A Morphing Composite Air Inlet with Multiple Stable Shapes

Abstract

The morphing air inlet is a structure with shape-changing capability. Shapes include that which is flush with an aerodynamic surface and also a submerged divergent channel suitable for use in an aircraft cooling system. The air inlet structure is multistable in order that it can ‘snap’ open and closed and not require any external holding force to maintain its geometry. Structural multistability is achieved using a novel combination of material prestress and bending stiffness tailoring. Analytical and finite element models are developed in order to explain how this multistability is achieved and to predict the actuator requirements and bending strains within the structure. The air inlet design is autoclave manufactured from carbon fiber reinforced plastic and tested as a proof-of-concept demonstrator. The bending stiffness tailoring enables the structure to fulfill the conflicting requirements of large deformations, low mass, and high stiffness to withstand external loads. The simple construction also aids ease of maintenance and reliability. The morphing demonstrator behaves as a one degree-of-freedom system enabling simple actuation solutions, such as inflatable bladders, to be feasible.