Spin burst test of carbon-carbon composite disk

In order to establish design criteria for a turbine disk made of Carbon-Carbon (C/C) composites. spin burst tests were performed on quasi-isotropically laminated C/C composite disks. Un-notched and notched flat disks were prepared to evaluate the effect of stress concentration on fracture behavior. Strain measurements during rotation tests revealed that deformation of the C/C composite disks with or without notches was in agreement with analytical or finite element calculations in the elastic region, which suggests that the test fixtures of the spin tester have a negligible effect on the deformation of C/C composite disks. In the spin burst tests, the un-notched C/C composite disks burst at an average rotation speed of 25000 r.p.m. with a peripheral velocity of 393 m/s. A comparison between the mean hoop stress averaged over the radius and the tensile strength of smooth specimen suggests that the burst of the un-notched C/C composite disks obey the mean stress criterion. On the other hand, the fracture toughness criterion was shown to be applied for the notehed specimen. The difference in the fracture criterion between the un-notched and the notched C/C composite disks is believed to correspond to that between the double edge notched specimens and specimens with a hole in the static tensile tests, (which was explained by the difference in the magnitude of the damaged zone where the stress concentrations would be relaxed).