Evaluation method development for ceramic matrix composites towards damage tolerance design in micro gas turbine

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The object of the present study is to develop the quantitative evaluation method of microscopic deformation and fracture characteristics of carbon/carbon and ceramic matrix composites under the environment where the micro gas turbine is operated. Specifically, (1) thermal shock test method, (2) impact mechanical test method under high temperature, (3) creep test method under high temperature and (4) oxidation test method with mechanical loading under high temperature have been developed. Using these methods, the relation between the micro-fractures (initiation, progress and accumulation) and the mechanical properties (stiffness and strength) are clarified quantitatively. The obtained results are as follows.(a) Water quench test method was selected as the thermal impact tests for C/C and ceramic matrix composites and has been developed.(b) Split Hopkinson pressure bar testing system with infrared heater has been developed. This system enables the impact tests up to 1300℃ environment.(c) … More New testing machine with two hydro-electric actuators have been developed. This system can be operated under the force and displacement control conditions. This machine has been instrumented with the infrared heater which enables the oxidation tests with mechanical loading up to 1300℃.(d) A new model on monofilament strength size-effect has been presented through coupling a Griffiths fracture mechanics and a distribution of crack initiating flaw size. As an example, Tyranno ZMI ceramic monofilaments were tensile tested on several gauge lengths to have revealed that the model estimations have fitted the derived data within acceptable error level, while single-modal Weibull model estimations showed a level of discrepancy.(e) It is clarified that the low fiber efficiency in C/C composites do not depend on the degradation of the fiber during the manufacturing process, but depends on the fiber/matrix interfacial strength.(f) The manufacturing process of C/SiCO composites with low environmental impact has been developed. It is clarified that the oxides generated under the oxidation atmosphere enlarged fiber/matrix interfacial strength, which results in the decrease in strength. Less