Influence of local stiffeners and non-uniform edge loads on the stability characteristics of composite laminates with a circular opening

Perforated panels are commonly used in thin-walled structural components, but they are prone to stress concentration near free edges, which can lead to delamination or premature failure at lower stress levels. To mitigate such failures, strategically arranged stiffeners around the cutouts can provide effective reinforcement. This study investigates the influence of stiffener arrangements around circular cutouts and the impact of non-uniform edge load distributions on the buckling behavior of composite panels. A robust and computationally efficient finite element (FE) formulation is developed to facilitate this analysis. The research incorporates a 9-noded heterosis plate element and a compatible 3-noded beam element, accounting for shear deformation and rotary inertia in both the plate and stiffeners. Additionally, due to the non-uniform stress distribution in the perforated panel, a unique dynamic technique has been implemented to account for the stability performance by employing two sets of boundary conditions. A novel mesh configuration is employed to accurately position stiffeners around the cutouts, with its reliability confirmed through validation against existing literature. Key parameters such as cutout size, layup scheme, boundary conditions, and panel aspect ratios are analyzed, with results emphasizing the significant role of stiffener depth in enhancing panel buckling behavior. The study also examines the effects of various stiffener eccentricities on the structural response.