Demetris Pentaras

Carbon nanotubes and nanosensors: vibration, buckling and ballistic impact

The main properties that make carbon nanotubes (CNTs) a promising technology for many future applications are: extremely high strength, low mass density, linear elastic behavior, almost perfect geometrical structure, and nanometer scale structure. Also, CNTs can conduct electricity better than copper and transmit heat better than diamonds. Therefore, they are bound to find a wide, and possibly revolutionary use in all fields of engineering. The interest in CNTs and their potential use in a wide range of commercial applications; such as nanoelectronics, quantum wire interconnects, field emission devices, composites, chemical sensors, biosensors, detectors, etc.; have rapidly increased in the last two decades. However, the performance of any CNT-based nanostructure is dependent on the mechanical properties of constituent CNTs. Therefore, it is crucial to know the mechanical behavior of individual CNTs such as their vibration frequencies, buckling loads, and deformations under different loadings. This title is dedicated to the vibration, buckling and impact behavior of CNTs, along with theory for carbon nanosensors, like the Bubnov-Galerkin and the Petrov-Galerkin methods, the Bresse-Timoshenko and the Donnell shell theory.

Dynamic Deflection of a Single-Walled Carbon Nanotube Under Ballistic Impact Loading

The dynamic deflections of geometrically different single-walled carbon nanotubes are determined under various high-velocity impacts and for different positions at which ballistic impact is applied. Elastic beam model is applied to study the dynamic deflection of single-walled carbon nanotubes for two cases of boundary conditions, namely to clamped–clamped and clamped-free single-walled carbon nanotubes. Moreover, we examine the relationship between the single-walled carbon nanotube radius, the relative position at which the ballistic impact takes place, the speed of the object (e.g., bullet) that strikes the nanotube, and the deflection of the nanotube for a specific bullet size and shape as was used by recent study in the literature.

Some Modern Problems in Structural Engineering Dynamics

This review paper deals with two problems in structural engineering dynamics; one is deterministic, the other is of stochastic nature. One problem is linear, the other is nonlinear. Authors have a biased preferential view on these problems because of their active involvement in the discussed research topics. Still, these two problems reflect, at least in a small manner, some developments in this vast and fascinating field. The first part deals with deterministic linear vibrations of double-walled carbon nanotubes either in classical or refined setting; the second part is devoted to the nonlinear random vibrations of structures. 1. Fundamental natural frequencies of double-walled carbon nanotubes Nanotechnology became recently a very active field of research. This section deals with evaluation of fundamental natural frequencies of double-walled carbon nanotubes under various boundary conditions. The Bubnov-Galerkin and Petrov-Galerkin methods are applied to derive the expressions for natural frequencies. Apparently for the first time in the literature explicit expressions are obtained for the natural frequencies. These can be useful for the designer to estimate the fundamental frequency in each of two series.

Exact solution for natural frequencies of double-walled carbon nanotubes clamped at both ends

We report a study of the natural frequencies of the double-walled carbon nanotubes clamped at both ends. An exact solution is provided and compared with solutions reported in the literature. In contrast to earlier investigations, an analytical criterion is derived to establish the behavior of the roots of the characteristic equation. An approximate Bubnov–Galerkin solution is also obtained to compare natural frequencies at the lower end of the spectrum.

Free Vibration of the Triple-Walled Carbon Nanotubes

Natural frequencies of the triple-walled carbon nanotubes (TWCNTs) are determined both exactly and approximately. For the case of TWCNT which is simply supported at it ends closed-form solutions are obtained. It is shown that there are three series of natural frequencies corresponding to the cubic polynomial equation for natural frequency squares. For the TWCNT that has other boundary conditions approximate Bubnov-Galerkin and Petrov-Galerkin methods are applied. Simple polynomial coordinate functions are utilized. Each of these methods yields three natural frequencies corresponding to the lower and of each frequency spectra.Copyright

Vibration Tailoring of a Polar Orthotropic Circular Plate With a Translational Spring

In this study, the vibration tailoring problem is analytically solved for the polar orthotropic circular plate with translational spring along its circumference. By using the semi-inverse method and postulating the mode shape as a polynomial, we derive a closed-form solution.