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Viscoelastic Properties of Nanocomposites
Jacopo Ciambella
www.bris.ac.uk/composites
5th ANNUAL CONFERENCE ACCIS
7th September 2012
2/10Why Viscoelastic Materials?
Elastic Viscoelastic Viscoplastic
Energy dissipation capabilities, i.e., damping, of viscoelastic materials are crucial in all those applications where structures are subjected to cyclic loading
Viscoelastic Properties of Nanocomposites
3/10Research Objectives
Viscoelastic Properties of Nanocomposites
NATURAL RUBBER + NANOFILLERS
Carbon Black Graphene
New compounds with enhanced damping properties, multifunctionality
Research Group
ACCISDr J. CiambellaDr S. Rahatekar
School of ChemistryDr A. PatilProf S. Mann
ACCIS DTCD. Stanier (PhD student)XP Project: “Graphene/Elastomer Nanocomposites for Applications in Pneumatic Tyres “
4/10Background
1.Constitutive Modelling
1.Experiments1.Numerical Simulations
Viscoelastic Properties of Nanocomposites
• From February 2012
– Lecturer in Composites Engineering @ ACCIS
• Mechanical Characterization of Carbon Black-Filled Rubber
5/10Background
Results: Model the hysteresis losses during finite deformations of the material
Characteristic frequencyof the deformation due to rolling
10 – 100 Hz
Characteristic frequencyof the deformation due to road roughness
104 – 106 Hz
Low Tan δ at the characteristic frequency
Decrease Rolling Resistance
High Tan δ at the characteristic frequency
Increase Wet Grip
OP
PO
SIT
E R
EQ
UIR
EM
EN
TS
Remark: Need of a constitutive equation able to describe the large strain behaviour for selecting the optimal material/structural configuration
Viscoelastic Properties of Nanocomposites
6/10The ABAQUS Model of Finite Viscoelasticity
Some shortcomings were highlighted and a new viscoelastic formulation was proposed. After this work, the ABAQUS model was changed (from Abaqus 6.9).
Viscoelastic Properties of Nanocomposites
Large strain viscoelasticity
Configuration at time s Configuration at time t
Ciambella J., Destrade M., and Ogden R. W., 2009, “On the ABAQUS FEA model of finite viscoelasticity,” Rubber Chemistry and Technology, 82(2), pp. 184–193.
7/10Polymer Nanocomposites
Viscoelastic Properties of Nanocomposites
Carbon Black (CB) Graphene / Graphene Oxide (GO)
• Easy to process
• Inexpensive
• Good thermal properties
• Good electrical properties
• High mechanical strength
• Large interfacial area could lead to increased dissipation properties
• Graphene membrane only one atom thick is impermeable to standard gases
• Excellent electrical properties also at very low volume fraction
• Functional groups similar to elastomeric polymer can be grafted on the graphene surface
8/10
0 2 4 6 8 10 12 14 160
200
400
600
800
1000
1200
1400
Preliminary Experimental Results
Viscoelastic Properties of Nanocomposites
Dynamic Tests
NR
NR+GO (0.25phr)
NR+GO (0.50phr)
Frequency (Hz)
Storage M
odulus (kPa)
Material G'@5Hz Perc. Var.
NR 800 kPa -
NR+GO (0.25phr) 956 kPa +19.5%
NR+GO (0.50phr) 1082 kPa +35.2%
Increased stiffness
Better Dry Handling
9/10
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Preliminary Experimental Results
Viscoelastic Properties of Nanocomposites
Fatigue Tests
NR
NR+GO (0.25 phr)
Tensile Strain
Tensile S
tress (MP
a)
Material εmin
@ 50th cycle εmax
@ 50th cycle
NR 0.56 0.80
NR+GO (0.25phr) 0.25 0.38
-55 % -52 %
Huge increase in Fatigue
Resistance
August 2012
10/10Conclusions and Further Developments
Viscoelastic Properties of Nanocomposites
Conclusions• A natural rubber compound reinforced with GO has been produced
• Preliminary results on fatigue tests show a massive increase in fatigue resistance
• The introduction of GO increases both storage and loss moduli
• Larger GO content
• DMA tests at higher frequencies
• Measure the conductivity of the GO filled rubber during deformation
• Rubber vulcanisation (addition of sulphur based curatives)
Further Developments
AcknowledgementsACCIS Doctoral Training Centre for supporting the Extended Project:“Graphene/Elastomer Nanocomposites for Applications in Pneumatic Tyres”
