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Effect of nanosectioning on surface features and stiffness of an amorphous glassy polymer
(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)
(English)In: Article in journal (Other academic) Submitted
Abstract [en]

Sectioning of a glassy polymer, poly(methyl methacrylate), at the nanoscale was carried out by means of an ultramicrotome. The effects of sectioning thickness and speed on the topography and stiffness over the surface were then investigated by atomic force microscopy. A critical section thickness and speed were identified, below which a flat and smooth cut surfaces were created, with homogeneous elasticity. Above the critical thickness or speed, localized periodic bands were formed on the sectioned surfaces oriented perpendicular to the cutting direction with a nonhomogeneous distribution of the mapped elasticity. Finite-element simulations based on a constitutive model of the polymer reproduced the periodic shear bands observed in the experiments. The influence of sectioning speed on the elastic modulus was predicted by a damage mechanics model and was found to correlate with results obtained by atomic force microscopy. The results lend confidence that critical machining conditions, such as sectioning thickness and speed, can be predicted to avoid undesirable shear localizations and damage formation in manufacture of e.g. small scale optical and photonic applications. 

National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:uu:diva-328888OAI: oai:DiVA.org:uu-328888DiVA: diva2:1138164
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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