M. Ahmadi

Finite element investigation into the thermal conductivity of carbon nanotube/aluminum nanocomposites

This paper aims to study the thermal conductivity coefficient of aluminum matrices reinforced by single-walled carbon nanotubes. To obtain the thermal conductivity coefficient of the nanocomposites, a small temperature difference is applied on two opposite edges of a representative volume element. The nanotubes are distributed in Al matrix by using three different patterns, including random pattern, regular pattern with nanotube direction along the temperature difference and regular pattern with nanotube direction perpendicular to the temperature change. It is shown that the best enhancement in the thermal conductivity of aluminum matrix occurs by the regular distribution of the nanotubes along the temperature change. Also, increasing the volume fraction of nanotubes in aluminum matrix leads to increasing the thermal conductivity coefficient of the nanocomposite.

Free and forced vibration analysis of rectangular/circular/annular plates made of carbon fiber-carbon nanotube-polymer hybrid composites

Abstract A multiscale finite element method is adopted in this paper to study the vibrational characteristics of polymer matrix composite plates reinforced with the combination of carbon fibers (CFs) and carbon nanotubes (CNTs). The effects of nanoscale and microscale are coupled through a two-step procedure. In the first step, random dispersion of CNTs into the polymer matrix is modelled using a three-phase representative volume element (RVE). In the selected RVE, the influence of the interphase formed because of non-bonded interactions between the polymer matrix and CNTs is taken into account. In the second step, the distribution of CFs into the composite is modelled, and the elastic properties of CF-CNT-polymer matrix hybrid composite are calculated for various values of volume fractions of reinforcement phases. Then, the free and forced vibration behaviors of composite plates are analyzed. It is considered that the plates have rectangular, circular, and annular shapes and are under clamped/simply supported edge conditions. The effects of CNT/CF reinforcement on the elastic modulus and density of composite and on the free/forced vibration response of the considered structures are investigated. It is shown that the vibrational behavior of plates is significantly affected by the hybrid reinforcement with CNT and CF.

Fracture behavior of the carbon nanotube/carbon fiber/polymer multiscale composites under bending test – A stochastic finite element method

ABSTRACT The behavior of L-shaped samples made of multi-scale carbon nanotube/carbon fiber reinforced polyethylene under the bending test is investigated by using the extended finite element method. The mechanical properties of the multi-scale composite are obtained by a stochastic finite element mode. Initially, molecular dynamics simulations are used to compute the mechanical properties of nanotubes at the nanoscale. Then, by using the finite element method, the properties of the carbon nanotube/polyethylene nanocomposite are obtained. Considering the mechanical properties of the matrix as the properties of nanotube reinforced polyethylene, the carbon fibers are included into the composites in the next scale.

Free Vibration Analysis of Carbon Fiber-Carbon Nanotube-Polymer Matrix Composite Plates by a Finite Element-Based Multi-Scale Modeling Approach

The vibrational behavior of polymer matrix nanocomposite plates reinforced with carbon fibers (CFs) and carbon nanotubes (CNTs) is studied using the finite element method based on a multi-scale modeling approach. The influences of nano- and micro-scale are coupled through a two-step procedure. First, CNTs are dispersed into the polymer matrix. In the selected representative volume element (RVE), interphase due to chemical interaction between CNT and polymer matrix is considered. Also, the state of dispersion of CNTs into the matrix is assumed to be random. In the second step, CFs are randomly distributed in the reinforced polymer with CNTs. The reinforcement is carried out for various volume fractions of CFs and CNTs. Two three-dimensional models including the brick and shell ones are used to generate the results. Moreover, the analysis is presented for square plates under different types of boundary conditions. The effect of nanocomposite thickness on its vibrational response is also investigated.