Abstract: Fiber-reinforced polymer composites are extensively employed in aerospace, automotive, and related industries owing to their superior specific strength and stiffness. This research focuses on addressing critical challenges in modeling the nonlinear mechanical behavior and damage evolution of FRP composites, proposing two groundbreaking enhancements to establish an advanced, engineering-oriented damage constitutive model. First, to resolve the inherent limitations of conventional homogenization approaches in predicting inaccuracies under complex loading paths, a novel mean-field homogenization framework is developed using an incremental-secant nonlinear formulation. This framework innovatively incorporates asymmetric elastoplastic deformation of the polymer matrix and fiber-matrix interfacial debonding effects, enabling high-fidelity simulation of progressive damage mechanisms. The proposed model overcomes the longstanding deficiency of traditional methods in capturing the gradual softening phase of stress-strain responses, particularly under in-plane shear and multiaxial loading scenarios, thereby significantly improving predictive reliability for composite failure. Second, a pioneering methodology is introduced to account for strain-induced fiber reorientation during large shear deformations. By formulating a quantitative relationship between shear strain and dynamic fiber orientation evolution, the model achieves exceptional accuracy in predicting nonlinear shear-dominated responses, a critical aspect for composites subjected to complex service conditions. Numerical validation via ABAQUS finite element simulations confirms the model’s capability to integrate multifaceted damage mechanisms, including matrix plasticity anisotropy, interfacial decohesion, and strain-softening effects. The developed framework advances multi-scale damage modeling by bridging microscale damage initiation (e.g., matrix cracking and debonding) with macroscale structural degradation, offering unprecedented insights into failure progression. These advancements provide a robust theoretical foundation for the precision design of aerospace composite structures, particularly in optimizing damage tolerance and weight-critical components. By enhancing the fidelity of virtual testing tools, this research contributes to accelerating the development of next-generation composite materials tailored for extreme operational environments. The proposed methodology is anticipated to serve as a cornerstone for future studies on nonlinear composite mechanics and multiphysics-coupled failure analysis.