The Relationships of Structure to Properties in Graphite Fibers
Technical rept. 1 May 1973-31 Apr 1974
RENSSELAER POLYTECHNIC INST TROY NY DEPT OF MATERIALS ENGINEERING
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The anomalous density dip in PAN precursor carbon fibers has been investigated with respect to properties of commercial fibers and a series of specially heat-treated fibers. The density minimum is apparently due to a combination of two factors the initial decrease in density caused by weight loss, and the subsequent density increase due to dimensional changes. Modes of failure in Fiber B and Kevlar I, III and IV fibers have been studied. The buckling of these fibers in compression is manifested as oblique strain markings. The strain band directions are used to show that Kevlar I is most ordered and Fiber B, the least. The effect of abrasion on fiber strength has been studied qualitatively abrasion does not appear to cause drastic reductions in strength. CCA-1 rayon precursor carbon fiber and its replacements have been studied using optical microscopy and differential thermal analysis. The differences amongst the carbon fiber cloths and their precursors are substantial and can be expected to result in performance changes when CCA-1 is replaced by either substitute. The microstructure of pitch-based carbon fibers has been studied using ordinary and polarized light microscopy. Variations in fiber shape and optical activity are related to the presence of both isotropic and mosophitic portions in the precursor pitch.
- Laminates and Composite Materials