CN105043458A - Device and method for on-line detection of lightning damage of fiber composite material - Google Patents
Device and method for on-line detection of lightning damage of fiber composite material Download PDFInfo
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Abstract
The invention discloses a device and method for on-line detection of lightning damage of a fiber composite material. The device comprises a twin-lead array type temperature fiber bragg grating, a twin-lead array type strain fiber bragg grating, two optical fiber couplers, a fiber bragg grating demodulator and a processor. The two ends of each fiber bragg grating are both used as leads, and the fiber bragg gratings are connected with the demodulator through the couplers, so that two independent optical signal channels are formed. After optical fibers are struck by lightning to be broken, each twin-lead fiber bragg grating can be used as two independent single-lead fiber bragg gratings. The gratings are embedded in the composite material, the temperature and the strain of structural components of the composite material are subjected to offset detection through central wavelengths, data are processed through lightning damage detection system software, and a three-dimensional distribution result on the lightning damage degree of the structural components of the composite material is formed, output and displayed. By the adoption of the device and method, the on-line detection problems that the traditional lightning striking process is transient and cannot be captured easily, and lightning striking damages a sensor, a transient electromagnetic field interference detection system, a lightning surge damage detector and the like are solved.
Description
Technical field
The present invention relates to a kind of fibrous composite lightning damage on-line measuring device and method.
Background technology
Fibrous composite has the plurality of advantages such as high strength, low-density, corrosion-resistant, antifatigue, is Aero-Space ideal structure material, has been widely used in aerospace flight vehicle at present, especially in aircraft structure, play extremely important effect.Such as, in Boeing 787 and Air Passenger A350XWB aircraft, compound substance consumption is more than 50%, this wherein major part be carbon fibre composite and glass fiber compound material.
According to statistics, the every airplane average flight of China will suffer to be struck by lightning for 1 time for 3000 hours in statistical significance, in the flight of thunderstorm prone areas, suffers lightning strike probability to improve several times.Fibrous composite replaces metal material, and intensity improves, and quality alleviates, but electrical and thermal conductivity is not as metal material, more easily damages after being struck by lightning.There will be three kinds of degree of impairments: slight damage, heavier damage and major injury after aircraft is struck by lightning.Slight damage then can continue flight, overhauls after can landing; Heavier damage needs to land immediately and keeps in repair or make a return voyage; Major injury may cause fatal crass.After aircraft is struck by lightning, the accident of fatal crass is of common occurrence.
Thunderstorm causes serious potential safety hazard to aircraft flight, but aircraft aloft flies, cannot be completely lightning-arrest, the process how on-line monitoring Aircraft Composite Structure part is struck by lightning and the degree of injury after being struck by lightning, to determine whether to make a return voyage immediately maintenance, this, concerning significant aircraft safety and operation cost, enjoys Air Branch to pay close attention to.On-line checkingi compound substance lightning damage position, damaged area, lesion depths, and assessment composite material structural member be struck by lightning after residual intensity, to Flight Safety, there is extremely important practical value.
Thunder and lightning is the strong electromagnetic phenomenon that a kind of moment (hundreds of microsecond) occurs, and electric current huge (can up to 200kA), is difficult to accomplish on-line checkingi.Be conventionally used to compound substance lightning damage detecting sensor and mainly contain three defects in use: (1) adopts the micro-electric current of sensor as signal, thunderbolt can produce huge transient electromagnetic field when occurring, undesired signal is transmitted, or sensor circuit can produce induction current, or lightning current enters sensor loop, cause whole sensor, detector circuit destroys by lightning surge; (2) traditional sensors self is affixed on aircraft surfaces or implants inner, if be affixed on aircraft surfaces, be difficult to test material internal injury, also easily suffer to be struck by lightning directly damage, and being embedded in aircaft configuration inside in advance can have an impact to composite material strength, easily causes stress to concentrate; (3) nearly all sensor all can be damaged by thunderbolt directly, loses measuring ability.Sensor does not affect by the transient electromagnetic field of thunder and lightning, still can survive after running into thunderbolt, composite inner damage can be detected, but can not produce obviously impact to composite material structural member intensity, become the important prerequisite condition of composite material structural member lightning damage on-line checkingi.
Summary of the invention
The present invention is in order to solve the problem, propose a kind of fibrous composite lightning damage on-line measuring device and method, this device utilizes double lead arrayed optical fiber grating to be sensor, composite inner after Real-Time Monitoring is struck by lightning is damaged, and effectively solves the of short duration difficult problem being difficult to the on-line checkingi such as seizure, thunderbolt damage sensor, transient electromagnetic field Interference Detection system, lightning surge damage detecting device of traditional lightning stroke process.
To achieve these goals, the present invention adopts following technical scheme:
A kind of fibrous composite lightning damage on-line measuring device, comprise double lead array optical fiber temperature grating, double lead array strain fiber grating, two fiber couplers, fiber Bragg grating (FBG) demodulator and processor, wherein: light source produces laser signal, laser signal is divided into two-way through conduction optical fiber, be transferred to the first fiber coupler and the second fiber coupler respectively, first fiber coupler connects one end lead-in wire of double lead array optical fiber temperature grating and double lead array strain fiber grating, other end lead-in wire connection second fiber coupler of double lead array optical fiber temperature grating and double lead array strain fiber grating, form two and have the port that laser is incident and reflect concurrently, all fiber gratings of double lead array optical fiber temperature grating, double lead array strain fiber grating are embedded in composite material structural member inside all in advance, after laser signal and fiber grating interact, reflects laser enters first, second fiber coupler again respectively by two ends lead-in wire, the light signal that first, second fiber coupler exports enters fiber Bragg grating (FBG) demodulator, settling signal demodulation, fiber Bragg grating (FBG) demodulator connection handling device, processor is according to the result of signal analysis fibrous composite type of impairment, degree and distribution thereof.
Described double lead array optical fiber temperature grating is parallel with double lead array strain fiber grating, arranged adjacent, each temperature raster unit in double lead array optical fiber temperature grating and double lead array strain each strain raster unit one_to_one corresponding of fiber grating, thus make two corresponding gratings on optical fiber temperature and adjacent strain optical fiber constitute a double lead fiber grating pair.
Described light source is the laser instrument be built in fiber Bragg grating (FBG) demodulator, and laser instrument produces continuous frequency modulation laser, enters double lead array optical fiber temperature grating, double lead array strain fiber grating, form stable reflected signal by lead-in wire.
Described double lead array optical fiber temperature grating, double lead array strain fiber grating is double lead structure, namely each grating has two to go between connected, article two, lead-in wire all can as the signalling channel of raster unit, as long as each grating has a bars passage just to can be used for input; Even if grating damage fracture, as long as grating also has a lead-in wire to be connected with external detection system, just can keep optical fibre channel, ensure the survival of fiber grating and the transmission of detection signal in lightning stroke process.
Described double lead array optical fiber temperature, double lead array strain optical fiber all comprises multiple raster unit being carved with different centre wavelength, and each raster unit is all independently sensor units.
Described processor, comprise Geometric Modeling module, fiber grating signal resolution module, damage of composite materials database and lightning damage inverting graphical interfaces, wherein, described Geometric Modeling module, for carrying out modeling to composite material structural member, in compound substance geometric model, accurately mark the position of raster unit; Described fiber grating signal resolution module, for the wavelength signals that analytical calculation fiber Bragg grating (FBG) demodulator transmits, obtain the temperature of fiber composite structure part, strain and stress, the information stored is contrasted, judge type of impairment and degree of injury in itself and damage of composite materials database; Described lightning damage inverting graphical interfaces, for being finally inversed by compound substance lightning damage distributed in three dimensions situation and exporting.
Based on a detection method for said apparatus, comprise the following steps:
(1) before composite material solidification is shaping, the spacing as required according to setting in structural member lays double lead array optical fiber temperature grating, double lead array strain fiber grating;
(2) composite material structural member curing molding, fiber-optic grating sensor is embedded in composite material structural member inside, connects the first fiber coupler, the second fiber coupler, fiber Bragg grating (FBG) demodulator and processor;
(3) light source produces laser signal, after laser signal enters the first fiber coupler, the second fiber coupler, double lead array optical fiber temperature grating, double lead array strain fiber grating region is entered respectively by two ends lead-in wire, signal after optical grating reflection is through the first fiber coupler, the second fiber coupler back light gate signal (FBG) demodulator, and light signal is demodulated to digital signal and enters processor process;
(4) set up the 3-D geometric model of composite material structural member by Geometric Modeling module, raster unit is numbered by coordinate relationship marking on the three-dimensional model of composite material structural member; Grating signal parsing module resolves the signal that grating signal (FBG) demodulator sends, and according to the information that double lead array optical fiber temperature grating, double lead array strain fiber grating gather, obtains compound substance strain, temperature and STRESS VARIATION;
(5) compound substance lightning damage database is called, identification of damage type and judge degree of injury, obtain type of impairment and the degree of raster unit numbering place compound substance regional area, type of impairment and degree are passed through stop position data inversion on geometric model, obtains the dynamic solid distribution plan of compound substance lightning damage.
In described step (1), concrete grammar is: before composite material solidification is shaping, lay according to certain spacing the fiber grating pair that m is carved with n grating sensor as required in structural member, optical fiber label is 1,2,3, m, raster unit label is 1,2,3, n, each grating pair there are two fiber gratings, article one, be the optical fiber temperature grating of measuring tempeature, be labeled as T, another is the strain fiber grating of monitor strain, be labeled as S, form two array optical fiber grating sensor.
In described step (4), when thunderbolt energy is low, fiber grating is intact, it is identical that two ends lead-in wire collects grating sensor cell signal, adopt any one end input, cause damage of composite materials serious to thunderbolt energy, cause fibercuts, double lead fiber grating becomes two single wire fiber gratings, grating sensor still can carry out detection and transmission of signal, now the signal of two ends lead-in wire transmission all wants check processing, whether damaged by the signal difference determination raster unit district contrasting two lead end port transmissions, and determine the position in the raster unit district of damaging, quantity.
In described step (5), realized measured detection by the drift of measuring raster center wavelength, express raster center wavelength, and raster center wavelength is with the drift of stress and temperature, is strained and temperature-responsive.
In described step (5), the temperature computation method of compound substance is: by recording the centre wavelength in the optical fiber temperature optical grating calibration situation under different temperatures and the centre wavelength in strain optical fiber grating temperature demarcation situation, the linear relationship of then matching centre wavelength and temperature, obtain grating temperature coefficient, then obtain the temperature of compound substance.
In described step (5), the strain calculation method of compound substance is: according to the knots modification of strain fiber bragg grating center wavelength and the fitting function difference equation of optical fiber temperature grating and the demarcation of strain optical fiber grating temperature, calculate the dependent variable of compound substance, bonded composite modulus, calculates compound substance stress.
Beneficial effect of the present invention is:
(1) the invention provides a kind of compound substance lightning damage on-line measuring device, solve the of short duration difficult problem being difficult to the on-line checkingi such as seizure, thunderbolt damage sensor, transient electromagnetic field Interference Detection system, lightning surge damage detecting device of traditional lightning stroke process;
(2) the present invention adopts double lead fiber-optic grating sensor, has an impact hardly to composite material structural member strength and stiffness, can detect composite inner damage simultaneously.After being struck by lightning, double lead fiber-optic grating sensor can become two independently single wire fiber grating sensors, and after composite material structural member is damaged, the fiber-optic grating sensor of survival still can normally work;
(3) the invention provides the method for compound substance lightning damage on-line checkingi and signal transacting, lightning damage situation is detected by the change of the strain in lightning stroke process, temperature, and the type of impairment of stereo display composite material structural member directly perceived and degree of injury distribution.
Accompanying drawing explanation
Fig. 1 is the FBG pick-up unit schematic diagram of composite material structural member lightning damage;
Fig. 2 becomes two independently single wire fiber grating schematic diagram after double lead fiber grating is struck by lightning;
Fig. 3 is the schematic diagram of double lead arrayed optical fiber grating pair;
Fig. 4 is the centre wavelength of grating and the demarcation of temperature relation and matched curve;
Fig. 5 (a) is the raster center wavelength variations of fiber-optic grating sensor measurement compound substance thunderbolt temperature-fall period;
Fig. 5 (b) is the temperature variation of fiber-optic grating sensor measurement compound substance thunderbolt temperature-fall period.
Embodiment:
Below in conjunction with accompanying drawing and embodiment, the invention will be further described.
A kind of compound substance lightning damage on-line measuring device, this device with double lead arrayed optical fiber grating for sensor, the change of the strain of on-line monitoring composite material structural member lightning stroke process, stress and temperature, by the computer aided detection software of lightning damage, Bragg grating signal is processed, judge lightning damage type, calculate lightning damage degree.
Double lead arrayed optical fiber grating pair is made up of two double lead fiber gratings: an optical fiber temperature grating and a strain fiber grating, and optical fiber temperature grating is used for measuring tempeature, and strain fiber grating is used for monitor strain.Article two, optical fiber is arranged in parallel and adjacent, all draws with double lead, forms a double lead fiber grating pair.
Select double lead fiber grating pair as sensor advantage mainly: fiber grating adopts double lead structure, after suffering thunderbolt fracture, 1 double lead fiber-optic grating sensor can become 2 single wire fiber grating sensors, still can play sensor effect.Fiber grating can detect strain and the temperature variation of compound substance, and the STRESS VARIATION of Calculating material, can accurate characterization compound substance lightning damage process by the change of strain, stress and temperature.Fiber grating diameter is only equivalent to the several times of carbon fiber diameter, imbeds fibrous composite inside and does not almost have an impact to composite property.In addition, fiber grating adopts light signal to be sensed signal sources, not by the interference of Lightning Electromagnetic Fields.
A kind of compound substance lightning damage on-line measuring device concrete structure mainly comprises: double lead arrayed optical fiber grating pair, fiber coupler, fiber Bragg grating (FBG) demodulator (built-in laser instrument), computing machine etc.
The built-in laser instrument of fiber Bragg grating (FBG) demodulator produces laser signal, A, B two paths are divided into enter fiber coupler A and fiber coupler B through conduction optical fiber, fiber coupler A connects the A end lead-in wire of double lead fiber grating, fiber coupler B connects the B end lead-in wire of double lead fiber grating, forms the port that two have laser incidence and reflection concurrently.Fiber grating is embedded in composite inner, after laser signal and grating interact, reflects laser enters fiber coupler A, B again respectively by A, B lead-in wire, the signal going out coupling mechanism returns fiber Bragg grating (FBG) demodulator, the digital signal that computing machine can identify is become after optical signal demodulation, through the processing process of the computer aided detection software of lightning damage, form the result of type of impairment, degree and distribution thereof in a computer, and output display.
The built-in laser instrument of fiber Bragg grating (FBG) demodulator can produce continuous frequency modulation laser, and laser signal enters Bragg grating by lead-in wire, forms stable reflected signal.
Double lead arrayed optical fiber grating pair is double lead structure, namely each grating has two to go between connected, each grating has two light paths, even if grating damage fracture in lightning stroke process, as long as grating also has a lead-in wire to be connected with external detection system, just can keep optical fibre channel, ensure the survival of fiber grating and the transmission of detection signal.
Double lead arrayed optical fiber grating pair is made up of two double lead fiber gratings: an optical fiber temperature grating and a strain fiber grating, and optical fiber temperature grating is used for measuring tempeature, and strain fiber grating is used for monitor strain.Article two, optical fiber is parallel and adjacent, raster unit one_to_one corresponding, all draws with double lead, forms a double lead fiber grating pair.
Double lead arrayed optical fiber grating, the optical fiber fabrication arrayed optical fiber grating in the even thinner footpath of preferred cladding diameter 35-45 micron, the grating of thinner diameter can reduce the impact of optical fiber embedding on composite material strength and rigidity to a greater degree.
Every bar optical fiber is scribed the raster unit of 1-20 different centre wavelength, be preferably 6-16 raster unit, each raster unit is all independently sensor units, and many optical fiber having scribed multiple grating can form optical fiber optical grating array.
Double lead arrayed optical fiber grating can detect strain and the temperature variation of composite material structural member lightning stroke process, bond material parameter, can the STRESS VARIATION of Calculating material lightning stroke process.
Coupling mechanism is fiber grating signal coupler, has excellent wavelength chooses ability and the characteristic of multiport, is the fiber coupler that compact conformation, loss are little, polarization is irrelevant.
Fiber Bragg grating (FBG) demodulator is high-speed high frequency optic fiber grating wavelength (FBG) demodulator, has at a high speed and the demodulation scheme of multi-channel parallel, realizes signal fast demodulation, meets thunderbolt and detects needs.Fiber Bragg grating (FBG) demodulator is connected by data line with computing machine, and the light signal fast demodulation that the grating after thunderbolt moment and thunderbolt is returned is digital signal.
Computing machine is furnished with lightning damage inspection software, and software comprises Geometric Modeling module, fiber grating signal resolution module, damage of composite materials database and lightning damage inverting graphical interfaces.By the Geometric Modeling module of software to composite material structural member modeling, in compound substance geometric model, accurately mark the position of raster unit; Signal receiving module analysis calculates the wavelength signals that fiber Bragg grating (FBG) demodulator transmits, and obtains the temperature of fiber composite structure part, strain and stress, then with the contrast of damage of composite materials database, is used for judging type of impairment and degree of injury.Be finally inversed by compound substance lightning damage distributed in three dimensions situation by graphical interfaces, export at graphical interfaces.
For achieving the above object, the invention provides the method that this device carries out fibrous composite lightning damage on-line checkingi, step is as follows:
(1) the optical fiber inscribing fiber grating in the even thinner footpath of cladding diameter 35-45 micron is selected, multiple raster unit scribed by every bar optical fiber, raster unit label is 1,2,3, n, lead-in wire is drawn from sensors A, B two ends, and is demarcated the temperature coefficient of grating respectively.
(2) select two fiber gratings to set up fiber grating pair, a fiber grating is used for measuring tempeature, and be labeled as T, another fiber grating monitor strain, is labeled as S, the tiny stainless-steel tube of the equal overcoat of optical fiber temperature grating of mark T, mouth of pipe rubber seal.
(3) before composite material solidification is shaping, lay according to certain spacing the fiber grating pair that m is carved with grating sensor as required in structural member, optical fiber label is 1,2,3, m, each grating pair there are an optical fiber temperature grating and a strain fiber grating, every bar optical fiber there is n sensor unit (raster unit), form two array (temperature matrices T [m × n] and strain matrix S [m × n]) fiber-optic grating sensor.
(4) with plastic tape parcel protection fiber grating lead-in wire, according to technique, composite material structural member curing molding, fiber-optic grating sensor is embedded in composite material structural member inside.
(5) after composite material structural member curing molding, the A of every bar fiber-optic grating sensor is held each corresponding ports of lead-in wire connecting fiber coupling mechanism A front end, the B of fiber-optic grating sensor is held each corresponding ports of lead-in wire connecting fiber coupling mechanism B front end, coupling mechanism back-end ports is by intelligent acess fiber Bragg grating (FBG) demodulator, and grating demodulation instrument connects computing machine by data line.
(6) (FBG) demodulator is opened, built-in laser instrument produces laser signal, after laser signal enters coupling mechanism, lead-in wire is held to enter grating region respectively by A, B, signal after optical grating reflection returns coupling mechanism, through coupling mechanism back light gate signal (FBG) demodulator, light signal is demodulated to digital signal and enters computer disposal.
(7) the computer aided detection software analyzing and processing (FBG) demodulator signal of lightning damage, obtains lightning damage distribution, interface output display.
In step 1, raster unit marks 1 to n from A end lead-in wire successively to B end lead-in wire, and centre wavelength increases successively, and increment is 4nm.
Grating pair in step 2 is made up of an a temperature survey grating T and strain measurement grating S, and two fiber gratings walk abreast, and ensures the raster unit T of optical fiber temperature
kithe S of (in kth group grating pair i-th temperature grating) and strain grating
ki(in kth group grating pair i-th strain grating) position is corresponding, and temperature grating needs the tiny stainless-steel tube of overcoat, mouth of pipe rubber seal.
Fiber grating pair sensor, before composite material solidification is shaping, is layered on composite material structural member inside by step 3, and in order to ensure stable performance and the survival rate of grating sensor, the right laying direction of optical fiber is as far as possible identical with the composite fiber laying angle of next-door neighbour.
In step 6, grating demodulation instrument connects computing machine by data line, and computing machine is furnished with lightning damage on-line checkingi software.This software comprises several large modules such as Geometric Modeling module, fiber grating signal resolution module, compound substance lightning damage database and lightning damage inverting graphical interfaces.
In step 7, have selectivity to the process of the grating signal that grating two goes between, because thunder energy is different in lightning stroke process, the lightning damage degree produced compound substance is also different; The damage of composite material structural member diverse location is also different, and near lightning strike spot, damage is serious, lighter away from the damage of lightning strike spot position.If damage of composite materials is comparatively light, grating is intact, and it is identical that optical fiber side a and b lead-in wire collects grating sensor cell signal, can adopt any one end of A, B input.When the energy that is struck by lightning is higher, damage of composite materials seriously causes fibercuts, in this case a double lead fiber grating becomes two single wire fiber gratings, and grating sensor still can carry out detection transmission of signal, now A, B go between two end signals all will by computer disposal.Whether damaged by the signal difference determination raster unit district of contrast A and B lead-in wire port, and determine position, the quantity in the raster unit district of damaging.
In step 7, lightning damage inspection software test material structural damage process is as follows:
Set up the 3-D geometric model of composite material structural member by Geometric Modeling module, raster unit is numbered by coordinate relationship marking on the three-dimensional model of composite material structural member; Grating signal parsing module resolves the signal that sends of (FBG) demodulator, obtains compound substance strain, temperature and STRESS VARIATION, calls compound substance lightning damage database, identification of damage type and judge degree of injury; Obtain type of impairment and the degree of raster unit numbering place compound substance regional area, type of impairment and degree are passed through stop position data inversion on geometric model, obtains the dynamic solid distribution plan of compound substance lightning damage, exported by Computer display.
The signal that step 7 Computer process (FBG) demodulator transmits and solve composite temperature, strain and stress principle as follows:
Realized measured detection by the drift of measuring raster center wavelength, raster center wavelength X
bcan be expressed as:
λ
B＝2nΛ
Wherein, λ
bfor the centre wavelength of grating; Λ is screen periods; N is refractive index.
λ
bdrift with stress and temperature is:
Wherein, Δ λ
bfor fiber bragg grating center wavelength variable quantity; ε is additional strain; P
i,jfor the photoelastic tensor coefficient of optical fiber; V is fiber optic materials Poisson ratio; α is the thermal expansivity of fiber optic materials; Δ T is temperature variation.
Strain and temperature-responsive result can be derived in conjunction with two formula above, as shown in the formula:
In formula, K
tfor the temperature sensitive coefficient of fiber bragg grating center wavelength drift; K
εfor the gage factor of fiber bragg grating center wavelength drift.
(1) composite temperature calculates
The temperature grating of each fiber grating centering, the ess-strain transmission of foreign material and grating sensor isolated by the stainless-steel tube of overcoat, and extraneous strain does not have an impact to raster center wavelength, and the knots modification of raster center wavelength only changes relevant with material temperature.Temperature grating needs to demarcate temperature coefficient, by recording the raster center wavelength under different temperatures, the linear relationship of then matching centre wavelength and temperature, obtains grating temperature coefficient.
A fiber grating centering, centre wavelength and the temperature foh relation of the surely rear temperature grating of bidding and strain grating are as follows:
λ
BT1＝k
T1T+λ
10
λ
BT2＝k
T2T+λ
20
In formula, λ
bT1for the centre wavelength in temperature optical grating calibration situation; λ
bT2for the centre wavelength in strain grating temperature demarcation situation; k
t1for the temperature coefficient of temperature grating; k
t2for straining the temperature coefficient of grating; T is composite temperature.
Two close fiber optic of fiber grating centering are adjacent, and position is corresponding, temperature grating T
kiwith strain grating S
kitemperature identical, so the temperature of compound substance is:
By above formula, temperature raster center wavelength is utilized just to obtain the temperature variation of compound substance.
(2) compound substance strain calculation
The knots modification of strain raster center wavelength is caused jointly by the strain of temperature variation and compound substance, is expressed as:
Δλ
B2＝k
ε2ε+k
T2ΔT
In formula, k
ε 2for straining the coefficient of strain of grating; k
t2for straining the temperature coefficient of grating; ε
εfor the strain of compound substance; Δ T is the temperature variation of compound substance.
The difference equation of the fitting function that two in grating pair corresponding grating sensor cell temperatures are demarcated is:
Δλ
BT1＝k
T1ΔT
Δλ
BT2＝k
T2ΔT
In conjunction with above various, compound substance dependent variable is:
(3) compound substance Stress calculation
According to modulus and the strain of compound substance, in certain temperature range, can direct solution compound substance stress:
σ＝Eε
In formula, σ is compound substance stress; E is compound substance modulus.
Case study on implementation 1:
A kind of 360mm × 360mm, [45/0/-45/90]
4Scarbon fibre composite slab construction part lightning damage pick-up unit and method.Optical fiber Bragg grating sensor take light signal as detection signal, and carrier is quartz fibre (glass fibre), and diameter is very thin, is only the several times of carbon fiber diameter.Optical fiber Bragg grating sensor is detect foundation with center wavelength shift, and precision is high, not only may be used for material strain and detects, also can be used for temperature detection, is the ideal transducer that compound substance lightning damage detects.Select optical fiber Bragg raster in the present embodiment.
Device comprises (as Fig. 1): double lead array optical fiber Bragg grating pair, fiber coupler, optical fibre grating digital demodulation instrument (built-in laser instrument), computing machine etc.
Optical fiber Bragg raster adopts double lead structure, after suffering thunderbolt fracture, 1 double lead fiber-optic grating sensor can become the fiber-optic grating sensor (as Fig. 2) of 2 single lead-in wires, and grating also can normally work, and ensures the sustainability of lightning stroke process on-line checkingi.
1, according to structural member size, grating scribed by the optical fiber of 18 cladding diameters 40 μm, every bar optical fiber is scribed the raster unit of 9 different centre wavelengths, raster unit respectively label is 1-9, each raster unit total length is 40mm, wherein grating etching region length 10mm, grid region are spaced apart 30mm, and hold B to hold raster center wavelength to increase gradually from A, the increment of each centre wavelength is 4nm.
2, the temperature coefficient of every bar fiber grating is demarcated, matching centre wavelength and temperature relation, obtain the temperature coefficient of grating.
3, select two fiber gratings to set up grating pair (as Fig. 3), wherein one is overlapped stainless-steel tube in raster unit, and rubber seal, article 18, optical fiber forms 9 groups of fiber grating pairs, be labeled as 1-9 to fiber grating pair, temperature grating marker is T, and strain grating marker is S.
4, according to [45/0/-45/90]
4Sply sequence is laid 360mm × 360mm carbon fibre initial rinse fabric on flat plate mold, after having spread sheet material the 16th laying (90 ° of layings), before spreading the 17th laying (90 ° of layings), the optical fiber of 9 groups of fiber grating pairs is placed on prepreg according to equidistantly (40mm) is parallel in 90 ° of directions, optical fiber to two ends go between A, B apply tension force, then spread 17-32 layer carbon fibre initial rinse fabric.
5, optical fiber two ends lead-in wire A, B packing protective layer, moves in former, according to the technique curing molding made by composite material preformed body and mould.Article 18, two array (temperature matrices T [9 × 9] and strain matrix S [9 × 9]) the formula sensor of fiber grating composition.
6, solidification after the laminate demoulding and be installed on artificial lightning damage test platform, fiber grating A, B two ends lead-in wire switch-in coupler A, B respectively, coupling mechanism A, B are by conduction Fiber connection grating demodulation instrument, grating demodulation instrument is by RJ45 joint twisted pair line connection computer, inspection software is had in computing machine, fiber grating data can be processed, and three-dimensional modeling, output display damage profile.
Temperature survey needs to demarcate grating temperature coefficient, and Fig. 4 is that the strain of grating and temperature relation are demarcated and matched curve.Fig. 5 is the data that grating sensor measures that composite temperature reduces process, and wherein Fig. 5 (a) is a certain raster center wavelength variations, and Fig. 5 (b) is the temperature variation after converting.
By reference to the accompanying drawings the specific embodiment of the present invention is described although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various amendment or distortion that creative work can make still within protection scope of the present invention.
Claims (10)
1. a fibrous composite lightning damage on-line measuring device, it is characterized in that: comprise double lead array optical fiber temperature grating, double lead array strain fiber grating, two fiber couplers, fiber Bragg grating (FBG) demodulator and processor, wherein: light source produces laser signal, laser signal is divided into two-way through conduction optical fiber, be transferred to the first fiber coupler and the second fiber coupler respectively, first fiber coupler connects one end lead-in wire of double lead array optical fiber temperature grating and double lead array strain fiber grating, other end lead-in wire connection second fiber coupler of double lead array optical fiber temperature grating and double lead array strain fiber grating, form two and have the port that laser is incident and reflect concurrently, all fiber gratings of double lead array optical fiber temperature grating, double lead array strain fiber grating are embedded in composite material structural member inside all in advance, after laser signal and fiber grating interact, reflects laser enters first, second fiber coupler again respectively by two ends lead-in wire, the light signal that first, second fiber coupler exports enters fiber Bragg grating (FBG) demodulator, settling signal demodulation, fiber Bragg grating (FBG) demodulator connection handling device, processor is according to the result of signal analysis fibrous composite type of impairment, degree and distribution thereof.
2. a kind of fibrous composite lightning damage on-line measuring device as claimed in claim 1, it is characterized in that: described double lead array optical fiber temperature grating is parallel with double lead array strain fiber grating, arranged adjacent, each temperature raster unit in double lead array optical fiber temperature grating and double lead array strain each strain raster unit one_to_one corresponding of fiber grating, thus make two corresponding gratings on optical fiber temperature and adjacent strain optical fiber constitute a double lead fiber grating pair.
3. a kind of fibrous composite lightning damage on-line measuring device as claimed in claim 1, it is characterized in that: described double lead array optical fiber temperature grating, double lead array strain fiber grating is double lead structure, namely each grating has two to go between connected, article two, lead-in wire all can as the signalling channel of raster unit, as long as each grating has a bars passage just can be used for input.
4. a kind of fibrous composite lightning damage on-line measuring device as claimed in claim 1, it is characterized in that: described double lead array optical fiber temperature, double lead array strain optical fiber all comprises multiple raster unit being carved with different centre wavelength, and each raster unit is all independently sensor units.
5. a kind of fibrous composite lightning damage on-line measuring device as claimed in claim 1, it is characterized in that: described light source is the laser instrument be built in fiber Bragg grating (FBG) demodulator, laser instrument produces continuous frequency modulation laser, enter double lead array optical fiber temperature grating, double lead array strain fiber grating by lead-in wire, form stable reflected signal.
6. a kind of fibrous composite lightning damage on-line measuring device as claimed in claim 1, it is characterized in that: described processor, comprise Geometric Modeling module, fiber grating signal resolution module, damage of composite materials database and lightning damage inverting graphical interfaces, wherein, described Geometric Modeling module, for carrying out modeling to composite material structural member, in compound substance geometric model, accurately mark the position of raster unit; Described fiber grating signal resolution module, for the wavelength signals that analytical calculation fiber Bragg grating (FBG) demodulator transmits, obtain the temperature of fiber composite structure part, strain and stress, the information stored is contrasted, judge type of impairment and degree of injury in itself and damage of composite materials database; Described lightning damage inverting graphical interfaces, for being finally inversed by compound substance lightning damage distributed in three dimensions situation and exporting.
7. based on a detection method for the device such as described in claim 1-6, it is characterized in that: comprise the following steps:
(1) before composite material solidification is shaping, the spacing as required according to setting in structural member lays double lead array optical fiber temperature grating, double lead array strain fiber grating;
(2) composite material structural member curing molding, fiber-optic grating sensor is embedded in composite material structural member inside, connects the first fiber coupler, the second fiber coupler, fiber Bragg grating (FBG) demodulator and processor;
(3) light source produces laser signal, after laser signal enters the first fiber coupler, the second fiber coupler, double lead array optical fiber temperature grating, double lead array strain fiber grating region is entered respectively by two ends lead-in wire, signal after optical grating reflection is through the first fiber coupler, the second fiber coupler back light gate signal (FBG) demodulator, and light signal is demodulated to digital signal and enters processor process;
(4) set up the 3-D geometric model of composite material structural member by Geometric Modeling module, raster unit is numbered by coordinate relationship marking on the three-dimensional model of composite material structural member; Grating signal parsing module resolves the signal that grating signal (FBG) demodulator sends, and according to the information that double lead array optical fiber temperature grating, double lead array strain fiber grating gather, obtains compound substance strain, temperature and STRESS VARIATION;
(5) compound substance lightning damage database is called, identification of damage type and judge degree of injury, obtain type of impairment and the degree of raster unit numbering place compound substance regional area, type of impairment and degree are passed through stop position data inversion on geometric model, obtains the dynamic solid distribution plan of compound substance lightning damage.
8. detection method as claimed in claim 7, it is characterized in that: in described step (1), concrete grammar is: before composite material solidification is shaping, lay according to certain spacing the fiber grating pair that m is carved with n grating sensor as required in structural member, optical fiber label is 1, 2, 3, m, raster unit label is 1, 2, 3, n, each grating pair there are two fiber gratings, article one, be the optical fiber temperature grating of measuring tempeature, be labeled as T, another is the strain fiber grating of monitor strain, be labeled as S, form two array optical fiber grating sensor.
9. detection method as claimed in claim 7, it is characterized in that: in described step (4), when thunderbolt energy is low, fiber grating is intact, the two ends grating sensor cell signal collected that goes between is identical, any end signal is adopted to carry out lightning damage detection, when the energy that is struck by lightning causes damage of composite materials serious and causes fibercuts, double lead fiber grating becomes two single wire fiber gratings, grating sensor still can carry out detection and transmission of signal, now the signal of two ends lead-in wire transmission all wants check processing, whether damaged by the signal difference determination raster unit district contrasting two lead-in wire transmission, and determine the position in the raster unit district of damaging, quantity.
10. detection method as claimed in claim 7, it is characterized in that: in described step (5), realized measured detection by the drift of measuring raster center wavelength, according to the drift relation of raster center wavelength with stress and temperature, strained and temperature information.
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