Finite element analysis of stress concentration and buckling behaviour in composite panels with cutouts

This study presents a detailed finite element investigation of stress concentration and buckling behaviour in laminated composite panels with circular cut-outs reinforced using flange configurations. Unlike previous studies that primarily focus on single loading conditions or limited geometric variations, this work is the first to systematically evaluate the influence of varying flange heights (0 mm – 8 mm) under shear, compressive, and combined loading conditions. Composite panels made of T300/976 carbon fibre reinforced polymer with a 16-layer [± 45] s layup were analysed using MSC Patran/Nastran. The results demonstrate that flange reinforcement significantly improves structural performance. A maximum reduction of approximately 31% in stress concentration factor (SCF) was observed with the introduction of flange reinforcement, while the buckling load factor (BLF) increased from 1.23 in the unreinforced case to 1.37, approaching the performance of a solid panel. The study further identifies that a flange height of 6 mm provides the optimal balance between stress reduction, buckling resistance, and weight efficiency, as further increases yield only marginal benefits. Additionally, the results highlight that the effectiveness of reinforcement decreases with increasing cut-out diameter, although significant improvements in buckling stability are still achieved. Overall, the findings establish flange reinforcement as an efficient design strategy for enhancing the structural integrity of composite panels with cut-outs under realistic multi-load conditions.