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)