Micromechanics-based viscoelastic analysis of carbon nanotube-reinforced composites subjected to uniaxial and biaxial loading

Viscoelastic response of carbon nanotubes (CNTs) reinforced polyimide nanocomposites subjected to the action of uniaxial and biaxial loads is studied using a micromechanical model based on the unit-cell method. The developed micromechanical model is simple and efficient, and provides closed-form expressions for the effective viscoelastic response of nanocomposites. The representative volume element (RVE) of nanocomposites consists of three phases including continuous CNTs, polyimide matrix and interphase. The state of dispersion of CNTs into the polymer matrix is considered to be random. The obtained elastic and viscoelastic responses are found to be in good agreement with those predicted through other methods and experimental data. The model is then used to study the effects of interphase materials (elastic and viscoelastic) on the creep behavior of nanocomposites. Also, the effects of stress level, CNT radius and interphase on the viscoelastic response of nanocomposites under uniaxial and equi-biaxial including transverse/transverse and longitudinal/transverse loading conditions are examined.