Coupled thermo-mechanical creep behavior of sandwich beams – Modeling and analysis

The viscoelastic creep behavior of sandwich beams and its interaction with changes in the ambient temperature that influences the viscoelastic characteristics of the core material are analytically investigated in this paper. A theoretical model is developed, which accounts for the viscoelasticity of the core via an incremental exponential law that corresponds to the rheological generalized Maxwell model with temperature-dependent spring and dashpot constants, which are obtained from the expansion of the relaxation moduli into Prony series at different temperatures. The model uses the concepts of the high-order sandwich theory for the structural modeling that accounts for the deformability of the core in shear and through its thickness. The time–temperature superposition principle is used for the characterization of the viscoelastic material properties of the core from tests of short duration at different temperatures. An incremental time-stepping analysis is conducted, which accounts for the time variations of the stresses, deformations, temperature field, and material properties. The incremental governing equations and the stresses and deformations fields through the thickness of the core are derived, and the capabilities of the model are studied numerically. The results show that creep of the core leads to significant variations in the internal forces and stress concentrations, which can have a significant influence on the performance of sandwich beams under sustained loads.