The optimisation of structures with constrained viscoelastic layers is a major issue in the design of submarines, to ensure stealthiness performances. The first aim of this work is to develop a methodology to build reliable master curves of viscoelastic materials from dynamic mechanical analyzer measurements. The second aim is to propose reduction methods based on Craig-Bampton substructuring approach to solve the system composed of a mechanical structure with embedded damping material in the frequency domain. These strategies are applied to the response of a bidimensional viscoelastic sandwich ring with stiffeners.