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In t e rna t i ona l Journa l o f Mode rn Phys i c s BVol . 17, Nos . 8 & 9 (2003) 1744-1749 World Sc ient i f ic Publ i shing Company

ACTIVE VIBRATION CONTROL OF EPOXY MATRIX COMPOSITE BEAM SWITH EMBEDD ED SHAPE MEMORY ALLOY TiNi FIBERS.

T. AOKI*Graduate School of Engineering, Saitama Institute of Technologyaoki@oita-ct.ac.jpA. SHIMAMOTODepartment of Mechanical Engineering, Saitama Institute of Technology1690 Fusaijii, Okabe, Saitama, 369-0293, Japan

Received 4 M y 2002Received 7 November 200 2

In this paper, epoxy matrix composite beams with embedded TiNi (SMA: Shape Memory Alloy) fiberare applied to enhance the strength and fracture toughness of the machinery components. It is also wellknow n that SMA show s the remarkable changes of stiffness and damping ratio between martensite atlower temperature and austenite at high temperature. A shape recovery force is associated with inversephase transformation of SMA. The effects of heating with current and pre-strain in TiNi fiber of SMAon vibration characteristics are experimentally investigated. The active vibration control is achieved bycontrolling the current and p re-strain

1. IntroductionModern high-rise buildings and bridges are designed so that they can minimize thedamage from earthquakes and natural disasters. By detecting with sensor installed in theconstruction material, the computer of a smart (intelligent) material system analyzes dataand gives optimum control signals. Thus damage by quakes is controlled andminimized.1 Figure 1 is a schematic of the basic functional factors of the smart(intelligent) material systems. SMA (Shape Memory Alloy) causes crystal phasetransformation in response to changes in temperature and stress. In the process thematerial characteristics such as stiffness changes greatly.2 This research aims to developof the smart (intelligent) m aterial system using two m aterials, epoxy resin and SM A.

Here, we embedded reinforced TiNi fiber in epoxy matrix composite beams andmade specimen. Changing that current level can vary the temperature of the TiNi fiber.When the temperature of the TiNi fiber reaches its transformation temperature, the SMArestores its form which generates suppression on deflection and increases the stiffness.

In this experiment, we found that our epoxy matrix composite beams have dampingeffect against earthquakes or vibration by strengthening the stiffness of the material.

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Actuator(Effector)

environmentalChanges

Fig. 1. Schematic of the basic functional factors associated with smart (intelligent) material systems.

2. Principal of Damping Method against VibrationThere are three methods3 to reduce vibration such as the method of rational architecturaldesigning, vibration-proof method and damping method. Our experiment is categorizedin this third method. This method has an effect that decreases the vibration in the vicinityof the resonance frequency. In this experiment, we changed the response characteristicsof the specimen which is exposed to external vibration by changing its resonancefrequency and thus we proved the damping effect.

(a) z z z z s t r ^ sEpoxy matrixTiNi Fiber; ; ; ; ; , * , \ (Aphase) ~ < lhard]Shape Memory' ' Heat Treatment(M phase)

Pre-strain tso f tJ

(M phase)Heating above AfTemperature

(A phase)SME - Fiber Shrinkage

Table 1 Mechanical property of constituentsMaterial Young's Poisson Tensile

Modulus(GPa) Ratio Strength(MPa)TiNi fiber 30(Ms)

82(As)Epoxy resin 60.43

0.39Ms:Martensite As:Austenite

120~130(Ms)170(As)50

Fig. 2. Basic design concept of intelligent composite material

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1746 T. Aoki & A. Shimamoto

TiNi Fiber

te 165 TiNi Fiber^fHTTt"1

'2 2 2 2 ' 2< 20 ?Fig.3 Schematic of specimen

3 . Specimen and Experimental Method3.7. SpecimenThe specimens of this experiment are epoxy resin matrix composite beams withembedded reinforced TiNi fiber. The basic design concept of the specimen is shown inFig. 2. The schematic of the specimen is shown in Fig. 3. The table 1 shows themechanical property of constituents4 of the TiNi fiber and the epoxy resin. T he specimenthickness is 2 mm, width is 20 mm and length is 165 mm . The diam eter of the TiNi fiberis d = 0.4 mm. The fibers were first heated for 30 minutes at 500C in the air and thenwere annealed in the ice water. Four transformation temperatures5 of the TiNi fiber weredetermined: martensitic start Ms = 31C, martensitic finish Mf = 15C, austenitic startAs = 57C, and austenitic finish Af = 63C. The heat treated TiNi fiber was given fourkinds of tensile pre-strain ept = 0, 1, 3 and 5%. These fibers are embedded in parallel inthe epoxy matrix smart composite beams at 2mm intervals. In the process of producingthe specimen, the both ends of the fibers should be fixed firmly so that they can keeptheir pre-strain.3.2. Experimental MethodThis experimental system consists of a vibrator and a regulated DC power supply. Theimpedance head of the vibrator supported the center of the specimen. By using theregulated DC power supply device, five levels of current, 0, 1, 2, 3 and 3.5 A by stages,was applied directly to the TiNi fiber and at the sane time, vibration was given to thespecimen. Meanwhile the resonance frequency and the loss factor of the specimen weremeasured. As a result, the dynamic damping effect was observed each time when fivedifferent current was applied to the TiNi fiber.

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Active Vibration Control of Epoxy Matrix Composite Beams 1 7 4 7

4. Results and Discussion

4.1. Young's ModulusFigure 4 shows a relation between Young's modulus and applied current. It shows thefact that the more pre-strain increases the larger Young's modulus becomes. Conversely,as the current increases Young's modulus becomes smaller. When the pre-strain is 5%,the Young's modulus value decreased by 5.0% at 3.5 A compared to that at 1 A.4.2. Frequency Characteristic ofSMAFigure 5 shows a relation between loss factor and resonance frequency. As it shows,when the tensile pre-strain increases, the resonance frequency of the specimen alsoincreases, but on the other hand, the loss factor decreases. In particular, when the pre-strain is 5%, comparing to the loss factor at 10 Hz, it decreases by 86.8% at 100 Hz.Figure 6 shows a relation between loss factor and current when the resonance frequencyis 100 Hz. It can be found that the more current is applied the more loss factor decreasesregardless of the percentage of the pre-strain.

? 55O3O1 45co

tl rSi1 i i I

0% 1%A 3%0 5%

r0 1 2 3 4

C u r r e n t [A ]Fig . 4 Re la t ion be tw een Young ' s modu lu s and

app l i ed cu r ren t .

o- I 0 . 1

0 . 0 1 J

" 0 *cm

^ A 3 *0 5

s=a=xrx r3 4

Curren t [AJ

1 -1

saoss: oA QAnu

0% - 0A 1% - 3 AA 3 % - 3 A

y61 1 0 1 0 0 1 0 0 0 1 0 0 0 0

R e s o n a n c e f r e q u e n c y [ H z ]Fig . 5 Re la t ion be tween los s fac to r and re s on ance

f requency .

0 . 0 1 0 . 0 2 0 . 0 3T i m e [s ]

F ig . 6 . Re la t ion be tween los s fac to r and app l i ed cu r ren t . F ig . 7 . Re la t ion be tween amp l i tude of v ib ra t ion and t ime .

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4.3. Damping Effect

Figure 7 shows a relation between vibration amplitude and time when the pre-strain is0% and 5%. It is noted when the pre-strain is 5%, the amplitude was damped byapproximately 39.6% compared to the time when the pre-strain is 0%. Figure 8 showsthe damping ratio of the vibration amplitude when the pre-strain is 0% and 5%. Verylittle change is found in the damping ratio under those two conditions. Figure 9 showsthe frequency respon se characteristic of the specimen obtained in Fig. 7 and the dam pingproperty. As it shows the resonance frequency of the specimen is higher when the pre-strain is 5%. On the contrary, when the pre-strain is 5% it was found that the vibrationamplitude is damped more greatly as long as the frequency is less than the fc (108Hz)point where those two forms meet.

s 8070605040302010

0

0%-0A 0 5%-3A + O

*620 40 60 80 100

Xo-t-l100

Frequency[Hz]Fig. 8. Damping ratio of vibration amplitude. Fig. 9. Frequency response characteristic.

5. Conclusion

In this research, we used epoxy matrix composite beams with embedded reinforcedshape memory alloy TiNi fiber as a specimen. We researched the possibility of dampingeffect by controlling Young's modulus and loss factor. As a result, following conclusionscan be obtained.(1) W hen current is applied to the TiNi fiber and the TiNi fiber is heated, the young's

modulus decreases. The Young's modulus value was decreased by 5.0% at 3.5 A incomp arison with that at 1 A. It has been proved that it's possible to preventdestruction by quakes by heating TiNi fiber with current and changing Young'smodulus of composite. Thus basic numerical data has been determined for smartcomposite system.(2) The loss factor decreases as the resonance frequency increases when current isapplied to the TiNi fiber and it is heated. The more current is applied the more lossfactor decreases. The greater the pre-strain the m ore the loss factor decreases.

(3) Changing the stiffness of the specimen causes this damping effect. Thus the

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possibility of the damping effect has been verified against external quakes by controllingthe stiffness of bridges and buildings.

AcknowledgementsThis work was supported by a Grant-in-Aid Science Research [40006169] of theMinistry of Education, Science, and Culture of Japan, and a part of this work was alsosupported by the High-Tech Research Center of Saitama Institute of Technology.

References1. C. A. Rogers, C. Liang and S. Lee, Proc.32nd Structures, Structural Dynamics and Materials

Conference, pi 190 (1991)2. A. Shimamoto, Y. Furuya, N. Kurosawa and H. Abe, Active Vibration Control of 'Smart '

Bridge Model Using Shape Memory Alloy, /SM(A)67-654, p294-299 (2001)3. Society for the study of Damping Material, A Handbook of measuring Loss Factor, pi-8

(1995)4. A. Shimamoto and M. Taya, Reduction in K: by Shape Memory Effect in a TiNi Shape-Mem ory Fiber-Reinforced Epoxy Matrix Composite, JSME(A)63-605, p26-31(1997)5. D. Y. Ju and A. Shimamoto, Damping Property of Epoxy Matrix Composite Beams with

Embedded Shape Memory Alloy Fibers, J oflMSS, Vol.10-July (1999)

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