Journal of Nano Research Vol. 57

Abstract: Development and promotion of nano materials and technology has gained more attention of research scholars world wide spreding to different disciplines. In this research an approach has been made to study and investigate the behavioural properties and examine the microstuructural qualities of nano composite bricks replacing the cement with microsilica (mS) and nanosilica (nS) additives. The investigation was conducted using four types of specimens being normal concrete mixture with 0% of mS and nS, with 5%, 6% and 7% of mS, with 1%, 1.5% and, 2% of nS and replacing the cement with mixure of 5%+1%, 6%+1.5% and 7%+2% of mS and nS respectively. The results showed that, the maximum compression strength of 27.62MPa and 37.67MPa with the maximum flexural strength of 22.76MPa and 33.56MPa were possible when 6% of mS and 1.5% of nS were replaced respectively. Also, it was found that the maximum compression strength of 31.47MPa and flexural strength of 31.95MPa were achieved when we add 6%+1.5% mS and nS was added together in the concrete mix. The Scanning Electron Microscope (SEM) results revealed that, the mixture of mS and nS enhances the mechanical properties and the addition of mS and nS gives more symbiotic effects of densifying the microstructure in the hardened concrete mixture leading to better harmonic effects on durability.

Abstract: Based on the first order shear deformation plate theory (FSDT) in the present studie, static and dynamic behavior of carbon nanotube-reinforced composite sandwich plates has been analysed. Two types of sandwich plates, namely, the sandwich with face sheet reinforced and homogeneous core and the sandwich with homogeneous face sheet and reinforced core are considered. The face sheet or core plates are reinforced by single-walled carbon nanotubes with two types of distributions of uniaxially aligned reinforcement material which uniformly (UD-CNT) and functionally graded (FG-CNT). The analytical equations are derived and the exact solutions for bending and vibration analyses of such type’s plates are obtained. The mathematical models provided and the present solutions are numerically validated by comparison with some available results in the literature. Influence of Various parameters of reinforced sandwich plates such as aspect ratios, volume fraction, types of reinforcement and plate thickness on the bending and vibration analyses of carbon nanotube-reinforced composite sandwich plates are studied and discussed. The findings suggest that the (FG-CNT) face sheet reinforced sandwich plate has a high resistance against deflections compared to other types of reinforcement. It is also revealed that the reduction in the dimensionless natural frequency is most pronounced in core reinforced sandwich plate.

Abstract: This paper presents a novel numerical procedure to predict nonlinear buckling and postbuckling stability of imperfect clamped–clamped single walled carbon nanotube (SWCNT) surrounded by nonlinear elastic foundation. Nanoscale effect of CNTs is included by using energy-equivalent model (EEM) which transferring the chemical energy between carbon atoms to mechanical strain energy. Young’s modulus and Poisson’s ratio for zigzag (n, 0), and armchair (n, n) carbon nanotubes (CNTs) are presented as functions of orientation and force constants by using energy-equivalent model (EEM). Nonlinear Euler-Bernoulli assumptions are proposed considering mid-plane stretching to exhibit a large deformation and a small strain. To simulate the interaction of CNTs with the surrounding elastic medium, nonlinear elastic foundation with cubic nonlinearity and shearing layer are employed. The governing nonlinear integro-partial-differential equations are derived in terms of only the lateral displacement. The modified differential quadrature method (DQM) is exploited to obtain numerical results of the nonlinear governing equations. The static problem is solved for critical buckling loads and the postbuckling deformation as a function of applied axial load, curved amplitude, CNT length, and orientations. Numerical results show that the effects of chirality angle and curved amplitude on static response of armchair and zigzag CNTs are significant. This model is helpful especially in mechanical design of NEMS manufactured from CNTs.

Abstract: In this paper the finite element simulation is exploited to investigate dynamical behaviors of perfect and defected Single Walled Carbon Nanotube (SWCNT). The natural frequencies, mode shapes and modal participation factors those not be considered elsewhere, are consider through this analysis. Energy equivalent model is adopted to find a linkage between the energy stored in chemical atomic bonds and potential energy stored in mechanical beam structure. Nanotube software modeler is used to generate a geometry of SWCNT structure by defining its chiral angle, length of nanotube and bond distance between two carbon atoms. The whole tube of SWCNT is simulated as cage and bonds between each two atoms are represented by beam (A BEAM 188) with circular cross section, and carbon atoms as nodes. Numerical results are presented to show the fundamental frequencies and modal participation factors of SWCNTs. The effect of vacancies on activation and deactivation of vibration modes are illustrated. During manufacturing of SWCNTs, atoms may be not perfectly bonded with adjacent and some vacancies may be found, so this defect is considered in this study.

Abstract: In present paper, a novel two variable shear deformation beam theories are developed and applied to investigate the combined effects of nonlocal stress and strain gradient on the bending and buckling behaviors of nanobeams by using the nonlocal strain gradient theory. The advantage of this theory relies on its two-unknown displacement field as the Euler-Bernoulli beam theory, and it is capable of accurately capturing shear deformation effects, instead of three as in the well-known first shear deformation theory and higher-order shear deformation theory. A shear correction factor is, therefore, not needed. Equations of motion are obtained via Hamilton’s principle. Analytical solutions for the bending and buckling analysis are given for simply supported beams. Efficacy of the proposed model is shown through illustrative examples for bending buckling of nanobeams. The numerical results obtained are compared with those of other higher-order shear deformation beam theory. The results obtained are found to be accurate. Verification studies show that the proposed theory is not only accurate and simple in solving the bending and buckling behaviour of nanobeams, but also comparable with the other shear deformation theories which contain more number of unknowns