Non linear buckling analysis of laminated composite twisted plates

Abstract

The twisted plate has various applications in turbine blades, compressor blades, fan blades and particularly in gas turbines. Many of these plates are subjected to in-plane load due to fluid or aerodynamic pressures. Buckling of such plates is of special importance especially if the plates are thin. Hence it is necessary to study their behaviour under different types of loads. Laminated composite materials are increasingly used as load bearing structural components in aerospace and naval structures, automobiles, pressure vessels, turbine blades and many other engineering applications because of their high specific strength and stiffness. For a complete buckling study, a geometrically nonlinear analysis should be carried out. In a geometrically nonlinear analysis, the stiffness matrix of the structure is updated between loading increments to take into account deformations which affect the structural behaviour unlike a linear buckling analysis where the stiffness matrix is constant through the analysis. The analysis is carried out using ANSYS software. In ANSYS, the shell 281 element with six degrees of freedom per node is used. A twelve by twelve mesh is found to give good accuracy.The buckling of twisted plates was investigated by a nonlinear analysis. The effect of number of layers, changing angle of twist, width to thickness ratio, aspect ratio, etc is also studied. It was observed in all cases that the buckling load by nonlinear analysis is lesser than that predicted by a linear analysis which proves the importance of the present study.