Nonlinear dynamic behavior analysis of pre-damaged (cutout) sandwich shell panel

In the present work, a nonlinear mathematical model of sandwich shell panel structure with cutout has been developed to investigate the nonlinear time-dependent deflection responses. The well-established higher-order shear deformation theory and finite element method concepts have been utilized to develop the aforementioned mathematical model. The core and face sheet layers of the sandwich panel are treated as orthotropic layers and stress-strain constitutive relations have been used to model them. In continuation, the Green-Lagrange type of nonlinear strain-displacement relation is used to consider geometrical nonlinearity. A through-thickness cutout has been considered at the arbitrary location of the sandwich panel. The remaining part of the panel is now discretized with nine noded isoparametric elements. The energy approach is used to derive the energy equations, and Hamilton's principle is applied to obtain the governing differential equation for nonlinear dynamic analysis. The time-dependent deflection responses are calculated using Newmark's time integration method. The developed mathematical model is then implemented as a MATLAB algorithm. Now, the necessary mess refinement and validity of the derived numerical model are checked by comparing the present dynamic responses with previously published reference dynamic responses. Further, the present numerical model's robustness is checked by using it to explore the effect of various parameters such as cutout sizes, shapes, and positions (concentric and eccentric), as well as the thickness of the core-face sheet and end conditions on the nonlinear dynamic deflection of the sandwich structure with cutout. Lastly, a detailed discussion, based on the obtained responses has been provided.