Measurement of Whisker Orientation in Composites by X-Ray Diffraction*

Abstract

Standard x-ray diffraction techniques have been shown to give a quantitative measure of orientation of α-SiC whiskers in polymeric matrices. The pole distributions of the (1120) planes of SiC have been fitted to a normal bivariate distribution where the standard deviation is taken as a measure of the degree of orientation and the volume under the surface as the volume fraction of whiskers oriented within a given set of limits. A semiquantitative trans mission photographic method was also used and the half-arc lengths are shown to give results comparable with those of the quantitative methods. The specimens were whisker filled strands of cellulose triacetate and cupra-ammonium rayon (Cupram), made by a wet spinning process, and an epoxy composite made from the Cupram strand. The strands are shown to exhibit rotational symmetry about the long axis whereas the composite does not.