For aircraft structures most popular composites materials are laminates, shaped, whose mechanical properties are characterized by good in plane-rigidity but low out-off plane properties. For applications with a large number of plies difficulties occur during the preforming stage, first step of the RTM Process, where it requires to operate in several stage to master the deformability of each layer. Otherwise for pieces for which loads are out-of plane the use of laminates is less suitable. Using 3D-preforms as reinforcements in the thickness is discussed in the literature but as to its influence on the mechanical behavior of composites. Potentialities of reinforcement through the thickness to minimize defects during processing composite are fairly described. Innovative solutions reinforcements between the layers and developed in this program are based on the stitching technology. Conventional stitching is performed using a one- or double-sided sewing machine which inserts yarns of carbon, glass, aramid or other high performance fibrous tows into several layers of preforms. In this program, thermoplastics and dry preforms will be stitched for hot-pressing and RTM processes. Associated to the analysis of the stitching process, this project is dedicated to the identification of the mechanical behavior of stitched multi-ply preforms during the preforming and injection stages. Modelling developments will concern specific behavior laws including tufting threads for multiplies preform to simulate the preforming and injection (or hot-pressing) stages. Two demonstrators of composite parts will be realized on industrial tools for thermoset and thermoplastics applications. This consortium contains four companies dedicated to manufacturing of composite parts (RT2I, MECANO-ID), one specialist of fibers (SCHAPPE TECHNIQUES) and ESI which is a pioneer and world-leading provider in Virtual Product Engineering, leveraging the physics of materials. Three public laboratories conduct scientific developments. GEMTEX (ENSAIT) will be the leader of this program and tasks concern the tufting technology and the experimental identification of tufted stacking during the preforming stage. The LAMCOS (INSA de Lyon) is a specialist on the mechanical behavior of reinforcement and will develop a specific behavior law for the simulation of the preforming phase. TPCIM (Mines de Douai) will identify the behavior of tufted preforms during the injection (and hot-pressing) stages.