A Test of the Refinement Procedure forDetermining the Crystallite OrientationDistribution: Polyethylene Terephthalate

A test of the refinement procedure for improving the crystallite orientation distribution function is presented for afiber texture sample of polyethylene terephthalate. This is a particularly difficult example because the triclinic unitcell offers no simplification due to symmetry, and the pole figures are sharply peaked. The analysis employed 17observed pole figures and an additional 29 unobserved pole figures reconstructed from the crystallite orientationdistribution function. After three cycles of refinement, in which the maximum value of the coefficient was increasedfrom 6 to 16, the standard deviations,σ qandσ w , of the plane-normal and crystallite orientation distributions werereduced by about a factor of 3. The refined crystallite orientation distribution function indicates that the c -axistends to align along the fiber axis for this polyethylene terephthalate sample.