Damage‐Based Constitutive Model and Its Application to 2D‐SiC/SiC Composites

A damage‐based macroscopic constitutive model is proposed to predict the stress–strain response of 2D‐SiC/SiC composites subjected to monotonic and incremental cyclic loadings under different modes, including on‐axis tension, in‐plane shear, and off‐axis tension. The proposed formulation establishes explicit relationships between principal damage variables and stress components, and introduces effective damage parameters to capture coupling effects associated with anisotropic damage. Based on experimental characterization of axial tension and in‐plane shear scenarios, the evolution laws of the principal damage variables and residual strains are identified, and the remaining constitutive parameters are calibrated. The proposed model accurately reproduces the characteristic two‐stage mechanical response, consisting of an initial linear‐elastic regime followed by progressive nonlinear deformation, and captures the degradation of the unloading modulus and the accumulation of residual strain at off‐axis angles of 15°, 30°, and 45°, with good agreement between predictions and experimental stress–strain curves. Scanning electron microscopy observations further reveal orientation‐dependent damage mechanisms, providing microstructural support for the proposed formulation. The resulting framework offers a physically consistent and computationally efficient approach for predicting the anisotropic stress–strain behavior of 2D‐SiC/SiC composites under complex multiaxial loading conditions.