CN104807698A - Test method for poisson ratio of continuous fiber enhanced resin-based composite material - Google Patents
Test method for poisson ratio of continuous fiber enhanced resin-based composite material Download PDFInfo
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- CN104807698A CN104807698A CN201510214015.2A CN201510214015A CN104807698A CN 104807698 A CN104807698 A CN 104807698A CN 201510214015 A CN201510214015 A CN 201510214015A CN 104807698 A CN104807698 A CN 104807698A
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Abstract
The invention discloses a test method for a poisson ratio of a continuous fiber enhanced resin-based composite material. The test method has the advantages that (1) the shortcomings of the existing composite material poisson ratio test technology are overcome, and a novel FBG test method for the poisson ratio of the composite material is provided based on a fiber Bragg grating string technology; (2) the problem that a test piece is low in surface quality, non-uniform in thickness, non-uniform in width, low in parallelism and the like caused by the conventional composite material test piece vacuum bag and thermal pressing tank manufacturing technology is solved, a manufacturing technology for a continuous fiber enhanced resin-based composite material standard test piece is provided based on a closed type thermal die pressing technology, and the problem of separation of the composite material standard test piece with the built-in fiber Bragg grating string from a rigid closed type die is focused to be solved, and convenient, precise and effective test on the poisson ratio of the composite material is realized.
Description
Technical field
The present invention relates to the method for testing of a kind of material Poisson ratio (Poisson ratio), particularly a kind of method of testing of continuous fiber reinforced composites Poisson ratio.
Background technology
Fiber-reinforced resin matrix compound material relies on specific strength and the feature such as specific modulus is high, chemical resistance is good, designability is strong, is used widely in fields such as Aero-Space, automobile, naval vessel, buildings.Wherein, carbon fiber enhancement resin base composite material density is only about 1.6g/cm
3, superior performance, estimate one of the main material by becoming new-energy automobile, aircraft.
Carry out structural mechanic of complex material research, the problem that first will solve is the accurate test of the Engineering Elastic Constants such as compound substance Poisson ratio, modulus; When adopting Classical lamination theory to carry out structural mechanic of complex material analysis with assessment, the problem that first will solve is exactly the accurate Characterization of Poisson ratio, because Poisson ratio is structural design and an important materials parameter in analysis, directly affect structural internal force and distortion calculated value.Along with deepening continuously of investigation of materials and application, the modernism of Accurate Determining Poisson ratio has been subjected to the concern of more and more researcher.And Poisson ratio test itself has high-precision requirement to equipment, standard specimen.Such as, the surface quality requirements of continuous fiber reinforced composites standard specimen is high, and no marking, cavity, depression and burr are answered in surface and edge; Test specimen should be distortionless, and adjacent interplanar should be mutually vertical; Test specimen inside should without delamination failure and fibre breakage.This just requires that test material preparation equipment and mold can produce high-quality standard specimen.
The method of the mensuration compound substance Poisson ratio that current employing is maximum uses various extensometer to coordinate secondary instrument image data to obtain vertical, horizontal strain data, thus record Poisson ratio.But the deadweight of extensometer and holding force cause the additional deformation of soft sample compared with conference, cause that measuring accuracy is lower, to measure numerical value unstable; And if need to measure compound substance Poisson ratio by the method at relatively high temperatures, then require that displacement measurement element must be high temperature resistant, this is current more scabrous technical barrier.Micro-plunging in recent years with higher measuring accuracy starts to rise, no matter but how little intrusion is all can cause plastic deformation, and quite complicated at the process in which materials ess-strain of pressure head pressure.About the method for testing of pasting moire sheet or resistor disc in surface of test piece, foil gauge area, sticking Quality and patch location and direction all easily make measuring error increase, and measurement range is limited, and cost is high, are difficult to apply under the high temperature conditions.Acoustic method can realize Non-Destructive Testing substantially, but because the acoustic resistance of nonmetallic materials and internal damping are comparatively large, makes the velocity of sound and vibration-testing all more difficult, and the method can not ensure that test is carried out in elastic limits.Through Optical Interference Spectra General Requirements test specimen optically smooth, this carries out accurate surface finish process with regard to needing, and increases experimental work amount and difficulty.
As a kind of sensing element of function admirable, optical fiber Bragg raster (FBG) responds to the change of ambient temperature or stress by the movement of reflection wavelength, and reflection wavelength moves has good linear relationship with straining; In addition, it have highly sensitive, excellent corrosion resistance, high-low temperature resistant, antijamming capability are strong, the little quality of volume is light, on structure almost without affecting, the series of advantages such as the reliable and stable and light path deflection of test data, can in the preparation process of compound substance, imbed composite structure inside in advance, the strain of the vertical and horizontal of inside configuration is accurately measured simultaneously, there is advantage and wide application prospect that other method cannot reach.
According to the series of advantages of FBG sensor, researchist will be embedded in the middle position of composite material test piece length, width, thickness direction in single vertical and horizontal FBG sensor; First carry out composite material solidification shaping, composite material test piece is placed on universal testing machine again and carries out Poisson ratio determination experiment, utilize the corresponding relation of FBG centre wavelength knots modification and strain, determine longitudinal strain and the transverse strain of compound substance standard specimen, and then obtain the test result of Poisson ratio of composite material test piece.But, the method of single vertical and horizontal FBG sensor test compound substance Poisson ratio is adopted to there is a series of key core problem, be described as follows for " About Frp/cm " journal article " the fiber grating testing and analyzing of composite laminated plate engineering constant " of wangkai song and Mei Zhiyuan: (1) horizontal (fiber 90 ° of directions) fibre-optical bending position and grating region are apart from too near, grating region is easily caused to be out of shape and to produce chirp signal, and light signal strength decay is serious, thus transverse strain measuring accuracy is caused significantly to reduce; (2) wire locations conflicts with clamp for universal testing machine position, needs significantly to bend thus cause light signal strength decay, measuring accuracy reduction when optical fiber is drawn from grip of testing machine; (3) do not add any safeguard measure when horizontal raster is arranged, the easy like this grating that causes is by rugged fortifying fibre shear failure vertical with it; (4) horizontal, longitudinally each use grating region measure the microstrain of compound substance standard specimen, the situation that the material Poisson ratio space distribution that cannot occur in the same sample of handling averagely is like this uneven, bring comparatively big error to experimental result.
Optical fiber Bragg raster string technology is that interval writes multiple, to have different centre wavelength Bragg gratings on simple optical fiber, form grating string, meet the needs of long range measurements or multimetering, do not need welding, position is accurate, avoiding the error produced with repeatedly laying during single grating test, improve reliability and the stability of measuring system, and number and the spacing of grating region can be set according to actual needs.Meanwhile, multiple grating string can form sensing network, realizes quasi-distributed measurement.In addition, adopt optical fiber Bragg raster string that lead processing can also be made to become easily, facilitate.
In order to ensure that FBG sensor can detect the Poisson ratio of continuous fiber reinforced composites (i.e. transverse isotropy compound substance) effectively, accurately and easily, enable researchist carry out reliable design and analysis, assessment to composite structure, the optical fiber Bragg raster string measuring technology method of exploitation compound substance Poisson ratio is significant.
Summary of the invention
The object of the invention is: (1) overcomes the deficiency of existing compound substance Poisson ratio measuring technology, a kind of FBG method of testing of new compound substance Poisson ratio is provided based on optical fiber Bragg raster string technology; (2) solve traditional composite material test piece vacuum bag, the problem such as surface of test piece that autoclave manufacturing technology causes is of poor quality, in uneven thickness, width is uneven, the depth of parallelism is poor, a kind of continuous fiber reinforced composites test specimen manufacturing technology is provided based on closed type hot mould pressing technology, emphasis buries the composite material test piece of optical fiber Bragg raster string and the disengaging problem of rigidity closed molds in solving, and realizes convenient, accurate, the Validity Test of compound substance Poisson ratio.
The technical scheme that the present invention takes is:
A method of testing for continuous fiber reinforced composites Poisson ratio, comprises step as follows:
1) making of compound substance standard specimen: teflon adhesive tape and teflon cloth are coated on successively on mould side wall deckle board and lead-in wire groove thereof; At mold cavity middle berth N layer (N >=20) polymer matrix composites prepreg, and lay along machine direction and the multiple optical fiber Bragg raster strings perpendicular to machine direction on different prepreg respectively; Then, curing molding;
2) demoulding: clean out fiber grating lead-in wire resin around, keep wire straight, pull the exposed parts of teflon cloth, make the composite product demoulding;
3) test: under constant temperature, the compound substance standard specimen of the demoulding is placed in universal testing machine and measures Poisson ratio, separately at j direction (fiber 0 ° of direction) upper effect normal stress σ
j, and without other external force;
4) data processing: the centre wavelength data of the grating region that process Real-time Collection arrives, obtain the time dependent curve of centre wavelength of each grating region of optical fiber Bragg raster string, corresponding relation according to raster center wavelength variable quantity and microstrain obtains longitudinal microstrain of compound substance standard specimen and horizontal microstrain, and then calculates Poisson ratio ν.
Preferably; step 1) in; described lay respectively on different prepreg along machine direction and perpendicular to multiple optical fiber Bragg raster strings of machine direction concrete steps for n-th layer (N-10 > n > 5) longitudinally (fiber 0 ° of direction) lay multiple optical fiber Bragg raster string, the n-th+i layer (N-14 >=i > 5) laterally (fiber 90 ° of directions) lay the optical fiber Bragg raster string of multiple fillet shape, prepreg protection in the same way.
Preferably, step 1) in, described curing molding method is compound substance hot compression molding method.
Preferably, step 1) in, the grating region of described optical fiber Bragg raster string can not be arranged on the point of crossing of 0 ° and 90 ° direction optical fiber Bragg raster string.
Preferably, step 1) in, described optical fiber Bragg raster string distributes 2 ~ 6 grid regions.
Preferably, step 1) in, the thickness of described fillet shape, in the same way prepreg is identical with full wafer prepreg thickness.
Preferably, step 1) in, the paving location of optical fiber Bragg raster string at the middle position of test specimen, but should to note between 0 ° and 90 ° of direction optical fiber Bragg raster strings at least 5 layers, interval prepreg.
Preferably, step 1) in, described in be parallel to the lead-in wire of the optical fiber Bragg raster string of machine direction at the region bends near test piece end, unifiedly to draw from side.
Preferably, the tail optical fiber of described optical fiber Bragg raster string uses teflon pipe to protect.
Preferably, step 3) in, in described 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 the point of crossing of 0 ° and 90 ° direction optical fiber Bragg raster string.Distribution 2 ~ 6 grid regions on the optical fiber Bragg raster string of described detection strain.Tail optical fiber use teflon pipe protect, make optical fiber Bragg raster string can in the scope of-80 DEG C ~ 280 DEG C Long-Time Service.The thickness being used as the fillet shape prepreg in protection lateral light grid region is identical with full wafer prepreg thickness, and be 0.1 ~ 0.2mm, shape is rectangle, is of a size of length 35 ~ 40mm, width 5 ~ 10mm.The paving location of optical fiber Bragg raster string at the middle position of test specimen, but should to notice between 0 ° and 90 ° of direction optical fiber Bragg raster strings that at least 5 layers, interval prepreg is to avoid mutually interfering between the two.By the lead-in wire of longitudinal optical fiber Bragg raster string at the region bends near test piece end, bending radius is 2cm, unified to draw from side to avoid the fixture conflict with universal testing machine, make lead-in wire can in order, incoming fiber optic grating demodulation instrument easily, ensure light signal strength simultaneously.The reason that whole framed and lead-in wire groove is wound around one deck teflon adhesive tape be teflon fusing point up to 327 DEG C, therefore can not melting in compound substance high temperature cure process; Teflon also has many excellent properties, as chemically stable, solvent resistant, resistance to oxidation, and can at 260 DEG C of Long-Time Service etc.; Particularly its adhesive property is poor, not with epoxy resin or the framed adhesion of metal, the demoulding can be made easily to operate.Coated one deck teflon cloth can increase compound substance and metal framed between slippage ability, be convenient to the demoulding.Hot compression molding technique sets as required, such as: first from room temperature to 80 DEG C, is incubated 30 minutes, is then warming up 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 breaking elongation of individual carbon fibers is about 1%, so the compound substance range of strain in restrained stretching test is 0.5% ~ 0.6%, thus ensure it is measure Poisson ratio in compound substance elastic limits.
A preparation method for the standard specimen of continuous fiber reinforced composites Poisson ratio, adopts following steps:
1) making of compound substance standard specimen: teflon adhesive tape and teflon cloth are coated on successively on mould side wall deckle board and lead-in wire groove thereof; At mold cavity middle berth N layer (N >=20) polymer matrix composites prepreg, and lay along machine direction and the multiple optical fiber Bragg raster strings perpendicular to machine direction on different prepreg respectively; The described lead-in wire being parallel to the optical fiber Bragg raster string of machine direction is at the region bends near test piece end, and unification is drawn from side; Then, curing molding;
2) demoulding: clean out fiber grating lead-in wire resin around, keep wire straight, pull the exposed parts of teflon cloth, make the composite product demoulding, obtain the standard specimen of continuous fiber reinforced composites Poisson ratio.
The effect that the present invention is useful is:
(1) the present invention's mode of being drawn from composite material test piece by the lead-in wire of appropriate design optical fiber Bragg raster string and position, is efficiently solved the improper bending grating region distortion that easily causes of optical fiber and produces the problems such as chirped optical signal phenomenon, light signal strength decay are serious, measuring accuracy reduction; In composite material test piece, imbedding position by appropriate design optical fiber Bragg raster string, efficiently solving FBG sensor position, grating region anti-shear performance difference thus fragile easily broken problem when detecting compound substance Poisson ratio.
(2) by laying multiple optical fiber Bragg raster string along machine direction with perpendicular to machine direction, meet and needs are measured to the space Multipoint synchronous of continuous fiber reinforced composites Poisson ratio, do not need welding, position is accurate, improve reliability and the stability of test macro, and number and the spacing of the grating region of each optical fiber Bragg raster string can be set according to actual needs.
(3) before curing molding, to mould side wall deckle board and the go between coated teflon adhesive tape of groove and teflon cloth, avoid metal die sidewall deckle board and lead-in wire groove contact with the direct of compound substance, although and metal is framed, between teflon adhesive tape and teflon cloth contact but non-caked, be easy to slippage, be conducive to the demoulding, effectively improve the surface quality of compound substance standard specimen and dimensional accuracy and be imbedded at the survival rate of the optical fiber Bragg raster string in compound substance.
(4) with in the same way, fillet shape prepreg is to the upper and lower embedding treatment of optical fiber Bragg raster string in transverse direction (fiber 90 ° of directions); can grating region be protected, effectively avoid fragile large by rigidity, the rugged longitudinal fiber shear failure in lateral light grid region.
The present invention improve to a great extent traditional optical fiber Bragg raster lead-in wire complicated, draw the problem that the yielding and easy damaged in difficulty, grating region destroys, make the FBG detecting step of compound substance Poisson ratio easy and efficient; Solve the problems such as traditional compound substance standard specimen surface quality is low, poor dimensional precision; Protect the grating region of the optical fiber Bragg raster string as sensitive element well, make the data obtained more comprehensive, accurate, reliable.
Accompanying drawing explanation
Fig. 1 is the structure drawing of device (in order to show compound substance standard specimen and fiber-optic wire, not drawing cope match-plate pattern in this structure drawing of device) of the embodiment of the present invention.
Fig. 2 (a) is for having the mould vertical view (for ease of observing lead-in wire groove, deleting cope match-plate pattern in this figure) of lead-in wire groove;
Fig. 2 (b) is for having the A-A direction view of the mould of lead-in wire groove;
Fig. 2 (c) is for being covered with the mould of one deck teflon adhesive tape and one deck teflon cloth;
Fig. 2 (d) is the inner mould being equipped with partial prepreg;
Fig. 2 (e) is the laying method of longitudinal optical fiber Bragg raster string in test specimen inside;
Fig. 2 (f) is the laying method of lateral light fiber Bragg grating string in test specimen inside;
Fig. 2 (g) is with the laying method of lateral light fiber Bragg grating string in test specimen inside of fillet shape, in the same way prepreg protection.
Wherein, 1 is prepreg; the 2 optical fiber Bragg raster strings laid for longitudinal (fiber 0 ° of direction) (tail optical fiber uses teflon pipe to protect); the 3 optical fiber Bragg raster strings laid for horizontal (fiber 90 ° of directions) (tail optical fiber uses teflon pipe to protect); 4 is the lead-in wire groove of mould side wall deckle board; 5 is mould side wall deckle board; 6 is one deck teflon adhesive tape and one deck teflon cloth; 7 is lower bolster, and 8 is be used as protection laterally (fiber 90 ° of directions) fillet shape of grating region, in the same way prepreg.
Concrete embodiment
Below in conjunction with accompanying drawing, the present invention will be further elaborated.Should be noted that following explanation is only to explain the present invention, its content not being limited.
Embodiment 1:
A kind of optical fiber Bragg raster string method of testing of continuous fiber reinforced composites Poisson ratio.
(1) making of compound substance standard specimen: be wound around one deck teflon adhesive tape equably, then coated one deck teflon cloth on whole framed 5 and lead-in wire groove 4.At mold cavity middle berth N layer (N >=20) polymer matrix composites prepreg 1, and two prepreg wherein lay optical fiber Bragg raster string respectively, namely an optical fiber Bragg raster string 2 is laid in n-th layer (N-10>n > 5) longitudinal (fiber 0 ° of direction), fillet shape is used in the upper laying one of the n-th+i layer (N-14 >=i > 5) horizontal (fiber 90 ° of directions), the optical fiber Bragg raster string 3 of prepreg 8 protection in the same way, these fillet shapes, the machine direction of prepreg 8 is identical with the direction of optical fiber Bragg raster string 3 in the same way, thickness is identical with full wafer prepreg thickness, be 0.1 ~ 0.2mm, shape is rectangle, distribution 6 grating regions on longitudinal optical fiber Bragg raster string 2, grating region and test specimen edge should at least interval 40mm, lateral light fiber Bragg grating string 3 distributes 2 grating regions, and grating region and test specimen edge should at least interval 5mm, tail optical fiber use teflon pipe protect, make optical fiber Bragg raster string can in the scope of-80 DEG C ~ 280 DEG C Long-Time Service.Curing is compound substance hot compression molding method.
Concrete implementation step:
A) on whole framed 5 and lead-in wire groove 4, be wound around one deck teflon adhesive tape equably, then use one deck teflon cloth completely coated, they and mould side wall deckle board are tightly fitted.
B) prepreg guillotine is utilized successively to be cut by being parallel to machine direction (fiber 0 ° of direction) by prepreg, the fillet shape prepreg being used as protection grating region of the face inside dimension of cutting out to be the prepreg of 260mm*40mm and face inside dimension be 40mm*10mm.
C) be that the prepreg of 260mm*40mm is successively routed to as requested by the lower bolster 7 coating release agent in advance and ready framed 5 die cavitys surrounded by cutting the face inside dimension obtained, ply sequence is [0 °]
22.In process of deployment, lay one group of optical fiber Bragg raster string 2, as axial strain sensor in the 8th layer of longitudinal direction (fiber 0 ° of direction); One group of optical fiber Bragg raster string 3 with the protection of fillet shape, in the same way prepreg 8 is laid, as transverse strain sensor in the 15th layer of transverse direction (fiber 90 ° of directions).To the lead-in wire of the optical fiber Bragg raster string 2 of axial strain sensor be used as at the region bends near test piece end, bending radius is 2cm, unified fixture conflict of drawing from side to avoid lead-in wire and universal testing machine, make lead-in wire can in order, incoming fiber optic grating demodulation instrument easily, ensure light signal strength, avoid light signal to produce chirp phenomenon simultaneously.
D) cover the cope match-plate pattern coating release agent in advance, close die, insert in vulcanizer; Heating pressurization, makes prepreg hot-forming in full rigidity closed molds, realizes the solidification of compound substance.The heat pressing process adopted is first from room temperature continuous warming to 80 DEG C, is incubated 30 minutes, and then continuous warming to 130 DEG C, is incubated 60 minutes; The pressure in two stages is 0.5Mpa, is finally cooled to room temperature, obtains the polymer matrix composites of curing molding.
(2) demoulding: open vulcanizer, cleans out optical fiber Bragg raster string lead-in wire resin around, prevents from destroying fiber grating because of the adhesion of resin; Keep wire straight, avoid it to bend, affect signals collecting.Pull the exposed parts of teflon cloth, make the composite product demoulding.
(3) test: the compound substance standard specimen of the successful demoulding is placed in universal testing machine and measures Poisson ratio, act on tensile stress sigma in the vertical separately, and without other external force.Test loading velocity is 2mm/min; Because the breaking elongation of individual carbon fibers is about 1%, so the standard specimen draw ratio in restrained stretching test is 0.5% ~ 0.6%, thus ensure it is measure Poisson ratio in elastic limits.
Concrete implementation step:
A) control environment temperature, and warranty test carries out under constant temperature.
B) standard specimen is put in fixture, the long axis of standard specimen must be made to become same straight line with the axis of testing machine, prestress is loaded to standard specimen, tight a little standard specimen; Prestrain ε≤0.05%.
C) go between prior bending in standard specimen, the unified FBG drawn from side incoming fiber optic grating demodulation instrument.
D) with the loading velocity stretching standard specimen of 2mm/min, until strain reaches 0.5% ~ 0.6%; Dynamic realtime gathers the centre wavelength data of grating region simultaneously.
(4) data processing: the centre wavelength data of the grating region that process Real-time Collection arrives, obtain the time dependent curve of centre wavelength of each grating region of optical fiber Bragg raster string; With longitudinal reflection wavelength for horizontal ordinate, horizontal reflection wavelength is ordinate, obtains a relation curve, and this slope of a curve is exactly the Poisson ratio ν of compound substance standard specimen.
Embodiment 2:
A kind of optical fiber Bragg raster string method of testing of continuous fiber reinforced composites Poisson ratio.
(1) making of compound substance standard specimen: be wound around one deck teflon adhesive tape equably, then coated one deck teflon cloth on whole framed 5 and lead-in wire groove 4.At mold cavity middle berth N layer (N >=20) polymer matrix composites prepreg 1, and two prepreg wherein lay optical fiber Bragg raster string respectively, namely an optical fiber Bragg raster string 2 is laid in n-th layer (N-10>n > 5) longitudinal (fiber 0 ° of direction), lay one at the n-th+i layer (N-14 >=i > 5) horizontal (fiber 90 ° of directions) and use fillet shape, the optical fiber Bragg raster string 3 of prepreg 8 protection in the same way, these fillet shapes, the machine direction of prepreg 8 is identical with the direction of optical fiber Bragg raster string 3 in the same way, thickness is identical with full wafer prepreg thickness, be 0.1 ~ 0.2mm, shape is rectangle, distribution 4 grating regions on longitudinal optical fiber Bragg raster string 2, grating region and test specimen edge should at least interval 40mm, lateral light fiber Bragg grating string 3 distributes 2 grating regions, and grating region and test specimen edge should at least interval 5mm, tail optical fiber use teflon pipe protect, make optical fiber Bragg raster string can in the scope of-80 DEG C ~ 280 DEG C Long-Time Service.Curing is compound substance hot compression molding method.
Concrete implementation step:
A) on whole mould side wall deckle board 5 and lead-in wire groove 4 thereof, be wound around one deck teflon adhesive tape equably, then use individual layer teflon cloth completely coated, they and mould side wall deckle board 5 are tightly fitted.
B) prepreg guillotine is utilized successively to be cut by being parallel to machine direction (fiber 0 ° of direction) by prepreg, the fillet shape prepreg being used as protection grating region that the prepreg that the face inside dimension of cutting out is 260mm*40mm, face inside dimension are 40mm*10mm.
C) be that the prepreg of 260mm*40mm is successively routed in the die cavity that surrounded by the lower bolster 7 and ready mould side wall deckle board 5 that coat release agent in advance as requested by cutting the face inside dimension obtained, ply sequence is [0 °]
20.In process of deployment, lay one group of optical fiber Bragg raster string 2, as axial strain sensor in the 6th layer of longitudinal direction (fiber 0 ° of direction); One group of optical fiber Bragg raster string 3 with the protection of fillet shape, in the same way prepreg 8 is laid in the 12nd layer of transverse direction (fiber 90 ° of directions).The lead-in wire of longitudinal optical fiber Bragg raster string 2 is bent, bending radius is 2cm, unified fixture conflict of drawing from side to avoid lead-in wire and universal testing machine, make lead-in wire can in order, incoming fiber optic grating demodulation instrument easily, ensure light signal strength, avoid light signal to produce chirp phenomenon simultaneously.
D) cover the cope match-plate pattern coating release agent in advance, close die, insert in vulcanizer; Heating pressurization, makes prepreg hot-forming in full rigidity closed molds, realizes the solidification of compound substance.The heat pressing process adopted is first from room temperature continuous warming to 80 DEG C, is incubated 30 minutes, and then continuous warming to 130 DEG C, is incubated 60 minutes; The pressure in two stages is 0.5Mpa, is finally cooled to room temperature, obtains the polymer matrix composites of curing molding.
(2) demoulding: open vulcanizer, cleans out optical fiber Bragg raster string lead-in wire resin around, prevents it from destroying fiber grating; Keep wire straight, avoid it to bend, affect signals collecting.Pull the exposed parts of teflon cloth, make the composite product demoulding.
(3) test: the compound substance standard specimen of the successful demoulding is placed in universal testing machine and measures Poisson ratio, act on tensile stress sigma in the vertical separately, and without other external force.Test loading velocity is 1mm/min; Because the breaking elongation of individual carbon fibers is about 1%, so the standard specimen draw ratio in restrained stretching test is 0.5% ~ 0.6%, thus ensure it is measure Poisson ratio in elastic limits.
Concrete implementation step:
A) control environment temperature, and warranty test carries out under constant temperature.
B) standard specimen is put in fixture, the long axis of standard specimen must be made to become same straight line with the axis of testing machine, prestress is loaded to standard specimen, tight a little standard specimen; Prestrain ε≤0.05%.
C) will go between incoming fiber optic grating demodulation instrument.
D) with the loading velocity stretching standard specimen of 1mm/min, until strain reaches 0.5% ~ 0.6%; Dynamic realtime gathers the centre wavelength data of grating region simultaneously.
(4) data processing: the centre wavelength data of the grating region that process Real-time Collection arrives, obtain the time dependent curve of centre wavelength of each grating region of optical fiber Bragg raster string, corresponding relation according to raster center wavelength variable quantity and microstrain obtains longitudinal microstrain of compound substance standard specimen and horizontal microstrain, with longitudinal microstrain for horizontal ordinate, horizontal microstrain is ordinate, obtain a relation curve, this slope of a curve is exactly the Poisson ratio ν of compound substance standard specimen.
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 method of testing for continuous fiber reinforced composites Poisson ratio, is characterized in that, comprises step as follows:
1) making of compound substance standard specimen: teflon adhesive tape and teflon cloth are coated on successively on mould side wall deckle board and lead-in wire groove thereof; At mold cavity middle berth N layer N >=20 polymer matrix composites prepreg, and lay along machine direction and the multiple optical fiber Bragg raster strings perpendicular to machine direction on different prepreg respectively; Then, curing molding;
2) demoulding: clean out fiber grating lead-in wire resin around, keep wire straight, pull the exposed parts of teflon cloth, make the composite product demoulding;
3) test: under constant temperature, the compound substance standard specimen of the demoulding is placed in universal testing machine and measures Poisson ratio, separately in j direction, namely on fiber 0 ° of direction, effect normal stress σ
j, and without other external force;
4) data processing: the centre wavelength data of the grating region that process Real-time Collection arrives, obtain the time dependent curve of centre wavelength of each grating region of optical fiber Bragg raster string, corresponding relation according to raster center wavelength variable quantity and microstrain obtains longitudinal microstrain of compound substance standard specimen and horizontal microstrain, and then calculates Poisson ratio.
2. the method for claim 1; it is characterized in that; step 1) in; described lay respectively on different prepreg along machine direction and perpendicular to the concrete steps of multiple optical fiber Bragg raster strings of machine direction at n-th layer N-10 > n > 5 longitudinally; i.e. fiber 0 ° of direction; lay multiple optical fiber Bragg raster string; at n-th+i layer N-14 >=i > 5 laterally; i.e. fiber 90 ° of directions, lay the optical fiber Bragg raster string of multiple fillet shape, prepreg protection in the same way.
3. the method for claim 1, is characterized in that, step 1) in, described curing molding method is compound substance hot compression molding method.
4. the method for claim 1, is characterized in that, step 1) in, the grating region of described optical fiber Bragg raster string can not be arranged on the point of crossing of 0 ° and 90 ° direction optical fiber Bragg raster string.
5. the method for claim 1, is characterized in that, step 1) in, described optical fiber Bragg raster string distributes 2 ~ 6 grid regions.
6. method as claimed in claim 2, is characterized in that, step 1) in, the thickness of described fillet shape, in the same way prepreg is identical with full wafer prepreg thickness.
7. the method for claim 1, is characterized in that, step 1) in, the paving location of optical fiber Bragg raster string at the middle position of standard specimen, but should to note between 0 ° and 90 ° of direction optical fiber Bragg raster strings at least 5 layers, interval prepreg.
8. the method for claim 1, is characterized in that, step 1) in, described in be parallel to the optical fiber Bragg raster string of machine direction lead-in wire at the region bends near standard specimen end, unifiedly to draw from side.
9. the method for claim 1, is characterized in that, the tail optical fiber of described optical fiber Bragg raster string uses teflon pipe to protect.
10. a preparation method for the standard specimen of continuous fiber reinforced composites Poisson ratio, is characterized in that, adopts following steps:
1) making of compound substance standard specimen: teflon adhesive tape and teflon cloth are coated on successively on mould side wall deckle board and lead-in wire groove thereof; At mold cavity middle berth N layer N >=20 polymer matrix composites prepreg, and lay along machine direction and the multiple optical fiber Bragg raster strings perpendicular to machine direction on different prepreg respectively; The described lead-in wire being parallel to the optical fiber Bragg raster string of machine direction is at the region bends near test piece end, and unification is drawn from side; Then, curing molding;
2) demoulding: clean out fiber grating lead-in wire resin around, keep wire straight, pull the exposed parts of teflon cloth, make the composite product demoulding, obtain the standard specimen of continuous fiber reinforced composites Poisson ratio.
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| CN201510214015.2A CN104807698B (en) | 2015-04-29 | 2015-04-29 | A kind of method of testing of continuous fiber reinforced composites Poisson's ratio |
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| CN108760490A (en) * | 2018-05-18 | 2018-11-06 | 山东工业陶瓷研究设计院有限公司 | The detection method of Continuous Fiber Reinforced Ceramic Matrix Composites room temperature compression performance |
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