Chuong7-Vat Lieu Com

7/29/2019 Chuong7-Vat Lieu Com

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VT LIU COMPOSITE

TRNG I HC BCH KHOA THNH PH H CH MINH


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COMPOSITE


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COMPOSITE


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COMPOSITE


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COMPOSITE


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TNG QUAN

Ti sao chng ta li quan tm ti vt liu composite ???

Tnh cht cc vt liu truyn thng

Kim loi: bn, do, nng

Polyme: bn khng cao, tuy nhin rt do v nh

Ceramic: cng, dn, rt bn vi nhit ,

Chng ta c th to ra vt liu c nhng tnh nng u vit

ca mi loi vt liu truyn thng khng ????


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Vt liu composite l vt liu t hp t hai hay nhiu loi vt liu c bn cht khcnhau. Vt liu to thnh c nhng c tnh tri hn c tnh ca hai vt liu thnh

phn khi xt ring l

I. KHI NIM


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I. KHI NIM

Nn L pha lin tc ng vai tr:

Lin kt cc phn t ct thnhkhi composite ng nht.

Che ph v bo v ct trnh cch hng c hc v ha hc cami trng.

Truyn ti v phn b ti trngsang vt liu ct lm gim ng

sut tp trung.To kh nng d dng tin

hnh cc phng php gia cng

composite thnh cc chi tit theo

thit k

Ct l pha gin on ng vai tr

To nn bn cao, modul n hi

cao cho composite


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I. KHI NIM

Ct l pha gin on ng vai tr to nn bn cao, modul n hi cao

cho composite

Cc yu t nh gi

Tnh gia cng c hc

Tnh khng ha cht, mi trng , nhit

Kh nng phn tn vo trong nn

C thun li cho qu trnh gia cng hay khng

Gi thnh


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- Gi thnh r hn thp khng g.

- T s tnh nng c l/gi c v t s tnh nng c l/ khi lng cao hn st

thp nhiu.

- Nh.

- Phng php gia cng ch to n gin v a dng.

- D to hnh thay i, sa cha.

- Chi ph u t thp.

II. C IM CA VT LIU COMPOSITE


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II. C IM CA VT LIU COMPOSITE


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Nguyn tc gia cng trong vt liu composite

Khi lc tc dng vo n, chng s bchuyn hng, to thnh nhng lung

lc mi c cng yu hn, sau nhiu

ln chuyn hng v truyn mt phn

lc cho n, cho nn th lc b trit tiu

hon ton

Khi lc tc dng vo n, mt phn lc

s b ht n hp thu, phn cn li s

c truyn sang ht n khc, kt qu

l lc tc dng s gim dn cng v

b trit tiu sau khi i qua nhiu ht n

F1

F2

F3

F1>F2>F3

n cng

n mm

F


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Mi vt liu u c nhng tnh cht ring v rt c trng ty theo yu cu v

tnh cht ca vt liu composite m chng ta la chn vt liu cho ph hp. Mt

im cn quan tm na l s khc bit v khi lng ring ca hai pha s

nh hng rt ln n sn phm.

V d: vt liu composite t gang v silicabit (SiC). Do dsilicabit


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Lin kt ha hc

V d: composite gia si thy tinh vi nha c cha silan

S kt dnh gia ct nn

y l yu t quyt nh n c tnh ca vt liu composite. Cc dng kt dnh gia

ct v nn l:

Cc yu t nh hng n tnh chtcomposit


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Lin kt tnh in

Lin kt c hc: xut hin khi c s tip xc trit gia hai pha, ph thuc vo

din tch tip xc gia hai pha.



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Khe khng kh

n

Nn Bt kh

Lin kt cng cc

V d: to b tng gm ct, , xi mng v thp c du trn b mt, do xi mng

phn cc, trong khi du khng phn cc lm cho s tip xc gia xi mng vthp khng tt, lm cho tnh nng ca b tng ct thp khng cao.

Thng thng cc yu t lm nh hng n tnh kt dnh hay tnh cht ca vt liu

l do s hp ph v thm t khng tt, linh ng ca vt liu nn ( nha):

Cc yu t nh hng n tnh cht composit


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Uniaxial

constraint



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Thng thng c tnh ca vt liu composite s tng khi ta tng hm lng n

(ct), tuy nhin ch tng ti mt mc no , nu tip tc tng hm lng n

ln, c tnh s gim dn.

T l nn/ct

c trng hnh hc ca vt liu tng cng

c xc nh bi : hnh dng, kch thc, tp trung v phn b:



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Phn b khng u Phn b u


S phn b:


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Hnh dng


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Kch thc:


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Trong trng hp composite vi cht n dng si, phng ca si quyt nh

tnh d hng ca vt liu.



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C nhiu phng php gia cng nhng phng php no cng cn m bo phn

tn u cht n trong pha nn. Ngoi ra, lm cch no gim thiu cc khuyt tt

trong qu trnh gia cng nh bt kh, qu nhit cng l mt trong cc yu t quyt

nh n tnh cht ca vt liu composite

Phng php gia cng composit



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Phn loi

Theo bn cht v thnh phn

Composite nn hu c(PMC)cng vi vt liu ct dng:

Si hu c: Polyamit, kevlar

Si khong: thy tinh, cacbon

Si kim loi: Bo, nhm

Composite nn kim loi(MMC)vi n dng ht:

Si kim loi: Bo

Si khong: Cacbon, silic

Composite nn ceramic (CMC)vi vt liu ct dng:

Si kim loi: Bo

Ht kim loi.

Ht gm.


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Theo hnh dng n

Phn loi

Composite gia cng bng ht:

Ht c nhiu dng hnh hc khc nhau nhng nhn chung kch thc ca

chng tng i ng u theo mi hng.

gia cng hiu qu, ht phi nh v phn tn ng u trong nn.

C th phn thnh composite ht th v ht mn ( < 0.1 micromet).

Gm c:

Composite nn kim loi

composite nn ceramit.

Composite nn polyme


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composit ht th l btng:ximng l nn, ct v si l ct.

composit ht mn: cao su n

than en kch thc ht 20 50 nm

Phn loi


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Ru l nhng n tinh th rt mng vi t l gia chiu di v ng knh l rt ln. N

khng tn ti khuyt tt nn bn rt cao, v vy rt t tin. c bit ru tinh th rt kh

lin kt vi vt liu nn. Nhng vt liu ru tinh th bao gm graphite, silicon carbide,

silicon nitride, aluminum oxide.

Vt liu lm si dng a tinh th hoc v nh hnh c ng knh nh, thng thng l

polymer hoc ceramic ( polymer aramids, glass, carbon, boron, aluminum oxide, siliconcarbide).

Dng dy c ng knh ln hn, nhng vt liu in hnh nh: molybdenum v tungsten.

Dy c dng nh nhng si thp gia cng trong lp xe t.

Theo hnh dng n

Phn loi

composit gia cng bng si

Mt s dng si:


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Theo dng cu trc

Phn loi

Cu trc lp:


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Bao gm 2 lp mng cng bn

ngoi bao bc mt lp li dy

bn trong.

To nn mt cu trc nh nhng

c cng v bn tng i

cao.

Phn loi

Theo dng cu trc

Composit dng sandwich


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M hnh trn m t composite sandwich (A) v cc thnh phn ca n

gm: cc tm mt (B) v li c cu trc t ong (C)

Cu trc t ong thng thng lm t hp kim nhm hoc polymer aramid.

Composit cu trc sandwich c nhiu ng dng: tm lp mi, sn, tngtrong xy dng, hoc cnh, thn my bay, mt phn ui my bay.

Composit dng t ong

Theo dng cu trc

Phn loi


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Cng ngh ch to vt liu composite nn polymer

Gia cng bng tay ( hand-lay-up):dng c hay con ln qut nha ln khun ph chng dnh, t vi ln, qut nha, dng con ln ui bt kh v ln cht, tip tc

nh th cho n khi t yu cu.

Gia cng p sut thng


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Chi ph u t thp

Quy trnh n gin v linh hot. C th s dng nhiu loi si v nh hng

si khc nhau

Thch hp sn xut cc sn phm c kch thc ln

Cht lng sn phm ph thuc nhiu vo tay ngh nhn cng.

ng u ca sn phm khng cao

Khun h cho nn gp nhiu vn v dung mi c hi, d bay hi.

Khng thch hp sn xut cc sn phm c kch thc nh, tinh so cao.

U IM

NHC IM


Gia cng bng tay ( hand-lay-up)

C


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Phng php phun nha si ( spray-up):si

th c ct ngn phun vo cng lc vi nha

tun t cho n khi t b dy yu cu, dng conln ui bt kh.

Gia cng p sut thng



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C h h t t li it l


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Thch hp sn xut cc sn phm c kch thc va v ln, c mtkhun un ln.

Chi ph u t thp.

Khng thch hp sn xut cc sn phm c tinh so cao.

Kh kim sot c t l nha si, b dy sn phm. Nhng thng s

ny i hi tay ngh ca ngi cng nhn.Khun h cho nn vn v c hi ca dung mi cn phi c

quan tm.

Ch to c mt mt lng

U IM

NHC IM

Phng php phun nha si ( spray-up)


C h h t t li it l


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Phng php cun si ( filament Winding) :

cun si c ko qua mng thm nha trc,

sau cun ph ln mt khun, dng snxut ng dn, thng cha nh

Gia cng p sut thng


C h h t t li it l


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Thch hp sn xut cc bnh, ng chu p sut.

Thch hp sn xut cc sn phm c kch thc khc nhau

Chi ph u t thp: nguyn liu u vo r, h thng thit b khng qut so vi mt s phng php khc.

C th tin hnh mt cch t ng

Hn ch trong sn xut cc sn phm c cu trc kn, vi nhng cu

trc h ( bn tm) th phng php ny khng thc s thch hp

Kh kim sot c ng u v t l nha si trong sut b dy

sn phm.

U IM

NHC IM

Phng php qun si ( filament winding)


C h h t t li it l


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Gia cng di p sut


c p nng ( hot press moulding):nha si

hay n c trn u, cho vo khun c

di p sut v nhit cao, sn phm c

nh hnh theo 3 chiu



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c p ngui ( Cold press moulding):ging c p nng nhng tin hnh nhit

thng.

Gia cng di p sut




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C th sn xut c cc sn phm c t l si cao.

C th sn xut cc sn phm c kch thc t nh cho ti ln.

Nng sut cao.

Khng i hi nhiu nhn cng

bng lng b mt, chnh xc cao v thch hp cho vic sn xut

cc chi tit c tinh so.

Hn ch trong vic sn xut cc sn phm c hnh dng n ginnh a phng.

Kh sn xut cc sn phm i hi b dy ln.

D gy h hng khun, to nhiu bavia.

Chi ph u t cao.

U IM

NHC IM


Gia cng di p sut



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n ko ( pultrution):cht n trn vi nha np lin tc v ko qua li c gia

nhit, nha ng rn mt phn hay hon ton khi qua li to hnh.




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Qu trnh din ra lin tc, nng sut sn xut cao, chnh xc cao.

Qu trnh din ra gn nh t ng, khng cn nhiu nhn cng lnh ngh.

Thch hp sn xut cc sn phm c mt ct ngang khng i dc theochiu di.

Chi ph u t cao.

Khng thch hp cho cc sn phm c hnh dng phc tp, b dy mng.

Nhng sn phm cn kh nng chu lc phc tp khng c sn xut

theo phng php ny do cc tnh cht ca chng phn ln b hn ch theo

hng dc trc.

U IM

NHC IM


n ko ( pultrution)


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c tim ( injection):n cho vo khun, sau nha lng tim vo khun, gia

nhit ng rn. Cng c th trn nha v n trc ri tim vo khun, ng

thi phn ng ng rn xy ra trong khun.




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Kh nng t ng ha cao.

Nng sut cao.

C kh nng sn xut cc sn phm c kch thc va v nh.C th sn xut cc chi tit tinh so c chnh xc cao.

Chi phi u t cao.

Yu cu p sut ln, d gy h hng khun.

Ch c th s dng cho cc loi si ct ngn.

U IM

NHC IM


c tim ( injection)


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