ИСТИНА

Three mathematical models for characterization of different types of nonlinearity of composites behavior under deformation are proposed. The physical nonlinearities of composite materials are usually defined by heterogeneous nature, mechanical properties of constituents, the presence of initial defects caused by imperfections of manufacturing technologies and others. The corresponding approach is proposed, where two types of physical nonlinearity are taken into account, one of which is the stress state dependence of material properties (or their susceptibility to the loading conditions) and the second one is concerned the nonlinearity of stress – strain curves under conditions of shear loading, while the diagrams are approximately linear when the load acts along reinforcement. The corresponding constitutive relations are proposed to describe the considered types of physical nonlinearities of composite materials. To describe the first type of physical nonlinearity in the behavior of composite materials, the stress state parameter is introduced into constitutive relations.