The belt-rib concept for variable-camber airfoils: recent developments

Abstract

The belt-rib concept for lifting surfaces with variable camber evolved at DLR recently as one of the most promising solutions for the adaptive wing. With the belt-rib idea the adaptive wing issue is approached in a new way: instead of a “mechatronic” solution with hinges or linear bearings a “structronic” solution is chosen, where defined, distributed flexibility allow the desired shape changes. The new concept evolves from the classical wing structure. The classical rib, which is in charge of the wing section’s stiffness, is replaced by a “belt rib”, which allows camber changes within given limits while leaving the remaining in-plane stiffness properties of the section widely unchanged. The evolution of the belt-rib concept was accompanied by experimental tests on different prototypes. The last developments concern the construction of a model with solid-state hinges, realized as hybrid glass fiber - carbon-fiber reinforced composite structure. The model is actuated mechanically by Bowden cables, which can be replaced by shape memory wires in the next development stage. In this paper, the fundamentals of the concept and the most relevant results of the first developments are reported. A description of the new belt-rib design follows, which was implemented in a new prototype. The description of the experimental strength proof and an outline of further development work conclude the paper.