Geometrical Expressions of Spaces in Anisotropic Fiber Assemblies

In order to express the sizes and geometrical anisotropies of void spaces in a random fiber assembly that has an arbitrary distribution of fiber orientation, two quantities (aperture circle and free length) are introduced and their distributions are derived mathematically. It is found that the approximate probability density functions of the radius of aperture circle r and the free length are given by and respectively, where v, p, n, and λ are the quantities proper to the assembly through which the anisotropies of void structures are expressed.