Abstract

Ceramics matrix composites (CMCs) have higher heat resistance and specific strength than conventional metal. These effects can contribute to not only reducing cooling air and parts weight, but also increasing turbine inlet temperature (TIT). As a result, CMCs have potential to improve aero-engine performance and reducing emission. CMCs also have complicated material characteristics to apply aero engine turbine parts. Stress-strain curve shows not only non-liner behavior in higher stress level but also anisotropy. The behavior and fracture toughness show the anisotropy because of material internal structure. Material strengths indicate anisotropy as well. Low cycle fatigue (LCF) strength indicates dependency of stress gradient. Thus, conventional design methods using linear elastic analysis model and peak stress assessment are too conservative to design CMC parts. IHI is developing SiC-SiC 3D woven fabric which is used for aero engine turbine vane and also building up a fracture prediction model to design the CMC turbine vane. Fracture prediction model is composed of structural analysis model to estimate deformation and fracture evaluation model to predict strength. The material model is assumed as a homogeneous substance and this material model constitutive equation is constructed from the theory of continuum damage mechanics (TCDM). In fracture model, that strength parameter is calculated with averaging stress fields. Multi-axial stress fields are evaluated by engineering equations referred to Hashin’s criteria. To validate our fracture prediction model, specific structural feature test were conducted. Sub-component tests were based on the building block approach that was general to validate structural reliability of composite material parts. Static tests and low cycle and high cycle fatigue tests were carried out at room temperature and high temperature. The validation test results showed good agreement with prediction. Finally we have made sure the validation of this fracture prediction model.

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