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Smart Cellular Systems with Pressure Dependent Poisson’s Ratios

Attard D., Cauchi R., Gatt R., Grima-Cornish J. N., Grima J. N.

Computational Methods in Science and Technology

2020

Vol. 26, No. 2

37--45

The Poisson’s ratio behaviour of cellular systems which change their internal features when subjected to pressure change to become a “re-entrant” or “non-re-entrant” honeycomb was investigated. It was shown, through finite elements simulations, that these changes in geometry permit the systems to exhibit a wide range of Poisson’s ratios, the magnitude and sign of which can be controlled through the external pressure. Auxetic behaviour was also shown to be obtainable at specific pressures with the right combination of design and materials.

Modelling of the static and dynamic properties of tho-type silicates

Cauchi R., Grima J. N.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

2014

Vol. 18, No 1

5--65

Auxetic materials are materials exhibiting a negative Poisson’s ratio in one of their planes. This phenomenon has been studied in various materials. Zeolites are crystalline substances whose structure is characterised by the framework of linked tetrahedra, each consisting of four oxygen atoms surrounding a cation. The resulting interstitial spaces make them efficient for use as adsorbents and molecular sieves, and many studies have been focused on this aspect. Some of these zeolites may exhibit auxeticity at least in one of their planes. THO (and similar systems, such as NAT and EDI) together with the all-silica equivalent of these have been studied extensively via static simulations for their negative Poisson’s ratio in the (001) plane. In this paper a study of the all-silica equivalent of THO has been carried out via both static and dynamic simulations using the same force-field, where the system was subjected to stress along the x direction. The hypothesised semi-rigid mechanism of deformation, proposed by Grima et al. was then projected over this framework. The results obtained confirmed auxeticity along this plane by means of the COMPASS force-field, in both static and dynamic studies and compared well with the proposed mechanism of semi-rigid rotating polygons. It also showed that as the Young’s modulus of this mechanism increases other mechanisms of deformation increase in importance.