Iranian researchers at the Institute of Nanoscience and Nanotechnology of University of Kashan made more practical the usage of carbon nanotubes in intelligent nanostructures by carrying out new researches on them.
Studies have been made in recent few years on the transverse vibrations of carbon nanotubes which improve their performance considerably by using Euler-Bernoulli and Timoshenko beam models. However, none of the said models considered the geometric form of the cylindrical shell of carbon nanotubes.
The result of this research has various applications in producing nano-drills, nano-sensors, nano-resonators, and intelligent nano-structures.
"In this research, the effect of nano scale on the free vibrations has been studied by applying Euler-Bernoulli beam, Timoshenko beam, and Donnell cylindrical shell theories. Therefore, all models have been considered to simulate carbon nanotubes and to use mechanical theories in continuous environments," Dr Qorbanpour, one of the researchers, told the news service of Iran Nanotechnology Initiative Council.
"We first collected references and studied them to obtain equations of motion for Euler-Bernoulli beam model, Timoshenko beam models, and Donnell cylindrical shell model. Then we solved the equations by considering the effect of nano scale, Van der Waals forces between the inner and outer carbon nanotubes for double-walled carbon nanotubes in equations of motion, and buckling modes by applying the boundary conditions of the simple fulcrum as sine functions," he added, noting, "Next, we calculated the natural frequencies. In the end, we compared the theories of Euler-Bernoulli beam, Timoshenko beam, and Donnell cylindrical shell."
The research result shows that contrary to Euler-Bernoulli beam theory, Timoshenko beam theory has included the effects of the shear stress and rotary inertia momentum. Such effects are more important for carbon nanotubes with high wavenumber.
The research has been published in detail in Part C J. Mechanical Engineering Science, vol. 224, pp. 745-756, 2010.
Source: Iran Nanotechnology Initiative Council.