ИСТИНА

Most of laminated composites used in modern structures exhibit nonlinearity even under elas-tic conditions. Probably, the most evident case that reveals this effect is the plane shear ex-periment, where stress strain diagram is apparently nonlinear directly from low values of load. This experiment demonstrates decrease of shear modulus during increase of shear stress and strain. On the other hand, the damage of the material causes additional nonlinearity to test loading diagrams. The aim of the research is the development of constitutive equations for anisotropic composite materials that takes into account both effects of stiffness degradation under loading.