Folding aerofoil sections exploiting Brazier Phenomena

The design of composite flexible hinges in folding structures by exploiting unstable behaviour during bending, i.e. Brazier phenomena, can preclude the added weight and complexity of mechanical hinges. Novel applications motivating this study include folding aircraft wingtips to increase wing aspect-ratio and to comply with airport space restrictions as well as for folding wind-turbine blades facilitating large blade transportation. Currently, there is little published work utilising cross-sectional deformations of aerofoils for novel performance enhancements. Nevertheless, research on Brazier phenomena for circular cylindrical shells made from laminated composite materials is extensive. By recognising this contrast, this study verifies similarities between Brazier phenomena for circular and aerofoil cross-sections through finite element analyses. Similarities are discussed including the dependency of folding load on structural stiffnesses, stacking sequences and consideration of local buckling and limit load.