Numerical Brazilian disk testing of multiscale porous Ultra-High Temperature Ceramics

Recent developments in Ultra-High Temperature Ceramics (UHTC) processing have allowed for the introduction of significant amounts of porosity into these materials. These developments have widened the scope for how UHTCs can be integrated into hypersonic vehicles. Functional grading of porosity allows density and thermal conductivity to be spatially tailored to minimize weight penalty while maintaining thermal shielding and resilience to thermal shock. However, added porosity also results in decreased stiffness and strength. These relationships must be quantified in order to enable porous UHTC component design. In this work, a multiscale computational model using a quasi-static Material Point Method (MPM) implementation is used to quantify the mechanical response of porous UHTCs subject to Brazilian disk testing. The as-implemented MPM algorithm can readily handle large deformations, self-contact and damage. Microscale simulations corresponding to a range of strain states are simulated to calibrate an effective macroscale damage model for use in the macroscale Brazilian disk test simulations. A variety of mesoscale property distributions are considered and used in an initial effort to validate the multiscale modeling approach developed herein, with results closely matching experimental findings after model calibration at the mesoscale.