Experimental and numerical study on axial compressive ultimate strength of composite sandwich panels with steel stiffeners

Objectives To address the lightweight design requirements of the upper decks in large cruise ship superstructures, a novel composite sandwich panel with steel stiffeners was proposed, reducing significantly structural weight compared to traditional steel stiffened panel. Methods Experimental and numerical studies were conducted to evaluate the axial compression ultimate strength of the proposed panel. In the experimental phase, a test model with specified dimensions was designed, and tensile tests were performed to refine material parameters. The initial deformation of the specimen was measured before the test, and deformation processes along with load-time histories under axial compression were carefully recorded. In the numerical phase, a finely meshed finite element model was developed in Abaqus/Explicit, incorporating the measured initial deformation. The Tsai-Wu, Shokrieh-Hashin, and LaRC03 failure criteria, combined with instantaneous stiffness degradation models, were implemented via a VUMAT subroutine. Forced displacement was applied to replicate the axial compression process observed in the experiments. The experimental results were used to validate the finite element simulations and assess the applicability of the failure criteria for composite materials. Results Compared to experimental values, the Shokrieh-Hashin and LaRC03 criteria, combined with instantaneous stiffness degradation, predicted ultimate strengths with errors of 5.7% and 2.7%, respectively, and corresponding displacement errors of 3.8% and 2.1%, all within a reasonable range. The LaRC03 criterion, due to its consideration of fiber matrix failure, predicted a larger damage area in the face sheet, slightly lower ultimate loads, but greater deformation. In contrast, the Tsai-Wu criterion predicted premature failure, with an ultimate load error of 3.3% and a significant displacement error of 27.1%. The load-bearing trend in the elastic phase of the simulation is consistent with the experimental results but exhibits certain differences, with the simulated ultimate load exceeding the experimental value. Conclusions The Shokrieh-Hashin criterion can be effectively applied to accurately predict the ultimate strength of composite sandwich panels with steel stiffeners. The LaRC03 criterion, due to its consideration of additional factors, provides more precise predictions but is only applicable under compressive loading conditions. The composite sandwich panels with steel stiffeners achieve a 40% weight reduction compared to the original steel-stiffened panels while effectively lowering the center of gravity of the ship's weight. Experimental and simulation studies on this structure offer an effective methodology for lightweight design and analysis of ship superstructures.