Comparison of Three Matrix Damage Models for Predicting Mechanical Behaviors of Unidirectional Composites

The damage evolution of the matrix profoundly influences the mechanical responses of unidirectional composites. This study aims to assess the predictive capabilities of three matrix damage models in estimating the stiffness, strength and stress–strain responses of unidirectional composites across various loading scenarios. Initially, the maximum stress criterion and linear damage evolution model were utilized to characterize the damage behavior of fibers, while the developed linear, exponential and sudden-drop damage models were employed to capture the matrix’s damage behavior. Subsequently, a microscale representative volume element (RVE) model was established for unidirectional composite. Periodic boundary conditions were then imposed on the RVE model to predict the mechanical behaviors of the composite under longitudinal tension and compression, transverse tension and compression, and in-plane and out-of-plane shear loading conditions. The predictions are compared and analyzed with experimental results. The results reveal that while all three damage models exhibit consistent and accurate predictions in terms of elastic moduli, significant disparities are observed in their abilities to predict the strengths and stress–strain responses. Additionally, the developed exponential damage model is the most effective in capturing the nonlinear mechanical behaviors of unidirectional composites, exhibiting the strongest comprehensive prediction capability.