In paper on the basis of the simplified deformation theory of the plasticity offered by prof. B.E. Pobedrya, and FEM the computer modeling and specialized software by calculation of physically nonlinear deformation of fibrous composite materials are developed. Influence of the volume content and mechanical parameters of fiber and matrix on the elastic-plastic deformed condition of fibrous composite materials is investigated. The range of ratio values of the fiber and the matrix where ensured their effective joint functioning is determined. The concentration of stresses in constructions weakened by various types of stress concentrators is studied.