Evaluation of Structural Characteristics of Lattice Structure and Proposal of Shear Stopper Lattice for Application to Twist-Morphing Wings

The structural characteristics of a lattice structure depend on the structure of its unit cells. This allows morphing wings to exhibit anisotropic structural characteristics in certain sections and allows them to be lightweight while maintaining the necessary stiffness. In this study, five types of lattice structure are subjected to bending, tensile, compressive, and torsional tests, and the equivalent stiffness of each type is calculated. Among these structures, the cube lattice has high bending stiffness and low torsional stiffness, making it suitable for twist-morphing wings. A twist-morphing wing composed of a cube lattice has relatively low torsional stiffness and can be twisted using an actuator while maintaining the bending stiffness in the wingspan direction. However, the low torsional stiffness can cause excessive torsional deformation when the aircraft is subjected to a large disturbance or load. When the twist angle exceeds a certain value, the torsional stiffness must thus be increased. We propose a shear stopper mechanism and evaluate its effectiveness. A prototype is manufactured and subjected to a torsion test. The results indicate that the proposed mechanism can increase stiffness when the torsional deformation is larger than a certain value. The developed shear stopper is thus effective for morphing wing systems.