Tuyen tap bao cao khoa hgc Hgi nghi Khoa hgc ky thuat Do luflng toan quoc lan thi IV HdNgi,ll-200S
ONG DUNG LASER EXTENSOMETER TRONG XAC DJNH THUC NGHIEM CO TI'NH VAT LIEU COMPOSITE COT SOI NEN NHUA
Trdn Minh Til - Dgi hgc Xay dung
Trdn Ich Thinh, Thdi Thi Hdng • Dgi hgc Bdch Khoa Hd Ndi
Tdm tdt:
Bdo cdo trinh bdy dng dung cua Laser Extensometer trong xdc dinh thuc nghiim ca tinh ciia vdt lieu composite thuy tinhlepoxy d diiu kiin binh thudng (nhiit dd vd dd dm phdng) vd dieu kiin mdi trudng dm udt (hdp Ihu nude tinh khiit). Cdc thi nghiim ca hgc nhdm xdc dinh cdc hdng sdvdi lieu, cdc ddc Irung ca hgc cua vdl lieu composite vdi su trg giup cua Laser Extensometer Ihuc hiin trin mdy keo- nen van ndng MTS-RF300 vd INSTRON-5582. Ki't qud Ihu dugc Id ddng tin cdy vdi qui trinh thi nghiem tudn theo liiu chudn ASTM vd dugc thuc hiin trin mdy mdc, thiet bi do hiin dgi.
I. DAT VAN DE
vat lifiu composite ngay cang dugc ttng dung rflng rai va ttfl thanh mflt ttong nhttng vat lifiu tta chuflng trong nhifiu Iinh vuc cia nfin kinh tfi' qufi'c dan do nhttng tinh chdt nfli trfii cua nfi so vfli cdc vat lifiu truyfin thfing: dfi bfin rifing, mfldun rifing cao, kha nang chiu mdi mon, cdch nhifit va cdch dm tflt, nhe,... Vai ttfl cia thuc nghifim cfl hgc dfi xdc dinh co ti'nh vdt lifiu composite nhdm gflp phdn ndng cao cfing nghfi chfi tao vat lifiu Id rdt quan trgng. Dfi xdc dinh chinh xac eg tinh cia mfit vat lifiu composite lflp bdng thuc nghifim, ta cdn phai cfl:
- Mdy thi nghifim chudn (hi dflng difiu khifin; cam bifi'n do luc keo-nen cfl dfl chinh xac cao; thang luc phi hgp; van ttfc keo, nen fln dinh vd cfi thfi tu chgn...).
- Thifit bi do chuyfin vi, bifin dang theo hai phttong cfi dfi tin cay cao.
- Ky thudt thi nghiem phi hgp: kich thuflc hinh hgc vd cflng nghfi tao mdu thi nghifim;
loai vd chfi dfl thi nghifim cdn tifin hdnh; phttong phdp thu vd xi ly stf lifiu v.v...
Vdt lifiu composite lflp cfl't vai thiy tinh/ epoxy Id vdt lifiu true httflng. Dfi ti'nh todn dfi bfin cia mfit kfi't cdu (phan tfi') composite chiu ttang thai ing sudt phang, ngodi dfi bfin phd buy, ta cfin cdn dfin bfin hang stf vat lifiu (hdng sfi dan hfli): E,, E^, G,2 va v.j [1].
Trong thuc tfi, dfi do bifin dang, ngufli ta thttflng gdn cac cam bifin difin ttfl trong ving lam vific cia mdu thi [2], [3]. Vfli cdc vat lifiu khdc nhau cdn phai lua chgn Igai cam bifin phi hgp, gid thanh lai ddt; khi bfi mat mdu thi hi dm uflt thi vific gdn cdc cam bifin Id vfi ving khfi khdn. Phttgng dn s i dung chuyfin vi kfi (Extensometer) da dugc thuc hifin ttong nhifiu thi nghiem nhung thifit hi nay dfii hoi bfi mat mdu thi phai dat dfi nhdn cdn thifit [4], [5]. Chuyfin vi kfi cung chi do dugc bifin dang dgc cia mdu ttong khoang hep gitta hai "cdu"
tie'p xuc. Nhttng ndm gdn ddy, thifit hi do bien dang bdng Laser Extensometer da dugc dua vdo s i dung vd khdc phuc dugc cdc nhugc difim cia cam bifin difin ttfl va chuyfin vj kfi.
Thifi't bj nay cfl thfi do dttgc bifin dang gitta hai vach phan quang bdt ki ttong ving ldm vific.
Laser Extensometer cho phep do dflng thfli bifi'n dang theo hai phttong dgc va ngang nfin ta cfl thfi xdc dinh dugc ngay hfi sfi Poisson cia vat lifiu [6].
478
Muc dfch chfnh eua nghifin ci^ trong bdo eao la xac dinh thuc nghifim eac hang sd dan hdi, dd bin vd biln dang pha buy cua vdt lifiu composite cdt vai thuy tinh-epoxy chi tao tai phdng thf nghiem 6 diiu kifin mfii trucmg bmh thudng (nhifit dd va do im phdng) va d diiu kifin mdi trudng dm udt (ngdm trong nude tinh khifi't) bang cdc thifi't bi do Laser Extensometer trong cac thi nghifim keo, nen dung true va Ifich true .
II. THIET BI DO BIEN DANG LASER EXTENSOMETER
Trfin may MTS- Aliance RF 300, INSTRON 5582 ludn gdn cac cam bifi'n luc dl xdc dinh tai trgng tac dung lfin mdu thfi, dfi dich chuyin tuong ddi gifla hai ban kep mdu cho ta bifi'n dang dai tucmg ddi tuong fing. Phfiong phdp do bifi'n dang dua tt-fin nguyfin ly nay la don gian nhdt va ggi la Simplified Tensile (Compressive) Test. Ngoai ra dl xdc dinh biln dang ngudi ta cdn dung cac thifi't bi do hd trg khac nhu: cam bifi'n difin trd, cam biln do biln dang bang tiep xuc (Extensometer), cam biln do biln dang bang laser (Laser Extensometer).
Do biln dang bang Laser Extensometer Id phuong phap do nhd cam bifi'n tia Laser, dugc phat minh vd dua vdo fing dung tfi nhijng ndm ddu cua thdp ki 90. Ddy Id phucmg phap do khdng tiep xfic nhd tia laser va mfit hfi thdng cam bifi'n quang hgc. Cfing vific ghi vd xfi l^ sd lifiu duge thuc hifin nhd su trg gifip cua mdy tfnh vdi cdc phdn mim tuong thfch cd sdn. Hfi thdng may va cdc thiet bi do dugc mfi ta d hinh I. So vdi Extensometer, nhflng uu dilm cua Laser Extensometer cd thi tdm tdt nhu sau: do dugc biln dang dge cua mdt ehilu ddi bdt ki, khfing cdn tifi'p xuc vdi bl mdt cdn do bie'n dang, sfi dung dugc cho tdt ca cde chung Igai vdt lifiu va trong mgi diiu kifin mdi trudng dm udt hay nhifit dg cao (nhifit dd cd thi sfi dung din i 800 °K).
Hinhl: So do he thdng may va thiet bi do Laser Extensometer
Nguyfin ly do bifi'n dang dgc cua Laser Extensometer cd thi dugc mfi ta nhu sau: tfi ngudn laser, cac tia laser cd cudng dd khdng ddi chilu tdi guong, qua guong cac tia laser phan xa tdi thau kfnh hinh tru rdi chifi'u lfin mdu thf nghifim. Khi guong quay cae tia laser se ndm trong mdt mdt phdng. Ta diiu chinh sao cho mat ph^g nay trung hoac song song vdi true ddi xfing cua mdu thi nghifim. Trong qua tnnh guong quay, tia laser tfi thdu kfnh chilu lfin mdu thi nghifim se tinh tie'n trfin true ddi xfing cfia mdu vdi mdt van tdc tinh tiln khdng ddi do guong quay diu (vdi mfit sd vdng quay khdng ddi). Cac tia nay khi di chuyin tren
nfin son den p h i ttfin bfi mat mdu se khflng phan xa lai. Chi khi cdc tia nay cham vao cdc vach trdng thi mfli bi phan xa trfl lai. Nhfl cfl thdu kinh hfii tu cdc tia laser bi phan xa trfl lai dugc hgi tu vfi tifiu difim c i a thdu kinh. Tai tifiu diem c i a thdu kinh ngufli ta dat mflt photodiode. Tai day tin hifiu dnh sdng dugc chuyfin thdnh tin hifiu di6n. Do cdc dai son phan quang khfing lifin nhau nfin cdc tin hifiu dugc photodiode cho ra la mfit difin thfi analog. Nhfl mflt ADC- card md cdc tin hifiu nay dugc chuyfin dfin mfit bfi phdn tich dfi ta thu dttgc cdc tin hieu digital.
Sau khi p h i mfit Iflp sgn den lfin bfi mat mdu t h i , cdc vach son ttang phdn quang cfl thfi dugc ddn ttt cdc bdng dinh hodc quet son lfin duflng theo kich thttflc da cho sao cho net son phai that sdc net (hinh 3).
Cfi thfi tinh dttgc dfl bifin dang dgc gitta hai vach trdng "i"," j " bdt ki (hinh 3) trfin mdu ttt su khdc nhau vfi thfii gian gitta hai xung difin thfi digital tugng ttng:
^;^' = U-'lll-' = M'-'tt';'
Nguyfin ly do bifin dang ngang hodn todn khdc vfli nguyfin ly do bifin dang dgc. Phep do bifin dang ngang dua trfin nguyfin 1;^ difin tich chifiu sang hi che khudt (shadow image principle). Theo nguyfin ly nay ta cfl thfi do dugc bifin dang tttong dfl'i gitta hai vach trdng"
k" vd "m" theo phttong ngang : £•'"" = A/'"" III'' = hi''" I tl""
Hinh 2 cho thd'y todn canh mdy thi nghiem van nang INSTRON-5582 c i n g thifit hi Laser Extensometer c i a hang Fielder Optoelektionik GmbH tai phflng thi nghifim Trttflng DWB/srHdNfii.
Hinh 2: May thi nghiem INSTRON-S582 va Laser Extensometer III. THl NGHIEM XAC DINH CO TfNH VAT Lifiu COMPOSITE 3.1. Muc dich thi nghiem
' Xdc dinh dfl ngam dm cua vdt lifiu composite Tliuy tinh/Epoxy.
' Xdc dinh ddc ttttng co hgc cua vdt lifiu composite Iflp nhu: mfidun Young doc E„
mfl dun Young ngang E , , mfl dun cdt G,,, hfi stf Poisson i/^ (x,y la hfi trac chung cua vdt lieu composite [I]) ttong difiu kifin binh thuflng (nhifit dfl vd dfi dm phfing) vd trong mfii truflng dm ttflt (ngdm ttong nuflc tinh khifit).
Xdc dinh dfl bfin phd buy keo, vd nen c i a vdt lifiu composite ttong difiu kifin binh thuong (nhifit dfl va dfl dm phflng) va trong mfii ttuflng dm ifit.
480
Hinh 3: Mdu keo va nen v(n cac vach son trdng phan quang tren nen den 3.2. vat lieu thi nghifim.
Vdt lifiu nghifin cfiu la tdm composite 4 ldp (thf nghifim keo) cdt vai thuy tinh-epoxy cd cdu hinh [0/90/90/0], kfch thudc 400x400x3; tam composite cdt vai 10 ldp 400x400x10 (thf nghifim nin) san xudt tai Cdng ty Hod vdt lifiu va fing dung cdng nghfi mdi kfi't hgp vdi DHBK Ha Nfii ( CMANT- 995). Vdi vai thuy tinh, sgi dgc cdng hon nfin dugc la'y lam chudn dl dat cdc t£&n vai thuy tinh theo cdc gdc. Keo epoxy da dugc xfi ly bifi'n tfnh dl tdng thfim tfnh thdm thdu, dUOc bd sung cde chdt active, antioxydante, stabilizate, antistarene va cdc chdt chdng 6 xy hda, chd'ng lao hda do tia tfi nggai theo hifiu fing Barie. Thi cdng bang phuong phap Idn thu cdng, cfi mfit ldp vai thuy tinh dat theo cac gdc xdc dinh kem mdt Idp keo epoxy da trdn cha't hda rdn. Sau 3h thao mdu, mai cdt ba via theo kfch thudc da dinh. Ti 16 vl khfi'i lugng vai thuy tinh trong composite edt vai la 30% vd keo epoxy bifi'n tfnh cung cde thdnh phdn khac Id 70%, khdi lugng thi tfch 1,55-1,62 kg/dm\
3.3. M4U thi nghifim keo va nen.
Tfi ta'm composite 400x400x3, ta cdt ra cac dai chfl nhdt 250x25x3 theo cac phuong 0 khdc nhau, sau dd phay theo kfch thude mdu keo tifiu ehudn. Mdu thi nghifim nen dugc xe tfi tdm 400x400x10 theo kfch thudc tieu chudn vdi gdc 9 khac nhau, sau dd mai thfi rdi mai tinh cac bl mdt mdu nhdt la hai bl mdt tifi'p xfic vdi dia nen. Sau khi gia cdng mdu, ta tifi'n hdnh phun son den vd son eae vach phan quang lfin cdc bl mat edn do biln dang. Mdu thf nghifim keo dugc chfi' tao theo tifiu chudn ASTM 3039-76 va mdu thf nghifim nen theo ASTM-D 3410 [8].
IV. K^'T Q U A THI NGHIEM.
4.1. Thi nghiem xac dinh do ngam am cua vat lieu composite
Trude hit, ta can mdu trude khi ngdm trong nude tinh khifi't bang can difin tix Metier Toledo AL- 204 vdi dd chfnh xdc den 10"* gam. Sau tiimg khoang thdi gian xac dinh (1 ngay- 24h, 3 ngay- 72 h, 5 ngay- 120h, 7 ngay- 168h, 14 ngay, 21ngay, 30 ngay...) ta vdt mdu lfin, lau va thdm khd mdu rdi cdn lai mdu.
Dd ngdm dm tai thdi dilm t duge tinh theo: Am = trong dd m(t) Id khdi lugng mdu do duge tai thdi dilm t, mg la khdi lugng mdu do dugc tai thdi dilm t=0. Do ngdm dm cua cac Igai mdu khac nhau duge tfnh todn va bilu difin bang dd thi trfin hinh 4.
Mdu keo Vai
Hinh 4:
Bifin thien do ngam dm cua mdu keo composite cfit vai Thuy tinh/ Epoxy theo thfli gian ngam mdu.
Nhdn xet: T i dfi thi tten hlnh 4 til thdy:
• Dfi ngdm dm c i a cdc mdu vat lifiu composite cfi't vai T h i y tinh/ Epoxy dfiu tdng theo thfli gian ngam mdu.
. Qui luat bifin thifin cua dfi ngam dm p h i hgp vfli ke't qua nghifin cttu ttong [10]. Ban ddu dfl ngdm dm tang nhanh, sau dfi cham ddn vd cfl ttifi coi nhtt bao hfla sau 720 h.
4.2. T h i nghiem xac dinh cac h i n g so vdt lieu, do ben p h a huy, bien dang pha huy composite cot vai T h u y tinh/Epoxy
Cdc thi nghifim keo va nen dugc thuc hifin tten mdy kfio- nen van nang INSTRON 5582-200KN vd MTS-RF300-300KN voi thifit bi do bifi'n dang hai chifiu Laser Extensometer cua hang Fielder Optoelekttonik GmbH tai phflng ttii nghifim Truflng DHBK Hd Nfli. Vdn tfic keo, nen mdu la 0,2 mm/phit. Dfl dm ttong phflng thi nghifim la 70%, nhifit da phflng 24°C.
Mfl dun cfl huflng cua mdu composite cfi't vai Thiy tinh/ Epoxy chiu keo vd nfin dugc cho trong bang I va 2.
Bang 1. Mo dun c6 hufing eua mdu keo composite cfi't vai Thuy tinh/ Epoxy
E, IGPal
AE, [%1
E. tsE, IGPal [%]
E. AE, [GPal [%]
E,
[GPal
J%L
Khfl 8,845 0 168 h 8,365 -5,43 336 h 7,720 -12,72 504 h 7,580 -14,3
6,193 5,817 5,180 4,840
0 -16,24 -16,36 -21,85
5,668 5,327 4,710 4,374
0 -6,02 -16,90 -22,83
7,713 0 0,26 7,334 -4,94 0,24 7,145 -7,39 0,24 6.847 -11.25 0,24
Bang 2. Mo dun eo hufing cua mdu nen Composite vai Thuy tinh/ Epoxy
E.
IGPal AE,
[%1 [GPal AE,
[%]
E, JGPa]_
AE,
m
— 9 0 ' —90"
E, AE, IGPal r%]
Khfl 8,992 0 168 h 8,555 -4,86 336 h 8,196 -8,85 504 h 7,928 -11.83
6,922 6,391 5,778 5,279
0 -8,60 -17,36 -24,50
6,457 5,720 5,290 4,788
0 -11,41 -18,07 -25,85
8,956 0 0,170 8,492 -5,18 0,146 7,974 -10,96 0,129 7.484 -16,44 0,127
482
1 ,0
: s "
1 °
K..V-
^ ! f e ^ S
j - - « - - Ngn-lUk 1 1" * N(im-33ai 1 1— - • — -NEiin-504h |0 15 30 45 60 75 90 1 eirni
i _..
^
"";:;
1
1
""" il
,;
• • ^ ^ " • I I
Hinh 5: Bien thien ciia mo dun co hudng keo va nen theo gdc dat cdt 6 Hinh 5 bilu difin su biln thien cua md dun cd hudng keo va nen theo gdc ddt cdt va thdi gian ngdm, cac trong dd thi nay khfing bilu difin gia tri cua hfi sd Poisson vi ti 16 qua be so vdi cac dai lugng cdn lai.
Biln thifin cua fing sudt pha hfiy va biln dang pha buy keo theo gdc dat cdt vdi cac khoang thdi gian ngdm mdu khdc nhau dugc thi hifin trfin hinh 6.
--^- _ f, 1
= - ™ - * ^ 5 i ~ - * - ^ - ^ - . - .
15 30 45 60 75 90
Hlnh 6: Bifin thifin cua ttng sudt pha huy, bie'n dang pha huy keo theo goc dat cot 6 Vfli mdu nen, bifin thifin cia ttng sudt phd hiy va bifi'n dang phd hiy dttgc bifiu difin trfin hinh 7.
0 15 30 45 60 75 90
Hinh 7: Bien thien cua ing suat pha buy va bien dang pha huy nen theo goc dat cot 9 Nhdn xet: Ttt cdc kfit qua thu dttgc t i thuc nghifim(do khufin khfl bdi bao , khflng thfi lifit kfi hfi't cdc gid tri bdng sfi), quan sat cdc do thi ta cfl thfi rut ra cdc nhan xet sau:
Cdc hang sfi vat lifiu, ttng sudt pha hiy deu giam khi do ngam dm cia vat lifiu tdng.
Cdc bang sfi vdt lifiu, ing sud't pha hiy, vd bifi'n dang phd hiy cia mdu keo va nfin la khdc nhau vfli vat lifiu composite cflt vai Thiy tinh/ Epoxy .
Cdc mfl dun cfl httflng cia mdu keo va nen voi gfic 6 = 30°, 45° giam nhifiu hon so vfli cdc mdu cfi 6= 0°, 90°. ( chang ban sau thfli gian ngdm 504 h vfli vdt lifiu composite cflt vai mdu 0° giam 14,3%, mdu 30° giam 21,85%, mdu 45° giam 22,83% va mdu 90° giam 11,25%).
V. KET LUAN
Ti nhttng kfit qua thuc nghifim xdc dinh co tinh cia vdt lifiu composite cflt vai Thiy tinh/ Epoxy cfl thfi rit ra nhttng kfit luan sau:
Nhfl Laser Extensometer, cdc hang sfl vdt lifiu cua composite (E„ E,, Gn, vd dac bifit he sfi n|2) dugc xdc dinhvfli do tin cdy cao.
Nhfl phuong phdp do Laser Extensometer , co tinh cia cdc mdu da ngdm dm (ngay sau thfli difim ngam trong nttflc) da dugc do mgt cdch thudn lgi va chi'nh xac.
Kfit qua thuc nghifim cho tha'y:
vat lifiu composite cfl tinh di huflng cao.
Cdc hang sfi vM lifiu, ttng sudt phd hiy deu giam khi dfi ngdm dm cia vat lieu tang.
Cdc hdng sfl vdt lifiu, dug sudt phd hiy, va bifi'n dang phd hiy cia mdu keo vd nen la khac nhau voi vat lifiu composite cfit vai Thiy tmh/Epoxy .
Tdi Ueu tham khdo:
[1] Trdn i'ch Thinh, Vdt lieu Composite- Ca hgc vd tinh loan kit cd'u. NXB Gido due 1994
[2] J. L. Morals, M. S. Moura, J. C. Xavier, In-plane mechanical behaviour of a glasstepoxy composite . UTAD, Quinta dos Prados, Portugal.
[3] R. Rikards, A. Chate, G. Gailis, Indenlificalion of elastic properties of laminates based on experiment design. Inter. Jour, of Solid and Struc. 38 (2001) 5097-5115.
[4] D. Bolcu, G. Stanescu, M. Ursache, Theoretical and experimental study on determination of Ihe elastic properties of Ihe composite materials. Romania Report in Physics, Volume 56, No.l, p. 3-12,2004.
]5] V. Carvelli, T. Truong Chi, M. S. Larosa,...Experimental and numerical determination of the mechanical properties of multi-axial multi-ply composites. Ilth.
European Conference on Composite Materials. May 31-June 3 2004, Rhodes (Greece).
[6] MTS- RF300 andTeslWorkSoftware. Use'rManual, 2002.
17] INSTRON - Use'r Manual, 2001.
18] ASTM Standard D3410-87. Standard Test Method for Compressive Properties of Unidirectional or Crossply Fiber-Risin Composites, American Society for Testing &
Materials.
[9] . M. Karbhari, L. Zhao, K. Murphy, Enviromental Durability of Glass Fiber- reinforced Composites Short Term Effects. Proceeding of CDCC 1998.Sherbrooke, Canada.
[10] Onald. F. Gibson, Principles of composite materials mechanics. McGraw-Hill Inc, 1994.