The objective of this work is to study the coupling between the hygroelastic properties of papers and their microstructure. The use of images of model paper acquired by X-ray microtomography allowed the characterization in an unprecedented manner of the evolution of microstructural properties of these materials according to their production conditions and during tests where they were placed in atmosphere at controlled relative humidity.
These results provide a new contribution to the knowledge of the statistical nature of the descriptors of fibre properties (size and orientation) and their contacts (surface, bonding degree ratio), of the architecture of fibrous networks that papers constitute (number of fibre-to-fibre bonds) as well as of the size of the representative elementary volumes of microstructural and elastic properties. Based on this information, various models, more or less sophisticated, were developed in the framework of the theory of homogenisation of discrete periodic structures to describe the mechanical properties of paper. This approach sheds new light on the role of fibre-to-fibre bonds on the mechanical behaviour of these materials.