METHODS OF THE DYNAMIC BEHAVIOR MODELLING, THE STRENGTH ASSESSMENT AND THE STRUCTURAL STABILITY EVALUATION OF COMPOSITE BLADES OF ROTARY MACHINES

The work considers methods of joining and analysis of composite blades of rotary machines, namely options for connecting metal and composite parts, approaches to creating a calculation model and modeling the static and dynamic mechanical behavior of composite blades, and techniques of determining their strength according to various criteria, taking into account the characteristics of connections. For this purpose, a detailed review of the applications of composite blades in rotary machines for various purposes, available in the literature, was carried out, as well as options for combining composite and metal parts were given to determine the most optimal approach to creating a strong blade consisting of such parts. The method of construction of the calculation model includes features of joints, illustrated on the example of a composite rotor blade, which contains a steel root and a composite airfoil with layers of different thicknesses and stiffening ribs connecting two side surfaces of the airfoil and passing along the radial direction of the rotor from the root to peripheral sections of the blade airfoil to ensure its strength and structural stability. The analysis of the strength of the composite blade is performed on the basis of criteria specially developed for composite materials, in particular, the Hashin criterion. It is proposed to analyze the structural stability of the composite blade profile under the influence of the aerodynamic pressure of the flow to determine its critical value, at which the buckling may occur by certain shapes. The dynamic characteristics of the airfoil are found in the form of natural frequencies and natural forms of vibrations, taking into account the prestressed state from centrifugal forces and the aerodynamic pressure of the flow. It is proposed to identify the properties of the composite material of the blade airfoil using numerical experiments and full-scale experimental studies, and the adequacy of the modelling of its mechanical behavior and strength can be checked on the basis of the rig considered in the work.