Modeling and verification of 2D-C/SiC elastoplastic damage behavior based on micro-mechanism under multiaxial stresses

The complex nonlinear mechanical behavior of advanced ceramic matrix composites under multiaxial stress states challenges for their engineering design and application. This study focuses on 2D-C/SiC composites and proposes a modeling approach based on micro-mechanism for their elastoplastic damage behavior under multiaxial stresses. By establishing the relationship between microscopic damage mechanisms (matrix cracking and interface debonding) and macroscopic nonlinear mechanical responses (stiffness degradation and residual deformation), an elastoplastic damage constitutive model incorporating physical significance is developed. The model introduces stress-state-dependent coupling coefficients to quantitatively describe the interaction between anisotropic damage/plastic evolution under multiaxial stresses. Model parameters are systematically determined based on experimental data, and the applicability of model is validated under on-axis tension, shear, off-axis tension, and tension of the plate with a hole. The results demonstrate that the proposed model based on micro-mechanism can effectively characterize the nonlinear elastoplastic behavior of 2D-C/SiC composites under multiaxial stresses, so that it can provide a key theoretical model for structural design to describe nonlinear response in complex stresses of large-scale structures.