<p>The article proposes an approach to calculating the stress-strain state of reinforced composites, accounting for damageability, based on phenomenological modeling of the degradation of their elastic properties due to the accumulation of microdamage. The main hypotheses of continuum damage mechanics are considered, in particular, the specific energy equivalence method (SEEM), which provides a more accurate description of changes in the mechanical properties of layered orthotropic composite materials than the deformation equivalence method (DEM). The effective stress tensor is determined by accounting for three damage parameters: in the fiber directions and under shear. The use of the thermodynamic potential, Helmholtz free energy, to formalize the relationship between damage accumulation and stiffness degradation is justified. An experimental method for determining damage parameters based on repeated tensile (ASTM D3039) and shear (ASTM D5379) tests has been proposed, and the results confirm differences in the degradation kinetics of normal and shear moduli. Analytical dependencies of damage susceptibility on thermodynamic force have been constructed, allowing the damage development process to be approximated. The obtained models have been compared with the original Ladevèze model, and it has been shown that the proposed approach more accurately reflects the behavior of woven composites under complex loading conditions. The results obtained can be used to predict the service life and determine the limit state of structures made of reinforced composite materials through numerical simulation.</p>