Fibre-reinforced laminated composites are constructed layer-by-layer, enabling ease of directional stiffness tailoring. Their vast design space is typically explored using two-steps. First, the optimum stiffness for given loads is conceptualised using continuous optimisation of lamination parameters (LPs). Then, discrete optimisation determines a fibre stacking sequence (SS) that closely matches these LPs. While fibre angles are conventionally limited to 45°multiples, finer increments (e.g., ±15°) can enable lighter structures. However, existing SS design methods do not scale well with this increased problem dimensionality. To overcome this challenge, we propose LP2SS, a novel methodology utilising fast Fourier transforms (FFT) and a branch-and-bound optimiser. By treating LPs as a signal, FFTs identify the number of fibre layers oriented at different angles, akin to estimating the magnitude of different frequencies within a signal. This fibre angle distribution guides the branch-and-bound optimiser, enabling efficient SS design with accurate LP matching, while satisfying empirical design rules. The ingenious use of FFTs is key to LP2SS's performance, achieving solutions within tenths of a second, compared to minutes required by state-of-the-art methods. Validated on established benchmarks and a newly proposed comprehensive test set, LP2SS marks a significant advancement in the optimal design of large-scale laminated composite structures.

Hybrid laminar flow control (HLFC) can be a possible solution for future sustainable energy-efficient aviation. The current study proposes a MATLAB-based numerical tool for the design of the suction system for an airfoil optimized for a subsonic short-range HLFC application. Considerable energy losses may occur when the air passes through the perforated metallic outer surface and the inner structure of the suction system. A semi-empirical approach is used to design a layout that provides a target suction velocity based on measured pressure losses through porous medium and substructures. Flowbench measurements were performed on 3D-printed internal core test samples to quantify the pressure losses that can be used to create a lower pressure below the porous sheet matching the target suction velocity. The actual suction realized on the airfoil using this substructure concept has a discrete nature that increases with the distance between two adjacent walls. Finally, the suction system’s power requirement is calculated. The power requirement for distributed suction accounts for the pressure loss characteristics of the porous material, the internal core structure, and throttling holes. However, the study does not include the ducting losses from the substructure to the compressor. Approximately 80% of the total suction power is utilized to eject the sucked air back to the freestream conditions for a system with a compressor and propulsive system efficiency equal to one. The study analyses the performance of the designed internal core layout to different flight conditions and addresses the suction power requirement variation with lift coefficient and flight altitude.