Analysis of high temperature creep in pyrolytic carbon

✍ Scribed by W.V. Kotlensky

• Publisher: Elsevier Science
• Year: 1966
• Tongue: English
• Weight: 952 KB
• Volume: 4
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(66)90082-0

✦ Synopsis

Data on short-time high-temperature tensile creep parallel to the substrate for two pyrolytic carbons (pyrolytic graphites) characterized by their microstructures as substrate nucleated (SN) and regeneratively nucleated (RN) h ave been analyzed by means of the Dom method.(i) Over the range of approximately 1.5 to 10% creep strain for the SN material and for creep strains above 1.5% for the RN material, the creep data were found to fit the empirical relationship E=A+&",

where s is the creep strain, t is the time, n is a constant which depends on the material, and A and B are parameters depending on both the material and the test conditions. The SN material was characterized by n =0.60, while the RN material had n=0.42. The same apparent activation energy of about 250 kcal/mole was calculated for both of these carbons. As assumed in the analysis, the structural change which occurs during creep was found to be dependent upon the total creep strain, and the same structure was developed at a given load for the same strain independent of test temperature. These structural changes are discussed briefly with reference to the deformation mechanisms.