The objective of the project is to quantify the importance of solid friction mechanisms in structured fiber assemblies, such as in a yarn or a fabric. In the case of arrangements of fibers such as in a yarn or a fabric, the mechanical strength propagates over distances very large compared to the size of the individual fibers. In order to characterize this mechanical strength, we propose experiments to quantify the frictional forces, the plasticity of the assemblies and the metastability of these systems at the scales of twisted fiber strands, inter-strand contacts, and model fabrics. The experimental study of model systems in which friction at a given scale is controlled is proposed. In particular, the links between average macroscopic behavior (elastic moduli, damage,...) or variable behavior (stress fluctuations,...) and individual sources of friction will be studied. The experimental results will be complemented by a numerical model of frictional fibers in contact which will allow systematic parametric studies.