Static strength tests and effects of defects on dovetail elements of ceramic matrix composites turbine rotor blades

Abstract

The dovetail of ceramic matrix composites（CMC）turbine blade is the key to the assembly and ability to withstand centrifugal loads of the blade. In order to study the mechanical behaviour of the blade dovetail prepared by the melt infiltration（MI）method under the tensile load in the radial direction of rotating，and verify the influence of the internal quality of the dovetail on its static tensile strength and failure mode，the CMC high pressure turbine dovetail element specimens were designed and fabricated，and a uniaxial static tensile test was conducted，the internal quality of the test specimens was scanned using non-destructive X-ray CT. The test process was monitored using DIC and acoustic emission method. The results show that the CMC dovetail is able to maintain in complete contact under uniaxial static tensile loads，and its static strength and failure are very sensitive to its internal quality，especially to the delamination defects. When there are no delamination defects in the dovetail，the damage generally starts from the neck and quickly spreads，the damage starting load is near the maximum fracture load，and the fracture surface is zigzag. When there are delamination defects in the dovetail，the fracture starts from the defects，and the delamination gradually spread and cause the fracture surface of the dovetail，the damage starting load is decreased by 99.05%，and the maximum failure load is decreased by 14.29% compared to the case of no delamination defects，and the fracture surface is consistent with the delamination defects.

Keywords

• ceramic matrix composites
• mi method
• turbine blade
• dovetail
• delamination defects