三次元直交織構造を考慮したセラミックス基複合材料の損傷モデリング

Abstract

Ceramic matrix composites (CMCs) are expected to be applied to high-temperature parts of jet engines because they are lighter and have higher heat resistance than Ni-based alloys which have been conventionally applied to turbines. One of the challenges in applying CMCs to engine parts is the difficulty of design due to the difference in material strength due to the microstructure composed of fiber bundles and matrix. The two types of microstructure models were prepared. The one is "unit cell model" which is a simplified shape model with a rectangular three-dimensional orthogonal weave structure. The other one is "CT model" which is a complex detailed shape model created by image recognition technology based on image data acquired by X-ray Computed Tomography (CT). Structural analyses of these models were conducted using a damage model based on continuum damage mechanics including a nonlocal damage theory proposed by the authors. It was confirmed that the fracture strength varies depending on the microstructures which are narrow area of yarns and void in matrix. On the other hand, it was unclear how the parameters related to the damage model affected the material behavior. Thus, the effect of damage model on material behavior was investigated by changing the parameters in this study. As a result, it was found that there was an appropriate parameter for nonlocal damage theory to avoid the mesh dependence of nonlinear behavior and fracture strength.