polycaprolactone fusing point is 60 DEG C, technological temperature is more than 60 DEG C and curing reaction is for exothermic reaction, and polycaprolactone energy is completeIt is complete to incorporate resin.
3, sensor does not impact composite gauge: using the heating speed for being no more than 10 DEG C/min, resin existsCan be partially cured when reaching special material fusing point, overall viscosity increases, and special material dosage is seldom, and part can be equal to after thawingCuring agent can ensure that sensor is fixed on composite material surface.
4, system is simple: the reception and transmitting of signal can be carried out with set of system, in life cycle management monitoring allReal-time monitoring can be carried out using only piezoelectric ceramics.
5, the life cycle management monitoring that the present invention is able to achieve composite structure manufacture, is on active service and safeguards, piezoelectric ceramics pieceIt is finally integrated in composite material surface and forms structural healthy monitoring system.Structural healthy monitoring system is present large scale structure, friendshipThe current state-of-the art technological concept of industry, analyzing binding model by Real-time Monitoring Data can be predicted the service life, and ensure the peace of structureFull property and reliability.
Detailed description of the invention
Fig. 1 is the co-curing sensor schematic of the embodiment of the present invention.
Fig. 2 is special material and piezoelectric ceramics piece co-curing sensor schematic of the invention.
Fig. 3 is structural schematic diagram in mold of the invention.
Fig. 4 is the structural schematic diagram after piezoelectric ceramics piece and composite material co-curing of the invention.
Specific embodiment
The present invention is further illustrated with reference to the accompanying drawings and examples.
As shown in figures 1-4.Specific step is as follows for the embodiment of the present invention:
1) using can packaging ceramic piezoelectric patches 3 and the formation co-curing sensor 7 of special material 2；The special material 2 usesOne of polycaprolactone etc.；
2) co-curing sensor 7 is fixed on to the type chamber 6 of mold 10 in advance, co-curing sensor 7 reserves type chamber metallic channel 4And solidify after sealing；Co-curing sensor 7 and metallic channel 8, the depth and co-curing of the metallic channel 8 are reserved in the moldThe thickness of sensor 7 is preferably identical；The sealing can be used identical material and be fixed；The mold 10 can for metal die,One of composite material mould, ceramic material mold, quartz material mold, cement material mold, gypsum material mold etc.；InstituteStating cured temperature can be 60~180 DEG C, keep heating rate uniform, and heating rate is no more than 10 DEG C/min.In the moldSlot should ensure that cavity surface is smooth, sensor arrangement does not influence product surface quality after sensor encapsulation.
3) when composite material 11 injects, flow process generates pressure change, cure sensor 7 together of piezoelectric ceramics piece 3Electric signal is generated, 11 flow front position of composite material is obtained；Fiber-reinforced resin base composite wood can be used in the composite materialOne of material or Whisker Reinforced Polymer Composites etc.；The liquid molding process of the composite material, which can be used, to be vacuumized；The flow front position is that resin flow front is incuded using the direct piezoelectric effect of piezoelectric ceramics piece.
4) composite material 11, according to supersonic detection method, passes through the variation of velocity of wave and amplitude full of being solidified after type chamber 6Real-time monitoring curing degree, and co-curing sensor 7 will be integrated in 11 surface of composite material after solidifying, and supervise directly as structural healthIt surveys.When the characterization curing degree of the supersonic detection method, velocity of wave V can be usedLWhen there is a sensor in the side=2d/t and attenuation alpha=(1/d)20log(A0/ A) characterization curing degree, wherein d is plate thickness, and t is time, A0To emit signal amplitude, A is to receive signal amplitude；When for monitoring structural health conditions, it can be used for supersonic guide-wave technology or acoustic emission；The supersonic detection method, being will be solid altogetherChange sensor 7 and be arranged in composite material work piece side, piezoelectric ceramics piece connection signal capture card is made to emit also to receive.
Special material (such as polycaprolactone) and piezoelectric ceramics piece co-curing sensor are made in advance, and sensor is fixed in advanceIt is sensed in tank 5 and type chamber metallic channel 4 in mold cavity co-curing, groove depth cure sensor consistency of thickness, and reserved type togetherChamber metallic channel 4, is finally sealed using special material, to determine that special material has been fully cured；According to composite wood feed liquidBody formed technique requirement, in resin injection, flow process can generate pressure change, according to direct piezoelectric effect, piezoelectric ceramics pieceCo-curing sensor can generate electric signal, obtain resin flowing advanced position；Resin is solidified after being full of type chamber, according to ultrasoundTesting principle, by the variation of velocity of wave and amplitude come real-time monitoring curing degree；Piezoelectric ceramics piece sensor will integrate after hardeningComposite material surface, and composite material composed structure health monitoring systems, can be used active supersonic guide-wave monitoring technology andPassive type acoustic emission carries out real-time monitoring to composite structure integrality and damage.
In Fig. 1, label 1 is conducting wire, and 9 be seal groove.
The present invention is further illustrated below with composite liquid moulding process, and (special material selection gathers in oneselfEster).
As indicated with 1, the radius of piezoelectric ceramics piece is 4mm to co-curing sensor schematic of the invention, with a thickness of 0.2mm.Piezoelectric ceramics piece is integrally packaged using polycaprolactone, is still wafer type after encapsulation, radius 4.1mm, with a thickness of0.4mm。
The process for producing composite material that the present invention takes is liquid molding process.Mold shape is as shown in Fig. 2, selected moldOuter dimension is 600mm × 600mm × 40mm, and internal cavity is having a size of 400mm × 400mm × 3mm.With the intracavitary arrangement 4 of typeFor piezoelectric ceramics piece sensor, first opening four radiuses in mold cavity inner surface is 4.1mm, the counterbore slot of thickness 0.4mm, holeShoulder radius is 4.2mm, depth 0.1mm.The conducting wire used is the enameled wire of diameter 0.05mm, and 0.1mm length and width are opened in moldHigh metallic channel.Then encapsulation sensor and conducting wire are put into counterbore slot and metallic channel, and encapsulate sensing again with polycaprolactoneDevice removes extra polycaprolactone, guarantees that mould inner surface is smooth and polycaprolactone has been fully cured.Then according to liquid molding workSkill, coating release agent put the carbon fiber unidirectional cloth of 400mm × 400mm size, and 8 layers of cloth of laying are pressed [0/90/ ± 45]sAngle pavingIt puts.Vacuum is extracted after the laying release cloth of the top, borrows vacuum indentation resin can be to polycaprolactone table when resin flows through sensorFace generates a dynamic pressure, is eventually transferred to piezoelectric ceramics piece, generates electric signal, by sensor whether generate electric signal comeJudge whether resin flows through sensitive zones.After resin is full of type chamber, mold is put into insulating box and is heated in 80 DEG C30min, waits completion to be solidified, and when solidification, resin becomes solid from liquid, on the mechanical properties such as modulus and Poisson's ratio are started from scratchRise, and also with the physical-chemical reactions such as crosslinking, heat release, can velocity of wave to ultrasonic signal and amplitude have an impact, pass throughThe velocity of wave V of ultrasonic signalL=2d/t and amplitude α=(1/d) 20log (A0/ A) change to characterize curing degree, pass through following formula:
Use formulaWithCarry out accurate calculating curing degree.ρ is resin density, α in formulaUSTableShow that curing degree, L indicate resin storage volume modulus, L0Indicate initial volume modulus (when solidification does not complete), LfIndicate maximum storageBulk modulus (when solidification is completed).
Finally mold is taken out, opens mold, the co-curing product of sensor and finished product composition is taken out, carries out surface letterSingle processing.Shape is as shown in Figure 3.The sensing network of piezoelectric ceramics piece sensor composition has been permanently integrated at composite structureSurface can be used for the active monitoring based on supersonic guide-wave technology and the passive type monitoring based on acoustic emission.From resinThe monitoring structural health conditions of flow front finally, can in a set of acquisition system data acquisition.
It is monitored from producing to being worked into using whole life cycle in conclusion the present invention can be used for composite material, andWhole process can be monitored using only piezoelectric ceramics piece sensor, is not necessarily to other sensor-based systems.
The present invention provides a kind of methods that piezoelectric ceramics piece sensor is used for composite material life cycle real-time monitoring, mainWanting step includes: that piezoelectric ceramics piece positive and negative anodes are connected conducting wire, first uses special material packaging ceramic piezoelectric patches, which answersComposite property is not influenced, and the material is required to have the characteristics that fusing point is low, initial strength is high, and is the solidification of resin matrixOne of agent or one of modified material, such as polycaprolactone；The special material of molten condition is imported in the mold having had been prepared for andPiezoelectric ceramics piece is formed by curing encapsulation sensor；Then sensor is put into mold preformed groove, will be sensed using identical materialDevice and its fixed encapsulation of conducting wire；Remaining process flow is carried out according to composite liquid moulding process, and resin injection flowing can produceRaw dynamic pressure is transmitted to piezoelectric ceramics sector-meeting and generates electric signal；Material mechanical performance enhances at any time when solidification, can be to ceramicsThe ultrasonic velocity and amplitude size that piezoelectric patches generates have an impact；Workpiece is taken out in demoulding after curing molding and piezoelectric ceramics piece is totalCured article.The present invention not only realizes real-time monitoring composite liquid forming process, but also finally by piezoelectric ceramics piece groupAt sensing network can co-curing in composite material surface, can be used for the health monitoring technique of composite structure, to be compoundMaterial monitors from design, manufacture, military service and the life cycle management of maintenance and provides technical support.