Development and evaluation of a light-weight flexure-based lockable joint for morphing wings

Single degree of freedom (single-DOF) morphing wings have the advantages of light-weight and multiple morphing shapes, which can enable aircraft to adapt to uncertain flight environments and various mission types. A single-DOF morphing wing with four morphing shapes designed based on the reconfigurable mechanism is introduced firstly in this paper. Then, a light-weight compliant locking mechanism (CLM) based on flexure hinges is proposed for lockable joints in the reconfigurable mechanism. The CLM has two types depending on the locking method, namely the “plug-in” compliant locking mechanism (PCLM) and the “friction” compliant locking mechanism (FCLM). The working principles of the two CLMs are described. The mathematical models are established to assess the static and dynamic characteristics of the proposed CLM, which are also verified by the finite element simulation. The influence of the flexure hinge dimensions on the working performance of the CLM is analyzed, and its dimensions are optimized considering both the locking performance and the maximum stress. Finally, a PCLM and a FCLM actuated by SMA wires are fabricated based on the optimized dimensions. The experiment is conducted to assess the locking torque of the CLM and the feasibility of the proposed CLM used for morphing wings is confirmed.