EVALUATION OF GEOMETRICALLY NONLINEAR STATE OF SURFACE DEFECTS OF AVERAGE THICKNESS OF ORTHOTROPIC STRUCTURE IN COMPOSITE PANELS UNDER COMPRESSION AND SHEAR TAKING INTO ACCOUNT RIGID SUPPORT

In this paper, we consider surface defects such as delaminations in composite load-bearing panels loaded with compressive and shear forces. For defects, the possibility of loss of stability and transition to a geometrically nonlinear state is taken into account. The objects of study in this paper are local panels, which are defects in composite load-bearing panels. The paper presents analytical solutions to the problems of determining the geometrically nonlinear stress-strain state of orthotropic panels, taking into account all-round rigid support under compression and shear. Note that the ratio of thicknesses to overall dimensions of the panel in this case allows us to classify them as panels of medium thickness, for which it is necessary to take into account both membrane and bending stresses. Analytical solutions of geometrically nonlinear problems are obtained using the Bubnov–Galerkin method and the resulting nonlinear equations are presented, linking the acting load and the deflection amplitude. To assess the stress state of defects, analytical expressions for membrane and bending stresses are given. It is noted that the results of determining the stress-strain state are the initial data for the next problem of fracture mechanics on the development of damage.