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International audience; Cohesion of the fibers network is a key element in numerous manufacturing processes of textile structures and composite parts, because it significantly affects the implementability and the obtained result. However, cohesion remains at the moment an intuitive concept. This paper aims to deal with this concept, first proposing a first interpretation of yarn cohesion. Thanks to this definition, the in-plane shear test is proposed to characterize and measure cohesion. Among many difficulties, it appears to be an interesting way to analyze the cohesion of yarns extracted from 7 different batches and to establish the link between cohesion and implementation in manufacturing processes of Herakles which supports this study. In addition, the phenomenon responsible for the yarn cohesion are tackled and the influence of the yarn constitution is analyzed.

International audience; A better apprehension of the behaviour of the interface between sheets of woven reinforcement during the forming of dry fabrics is necessary for a better optimization of the LCM processes. Even if numerical studies are carried out to simulate multi-layer forming, the contact between the layers is very roughly modelled using an approximate friction coefficient. To knowledge, only few preliminary results can be found concerning the contact fabric/fabric. In order to understand and characterize the contact between layers of different fabrics, a specific friction device has been designed in our lab. This machine was designed with the aim of carrying out tests as well on fabric/ fabric, fabric/metal but also fibre/fibre friction. After a short presentation of the device, results concerning steel/steel friction will be presented in order to validate the device. Then first results obtained about fabric/fabric contact will be given, in order to point out the contacts mechanism involved.

This paper concerns the development of an experimental device which is able to form very complex double curved geometry. Objectives are to analyze the evolution of the woven preform during the forming process. This device contains one mechanical module containing the classical tools in forming process, (punch, blank holder, and open-die), and one optical module to measure the 3D-deformed shape and the distribution of local deformations, like shear angles of the woven reinforcement during all the process. Experimental results are obtained with an interlock carbon woven fabric, used in aeronautical applications. Wrinkling and buckling will be analyzed at the global scale of the piece. The evolution of the shear angle will be presented at local scale (on face, or edges of the geometry).