1,720,998 research outputs found
The non linear behaviour of carbon based nanostructures: a Molecular Mechanics Model
No full textFrom about twenty years carbon-based nanostructures are a real challenge for the scientific community, for their enormous technological potential in several contexts of application, including microelectronics (e.g., conductive inks and flexible films), sensoring and actuating systems (e.g., gas sensors), energy generation and storage (e.g., photovoltaic cells, hydrogen storage, supercapacitors), biotechnologies (e.g., membranes for water filtration, gas separation, DNA sequencing) and composites. Their effective exploitation goes hand in hand with in-depth knowledge of their physical behavior. Electronic, optical and mechanics properties are crucial and, moreover, also mutually interacting, even with the possibility of tuning the former trough control of deformation. Knowledge of the mechanical behavior of these nanostructures is also related to the availability of predictive models, e.g., provided by ab-initio methods, by molecular dynamics (or statics) mechanics, but also by continuum mechanics and structural mechanics. In the context of linearized models, aimed at determining just elastic moduli, the cost of computationally onerous methods is not prohibitive; on the contrary, when the mechanical behaviour is highly non-linear, e.g., in post-buckling behaviour, in case of mode interaction or in fracture problems, the recourse to models as simple as possible is necessary. In the present paper a molecular mechanics model, equipped by simple potentials, incorporating binary, ternary and quaternary atomic interactions, is presented and the choice of the parameters of the given potentials is explained. The model is implemented in a numerical algorithm of step-by-step analysis with the objective to provide the equilibrium paths also in advanced post-buckling. Both the accuracy of the model and the reliability of the implementation are valued by means of a tight comparison with results in the literature of Solids State Physics
On the nanoscale mechanical modelling of diatomic hexagonal nanostructures
No full textOver the last two decades, interest in the applications of graphene and carbon nanotubes has continuously grown in a variety of fields, including microelectronics, sensoring and actuation systems, energy generation and storage, biotechnologies and composite materials. In parallel, many researchers have also investigated nanomaterials consisting of elements other than carbon (C), including boron (B), nitrogen (N) and silicon (Si). Some examples are boron nitride (BN) and silicon carbide (SiC) nanosheets and the relative nanotubes.
Similarly to their C analogues, these nanomaterials exhibit exceptional thermal and mechanical properties (e.g., low density, high thermal conductivity, high tensile stiffness and strength). Moreover, the different atomic composition leads to some specific properties, such as stronger resistance to oxidation and chemical stability at high temperatures, giving them advantages over C nanomaterials in harsh environments. As of now, these nanomaterials have drawn attention in different technological fields, including the composites, the manufacture of semiconductors and hydrogen storage. In addition, BN compounds can also be cleaned and reused by means of heating and burning in air, are biocompatible, have low friction coefficient, have excellent sorption performance and are hydrorepellent. For these reasons, they are studied also for applications in medicine (e.g. drug delivery), as lubricants and for water purification from oil, solvents and dyes. The effective exploitation of these nanomaterials goes hand in hand with in-depth knowledge of their physical behavior. Electronic, optical and mechanics properties are crucial and, moreover, also mutually interacting, even with the possibility of tuning the former trough control of deformation [7]. Knowledge of the mechanical behavior of these nanostructures is also related to the availability of predictive models, e.g., provided by ab-initio methods, by molecular dynamics (or statics) mechanics, but also by continuum mechanics and structural mechanics. In the context of linearized models, aimed at determining just elastic moduli, the cost of computationally onerous methods is not prohibitive; on the contrary, when the mechanical behaviour is highly non-linear, e.g., in post-buckling behaviour, in case of mode interaction or in fracture problems, the recourse to models as simple as possible becomes preferable.
In the present paper a molecular mechanics model diatomic nanomaterial with hexagonal nanostructure is presented. The model is equipped by simple potentials, incorporating binary, ternary and quaternary atomic interactions. The parameters for BN sheets and tubes are derived. Numerical examples regarding linear and nonlinear behaviours of BN sheets and tubes are presented
A computational approach for the hygro-thermal modeling of wood under surface densification
No full textA nonlinear model for the out-of-plane behaviour of single-layer graphene sheets
No full textIn the last years, 2D nanomaterials, and in particular graphene, have received considerable attention, due to the wide number of demonstrated or potential applications in electronic nanodevices, energy generation and storage, biotechnologies, composite materials.
The study of their mechanical behaviour plays an important role for their manufacturing and integration in devices, for tuning their performances as well as for controlling the mechanics of their composites.
For this reason, considerable research efforts have been done for modelling their mechanical behaviour through a variety of approaches, ranging from the solid state physics methods to the use of equivalent continua.
The most of the existing literature has focused only the in-plane behaviour of these materials, while there is a lack of studies of their transverse behaviour, relevant for buckling, wrinkling and rippling phenomena or simply to establish the bending stiffness of the continua.
With this in mind, in this paper, the Gillis sticks-and-springs model for the in-plane behaviour of graphene is extended to account also for transverse deformation.
To this aim, the contribution of dihedral angles is included.
Numerical analyses regarding the out-of plane buckling of graphene sheets are addressed
The non linear mechanical behaviour of single layer graphene sheets from atomistic simulation to continuum models
No full textSingle-layer graphene sheets (SLGSs) are the basic structural element of several carbon allotropes, including graphite, fullerenes and carbon nano-tubes (CNTs). Due to their remarkable mechanical properties, extensive interests have been recently devoted to characterize their behaviour at nanoscale in order to investigate also the performance of advanced composites based on their inclusions.
However, the evaluation of SLGSs mechanical properties in a direct experimental way is considered a difficult task because of the technical difficulties and the costs involved in the manipulation of nanoscale objects. For these reasons several modelling tools have been proposed varying from continuum models to atomistic approaches that account for the discrete nature of the matter. The most of the existing literature has focused only the evaluation of the elastic constants and of the force constants of the interatomic potentials, instead much less studies have been made about the nonlinear SLGS behavior
Buckling of single-wall carbon nanotubes from molecular mechanics to continuum models
No full textIn the last years carbon nanotubes (CNTs) have received considerable attention, due to the wide number of applications in electronic nanodevices, energy generation and storage, biotechnologies, composites.
The study of the CNTs mechanical behaviour plays an important role for their manufacturing and integration in devices, for tuning their performances in certain applications as well as for controlling the mechanics of their composites. For this reason, considerable research efforts have been done for modelling the CNTs mechanical behaviour through the solid state physics methods, molecular mechanics models or continua.
The most of the existing literature has focused only on the CNTs linear behaviour, while there is a lack of studies in the nonlinear range, especially of buckling.
With this in mind, a nonlinear molecular mechanics model of single-wall CNTs is presented. The model accounts for standard binary and ternary interactions between the atoms and for dihedral angles.
Numerical analyses regarding the buckling of single-wall CNTs are addressed directly at the nanoscale. The equilibrium paths and the deformed configurations are critically discussed in comparisons with 1D models endowed with suitable microstructure and considerations on the role of the various energy contributions are also provided
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