The objective of this project is to develop a thorough understanding of the thermo-mechanical behaviour of a hybrid box with composite panels but including metallic ribs or fittings. A building-up approach, from different materials CTE characterization up to the validation of a whole box assembly section, is required to develop and validate the capacity to properly modelize the thermo-mechanical effect in hybrid assemblies. Based on this developed methodology, innovative solutions will be studied for the metallic components of a composite wing-box.