The objective is to design a joint, suitable for use from low to high temperature by combination of two adhesives along the overlap length in single lap joint. This mixed modulus concept is called Multi-module Bond line (MMBL). At high temperatures, a brittle adhesive (high modulus) in the middle of the joint retains the strength and transfers the entire load. At low temperatures, a ductile adhesive at the ends of the joint is the load-bearing adhesive. The first part of this work deals with the formulation of adhesives with differend stiffnesses to be used in the MMBL concept. Starting from a DGEBA resin/DETDA hardener system, different contents of amine terminated polysiloxane modifiers are added to the original mixture. A phase-separated structure is observed via scanning electron microscopy. The thermal, mechanical and dynamic viscoelastic properties of polysiloxane modified epoxy networks are studied. The second part of this paper will present the infinite element study of the assembly with two formulated adhesives in order to verify if they respect the MMBL concept.