CN85102277B - Carbon fibers section area and young's modulus measuring meter - Google Patents
Carbon fibers section area and young's modulus measuring meter Download PDFInfo
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- CN85102277B CN85102277B CN85102277A CN85102277A CN85102277B CN 85102277 B CN85102277 B CN 85102277B CN 85102277 A CN85102277 A CN 85102277A CN 85102277 A CN85102277 A CN 85102277A CN 85102277 B CN85102277 B CN 85102277B
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- exciting electrode
- carbon fiber
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- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
Abstract
The present invention relates to a measuring meter for a carbon cellosilk cross section area and a Young's modulus, particularly to a measuring device for measuring the carbon cellosilk cross section area and the axial Young 's modulus. The present invention adopts contactless reception vibration signals which are amplified by making use of a string vibration resonance principle, a vibration part is positioned in a vacuum system, and thus, air damping, non linear vibration, other kinds of interference and loss can be eliminated greatly. Therefore, the measuring precision is high, and the present invention is a useful tool for measuring important mechanics parameters of carbon cellosilk.
Description
The present invention relates to a kind of measurement mechanism that is used to measure carbon fiber monofilament cross-sectional area and axial Young modulus.It utilizes the string vibration resonance principle survey cross-sectional area of fiber, the axial compressional vibration of fiber to survey axial Young modulus, adopts contactless received signal, judges the resonance situation of tested carbon fiber monofilament with this.
The cross-sectional area of present measurement carbon fiber monofilament method more accurately is to adopt string vibration resonance method, central laboratory, carbon element factory, Shanghai once reported in April, 1978 and is entitled as " carbon fiber filament strength method of testing " literary composition and has introduced this measuring method, and designed measurement mechanism is divided into vibrational excitation system, sample clamping system, receiving system, signal amplifying system four parts in the literary composition.Tested carbon fiber wire is fixed by upper grip, lower end system is the weight of m with the quality, receiving transducer directly contacts with filament to receive vibration signal, the sound signal that the vibrational excitation system that is made up of audio signal generator etc. is sent adds to the carbon fiber monofilament through exciting electrode, make the carbon fiber wire starting of oscillation, vibration signal is received, is shown through the signal amplifying system amplification and by oscillograph by the contact probe.Regulate the frequency of audio signal generator, the excitation fiber silk is made fundamental resonance, and measures its fundamental resonance frequency ν
0, then by ν
0, carbon fiber wire density p and length L, just can obtain its sectional area and be according to formula
A＝mg/4ρL2v02
Because when receiving vibration signal, adopt contact, promptly receiving transducer directly contacts with the fibre single thread that is vibrating, do the serious interference that the vibration that makes carbon fiber wire is popped one's head in like this, make wave form distortion, increase the energy loss of vibrational system, thereby brought new error.
Task of the present invention is that a kind of new pick-up unit will be provided, it needn't just directly contact with the carbon fiber wire that is vibrating can receive filametntary vibration signal, judge its resonance state exactly, thereby accurately measure the cross-sectional area and the axial Young modulus of carbon fiber wire.
Task of the present invention is finished in the following manner: at first the contact probe is received and change the capacitance sensing receive mode into.(or between compressional vibration exciting electrode and carbon fibril lower chuck) formed electric capacity is as sensing capacitance between lateral vibration exciting electrode and carbon fiber wire, this electric capacity and the output resistance that is connected on the carbon fiber upper grip, the electric capacity that is connected on the exciting electrode front end are formed four arms that exchange balanced bridge respectively with resistance, and the tie point of this electric capacity and the output resistance that is connected on the carbon fiber wire upper grip and be connected on the electric capacity of exciting electrode front end and the tie point of resistance is respectively two output terminals of this electric bridge connects the differential operational amplifier of a high input impedance at this output terminal.When carbon fiber is excited to show effect forced vibration, the electric capacity of formed capacitor constantly changes between exciting electrode and the carbon fiber wire or between exciting electrode and the lower chuck, its friendshipization amount is directly proportional with the amplitude of fiber vibration, like this because of variation AC signal that is directly proportional with electric capacitance change on superposition on the output load resistance of this electric capacity, because the existence of this alternating current bridge balanced system, make separating with the AC signal that gets on because of the electric capacitance change superposition because of the AC signal of having powerful connections on the pull-up resistor, this superposition gets on to reflect that the AC signal of carbon fiber wire vibration situation is shown by display again after the high input impedance differential amplifier amplifies, the size of the electric signal that shows from display like this, just can correspondingly judge filametntary amplitude size, judge filament thus exactly and whether resonate.
Below with reference to accompanying drawing invention is described in further detail.
Fig. 1 is the synoptic diagram of vibrational excitation system, receiving system, alternating current bridge balanced system.
Fig. 2 is a high input impedance differential operational amplifier wiring diagram.
Fig. 3 is the vacuum system synoptic diagram.
With reference to Fig. 1, fibre single thread (12) upper end is tightly clamped motionless by upper grip (7), and the lower end sprung mass is the weight (13) of m, the effect of weight is to the fixing tension force mg of one of fibre single thread, the outer chuck of image of weight can be clamped fibre single thread, and hang.Form a vibrational excitation system by high voltage direct current generator (1), audio signal generator (2), protective condenser (4), lateral vibration exciting electrode (5) and compressional vibration exciting electrode (6).(1) provides Dc bias; (2) provide the interchange exciting voltage, its frequency is measured by digital frequency meter (3), and frequency-measurement accuracy is 0.1HZ; (4) electric capacity can with 0.1 μ f, withstand voltage be 500 volts, it shields in this device, when (5) and filament (12) or (6) and (13) when colliding accidentally, it can prevent that high direct voltage from directly scurrying into amplifier.
Dc bias with exchange the exciting voltage effect under, (5) excite (12) to do the lateral vibration of string to measure filametntary cross-sectional area; (6) excite (12) to do compressional vibration to measure filametntary axial Young modulus.The measuring sequence of these two amounts is by rotary switc S
1Carry out.
If ν
1Be the resonance fundamental frequency of carbon fiber monofilament when doing lateral vibration; And establish ν
2Be the resonance fundamental frequency of carbon fiber monofilament when doing axial compressional vibration;
ρ and L are respectively the volume density and the length of carbon fiber monofilament, and m is the quality of weight (13), and then the cross-sectional area A of carbon fiber monofilament and axial Young modulus are calculated as follows:
A＝mg/4ρL
2v
1 2
E＝4π
2Lmv
2 2/A
Calculate proof, as Dc bias V
0＞＞exchange exciting voltage amplitude V
fThe time, the suffered excitation force of fiber is:
F＝2KV
0V
fcosωt
So, V
0And V
fBig more excitation force is big more, and the filament vibration is just strong more.
This device utilizes between (5) and (12) in addition or the variation of the sensing capacitance electric capacity in the filament vibration processes between (6) and the lower chuck (13) comes detection fibers silk vibrational state, (5) electric capacity is (14) and between (12), (6) and the electric capacity between (13) be (15), replaced contact probe to receive with the sensing capacitance receive mode.The present invention unites two into one exciting electrode dexterously with receiving sensing device, play simultaneously with a device and excite and receive double action, and apparatus structure is greatly simplified.
Because the existence of sensing capacitor (14) or (15), the AC signal of being come by (2) will be by this electric capacity and through filament and output load resistance (8), and go up intrinsic background AC signal of generation in (8).This background AC signal be exactly fiber when static by sensing capacitor (14) or (15).When (12) vibrate, the electric capacity of this electric capacity is with intercropping varies with cosine at any time, the changes in capacitance amount is directly proportional with the filament amplitude, goes up AC signal that is directly proportional with electric capacitance change (its variable quantity is directly proportional with amplitude) on the superposition because of the variation of this electric capacity in (8) like this.If we can with certain means with the intrinsic background AC signal of (8) with separate because of the AC signal of electric capacitance change superposition, and this superposition input come out, then the size of the vibration of fiber and its amplitude is through exchanging millivoltmeter or oscillograph shows with regard to available after amplifying.
For the useful signal of going up institute's superposition from (8) detects, the present invention has designed one group of alternating current bridge balanced system.Electric bridge four arms are made up of electric capacity (14) or (15) resistance (8), electric capacity (10) or (11), resistance (9) four parts respectively.(14) or the contact B of the tie point A of (15) and (8) and (10) or (11) and (9) be two output terminals of electric bridge, (8) equate with the resistance of (9).Desirable 220K Ω.
Make Dc bias V before the test earlier
0=0, regulating (10) or (11) then, to make the electric potential difference between electric bridge output A, B at 2 be zero, and balance adjustment is in this operation.After the bridge balancing, the fixed background AC signal between A and the B promptly is cancelled.Balancing capacitance when (10) are for the lateral vibration of survey fiber here, (11) are the balancing capacitance when surveying compressional vibration.After the bridge balancing, slowly add Dc bias then, after bias voltage added, bridge balancing can be subjected to slight damage, at this moment needed to regulate (10) or (11) once more and made bridge circuit balance again, and this moment, test can formally begin.
With reference to Fig. 3, in order to suppress the intrinsic background AC signal in the balance bridge circuit, require to use differential amplifier, because the useful signal that fiber vibration produces only is about 2% of background signal, so require differential amplifier that high as far as possible common-mode rejection ratio (CMRR) is arranged, the CMRR of this device is greater than 80db.Three operational amplifiers (21), (22), (29) can be selected the F007B integrated circuit for use, and integrated circuit (21), (22) want strictness to select to make its characteristic identical as far as possible, can improve common-mode rejection ratio like this and reduce noise.Desirable 5 μ of electric capacity (20) in addition, 110K can respectively be got in resistance (23), (25), the desirable 1K of resistance (24), 5K can respectively be got in resistance (26), (27), (28), (30).The output terminal of amplifier can connect ac millivoltmeter or oscillograph is observed, when resonance, and milivoltmeter indication maximal value.Filament, activating system, receiving system, balanced system and amplification system all need electric shield ground connection in addition.
Because the external surface area of carbon fiber monofilament is too big, during the filament vibration, air damping is big, makes resonance peak too wide, and resonant frequency is difficult for judging on the one hand, causes resonant frequency on the low side on the other hand, makes the cross-sectional area that records higher.Therefore be necessary oscillating component is added a vacuum system, to improve measuring accuracy.The vacuum system synoptic diagram is with reference to Fig. 3, and in Fig. 3, (31) are general vacuum glass bell jar, and (32) are vacuum base, and (33) are bleeding point, and the vacuum tightness of system is 10
-2More than the holder.
The present invention is owing to adopt contactless reception and amplification, add that vacuum system can eliminate air damping and other interference and loss to greatest extent, resonance peak is narrowed down greatly, measurement sensitivity greatly improves, given full play to the high-precision advantage of resonant method, and owing to improved measurement sensitivity, just might reduce its Dc bias and interchange exciting voltage (Dc bias of this device is below 80 volts as far as possible, exchange exciting voltage below 10 volts) to eliminate the influence of nonlinear vibration, the measuring accuracy of filament cross-sectional area and axial Young modulus is further enhanced.
Claims (2)
1, a kind of carbon fiber monofilament cross-sectional area and Young modulus measurement mechanism, the involving vibrations exciting electrode, the non-contact type signal receiving system, the alternating current bridge balance device, differential amplifier and vacuum system etc., specimen holder is between last lower chuck, described vibrational excitation electrode comprises lateral vibration exciting electrode and compressional vibration exciting electrode, it is characterized in that adopting the vibration signal of contactless reception monofilament, utilize electric capacity between lateral vibration exciting electrode and carbon fiber monofilament and the electric capacity between compressional vibration exciting electrode and the lower chuck as sensing capacitance respectively, exciting electrode and capacitance sensing type receiving trap unite two into one, insert in the alternating current bridge by the rotary switc order then, constitute an arm of electric bridge, the output terminal of electric bridge inserts a differential amplifier, regulate the output signal of vibration frequency and detecting amplifier, thereby judge whether filament resonates.
2, the measurement mechanism of a kind of carbon fiber monofilament cross-sectional area and axial Young modulus, four arms that it is characterized in that alternating current bridge are respectively by electric capacity (14) or (15), resistance (8), electric capacity (10) or (11), resistance (9) is formed, (14) or the contact P of the contact A of (15) and (8) and (10) or (11) and (9) be two output terminals of electric bridge, before the fibre single thread vibration, regulate earlier (10) or (11) and make that electric potential difference is zero between electric bridge output terminals A, the B, with the background AC signal of balanced system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN85102277A CN85102277B (en) | 1985-04-01 | 1985-04-01 | Carbon fibers section area and young's modulus measuring meter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN85102277A CN85102277B (en) | 1985-04-01 | 1985-04-01 | Carbon fibers section area and young's modulus measuring meter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN85102277A CN85102277A (en) | 1986-10-08 |
| CN85102277B true CN85102277B (en) | 1988-03-30 |
Family
ID=4792389
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN85102277A Expired CN85102277B (en) | 1985-04-01 | 1985-04-01 | Carbon fibers section area and young's modulus measuring meter |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN85102277B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100346152C (en) * | 2004-06-03 | 2007-10-31 | 电子科技大学 | Electrostatic capacitance type apparatus for measuring Young's modulus |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1294413C (en) * | 2004-07-19 | 2007-01-10 | 中国科学院物理研究所 | Method for measuring single linear nanometerial Young's modulus |
| CN102818533B (en) * | 2012-07-29 | 2014-07-16 | 昆明醋酸纤维有限公司 | Methods for detecting section shape and radial profile degree of cellulose acetate fibers |
| CN109540945A (en) * | 2018-08-30 | 2019-03-29 | 北京化工大学 | The method of quantitatively characterizing carbon fiber physical structure |
-
1985
- 1985-04-01 CN CN85102277A patent/CN85102277B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100346152C (en) * | 2004-06-03 | 2007-10-31 | 电子科技大学 | Electrostatic capacitance type apparatus for measuring Young's modulus |
Also Published As
| Publication number | Publication date |
|---|---|
| CN85102277A (en) | 1986-10-08 |
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