Abstract
In accord with Johnson and Tyson readily discernible dark (extinction) bands in bright field images and bright (intensity) bands in (002) dark field images were observed in fragments as well as the ends of broken commercial polyacrylonitrile based graphitized carbon fibers (tensile strength = 1.78 × 109 Nm-2, tensile modulus = 3.48 × 1011 Nm-2; 6.895 × 103 Nm-2 = 1 psi). The bands are oriented at right angles to the fiber axis. Denoting the band dimensions parallel and perpendicular to the fiber axis direction as Bx and By respectively, it was found that Bx was in the range ∼1.5 nm - 7.0 nm whereas By was in the range ∼3.0 nm - 25.0 nm. The ratio Bx/By for individual bands varied in the range 1/8 to one but was usually less than one.
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