Maximum buckling load design and post-buckling compressive failure of curved grid sub-stiffened composite panels

The structural efficiency of composite stiffened panels can be substantially improved by utilizing curved stiffening components due to their exceptional mechanical performance and design flexibility. This paper aims to explore the impressive potential offered by the curved stiffening concept in the design of T-shaped stiffened composite panels featuring curved sub-stiffening components. An optimization design framework is proposed to optimize the laminates sequence of skin, ply orientation angles and distribution of the curved sub-stiffeners as well as the curvature of the sub-stiffeners of the proposed curved grid sub-stiffened composite panels to yield higher buckling performance without additional weight. Results demonstrate that introducing composite curved grid sub-stiffeners to the T-shaped stiffened composite panel leads to substantial improvements (+254.42%) in buckling performance, while maintaining equivalent weight designs. Furthermore, the introduction of composite curved grid sub-stiffeners reveals alterations to the post-buckling deformation paths of grid sub-stiffened composite panels, leading to varied collapse loads and degrees of deformation in the composite panels. This highlights the importance of utilizing the composite curved grid sub-stiffeners to improve stability and reduce the risk of failure in thin-walled structures, all while meeting lightweight design criteria. •A novel grid sub-stiffening concept (composite curved grid sub-stiffeners) was introduced and optimized to improve the initial buckling performance of an existing T-stiffened composite panel design with no additional weight.•Substantial improvements in buckling performance were achieved when compared to the T-shaped stiffened and sub-stiffened composite panel with equivalent weight designs.•The curvature of the sub-stiffeners has a considerable influence on the buckling performance and alters the buckling mode shapes.•The introduction of composite curved grid sub-stiffeners alters the post-buckling deformation paths and further affects the initiation and propagation of various failure modes.