بررسی رفتار استاتیکی و ارتعاشی پره هلیکوپتر با هسته ساخته شده از ساختارهای فرامواد

Metamaterials are widely used in airplane wings, helicopter blades, turbine blades, etc. due to their shape morphing properties. In helicopter blades, bend-twist coupling is a complex and significant phenomenon in helicopter blade design and performance. As the blade bends during rotation, it also twists simultaneously. Bend-twist coupling has implications for aerodynamic performance, structural integrity, and flight control. Numerous factors contribute to bend-twist coupling, including the blade's geometric shape, such as its aspect ratio, thickness, and curvature. In this research, three beam models made of metamaterials are considered as the core of helicopter blades, and the geometry of the unit cell of the beams has been investigated to achieve the bend-twist coupling property. Beams consisting of several metamaterial unit cells were made using additive manufacturing technology and subjected to static and dynamic experimental tests. Furthermore, finite element simulations were performed in Abaqus software to validate the experimental results. The results obtained from the static tests indicate that the beam with a unit cell geometry consisting of a simple cube and a diagonal sub-cell exhibits a higher bend-twist coupling property compared to the other geometries investigated, despite its simple structure. Also, increasing the aspect ratio in the geometry of the unit cell has a great effect on improving the bend-twist coupling property. The dynamic analysis of the beams also shows that the beams with more bend-twist coupling properties obtained in static tests have higher natural frequencies and the number of torsion modes in a specific frequency range is more, which is a proof of the bend-twist coupling property in these beams.