Morphing Aircraft: The Need for Flexible Skin

 

The morphing aircraft attempts to break out of the confines of rigid structures with the intention of creating vehicles with multiple functional equilibria. The morphing aircraft is a multirole platform that changes its state substantially to adapt to changing operation environments, and is viewed as part of a revolutionary transformation from large, expensive piloted aircraft to smaller, autonomous types with combined roles and increased functionality. 

Flexible skins constitute an enabling technology for morphing aircraft. The skin must be able to handle large in-plane deformations and out-of-plane aerodynamic loads while simultaneously carrying some shear loads. There are numerous design concepts that can be used for morphing aircraft, but most designs cannot effectively integrate skins. Elastomers constitute a promising group of materials for flexible skins; they are capable of elastically deforming by very large amounts without permanent changes in shape. The occasional cross-links within elastomers define an original shape which will be restored upon unloading.

Since elastomers are generally insulating, elastomeric skins can become charged in service; they could then behave as a capacitor and discharge in a single event causing considerable damage to the surrounding materials and the electronics on the vehicle. To mitigate electrostatic charge buildup, the surface resistivity of the skin should be lowered below a threshold level, which should be retained even under large elastomeric deformations. The conductivity of the elastomeric skin would also provide a level of protection against lightning strike.