An indentation law for doubly curved composite sandwich panels with rigid-plastic core subjected to flat-ended cylindrical indenters

In this paper, an indentation law (force – indentation relation) is derived for a doubly curved composite sandwich panel subjected to a flat-ended cylindrical indenter using the principle of minimum potential energy. The sandwich panel is composed of two laminated facesheets and a rigid-plastic core. The analysis is nonlinear due to nonlinear strain-displacement relations. In contrast to existing analytical models for the indentation of composite sandwich panels, the geometry of the sandwich panel is a doubly curved shell which includes flat, cylindrical and spherical panels as three special cases. Moreover, both bending and membrane effects are simultaneously taken into account for the indented facesheet. Additionally, the stacking sequence of the facesheets is completely arbitrary, so that all the coupling stiffnesses, are also included in the model. The validity of the derived indentation law is confirmed through comparison with the existed experimental and present FEM (finite element method) results. The effects of some important geometrical and mechanical parameters on the derived indentation law are studied and discussed. It is observed that the stacking sequence of the facesheet has a little influence on the indentation response. Furthermore, for the same indentation force, the indentation depth increases with increasing radii of curvature.