Geometrically nonlinear creep behavior of debonded sandwich panels with a compliant core

Abstract

The paper investigates the effects of creep of the core material on the geometrically nonlinear behavior of sandwich panels with debond at one of the core–face interfaces within the framework of the high-order sandwich panel theory (HSAPT). The theoretical model accounts for the viscoelasticity of the core via an incremental exponential law that corresponds to the rheological generalized Maxwell model obtained from the expansion of the relaxation moduli into Prony series. The HSAPT structural modeling accounts for the deformability of the core in shear and through its thickness, as well as for the large displacements of the facesheets. An incremental time-stepping analysis is conducted, which accounts for the time variations of the stresses, deformations, and the geometrically nonlinear effects. 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 deformations and stresses over time, which when combined with the geometrically nonlinear effects of the debonded facesheet, can have an important influence on the performance of sandwich panels under sustained loads. It is shown that stress relaxation due to creep and/or contact may restrain the buckling of the debonded facesheet in some cases.