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Micromechanics

About: Micromechanics is a research topic. Over the lifetime, 6000 publications have been published within this topic receiving 162635 citations.


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Journal ArticleDOI
TL;DR: In this paper, the use of Raman spectroscopy in probing the deformation mechanisms of cellulose fibres (regenerated and natural), and two natural cellulose composite systems (wood and paper) is described.
Abstract: The use of Raman spectroscopy in probing the deformation mechanisms of cellulose fibres (regenerated and natural), and two natural cellulose composite systems (wood and paper) is described. It is shown that during tensile deformation the 1095 cm−1 Raman band, corresponding to the stretching of the cellulose ring structure, shifts towards a lower wavenumber due to molecular deformation. By analysing a number of fibres with different microstructures this shift is shown to be invaluable in understanding the micromechanisms of deformation in these materials. Moreover, the rate of Raman band shift is shown to be invariant with stress for all fibre types, consistent with a fibre microstructure based on a modified series aggregate model. In the composite systems, such as wood and paper, it is shown that the stress-induced Raman band shift in the cellulose gives an important insight into their local deformation micromechanics.

170 citations

Journal ArticleDOI
TL;DR: In this article, the coupled electroelastic Green's functions for a transversely isotropic piezoelectric medium were derived by utilizing the contour integral representation of the Green's function derived by Deeg.

169 citations

Journal ArticleDOI
TL;DR: In this paper, a micromechanics model is developed to assess the impact of the effects of electron hopping and the formation of conductive networks on the electrical conductivity of CNT-polymer nanocomposites.
Abstract: The introduction of carbon nanotubes (CNTs) into nonconducting polymers has been observed to yield orders of magnitude increases in conductivity at very low concentrations of CNTs. These low percolation concentrations have been attributed to both the formation of conductive networks of CNTs within the polymer and to a nanoscale effect associated with the ability of electrons to transfer from one CNT to another known as electron hopping. In the present work, a micromechanics model is developed to assess the impact of the effects of electron hopping and the formation of conductive networks on the electrical conductivity of CNT-polymer nanocomposites. The micromechanics model uses the composite cylinders model as a nanoscale representative volume element where the effects of electron hopping are introduced in the form of a continuum interphase layer, resulting in a distinct percolation concentration associated with electron hopping. Changes in the aspect ratio of the nanoscale representative volume element are used to reflect the changes in nanocomposite conductivity associated with the formation of conductive networks due to the formation of nanotube bundles. The model results are compared with experimental data in the literature for both single- and multi-walled CNT nanocomposites where it is observed that the model developed is able to qualitatively explain the relative impact of electron hopping and nanotube bundling on the nanocomposite conductivity and percolation concentrations.

168 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated void growth and coalescence under physical states similar to those found in highly stressed regions ahead of a crack and showed that micro void cavitation and link-up will increasingly dominate the failure process resulting in a brittle-like ductile rupture mode in which very little energy is expended.
Abstract: Void growth and coalescence under physical states similar to those found in highly stressed regions ahead of a crack is investigated. The analysis introduces a representative material volume containing several large voids and a population of microvoids present from the very beginning, all of which are modeled as discrete entities. Plastic yielding has pervaded the material volume of interest. The underlying micromechanics of final rupture is dominated by a succession of rapidly growing microvoids. This involves the synergistic interaction between elasticity associated with high stress triaxiality, stiffness softening caused by plastic yielding and a rich supply of length scales arising from voids of vastly different sizes. A primary feature of the coalescence phase is an unstable deformation mode whereby a minute, benign void rapidly enlarges reaching a size set by the characteristic length of the locally elevated stress field. The process begins with a large void growing in concert with the plastic strain. Simultaneously, a local zone of high stress concentration emanates from the large void and spreads across the material raising the stresses at nearby microvoids. As a result, the hydrostatic stress surrounding one or more microvoids is raised to a level that activates an unstable deformation mode in which the stored elastic energy drives the plastic expansion of the microvoid. Although the overall stress decreases rapidly, small zones of high stress concentration are generated near growing voids—causing even smaller nearby microvoids to grow rapidly. This process continues until the submicron ligament fails by microcleavage or by shearing along crystallographic planes. Plastic yielding plays a crucial role in the above process by lowering the stress level required for the unstable-like growth mode of microvoids. The process outlined above appears to be the main operative mechanism in several observed failure modes in metal alloys. The morphologies of fracture surfaces dominated by flat dimpled rupture and voidsheet formation can be elucidated by the present work. For high-strength metals, our studies suggest that microvoid cavitation and link-up will increasingly dominate the failure process resulting in a brittle-like ductile rupture mode in which very little energy is expended.

168 citations

Journal ArticleDOI
TL;DR: Experimental determination of the strain distribution in prismatic, square cross-section bars of human compact bone in torsion disclosed nonclassical effects associated with the microstructure, including localized deformation at the cement lines.

168 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023233
2022419
2021203
2020235
2019208
2018247