Fraunhofer diffraction of short-fiber-reinforced composites aligned by an electric field.

This study aims to determine if aligned, short-fiber composites are capable of producing Fraunhofer diffraction patterns similar to those of human enamel sections and to validate the mechanism of diffraction by comparing the experimental and theoretical fiber spacings. Rectangular composite specimens were filled with short E-glass fibers (120 microm length, 15 microm diameter) to contents of 1, 5, 10, and 25% (vol%). The fibers were oriented perpendicular to the surface normal using an alternating electric field of 0.75 kV/mm. A He-Ne laser was used with thin slices of specimen placed behind a pinhole to produce diffraction patterns. The locations of the diffraction maxima were used to determine the theoretical slit spacings which were compared to the experimental slit spacings determined by microscopy. The specimens produced diffraction patterns analogous to the theoretical Fraunhofer diffraction of light through multiple slits. This was verified by comparing the theoretical spacing of the fibers calculated from the diffraction pattern with the experimental spacing of the fibers determined from the optical micrographs. This work has verified that orientation of short-fiber composites using an electric field can yield composites with sufficient order to produce Fraunhofer diffraction patterns that are qualitatively similar to the diffraction patterns of human enamel sections.