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~Sb.
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SUPPL XMWNTARY NOTES
112-SPCNSOR19IG MILITARY ACTIVITY'IAir Force Materials Laboratory(I4BC)IWright-Patterson AFB, Ohio
ABSTRACTThree dimensional structural models of several different carbon fibers with different precursor bases and represent'ing a wide modulus range have been developed. In addition, a larger variety of commercially available carbon fibers and the newer high performance organic fibers have been studied.Results from the individual characterizations indicate that increasing fiber rnodulu! Is accompanied bydevelopment of thicker, straighter, more crystalline, and better al"igned ribbons of graphite. Quantitative optical measurements on fibers indicate T a very steep modulus gradient is present in fibers from skin to core such that when fibers are loaded in tension, most of the load is born by the skin.General studies indicate PANl fibers experience an inflection in density in "the 30-50 'Msi range while the densitv of hot stretched fibers is uniformfly proportional to modulus. Basal spacing and stack height fluctuate in the region of the density anomaly for the PAN fibers inferring a degree of structural disordering which may W related to the strength anomaly. In addition, the preferred orientation versus modulus relations for PAN and rayen base fibers is different implying constant strapn conditions in PAN.
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