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Influences on nanocomposite structural performance: experimental study on materials processing and bonding

Influences on nanocomposite structural performance: experimental study on materials processing and bonding
Influences on nanocomposite structural performance: experimental study on materials processing and bonding
Nanocomposites have been widely reported to enhance performance in polymers, in both
mechanical and physical properties. An increasing amount of research has resulted in many
nanocomposite polymers being applied to various consumer products from motorcars to golf
balls. Yet, at this time, there are no structural applications despite a large number of reports
claiming improved mechanical properties. Carbon nanotubes are renowned for their specific
mechanical properties as well as their thermal and electrical properties. Researchers have
put a considerable amount of effort in adopting these nano-materials to structurally enhance
an epoxy composite matrix. Though considered very promising many issues such as the
dispersion and the bonding interface have been identified and there remains still no
guaranteed structural improvement.

The potential of epoxy/clay nanocomposite processing and application has been explored
incorporating a study of composite processing methods and characterisation techniques. The
key goals were to reliably achieve full dispersion and exfoliation of nanoclay without
inducing air into the composite system. Two mechanical processes were used for
comparison; a high shear rotary mixing and a laboratory bead mill. Microscopic
observations of the resin before curing shows agglomerated nanoclay visible in the samples
which decreases as the shearing time. Comparing the processing methods showed greater
dispersion in the bead mill processed samples. TEM and X-ray diffraction were used to
measure the exfoliation of the nanoclay. The analysis showed that the nanoclays had
become intercalated, with the clay layer separation increasing from 2- 4 nm. Further testing
looked at the mechanical and thermal properties of the nanoclay composites, comparing the
nanoclay processing in amine hardener or solvent. The effect of changing the amount of
nanoclay present in the epoxy was also recorded. Testing showed that a solvent processing
II
method gave best results, with a nanoclay loading of 2wt% processed with a solvent in a
bead mill.

The performance of CNTs in epoxy composites was also assessed looking at different
bonding mechanisms (covalent and Vander Waals) of the carbon nanotube to the resin. The
rheological, mechanical and fracture toughness properties were tested in epoxy resin with
different nanotube loadings. These properties were explored in a brittle and a flexible resin,
achieved by using two amine curing agents. The covalently bonded tubes showed
Newtonian rheological properties and the greatest enhancement in tensile compressive and
flexural strength and modulus as well as K1c fracture toughness. MWNT resins
incorporating non-covalent bonds displayed shear thinning rheological behaviour and
showed greatest improvement in Charpy impact toughness. Fibre reinforced composites
laminates have also been investigated by enhancing a formulated pre-preg material.
Compressive properties and interlaminar shear stress were tested in a woven carbon fibre
composite and some increased properties have been seen which shows potential for further
research.
Carter, Humphrey Alexander Copsey
e494cd44-31a4-4544-9b56-44a5a53bf2e4
Carter, Humphrey Alexander Copsey
e494cd44-31a4-4544-9b56-44a5a53bf2e4
Shenoi, Ramanand
a37b4e0a-06f1-425f-966d-71e6fa299960
Jones, D.
3db17fb6-80c9-4b77-85e5-ffaa220f2db3
Carter, Y. Didier
2a05c6ca-b259-48c4-8a4a-c93e41888c0b

Carter, Humphrey Alexander Copsey (2008) Influences on nanocomposite structural performance: experimental study on materials processing and bonding. University of Southampton, School of Engineering Sciences, Doctoral Thesis, 184pp.

Record type: Thesis (Doctoral)

Abstract

Nanocomposites have been widely reported to enhance performance in polymers, in both
mechanical and physical properties. An increasing amount of research has resulted in many
nanocomposite polymers being applied to various consumer products from motorcars to golf
balls. Yet, at this time, there are no structural applications despite a large number of reports
claiming improved mechanical properties. Carbon nanotubes are renowned for their specific
mechanical properties as well as their thermal and electrical properties. Researchers have
put a considerable amount of effort in adopting these nano-materials to structurally enhance
an epoxy composite matrix. Though considered very promising many issues such as the
dispersion and the bonding interface have been identified and there remains still no
guaranteed structural improvement.

The potential of epoxy/clay nanocomposite processing and application has been explored
incorporating a study of composite processing methods and characterisation techniques. The
key goals were to reliably achieve full dispersion and exfoliation of nanoclay without
inducing air into the composite system. Two mechanical processes were used for
comparison; a high shear rotary mixing and a laboratory bead mill. Microscopic
observations of the resin before curing shows agglomerated nanoclay visible in the samples
which decreases as the shearing time. Comparing the processing methods showed greater
dispersion in the bead mill processed samples. TEM and X-ray diffraction were used to
measure the exfoliation of the nanoclay. The analysis showed that the nanoclays had
become intercalated, with the clay layer separation increasing from 2- 4 nm. Further testing
looked at the mechanical and thermal properties of the nanoclay composites, comparing the
nanoclay processing in amine hardener or solvent. The effect of changing the amount of
nanoclay present in the epoxy was also recorded. Testing showed that a solvent processing
II
method gave best results, with a nanoclay loading of 2wt% processed with a solvent in a
bead mill.

The performance of CNTs in epoxy composites was also assessed looking at different
bonding mechanisms (covalent and Vander Waals) of the carbon nanotube to the resin. The
rheological, mechanical and fracture toughness properties were tested in epoxy resin with
different nanotube loadings. These properties were explored in a brittle and a flexible resin,
achieved by using two amine curing agents. The covalently bonded tubes showed
Newtonian rheological properties and the greatest enhancement in tensile compressive and
flexural strength and modulus as well as K1c fracture toughness. MWNT resins
incorporating non-covalent bonds displayed shear thinning rheological behaviour and
showed greatest improvement in Charpy impact toughness. Fibre reinforced composites
laminates have also been investigated by enhancing a formulated pre-preg material.
Compressive properties and interlaminar shear stress were tested in a woven carbon fibre
composite and some increased properties have been seen which shows potential for further
research.

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Published date: December 2008
Organisations: University of Southampton

Identifiers

Local EPrints ID: 72140
URI: https://eprints.soton.ac.uk/id/eprint/72140
PURE UUID: 4d760bbe-dced-4cab-9a55-885b2e33cae7

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Date deposited: 09 Feb 2010
Last modified: 18 Jul 2017 23:56

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Contributors

Author: Humphrey Alexander Copsey Carter
Thesis advisor: Ramanand Shenoi
Thesis advisor: D. Jones
Thesis advisor: Y. Didier Carter

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