Time-dependent behavior of viscoelastic three-phase composite plates reinforced by Carbon nanotubes

The recent advancement in the manufacture and analysis of Carbon nanotubes (CNT) has persuaded many researchers to use them as the reinforcing phase of a polymer matrix. Nevertheless, it should be recalled that polymers show a viscoelastic behavior, so that their mechanical properties are functions of time due to the intrinsic nature of the material. In this paper, a Maxwell rheological model is employed to describe the time-dependency of the mechanical properties of the matrix in the framework of linear viscoelasticity. The viscoelastic matrix is enriched by both CNTs and oriented fibers to obtain the so-called three-phase composite materials. Such materials represent the main constituents of the plates investigated in this paper by means of the Reissner-Mindlin theory. The transient response, which is analyzed through the Newmark's scheme, is expressed in terms of central deflection and mechanical parameters for several configurations. The effect of the mass fraction of both reinforcing phases is discussed. The solutions are achieved numerically by means of a Finite Element (FE) code which implements the viscoelastic model and the proper homogenization technique in order to deal with three-phase composites.