Time-Dependent Creep Analysis in a Layered Cylinder Made of Functionally Graded Piezoelectric with Weak Bonding

The time-dependent creep evolution was analyzed in a rotating layered hollow long cylinder with weak bonding made of functionally graded piezoelectric material (FGPM). The cylinder was subjected to internal pressure, hygrothermal loads and electrical field. Employing the stress–strain relation, electrostatic equation and equilibrium equation, a differential equation was resulted including creep strains. First, the equation was solved analytically for the initial condition by omitting the creep strains. Next, Norton’s law and the Prandtl-Reuss relations were used to achieve the stress and displacement rates by supposing fixed hygrothermal boundaries. Then, using an iterative procedure, the history of stresses, displacement and electric potential was obtained. Finally, the effects of key parameters such as hygrothermal loads, angular velocity, imperfect bonding and number of layers were explored. The results show that the imperfect bonding can yield crack growth at the outer layer due to the brittle behavior of these materials. Also, since the hoop stress increases during the creep evolution, the static analysis has no credit during the creep progress.