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Structural Dynamics
Nakhiah Goulbourne Gary Seidel Dan Inman
AFOSR-MURI Functionally Graded Hybrid Composites
Students: R. Bha;acharya M. Bonakdar X. Ren
• Temperature hysteresis modeling • PiezoresisDve Nano Composites
• Fuzzy Fibers • Damping Modeling &Measurements
• Fuzzy Fibers • CNT nanocomposites
• Macro VibraDon PredicDons
Connec2ons
Ti2AlC and Ti3Si2C from TAMU
Tested & Modeling UM
FEM and Aero Model at TAMU
Fuzzy Fibers from UD
PiezoresisDvity,Damping tesDng Modeling (VT, UM)
VibraDon Modeling UM
SHM Stanford
AFOSR-MURI Functionally Graded Hybrid Composites
Vascular Layer UICU
HYSTERESIS AND RATE DEPENDENCE IN LAYERED STRUCTURES
Nakhiah Goulbourne and R. Bha;acharya (GSRA)
AFOSR-MURI
Functionally Graded Hybrid Composites
SIZE OF GR
AIN
Mechanics of Layered Structures Fundamental Ques2on How does grain size, structure, and strain rate affect the mechanical response
of nano‐layered solids? Objec2ves • Develop high temperature rate dependent consDtuDve model for MAX
phase materials. • Conduct experimental characterizaDon (SHPB) and analysis (fractography) of
dynamic failure and fracture mechanisms in MAX phase materials.
Kinking Nonlinear ElasDc Solids
Year 1: Main Accomplishments
0
100
200
300
400
500
600
0 0.2 0.4 0.6 0.8 1
Strain Rate Dependence of 2024-T6 Aluminum and Ti2AlC
2024-T6 Al 1s-1 [2] 2024-T6 Al 1500s-1 pulse shaped [2] 2024-T6 Al 1500s-1 [2] 2024-T6 Al 1000s-1 [2] Ti2AlC 1100s-1 Ti2AlC 500s-1 Ti2AlC 200s-1
1. Conducted first invesDgaDons of the high rate deformaDon response of Ti2AlC
2. Characterized the dynamic fracture of Ti2AlC: SEM and other imaging techniques
Fractography analysis of Ti2AlC
High strain rate characterizaDon
Year 2: Main Accomplishments • Developed a model for rate dependence in MAX phase
materials at high temperatures • The fracDonal calculus model successfully fit to experimental
data capturing key mechanisms • InvesDgated new physics‐based mechanisms for formaDon of
IKBs and KBs ElasDc buckling Parallel Grains IKB KB
‘Soa’ Grains Homogenous Heterogeneous Kinking CombinaDon Glide Glide
Main Features: • Open loops at higher temperatures • Residual strains Primary mechanisms: • Irrecoverable deformaDons indicate plasDc
transiDon at high temperatures • Irreversible microstructural rearrangement –
formaDon of Kink Bands • Strain increase with unloading indicaDng
internal stress effects
High temperature hysteresis: Ti3Si2C
Barsoum et al, Nat Mat, v.2, 2003.
HYSTERESIS IN COMPRESSION AT HIGH TEMPERATURES
Hysteresis model background Objective: Model the open hysteresis loops present in high temperature behavior. Approach: We use a fractional calculus approach often used to model viscoelastic solids.
- Captures high temperature phenomena - Small number of parameters - Implementable in FEM
Previously a Preisach Mayergoyz model1 was developed by Barsoum’s group:
- Limited to closed hysteresis loops (IKBs only) - Room temperature behavior only - Large number of parameters and highly parameter dependent - Not easily implementable in FEM
σ(t) = Sin(ωt + πa)ε(t) + C(k) Da (ε(t)) ε(t) = A(k) Sin (ωt) Da is the fracDonal derivaDve operator
Stress‐strain Strain‐2me Equa2ons
A new frac2onal calculus approach to model hysteresis in ternary ceramics
Experimental data from Barsoum et al, Nat Mat, v.2, 2003. The model captures the compressive stress‐strain behavior of 3 coarse grained specimens at a parDcular temperature. Different parametric values used for different temperatures (a) 12000C, (b) 11000C and (c) 5000C (a)
(b) (c)
1200° C
1100° C 500° C
Model predictability
The model parameters were fit to the data shown in B. Those parameters were used in the model to predict the response at a different loading rate shown in A.
Fit
PredicDon
A new nano‐scale approach NANOSCALE MODEL:
• Length scale: Barsoum’s model is ‘micro‐scale’ with IKB as independent hysteresis unit. We are proposing a ‘nanoscale’ approach.
• Number of units in system (dislocaDon loop) is not constant.
• Radius and shape of a loop is a funcDon of its posiDon in the IKB and stage of deformaDon.
FUNDAMENTAL HYSTERESIS UNIT
Piezoresi2ve Fuzzy Fibers Objec2ves
Develop a mulDscale model correlaDng changes in nanocomposite electromechanical properDes with damage evoluDon within the nanocomposite interphase surrounding structural fibers (i.e. the fuzzy fiber).
Explore the design space for fuzzy fibers as structural health monitoring sensors through correlaDon of fuzzy fiber design parameters with sensing properDes.
Integrate mulDscale model for fuzzy fibers with higher length scale models for applicaDon in full mulDscale model for the FGHC.
G. Seidel X. Ren
Accomplishments
Last year: • Focused on developing composite cylinders models for the effecDve fuzzy fiber:
• Completed iniDal fuzzy fiber opDcal and sub‐opDcal visual characterizaDon
This year: Composite cylinder model for piezoresisDve response of fuzzy fiber ComputaDonal modeling piezoresisDve response of fuzzy fibe nanocomposites induced
by internal piezoresisDvity of CNTs.
Have begun tesDng fuzzy fiber samples mechanical response and piezoresisDve response (with Lafdi UDRI)
Single scale model MulDscale model
ElasDc properDes (with Lagoudas TAMU)
Electrical properDes
Piezoresis2ve Model for Aligned Nanocomposite Interphase:
2D Periodic hexagonal RVE
CNT
Matrix
IniDal focus on aligned CNT nanocomposite
EffecDve CNT properDes are used
Only inherent CNT piezoresisDvity demonstrated
PiezoresisDve equaDon
y~x~
z~
=
Δ
ΔΔ
12
22
11
66
2212
1211
12
22
11
0000
ε
ε
ε
ρ
ρρ
ggggg
Rotated representa2on of the nanointerphase
ijijij ρρρ Δ+= 0
Piezoresis2ve Algorithm Determine zero strain effecDve electrical conducDvity
Apply load increment and determine strain distribuDon
Apply piezoresisDve equaDon and update local resisDviDes
Apply appropriate electrical potenDal to determine effecDve electrical conducDvity
=
Δ
ΔΔ
12
22
11
66
2212
1211
12
22
11
0000
ε
ε
ε
ρ
ρρ
ggggg
0≠ΔΦ0=ΔΦeff
yyκ0≠ΔΦ eff
xxκ
0≠ΔΦ0≠ΔΦeff
xyκ ijijij ρρρ Δ+= 0
y direcDon x direcDon 0=ΔΦ
Results of Bulk Tension Test (Cont’d): • FOR CNT: mgg •Ω×−== 8
2211 105%10=fV m•Ω×== 7022
011 100492.6ρρ
Contour of conduc2vi2es in the RVE:
Plots of resis2v2es and conduc2vi2es in CNTs with applied boundary strains:
CNT Matrix
R² = 0.9927
0.00E+00
5.00E‐09
1.00E‐08
1.50E‐08
2.00E‐08
2.50E‐08
0 0.0005 0.001 0.0015
Conductivity_YY
Sigma_YY
Linear (Sigma_YY)
Strain_Y
S/m
Mul2scale Piezoresis2ve Algorithm Determine effecDve sDffness and zero strain effecDve electrical conducDvity at microscale/macroscale
Apply load increment and determine strain distribuDon at the macroscale
Apply piezoresisDve equaDon and update local resisDviDes at microscale Apply appropriate electrical
potenDal to determine effecDve electrical conducDvity and update macroscale conducDvity
Apply macroscale element strain and determine strain distribuDon at the microscale
Apply macroscale electrostaDc boundary condiDons and solve macroscale piezoresisDve response
Mul2scale modeling of fuzzy fiber’s piezoresis2ve effect
For the nanocomposite interphase:
mnoplCylindrica
lpkojnimijklCartesian CRRRRC =
For glass fiber: Isotropic
For pure matrix: Isotropic
1. Modeling mechanical properDes:
1x̂
2x̂r̂θ̂
θ
Transversely isotropic with axial direc2on in the radial direc2ons
=
6
5
4
3
2
1
66362616
5545
4544
36332313
26232212
16131211
6
5
4
3
2
1
222
)(00)()()(0)()(0000)()(000)(00)()()()(00)()()()(00)()()(
ε
ε
ε
ε
ε
ε
θθθθ
θθ
θθ
θθθθ
θθθθ
θθθθ
σ
σ
σ
σ
σ
σ
CCCCCCCC
CCCCCCCCCCCC
For plane strain problem: 0543 === εεε
• Apply a poten2al across the fuzzy fiber to get its piezoresis2ve response. Effec2ve resistance is obtained by building energy equivalence, which can be used to compare with experimental results.
In‐Plane Bulk Tension Test of Fuzzy Fiber with Piezoresis2ve Effect in the Interphase
In‐plane bulk tension test: %1%1.0 −=ε
410=rrg 0=θθg0RRΔ
ε
Gauge factor: 4≈
ΔΦ
L=2r
)( effRWW =
Nanoscale RVE
CNT θ̂
r̂
0=θrg
It is found that if the macroscale gauge factor is on the scale of experimental result, a very large internal piezoresis2ve strain coefficient (grr = 104) of CNT is needed.
Energy equivalence:
Effec2ve resistance
Click here
(Unit: ) m•Ω
Fuzzy Fiber Conclusions • A single scale finite element framework is built to model the
piezoresistive effects of nanocomposites in the nanoscale, which can capture the internal piezoresistivities of CNTs, and provide information for upper scales.
• The macroscale piezoresistive response of nanocomposites due to
micro- and nanoscale features can be modeled by using a multiscale algorithm, which can overcome the meshing of every CNT to save great computaDonal Dme.
• It is found in order to match the experimental data of piezoresisDve respond of
the macroscale material, a very large piezoresisDve strain coefficient is needed for CNTs, which implies the piezoresisDvity of nanocomposites mainly comes from dynamic nanotube network effects of electron hopping and nanotube contact.
Modeling effec2ve damping proper2es of fuzzy fiber‐reinforced polymer composite: Long Term Task Objec3ves
Develop a mulDscale model to characterize the effecDve damping property of fuzzy fibers and fuzzy fiber‐reinforced composites
InvesDgaDng the overall viscoelasDc properDes of the composite aaer inserDng various kinds of nano parDcles. InvesDgaDng the overall properDes as a funcDon of frequency, temperature and volume fracDon of the fiber and CNTs.
Doing experiments including harmonic stress‐strain tests and vibraDon tests to validate the model
Building an effecDve damping matrix for the macro scale composite to use it for transient dynamic analysis of arbitrary structures made up of this composite material (CollaboraDon with Dr. JN Reddy)
Advisors: Daniel J. Inman, Gary D. Seidel Student: Mohammad Bonakdar
Short Term finished tasks�
�
• Damping characterizaDon of viscoelasDc composites using micromechanics
• Effect of interphase on damping properDes of viscoelasDc nanocomposites with spherical parDcles
• Performing vibraDon tests to obtain material damping • Observing nonlinear behavior in CNT‐nanocomposites • Finite element analysis of damped viscoelasDc structures using GHM* method
• Student exchange between Virginia Tech and Texas A&M to learn techniques for making CNT nanocomposites.
*Golla‐Hughes McTavish method which curve fits experimental data and adds degrees of freedom producing a linear Dme invariant damping matrix
Damping characteriza2on of viscoelas2c composites using micromechanics
Proc. SPIE 7978, 797810 (2011); doi:10.1117/12.880481
Micromechanics (Mori‐Tanaka method) combined with the correspondence principle of viscoelasDcity are used to obtain the effecDve damping properDes of viscoelasDc composites
Spherical parDcles
Rod like parDcles
• Both matrix phase (eg. Epoxy) and the parDcle phase (eg. CNT or carbon fiber or fuzzy fiber) may be considered as viscoelasDc or elasDc.
• Different parDcle shapes (spherical, rod, fiber) could be modeled.
• ParDcles may be unidirecDonal or randomly oriented which is the case for CNT‐Epoxy nanocomposite.
10-6 10-4 10-2 100 102 1040
0.5
1
1.5
freq (Hz)η
Epoxy Matrix30% PC50% PC70% PC
10-6 10-4 10-2 100 102 1040
0.5
1
1.5
2
2.5
3
3.5
4
freq (Hz)
η
PC Matrix30% Epoxy50% Epoxy70% Epoxy
The procedure starts from the relaxaDon funcDon of the consDtuent materials (obtained from DMA). Fisng a Prony series we find the relaxaDon spectrum of the material which is all we need for characterizaDon of the viscoelasDc material
!
E( t) = E" + Ei exp #t$ i
%
& '
(
) *
i=1
N
+
Using this method we can find the frequency dependent effecDve damping of the composite Keypoint: the effec3ve proper3es highly depend on which material serves as the matrix and which one serves as the par3cle.
2‐phase viscoelas2c composite with spherical par2cles
Effect of interphase on damping proper2es of viscoelas2c nanocomposites
Presented at ASME McMat, May, June 2011, Chicago, IL
In nanocomposites an interphase layer is formed around the nanoparDcles which has different properDes than the parDcle and the matrix. This interphase layer can considerably affect the effecDve damping properDes of the composite. This model is useful in finding the effect of coated parDcles in the composite.
matrix
interphase
parDcle
The composite sphere model is combined with the correspondence principle of viscoelasDcity to find the effecDve complex bulk modulus of the composite, which yields the overall damping.
10-10 10-8 10-6 10-4 10-2 100 102 104101
102
103
104
105
time (sec)
Bulk
Relax
ation
func
tion
(MPa
)
ParticleInterphase1Interphase2Interphase3Interphase4Matrix
The interphase layer properDes are assumed to be changing radialy from parDcle to matrix. In this model we descreDzed the interphase layer and interpolated the relaxaDon funcDon between that of the parDcle and matrix.
10-5 100 1050
0.2
0.4
0.6
0.8
1
1.2
1.4β = 1
freq (Hz)
η
vf = 0.05vf = 0.15vf = 0.30
Keypoint: In case of elasDc reinforcements in viscoelasDc matrix, a decrease in the overall damping will happen.
Composite cylinder model (CCM) for the fuzzy fiber composite
Matrix phase (Epoxy)
Radially oriented CNT phase
Glass fiber phase
The composite cylinder model is the last step in finding the effecDve viscoelasDc properDes of the fuzzy fiber‐epoxy composite.
Observing nonlinear behavior in CNT‐nanocomposites
• Neat epoxy behaves linearly.
• Adding 0.3 wt% SWNT to the same epoxy results in nonlinear behavior, i.e., loss factor changes with amplitude of moDon.
• Also the SWNT reduces the damping by a small amount.
Loss factor of neat epoxy for 2 different amplitudes (from DMA)
Loss factor of 0.3 wt% SWNT‐epoxy composite for 2 different amplitudes (from DMA)
Finite element analysis of damped viscoelas2c structures using GHM method
10
100
1000
10000
1.E‐17 1.E‐11 1.E‐05 1.E+01 1.E+07 1.E+13
E' (M
Pa)
freq (Hz)
60 degC
100 deg C
150 deg C
Fit parameters
Modified sDffness and damping matrices sensiDve to frequency of loading for different temperatures
Storage modulus of CNT‐epoxy nanocomposite at different temperatures obtained by DMA
The GHM formulaDon is capable of bringing the frequency dependent sDffness and damping properDes into the finite element formulaDon. This method could be used for predicDng the vibraDon and damping of large structures made of viscoelasDc materials which could not be directly tested.
Finite element analysis of damped viscoelas2c structures using GHM method
Here the vibraDon of a fixed viscoelasDc beam made of CNT‐epoxy at 3 different temperature (below glass transiDon, about glass transiDon and above glass transiDon) is invesDgated.
T=60 T=100
T=150
Below Tg material is glassy with high sDffness and low damping
At Tg material has largest energy absorpDon capacity hence the vibraDon is overdamped.
Above Tg material is in rubbery phase, with low sDffness and damping resulDng in low frequency oscillaDons.
Performing vibra2on tests to obtain structural damping
• Forced or free vibraDon experiments could be used as a method to obtain the damping capacity of structures.
• Despite DMA that is used for small samples of materials, vibraDon tests do not have a limitaDon on the size of the structure.
• In addiDon to material damping, vibraDons reveals the effects of the structure geometry on the sDffness and damping.
Using the vibraDon test we can obtain the loss factors at specific resonance frequencies of the structure
CNT‐Epoxy beam Provided by TX A&M
Carbon fabric‐matrimid composite plate
Provided by TX A&M
Vibra2on proper2es of Func2onally Graded Hybrid Composites
Max Phase Metal/Ceramic
Vascular Healing and Cooling Material
Hi Damping Layer CNT/ Fuzzy Fibers
Sensing Layer (Piezoelectric)
Inman
Titanium/SMA
Nominal Values
Sample Frequency Response
Effects of Layer Thickness on Frequency
Summary of Key Accomplishments
• New hystereDc model capable of predicDng response with potenDal for FEM use
• ComputaDonal modeling piezoresisDve response of fuzzy fiber nanocomposites induced by internal piezoresisDvity of CNTs.
• Damping modeling of fuzzy fiber nanocomposites potenDal for FEM use
• VibraDon model of hybrid system for frequency/thickness analysis
Year 3 Plan Summary • MAX Phase Materials
– Develop physics based model for high temperature behavior – Implement in FEM to describe rate behavior at high temperatures. – Develop experimental protocol to determine the high strain rate response
of newly synthesized bulk, porous and composite MAX phase materials. – Combine temperature and frequency hysteresis
• Fuzzy fibers – InvesDgate electron hopping – InvesDgate the effect of network formaDon – TesDng – Pass informaDon on response up to the higher length to MURI group
• Nanocomposites – Introduce damage models – TesDng – invesDgate the effect of CNTs concentraDon on the damping – Augment GHM damping model with two fits
• Vibra2on – Flow effects on dynamic response of vascular layer
PublicaDons Since Last Review 1 • N. C. Goulbourne and R. Bha;acharya, "High strain rate characterizaDon of Ti2AlC", in
preparaDon, 2011. • R. Bha;acharya and N.C. Goulbourne, "A fracDonal calculus approach for modeling hysteresis
in MAX phase materials", in preparaDon, 2011. • Bonakdar, M., Seidel, G. D., and Inman, D.J., 2011, “Damping IdenDficaDon of ViscoelasDc
Composites using Micromechanical Approaches”, SPIE Conference on Smart Materials and Structures/NDE, 6 ‐ 10 March, San Diego, California, paper number 7978‐48.
• Bonakdar, M., Seidel, G. D., and Inman, D.J., “Effect of interphase on damping properDes of viscoelasDc nanocomposites”. 2011ASME McMat, May, June 2011, Chicago, IL
• G.D. Seidel, A.‐S. Puydupin‐Jamin, “Analysis of clustering, interphase region, and orientaDon effects on the electrical conducDvity of carbon nanotube–polymer nanocomposites via computaDonal micromechanics”, Mechanics of Materials, Volume 43, Issue 12, December 2011, Pages 755‐774
• Xiang Ren and G.D. Seidel, "AnalyDc and computaDonal mulD‐scale micromechanics models for mechanical and electrical properDes of fuzzy fiber composites“, Proceedings Paper for the 52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, Denver, Colorado, USA, 4 ‐ 7 April, 2011(AIAA 2011‐1923)
• George Chatzigeorgiou, Gary Don Seidel, Dimitris C. Lagouda, "EffecDve mechanical properDes of “fuzzy fiber” composites" to be submi;ed to Composites Part B: Engineering
• Xiang Ren and Gary D. Seidel, "Modeling of Inherent PiezoresisDvity. of Carbon Nanotubes on the EffecDve PiezoresisDvity of Polymer”
PublicaDons Since Last Review 2 • Nanocomposites", to be submi;ed to ASME Journal of Applied Mechanics (by end of January) • Gary D. Seidel, "MulDscale Modeling of Mechanical, Thermal, and Electrical ProperDes of Carbon
Nanotube‐Polymer Nanocomposites" Invited Talk at CENTRO DE INVESTIGACION CIENTIFICA DE YUCATAN (CICY) as part of SEMINARIO DE LA UNIDAD DE MATERIALES (Materials Division Seminar Series), Merida, Mexico, 20‐23 June, 2011.
• Mohammad Bonakdar, Gary D. Seidel, Daniel J. Inman, "Effect of Interphase on damping properDes of viscoelasDc nanocomposites", Presented at ASME 2011 Applied Mechanics and Materials Division Conference (McMAT), 30 May ‐ June 1, 2011.
• Xiang Ren, Gary D. Seidel, Skylar Stephens, "AnalyDc and ComputaDonal Micromechanics Models for Mechanical and PiezoresisDve ProperDes of the Nanocomposite Interphase of the Fuzzy Fiber Material", Presented at ASME 2011 Applied Mechanics and Materials Division Conference (McMAT), 30 May ‐ June 1, 2011.
• Xiang Ren and G.D. Seidel "AnalyDc and computaDonal mulD‐scale micromechanics models for mechanical and electrical properDes of fuzzy fiber composites" 52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference Denver, Colorado, USA 4 ‐ 7 April, 2011 (AIAA 2011‐1923)
• Mohammad Bonakdar, G.D. Seidel, and D.J. Inman "Damping characterizaDon of viscoelasDc composites using micromechanical approach" 2011 SPIE Smart Structures/NDE Conference San Diego, California, USA 6‐10 March, 2011 [7978‐48]
• Xiang Ren and G.D. Seidel, "MulDscale Modeling of the ElasDc ProperDes of Fuzzy Fibers", ASME 2010 InternaDonal Mechanical Engineering Congress and ExposiDon, Track 12: Mechanics of Solids, Structures, and Fluids, Topic 12‐17: MulDfuncDonal and Nanostructured Materials: Modeling and CharacterizaDon, Session 12‐17‐3: MulDfuncDonal and Nanostructured Materials III Vancouver, BriDsh Columbia, Canada 12 ‐18 November 2010