Free Vibration Analysis and Experimental Study of Functionally Graded Graphene Origami-Reinforced Auxetic Throat-Shaped Shells

The analysis of dynamic characteristics in composite shell structures has long been a critical issue in mechanical engineering, particularly for components with complex geometries and advanced functional reinforcements. However, the dynamic behavior of throat-shaped shells reinforced by graphene origami auxetic metamaterials remains unexplored. In this study, the dynamic characteristics of functionally graded graphene origami-reinforced auxetic metamaterial throat-shaped shells are systematically investigated as the first attempt that explicitly incorporates the negative Poisson's ratio effect, along with the effects of shell geometry, boundary conditions, and metamaterial design parameters. A unified numerical modeling framework is established by integrating first-order shear deformation theory, Hamilton's principle, and an improved Rayleigh-Ritz method to evaluate the vibration characteristics of the structure. The influences of graphene folding ratio, distribution pattern and mass fraction are considered within the proposed formulation. The model is validated through impact hammer experiments and finite-element simulations. Numerical and experimental results indicate that variations in graphene origami parameters lead to distinct changes in the dynamic characteristics of the throat-shaped shell, the Type-X distribution increases frequencies while folding ratio enhances higher modes, highlighting the importance of rational metamaterial design in vibration analysis of advanced composite shell structures.