STRUCTURAL STUDIES OF POSTCREEP, PAN-BASED, CARBON FILAMENTS

A large amount of plastic deformation of polyacrylonitrile-based (PAN) filaments occurs after creep at high stress (770 MPa) and at high tem perature (2310-degrees-C) on specially prepared uniaxial specimens. Fi laments were strained up to 140% elongation without necking. The struc ture of these postcreep carbon filaments was studied with electron dif fraction, scanning electron microscopy, transmission electronmicroscop y and X-ray diffraction. Creep reduced the interlayer spacing from the original value of 3.427 angstrom to 3.406 angstrom, which indicates i ncreased graphitization of the turbostratic carbon. Creep reduced the orientation of the graphene planes with the fiber axis from up to 40-d egrees to up to 30-degrees. The fibers had a fine granular structure; the stacking height of the graphene planes increased with creep to 57 angstrom from 45 angstrom.