Modeling creep behavior of carbon nanotube/fiber/polymer composite cylinders

In this research, the effects of multi-walled carbon nanotubes on the distribution of long-term creep strains in thick-walled multi-walled carbon nanotube/fiber/polymer three-phase laminated composites are studied. In the first step, micromechanical models are developed to calculate the elastic properties of multi-walled carbon nanotube/vinylester and multi-walled carbon nanotube/E-glass fiber/vinylester composites. Using classical lamination plate theory, equilibrium and compatibility equations and strain–displacement relations, the distribution of effective stresses is considered. Moreover, utilizing Schapery single-integral model for nonlinear viscoelastic materials, Prandtl–Reuss relations and Mendelson’s approximation method, not only the distribution of circumferential and radial strains is investigated but also the effects of fiber orientation and weight fraction (wt.%) of the multi-walled carbon nanotubes on the way of distribution are studied. The results demonstrated that the addition of the multi-walled carbon nanotube to the vinylester can reduce absolute values of the radial and circumferential creep strains and dimensionless effective stresses. Moreover, most reduction occurred in the inner wall of the cylindrical shell when fiber orientation was α = 90°.