Browsing by Author "Izadi, Razie"

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Citation - WoS: 23
Citation - Scopus: 21
Bending characteristics of carbon nanotubes: Micropolar elasticity models and molecular dynamics simulations
(TAYLOR & FRANCIS INC, 2021) Razie Izadi; Meral Tuna; Patrizia Trovalusci; Nicholas Fantuzzi; Fantuzzi, Nicholas; Trovalusci, Patrizia; Izadi, Razie; Tuna, Meral
The present paper aims at evaluating non-classical continuum parameters for each class of armchair and zigzag single-walled CNTs focusing on the scale effect in their flexural behavior observed in molecular dynamics (MD) simulations. Through a non-linear optimization approach the bending rigidities obtained from atomistic simulations are compared to those derived from non-classical continua. For MD simulations a novel method ensuring pure bending is introduced and for continuum modeling micropolar constrained micropolar and modified couple stress theories are employed. The results reveal that adopted non-classical theories notably micropolar theory provide reasonable outcomes with an obvious failure of classical Cauchy theory.
Citation - WoS: 35
Citation - Scopus: 34
Torsional Characteristics of Carbon Nanotubes: Micropolar Elasticity Models and Molecular Dynamics Simulation
(MDPI, 2021) Razie Izadi; Meral Tuna; Patrizia Trovalusci; Esmaeal Ghavanloo; Ghavanloo, Esmaeal; Trovalusci, Patrizia; Izadi, Razie; Tuna, Meral
Efficient application of carbon nanotubes (CNTs) in nano-devices and nano-materials requires comprehensive understanding of their mechanical properties. As observations suggest size dependent behaviour non-classical theories preserving the memory of body's internal structure via additional material parameters offer great potential when a continuum modelling is to be preferred. In the present study micropolar theory of elasticity is adopted due to its peculiar character allowing for incorporation of scale effects through additional kinematic descriptors and work-conjugated stress measures. An optimisation approach is presented to provide unified material parameters for two specific class of single-walled carbon nanotubes (e.g. armchair and zigzag) by minimizing the difference between the apparent shear modulus obtained from molecular dynamics (MD) simulation and micropolar beam model considering both solid and tubular cross-sections. The results clearly reveal that micropolar theory is more suitable compared to internally constraint couple stress theory due to the essentiality of having skew-symmetric stress and strain measures as well as to the classical local theory (Cauchy of Grade 1) which cannot accounts for scale effects. To the best of authors' knowledge this is the first time that unified material parameters of CNTs are derived through a combined MD-micropolar continuum theory.