A Heterogeneous Constitutive Model for Reinforced Carbon-Carbon using LS-DYNA

Reinforced Carbon-Carbon (RCC) is a ceramic matrix, coated C/C composite used in the Space Shuttle’s thermal protection system. A constitutive model for RCC is presented that separates the coating and substrate within a multi-material shell element allowing for bending strains to be accurately computed during a finite element analysis. Version 971 of LS-DYNA contains a new shell element formulation that allows for different constitutive models through the thickness. The carbon substrate is modeled with an orthotropic damage model that was originally developed by Matzenmiller, and has been enhanced into MAT_RATE_SENSITIVE_COMPOSITE _FABRIC (MAT 158). The behavior of the silicon carbide coating is modeled using a new constitutive model that is now included in LS-DYNA as MAT_NONLINEAR_ELASTIC_TENSION_CRACKS (MAT 236). The composite model is used for debris impact analysis on the RCC structures, and good correlation is shown with impact test deflections and damage.