1. Context

1.1 Cellulose fibers and paper

A sheet of paper is a tangle of cellulose fibers, hollow, curved cylindrical objects a few millimeters long and around 30 to 50 micrometers thick. In dry paper, the fibers are laid flat in superimposed layers, bonded together at points of contact by hydrogen bonds between the alcohol functions of the polysaccharides (major constituents of the fibrous wall) and form a network. Paper cohesion is good in the dry state, but relatively poor in the wet state due to the loosening of interfiber hydrogen bonds. The mechanical properties of paper are linked, on the one hand, to the morphology of the network (fiber length, thickness, fracturing or fibrillation of the walls, network density, number of contact points, network orientation, etc.) and, on the other,...