NASA Technical Reports Server (NTRS) 20020051230: Mechanics of Nanotubes and Nanotube-Polymer Composites

7 Pages·0.64 MB·English

by  NASA Technical Reports Server (NTRS)

NA,gAIVlission
Mechanics of Nanotubes and Nanotube-Polymer
Need_
Composites
Deepak Srivastava, NASA Ames Research Center
C"hengyu Wei, Stanford University/NASA Ames • Onboard computing sy;tems i_orfuture
Kyeongjae Cho, Stanford University autonomou= intelligent vehider
-powerful, compact,low '_;_'_.a9
Madhu Menon, University ofKentucky power"
Mohamed Osmau, Washington State University/Pulhrmn COnsumption,radiation
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'_Highperformance computing .
(Tera- and Peta-flop=)
-processing _tellite data
-integrated spacevehicle engineering
-climate modeli_
• Revolutionary computing technologies
• Smart, compact senmrs, ulttarmalll_obes
• "Advanced miniaturization ofallsystems
Microspacecxaft
Q "Thinking" spacecraft
o Micro-, nano-rovers forplanetary exploration
CarboNnanotube
CVD Carbon Nanotube SEM Images
CNT is atubular form ofcarbon with
diameter assmall as Irim.
Length: few nmto microns.
CNT isconfigumtionally equivalent toa
two dimensional gmphene sheet
rolled into atube.
CNT exhibits extmordinar),
mechanical properties:
Young's modulus over
1Tera Pascal, asstiff as
diamond, and tensile strength
- 200 GPa.
CNT can be metallic orsemiconducting,
depending onchirality. http://www.ipt.arc.nasa.gov at Ames Research Center
m
Outline
- High value ofYoung's Modulus (1.2 -1.3 TPa for SWNTs)
• Nanomechanics of nanotubes (C and BN nanotubes)
plastic collapse - Elastic limit upto 10-15% strain
anisotropic swain-release
nanostructured skin-effect
• C nanotube reinforced polymer composite
increased thermal expansion coefficient
increased Young's modulus
mechanisms and limits of load transfer
•redistribution ofstrain
•sharp buckling leading tobond rupture
•SWNT isstiffer thanMWNT
/
•Experiment: buckling and collapse of nanotubes embedded
f.._r 7 in polymer composites.
/-_ .... _ Compression
o._ "
o.oo:_ _' " ' " ' , I 16%S_m
t
SI.minElzregy - /'
v_s ."_ x'_ Bending Buckle, bend and
loops of thick fractureofthin
tubes..
oooi...... +'o " ' ''_.' 90degf°Id
o.4o, . , ., , . , .!-
o..:o / "L_m_,._a -]
o.2o ./ / Torsion
_•:._o.ti,-/"//_----_sirO_l _'+'+" 1 720 deg twist
o..oj._ - 5o io._ J_._ _£v'
"rune(ps)
D.Srivastava, M. Menon and ILCho, Phys. Rev. Lett. VoL 83, 2973 (1999)
D. Srivastava, M. Menon and ILCho, Ph_'s. Rev. B. toappear, 2OOl
•BN nanot_u_bbe_ based....._:_'_compos*iSte':__'_N:_+_:+'_'__with_aanisotropic'm_l plasticity [__
•Nanostructured skin effect !
ll
ll
-Previous MD simulations with high strain rate:
elastic up 30% (Yakoboson et al *)
Sinmlation: 30% yielding strain from fast strain rate (1/ps) molecular
dynamics simulations -Experimentally feasible strain rate and Temperature
Experiments: 6% maximum strain inSWCNT ropes; 12% maximum
strain inMWCNTs
Simulation:
T=0K, Tersoff-Bretmer potential: Super-elastic up m20%
T=0K, Tight Binding: diamond like defects, collapsed at 12%
Experiment:
Collapsing ofCNT within polymer matrix under compression stress 150GPA 11.5% tensile strained 9%tensile strained
(TEM study) (10,0) T=1600K (5,5) T=2400K
*Yakoboson elal, Comput. Mater• Sci.8,341(1997)
I x a _1 _1 [-!
ITensile strainapplied toa60._long(I0.0)CNT 1
-Arrhenius formula: t----_-1 e(E0 -VKE)/ksT
nsite V
_'o-, ).(.,_ .'.k/ . (Eyring's plastic doforn_ation theory on polymers)
-Activation energy as a function of strain: Ev = E°v - VK_
F_.-VK£
- Yielding: strongly dependent onstrain rate and Temperature -Transition rate: 1- 1 1e kBT
_] rlsite _ _ inversion
-Arrhenious Behavior: Linear dependent on temperature ofthe
slope ofyield strain vsstrain rate
-Parameters obtainedfromfitting of MD simulations' data
e_,= EV,,K+ _ksT In(_) N_
= 3.6eV; ..... ,d
:Strain rate; I: Constant related with vibrational frequency -3 -1
= 8x10 _s
I .:Fon:e constantI :Activation volume: I :Activation energy
:Number ofprocess involving inyielding; _1_ :Site available -Experimental feasible conditions
length ~ 1/_m; strain rate - 1/hour; T - 300K
Length effect: [,Aev= _ kVaTK ln(n _-,°/n°_,e) Yieldstrain:9_ 1%
Temperature effect: (__.___ )r, = (_--_-__. )r: I
_'_Po!;/._er_CN_com_ostte ,_,_
12
o rm,: "r
Structural and thermal properties
Load transfer and mechanical properties
i i
............ -_o.2, - SEM images of polymer (polyvinylacohol)
,i -_ _,,, 1 i i,o,,o, SEM i_mges of epoxy-CNT composite ribbon contained CNT fibers & knotted CNT
r2 ........-_"_'mo) .,v_...a.''r" (s.s) fibers
' Strainml__t.'y_) ,
• C.Wei, D. Srivaslava, and K. Cho, Phys. Rev. Left. (submitted)
• D. Srivastnva, C. Wei, and K. Cho, Appl. Mech. Review (2002)
(L.S.Sdladlcr cLal., AppLPhys. Leal.V731:'3842,1998) lB. Vigolo eLaL,Scimlee, V_9_ P|331. "_)
_ _._¸_:!i¸i_!_¸:¸_::_?_i!i::!_!!!!:!i_`i_i_i_ii¸_+_¸i¸¸_:_i_i_:!_:_W_`_:_ _
•Thermal conductivityofsingle-wallnanotubes
Classical MD: Tersoff-Brenner potentials and
VDW interactions
•Nanotube/polymer composites ashighthermalexpansion
coefficient materials
Polyethylene &(1O,O)CNT :(80d_im #PE
relaxed byMonteCarlo methods, NI_10:20A •Thermal conductivity ofnanotube/polymer composite
long CNT 8%volume ratio)
. _,.."--__-"
Composites prepared at300k;cooled downto 10K
Polymer-CNT composite with rate IK/lps
composites change from liquid statethrough
rubber state toglassystate
m ....
i
•cvo DlalmM 1300-2OOO,,',//askt,_
*Gr|phim (battl pltne) IgO0- 2000W/InK _I i
*CVDS_lom Ctr_idt 2_ -272WtmK _t
Alumirmm Nit/i_ (tln_red) 174- lg2XV/mK*_
-C_!_I_a, 4_0 W/mKaa
•single_11CarImnn_ tope 1750-_M_ _:_-iK#
,_ ,._o._=,, =..itr:.-et-xo,e._,l_st,, i.*_)
.e .lILQ/I¢I_ =._,I_¢_._d&ItcllttdIdIKl]dall7.L¢10-I_04,{L_911. i
:_'._*_"_ __...,t,:
_000 Small system: L/D-2, Np=10 Results: J
•Thermal peak position has astrong
o - ' , i , , dependence onthe radius of the tube
.¢_2_O000O .(,b). , . ," ,ri/O'.xto) __ ,.4i and weak dependence on chirality 0m'i g_ssi TM fr-oGmlass 1.5t0raKnsitionto 175Ktemperature Tg increased
(s'_._iys'l_ _ °Typical peak thermal conductivity ! o_[ composite-'_ liqMd -Thermal expansion coefficients: (K-_)
oof \
_i ,0o0o _ "m,;"*"_,* t isab°ut2000"3000W/mK PE PE-CNT
/ polymer _ \ r<Tg 3.Sxl0 -'4 4.5xI0 _ 1"18%
_300[. _ , = . t . _ , _ . with highly directional beat-flmowaterial T>Tg 8.6 x10-'4 IZOxI0 -'4 1"40_o
2CO0 [- (c) ...._ (to.o) _ •High thermal conductivity
.... ] andwca..k..d..e.h in.idt,
0 't_l-empera_°_r e(K_m '°°(Experimental value: 1.0 x10-4 K- 1;T <Tg)
O0 100 200 300 400 _0 60_
T_-,',_ (K)
M. Osmun nnd D.Srivastava, Nunotechnololev, i VoL 12,21(2001)
i
L__i_:_Ifi_c.r..e...a..s...c......... .._m.:::__ermal:_ex:p::a.nston .of_/_'e_o;_m-_p'osdcS._¢-__•_._ _: 1_/_4[
I [_Bm_an,motmn,and S_Cc Phonon M_es,pt_Nano_¢_ J
CUT:LO-2
un_c_l_._trM*r,_.t o _n_,ot, -,romt_-_ T=2OOK
eompo_le
__"(>;S pol./mot_k s,,._._ ,,.-"
,._.__._.... _VW.-4_
._" _VW.-
_N_ u_: lr_ ....... i -45 _h8mol;3ni_o6#llCowN67,d
> -as CNT: UO-2
unit ofpolyethylene=l? _ .
cN=_otaL_ !b._
"470.74 0.75 0.76 0.77 0.78 0.79 o.0 0.81 0.82
Oenmty(..q/ctr_3)
(Halpin- Tsai' sformula)
Small system: L/D-2, Np=10
Diffusion coefficients of polymer r'_" = E_,E,.,ErVr:MVodoululumse roaftiocomopfositfei,ber matrix and fiber
] with CNTs embedded [
Dependent on geometry, packing of
(ivi, iM,,-i) _: fiber; -aspect ratio of fiber
Diffusion coefficient increased,
especially along CNT axis direction,
toCNT_'oa_n ., indicating enhancement of themaal _[ Ecnt/Em- 1000
conductivity
'! , 1
*Experiments on ABS/CNT & RTV/
CNT show large increase (Rick
Bermrg's group at RICE)
4_
Tempe_atme(K)
*C. Wei. D. Srivastava. and K. Cho (submitted)
5
i_._,_._;_._. _. ........ _ ,. _,_¢÷_*-._:_.;._ _ _:..,_-x_.1_
2o1618 L./D-1000
I --.//
__o
°i -
:L
(MWCNT) (SWCxNT, L/D?I ..... ,Lg.'_, " ...... "
_.000 0,010 0.020 0.030
Volume RatioofCNTfiber
I1"1D. (_ian etat.A_p. Phi. Let,. V76. P2868. 2000:. R.Andrews etal.Ar_. Ph_.LeL. V75. PI329.1999
T=50K I Work hardening ofcomposim TinEMapolyimmaegres moaftrixalignmebnyt stretchionfgCNT 1|
/ with stretching /
-°_ 0.004 .:/Elastio enercjy ofan
_" 0,003 //I isolated CNT(10,0) , __i_i_:_.:_ :_
/
o.oo2
i_ CNTembedded Inpolymer
oO,' • • • • • •
0.001
/ CNT: L/D-2
• .'" unit ofpolyethylene=10
0.5 1 1.5 2 2.5 3
Straino|thecomposite (%) (/Jin _.al.. Appl.Phy¢ LolL,V'/3PI197.199S)
::::......I.I.J' I
-Young's modul_zs of CNT composites 30% higher than polymer matrix
-Stretching treatments enhance Yby 50%
(L/D-2. Np=10) 0.4
[11:Polynle_bulk;Y.1492MPa
[2]: Po_mmlxdka_e_sh_Ch_l_ ;Y.I5_SMPa
0.3 |3]:Composim:Y.1907MPa
[4]:Coml_im att_$treching;Y,,,2308MPa
--0.2 ." //._"_ [1]
J -.J_-es_tale=Ib.a_1,_
o
0.3 _ I_
S_dn_)
Comments
NaQomechardcs ofindividual nanotubes explained experimental
observations, andrevealed novel aJzisotropic strain release inBN
nanotubes
• Realistic strain-rate, temperatureandlength dependent deformation
ofnaaotubes under tensilestrain iddeveloped
• Polymer-nanotube composite isahighthermal expansion coefficient and
diffusion material above glass transition temperature
• Young's modulus increases byupto 30%forlow strainvalues, thiscanbe
further increased bystretching-unstretching cycling ofcomposite
• Multiple-site chemical bonding favors load transfer
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