Nonlinear thermomechanical dynamic buckling analysis of imperfect viscoelastic composite/sandwich shells by a double-superposition global-local theory and various constitutive models

摘要

Almost no dynamic buckling analysis has been performed so far for the sandwich/multilayer viscoelastic shells. Even the vibration analyses of the mentioned shells have been restricted to the harmonic loads ignoring the transverse stresses and their continuity at the mutual interfaces of the layers, and the transverse flexibility of the shell. In the present paper, a high-order double-superposition global-local theory inherently suitable for nonlinear analyses is proposed and employed for nonlinear dynamic buckling and postbuckling analyses of imperfect viscoelastic composite/sandwich cylindrical shells subjected to thermomechanical loads. Depending on the nature of the applied loads, both complex modulus and hierarchical constitutive models are used for the viscoelastic materials. Results reveal that as the time duration of the suddenly applied loads decreases beyond the first natural period of the shell, the dynamic buckling load becomes much higher than the static buckling load, especially for the rectangular load-time histories. Furthermore, the relaxation behavior of the viscoelastic material may decrease the dynamic buckling load.