CN104807698B - A kind of method of testing of continuous fiber reinforced composites Poisson's ratio - Google Patents
A kind of method of testing of continuous fiber reinforced composites Poisson's ratio Download PDFInfo
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- CN104807698B CN104807698B CN201510214015.2A CN201510214015A CN104807698B CN 104807698 B CN104807698 B CN 104807698B CN 201510214015 A CN201510214015 A CN 201510214015A CN 104807698 B CN104807698 B CN 104807698B
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Abstract
The invention discloses a kind of method of testing of continuous fiber reinforced composites Poisson's ratio, its advantage is：(1) overcome the shortcomings of existing composite Poisson's ratio measuring technology, a kind of FBG method of testings of new composite Poisson's ratio are provided based on optical fiber Bragg raster string technology；(2) solve traditional composite material test piece vacuum bag, the problems such as surface of test piece that autoclave manufacturing technology is caused is of poor quality, in uneven thickness, width is uneven, the depth of parallelism is poor, a kind of continuous fiber reinforced composites standard specimen manufacturing technology is provided based on closed type hot mould pressing technology, emphasis solves the problems, such as the disengaging of the interior composite standard specimen for burying optical fiber Bragg raster string and rigid closed molds, realizes the convenient, accurate of composite Poisson's ratio, Validity Test.
Description
Technical field
The present invention relates to a kind of method of testing of material Poisson's ratio (Poisson ratio), more particularly to a kind of continuous fibre
Tie up the method for testing of reinforced resin based composites Poisson's ratio.
Background technology
Fiber-reinforced resin matrix compound material is by specific strength and specific modulus are high, chemical resistance is good, designability is strong
The features such as, it is used widely in fields such as Aero-Space, automobile, naval vessel, buildings.Wherein, carbon fiber enhancement resin base is combined
Density of material is only about 1.6g/cm3, superior performance, it is contemplated that one of new-energy automobile, main material of aircraft will be turned into.
Carry out structural mechanic of complex material research, the problem for first having to solve is the engineerings such as composite Poisson's ratio, modulus
The accurate test of elastic constant；When carrying out structural mechanic of complex material analysis with assessment using Classical lamination theory, first have to
The problem of solution is exactly the accurate Characterization of Poisson's ratio, because Poisson's ratio is structure design joining with an important materials in analysis
Number, directly affects structural internal force with deformation calculated value.With deepening continuously for investigation of materials and application, Accurate Determining Poisson ratio
Modernism be subjected to the concern of more and more researchers.And Poisson's ratio test has high-precision to equipment, standard specimen in itself
Degree is required.For example, the surface quality requirements of continuous fiber reinforced composites standard specimen are high, surface and edge should nothings
Cut, cavity, depression and burr；Test specimen should be distortionless, and adjacent interplanar should be mutually perpendicular to；Should be without delamination failure inside test specimen
And fibrous fracture.This requires that test material preparation equipment and mold can produce high-quality standard specimen.
It is at present to coordinate secondary meter to adopt using various extensometers using the method for most measure composite Poisson's ratios
Collection data obtain vertical, horizontal strain data, so as to measure Poisson's ratio.But the deadweight of extensometer and chucking power cause soft compared with conference
The additional deformation of matter sample, causes that measuring accuracy is relatively low, measured value is unstable；And, if necessary to use at relatively high temperatures
The method measures composite Poisson's ratio, then require the necessary high temperature resistant of displacement measurement element, and this is current more scabrous technology
Problem.The micro- plunging with measuring accuracy higher starts to rise in recent years, no matter but how small intrusion is can all cause plasticity shape
Become, and material stress strain is considerably complicated during pressure head is depressed.On pasting moire piece or resistance in surface of test piece
The method of testing of piece, foil gauge area, sticking Quality and patch location and direction all increase easily measurement error, and survey
Amount is limited in scope, high cost, it is difficult to apply under the high temperature conditions.Acoustic method can substantially carry out Non-Destructive Testing, but because
The acoustic resistance and internal damping of nonmetallic materials are larger so that the velocity of sound and vibration-testing are all relatively difficult, and the method it cannot be guaranteed that
Test is carried out in elastic limits.Through Optical Interference Spectra typically requires test specimen optically smooth, and this is accomplished by carrying out the table of precision
Mirror polish treatment, increases experimental work amount and difficulty.
Used as a kind of sensing element of function admirable, optical fiber Bragg raster (FBG) is felt by the movement of reflection wavelength
Answer the change of ambient temperature or stress, reflection wavelength movement has good linear relationship with strain；Additionally, it have it is sensitive
Degree height, excellent corrosion resistance, high-low temperature resistant, strong antijamming capability, small volume light weight, on structure almost without influence, test number
According to series of advantages such as reliable and stable and light path deflections, composite can be in advance imbedded in the preparation process of composite
Inside configuration, while carry out accurate measurement to the strain of the vertical and horizontal of inside configuration, with other methods cannot reach it is excellent
Gesture and wide application prospect.
According to the series of advantages of FBG sensor, researcher will be embedded in compound in single vertical and horizontal FBG sensor
Material test specimen length, width, the middle position of thickness direction；First carry out composite curing molding, then by composite material test piece
Being placed on carries out Poisson's ratio determination experiment on universal testing machine, closed using FBG centre wavelengths knots modification and the correspondence of strain
System, determines longitudinal strain and the transverse strain of composite standard specimen, and then obtain the Poisson's ratio of composite material test piece
Test result.But, there are a series of passes in the method using single vertical and horizontal FBG sensor test compound material Poisson's ratio
Key key problem, with wangkai song with Mei Zhiyuan's《Fiberglass/composite》Journal article " composite laminated plate engineering constant
Fiber grating test with analyze " as a example by be described as follows：(1) laterally (90 ° of directions of fiber) fibre-optical bending position and grating region away from
Close to too, it is easily caused grating region deformation and produces chirp signal, and light signal strength decay is serious, so as to cause transverse strain
Measuring accuracy is greatly lowered；(2) wire locations conflict with clamp for universal testing machine position, when optical fiber from grip of testing machine
Place needs significantly to bend when drawing so as to cause light signal strength to be decayed, measuring accuracy reduction；(3) when horizontal raster is arranged not
Plus any safeguard measure, grating is so easily caused by rugged reinforcing fiber failure by shear normal thereto；(4) horizontal,
Longitudinal direction one grating region of each use determines the microstrain of composite standard specimen, so cannot be in the same sample of handling averagely
The uneven situation of the material Poisson's ratio spatial distribution of appearance, larger error is brought to experimental result.
Optical fiber Bragg raster string technology is that write-in multiple, the Bragg with different centre wavelengths are spaced on simple optical fiber
Grating, forms grating string and the need for meeting long range measurements or multimetering, is not required to welding, and position is accurate, it is to avoid with single
The error repeatedly laid during grating test and produced, improves the reliability and stability of measuring system, and can be according to reality
Need the number and spacing of setting grating region.Meanwhile, multiple grating strings can constitute sensing network, realize quasi-distributed measurement.
In addition, using optical fiber Bragg raster string the lead processing can also be made to become easy, convenient.
In order to ensure that FBG sensor effectively, accurately and easily can detect continuous fiber reinforced composites (i.e.
Transverse isotropy composite) Poisson's ratio, researcher is reliably designed composite structure, point
Analysis, assessment, the optical fiber Bragg raster string measuring technology method for developing composite Poisson's ratio are significant.
The content of the invention
The purpose of the present invention is：(1) existing composite Poisson's ratio measuring technology is overcome the shortcomings of, based on optical fiber
Bragg grating strings technology provides a kind of FBG method of testings of new composite Poisson's ratio；(2) traditional composite is solved
Surface of test piece that test specimen vacuum bag, autoclave manufacturing technology are caused is of poor quality, in uneven thickness, width is uneven, the depth of parallelism is poor
The problems such as, provide a kind of continuous fiber reinforced composites test specimen manufacturing technology, emphasis based on closed type hot mould pressing technology
The disengaging of the composite material test piece and rigid closed molds of optical fiber Bragg raster string is buried in solving the problems, such as, realizes that composite is moored
Loose the convenient, accurate of ratio, Validity Test.
The technical scheme that the present invention takes is：
A kind of method of testing of continuous fiber reinforced composites Poisson's ratio, including step is as follows：
1) making of composite standard specimen：Polytetrafluoroethylene (PTFE) adhesive tape and teflon cloth are coated on mould successively
On sidewall frame plate and its lead groove；In N layers of (N >=20) polymer matrix composites prepreg of mold cavity middle berth, and in difference
Laid respectively on prepreg along machine direction and the multiple optical fiber Bragg raster strings perpendicular to machine direction；Then, it is solidified into
Type；
2) demoulding：The resin cleaned out around fiber grating lead, keeps lead straight, pulls teflon cloth
Exposed parts, make the composite product demoulding；
3) test：Under constant temperature, the composite standard specimen of the demoulding is placed in universal testing machine
Poisson's ratio is determined, direct stress σ is individually acted on j directions (0 ° of direction of fiber)j, and without other external force；
4) data processing：The centre wavelength data of the grating region that treatment Real-time Collection is arrived, obtain optical fiber Bragg raster string
The curve that the centre wavelength of each grating region is changed over time, according to raster center wavelength variable quantity and the corresponding relation of microstrain
Longitudinal microstrain and horizontal microstrain of composite standard specimen are obtained, and then is calculated Poisson's ratio ν.
Preferably, step 1) in, it is described to be laid respectively along machine direction and perpendicular to fiber on different prepregs
Concretely comprising the following steps for multiple optical fiber Bragg raster strings in direction is laid in n-th layer (N-10 ＞ n ＞ 5) longitudinal direction (0 ° of direction of fiber)
Multiple optical fiber Bragg raster strings, in the multiple narrow bars of the n-th+i layers (N-14 >=i ＞ 5) horizontal (90 ° of directions of fiber) laying, together
To the optical fiber Bragg raster string that prepreg is protected.
Preferably, step 1) in, the curing molding method is composite hot compression molding method.
Preferably, step 1) in, the grating region of described optical fiber Bragg raster string can not be arranged on 0 ° and 90 ° of directions
On the crosspoint of optical fiber Bragg raster string.
Preferably, step 1) in, 2~6 grid regions are distributed on described optical fiber Bragg raster string.
Preferably, step 1) in, the narrow bar, the thickness of prepreg in the same direction are identical with full wafer prepreg thickness.
Preferably, step 1) in, the paving location of optical fiber Bragg raster string should be noted that in the middle position of test specimen
5 layers of prepreg are at least spaced between 0 ° and 90 ° of direction optical fiber Bragg raster strings.
Preferably, step 1) in, the lead of the optical fiber Bragg raster string parallel to machine direction is near test specimen
The region bends of end are unified to be drawn from side.
Preferably, the tail optical fiber of the optical fiber Bragg raster string is protected using teflon pipe.
Preferably, step 3) in, in the test process, tensile loads speed is no more than 5mm/min.
Step 1 in above-mentioned method of testing) described in the grating region of optical fiber Bragg raster string can not be arranged on 0 ° and 90 ° of sides
On crosspoint to optical fiber Bragg raster string.2~6 grid regions are distributed on the optical fiber Bragg raster string of described detection strain.
Tail optical fiber is protected using teflon pipe, make optical fiber Bragg raster string can in the range of -80 DEG C~280 DEG C long-term use.With
The thickness for making the narrow bar prepreg in protection horizontal raster area is identical with full wafer prepreg thickness, is 0.1~0.2mm, is shaped as
Rectangle, size is 35~40mm of length, 5~10mm of width.The paving location of optical fiber Bragg raster string is in the central position of test specimen
Put, but should be noted that to be at least spaced 5 layers of prepreg between 0 ° and 90 ° of direction optical fiber Bragg raster strings mutual between the two to avoid
Interference.By the lead of longitudinal optical fiber Bragg raster string in the region bends near test piece end, bending radius is 2cm, it is unified from
Draw avoiding the fixture conflict with universal testing machine side so that lead can in order, easily incoming fiber optic grating
(FBG) demodulator, while ensureing light signal strength.The original of a strata tetrafluoroethene adhesive tape is wound on whole framed and its lead groove
Because being that polytetrafluoroethylene (PTFE) fusing point is up to 327 DEG C, therefore will not be melted in composite high temperature cure process；Polytetrafluoroethylene (PTFE) is also
There are many excellent properties, such as chemically stable, solvent resistant, resistance to oxidation, can be in 260 DEG C of long-term uses etc.；Particularly its adhesive property
Difference, not with epoxy resin or the framed adhesion of metal, can be such that the demoulding easily operates.One layer of teflon cloth of cladding can increase compound
Slippage ability between material and metal are framed, is easy to the demoulding.Hot compression molding technique sets as needed, for example：First
From room temperature to 80 DEG C, 30 minutes are incubated, then heat to 130 DEG C, be incubated 60 minutes；The pressure in two stages is
0.5Mpa。
Above-mentioned steps 3) in tensile loads speed be no more than 5mm/min；Because the elongation at break of individual carbon fibers is about
1%, so the composite range of strain in restrained stretching experiment is 0.5%~0.6%, so as to be ensured of in composite bullet
Property limit range in determine Poisson's ratio.
A kind of preparation method of the standard specimen of continuous fiber reinforced composites Poisson's ratio, using following step
Suddenly：
1) making of composite standard specimen：Polytetrafluoroethylene (PTFE) adhesive tape and teflon cloth are coated on mould successively
On sidewall frame plate and its lead groove；In N layers of (N >=20) polymer matrix composites prepreg of mold cavity middle berth, and in difference
Laid respectively on prepreg along machine direction and the multiple optical fiber Bragg raster strings perpendicular to machine direction；Described is parallel
In machine direction optical fiber Bragg raster string lead in the region bends near test piece end, it is unified to be drawn from side；So
Afterwards, curing molding；
2) demoulding：The resin cleaned out around fiber grating lead, keeps lead straight, pulls teflon cloth
Exposed parts, make the composite product demoulding, obtain final product the standard specimen of continuous fiber reinforced composites Poisson's ratio.
The invention has the advantages that：
(1) present invention is by way of the lead of rationally design optical fiber Bragg raster string is drawn from composite material test piece
And position, efficiently solve the improper grating region being easily caused that bends of optical fiber and deform and produce chirped optical signal phenomenon, optical signal
The problems such as strength retrogression is serious, measuring accuracy is reduced；By rationally design optical fiber Bragg raster string in composite material test piece
Embedment position, efficiently solve FBG sensor when composite Poisson's ratio is detected grating region position anti-shear performance difference so as to
Fragile easily broken problem.
(2) multiple optical fiber Bragg raster strings are laid by along machine direction and perpendicular to machine direction, is met to continuous fine
The space Multipoint synchronous measurement for tieing up reinforced resin based composites Poisson's ratio needs, and is not required to welding, and position is accurate, improves test
The reliability and stability of system, and can according to actual needs set the number of the grating region of each optical fiber Bragg raster string
With spacing.
(3) before curing molding, to mould side wall deckle board and its lead groove cladding polytetrafluoroethylene (PTFE) adhesive tape and poly- four
PVF cloth, it is to avoid the directly contact of metal die sidewall frame plate and its lead groove and composite, and metal it is framed,
Although being contacted but non-caked between polytetrafluoroethylene (PTFE) adhesive tape and teflon cloth, it is easy to slide, be conducive to the demoulding, effectively improve
The surface quality and dimensional accuracy of composite standard specimen and the optical fiber Bragg raster string that is imbedded in composite
Survival rate.
(4) with the same direction, narrow bar prepreg to the optical fiber Bragg raster string of transverse direction (90 ° of directions of fiber) up and down embedding at
Reason, can protect grating region, be prevented effectively from the lateral light grid region of fragility by big, the rugged longitudinal fiber failure by shear of rigidity.
The present invention largely improves that traditional optical fiber Bragg raster lead is complicated, it is easy to draw difficult, grating region
Deformation and the problem of easy damaged destruction, make the FBG detecting steps of composite Poisson's ratio easy and efficient；Solve traditional answering
Condensation material standard specimen surface quality is low, poor dimensional precision the problems such as；Protect well as the fiber Bragg of sensing element
The grating region of grating string, makes the data obtained more fully, accurately, reliably.
Brief description of the drawings
Fig. 1 for the embodiment of the present invention structure drawing of device (in order to show composite standard specimen and fiber-optic wire,
Upper die plate is not drawn in the structure drawing of device).
Fig. 2 (a) is that the mould top view for being provided with lead groove (for ease of observation lead groove, mould is deleted in the figure
Plate)；
Fig. 2 (b) is the A-A direction views of the mould for being provided with lead groove；
Fig. 2 (c) is the mould for being covered with a strata tetrafluoroethene adhesive tape and one layer of teflon cloth；
Fig. 2 (d) is the internal mould for being equipped with partial prepreg；
Fig. 2 (e) is laying method of longitudinal optical fiber Bragg raster string inside test specimen；
Fig. 2 (f) is laying method of the horizontal optical fiber Bragg raster string inside test specimen；
Fig. 2 (g) is paving of the horizontal optical fiber Bragg raster string for having used narrow bar, prepreg in the same direction to protect inside test specimen
Equipment, method.
Wherein, 1 is prepreg, and 2 for the optical fiber Bragg raster string of longitudinal direction (0 ° of direction of fiber) laying, (tail optical fiber uses Teflon
Imperial pipe is protected), 3 for laterally (90 ° of directions of fiber) laying optical fiber Bragg raster string (tail optical fiber is carried out using teflon pipe
Protection), 4 is the lead groove of mould side wall deckle board, and 5 is mould side wall deckle board, and 6 is a strata tetrafluoroethene adhesive tape and a strata
Tetrafluoroethene cloth, 7 is lower template, and 8 is narrow bar, prepreg in the same direction as horizontal (90 ° of directions of the fiber) grating region of protection.
Specific embodiment
The present invention will be further elaborated below in conjunction with the accompanying drawings.It should be noted that the description below is merely to solution
The present invention is released, its content is not defined.
Embodiment 1：
A kind of optical fiber Bragg raster string method of testing of continuous fiber reinforced composites Poisson's ratio.
(1) making of composite standard specimen：A strata is equably wound on whole framed 5 and its lead groove 4
Tetrafluoroethene adhesive tape, then coats one layer of teflon cloth.In N layers of (N >=20) polymer matrix composites of mold cavity middle berth
Optical fiber Bragg raster string is laid respectively on prepreg 1, and two prepregs wherein, i.e., in n-th layer (N-10>N ＞ 5)
An optical fiber Bragg raster string 2 is laid in longitudinal direction (0 ° of direction of fiber), in the n-th+i layers (N-14 >=i ＞ 5) horizontal (90 ° of sides of fiber
To) on laying one with narrow bar, prepreg in the same direction 8 protect optical fiber Bragg raster string 3, these narrow bars, prepreg in the same direction
8 machine direction is identical with the direction of optical fiber Bragg raster string 3, and thickness is identical with full wafer prepreg thickness, be 0.1~
0.2mm, is shaped as rectangle；Be distributed 6 grating regions on longitudinal optical fiber Bragg raster string 2, grating region and test specimen edge should at least between
Every 40mm；2 grating regions are distributed on horizontal optical fiber Bragg raster string 3, grating region should at least be spaced 5mm with test specimen edge；Tail optical fiber
Protected using teflon pipe, make optical fiber Bragg raster string can in the range of -80 DEG C~280 DEG C long-term use.Solidification side
Method is composite hot compression molding method.
Specific implementation step：
A) a strata tetrafluoroethene adhesive tape is equably wound on whole framed 5 and its lead groove 4, then with a strata four
PVF cloth is coated completely, them is tightly fitted with mould side wall deckle board.
B) prepreg is pressed using prepreg guillotine and is successively cut parallel to machine direction (0 ° of direction of fiber), cut out face
Inside dimension is the narrow bar preimpregnation as protection grating region of 40mm*10mm for the prepreg and face inside dimension of 260mm*40mm
Material.
C) the face inside dimension for obtaining will be cut for the prepreg of 260mm*40mm is successively routed to by applying in advance as requested
In the lower template 7 of good releasing agent and ready framed 5 die cavity for surrounding, ply sequence is [0 °]22.In process of deployment,
8th layer of longitudinal direction (0 ° of direction of fiber) lays one group of optical fiber Bragg raster string 2, as axial strain sensor；In the 15th layer of transverse direction
(90 ° of directions of fiber) lay one group of optical fiber Bragg raster string 3 protected with narrow bar, prepreg in the same direction 8, as transverse strain
Sensor.The lead of optical fiber Bragg raster string 2 of axial strain sensor be will act as in the region bends near test piece end,
Bending radius is 2cm, unified to draw to avoid the fixture conflict of lead and universal testing machine from side so that lead can
In order, easily incoming fiber optic grating demodulation instrument, it is ensured that light signal strength, while avoiding optical signal from producing chirp phenomenon.
D) upper die plate for coating releasing agent in advance is covered, Guan Bi mould is inserted in vulcanizer；Heating pressurization, makes prepreg
It is hot-forming in full rigidity closed molds, realize the solidification of composite.The heat pressing process of use is first continuously to be risen from room temperature
Temperature is incubated 30 minutes to 80 DEG C, and then continuous warming, to 130 DEG C, is incubated 60 minutes again；The pressure in two stages is
0.5Mpa, is finally cooled to room temperature, obtains the polymer matrix composites of curing molding.
(2) demoulding：Vulcanizer is opened, the resin cleaned out around optical fiber Bragg raster string lead is prevented because of resin
Adhesion and destroy fiber grating；Keep lead straight, it is to avoid its bending, influence signal acquisition.Pull the outer of teflon cloth
Dew part, makes the composite product demoulding.
(3) test：The composite standard specimen of the demoulding that succeeded is placed in universal testing machine and determines Poisson
Than, tensile stress sigma is individually acted in the vertical, and without other external force.Experiment loading velocity is 2mm/min；Due to individual carbon fibers
Elongation at break be about 1%, so restrained stretching experiment in standard specimen draw ratio be 0.5%~0.6%, so as to ensure
It is that Poisson's ratio is determined in elastic limits.
Specific implementation step：
A) environment temperature is controlled, it is ensured that experiment is carried out under constant temperature.
B) standard specimen is put into fixture, must makes the long axis of standard specimen with the axis of testing machine into always
Line, prestressing force, somewhat tight standard specimen are loaded to standard specimen；Prestrain ε≤0.05%.
C) will be bent in standard specimen in advance, the unified FBG lead incoming fiber optic grating demodulation instrument drawn from side.
D) standard specimen is stretched with the loading velocity of 2mm/min, until strain reaches 0.5%~0.6%；Dynamic is real simultaneously
When collection grating region centre wavelength data.
(4) data processing：The centre wavelength data of the grating region that treatment Real-time Collection is arrived, obtain optical fiber Bragg raster string
Each grating region the curve that changes over time of centre wavelength；With longitudinal reflection wavelength as abscissa, horizontal reflection wavelength is
Ordinate, obtains a relation curve, and this slope of a curve is exactly the Poisson's ratio ν of composite standard specimen.
Embodiment 2：
A kind of optical fiber Bragg raster string method of testing of continuous fiber reinforced composites Poisson's ratio.
(1) making of composite standard specimen：A strata is equably wound on whole framed 5 and its lead groove 4
Tetrafluoroethene adhesive tape, then coats one layer of teflon cloth.In N layers of (N >=20) polymer matrix composites of mold cavity middle berth
Optical fiber Bragg raster string is laid respectively on prepreg 1, and two prepregs wherein, i.e., in n-th layer (N-10>N ＞ 5)
An optical fiber Bragg raster string 2 is laid in longitudinal direction (0 ° of direction of fiber), in the n-th+i layers (N-14 >=i ＞ 5) horizontal (90 ° of sides of fiber
To) one optical fiber Bragg raster string 3 protected with narrow bar, prepreg in the same direction 8 of laying, these narrow bars, prepreg in the same direction 8
Machine direction it is identical with the direction of optical fiber Bragg raster string 3, thickness is identical with full wafer prepreg thickness, is 0.1~0.2mm,
It is shaped as rectangle；4 grating regions are distributed on longitudinal optical fiber Bragg raster string 2, grating region should at least be spaced with test specimen edge
40mm；2 grating regions are distributed on horizontal optical fiber Bragg raster string 3, grating region should at least be spaced 5mm with test specimen edge；Tail optical fiber makes
Protected with teflon pipe, make optical fiber Bragg raster string can in the range of -80 DEG C~280 DEG C long-term use.Curing
It is composite hot compression molding method.
Specific implementation step：
A) a strata tetrafluoroethene adhesive tape is equably wound on whole mould side wall deckle board 5 and its lead groove 4, then is used
Individual layer teflon cloth is coated completely, them is tightly fitted with mould side wall deckle board 5.
B) prepreg is pressed using prepreg guillotine and is successively cut parallel to machine direction (0 ° of direction of fiber), cut out face
Prepreg, narrow bar prepreg as protection grating region that face inside dimension be 40mm*10mm of the inside dimension for 260mm*40mm.
C) the face inside dimension for obtaining will be cut for the prepreg of 260mm*40mm is successively routed to by applying in advance as requested
In the die cavity that the lower template 7 of good releasing agent and ready mould side wall deckle board 5 are surrounded, ply sequence is [0 °]20.Laying
Cheng Zhong, lays one group of optical fiber Bragg raster string 2, as axial strain sensor in the 6th layer of longitudinal direction (0 ° of direction of fiber)；
12 layers of transverse direction (90 ° of directions of fiber) lay one group of optical fiber Bragg raster string 3 protected with narrow bar, prepreg in the same direction 8.Will be vertical
Bent to the lead of optical fiber Bragg raster string 2, bending radius is 2cm, it is unified to draw to avoid lead and universal material from side
The fixture conflict of testing machine so that lead can in order, easily incoming fiber optic grating demodulation instrument, it is ensured that light signal strength, together
When avoid optical signal produce chirp phenomenon.
D) upper die plate for coating releasing agent in advance is covered, Guan Bi mould is inserted in vulcanizer；Heating pressurization, makes prepreg
It is hot-forming in full rigidity closed molds, realize the solidification of composite.The heat pressing process of use is first continuously to be risen from room temperature
Temperature is incubated 30 minutes to 80 DEG C, and then continuous warming, to 130 DEG C, is incubated 60 minutes again；The pressure in two stages is
0.5Mpa, is finally cooled to room temperature, obtains the polymer matrix composites of curing molding.
(2) demoulding：Vulcanizer is opened, the resin cleaned out around optical fiber Bragg raster string lead prevents its destruction light
Fine grating；Keep lead straight, it is to avoid its bending, influence signal acquisition.The exposed parts of teflon cloth are pulled, makes to be combined
The material demoulding.
(3) test：The composite standard specimen of the demoulding that succeeded is placed in universal testing machine and determines Poisson
Than, tensile stress sigma is individually acted in the vertical, and without other external force.Experiment loading velocity is 1mm/min；Due to individual carbon fibers
Elongation at break be about 1%, so restrained stretching experiment in standard specimen draw ratio be 0.5%~0.6%, so as to ensure
It is that Poisson's ratio is determined in elastic limits.
Specific implementation step：
A) environment temperature is controlled, it is ensured that experiment is carried out under constant temperature.
B) standard specimen is put into fixture, must makes the long axis of standard specimen with the axis of testing machine into always
Line, prestressing force, somewhat tight standard specimen are loaded to standard specimen；Prestrain ε≤0.05%.
C) by lead incoming fiber optic grating demodulation instrument.
D) standard specimen is stretched with the loading velocity of 1mm/min, until strain reaches 0.5%~0.6%；Dynamic is real simultaneously
When collection grating region centre wavelength data.
(4) data processing：The centre wavelength data of the grating region that treatment Real-time Collection is arrived, obtain optical fiber Bragg raster string
Each grating region the curve that changes over time of centre wavelength, closed according to raster center wavelength variable quantity and the correspondence of microstrain
System obtains longitudinal microstrain and horizontal microstrain of composite standard specimen, laterally micro- to answer with longitudinal microstrain as abscissa
It is changed into ordinate, obtains a relation curve, this slope of a curve is exactly the Poisson's ratio ν of composite standard specimen.
Although above-mentioned be described with reference to accompanying drawing to specific embodiment of the invention, not to present invention protection model
The limitation enclosed, one of ordinary skill in the art should be understood that on the basis of technical scheme those skilled in the art are not
Need the various modifications made by paying creative work or deformation still within protection scope of the present invention.
Claims (9)
1. a kind of method of testing of continuous fiber reinforced composites Poisson's ratio, it is characterised in that as follows including step：
1) making of composite standard specimen：Polytetrafluoroethylene (PTFE) adhesive tape and teflon cloth are coated on mould side wall successively
On deckle board and its lead groove；In N layers of N >=20 polymer matrix composites prepreg of mold cavity middle berth, and in different prepregs
Laid respectively on layer along machine direction and the multiple optical fiber Bragg raster strings perpendicular to machine direction；Then, curing molding；
2) demoulding：The resin cleaned out around fiber grating lead, keeps lead straight, pulls exposing for teflon cloth
Part, makes the composite product demoulding；
3) test：Under constant temperature, the composite standard specimen of the demoulding is placed in universal testing machine and is determined
Poisson's ratio, individually in j directions, i.e., on 0 ° of direction of fiber, acts on direct stress σj, and without other external force；
4) data processing：The centre wavelength data of the grating region that treatment Real-time Collection is arrived, obtain each of optical fiber Bragg raster string
The curve that the centre wavelength of grating region is changed over time, the corresponding relation according to raster center wavelength variable quantity and microstrain is obtained
Longitudinal microstrain of composite standard specimen and horizontal microstrain, and then it is calculated Poisson's ratio；
Step 1) in, it is described to be laid respectively on different prepregs along machine direction and the multiple optical fiber perpendicular to machine direction
Concretely comprising the following steps in the longitudinal directions of n-th layer N-10 ＞ n ＞ 5, i.e. 0 ° of direction of fiber for Bragg grating strings, lays multiple fiber Bragg light
Grid string, in the n-th+i layers of transverse direction of N-14 >=i ＞ 5, i.e. 90 ° of directions of fiber, lays what multiple narrow bars, prepreg in the same direction were protected
Optical fiber Bragg raster string.
2. the method for claim 1, it is characterised in that step 1) in, the curing molding method is composite heat
Compression-moulding methods.
3. the method for claim 1, it is characterised in that step 1) in, the grating region of described optical fiber Bragg raster string
Can not be arranged on the 0 ° and 90 ° crosspoint of direction optical fiber Bragg raster string.
4. the method for claim 1, it is characterised in that step 1) in, it is distributed 2 on described optical fiber Bragg raster string
~6 grid regions.
5. the method for claim 1, it is characterised in that step 1) in, the narrow bar, the thickness of prepreg in the same direction and
Full wafer prepreg thickness is identical.
6. the method for claim 1, it is characterised in that step 1) in, the paving location of optical fiber Bragg raster string is in mark
The middle position of quasi- test specimen, wherein, at least it is spaced 5 layers of prepreg between 0 ° and 90 ° of direction optical fiber Bragg raster strings.
7. the method for claim 1, it is characterised in that step 1) in, the fiber Bragg parallel to machine direction
The lead of grating string is unified to be drawn from side in the region bends near standard specimen end.
8. the method for claim 1, it is characterised in that the tail optical fiber of the optical fiber Bragg raster string uses teflon pipe
Protected.
9. a kind of preparation method of the standard specimen of continuous fiber reinforced composites Poisson's ratio, it is characterised in that adopt
Use following steps：
1) making of composite standard specimen：Polytetrafluoroethylene (PTFE) adhesive tape and teflon cloth are coated on mould side wall successively
On deckle board and its lead groove；In N layers of N >=20 polymer matrix composites prepreg of mold cavity middle berth, and in different prepregs
Laid respectively on layer along machine direction and the multiple optical fiber Bragg raster strings perpendicular to machine direction；It is described parallel to fiber
The lead of the optical fiber Bragg raster string in direction is unified to be drawn from side in the region bends near test piece end；Then, solidify
Shaping；
2) demoulding：The resin cleaned out around fiber grating lead, keeps lead straight, pulls exposing for teflon cloth
Part, makes the composite product demoulding, obtains final product the standard specimen of continuous fiber reinforced composites Poisson's ratio.
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