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Assessing local yield stress and fracture toughness of carbon nanotube poly(methyl methacrylate) composite by nanosectioning
(Applied Mechanics, Department of Engineering Sciences, Uppsala University)
(Materials Science, Department of Engineering Sciences, Uppsala University)
(Centro de Investigación Científica de Yucatán A.C., Mexico.)
(Applied Mechanics, Department of Engineering Sciences, Uppsala University)
(English)In: Article in journal (Other academic) Submitted
Abstract [en]

A nanosectioning (cutting) method was used to test the local shear yield stress and fracture toughness of multiwall carbon nanotube (MWCNT) poly(methyl methacrylate) (PMMA) composites, and the effect of MWCNT content on the stress and toughness were investigated. The composites were prepared by a solution casting method, with MWCNT content varying from 0.05-1.0 wt%. A critical MWCNT content was found at 0.1 wt%; below such a critical content the shear yield stress increases by the incorporation of MWCNTs, while above this content the yield stress reduces. The fracture toughness of the composite was effectively enhanced by the addition of MWCNTs, from 17 J/m2 for the neat PMMA to 25 J/m2 for the 1.0 wt% composite. The shear yield stresses obtained by nanosectioning were correlated to nanoindentation measurement, and possible contributions from the MWCNTs to the fracture toughness of the composite were analysed.

National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:uu:diva-328890OAI: oai:DiVA.org:uu-328890DiVA: diva2:1138174
Available from: 2017-09-04 Created: 2017-09-04 Last updated: 2017-09-04
In thesis
1. Mechanical Properties and Deformation Behaviour of Polymer Materials during Nanosectioning: Characterisation and Modelling
Open this publication in new window or tab >>Mechanical Properties and Deformation Behaviour of Polymer Materials during Nanosectioning: Characterisation and Modelling
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Research in local fracture processes and micro-machining of polymers and polymer-based composites has attracted increasing attention, in development of composite materials and miniaturisation of polymer components. In this thesis, sectioning (machining) of a glassy polymer and a carbon nanotube based composite at the nanoscale was performed by an instrumented ultramicrotome. The yield stresses and fracture toughness of these materials were determined by analysing the sectioning forces. Fractographic analysis by atomic force microscopy was conducted to characterise the topographies and elastic properties of the sectioned surfaces to explore the deformation and fracture behaviour of the polymer during nanosectioning. The study reveals that a transition from homogenous to shear localised deformation occurred as the uncut chip thickness (depth of cut) or sectioning speed increased to a critical value. Analytical and finite element methods were used to model the nanosectioning process. The shear localised deformation was caused by thermal softening due to plastic dissipation. Although not considering sectioning, the tensile properties of a polymer nanocomposite were additionally investigated, where the degree of nanofibrillation and polyethylene glycol (PEG) content had significant effects.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 49 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1553
Keyword
Nanosectioning; Fracture toughness; Adiabatic shearing; Shear band; Nanosectioning; Glassy polymer; Nanocomposite
National Category
Applied Mechanics
Identifiers
urn:nbn:se:uu:diva-328906 (URN)978-91-513-0062-7 (ISBN)
Public defence
2017-10-20, Häggsalen Ångströmlaboratoriet, Lägerhyddsvägen 1, 752 37, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2017-09-21 Created: 2017-09-04 Last updated: 2017-10-18

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