Abstract: A method for elaborating an assembly which includes at least one composite structure part, one metal interface part and one metal structure part, said method includes a first step for assembling the part to the part in order to form a sub assembly and a second assembling step for welding the interface part of said sub assembly to part. The composite structure and metal interface parts are pre-equipped with male/female type mating connections and with locking devices locking the connection. The method can include, during the first assembling step, a phase for pre-assembling the parts by interlocking the male/female mating connections and a phase for locking said interlock by deforming by pressing at least one portion of the locking devices pre-equipped in the metal interface.