This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International licence Newcastle University ePrints -eprint.ncl.ac.uk Kossovich EL, Borodich FM, Bull SJ, Epshtein SA. Substrate effects and evaluation of elastic moduli of components of inhomogeneous films by nanoindentation.

This paper discusses special features of mechanical behaviour of coals discovered using depth-sensing indentation (DSI) techniques along with other traditional methods of material testing. Many of the special features are caused by the presence of multiscale complex heterogeneous internal structure within the samples and brittleness of some coal components. Experimental methodology for studying mechanical properties of coals and other natural extreme materials like bones are discussed.It is argued that values of microhardness of bituminous coals correlate strongly with the maximum load, therefore the use of this parameter in application to coals may ⋆ Research was supported by the Russian Science Foundation (grant #16-17-10217) be meaningless. For analysis of the force-displacement curves obtained by DSI, both Oliver-Pharr and Galanov-Dub approaches are employed. It is argued that during nanoindentation, the integrity of the internal structure of a coal sample within a small area of high stress field near the tip of indenter may be destroyed. Hence, the standard approaches to mechanical testing of coals should be re-examined.

We present a new hybrid molecular dynamics model of chitosan oligomers which is constructed specifically for studying chitosan + carbon nanostructures composites, their structure and mechanical properties. The model is derived for application within the modified molecular mechanics force field AMBER. Method of virtual sites mapping allowed to retain hexagonal rings of chitosan backbone. Mass and structural disposition of virtual atoms has been found as function of joined groups' atoms masses and coordinates. Geometrical parameters (e.g., bond length, valence angles, torsional angles and van der Waals distances) were found using semi-empirical methods. Parameters of interaction within the AMBER force field were estimated according to structural and energy characteristics of chitosan dimers and oligomers. Model has successfully passed multilevel verification based on comparison of its behaviour with atomistic chitosan within the same force field. It appeared that the model reproduces structural and energy characteristics of chitosan and its composites with carbon nanostructures. Moreover, it allows estimation of their mechanical properties. Dynamical characteristics of composite components are also well reproduced.

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The results of quantum-chemical analysis of elastic and strength properties of the bamboo-like tube are presented in this paper. For the first time the configuration of the thinnest stable bamboo-like tube was established. The bamboo-like nanotube breaking point is established to be under compression of 11GPa. Configuration of the nanoindentor based on symmetric and streamlined tip of the tube (15,15), presented in this work, provides perfect interaction between the nanoindentor tip and the tissue because tip has no sharp protruding pieces.

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