Passive load alleviation aerofoil concept with variable stiffness multi-stable composites

Large loads caused by fluid–structure interaction leading to fatigue failure and added robustness of wing-like structures constitute important design challenges to be addressed. A reduction in the penalties associated to the added structural mass required to withstand rare load scenarios by means of load alleviation control is highly desirable, particularly for efficient light-weight engineering systems, such as aircraft and wind turbine blades. Implementation of morphing for modifying the lift distribution to mitigate the impact of rare, but integrity threatening, loads on wing-like structures offers a potential solution for such challenges. In this paper, a passive load alleviation aerofoil concept featuring variable stiffness multi-stable elements is presented. The adaptability in the structural response of the aerofoil when subjected to aerodynamic forces allows for passively changing from a high lift generation shape, to a load alleviation configuration exploiting the energy of the flow. Passive implementations to achieve load alleviation through morphing result in lighter and simpler designs in comparison to actively actuated solutions.