Effects of lattice stiffeners on the nonlinear behavior of variable-curvature FG-GRC panels subjected to blast and step loads

Abstract

This paper presents a semi-analytical investigation of the nonlinear dynamic responses of lattice-stiffened variable-curvature functionally graded graphene-reinforced composite (FG-GRC) sandwich panels with a porous core under impulsive loading conditions. The structure consists of FG-GRC face sheets and a lightweight porous core, with material properties varying continuously through the thickness according to predefined distribution patterns. A refined smeared stiffener approach is developed to incorporate the mechanical contributions of different lattice configurations, accounting for higher-order shear deformation effects. The theoretical formulation is established based on the higher-order shear deformation theory (HSDT) combined with von Kármán geometric nonlinearity. To address the complexity of the variable-curvature geometry, an approximate stress function satisfying the compatibility condition is introduced within a Galerkin framework. The resulting nonlinear governing equations are derived using the Euler-Lagrange equations and solved via a fourth-order Runge-Kutta scheme to obtain time-dependent responses. Numerical results are presented to evaluate the influences of lattice stiffener parameters, core porosity distribution, graphene gradation, curvature profiles, and loading types (blast and step loads) on the dynamic behavior. The findings reveal that the integration of lattice stiffeners significantly enhances the structural stiffness and mitigates deflection amplitudes, while the presence of a porous core introduces a trade-off between weight reduction and structural rigidity. The interaction among stiffener topology, material gradation, and geometric curvature is shown to play a critical role in the dynamic performance of the proposed structures.