Sandwich structures are usually analysed by different methods of finite element representation. Most of them apply an ideal interface that will not collapse during deformation. As the core and the adhesive are weaker than the skins, it is expected that the performance of the adhesive will play a significant role. In this paper is proposed an analysis of sandwich beams that considers the plasticity of the core and of the skin. The 2D analysis considers an elasto-plastic formulation based on an associative formulation. The inclusion of a joint element at the skin-core interface is also proposed. This element may collapse plastically, and debonding will occur. Results so far illustrate the need of such a refined analysis.