Consideration of life prediction model for ceramic matrix composite(CMC) with cooling hole

icaf2023 Tracking Number 84

Ceramic matrix composites (CMCs) have higher heat resistance and specific elasticity than Ni-based alloys, thus it is desired to be applied to aircraft engines such as turbine parts. In high temperature parts, small holes should be pierced to inject cold fluid. However, there are few research on the effect of small hole against the CMC fatigue life. To investigate them, fatigue tests were conducted using flat plates pierced with single hole and multiple holes. Multiple holes were allocated vertically against load direction. Multiple holes have more advanced hole shapes which is called diffuser hole. In the test results, different fracture mode and crack propagation were observed between single holed and multiple holed type. Multiple holed specimens had shorter lives than single hole. In addition, the fatigue lives of diffuser hole were shorter than circular hole. For evaluating life shorting of multiple holed specimens, life prediction models were reconsidered, which includes stress prediction and life prediction. The strength parameters were calculated by averaging stress field, which were predicted by finite element analysis (FEA), in area of CMC unit cell. After evaluating lives of hole specimens, multiple holed lives were predicted by using a smooth test S-N curve. Furthermore, to improve the stress prediction, the strength parameters were recalculated after resizing diffuser hole shape to fit the actual specimen. After that, all specimen lives were predicted around smooth specimen’s S-N curve regardless of the number of holes. Finally, we have established the great life prediction model for the holed CMCs.