The project belongs to the fundamental field of solid mechanics. The constitutive relationship of materials is the cornerstone of research in solid mechanics. Composites with added fibers exhibit anisotropy, which poses a significant challenge to the establishment of their plastic/nonlinear constitutive theories. A basic requirement is consistency; that is, when the fibers disappear or their properties become identical to those of the matrix, the constitutive equation of the composite material must be able to degenerate into a constitutive equation for an isotropic matrix material given by some classical theory. Existing macroscopic nonlinear constitutive theories generally do not satisfy consistency; microscopic nonlinear constitutive theories, such as self-consistent or generalized self-consistent methods, Mori-Tanaka method, etc., usually rely on the Eshelby tensor, which although satisfies consistency, does not have an explicit form after the matrix enters plasticity, leading to extremely complex nonlinear constitutive equations for composites. This project has conducted research on a unified constitutive theory for composite material elasto-plasticity analysis, connecting the stresses within fibers and matrix through a bridging matrix to create a universal bridging model. The main findings are as follows: 1. A new principle for determining the bridging matrix has been established, which requires that the dependent variables satisfy the symmetry of the composite material's compliance matrix and the consistency of internal stress calculations. The independent variables are expanded into power series of fiber and matrix properties. Once plasticity begins, it is only necessary to change the parameters for fiber or matrix properties within the power series. The resulting bridging model is the only (innately) constitutive theory that satisfies the consistency of internal stress calculations, universally applicable to elasto-plastic responses, and the constitutive equations during the plastic phase are almost as concise as those during the elastic phase. Theories that do not satisfy consistency must rely on three-dimensional constitutive equations to calculate internal stresses within fibers and matrix, even if the composite material is subjected only to unidirectional loads. Compared to the computational volume based on two-dimensional constitutive equations, it increases by one order of magnitude. 2. It reveals that constitutive models based on exact solutions are not necessarily more effective. The bridging models created based on mathematical induction, logical reasoning, and physical abstraction, although different from those obtained from precise solutions in traditional mesomechanics, are also not precise themselves. They are all based on mathematical induction, logical reasoning, and physical abstraction because the applicability of exact solutions is limited. 3. A set of criteria for tensile and compressive failure under complex stress states has been established, which enables the prediction of damage and strength in textile composite materials such as knitted, woven, and braided fabrics. This project's seven representative papers have been cited a total of 495 times, with 294 citations being SCI-E cross-citations. Whether the theory is correct and effective must be confirmed through independent application by others. Australian Engineering Academy Fellow Mouritz and others used two schemes to compare the calculated values of mesomechanics theory including the bridge model with experimental values, and pointed out: 'Both evaluation schemes confirm that Huang's bridging model has the highest overall accuracy' (With both evaluation methods Huang's bridging method provides the best overall agreement with the reported quasi-static composite material properties); Zhejiang Hengshi Fiber Base Co., Ltd., a leading global wind power base material enterprise, has applied the theoretical principles of this project to guide the development of its new products. To date, there are no comprehensive statistics, but it is estimated that other scholars from both domestic and international sources have independently used the bridging model theory formula to study and solve various composite materials science and technology issues, with 163 academic papers published in total. Of these, 123 are journal articles, and 40 are doctoral and master's theses from 9 countries. This indicates that the correctness and effectiveness of the bridging model have been recognized by both domestic and international experts.