Paper structure, mechanics, and permeability: Computer-aided modeling

When paper is coated, as for printing, photographic, and many other applications, it simultaneously deforms and is penetrated to some depth by the coating material. Neither deformation nor penetration are well understood in scientific terms. Fundamental knowledge of the rheology and permeability of paper will aid in producing high-quality coated products, and doing so efficiently. This thesis is an investigation, by means of contemporary engineering science, into the stress-strain behavior, i.e. the rheology, and the permeability of fibrous, deformable, porous materials in general, and of paper in particular.; Paper is a two-phase system of solid matrix and porespace. The solid matrix is a disordered network of fibers. How the network deforms is determined here by adapting the matrix structural analysis techniques employed by structural engineers in designing frame buildings and other structures. Adaptations include non-linear elasticity of the fibers, breakage of fibers, and breakage of bondings between fibers. The porespace is a disordered network whose geometry, and thus conductivity to fluid flowing through it, is determined here by analyzing the geometry of the deformed fiber network. That conductivity is proportional to the permeability of the porous medium.; Here the applicability of regular networks to modeling the elastic stress-strain behavior of disordered systems is explored. The stress-strain behavior of two-dimensional models of paper is discussed and a new three-dimensional model of paper structure is presented. The stress-strain behavior of that three-dimensional model is explored. A regular network model of the pore structure and permeability of paper which is compressed normal to the plane of the sheet is examined. Finally, a series of computer algorithms is presented for calculating the pore structure, porosity, and the permeability of the new three-dimensional model and others like it. The variation of permeability of that model with compression normal to the plane of the sheet is probed. The findings are in accord with available experimental data.