Internal friction and elastic modulus behavior of vitreous carbon from 4°K to 570°K

Abstract

Internal friction and elastic modulus values have been investigated for vitreous carbon from 4 to 570°K at frequencies of 21–22 kc/sec. Samples about 4.0 by 0.09 by 0.2 in. were driven in a longitudinal mode, and the dynamic properties were obtained in resonance measurements. As-received samples exhibit low internal friction values ( Q −1 < 3 × 10 −4), but there is evidence of small mechanical relaxations near 50°K and above 400°K along with accompanying modulus inflections. Heat treatment at 1800°C, and reactor radiation both appear to affect the mechanical loss and the elastic modulus of the material. Modulus levels of the vitreous carbon are observed to be about 29 × 10 10 dynes/cm 2 and rather insensitive to temperature over the range studied. Although the modulus level is somewhat higher than the typical modulus values of carbon-backbone polymers, the level is within the range of the modulus values observed for some graphites and pyrolytic carbons that have been studied.