Abstract: This study addresses the critical challenges in nonlinear and damage modeling of fiber-reinforced polymer composites by proposing two innovative improvements. First, within the framework of the incremental-secant nonlinear method, we have developed a novel mean-field homogenization model that innovatively incorporates asymmetric plasticity of the matrix and fiber-matrix interface debonding. This approach demonstrates unique advantages in capturing the progressive damage evolution of composites under complex loading conditions such as in-plane shear, effectively overcoming the technical limitations of conventional methods in accurately simulating the gradual descent phase of the stress-strain curve. Second, the model pioneers in considering strain-induced fiber reorientation effects by quantitatively characterizing the dynamic evolution law of fiber orientation during shear deformation, significantly enhancing prediction accuracy for large shear deformations in composites. Validated through ABAQUS finite element simulations, the proposed model successfully integrates multiple complex mechanisms including asymmetric matrix plasticity, interface debonding, and strain softening. This advancement provides a new theoretical framework for precision design of aerospace composite structures.