59789 - Temperature Dependent Fracture Mechanics-Informed Damage Model for Ceramic Matrix Composites 

Structural ceramic matrix composite (CMC) components are subjected to extreme temperatures from the beginning of their lifetime—processing temperatures for C/SiC and SiC/SiC CMCs can be as high as 1500ºC and operating temperatures often range from below room temperature to 1200ºC. Cooldown from extreme processing temperatures causes appreciable manufacturing-induced damage due to high thermal residual stress, and constituent behavior varies substantially over the wide range of operating temperatures. This motivates the need for a multiscale modeling framework that integrates physics-based thermomechanical constitutive models to capture the effects of temperature on scale-specific CMC damage behavior. In this work, a temperature-dependent reformulation of a multiscale fracture mechanics-informed matrix damage model previously developed by the authors will be introduced. Internal state variable theory, fracture mechanics, and temperature-dependent material properties and model parameters will be utilized to model scale-dependent CMC brittle matrix damage initiation and propagation behavior for temperatures ranging from room temperature (RT) to 1200C. A unified damage internal state variable (ISV) will be introduced to capture matrix property degradation due to porosity formation and matrix crack initiation and propagation, and an extended multiscale framework will be implemented to account for residual stresses and damage due to cooldown from processing temperatures. The combination of temperature-dependent material properties and damage model parameters included in the model will allow more accurate simulation of the effects of temperature on the deformation and damage behavior of 2D woven C/SiC CMC material systems. Model calibration will be performed using experimental data from literature for plain weave C/SiC CMC at RT, 700C, and 1200C, and the nonlinear, temperature-dependent predictive capabilities of the reformulated model will be demonstrated for 1000C.