Design and testing of a full-scale variable-camber leading edge based on a composite compliant skin and an open-kinematic-chain mechanism

Climate change has prompted the aviation industry to reduce greenhouse gas emissions. Variable-camber leading edges, with their adaptable aerodynamic shapes, hold significant potential for laminar flow wings and contribute to greener aviation. In response to this need, this paper proposes a design optimization method for a variable-camber leading edge featuring an outer variable-thickness composite compliant skin and an inner open-kinematic-chain mechanism. The optimization methodology employs a fiber continuity model based on a ply-drop sequence, a guiding sequence and a thickness sequence to describe the variable-thickness composite compliant skin structure, enabling direct generation of a composite layup sequence that meets fiber continuity criteria. Additionally, the design methodology for the inner open kinematic chain considers the rigid-flexible coupling effect and analyzes the number of driving ribs along the span-wise direction. Finally, a full-scale physical prototype for a large-scale civil aircraft is developed and experimented in the FL-10 wind tunnel, demonstrating that the variable-camber leading edge can smoothly and precisely achieve its target shape and hold its final profile under the corresponding aerodynamic loads, thereby validating the proposed design methodology.