Non-linear thermo-mechanical behaviour of delaminated curved sandwich panels with a compliant core

A non-linear analysis of a delaminated curved sandwich panel with a compliant core, and a delamination (debond) at one of the face–core interfaces, and subjected to a thermal field and a mechanical loading or combined is presented. The mathematical formulation outlines the governing equations along with the stress and displacements fields for the cases where the core properties are either temperature independent (TI) or temperature dependent (TD). A variational formulation is used following the principles of the high-order sandwich panel theory (HSAPT) to derive the field equations along with the appropriate continuity conditions. The non-linear analysis includes geometrical non-linearities in the face sheets caused by rotation of the face cross sections, and high-order effects that are the result of the radially (transversely) flexible (or compliant) core. The core stress and displacements fields with temperature-dependent (TD) mechanical properties are determined in closed form using an equivalent polynomial description of the varying properties. The numerical study describes the non-linear response of delaminated curved sandwich panels subjected to mechanical concentrated loads, thermally induced deformations and simultaneous thermal and mechanical loads. In the combined loading case the mechanical loads are below the limit point load level of the mechanical response, and the imposed temperature field is varied. The results are displayed in terms of plots of various structural quantities along the sandwich panel length (circumference), equilibrium curves and strain energy release rate curves. It is shown that the combined thermo-mechanical response shifts the linear or non-linear responses,observed for the separate cases of either temperature induced deformations or mechanical loading, into a strongly non-linear response with limit point behaviour and large stresses in vicinity of supports, loads and tips of delaminated zone.