An Anisotropic Damage Constitutive Model For Ceramic Matrix Composites

Fiber reinforced ceramic matrix composites(CMCs) contains a lower brittleness than ceramic but maintain its excellence high temperature performance. Thus it has a broad application prospect in the field of aerospace. CMCs is a kind of anisotropic material and the CMCs constructions are generally used in high temperature and complex loads conditions, while both of the complex stress state and high temperature environment have a significant effect on the mechanical behavior. At present, few anisotropic constitutive model of CMCs concerning the effect of temperature and stress state was publicly reported. Therefore the establishment of a temperature dependent anisotropic constitutive model of CMCs that is applicable to the complex stress state is an important issue in this field.In this paper, the fundamental mechanical response tests in both room temperature and high temperature environments were carried out including tensile tests in 0°and 90°directions, in-plane shear test, compress test and off-axis tensile test. The stress-strain curves were obtained and the failure modes under all kind of loads were studies. On the basis of these tests, an anisotropic constitutive model containing both tensile and shear damage variables was established according to the continuum damage mechanics. The model was then written into the commercial finite element software with subroutine and the tensile and shear stress-strain curves in room temperature and high temperature environments were calculated by the model. Good agreement was found between the calculated results and tests data.Based on the 45° off-axis tests and calculated data, an anisotropic constitutive model concerning the tensile and shear damage coupling relationship was built. With this model, the 30°off-axis tensile curve was calculated and agreed well with the corresponding tests, which proves the rationality of the model. At last, the finite element models of a plat with hole and a turbine blade were calculated and verified the feasibility of the model to the analysis of complex components.