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Polymer fracture and deformation during nanosectioning in an ultramicrotome
(Applied Mechanics, Department of Engineering Sciences, Uppsala University)
(Applied Materials Science, Department of Engineering Sciences, Uppsala University)
(Applied Materials Science, Department of Engineering Sciences, Uppsala University)
(Applied Mechanics, Department of Engineering Sciences, Uppsala University)
2017 (English)In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 182, 595-606 p.Article in journal (Refereed) Published
Abstract [en]

The fracture and deformation behaviour of a thermoplastic in the nanosectioning process is investigated by using an ultramicrotome instrumented with force transducers. For sections with thickness values in the order of 10–100 nm, the specific work of surface formation of polymethyl methacrylate is found to be 6.3 J m−2, which is considerably smaller to macroscopic fracture toughness, but relatively close to the theoretical specific surface energy of 1.5 J m−2 of breaking the covalent bonds. Periodic transverse features, spaced a few hundred nanometres on the sectioned surfaces, are observed by atomic force microscopy for sections above a critical thickness. It reveals that a transition of the deformation mode occurs at a certain thickness, which is in concert with sectioning experiments for other materials showing adiabatic shear bands.

Place, publisher, year, edition, pages
2017. Vol. 182, 595-606 p.
Keyword [en]
NanosectioningFractureLocalized deformationPeriodic featuresAdiabatic shearing
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:uu:diva-328893DOI: 10.1016/j.engfracmech.2017.05.044OAI: oai:DiVA.org:uu-328893DiVA: diva2:1138178
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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