The increasing complexity of large-scale thin-walled structures can be handled by using a hierarchical modelling approach. However, in structural engineering a true preliminary design phase is frequently skipped, since reduced models are often either unavailable or unsuitable for the necessary degree of complexity. Before FEM became established, the shear panel theory was used to calculate thin-walled structures efficiently. While numerical finite element formulations of the shear panel theory have been compared to analytical solutions only, there has been limited review of the validity of the underlying assumptions and accuracy of the analytical model itself. The question arises of whether the shear panel theory provides a suitable reduced modelling approach. The aim of this work is to investigate the limitations of the shear panel theory within the preliminary design of thin-walled structures. An extensive parameter study using a detailed FEM model of a plane shear panel was conducted to compare the calculated stiffness and stress state with those of the analytical model. The models show different behaviour in stiffness and stress state for non-rectangular panels. This indicates that the assumptions of the shear panel theory violate the compatibility conditions between the shear panel and the surrounding stiffeners for non-rectangular panels.

The increasing complexity of large-scale thin-walled structures can be effectively addressed using hierarchical modelling approaches. However, in structural engineering, true preliminary design phases are often skipped due to the unavailability or insufficient accuracy of reduced models capable of handling the required complexity. Historically, the shear panel theory provided a computationally efficient method for analysing thin-walled structures before the adoption of the finite element method (FEM). While the shear panel theory includes a formulation for curved panels, it remains limited to one-dimensional representations, making it unsuitable for three-dimensional curved shell structures such as fuselages and wing boxes. Consequently, these structures are typically approximated using plane panels, introducing inaccuracies. This paper presents a novel formulation for rectangular simply curved panels in three-dimensional space that extends shear panel theory to simply curved structures by explicitly incorporating the shear centre into the derivation, enabling its use in preliminary design. The new formulation is validated through comparisons with numerical solutions of a wing box featuring a curved leading edge and analytical solutions of stiffened cylindrical shells. The results demonstrate that the curved panel formulation reproduces the analytical solution and significantly improves accuracy over state-of-the-art planar panel models, providing a more robust tool for the preliminary design of simply curved thin-walled structures.

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.

Reducing the ecological footprint of aviation is a key objective in the development of future aircraft. This is particularly relevant in the emerging field of Urban Air Mobility, which demands sustainable yet industrially feasible solutions due to expected high production rates. As part of the cooperative research project KONKAV, innovative materials and manufacturing methods are being explored to meet these demands. One such approach is the partial consolidation of nonwovens made from recycled carbon fibers, aimed at producing multifunctional, recyclable components for Urban Air Mobility cabin linings for high bending stiffness requirements. This study presents the experimental characterization of various nonwoven architectures, focusing on how different levels of consolidation affect their specific mechanical properties. The partially consolidated structure enables tailored stiffness profiles, making it possible to optimize structural performance while integrating functions such as thermal insulation and acoustic damping directly into the lining. An analytical material model has been developed by analyzing the experimental results. The findings demonstrate that partially consolidated nonwovens can achieve a competitive stiffness-to-weight ratio, with advantages over conventional glass-fiber-reinforced composites in terms of eco-efficiency and circularity. The proposed construction method offers potential for cost-effective, lightweight solutions that support closed-loop material use in aviation interiors.

In the preliminary design of aircraft structures, efficient modelling techniques are essential to balance accuracy and computational cost. Shear Panel Theory (SPT) offers a simple yet effective idealisation of thin-walled, stiffened structures such as wings. It captures more structural detail—like ribs, sweep and taper—than traditional beam idealisation and would otherwise require detailed finite element analysis. However, compared to a finite element model, the degrees of freedom of the structure as well as the meshing effort are significantly reduced, as SPT idealisation uses a structural element approach. This improves mass estimation and structural response calculation and makes SPT particularly well-suited for optimisation tasks in early design phases. This work presents a methodology to derive structural properties of wing segments based on NACA airfoils using SPT. This offers adjustment of the wing’s geometry for use in aeroelastic analysis and enables fast evaluation of structural behaviour and gradient computation, supporting integration into multidisciplinary design optimisation frameworks. The proposed methodology advances the use of idealised structural models in aircraft design by bridging the gap between high-fidelity analysis and system-level aeroelastic simulations, supporting faster and more informed early design iterations.