Effect of rotational imbalance on fracture rotation speed of carbon-carbon ring

Spin burst tests of carbon-carbon (C/C) rings were carried out to confirm the fracture criterion under high speed rotation as a function of the inner/outer diameter ratio R. The C/C rings were made of a quasi-isotropic lamination type and were confirmed by static tensile tests to have isotropic strength. The burst rotation speeds of the C/C rings were found to be much lower than those expected from stress distributions. A detailed inspection of stress distributions in the C/C rings revealed that a rotational imbalance inherent in C/Cs caused a high average hoop stress and stress concentration around the inner radius. These effects were shown to lower fracture rotation speeds.