Three-dimensional model for analysis of stiffness and hygroexpansion properties of fiber composite materials

A three-dimensional model for stiffness and hygroexpansion of fiber and particle composite materials is presented. The model is divided into two steps, first a homogenization of a single fiber with a coating representing the matrix material, then a network mechanics modeling of the assembly of coated fibers that constitutes the composite material. The network modeling is made by a fiber orientation integration including a linear and an exponential interpolation between the extreme case of homogenous strain and the extreme case of homogenous stress. A comparison between the modeled prediction and measurement data is made for stiffness, Poissons ratio, and hygroexpansion. The matrix material is assumed to have isotropic properties and the fiber or particle material may have arbitrary orthotropic properties.