A Revised Shear Panel Formulation for Parallelogram Panels

The growing complexity of large-scale, thin-walled structures can be managed through the use of hierarchical modelling approaches. In aeroelastic wing design, efficient models are needed during the concept and preliminary design phases, as a large design space must be explored. However, in structural engineering, these models are often reduced-order models that use time-consuming CAD-based FEM models to capture important detail. Shear panel theory has historically been used for such problems, even though it has been reported that the method cannot model the bending-induced torsion of swept wings. Additionally, the assumptions used to derive the parallelogram panel have been criticised for being inconsistent, resulting in deviations in stiffness and stresses. This paper presents a novel formulation for parallelogram shear panels and a novel smearing approach for normal stiffness that does not lead to an overestimation of in-plane bending stiffness. These new formulations are validated through comparisons with FEM reference models of single panels and swept and unswept wings. The results demonstrate that the stiffness and stress state of the new panel formulation match those of the reference model, and that using the formulation achieves the desired bending–torsion coupling of swept wings. Furthermore, the proposed smearing approach allows wing sections to be modelled with the fewest possible degrees of freedom while avoiding the overestimation of bending stiffness.