Toughening mechanisms in nanoparticle-modified epoxy polymers
Author(s)
Type
Thesis
Abstract
The present work investigates the ability of several different epoxies to be toughened
with the addition with 20 nm silica nanoparticles (nanosilica). The formation of ‘hybrid’
epoxy polymers, containing both silica nanoparticles and carboxyl-terminated
butadiene-acrylonitrile (CTBN) rubber micro-particles, is also discussed. The
structure/property relationships are considered, with an emphasis on the toughness
and the toughening mechanisms. Particular attention was given to an anhydride cured
diglycidyl ether of bisphenol-A (DGEBA) system where the fracture energy increased
from 83 to 204 J/m2 with the addition of 20 wt. % of silica nanoparticles. Plastic shear
bands followed by debonding of the matrix from the silica nanoparticles, and
subsequently plastic void growth of the epoxy were found to be the operative
toughening mechanisms. The largest increases in toughness observed were for the
‘hybrid’ materials where a synergistic behaviour on the fracture energy. A maximum
fracture energy of 1051 J/m2 was measured for a ‘hybrid’ epoxy polymer containing 10
wt. % silica nanoparticles and 9 wt. % rubber micro-particles. The toughening
mechanisms for such systems were postulated to be rubber-particle cavitation, shear
band yielding and void growth and debonding and plastic void growth of the nanosilica
necklaces.
Ultimately, these polymers are intended to be used as matrices in fibre-reinforced
composites. Therefore, resistance to delamination as fibre-composites has been
examined for such modified epoxies. The interlaminar fracture energies for the fibrecomposite
materials were found to increase even further by a fibre bridging toughening
mechanism. However, the fibre-matrix adhesion is shown to be an important
parameter.
The present work has extended an existing model to predict the toughening effect of
the nanoparticles in the epoxy polymer. There was excellent agreement between the
predictions and the experimental data for epoxy containing the silica nanoparticles, and
for epoxy polymers containing rubber or coreshell particles. Inferences have been
made about the toughenability of the epoxy being sensitive to particle-matrix adhesion
and the ability for the matrix to shear yield.
with the addition with 20 nm silica nanoparticles (nanosilica). The formation of ‘hybrid’
epoxy polymers, containing both silica nanoparticles and carboxyl-terminated
butadiene-acrylonitrile (CTBN) rubber micro-particles, is also discussed. The
structure/property relationships are considered, with an emphasis on the toughness
and the toughening mechanisms. Particular attention was given to an anhydride cured
diglycidyl ether of bisphenol-A (DGEBA) system where the fracture energy increased
from 83 to 204 J/m2 with the addition of 20 wt. % of silica nanoparticles. Plastic shear
bands followed by debonding of the matrix from the silica nanoparticles, and
subsequently plastic void growth of the epoxy were found to be the operative
toughening mechanisms. The largest increases in toughness observed were for the
‘hybrid’ materials where a synergistic behaviour on the fracture energy. A maximum
fracture energy of 1051 J/m2 was measured for a ‘hybrid’ epoxy polymer containing 10
wt. % silica nanoparticles and 9 wt. % rubber micro-particles. The toughening
mechanisms for such systems were postulated to be rubber-particle cavitation, shear
band yielding and void growth and debonding and plastic void growth of the nanosilica
necklaces.
Ultimately, these polymers are intended to be used as matrices in fibre-reinforced
composites. Therefore, resistance to delamination as fibre-composites has been
examined for such modified epoxies. The interlaminar fracture energies for the fibrecomposite
materials were found to increase even further by a fibre bridging toughening
mechanism. However, the fibre-matrix adhesion is shown to be an important
parameter.
The present work has extended an existing model to predict the toughening effect of
the nanoparticles in the epoxy polymer. There was excellent agreement between the
predictions and the experimental data for epoxy containing the silica nanoparticles, and
for epoxy polymers containing rubber or coreshell particles. Inferences have been
made about the toughenability of the epoxy being sensitive to particle-matrix adhesion
and the ability for the matrix to shear yield.
Date Issued
2008
Date Awarded
2010-07
Citation
2008, pp.010.5-
Publisher
Elsevier
Start Page
010.5
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Kinloch, AJ
Taylor, Ambrose
Sponsor
EPSRC
Creator
Masania, Kunal
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Source
5th International Conference on Fracture of Polymers, Composites and Adhesives
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)
Start Date
2008-09-07
Finish Date
2008-09-11
Coverage Spatial
Les Diablerets, Switzerland