Gradient-Based Optimisation of a Carbon-Fibre Wing Structure for Deployment in a Hybrid-Electric Small-Aircraft Configuration

As part of the DLR-Center for Small Aircraft Technologies, the project D-LIGHT+ aims to develop a climate-neutral commuter aircraft by combining hydrogen fuel cells with distributed electric propulsion. The overall aircraft design process is supported by a multidisciplinary approach, bringing together specialists from conceptual design, aerodynamic optimisation, fuel-stack development, hydrogen-tank manufacturing, electric powertrain design, flight dynamics, and aeroelasticity. The weight and size of the fuel stack and powertrain systems have emerged as the key obstacles to this undertaking, prompting a search for creative solutions and technological breakthroughs. One key aspect is the replacement of the current sizing process of the primary wing structures. The new approach implements a gradient-based optimisation process for carbon fibre laminates, tailoring the structural characteristics to the specific requirements of the configuration. For this purpose, a new optimisation model generator is implemented, capable of converting known topology models by identifying key assembly groups. The optimisation models are constructed using lamination parameters, which describe the structural properties of a laminate by a reduced set of variables in a continuous and convex space. This is complemented by a set of constraints, ranging from lamination parameter compatibility and global buckling simulations to the Tsai-Wu failure criterion in lamination parameter space. Finally, this work highlights the integration of this approach into an aeroelastic loads and optimisation framework and addresses the impact on key characteristics of the configuration.