A constitutive model for orthotropic damage in an all oxide woven ceramic matrix composite material

Kurzfassung

The present work includes a constitutive damage meso-model which is based on the investigations of mechanical properties under room and high temperature of a plain-woven oxide/oxide Ceramic Matrix Composite (CMC) material. The models developed for unidirectional plies have been adapted to a plain-woven ply. The damage is defined as the degradation of the in-plane elastic properties. The thermodynamic potentials and the corresponding scalar damage variables are integrated into the framework of continuum damage mechanics. The damage surface of the model corresponds to the Tsai-Wu failure criterion in the stress space. The most of the variables used to define the damage initiation and propagation have been derived from simple on- and off-axis tension and shear tests. Nevertheless, curve fitting is required to obtain a certain set of parameters. The Tsai-Wu failure criterion has been implemented in strain and stress space to predict the failure of the laminate. The material model is then implemented into the commercial finite element software ANSYS Workbench with the help of a user-defined material subroutine written in FORTRAN. The stress-strain relationship for different fibre orientations under room and elevated temperatures is compared with experimental data to assess the accuracy of the model.