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MULTIFUNCTIONAL MATERIALS: SHOCK,
DURABILITY AND BLAST RESISTANCE
PROFESSOR DAVID HUI
UNIVERSITY OF NEW ORLEANS
OUTLINE� Background
� University of New Orleans (UNO) work relates to developing threefunctional properties in composite materials: (1) Energy absorption (2) blast protection and (3) durability
� UNO applied nanotechnology-based solutions through the utilization of nanomaterials that dissipate a substantial fraction of the shock/blast energy that is received
� We analyzed the mechanisms
� Experiments with nano-particle filled composites in linear impact (Hopkinson Bar)
� Experimented with CNT reinforced damping (Vibration)
� Applied holography and laser vibrometry for experimental records
� We have proven nanoparticle-based energy absorption technology
� Energy absorption was achieved by providing large energy sink by sources for friction and slip-stick motion at interfaces of matrix and nanoparticle.
BACKGROUND OF UNO’S NANO-PARTICLE
BASED COMPOSITES RESEARCH FOR NAVY
WHAT US NAVY WANTSFOR THE SHIPS?
�Lighter
�Stronger
�Faster
The above are the three mantras for the Navy’s R&D search for new materials
NEW MATEIALS SHOULD ENABLE THE NAVY TO HAVE SHIPS
Quickly deployable
Carry Larger Payloads
Survive threats in high seas
These would be possible if materials with
specific property improvements are introduced
Navy’s new materials of the future
NANO-COMPOSITESIn all their varieties as
Smart
Adaptive
Multifuctional
Etc
Etc
MULTIFUNCTIONAL MATERIALS
NAVY IS CHANGINGNEW TECHNOLOGIES FOR NAVY
ALL VARIETIES OF COMPOSITES Smart, Adaptive, Nano,
Multifunctional, Graded
FRICTION STIR WELDING Avoids HAZ
NEW HULL DESIGNS Advanced composite Double Hull
(1998)
Double M Hull (2004)
NEW JOINT DESIGNS Composite to Metal
Technology show caseSwedish all-composite STEALTH ship – First in the world
Max length possible with today’s technology : 209 ft
Ships longer than 400 ft can not be built with composites
Because of lower stiffness
New ship double hull concept
New hybrid hull concept
The bow and stern made of
Composite, the mid part stainless steel
Metal-composite jointing
is in issue
TECHNICAL DISCUSSIONS-BASICS-
SOLID IMPACT ON A MULTI-LAYERED SOLID MEDIA
1 dimensional problem :
vFORCE F = PA
S
IMPACTOR VELOCITY = V
IMPACT ENERGY = 0.5MV2
IF IMPACTOR IS CYLINDRICAL SOLID
AND GAS PROPELLED, THEN
IMPACT ENERGY = PAS
WHERE
P = PRESSURE
A = AREA
Particle velocity = v
Stress Pulse Energy = ����cv
(unidirectional stress wave propagation theory)
where:
���� = Density
v = particle velocity
c = stress wave velocity = (E/����)0.5
E = Young’s modulus
V
F1
t1 t2
F2Note: Transformation of energy from low amplitude
force to high amplitude force to cause damageF 2 >> F1
t 2 << t 1
t t
IMPULSE = F1 t 1 = F2 t 2
IMPACT ---BASICS
F1
t1 t2
F2Note: Transformation of energy from low amplitude
force to high amplitude force to cause damageF 2 >> F1
t 2 << t 1
t t
IMPULSE = F1 t 1 = F2 t 2
ENERGY OF THE IMPACTOR = (1/2)MV2
ENERGY OF STRESS WAVE = [A/(����C)]
(1/2)MV2 = [A/(����C)]
The trick to make a structure to survive impact is to make the high
amplitude F2 (stress) transform to low amplitude F1 so that the
material’s strength is not exceeded. Modifying materials by using
nanotechnology achieves it by dispersing the stress wave
amplitude very rapidly
Multiple Impedance Pressure Bar (MIPB)
PC brassAL steel
Light Gas
Pressure
Steel
Strike
r
SG SG SG SG
MULTILAYER WAVE PROPAGATION – Increased Number
Of Interfaces Cause Decrease in Propagating Stress Amplitude
Impedance Z = ρc/g
SG = Strain Gage
Dutta-Tech
Materials of different impedences
Multiple layer shock propagation problem
DUTTA HYPOTHESISFOR IMPEDANCE GRADIENT WHICH CONSIDERS
INFINITE NUMBER OF LAYERS
No Interfaces
Multiple Plate
Impedance MismatchedBarrier/Armor
Impedance
gradedBarrier/Armor
Interface
Damage
No Interfaces
Multiple Plate
Impedance MismatchedBarrier/Armor
Impedance
gradedBarrier/Armor
Interface
Damage
No Interfaces
Multiple Plate
Impedance MismatchedBarrier/Armor
Impedance
gradedBarrier/Armor
Interface
Damage
Dutta-Tech
Impedance Effect Processing Model from Hopkinson Bar Test Data
Stress waveforms in incident bar - test MIX-5B-Direct
-8000
-6000
-4000
-2000
0
2000
4000
6000
0 2000 4000 6000 8000 10000 12000 14000
Time (Seconds)
Str
ess (psi)
Energy: stress square- t curve MIX 5B-Direct
-10000000
0
10000000
20000000
30000000
40000000
50000000
0 2000 4000 6000 8000 10000 12000 14000
time (seconds)
sig
ma s
quare
(psi
2)
Transmitted stress wave
MIX 5B
-8000-6000-4000-2000
0200040006000
0 2000 4000 6000 8000 10000 12000 14000
Time (seconds)
Str
ess (psi)
Energy: stress square - t curve Mix 5B-Direct
-10000000
0
10000000
20000000
30000000
40000000
50000000
0 2000 4000 6000 8000 10000 12000 14000
Time (Seconds)
Sig
ma s
quare
(psi
2)
Evaluate Attenuation by comparing wave amplitude
And wave energy in incident and in transmitted bar after
The wave has passed through the designed IMG material
INCIDENT WAVE AMPLITUDE INCIDENT WAVE ENERGY
TRANSMITTED WAVE AMPLITUDE TRANSMITTED WAVE ENERGY
S(in)S(in)
Sin (t)
Amplitude Attenuation : S(t)/S(in) = 53% Energy Attenuation : S(t)/S(in) = 28%
U EnergyAc
Edt
t
( ) = ∫σ2
0
Energy content of a stress wave pulse:
Where A is the rod area, c is the wave velocity
E is the Young’s modulus, sigma is stress, and t is time
Dutta-Tech
Nano-technology based energy absorption/damping
(After R.S.Lakes, Viscoelastic Solids, Boca Raton, FL, CRC Press)
WHY NANO-COMPOSITES?
Look at the Problems of Traditional Ship CarbonSteels:
Corrosion
Thermal and Electromagnetic Signature
Construction by framing and sheathing and
welding numerous parts with 100 yrs old designs
Labor intensive
Numerous Heat Affected Zones (HAZ) stress concentration
HAZ’s readily corrdes and fail in fatigue
Extensive coating is required
Result: Higher building and maintenance costs
WHY NANO-COMPOSITES?
Advantages with NANO-Composites:
• Higher strength-to-weight ratio
• Lower Magnetic Signature
• Lower Acoustic Signature
• Lower Hydrodynamic Signature
• Lower Thermal Signature
• Lower Radar Signature
• Lower maintenance cost
• Parts consolidation in fabrication
• Fatigue resistance and durable
AND NOW NANO WILL MAKE THE MATERIALS MORE BLAST AND SHOCK RESISTANT•
LINEAR IMPACT STUDY OF A NANOCOMPOSITE IN
HOPKINSON BAR
OBJECTIVE
Multi-walled carbon nanotube (MWCNT) in a
polymer is believed to modify the energy absorbing
haracteristics of the resulting nano polymer
composites.
Our objective here is to find out the efffects of
MWCNT contents on the dynamic mechanical
properties, including energy absorption
characteristics of the resulting Polymer
Nano-composites.
Materials
The materials were Fabricated at Univ of Mississippi
Fabrication
1. Mix different percentages of MWCNT in Nylon 6,6
2. Mold into a panel
3. Cure
4. Cut to lengths
Test Materials
Samples:
Hopkinson Bar Apparatus
Bars
Sample
Strain wave records from the two bars
Governing Equations
∫=
t
dtCu0
101 ε
∫=
t
dtCu0
202 ε
∫=
t
dtCu0
101 ε
∫=
t
dtCu0
202 ε
∫=
t
dtCu0
101 ε Avg strain in the specimen =
Avg stress in the specimen =
Avg strain rate in the specimen =
L = Specimen length
Energy Absorbed =
Results: Effects on peak stressand Energy Absorption
Samples - permanent deformation
STRAIN RATE = SLOPE
STRESS-STRAIN PLOTS
Effects of MWCNT % on the modulus (stress-strain slope)
0% 10%5%
Effect on Energy Absorption
0% 5% 10%
CONCLUSIONS
� MWCNT Nylon composites are extremely tough. They did not completely fracture under dynamic peak stress of 170 MPa. Internal Damage Predicted from permanent dimensional change.
� Modes of failure need to be confirmed by SEM
� MWCNT modified strength, stiffness and energy absorption. Only after smaller addition the properties improved significantly (20% approx). The reasons are being investigated.
� Nylon is thermoplastic and energy absorbent. Additional work needed with thermoset composites
VIBRATIONAL ENERGY ABSORPTION STUDY IN CNT-FRP COMPOSITES
Nano-particle-reinforced energy
absorption:
� It involves placement of numerous nano particles
�During impact nanoparticles interact with internal matrix and with one another and thus dissipate energy through momentum transfer and friction
Parameters controlling energy absorption in these materials
� Particle size
� Dispersion in matrix
� Shape
� Density
� Texture
� Coefficient of restitution
� Coefficient of friction
� Surface area and conditions
� Free space around the particles
� Strain rate
Example of a typical syntactic foam composite material with a relatively low volume fill of micro-spheres. The sphere “ringed” is approximately
50µµµµm
Microstructure of filled composite materials
syntactic foam
composite material
representative volume
hydrostatic pressure load
shear load
homogenous material
K and G
Mechanisms of shock and blast
energy dissipation
Principle of homogenisation method for syntactic foam composite materials
Dispersion of lightweight spherical fillers
5 wt.% SiO 10nm nanospheres (2000x)Fractured surface of 5 wt.% SiO 1µm (2000x)30 wt.% SiO 120µm microspheres (500x)
5 wt.% SiO 10nm nanospheres ( Optic. 50x)
5 wt.% SiO 10nm nanospheres (20000x)5 wt.% SiO 1µm mesospheres (8000x)
5 wt.% SiO 1µm mesospheres (Optic. 50x)30 wt.% SiO 120µm microspheres (Optic. 50x)
Fractured surface of SiO microspheres (700x)
Better dispersion
of nanofillers
Properties of interphase layer
Approaches to control the interphase layer
� Chemical dispersant / surfactant to achieve dispersion and effective thickness of the layer
� Electrostatic ultrasound treatment
� High shear force mixing to prevent agglomeration of nanoparticulates
Effective thickness of interphase
layer
30nm thickness of interphase layer50-80 vol.%
concentration of nanoparticles
100nm thickness of interphase
layer10-30 vol.%
concentration of nanoparticles
Single-walled nanotube-epoxy composite
Computationally performed Pull out test
Composite Materials, Experimental
� Samples manufactured manually by meltmixing nanotubes and polymer by extrusion process
� Investigated the effects of different orientations of carbon nanotubes (CNT)
� Applied multiple stress rates
� Viewed results by holography technique
� High strain rate was produced by Bruel and Kjaer (B&K) vibration system
� Energy absorption capacity was measured by damping capacity measurements
� CNT orientations were controlled by extrusion rate
� We measured : frequencies, mode shapes, and damping at each mode by
the B&K laser vibrometry
Nanotube-FRP Experimental (Contd)
Computer System
Laser vibrometer
Clamped Sample
Electro-dynamic exciter
1125
1045
1136
866828
772740 726 740
300
1150
1210
10801060
1030 10101050
990
930
790
730750
730690
0
200
400
600
800
1000
1200
1400
IP 2
90
epox
y V
erifl
ex
40 w
t.% S
iO, 5
00µm
20 w
t.% N
i-coa
ted,
120
µm
30 w
t.% N
i-coa
ted,
120
µm
20 w
t.% V
S5500
, 100
µm
40 w
t.% V
S5500
, 100
µm
20 w
t.% D
32, 1
20µm
40 w
t.% D
32, 1
20µm
2 w
t.% E
xpan
cel,
10-4
0µm
5 w
t.% S
iO 1
-5µm
10 w
t.% S
iO 1
-5µm
2.5
wt.%
SiC
50n
m
5 w
t.% S
iC 5
0nm
2.5
wt.%
SiO
15n
m
5 w
t.% S
iO 1
5nm
2.5
wt.%
SiO
10n
m
5 w
t.% S
iO 1
0nm
7 w
t.% S
iO 1
0nm
2 w
t.% m
esoS
iO, 8
nm p
ore
2 w
t.% m
esoS
iO, 4
nm p
ore
2 w
t.% m
esoA
lSi,
8nm
por
e
2 w
t.% C
NT 1
00nm
5 w
t.% C
NT 1
00nm
De
nsity,
kg
/m3
(T
em
p.=
25
C)
Density (weight) of foam composites
Pure
epoxyMesoscale
Carbon
NanotubesMicroscale Nanoscale
01/03/2010© The University of Sheffield /
Research Office
0.02
0.30.26
0.32
0.27
0.38
0.32
0.4
0.35
0.25
0.45
0.4
0.350.38
0.41
0.48
0.8
1
0.9
0.950.98
0.83
0.65
0.55
0
0.2
0.4
0.6
0.8
1
1.2
IP 2
90
epox
y V
erifl
ex
40 w
t.% S
iO, 5
00µm
20 w
t.% N
i-coa
ted,
120
µm
30 w
t.% N
i-coa
ted,
120
µm
20 w
t.% V
S5500
, 100
µm
40 w
t.% V
S5500
, 100
µm
20 w
t.% D
32, 1
20µm
40 w
t.% D
32, 1
20µm
2 w
t.% E
xpan
cel,
10-4
0µm
5 w
t.% S
iO 1
-5µm
10 w
t.% S
iO 1
-5µm
2.5
wt.%
SiC
50n
m
5 w
t.% S
iC 5
0nm
2.5
wt.%
SiO
15n
m
5 w
t.% S
iO 1
5nm
2.5
wt.%
SiO
10n
m
5 w
t.% S
iO 1
0nm
7 w
t.% S
iO 1
0nm
2 w
t.% m
esoS
iO, 8
nm p
ore
2 w
t.% m
esoS
iO, 4
nm p
ore
2 w
t.% m
esoA
lSi,
8nm
por
e
2 w
t.% C
NT 1
00nm
5 w
t.% C
NT 1
00nm
Lo
ss f
acto
r, t
an
δ (
Te
mp
.=1
10
C)
Energy dissipation properties of foams at elevated temperature
Pure
Epoxy
Resin
Mesoscale
Carbon
NanotubesMicroscale Nanoscale
BOUNDARY MESHLESS FORMULATION FOR
DEFORMATION OF SOLIDS 45
____ SWCNT + polymer A
- - - MWCNT + polymer A
············ CNT+ polymer B
· - · - · CNT+ polymer A +
ceramics
106
107
108
109
Mo
du
lus (
Pa
)
0 20 40 60 80 100 1200
0.2
0.4
0.6
Tem perature (°C)
Lo
ss fa
cto
r
A + glass
A + poly
B + glass + poly
B + poly
Mechanical and damping and Properties at 10 Hz: 5wt% CNT-reinforced balloon-
based foams. The peak damping occurs around 100°°°°C for CNT-reinforced
polymer balloon-based syntactic
Damping prediction
Strength of Syntactic Foams
Shock resistance of foam composite materials
� Resonant frequency was determined from the peaks of the frequency response curves
� Each mode shape was the characteristic of the specific NT-FRP
� A finite element model was used to determine displacements and stresses for each orientation of the CNT with respect to loading direction.
Nanotube-FRP Experimental (Contd)
VibrationLoad
VibrationLoad
(a) (b) (c)
Nanoparticle orientation: (a) CNT along the load direction P, (b) chaotic distribution of CNT, and (c) perpendicular CNT to the load direction.
� Modes of vibration of the NT-FRP samples by holography:
Nanotube-FRP Experimental (Contd)
a
d
b c
e f
CNT-reinforced samples, viewed by holography and in color
computer imaging for different CNT orientations:
(a) CNT along the load direction P, (b) chaotic distribution of CNT,
and (c) perpendicular CNT to the load direction
� Frequency was varied from 200 to 4000 Hz
� Twelve natural frequencies were identified
� Signals were noisy below 400 Hz
� Single matrix had better coherence than the CNT-FRP’s
� Variation between tests and finite element prediction of frequencies was within 10%
� Clamping conditions influence variations
Nanotube-FRP Experimental Results
Mode # ω, Polymer
matrix (Hz)
ω, along CNT-
reinforced
polymer (Hz)
%, Diff.
ω, perpendicular
CNT-reinforced
polymer (Hz)
%, Diff.
1 186 112 39,8% 132 29.0%
2 506 254 49.8% 411 18.8%
3 860 544 36.7% 546 36.5%
4 1206 856 29.0% 974 19.2%
5 1,658 1,211 27,0% 1,346 18.8%
6 1,924 1,612 16.2% 1,574 18.2%
7 2,504 2,016 19.5% 2,182 12.9%
8 2,934 2,123 27,6% 2,176 25.8%
9 3,624 3,086 15.1% 3,560 1.8%
10 3,918 3,134 20.0% 3,545 9.5%
Resonance Frequencies Obtained by Laser Vibrometry at Room Temperature
ANALYSIS- Interphase layer model
� Assumption:The dissipated energy, via interfacial movement of
nanotube and polymeric material, is linked with the local cohesion and
adhesion phenomena between the filler/matrix interface.
Consider the equivalent shear force and the differential displacement between tube and matrix (after Koratkar et al 2002, and Odegard
2004)
ηηηη = Loss factor
Udiss = Energy Dissipation
r = radius of nanotube =10-100nm
l2 = length of nanotube
ANALYSIS- Interphase layer model (Contd)
Strain between nanotube and matrix material (����2 ):
Where
R = radius of the representative volume V
G = Shear modulus
E eq = Equivalent modulus of nanotube = 2(l/t)Eg
And
ANALYSIS- Interphase layer model (Contd)
Stress in composite materials is associated with
energy dissipation and is given by:
Comparison of damping behavior
Polymer
matrix
Along CNT-reinforced
polymeric material
Perpendicular CNT-reinforced polymeric
material
Mo
de
Damping
factor, Q
Damping
factor, Q
Increase,
%
Damping
factor, Q
Increase,
%
1-2 339 543 60,2 412 21,5
3-4 811 1402 72,9 1253 54,5
5-6 1193 1616 35,5 1345 12,7
7-8 696 907 30,3 823 18,2
9-
10 1783 2341 31,3 1896 6,3
Nanoindentation of blast-resistant materials
Typical microtomed
nanocomposite samples
mounted on magnetic steel
disks to hold the sample
magnetically.
Polishing of the microtomed
section of sample is not
desireable due to a risk of
particle failure.
Steel disk diameter 15mm.Notes to the rightside figure.
Heating stage used on the
NanoIndenter. Samples are
thin to control the surface
temperature.
Samples are held by springs.
Size of heated plate approx.
Sample preparation for nanoindentation
Several samples mounted on standard stage;
Area 15x15cm; height 0cm - 3cm; weight <10kg
Nanoindentation of multilayered and
nanomaterials at interphase
Nanoindentation at statics
Typical indentation load-displacement
curves for fibre, matrix and the transition
region at a maximum indentation depth of
60 nm
Variation of elastic modulus across the
matrix-interphase-fibre
Source: Jang-Kyo Kim, Man-Lung Sham. Composites, part A 32, 2001. 607 – 618
Surface topography of composite
materials
SiO sphere-filled composite
material sample; polymer
matrix (epoxy) with dispersed
inclusions (lightweight and
stiff hollow SiO spheres) on
left corner, improving blast
resistance of matrix.
Surface Topography at the filler-
matrix interphase point, showing a
step change in mechanical
properties at the interphase;
Nanoindentation results
Modulus Mapping of blast-resistant materials
Prediction of Energy Dissipation at Impact Stress
Impact stress of centrally notched specimen was simulated by MSC.Visual Dytran/LS.Dyna for
Windows XP.
Benefits of filled nanocomposites
1.Contains organically-treated, fillers that disperses evenly
throughout resin.
2.Reinforcement efficiency is achieved at low concentrations (3-
5%) that has a small cost in terms of specific gravity.
3.Stiffness comparable to a 20-30% load of a standard mineral
filled compound.
4.Vibration damping and heat resistance considerably increased
in nanocomposites.
5.Lower loading levels (2-8 wt.%) help maintain resin
transparency.
6.Available for injection molding, extrusion (sheet or film), and
blow molding.
7.Other benefits of nanocomposite include: lower gas
permeability, good surface appearance, dimensional stability,
and lower heat release.
Conclusions and general remarks� NT-FRP show a great promise of energy absorption as clear from
the study of their damping characteristics
� The nano structure in which the polymers tend to form large-
diameter helices around NT favors strong matrix bond
� Depending on orientations the NT increases or decreases the bond strength, fracture strength or damping by 10-20%
� More work is needed to characterize the effects of SWNT, MWNT, Fullerene, BN, or SiC nanotubes, dispersion and orientation effects,
� Multiscale vibration damping modeling needs to be refined
� Both computational and experimental benchmarks need to be improved
Refereed Journal Articles published with
respect to this work
1. M. Kireitseu, G. Tomlinson, D. Hui, L. Bochkareva. Dynamics and Vibration Damping
Behavior of Advanced Meso/Nanoparticle-Reinforced Composites. Journal of Mechanics of
Advanced Materials and Structures, 14(8), 2007, 603-617.
2. M. Kireitseu, D. Hui, G. Tomlinson. Advanced shock-resistant and vibration damping
properties of nanoparticles-reinforced composite material, Jrnl. of Composites Part B 39(1),
2008, 128-138.
3. Lurie S, Hui D, Kireitseu M V, Zubov V, Tomlinson G R, Bochkareva L, Williams R A.
“Computational Mechanics Modelling of Nanoparticle-Reinforced Composite Materials across
the Length Scales”. Int. Journal of Computational Sc. and Engineering, 2 (3-4), 2006, pp.
228-241.
4. M. Kireitseu, V. Kompiš, D. Hui, G. Tomlinson, L. Bochkareva, S. Lurie. Modelling of Strength
of Nanoparticle-Reinforced Materials and their Applications. Jrnl. of Science & Military, 2 (1),
2006, 1-6.
5. D. Hui, M. Kireitseu, G.R. Tomlinson, V. Kompis. Advanced Design Concepts and Modelling
of Composite Materials in Emerging Applications. Advances in Science and Technology, 50,
2006, pp. 124-130.
6. M.V. Kireitseu, D. Hui, K.T. Lau, Viscoelastic behaviour and vibration damping properties of
epoxy based composite filled with coiled carbon nanotubes, Journal of Nanomaterials,
Hundawei Publ. House (submitted, August 2008)