Optimising the design of auxetic core airfoil for wing morphing applications

Bird wings demonstrate phenomenal adaptation and aerodynamic performance across varied flight conditions. In contrast, conventional aircraft wings are designed for specific scenarios, limiting their adaptability. Therefore, the integration of smart cellular structures into morphing airfoils is crucial for furthering aircraft development. This entails integrating actuators, sensors, and innovative control systems to modernize aircraft engineering. One intriguing approach is adopting a re-entrant arrangement which exhibits a negative Poisson’s ratio, popularly known as auxetic behaviour. This particular trait can bring substantial advantages to the morphing process. Morphing airfoils containing an auxetic core offer various benefits, including greater deformability, ease of control, variable stiffness, and improved stress tolerance. This research provides a novel approach by discovering the optimal re-entrant unit cell and extending its key advantage within the aerospace sector, focusing on achieving maximal wing trailing edge deflection. The paper explores the in-plane characteristics of a 2D re-entrant auxetic structure and evaluates the consequences of parameter changes on the structure’s negative Poisson ratio. Through multi-objective optimisation employing a genetic algorithm, the study achieves a remarkable 99.53 % enhancement in Poisson’s ratio and a substantial 158.70 % rise in the relative elastic modulus, as evaluated analytically. Further, Finite element analysis (FEA) of the Eppler 420 airfoil reveals that integrating the improved re-entrant core within the airfoil leads to a significant augmentation of 63.56 % in trailing edge deflection compared to past research. This research emphasizes the potential of adopting optimised re-entrant structures to boost the performance and adaptability of aircraft wings.