SPIN BURST TEST OF CARBON-CARBON COMPOSITE DISK

In order to establish design criteria for a turbine disk made of Carbo n-Carbon (C/C) composites, spin burst tests were performed on quasi-is otropically 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 w as in agreement with analytical or finite element calculations in the elastic region, which suggests that the test fixtures of the spin test er 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 o f 393 mis. 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 crite rion. On the other hand, the fracture toughness criterion was shown to be applied for the notched specimen. The difference in the fracture c riterion between the un-notched and the notched C/C composite disks is believed to correspond to that between the double edge notched specim ens 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).