Technique for Evaluating the Strength of Composite Blades

The paper presents a technique for designing and investigating the strength of a composite blade on an example of a mine ore ventilation fan, considering aerodynamic loads acting on a blade airfoil surface. The technique is based on the use of the finite element method in a combination with the theory of multilayer shells to determine the dynamics and strength of the composite airfoil, as well as the methods of the computational fluid dynamics, namely the Reynolds equations, for modeling an air movement in a fan passage to determine aerodynamic loads. A static strength estimation is based on an application of the Hashin strength criterion. An analysis of the results of strength calculations considering aerodynamic forces indicates a necessity of accounting them for thin-walled composite elements. A possibility of varying a thickness of the shell and taking it into account using the presented method allows to achieve an optimal ratio of strength and weight indices. A buckling analysis of the composite shell under an action of complex loading, based on methods of the linear stability theory, as well as calculations of natural frequencies and natural frequencies with regard to a prestressed state from an action of static loads, completes the technique. The results of the research allow to conclude on an applicability of the presented methodology for analyzing the strength of composite blades and an efficiency of the proposed design of the airfoil, as well as a possibility of its use to create real rotary machines. © 2020, The Institution of Engineers (India).