11 research outputs found
Structure-Sensitive Mechanism of Nanographene Failure
The response of a nanographene sheet to external stresses is considered in
terms of a mechanochemical reaction. The quantum chemical realization of the
approach is based on a coordinate-of-reaction concept for the purpose of
introducing a mechanochemical internal coordinate (MIC) that specifies a
deformational mode. The related force of response is calculated as the energy
gradient along the MIC, while the atomic configuration is optimized over all of
the other coordinates under the MIC constant-pitch elongation. The approach is
applied to the benzene molecule and (5, 5) nanographene. A drastic anisotropy
in the microscopic behavior of both objects under elongation along a MIC has
been observed when the MIC is oriented either along or normally to the C-C
bonds chain. Both the anisotropy and high stiffness of the nanographene
originate at the response of the benzenoid unit to stress.Comment: 19 pages, 7 figures 1 tabl
Topological mechanochemistry of graphene
In view of a formal topology, two common terms, namely, connectivity and
adjacency, determine the quality of C-C bonds of sp2 nanocarbons. The feature
is the most sensitive point of the inherent topology of the species so that
such external action as mechanical deformation should obviously change it and
result in particular topological effects. The current paper describes the
effects caused by uniaxial tension of a graphene molecule in due course of a
mechanochemical reaction. Basing on the molecular theory of graphene, the
effects are attributed to both mechanical loading and chemical modification of
edge atoms of the molecule. The mechanical behavior is shown to be not only
highly anisotropic with respect to the direction of the load application, but
greatly dependent on the chemical modification of the molecule edge atoms thus
revealing topological character of the graphene deformation.Comment: 9 pages, 10 figures, 1 table. arXiv admin note: text overlap with
arXiv:1301.094
Correlations between transmural mechanical and morphological properties in porcine thoracic descending aorta
Determination of correlations between transmural mechanical and morphological properties of aorta would provide a quantitative baseline for assessment of preventive and therapeutic strategies for aortic injuries and diseases. A multimodal and multidisciplinary approach was adopted to characterize the transmural morphological properties of descending porcine aorta. Histology and multi-photon microscopy were used for describing the media layer micro-architecture in the circumferential-radial plane, and Fourier Transform infrared imaging spectroscopy was utilized for determining structural protein, and total protein content. The distributions of these quantified properties across the media thickness were characterized and their relationship with the mechanical properties from a previous study was determined. Our findings indicate that there is an increasing trend in the instantaneous Young[U+05F3]s modulus (E), elastic lamella density (ELD), structural protein (SPR), total protein (TPR), and elastin and collagen circumferential percentage (ECP and CCP) from the inner towards the outer layers. Two regions with equal thickness (inner and outer halves) were determined with significantly different morphological and material properties. The results of this study represent a substantial step toward anatomical characterization of the aortic wall building blocks and establishment of a foundation for quantifying the role of microstructural components on the functionality of aorta
FEM study on mechanical properties of nanocomposites reinforced by defective graphene sheets
Free Vibration of Single Layer Graphene Sheets: Lattice Structure Versus Continuum Plate Theories
High-Resolution Morphological Approach to Analyse Elastic Laminae Injuries of the Ascending Aorta in a Murine Model of Marfan Syndrome
Pseudostatic and dynamic nanomechanics of the tunica adventitia in elastic arteries using atomic force microscopy
NoTunica adventitia, the outer layer of blood vessels, is an important structural feature, predominantly consisting of collagen fibrils. This study uses pseudostatic atomic force microscopy (AFM) nanoindentation at physiological conditions to show that the distribution of indentation modulus and viscous creep for the tunica adventitia of porcine aorta and pulmonary artery are distinct. Dynamic nanoindentation demonstrates that the viscous dissipation of the tunica adventitia of the aorta is greater than the pulmonary artery. We suggest that this mechanical property of the aortic adventitia is functionally advantageous due to the higher blood pressure within this vessel during the cardiac cycle. The effects on pulsatile deformation and dissipative energy losses are discussed