Free Vibration Characteristics of a Variable-Span Morphing Wing

In recent years, there has been an increasing interest to morphing wing technology. Telescopic span morphing mechanism may cause some dynamic instability problems. This study analyzed the dynamic characteristics of span-morphing wings. The differential transformation method is employed to obtain the natural frequencies of the system. The Euler-Bernoulli beam is used as structural model. The unswept cantilevered wing is modeled as three-stepped beam model. Prior to analyzing the free vibration characteristics of bending-torsion coupled three-stepped Euler-Bernoulli beam, validation cases are performed. Several span configurations of Goland and HALE wings are analyzed, and natural frequencies are obtained. Based on the results of this study, it can be stated that the increasing wingspan decreases the natural frequencies in a significant margin. The findings of the numerical analyses show that there is a significant difference in natural frequencies between fully retracted and fully extended wing configurations.