Post-Buckling Analysis of Stringer-Reinforced Composite Wing Panel by Classical and CUF-Based Finite Elements and Effect of Material and Geometrical Uncertainties

The design of reinforced composite aerospace structures and the choice of safety margins are strongly affected by our predictive capability. The analysis of buckling and many other failure mechanisms require the use of mathematical models able to capture 3D complex internal stress states, which is a major concern in composite laminates and represents a challenge of today structural simulations. In this work, a detailed model to characterize the post-buckling behaviour and the stress state of a stringer-reinforced composite wing panel subjected to uniform compression is proposed. The model under consideration has layerwise capabilities and is based on the Carrera Unified Formulation (CUF). According to CUF, refined structural theories can be formulated automatically as a generalization of the three-dimensional equilibrium equations and by making use of arbitrary expansion of the primary unknowns, which can be either distributed along 1D (CUF beam models) or 2D (CUF plate models) supports. Depending on the choice of the expansion functions, low- to high-order structural theories can be developed in a unified manner. Particular attention is focused on the effect of material and geometric uncertainties on the characterization of the limit load, bifurcations, post-buckling and failure. The numerical results clearly show the advantages of the proposed method and provide good confidence for further experimental testing to justify the use of opportune models able to predict and mimic the stochastic dispersion.