Characterization of fiber orientation in short-fiber composites

A method for measuring intermediate states of fiber orientation in short-fiber composites is described. The technique is based on the observation that a representative fiber distribution, for example, the negative of a photomicrograph from a specimen, resembles a collection of diffraction apertures. Diffraction masks for a Fraunhofer diffractometer made from the representative fiber distributions produce diffraction patterns characteristic of the state of orientation. Analyses are presented which relate the features of the diffraction pattern to (i) the orientation distribution, (ii) shape, and (iii) aspect ratio of the fibers. The results from these analyses are in good agreement with experimental diffraction patterns from masks made from simulated fiber distribution patterns.