Accurate Stick Model Development for Static Analysis of Complex Aircraft Wing-Box Structures

Aircraft simplified beam finite element models, also known as stick models, are commonly used in aircraft design and multidisciplinary design optimization. Accurate prediction of bending and twisting deformations of the aircraft structure in flight highly depends on the accuracy of the stiffness characteristics in its model. The process of generating a stick model depends on extracting the stiffness properties of the main structure and applying it to a set of beam elements extending along the structure's elastic axis. The present paper proposes a new methodology for extracting accurate bending stiffness properties of an aircraft wing using its 3-D finite element model. The paper reviews the different methodologies commonly used in the industry to generate stick models and gives an insight about the different approximations involved in each methodology and the impact of those approximations on the accuracy of the stick model performance. To validate the proposed methodology, the stick model of the DLR-F6 aircraft wing-box structure is generated using the proposed methodology and also using the methods available in literature. Deformations experienced by the generated stick models are compared with those obtained from the 3-D finite element model of the DLR-F6 aircraft wing box under the same loading condition. The results show that the stick model generated using the proposed methodology is in good agreement with the 3-D finite element model confirming its accuracy.