Carbon-Carbon Fatigue Data. Random fatigue data for uncoated (HTC) carbon-carbon bar specimens are shown in Figure 4-26. Data are included for specimens with various types of inhibitors as well as uninhibited ones. All specimens were made from 3K tow T-300 carbon fabric heat treated to 2150°C (3900°F). Fiber volumes for the inhibited, filled specimens ranged from 42% to 48%. The fillers were added to the phenolic prepregging resin in particulate form. All panels were densified using four cycles of 50-50 pitch-funaldelyde impregnation to a target porosity of less than 5%. To prevent reaction of the fillers with the fibers, the graphitization temperature was limited to 1650°C (3000°F). For infinite life (108 cycles), the lower fatigue limit is approximately 6000 psi (rms) and the upper limit is 12,000 psi (rms).