A theory is presented in order to describe the density, elasticity and dynamic viscoelasticity of paper and other fibrous sheet in terms of their structure. The network model on which the theory is based is almost identical with that employed by Nimura and Kido, but the mathematical treatments are different. On computing the number of segments (portion of fiber between two adjacent junctions), the effect of the thickness of constituent fibers is considered. This leads to a excellent agreement between theoretical and experimental results.
The density and the modulus of elasticity of a sheet are respectiN ely proportional to those of the constituent fiber, and increase rapidly with increasing the number of junctions. The correlation between the modulus and the density of the sheet depend markedly upon the effect of the thickness and the distribution function of the inclination of segments to the plane of sheet.