Nonlinear free vibration analysis of composite conical shell panel with cluster of delamination in hygrothermal environment

The nonlinear eigenvalue responses of conical composite shell structure with cluster of multiple delaminations are investigated numerically using the displacement-type finite element technique including the influence of the moisture and elevated thermal environment. The governing equation for the free vibrated structure case of the layered conical panel is obtained through a generalization of the principle of virtual displacement. The numerical solutions are obtained through a customized computer code developed via the higher order displacement field model imposing the zero stresses at the top and bottom surfaces of the laminate. The panel model has been discretized using an eight-nodded isoparametric element to maintain the desired C0 continuity and to avoid the mathematical complexity involved in C1-type continuity. A delamination model is developed by accounting single and cluster of delaminations. The delamination is located at centre of the laminates, either in cluster form or segregated over the lamina. The model is developed by considering the laminate is exposed to elevated moisture and temperature environment. The contribution of moisture and temperature effects on delaminated lamina is examined. The solution methodology is validated with published results. Influence of various parameters such as lamination schemes, aspect ratios, support conditions, thickness ratios, curvature ratios and material properties of the linear and nonlinear free vibration frequencies are analysed in detail and presented. The inferences from the study signify the reduction trend of fundamental frequency due to the presence of single/multi-delamination and moisture content.