Geometrically nonlinear static deflection of stiffened composite plates: A fifth-order equivalent model

Nonlinear reduced-order models (NLROM) have been developed to predict the geometrically nonlinear behaviour of structures with low computational cost. NLROMs built using non-intrusive methods are compatible with commercial FE software and have the potential for wide application in engineering. The challenge of non-intrusive NLROMs is to accurately reproduce the internal force of structures. In literature, the internal force has been assumed to be a cubic polynomial function of generalized coordinates. However, this assumption is effective only for structures with small rigid rotations but not for structures with significant rigid rotations such as cantilever structures. In this paper, we propose a fifth-order polynomial approximation of the internal force for such cases. The nonlinear stiffness tensors of the reduced-order model are built using explicit formulas, ensuring applicability to all structures. Our proposed reduced-order model accurately predicts the nonlinear static deflection of composite plates with complex geometries.