Abstract：An aircraft rudder is an irregular thin-walled structure with a huge thickness difference between its inner stiffener and skin. To meet its demand for mesh flexibility in analysis, a high-accuracy generic quadrilateral element for the thick and thin flat shell was constructed using coupling membrane element GQ12, which has rotational DOF, and the shear strain mixed interpolated plate element MITC4. Based on this analysis tool, this study has successfully obtained a clear internal optimized stiffener layout via adaptive growth method. Compared with traditional rudder internal frame design, the overall structure stiffness of the optimization result was improved by 33% and the weight was reduced by 29%. The accuracy and practicability of the GQ12+MITC4 coupling element and the effectiveness of the adaptive growth method on rudder stiffener layout topology optimization were verified, thus, providing an innovative and effective method for stiffener layout design of aircraft rudder structure.
