Backscattering of light in determining fiber orientation distribution and area density of nonwoven fabrics

The behavior of light backscattering from a fiber assembly with arbitrary fiber orientation distribution in space and area density depends on the physical properties of the fibers and their arrangement in the fiber assembly. In this paper, a thin fiber layer and its overlapped models are built to study their relations. With this model, the general equation for ascertaining backscattering intensity and the normalized backscattering intensity distribution of light produced from a nonwoven fabric with arbitrary fiber orientation and area density are derived from the theory of scattering and propagation of light. This allows the influence of each of these nonwoven structures to be separately studied. The measured results of the backscattering intensity of light and its distribution by the apparatus initiated in our laboratory are in good agreement with the analytical results calculated from structures of actual nonwovens. The instrument is equipped with a computer-controlled system and displays automatically. The backscattering intensity distribution of light and thus the fiber orientation distribution and area, density of nonwoven fabrics can be determined with this method.